De-icing Systems and Controls

Abstract

The present disclosure is generally directed to methods and systems for heating the exterior surface of a bulk medium, such as an aircraft. An exemplary system includes a series of individual heating elements, sensors, and a control system. The heating elements are disposed on the skin of the aircraft. The sensors are disposed on the skin at locations corresponding to relatively cooler regions in a heating pattern produced by the heating elements. The control system is connected to the heating elements and the sensors. The control system is configured to control power supplied to the heating elements in response to an output from the sensors.

Description

[Technical Field]

[0001] The present invention relates to a heating system for electrically conductive materials. [Background technology]

[0002] Many conductive surfaces, such as cars, aircraft, and satellites, encounter cold and icy conditions during daily use. The accumulation of ice and water on the conductive surfaces of these structures can create inefficient or dangerous operating conditions. For example, ice accumulation on an aircraft's wings can reduce lift and increase drag.

[0003] Many of these structures either lack heating systems or have heating systems that require the use of bulky electronics and other equipment. The use of such bulky devices poses challenges for the industry. Summary of the Invention

[0004] The present invention discloses techniques for heating conductive surfaces. These techniques generally use high frequency alternating current ("AC") signals (e.g., 1 kHz or higher) to shape current density in a targeted area of ​​a conductive bulk medium (e.g., a conductive material) to induce Joule heating in the medium.

[0005] Joule heating, also known as ohmic heating or resistive heating, is the process of generating heat by passing an electric current through a conductor. The amount of heat generated by a conductive medium is based on the amount of current passing through the medium and the medium's electrical resistance. As a result, heating can be controlled (e.g., increased or decreased) by adjusting the current, voltage, resistance, or a combination thereof.

[0006] The resistance of a given conductor can be increased by limiting the volume within the conductor through which current can flow and increasing the length over which the current flows. Embodiments of the present invention can be configured to generate heat within a conductive medium (e.g., a bulk medium, a conductor) by manipulating mechanisms that shape (e.g., contract, elongate, etc.) the current within the bulk medium, for example, by utilizing the skin effect and proximity effect. Both effects rely on passing a high-frequency AC current through the conductive medium to be heated. The skin effect inhibits current flow by utilizing the tendency of AC current to distribute within a conductor such that the current density increases near the surface of the conductor and decreases with depth within the conductor. The proximity effect can be used to further inhibit current flow through a conductor by placing an additional AC current path near an existing current flowing through the conductor. The proximity effect can also function to lengthen the current path.

[0007] For example, embodiments of the present invention are configured to increase the resistance of a bulk medium along a current path through the bulk medium by inhibiting current flow along the current path. As a result, the embodiments can provide increased heating capacity for the conductive medium while simultaneously reducing the current required to generate heat. That is, by increasing the effective resistance of the conductive medium along a particular current path, less current than would otherwise be required to generate Joule heat within the medium.

[0008] The subject matter described herein can be implemented to achieve one or more of the following advantages: Lighter, more compact electrical systems can be used to heat the conductors. Furthermore, heating can be localized to the target area without overheating the heating system circuitry. The heating system can be more efficient, for example, by generating heat directly in the bulk medium (e.g., an aircraft wing) itself, rather than generating heat in a heating element or layer attached to the bulk medium. The system also may use less current and voltage for heating, potentially improving safety and reliability. In some embodiments, component stress may also be reduced. The system can be easier, faster, or less expensive to install or retrofit. The system can be less expensive and easier to maintain. The system can be non-invasive when retrofitted to existing systems. The system allows for faster de-icing.

[0009] The details of one or more embodiments of the subject matter herein are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, drawings, and claims. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of an exemplary configuration for heating a bulk medium. [Figure 2] 2A-2B are schematic diagrams illustrating an exemplary configuration for utilizing the skin effect to concentrate current density in a first direction of a bulk conductor to heat a bulk medium. [Figure 3] FIG. 1 is a plot showing the increase in current density concentration due to the skin effect as a function of applied AC current. [Figure 4] 4A-D are schematic diagrams illustrating exemplary configurations for utilizing the proximity effect to concentrate current density in a second direction of the bulk conductor to heat the bulk medium. [Figure 5]5A-B are simulation diagrams illustrating the increase in current density crowding in a bulk conductor adjacent to a second conductor as a function of distance between the conductors due to the proximity effect. [Figure 6] Figure 6A is a schematic diagram of an exemplary configuration for heating a bulk medium using an array of electrodes, and Figures 6B-6D are schematic diagrams of exemplary configurations for heating a bulk medium using various electrode arrangements. [Figure 7] 1 is a schematic diagram of an exemplary signal conversion unit ("STU") including standard power conversion ("TSP") and AC generation ("ACG") main subunits. [Figure 8] FIG. 1 is a schematic diagram of an exemplary STU including a TSP, an ACG, and a control main subunit. [Figure 9] 9A and 9B are schematic diagrams of an example TSP subunit including a flyback converter and a common mode choke. [Figure 10] Figure 10A is a schematic diagram of an exemplary ACG subunit including a class D amplifier with dual MOSFET transistors, a temperature controlled crystal oscillator ("TCXO"), and a gate driver. Figure 10B is a schematic diagram of an exemplary class D switch mode amplifier. Figure 10C is a schematic diagram of an exemplary ACG subunit including a class D amplifier with dual MOSFET transistors, a TCXO, a gate driver, and a low power conversion stage ("LPC"). [Figure 11] FIG. 1 is a schematic diagram of an exemplary control subunit including a microcontroller and an LPC. [Figure 12] FIG. 1 is a diagram of an impedance matching network between a power source and a load. [Figure 13] 13A-D are schematic diagrams of building blocks of an exemplary impedance matching network. [Figure 14] FIG. 2 is a schematic diagram of an exemplary coordination network unit including a passive coordination subunit. [Figure 15]FIG. 15A is a schematic diagram of an exemplary coordination network unit including an active coordination subunit and a control subunit; and FIG. 15B is a schematic diagram of an exemplary coordination network unit including an active coordination subunit, an LPC, and a control subunit. [Figure 16] 1 is a schematic diagram of a cable stage in an exemplary heating system. [Figure 17] FIG. 1 is a schematic diagram of an exemplary electrode for a heating system. [Figure 18] Figure 18A is a schematic diagram of an exemplary brazed joint between an electrode and bulk media, Figure 18B is a schematic diagram of an exemplary rivet fastener attachment between an electrode and bulk media, Figure 18C is a schematic diagram of an exemplary air seal tape attachment between an electrode and bulk media, and Figure 18D is a schematic diagram of an exemplary mated attachment between an electrode and bulk media. [Figure 19] 1 is a cross-sectional view of an exemplary coupling strip for providing a radio frequency heating signal to a bulk medium according to an implementation of the present disclosure. [Figure 20] 20 illustrates an exemplary layout of the joining strip of FIG. 19 positioned on an aircraft wing. [Figure 21] 1A-1C show top views of several example bonding strips to illustrate various configurations of conductive layers within the bonding strips. [Figure 22A] 1 shows plots of simulated current densities generated in an aircraft skin by an exemplary coupling strip and electric field densities between the coupling strip and the aircraft skin. [Figure 22B] 22B shows a plot of simulated current densities generated in the skin of the aircraft shown in FIG. 22A. [Figure 23] Layout diagrams of some exemplary conductive layer arrangements within a coupling strip are shown. [Figure 24A] 24 shows a cross-sectional view of a coupling strip according to layout A of FIG. 23 taken along line AA. [Figure 24B] 24 shows a cross-sectional view of the coupling strip according to layout B of FIG. 23 taken along line BB. [Figure 24C]24 shows a cross-sectional view of the coupling strip according to layout C of FIG. 23 taken along line CC. [Figure 25] Figure 25A shows a cross-sectional view of an exemplary configuration for attaching a coupling strip to a bulk media, and Figure 25B shows a cross-sectional view of another exemplary configuration for attaching a coupling strip to a bulk media. [Figure 26A] 1 is a cross-sectional view of a bonding strip with a double-sided adhesive bottom layer prior to placement on bulk media. [Figure 26B] FIG. 26B is a cross-sectional view of the coupling strip of FIG. 26A placed on a bulk medium. [Figure 27] 27A-27F show cross-sectional views of various embodiments of embedded bonding strips. [Figure 28] 1A-1C illustrate an embodiment of a coupling strip connector. [Figure 29] 10A-10C illustrate another embodiment of a coupling strip connector. [Figure 30] 1 is a block diagram of a first exemplary bulk media heating system utilizing coupling strips according to an implementation of the present disclosure. [Figure 31] FIG. 10 is a block diagram of a second exemplary bulk media heating system utilizing coupling strips according to embodiments of the present disclosure. [Figure 32] FIG. 10 is a block diagram of a third exemplary bulk media heating system utilizing coupling strips according to an implementation of the present disclosure. [Figure 33] FIG. 1 illustrates a portion of an aircraft pilot's field of view with a temperature overlay on a wing. [Figure 34] FIG. 1 illustrates a time domain reflectometry (TDR) technique. [Figure 35] Figure 35A is a plot comparing two transmission lines measured with TDR, one of which includes a 2-meter connector, and Figure 35B is a plot showing a frequency domain analysis showing the impedance change associated with an impact-induced indentation. [Figure 36] Plot showing a comparison of two transmission lines measured with TDR, one of which has a dimple in its test panel. [Figure 37] 37A, 37B, and 37C illustrate exemplary cockpit announcement displays. [Figure 38] 1 shows a plot of coupling strip impedance and temperature as a function of time during de-icing operation. [Figure 39] 1 is a 3D plot of the dielectric constant of an exemplary acrylic adhesive material over a range of operating temperatures. [Figure 40] 1 is a plot of the dielectric constant of an exemplary acrylic adhesive material over a range of operating temperatures. [Figure 41] 1 shows plots of the frequency response of an unimpaired line and an impaired line. Like reference numbers and names in the various figures indicate like elements. DETAILED DESCRIPTION OF THE INVENTION

[0011] The heating system of the present invention uses AC current to increase the effective electrical resistance of conductive materials (e.g., aluminum, carbon fiber composites) to heat them more easily. Generally, the heat generated in the conductive material can be used to melt ice that forms on the surface of the conductive material. This heat can be used to keep the conductive material hot and prevent vapor deposition on the surface or to prevent water from freezing on the surface, as well as to prevent freezing precipitation (e.g., snow, sleet, fog, freezing rain) from forming on the surface. For example, the heat generated in the conductive material can be conducted (e.g., spread) throughout the conductive material. Furthermore, the generated heat can induce convection across the interface between the conductive material and a liquid on its surface, for example, to heat the liquid and prevent it from freezing.

[0012] Alternating current can be used to induce several electromagnetic effects that increase the effective resistance of conductive materials, thereby promoting Joule heating in the material. These effects include the skin effect, proximity effect, induction, eddy currents, hysteresis loss, and dielectric loss. When the frequency of the current in a conductor is set to a sufficiently high value, the skin effect causes most of the current to pass through the skin of the conductive material, which is significantly thinner than the geometric thickness of the conductive material. Furthermore, certain device geometries can be used to induce a proximity effect within the conductive material, which further suppresses the width of the current density and thereby further increases the effective resistance along the current path within the conductive material. These two effects can be used together to increase the electrical resistance of the conductive material and generate Joule heating.

[0013] For example, Joule heating generally refers to the heat generated by passing an electric current through a conductor. The heat generated in a particular current-carrying conductor is the root-mean-square product of the material's resistance and the square of the amplitude of the current:

number

[0014] Heat output from a heating element is generally increased by increasing the current passing through a conductor and by using a heating element with a relatively high resistance. However, embodiments of the present disclosure utilize certain electromagnetic phenomena (e.g., the skin effect and the proximity effect) to generate Joule heating by constricting the current density of local currents within a bulk medium. This current density constriction increases the effective resistance along the current path within the bulk medium. While the specific effects may vary depending on the material and geometry, the effective resistance for a particular length along the current path through a bulk medium can generally be expressed as:

number

[0015] Some embodiments of the present disclosure can use these electromagnetic phenomena to increase the length of the current path through a bulk medium. For example, as described below with reference to FIG. 4D, the techniques described herein can be used to "steer" the current path between two electrodes attached to the bulk medium along a non-orthogonal path (e.g., a serpentine path). A non-orthogonal path has an effective length (l) that is longer than the generally substantially straight path that would be produced by a current passing between the two electrodes in the absence of electromagnetic effects, such as the proximity effect. eff ) can be generated. Thus, the systems described herein can generate a current path length l that is an effective length (l) that is longer than the direct path that the current would take in the absence of the various systems and conductor arrangements described herein. eff ) can be increased to . Therefore, such an embodiment reduces the effective cross-sectional area (A eff ) and the effective length (l eff ) by both increasing the effective resistance (R eff ), which can increase the effective resistance of the bulk medium beyond its effective resistance to DC current. In such an embodiment, the effective resistance can generally be expressed as:

number

[0016] As used herein, skin effect generally refers to the tendency of alternating current to be unevenly distributed within a conductor, with current density being greater near the conductor's surface and decreasing as the distance to the conductor's surface increases. The strength of the skin effect increases with the frequency of the current and the conductivity of the material carrying the current. Some embodiments of the present disclosure can tailor the skin effect so that current flows more at the outer surface (e.g., "skin depth") of the conductor at higher AC frequencies.

[0017] In general, the skin effect of a conductor can be expressed by the following formula:

number

number

[0018] For an infinitely long and wide rectangular plate carrying a surface current, the skin effect can be expressed as:

number

[0019] For example, the diagram shown in FIG. 3, and described in detail below, illustrates an example of current density constriction within a depth of a material (eg, skin depth) caused by the skin effect.

[0020] As used herein, the proximity effect generally refers to the effect of AC current flowing through a first current path (e.g., a conductor) on the current density of AC current flowing through a nearby second current path. For example, as shown in Figures 5A-5B and described in detail below, the AC current in a first current path causes the AC current density in a second current path to "concentrate" or constrict around the first current path. In embodiments of the present disclosure, for example, the density of a current passing through a bulk medium is "pulled" toward another conductor carrying AC current when that conductor is placed near the current passing through the bulk medium. The degree and direction of the current density constriction (e.g., concentration) caused by the proximity effect depends on several variables, such as the distance between two or more AC current paths, the relative directions of travel of the currents through the individual current paths, the frequency of the AC currents in the current paths, and the magnitude of the individual currents in the current paths.

[0021] For clarity, the heating system of the present disclosure will be described in the exemplary context of a de-icing and anti-icing system for the exterior surfaces of an airplane. However, the heating system of the present disclosure can be used in other contexts, such as, but not limited to, heating other aircraft, unmanned aerial vehicles, wind turbines, cryogenically operated equipment, heat pumps, automobiles, radio towers, railroad track surfaces, manned or unmanned military vehicles, roofs, or other electrically conductive surfaces that benefit from the suppression of ice or water formation. The heating system can be used for de-icing or anti-icing. In some embodiments, the heating system can be used to heat low-conductivity materials, for example, by adding a conductive layer over or within the non-conductive material. Such embodiments can be used to heat roads (such as driveways), building materials, roofs, floors, or other low- or non-conductive material surfaces.

[0022] As used herein, deicing generally refers to the removal of snow, ice, or frost (collectively "ice") from a surface. In some embodiments, a heating system may melt a portion of existing ice on a conductive surface. The ice is then removed from the surface (e.g., by sliding off the surface as the melting process begins and the bond between the ice and the surface is broken).

[0023] Anti-icing, as used herein, generally refers to preventing snow, ice, or frost (collectively "ice") from forming or adhering to a surface. In some embodiments, the heating system prevents ice from forming on a surface (e.g., from freezing precipitation such as snow, frost, freezing rain, and the like) and maintains a surface temperature high enough to prevent ice buildup or formation.

[0024] 1 shows a block diagram of an exemplary heating system 100 for heating a bulk medium. The heating system 100 includes a power control system 104 coupled to electrodes 116 and 118. The electrodes 116 and 118 are coupled to a target area of ​​the bulk medium 102 (e.g., a portion of an aircraft wing). The power control system 104 generates an alternating current (AC current) (e.g., a frequency of 1 kHz or greater) across a closed-open circuit via a wire (or path or cable) 106, the bulk medium 102, and finally a wire (or return path) 108. The direction of the current 112 flowing through the wire is indicated by the dashed arrow.

[0025] In some embodiments, the heating system 100 can include, but is not limited to, a power control system 104, electrodes 116 and 118, and a specialized cable (e.g., wires 108 and 106). In some embodiments, the heating system is configured to be coupled to electrodes 116 and 118. In some embodiments, the heating system is configured to be coupled to a specialized cable (e.g., 108 or 116). In some embodiments, the power control system 104 can include, but is not limited to, a signal generation unit, a power source, a signal transformation unit, an impedance tuning network, a control unit, and a sensor, having specific configurations described in detail below. As described in detail below, in some embodiments, the impedance tuning network is an impedance matching network.

[0026] In some embodiments, the electrodes 116 and 118 are contact electrodes. For example, the electrodes 116 and 118 are physically connected to the bulk medium 102 to conduct current from the power control system 104 to the bulk medium. In some embodiments, the electrodes 116 and 118 can be coupled to the bulk medium 102 but can also be electrically isolated from the bulk medium 102. For example, in such embodiments, the electrodes 116 and 118 can magnetically induce current in the bulk medium 102 as inputs and outputs of an induction coil positioned proximate to the bulk medium 102.

[0027] The power control system 104 can provide a current at a high frequency (e.g., 1 kHz or higher) sufficient to constrict current flow in the z-direction between the electrodes 116 and 118 by adjusting the skin effect, thereby creating a high resistance in the bulk medium 102. The power control system 104 can provide AC current at a frequency between 1 kHz and 300 GHz. In some embodiments, the current frequency is between 100 kHz and 450 MHz. In some embodiments, the current frequency is in the range of 1 MHz to 50 MHz, 100 MHz to 150 MHz, 200 MHz to 300 MHz, 400 MHz to 500 MHz, or 800 MHz to 1 GHz.

[0028] In some embodiments, the return path 108 is positioned proximate to the surface of the bulk medium 102. The proximity of the return path 108 to the surface of the bulk medium can be used to adjust the proximity effect of the current flowing between the electrodes 116 and 118, thereby further suppressing the current and increasing heating within the bulk medium. It is not necessary to use the return current path 108 from the heating system circuit itself to utilize the proximity effect to shape the current flowing between the electrodes 116 and 118. In some embodiments, another current path 122 (e.g., from a different circuit) can be positioned proximate (e.g., distance 120a) to the bulk medium 102. For example, if the distance 120 or 120a of the current path 108 or 122 from the bulk medium 102 is sufficiently small, the proximity effect can be used to further suppress the current through the bulk medium.

[0029] For example, the distance 120 (or 120a) between the bulk medium and the path 108 (or 122) can be less than 1 meter, or less than 50 cm, or less than 10 cm to create a proximity effect. If a closer distance is possible given due consideration of design constraints (e.g., if the bulk medium is an airplane wing, and the airplane's ribs or spars do not obstruct the return path 108 / 122), the distance 120 (or 120a) can be less than 25 cm or less than 10 cm.

[0030] The bulk media 102 may include, but is not limited to, materials such as aluminum, metal alloys, carbon fiber composites, copper, silver, titanium, or steel. For example, the bulk media may be any portion of an aircraft's airframe (e.g., the outermost shell or surface of the aircraft, also known as the airplane's "skin"), such as the fuselage, wings, undercarriage, tail, etc.

[0031] The electrodes (116 and 118) may include, but are not limited to, aluminum, silver, copper, alloys thereof, or other conductive materials. In some embodiments, the electrode material is at least as conductive as the bulk medium 102. In some embodiments, the electrodes 116 and 118 may be arranged in an array of electrodes. The electrodes may be coupled to the bulk medium in various ways, for example, to the top or bottom surface of the medium, or embedded within the medium.

[0032] The heating system 100 is configured to create an effective resistance through the bulk medium 102 by shaping the density of the current flowing through the medium. In other words, in an aircraft application, the existing fuselage of the aircraft is used as part of the heating system's electrical circuit. The heating system 100 shapes the density of the current by manipulating the skin effect, the proximity effect, or a combination thereof, to increase the effective resistance of the bulk medium 102 along the current path between the electrodes 116 and 118. In some cases, the proximity effect can be utilized to direct the current path to heat a desired section of the bulk medium, as seen, for example, in FIG. 4D . The desired heating section of the bulk medium may be referred to as a “target heating location” or “target location.”

[0033] In some embodiments, an alternating current with a frequency of 1 kHz or greater can be passed directly through the aircraft fuselage, resulting in Joule heating in the portions of the fuselage near the surface through which the current flows. The heat generated by the current then spreads throughout the bulk medium 102 by conduction.

[0034] 2A-2B, the heating system 100 utilizes the skin effect to shape the current density through the target region 102 of the medium. Similar to FIG. 1, an AC current (direction 212) is supplied between electrodes 116 and 118 through the target region of the bulk medium 102. FIG. 2A is a schematic diagram showing the profile (e.g., side view) of the current density 202 through the target region of the bulk medium 102 in the absence of the skin effect (e.g., for a current frequency less than 1 kHz). The current flows in the y-direction (212), with the majority of the current flowing within the volume of the medium 102 indicated by the arrows. For example, the current has a depth 206 of approximately 2 mm, e.g., nearly the entire thickness of the bulk medium. Thus, FIG. 2A illustrates the operation of the system 100 with little or no current density shaping due to the skin effect.

[0035] FIG. 2B is a schematic diagram of a current density 202 profile resulting from applying a high-frequency AC current (e.g., 1 kHz or greater) between electrodes. FIG. 2B illustrates the operation of the system 100 to shape the current density due to the skin effect. For example, the skin effect, caused by operating the heating system 100 at a high frequency, causes the depth of the current density 202 flowing through the bulk medium 102 to shrink in the z-direction to a narrow region near the surface of the bulk medium 102. Furthermore, the effective resistance of the current flow region in the bulk medium 102 increases sufficiently to allow Joule heating in this region without overheating the rest of the circuit (e.g., wires, power supply, inverter, conditioning network, electrodes). The effective resistance of the bulk medium to AC current in the target region can be greater than the resistance of the bulk medium to DC current. For example, the effective resistance can be two or more orders of magnitude greater than the resistance of the bulk medium to DC current.

[0036] Figure 3 is a plot showing the concentration of current density (y-axis, normalized to 1) with depth in a material (x-axis, normalized to 1) due to the skin effect as a function of applied AC current. The current density decays exponentially along the thickness of the medium (z-direction). As the frequency increases from 1 kHz to 10 MHz, the current density becomes more concentrated near the surface of the bulk medium. Thus, the higher the frequency, the more pronounced the decay. In other words, the skin effect constricts the current density as it passes through a thin layer near the surface of the bulk medium. As a result, Joule heating occurs in this layer.

[0037] 4A is a side view of a system 400 for further constricting current density using the proximity effect. Similar to FIG. 1 , electrodes 116 and 118 are attached to bulk medium 102 (e.g., a target area on an airframe) and pass an AC signal (e.g., 1 kHz or higher) to generate a current density (or path) 410 in a direction 412 through the medium. Return path 108 is disposed within a distance 120 from current path (or density) 410 in the medium and has a direction 112 different from direction 412. In some embodiments, return path 108 is electrically isolated from bulk medium 102. Path 108 may be a wire or cable disposed within distance 120 from bulk medium 102. Return path 108 may be a wire or cable that completes the circuit of system 400.

[0038] When the return path 108 is sufficiently close to the current path 410 (e.g., less than 50 cm), the AC current in the return path 108 constricts the current in the current path 410 in a direction transverse to the current flow in the current path 410. In other words, by placing the return path 108 sufficiently close to the current path 410, the cross-sectional area of ​​the current flow in the current path 410 is constricted. For example, with reference to FIGS. 4A-4C , the current is constricted in two directions (e.g., the x-direction and the z-direction as shown) between the electrodes 116 and 118. For example, as shown in FIG. 4D , the proximity effect constricts the current density 410 in either the x-direction or the y-direction, depending on the direction of current flow. For example, if the current flows in the x-direction, the proximity effect constricts the current in the y-direction. For example, the proximity effect primarily constricts the current transverse to the direction of current flow, while the skin effect primarily constricts the current density within the depth of the bulk medium (e.g., in the z-direction as shown in FIGS. 2A and 2B ). In some cases, the proximity effect can also add to the contraction of current density with depth (e.g., in the z-direction) of the bulk medium 102, e.g., enhance the skin effect in embodiments that utilize both the skin effect and the proximity effect. In some embodiments, the proximity effect can also be used to define the direction of current flow through the bulk medium (e.g., the path that the current takes through the bulk medium 102).

[0039] 4B-C are exemplary schematic diagrams of a system 400 from a top view. Electrodes 116 and 118 are attached to a target region 102 of the bulk medium and pass an AC signal (e.g., 1 kHz or higher) to generate a current density (or current path) 410 in a direction 412 through the medium. The return path 108 is positioned in a different x-y plane (dashed line) than the current path (or density) 410 in the bulk medium 102. In some embodiments, the current in the return path 108 is in a direction 112 different from direction 412. For example, in some embodiments, the direction 112 of current in the return path 108 is opposite the direction 412 of current in the current path 410. If the spacing between the current path 412 and the return path 108 is sufficiently small (e.g., less than 50 cm), the current flowing in the bulk medium 102 between the electrodes 116 and 118 will be clustered (e.g., constricted in the y and z directions) near the return path wire due to the proximity effect, as shown in FIG. 4C. The greater the separation distance of the return path 108 from the bulk medium 102, the less current path 412 will be constricted within the bulk medium 102, as shown in FIG. 4B.

[0040] FIG. 4D is an exemplary schematic diagram of another embodiment of a system 450, viewed from above. As with the previous system 100, electrodes 116 and 118 are attached to a target region of the bulk medium 102. A return path 108 is positioned proximate to the bulk medium 102 in a different x-y plane than a current path 410 within the bulk medium 102. The illustrated embodiment shows how the return path 108 (or another separate current path) can be used to shape the path along which the current 410 flows through the bulk medium 102. For example, by placing a second current path (e.g., a current-carrying wire or cable like the return path 108) proximate to the bulk medium 102, the proximity effect can be used to both constrict the width of the current density transverse to the direction of current flow and to shape the current path 410 within the bulk medium 102. FIG. 4D also shows that the proximity effect constricts the current density along the current path 410 transverse to the direction of current flow. 4D , the current density along current path 410 is constricted in a direction substantially perpendicular to the direction of current flow in each segment of path 410, and current path 410 in bulk medium 102 conforms to the shape of return path 108. More specifically, in section A of current path 410, the current is guided to flow along the x-direction, and the current density is constricted in the y- and z-directions. In section B of current path 410, the current is guided to flow along the y-direction, and the current density is constricted in the x- and z-directions.

[0041] As shown in Figure 4D, the ability to shape the current path into more complex shapes through the proximity effect offers several advantages. First, such path shapes can be used to increase the effective current path length l. As noted above, longer path lengths result in greater resistance and greater Joule heating. Second, such current path shapes can be configured to direct current to strategic locations for heating. Third, such current path shapes can be used to create regions of increased heating (e.g., hot spots) at sharp corners in the current path.

[0042] The combination of the proximity effect and the skin effect can make the effective resistance of the bulk medium to AC current in the target region greater than the resistance of the bulk medium to DC current. For example, the effective resistance can be two or more orders of magnitude greater than the resistance of the bulk medium to DC current.

[0043] 5A-B are simulation diagrams illustrating the increasing concentration of current density in a bulk conductor target area 102 near a second conductor / path 108 due to the proximity effect as a function of the distance 120 between the conductors. The current in the bulk conductor and the second path is sufficient to cause the proximity effect as the distance 120 decreases (e.g., at frequencies above 1 kHz or 10 MHz). For example, when the distance 120 is 20 cm, the current density 410 remains nearly uniform in the xy plane, as shown in FIG. 5A. As shown in FIG. 5B, when the distance 120 is reduced to 2 cm, the proximity effect causes the current 410 to "crowd" or "constrict" around the return path 108 in the xz plane. This is achieved by the majority of the current 410 concentrating in a narrow strip along the bulk conductor and following the path of the second conductor (108) (e.g., the return path or other current-carrying wire). In other words, the current 410 follows the path of least inductance rather than spreading evenly throughout the bulk medium.

[0044] In some embodiments, a wire other than return path 108 is used to induce the proximity effect, similar to path 122 in FIG. 1. In that case, the current oscillation in that wire may or may not be driven by the same system (e.g., power control system 104) as paths 106 and 108. In that case, the proximity effect of wire 122 depends on the distance from current path 412 in the bulk conductor to wire 112. Similar to return path 108, wire 122 needs to be sufficiently close to path 412 (e.g., less than 50 cm).

[0045] Generally, the power control system 104 supplies current to the bulk medium 102 via electrodes (e.g., 116 and 118) and dedicated conductors (e.g., dedicated wires or cables) to form a closed circuit (see FIG. 1). These three components are described in more detail below.

[0046] In some embodiments, the electrodes 116 and 118 comprise arrays of input and output electrodes, as shown in Figure 6A. The electrode system 600 includes three input electrodes 116(1)-(3) forming the electrode array 116 and three output electrodes 118(1)-(3) forming the electrode array 118, resulting in adjacent current paths 410 within the bulk medium. As detailed above, the proximity effect due to the current 112 in the return wire 108 constricts the current density 410 in the bulk medium.

[0047] In general, various electrode geometries can be used to achieve desired heating in the target region of the bulk media 102. For example, referring to FIG. 6B, a system 610 shows two electrode arrangements 116 and 118 (with input / output wires 106 and 108) used to supply current to the target region of the bulk media 102. The electrode arrangements 116 and 118 may be arrays of one or more electrodes as shown in FIG. 6A. FIGS. 6C-D are schematic diagrams of other electrode configurations 620 and 630, respectively, for heating a target region 120, for example, on an aircraft wing. The electrode arrangements represented by 116, 118, and 640 may be single electrodes as shown in FIG. 6A, or arrays of one or more electrodes. Details of the electrode geometries and designs are provided below.

[0048] In some embodiments, the bulk medium is the skin of an airplane and the target area for heating is , wings, fuselage, vertical stabilizer, horizontal stabilizer, windows, winglets, windshield, control surfaces (flaps, ailerons, rudders, elevators, air brakes, etc.), nose / nose cone, landing gear, landing gear brakes, landing gear doors, engines and engine nacelles, AC inlets and outlets, fuel tank vents, pitot heads, static ports, other antennas, sensors, exterior lights, fuel tank vents, service panels, etc. In other words, the proposed technology may involve placing electrodes inside the airframe, possibly in one or more of the configurations shown in Figures 6A-6D. In some embodiments, the heating system 100 can generate Joule heat in a portion of the target area, followed by further heat diffusion via conduction within the material.

[0049] Generally, the power control system 104 includes a signal generation system designed to generate a high frequency (e.g., 1 kHz or greater) alternating current (AC) electrical signal and send it through the aforementioned target region 102 in the bulk medium. In some embodiments where the impedance of the target region is low (possibly much lower than 1 Ω), the signal generation system is configured to generate and maintain a desired current level to generate Joule heating in the target region. In some cases, other parts of the system (such as conductors or wires carrying signals) have impedances greater than zero, causing high currents flowing through these parts to generate unwanted Joule heating outside the target region. Therefore, in some embodiments, the signal generation system is designed to deliver high current only near the target region.

[0050] In some embodiments, some or all of the elements / units of the signal generating system, as well as the conductive elements / cables connecting them, are designed to reduce as much as possible the unwanted power losses that typically occur when transmitting high current and high frequency electromagnetic signals.

[0051] In some embodiments, the signal generation system can receive power from an existing power source (e.g., an existing electric bus on an aircraft). In some embodiments, the system uses a dedicated battery or a dedicated power source that is part of the system. For example, such a dedicated power source may include, but is not limited to, a fuel-based generator, a solar-power-based generator, a wind-power-based generator, a gas-power-based generator, etc. The signal generation system can be placed in circuit between the power source (e.g., an existing electric bus, a dedicated battery, a dedicated power source) and the target area.

[0052] Additionally, in some embodiments, the signal generation system may include control circuits and devices that exist as stand-alone units and / or are embedded within a combination of other units that are part of the signal generation system.

[0053] In some embodiments, the heating system 100 is used to heat several separate target areas. In such cases, each element or unit of the heating system (e.g., signal conversion unit, impedance matching network, etc.) can be centralized throughout the system or distributed as one or more individual units for each target area or group of target areas. The centralized or distributed configuration can be used to improve system functionality, energy efficiency, cost, regulatory compliance, weight, size, and complexity, among other criteria. For example, in some embodiments, the signal conversion unit is centralized, but the impedance matching network is distributed to one or more units for each target area. In some embodiments, the signal conversion unit is only partially centralized as a centralized TSP (“conversion to standard power”) subunit, but the ACG (“AC generation”) subunit is distributed as one or more subunits for each target area or group of target areas. In some embodiments, the signal conversion unit is fully distributed, with each of its subunits distributed to one or more subunits for each target area or group of target areas.

[0054] In some embodiments, the power control system 104 continuously sends power to the target area 102 until the heating / de-icing / anti-icing operation is complete. In some embodiments, the system can turn power on and off in an improved / efficient manner (e.g., using a control unit) to achieve a desired heat generation and distribution in the conductive material 102. For example, when the system is on, heat is generated in a specific location in the target area, conducted throughout the target area, and "spread" to the rest of the target area. While the system is off, the generated heat continues to conduct within the target area.

[0055] In some embodiments, the system can have a different power level for the on state and cycle between the different power levels in an improved manner with the off state. In some embodiments, a particular power level can be reached by smoothly increasing or decreasing the power rather than by a single step increment or decrement of power. The pattern of such a pulsed power system can be completely predefined when the system is built, or can be varied and dynamically improved based on a feedback loop that forms part of the system's control unit.

[0056] In some embodiments where the heating system includes multiple target areas, the above-described pulsed power pattern can be used asynchronously across all target areas, allowing all target areas to be heated for the required amount of time while maintaining both the overall average and overall instantaneous power levels below set thresholds. For example, in the case of an aircraft de-icing system that heats both wings, the fuselage, and the horizontal and vertical stabilizers, such a stepped power pattern can be designed so that the system is turned on for only one target area at a time. In some embodiments, the stepped power pattern powers on the system in the following order: left wing, fuselage, right wing, vertical stabilizer, and horizontal stabilizer.

[0057] In some embodiments, improved timing can be used at each stage to achieve desired heat, average power, and instantaneous power levels, as well as acceptable heat distribution. In some embodiments, similar to the patterns described above, any subset of the target area can be heated at a particular time.

[0058] In some embodiments, one or more units or elements referenced as part of the heating system design have an enclosure. Such an enclosure may be designed for a single unit or for any combination of units. In some embodiments, the enclosure is designed to comply with environmental certification standards. For example, the enclosure may be designed to comply with standards such as non-combustibility, protection from precipitation, mounting and construction that provides protection from external shock and vibration, electrical insulation, protection from external electromagnetic interference ("EMI"), shielding of enclosed circuitry from EMI radiation, and thermal relief.

[0059] In some embodiments, some enclosures can be designed to use the structure of the heated object (e.g., a bulk conductive material) as a heat sink. For example, one or more heating system units can be housed in a metal or conductive structure mounted to have high thermal conductivity with respect to the bulk medium in which it is placed. One possible advantage of this mounting is that it heats the bulk medium while simultaneously providing the necessary cooling for the electronics. Another possible advantage of this design is that it reduces the weight of the heating system (or device) by eliminating the need for a separate heat sink to distribute losses. In some embodiments, the target area can be used as part of the heat sink for the heating system unit. This use can improve the efficiency of the heating system, as the heating system circuitry inevitably generates heat losses that can be conducted to the target area and heat it.

[0060] In some embodiments, multiple adhesives or attachment types can be used to attach the enclosure to the bulk media. For example, an adhesive used primarily for mechanical rigidity can be used to hold the casing in place, and another adhesive (or interface agent) can be used to provide a low thermal impedance path for the enclosure's heat sink function.

[0061] In some embodiments, one or more heating system units can be configured to detect one or more measurements, such as, but not limited to, voltage, current, temperature, forward power, and reflected power, measured on the unit's circuitry, surrounding cables, other units, or target areas. In some embodiments, such measurements can be used to monitor the operational status of the units and to control (using feedback mechanisms) their operation for improvement, such as on / off switching, output levels, and in-circuit control of switching and adjustable units (see below for more details on controlling switching and adjustable units in dynamic regulating networks). Controlled parameters include power to and / or current to the load, voltage control of the regulating network, and other related signals.

[0062] In some embodiments, measurements used as part of the above feedback loop may also include specific ice sensors that may be placed at or near the target area. Such sensors may be used, for example, to notify the heating system and / or user of de-icing completion status and may be used as inputs to adjust power levels during de-icing and anti-icing operation. In some embodiments, ice sensors may also be used to determine faults or service requests within the system.

[0063] In some embodiments, the heating system may include a protocol converter control unit (or "control unit" or "control subunit") that receives input from a user (which in the case of an aircraft de-icing system may be the pilot or co-pilot) and / or sensors in the system and outputs control signals to all other units. In some embodiments, input from the user may include, but is not limited to, on / off status, de-icing / anti-icing / off status, target temperature for the target area, and target power for the target area. In some embodiments, input from sensors may include, but is not limited to, voltage, current, temperature, forward and reflected power, impedance, and ice sensors, squat switches, data from various aircraft logic units, information from avionics, and other information. In some embodiments, the protocol converter unit is centrally located throughout the system. In some embodiments, one protocol converter control unit is decentralized for each target area or group of target areas.

[0064] In some embodiments, user input can be transmitted to the control unit using wires (e.g., a data transfer standard such as ARINC 429) or wirelessly (e.g., a low-energy Bluetooth or Wi-Fi connection). In some embodiments, the user input device can be integrated into the heated system (e.g., integrated into the cockpit on-screen controls of the aircraft de-icing system) or can be a separate device such as a touchscreen tablet (e.g., a separate tablet mounted in the cockpit or, in the case of an aircraft de-icing system, a dedicated application installed on the pilot's touchscreen tablet).

[0065] In some embodiments, the power control system 104 includes a signal conversion unit (“STU”) or circuitry that converts a signal from an existing electric bus or a dedicated battery or any other power source of the heating system into a desired high-frequency AC waveform to generate a current in the bulk medium. For example, in an aircraft application, the signal conversion unit may receive available DC power from the airplane's electric bus and convert it into the desired high-frequency AC signal. In another aircraft example, the signal conversion unit may receive available power from the aircraft's electric bus in the form of an AC signal and convert it into the desired high-frequency AC signal. In some embodiments, the signal conversion unit may take available DC power from a dedicated battery or any dedicated power source (e.g., forming part of the heating system) and convert it into the desired high-frequency AC signal. In some embodiments, the dedicated battery or power source may be contained within the same enclosure and / or circuit board as the signal conversion unit.

[0066] 7 is a schematic diagram of an exemplary signal transformation unit ("STU") 700 for power control system 104, including the main subunits of conversion to standard power ("TSP") 710 and AC generation ("ACG") 720, which precede other circuitry 730 in the rest of device 100. Power control system 104 can draw power from an existing power source, as shown in FIG.

[0067] FIG. 8 is a schematic diagram of an exemplary signal transformation unit (“STU”) 800 for the power control system 104, including a TSP 810, an ACG 820, and a control subunit 830.

[0068] In some embodiments, the TSP draws power from an existing power source or battery of the heating system and converts that power to a standard input such as 250VDC for improved operation of the ACG as well as improved power transfer efficiency of the signal conversion unit.

[0069] In some embodiments, if an existing electrical bus supplies power to the TSP in the form of a 400 Hz, 115 VAC signal, the TSP can include a flyback converter with a filter, such as a common mode choke, on the output side to prevent electromagnetic interference from reaching or damaging the ACG. Figure 9A is a schematic diagram of an example TSP subunit 900, including a flyback converter 910 and a common mode choke 920. Figure 9B is a schematic diagram of an example flyback converter 910.

[0070] In some embodiments, the TSP is a bridge rectifier that converts AC power from an existing power source to a desired DC voltage. In some embodiments, the TSP draws DC power from a battery or an existing power source (e.g., the common 28 VDC on an aircraft) and converts it to a different DC or AC voltage. For example, DC-DC conversion is useful for powering the control units and elements of a heating system, where possible voltage levels include ±3.3 V, ±5 V, and / or ±12 V. Finally, in some embodiments, a power factor correction ("PFC") stage can be included in the TSP design, depending on the power source. In some embodiments, PFC can help correct nonlinear loads on the power source, which may be required. Both active and passive PFC stages can be used.

[0071] In some embodiments, the ACG uses input power from the TSP and converts it into a desired high-frequency AC signal. In some embodiments, the ACG is designed to improve the power transfer efficiency of the signal conversion unit. In some embodiments, the ACG includes a power amplifier or an AC or RF generator or oscillator.

[0072] In some embodiments, the main power amplification stage of a power amplifier is either "linear" or "switching." Relevant tradeoffs between these two architectures may include efficiency, power handling, and linearity. Examples of linear amplifiers include Class-A, Class-B, and Class-C. Examples of switching amplifiers include Class-D, Class-C, and Class-D. Examples of linear amplifiers include Class-E, Class-F, and Class-E-class amplifiers. In some embodiments, linear amplifiers have higher linearity and lower efficiency compared to switching amplifiers. Lower efficiency can lead to challenges such as difficult thermal management and the need for higher spec components. Lower linearity can lead to higher harmonic content, which can lead to challenges such as regulatory compliance, reduced efficiency, and physical and electrical layout design difficulties.

[0073] In some embodiments, the ACG includes a full-bridge class-D amplifier. For example, the amplifier design uses dual MOSFET transistors powered by a gate driver and a temperature-compensated crystal oscillator ("TCXO") to generate the desired frequency. FIG. 10A is a schematic diagram of an example ACG subunit 1000 including a class-D amplifier 1010 with dual MOSFET transistors, a temperature-controlled crystal oscillator ("TCXO") 1020, and a gate driver 1030. FIG. 10B is a theoretical schematic diagram of an example class-D amplifier using dual MOSFETs. In some embodiments, a full-bridge architecture can provide differential (balanced) drive capability and provide four times the power output for a given bus voltage level under a given load compared to a half-bridge architecture. Differential drive may also be suitable for emissions compliance under balanced load conditions provided by an anti-wing structure. Furthermore, in some embodiments, a class-D architecture may have a higher switch utilization rate than other switching architectures.

[0074] In some embodiments, many input parameters can be varied within a Class-D architecture to improve output parameters under a single frequency drive. Examples of input parameters include dead time. Examples of output parameters include efficiency, peak component stress, etc.

[0075] In some embodiments, the Class D architecture has high switch utilization and allows for silicon-based component implementation, making it suitable for potential ASIC development. Such development allows for a system-on-chip (SoC) implementation with all control components and power electronics on either the same die or a multi-chip package (MCP). In some embodiments, the Class D architecture has distributed modules housing the SoC and support circuitry installed in various distributed locations in predetermined functional areas of the aircraft.

[0076] In other embodiments, other switch mode designs such as single-switch architectures, e.g., Class E or Class F, are utilized. In some embodiments, such architectures allow for higher switching frequency implementations where a high-side gate driver may be difficult or impractical. In some embodiments, due to the potential limitations of Class-D implementations at higher frequencies, a single-switch architecture may be used instead of a Class-D implementation as frequencies increase.

[0077] In some embodiments, harmonic reduction and elimination techniques can be used with switch-mode amplifiers to mitigate the adverse effects of nonlinear distortion inherent in some switching architectures. For example, varying the duty cycle of the base waveform, blanking pulses, and other techniques can be used to eliminate harmonics during signal generation.

[0078] In some embodiments, the ACG includes a transistor such as a silicon MOSFET. In some embodiments, the transistor is a gallium nitride (GaN) MOSFET. In particular embodiments, GaN transistors have advantageous properties such as low on-resistance, low turn-on gate charge, and low reverse recovery charge. In some embodiments, GaN is suitable for higher frequencies.

[0079] In some embodiments, the TSP further includes a low power conversion ("LPC") stage, such as a linear regulator, to draw power from an existing power source and convert it into a power input signal suitable for elements such as gate drivers or crystal oscillators that drive the ACG. Figure 10C is a schematic diagram of an exemplary ACG subunit 1050, including a class D amplifier 1010 with dual MOSFET transistors, a temperature controlled crystal oscillator ("TCXO") 1020, a gate driver 1030, and an LPC 1050.

[0080] In some embodiments, the AC generating subunit is located near the target area. A potential advantage of this design is that it limits losses and emissions that occur when passing AC current from the AC generating subunit through the conditioning network to the target area. In some embodiments, the TSP subunit can be located near the AC generating unit or near an existing power source or dedicated battery. The proximity of the TSP to the ACG allows it to be integrated with the ACG, potentially reducing the number of modules in the system and their complexity. If the TSP is located near an existing power source or dedicated battery, it can be designed to improve power transfer from the power source or battery to the ACG (increasing efficiency and reducing EMI). For example, if the existing power source provides power in the form of a 400 Hz, 115 VAC voltage, the TSP can include an AC-DC converter to convert the source voltage to 250 VDC, reducing EMI caused by AC current and increasing efficiency by increasing the voltage and reducing the current flowing from the TSP to the ACG.

[0081] In some embodiments, the control subunit controls the status of the signal conversion unit (e.g., on / off mode, power output, frequency, and other parameters) based on relevant data inputs available for the application for which the device (heating system) is being developed, and outputs control signals to other signal conversion subunits, such as the TSP and ACG drivers. In the example of an aircraft de-icing and anti-icing heating system, in some embodiments, data inputs include manual pilot input from cockpit switches, temperatures from internal and external temperature sensors, wheels-on-weight status from squat switches, information from various aircraft logic units, avionics, feedback information from the device (heating system) itself, and other data. In some embodiments, the control subunit includes a microcontroller supervisor powered by a low-power conversion (LPC) stage, such as a linear regulator, that draws power from an existing power source, converts it to an appropriate power input signal, and outputs control signals to the TSP and ACG. Figure 11 is a schematic diagram of an example control subunit 1100, including a microcontroller 1110 and a low-power conversion stage (LPC) 1120.

[0082] In some embodiments, for example, in the case of a de-icing heating system retrofitted to an aircraft, the signal conversion units can be installed in a central location near available electric buses, reducing installation complexity, labor hours, and unit costs. In some embodiments, the signal conversion units are decentralized and installed near the target area, reducing the length that AC signals must travel between the signal conversion units and the target area, reducing costs associated with electromagnetic interference ("EMI") shielding of the signals and cabling requirements for transmitting such AC signals.

[0083] In some embodiments, the heating system includes an impedance matching network ("IAN") configured to adjust the output impedance of the heating system to a desired level. For example, the IAN can be configured to adjust the output impedance of the heating system to correspond to the input impedance of the bulk medium being heated. For example, the IAN can be configured to adjust the impedance between the output of the heating system and the input of the bulk medium to within a desired range of each other. In some embodiments, the impedance matching network is configured to adjust the output impedance of the heating system to adequately match the impedance of the bulk medium. In other words, the matching network is configured to match the output impedance of the STU ("source") to the impedance of the target area ("load") within reasonable engineering tolerances. In some embodiments, matching the source impedance and the load impedance includes adjusting the source impedance of the heating system to be the complex conjugate of the impedance of the bulk medium. In some embodiments, the impedance matching network adjusts the output impedance of the heating system to be within 10 to 30% of the impedance of the bulk medium being heated.

[0084] Figure 12 is a conceptual diagram of an impedance matching network 1200 between a source 1210 and a load 1220. Figure 12 shows a matching network that receives input power from an STU ("source") through an input port that is impedance matched to the output of the STU, and outputs power to a target area ("load") through an output port that is impedance matched to correspond to the target area.

[0085] Generally, for AC signals, if the output impedance of the source does not match the impedance of the load, some of the signal sent from the source to the load will be reflected back to the source rather than passing through the load. In some embodiments, an impedance matching network provides several benefits by suppressing signal reflections and the buildup of voltage standing waves, e.g., Reduced terminal voltage and risk of arcing in heating systems Improved efficiency of heating systems Reduction in the total output power required from the STU, thereby reducing the size, weight, and cost of the STU Reduced stress on system components Improved reliability Reduced temperature gradients in cables and bulk media etc. can be achieved.

[0086] In some embodiments, the output impedance of the STU is higher than the impedance of the target area. The conditioning network then converts the relatively high voltage, low current power from the STU to a relatively low voltage, high current power delivered to the target area. In these embodiments, this means that high current is delivered only after the conditioning network, and therefore near the target area, reducing joule losses in the rest of the SGU and improving the overall efficiency of the heating system.

[0087] In various embodiments, this conditioning network may be centralized or distributed throughout the target area. Distributing this conditioning network allows the cables to act as filters, potentially reducing the effects of peak voltages, peak currents, and / or temperatures on specific components. Distributed locations can also add modularity to the system design, improving component maintainability / replacement. Additionally, distributed locations allow the system to be located away from sensitive equipment, fuel tanks, and other hazardous areas.

[0088] A distributed impedance tuning network, such as an impedance matching network placed at the input of the combining strip 1900, can facilitate distributed monitoring of each combining strip locally, even in embodiments where the power control system 104 supplies power to multiple combining strips. It can also provide a means for various localized functions, including the ability to switch the combining strip 1900 on or off and the ability to communicate information to the power control system 104. Communication can be easily accomplished via a separate communication cable or via power cable encoding (e.g., a power cable connected to the combining strip 1900) to reduce weight and cable clutter.

[0089] For example, the conditioning network can trigger a special impedance state that is detectable by the power control system 104 based on the use of intentional impedance changes, such as encoding a signal sent back over the power lines with either digital communication-style coding or analog or threshold level coding techniques. As another example, the distributed impedance conditioning network can add an additional data signal to the power cable (in addition to the heating power signal). Alternatively or additionally, one or more of the units or elements mentioned as part of the heating system can relay information via wireless means.

[0090] In some embodiments, the impedance conditioning network further supports fault indication. In these embodiments, the heating system may include a local fault sensor that is triggered or tripped by a fault or failure that may be present in the heating system, as described in more detail in the "Control and Sensing" section below. For example, the local fault sensor may be located on the bonding strip 1900. This conditioning network may include a controller that maintains a look-up table that specifies different types of faults in specific portions and sections of the heating system and different impedance values ​​that correspond to the types of faults. This conditioning network may then be configured to adjust the input impedance observed by the power control system to a specific value to indicate a specific type of fault or failure that may be present.

[0091] Additionally, in some embodiments, the tuning network can be balanced by including additional capacitive components and grounding the symmetrical midpoint in the network. When driven by a fully differential source, this network operates in a balanced manner, allowing for high common-mode rejection and excellent noise immunity. In some embodiments, such balancing is not achieved, and the return path of the tuning network terminates at circuit ground.

[0092] In general, in some embodiments, a tuning network can include passive electronic components arranged in specific building block configurations. For example, these building block configurations can include transformers, L-networks, π-networks, T-networks, and other configurations. Figures 13A-D are schematic diagrams of building blocks of exemplary impedance tuning networks.

[0093] In some embodiments, the conditioning network of the heating system includes a passive conditioning subunit. Figure 14 is a schematic diagram of an exemplary conditioning network unit 1400 including a passive conditioning subunit 1410. In some embodiments, the passive conditioning subunit can include one or more of the building block configurations described above, as well as other configurations. In some embodiments, the passive electronic components of the passive conditioning subunit are selected to have a high quality factor, for example, to improve the efficiency of the network.

[0094] In some embodiments, the tuning network of a heating system can be designed to have a high-quality factor (high-Q) or a low-quality factor (low-Q). A high-Q tuning network can be used to remove harmonic signal components. Because harmonic components can be higher than in linear amplifiers, filtering can be advantageous in switching amplifier designs. However, high-Q networks can be more sensitive to component tolerances, operational variations in external conditions, assembly variations, and other variations in the system. Therefore, high-Q systems can cause practical problems during system implementation. For example, in the case of an aircraft wing de-icing system, if the system is high-Q, the impedance tuning network may be thrown off balance by small perturbations (such as flap movement), creating a risk of failure. Reducing harmonic components beyond the fundamental drive frequency can be beneficial for both regulatory certification and practical design concerns, such as the inclusion of stray signals in the design, excessive stress on components (within peak or time-average ratings), and control algorithm instability. In some cases, the use of dynamic tuning elements can mitigate or even eliminate these sensitivity concerns.

[0095] In some embodiments, the design of the conditioning network for a heating system can be based on the concept of power line conditioning. For example, the cabling at the input and / or output of the conditioning network can be considered part of the conditioning network. In some embodiments, proper impedance tuning can be achieved by selecting appropriate cable materials, form factors, dimensions, and lengths.

[0096] In some embodiments, the conditioning network of the heating system is a dynamic conditioning network including an active conditioning subunit and a control subunit. FIG. 15A is a schematic diagram of an exemplary conditioning network unit 1500 including an active conditioning subunit 1510 and a control subunit 1520. In some embodiments, the active conditioning subunit includes one or more conditioning network configurations controlled by the control subunit. In some embodiments, the passive electronic components of the active conditioning network subunit are selected to have a high quality factor, for example, to improve the efficiency of the network. In some embodiments, the control subunit receives input data (e.g., forward power, reflected power, voltage standing wave ratio) from signals transmitted to and received from the target area and dynamically controls the active conditioning network subunit to adjust the impedance tuning in real time. For example, such control can be achieved via tuning elements included in the design of the active conditioning network subunit. For example, the dynamic tuning elements may include a tunable capacitor and / or a tunable inductor. Further, examples of tunable elements include PIN diodes, BST capacitors, DTCs (discrete tuned capacitors), varactor diodes, MEMS, ferroelectric varactors, ferromagnetic components, YIG tuned filters, etc. Examples of evaluation criteria that can be considered while evaluating such devices include operating frequency range, DC voltage tuning, control signal linearity tuning, control complexity, capacitance / inductance tuning ratio, tuning speed, quality factor (Q), switching lifetime, packaging cost, power handling, power consumption, breakdown voltage, linearity, third-order intercept (IP3), integration capabilities, etc.

[0097] In some embodiments, a control unit with feedback between the target area and the conditioning network allows the network to adapt to external changes that may affect the impedance of the target area or the STU output impedance, such as changes in the temperature or geometry of the target area, the location of the heating system, the environment surrounding the system and target area, and other parameters. In some embodiments, the conditioning network further includes a low power conversion ("LPC") stage, such as a linear regulator, that draws power from an existing power source and converts it into a power input signal suitable for the control subunit. FIG. 15B is a schematic diagram of an example conditioning network unit 1550, including an active conditioning subunit 1510, a low power conversion stage ("LPC") 1560, and a control subunit 1520.

[0098] In some embodiments, special impedance measurements can be performed on target areas for all configurations and environmental conditions covering the spectrum of situations likely during use of the heating system. These measurements can enable the design of a dynamic tuning network unit adapted to the narrowest impedance range that allows for proper impedance tuning across the full spectrum of situations. In some embodiments, such design can be performed using algorithmic optimization or computer simulation to reduce the weight, complexity, and cost of the tuning network while improving system efficiency.

[0099] In some embodiments, dedicated cables can be used in the heating system, and the cables can be specially designed or selected for each stage to improve efficiency and shield the power signals carried to the target area. Figure 16 is a schematic diagram of cable stages in an exemplary heating system. In various embodiments, the cable stages of the heating system can be customized and can include, for example, a cable (cable stage 1) 1630 between the power source 1620 and the STU 1610, a cable (cable stage 2) 1660 within the STU between the TSP 1640 and the ACG 1650 subunits, a cable (cable stage 3) 1680 between the STU 1610 and the conditioning network 1670, and a cable (cable stage 4) 1695 between the conditioning network 1670 and the target area 1690.

[0100] In general, various design considerations may be involved in the design of dedicated cables for an overall heating system. In some embodiments, thermal considerations may be involved. For example, in some embodiments, the cables connecting the conditioning network to the target area (or passing near the target area and possibly back to the conditioning network) may be fastened to increase the flow of heat from the cable to the target area. This is advantageous if some of the heat generated as current flows through the cable can be recovered (or otherwise lost) and transferred to the target area intended to generate heat, increasing the efficiency of the system.

[0101] In some embodiments, a clamp may be used to route the cable close to the target area, in which case a thermally conductive material with good thermal conductivity may be used to fill the air gap between the cable-clamp-target area interface to improve thermal contact.

[0102] In some embodiments, the cable is attached directly to the target area. In such cases, to improve thermal contact, a highly thermally conductive adhesive can be used to attach the cable to the contact area. Additionally, a highly thermally conductive thermal interface material can be used to fill some or all of the remaining air gap between the cable and the target area.

[0103] In some embodiments, different shaped cross sections and different cable form factors can be used depending on the unit, target area, or power source to which the cable connects. In some embodiments, the cable includes only a main conductor, with or without a protective jacket (for electrical insulation and / or environmental protection against corrosion, humidity, extreme temperatures, friction, etc.). This configuration can be advantageous for portions of the system that carry DC signals or transmit signals to a target area.

[0104] In some embodiments, the cable is a coaxial cable, which may include shielding to reduce EMI emissions when carrying AC signals and to protect the system from ambient EMI when carrying any signal.

[0105] In some embodiments, the cable is a triaxial cable, a design which can be beneficial for EMI protection and isolation when carrying any signal, more particularly when carrying a balanced signal, for example at the output of a balanced embodiment of the conditioning network unit.

[0106] In some embodiments, the cable is a biaxial cable, a design that can offer advantages similar to those offered by triaxial cables.

[0107] In some embodiments, different cable cross-sectional shapes can be used depending on the unit, target area, or power source to which the cable connects.

[0108] In some embodiments, the cross section of the cable conductor has a circular shape. This design has the advantage of relatively low manufacturing costs (low non-recurring engineering costs) for coaxial / triaxial / twinaxial form factors.

[0109] In some embodiments, the cable has a flattened and / or rectangular cross section. For example, this cross section may be an advantageous cable shape for the final stage of a system, where the cable delivers current to a target area. In this final stage, a rectangular shape can reduce the effects of proximity and skin effects on the current circulating within the cable, thereby reducing losses and improving system efficiency. Furthermore, this shape can reduce the total amount of conductive material required in the cable, reducing the weight of the system, which is an important consideration for aircraft de-icing systems.

[0110] In some embodiments, depending on the particular input and output currents and signals carried by the cable, and depending on its cross-sectional shape and other factors, the cross-sectional size can be selected to limit the operating temperature to a specified range (e.g., for compliance and as determined by the materials used to manufacture the cable) and to reduce its weight and size.

[0111] In some embodiments, different cable shield types (and cross-sectional shapes) are used depending on the unit, target area, or power source to which the cable connects.

[0112] In some embodiments, the cable does not include a shield, which can be advantageous in stages where DC current is carried (and therefore EMI suppression requirements are low) and in stages where no return current needs to be carried (e.g., later in the system in embodiments where the target area carries the return current and a nearby cable supplies that current to the target area).

[0113] In some embodiments, a single shield is used. This is advantageous when one shielding layer is sufficient to make the device compliant with EMI / EMC and other environmental requirements.

[0114] In some embodiments, double shielding is used, which adds another layer of shielding to, for example, further reduce EMI radiation and can also reduce the EMI susceptibility of the cable.

[0115] In some embodiments, three or more layers of shielding are used, adding additional shielding layers for similar reasons as above.

[0116] In some embodiments, for a particular target area, the cable supplying the current to this area may follow different possible paths.

[0117] In some embodiments, the cables simply follow a generally straight path from one side of the target area to the other. In some cases, these paths may be parallel. In some embodiments, the cables may pass diagonally through the target area and cross each other at various locations within the target area. This can be useful, for example, to generate more uniform heat across the surface of the target area and to create relatively hot spots at desired locations where the cables cross.

[0118] In some embodiments, the cable follows a zigzag-type path, a serpentine path, or a path that can be modeled with a 2D spline curve. This design can increase the effectiveness of the system by lengthening the path taken by the current through the target area, thus further increasing the effective resistance. This can help achieve, for example, higher efficiency, lower current, and more stable impedance regulation by the system.

[0119] In some embodiments, the cable routing design is based on a combination of the above and other options.

[0120] In some embodiments, different materials may be used to manufacture the cable depending on the design, stage, and purpose of the cable.

[0121] Depending on the local voltage, current, temperature, power, bend radius, durability requirements, and other criteria, the cable conductor material can be selected to improve efficiency, conductivity, weight, cost, size, and thermal aspects.

[0122] In some embodiments, the conductor material is made of copper, silver, aluminum, carbon fiber composite, titanium, or alloys thereof. In some embodiments, the conductor is made of any of the aforementioned materials and coated with another material, such as a silver coating, to improve the conductivity of the conductor's skin.

[0123] In some embodiments, the conductors may be solid material or may be stranded. For example, in some embodiments, the strands may be insulated from each other by using an insulating coating such as enamel. For example, Litz wire may be used to reduce the effects of skin and proximity effects in the cable.

[0124] In some embodiments (e.g., for coaxial / triaxial / twinaxial cables), depending on local voltage, current, temperature, power, bend radius, durability requirements, and other criteria, the cable's dielectric material can be selected to improve efficiency (e.g., by reducing dielectric losses), weight, cost, flexibility, maximum voltage tolerance, maximum power tolerance, temperature rating (by providing the cable with high temperature tolerance and / or high heat capacity and / or low dielectric losses and / or good thermal conductivity).

[0125] In some embodiments, when transmission line conditioning is used within the conditioning network unit, the associated cable may also use a dielectric material selected to achieve the desired impedance level. Exemplary materials include polyethylene and Teflon-based materials, as well as others.

[0126] In some embodiments, depending on local voltage, current, temperature, power, bend radius, durability requirements, and other criteria, the cable jacket material is selected to improve parameters such as weight, cost, flexibility, maximum voltage tolerance, temperature rating, and heat conduction to a nearby heat sink (e.g., a targeted area to be used as a heat sink).

[0127] In some embodiments, when a transmission line conditioning is used as part of a conditioning network, the length of the cable used for impedance conditioning can be controlled in addition to its dielectric to reach the target impedance level. For example, a cable supplying current to a target area can be used as part of a transmission line conditioning system, with extra length added for impedance conditioning and locally coiled to occupy less space.

[0128] In some embodiments, the cables can be routed along the structure of the system using specific fastening techniques, which can be selected to improve installation cost and time, system weight (by reducing the length of wire required and the weight of fasteners), and the desired electromagnetic effect and heat transfer of the cables in proximity to the target area.

[0129] In some embodiments, the fasteners are selected to reduce the distance between the target area and the cable supplying power to the target area. This design may create a stronger proximity effect. In some embodiments, a conventional cable fastener design can be selected to reduce the cable-to-target area distance.

[0130] In some embodiments, the fasteners are also used to enhance heat transfer from the cable to the target area.

[0131] In some embodiments, the fastener material is selected to reduce the weight and cost of the system. This can be achieved, for example, by using composite materials. In some embodiments where the fastener is also used to conduct heat to the target area, a material with high thermal conductivity (e.g., a metallic material that typically has a relatively high thermal conductivity) is selected.

[0132] In some embodiments, the adhesive used to secure the fasteners to their bond areas is selected to enhance bond strength to the target area and ensure a long-term bond. Adhesive strength is advantageous when the bond area is relatively small and creates relatively strong mechanical constraints at the bond area. Additionally, in some embodiments where the fasteners are used for heat transfer from the cable to the target area, the adhesive is also selected for increased thermal conductivity.

[0133] Finally, in some embodiments where the fastener is used for heat transfer from the cable to the target area, the void in the area between the cable, fastener, and target area is filled with a sufficiently thermally conductive thermal interface material to improve the flow of heat from the cable to the target area.

[0134] In some embodiments, the cable is attached directly to the surrounding structure, such as a bulk medium, with an adhesive to allow for better heat transfer from the cable to the structure to which it is attached. The adhesive is selected based on criteria similar to those used for fasteners.

[0135] In some embodiments, the cable assembly design involves splitting a given cable path into two or more separate sets of branches. This is useful, for example, in embodiments where a single conditioning network delivers current to multiple sets of target areas. In such embodiments, a single cable may be the only output of the conditioning network, and the cable may be split into separate branches that feed each of the target areas, such that the cable reaches multiple target areas. In some embodiments, this splitting can be achieved by splitting a given conductor strand into several smaller strands, or if the split cable has stranded conductors, by sending a subset of the strands to each of the separate branches, or by using a power splitter. A power splitter is useful for controlling the amount of current, voltage, and power flowing in each of the branches into which the cable is split.

[0136] Similarly, in some embodiments, two or more cables can be merged into a smaller number of cables and the signals from all the merged cables can be pooled. Such merging can be achieved by fusing certain conductor strands with other strands, regrouping different subsets of strands into a new stranded cable, or by using a power combiner (e.g., the same device as a power divider, but used in the opposite direction). A power combiner helps to control the amount of current, voltage, and power flowing in each branch where cables are combined.

[0137] In some embodiments, each cable stage of the heating system has its own cable design considerations.

[0138] In some embodiments, cable stage 1 is selected to allow efficient power transfer from the power source to the TSP subunits. In some embodiments where the power source outputs DC current, cable stage 1 comprises stranded copper wire insulated with a compatible material and has a total equivalent gauge suitable for the power, voltage, and current supplied to the TSP subunits. In some embodiments where the power source outputs a 400 Hz, 115 VAC signal, cable stage 1 comprises stranded copper wire insulated with a compatible material and has a total equivalent gauge suitable for the power, voltage, and current supplied to the TSP subunits.

[0139] In some embodiments, cable stage 2 is selected to allow efficient power transfer from the TSP to the ACG subunits. In some embodiments where the TSP outputs power in the form of a 250 VDC signal, cable stage 2 comprises stranded copper wire insulated with a compatible material and having a total equivalent gauge appropriate for the power, voltage, and current supplied to the TSP subunits.

[0140] In some embodiments, cable stage 3 is selected and customized to enable efficient power transmission of the high-frequency AC power signal from the output of the STU to the regulating network. For example, the cable can be designed to reduce resistance and electromagnetic losses caused by the signal's high frequency, shield against external interference that could alter the signal integrity, and prevent signal leakage from the cable that could affect surrounding equipment and materials. In some embodiments, cable stage 3 is a high-power, high-frequency transmission line in the form of a customized coaxial cable. In some embodiments, the coaxial cable is made from a core conductor carrying the input signal of the conditioning network, the core conductor being made of stranded copper wire with an outer diameter sufficient to carry power with low resistive losses; a dielectric surrounding the core selected to provide increased electrical insulation and to maintain high voltage and temperature ranges; a shield conductor providing a return path for the signal to the ACG made of twisted and braided copper with an equivalent gauge large enough to carry power with low resistive losses; a first casing insulating the conductive shield, selected to maintain high voltage and temperature ranges; an outer shield similar to the conductive shield but which does not directly carry current and is used to protect the cable from external interference and prevent leakage; and finally, a second casing similar to the first casing insulating the outer shield.

[0141] In some embodiments, cable stage 4 is selected and customized to enable efficient transmission of high-frequency, high-current AC power signals from the conditioning network to the target area. In some embodiments, the cable is designed to adjust the impedance between the conditioning network and the target area, reduce resistive and electromagnetic losses caused by the signal's high frequency, shield against external interference that could alter the signal's integrity, and prevent signal leakage from the cable that could affect surrounding equipment or materials. In some embodiments, cable stage 4 is a high-power, high-frequency, and high-current transmission line in the form of a customized coaxial cable, similar to the cable stage 3 embodiment described above, except that it uses a larger conductor gauge and diameter and an additional silver coating of the same conductor to improve high-current performance and further reduce resistive losses. In some embodiments, cable stage 4 is further customized based on a Litz wire design. The purpose of such a design is to reduce losses due to proximity and skin effects in the cable by fabricating conductors with a thickness thinner than the skin from individually insulated (e.g., with an enamel coating) and perfectly symmetrically twisted or braided braid.

[0142] Generally, electrodes comprise a material that conducts current and directs current into and out of the target region of the bulk medium. In some embodiments, connectors are used to connect the electrodes to the bulk medium. A connector refers to a fixture that connects the electrodes to the bulk medium. In some embodiments, the electrodes and connectors are designed to reduce the contact resistance between the electrodes and the bulk medium. In other words, the electrodes are designed to smooth out the potential difference that develops across the target region for a given return path. If this contact resistance is higher than the resistance of the target region between the two electrodes, more heat will be generated at the contact point than along the target region, all else being equal, reducing the heating efficiency of the heating system. In some embodiments, for similar reasons, the electrodes and connectors are designed to reduce the contact resistance between the electrodes and the wires (or cables) of the heating system. In some embodiments, the electrodes and connectors are also designed to reduce electromagnetic losses (e.g., electromagnetic radiation).

[0143] In some embodiments, electrode design considerations to achieve one or more of the above goals include (1) selecting an electrode material with high electrical conductivity and (2) increasing the "real" contact area between the electrode and the bulk medium and between the electrode and the wire. "Real" contact area refers to the minute metal-to-metal or material-to-material contact where current flows from one material to another, often referred to as the "a-spot." In some embodiments, connectors are also designed to achieve these goals.

[0144] In some embodiments, the electrode material can include silver, copper, aluminum, carbon fiber composite, titanium, or alloys thereof.

[0145] In some embodiments, the electrodes are part of a cable used to transmit electrical current to the bulk medium.

[0146] In some embodiments, the shape of the electrodes is designed to fit a particular target area and / or to reduce contact resistance between the electrodes and the bulk medium and / or to reduce electromagnetic losses.

[0147] In some embodiments, the electrodes are circular.

[0148] In some embodiments, the electrodes are in the form of the ends of cables used to transmit electrical current to the bulk medium.

[0149] In some embodiments, line electrodes (eg, rectangular electrodes whose length is greater than their width) are used.

[0150] In some embodiments, electrodes in the shape of 2D spline curves with a small thickness (third spatial dimension) are used.

[0151] In some embodiments, the cable conductors can be connected to the target area by sandwiching them between the connector plate and the target area. For example, a portion of the side of the connector plate that contacts the target area can be milled. The cable conductors can be connected to the target area by placing them in this milled portion. This configuration allows the electrode connector plate to be clamped or glued under the cable conductors, eliminating the need to bend the connection to ensure proper coupling with the target area.

[0152] Generally, various implementations and design considerations of electrodes and connectors are discussed.

[0153] 17 is a photograph of an exemplary circular stud electrode 1700 for heating system 100. The electrode includes a circular ground stud coupled to a disk 1710 made of a conductive material (e.g., aluminum), on which a threaded conductive portion 1720 (e.g., aluminum) is attached.

[0154] In some embodiments, the conductor of the cable connected to the target area via electrode 1700 is wrapped around threaded conductive portion 1720 and laid flat, covering a significant portion of the surface area of ​​both the threaded conductive portion and the disk. In some embodiments, a nut and washer can be used on threaded conductive portion 1720 to compress the conductor against disk 1710, ensuring a higher contact area and lower contact resistance.

[0155] In some embodiments, the air gap between the washer, cable, and disk 1710 is filled with an electrically and / or thermally conductive thermal interface material to ensure improved thermal and / or electrical conductivity from the cable to the stud 1700.

[0156] In some embodiments, the circular stud electrode 1700 is attached to the target area by a specially selected adhesive that is sufficiently electrically and thermally conductive to conduct heat and electrical signals from the cable to the target area, and in some embodiments, the adhesive is also strong enough to withstand the torque exerted by the nut and washer.

[0157] In some embodiments, the connector is a U-shaped fixture attached to the bulk media and the electrode such that substantial compressive strength is provided between the electrode and the bulk media.

[0158] In some embodiments, the materials of the electrodes and connectors can be selected to reduce their weight. In some embodiments, the electrode material is selected to improve electrical and / or thermal conductivity through the material in addition to reducing its weight. Improved conductivity can be advantageous for electrode designs (e.g., round stud, one-plate designs) in which current flowing from the cable to the target area passes through the electrode.

[0159] In some embodiments, specific enclosures are included as part of the connector and electrode design. For example, such enclosures can be selected for environmental conditions, including criteria such as thermal mitigation and / or insulation, electrical insulation, EMI shielding, corrosion protection, vibration and impact resistance, durability, protection from external contamination and sediment, etc.

[0160] In general, various adhesive configurations (and combinations thereof) between the electrodes and / or connectors and the bulk medium are contemplated, which in some embodiments reduce contact resistance between the electrodes and the bulk medium and / or reduce electromagnetic losses.

[0161] In some embodiments, the electrode is connected to the bulk media using a braze joint. FIG. 18A is a schematic diagram of an exemplary braze joint attachment 1800 between an electrode 1802 and a bulk media target area 102 that is part of a larger bulk media 1806. A braze material is used to create the braze joint 1804. For example, a low-temperature braze filler metal (e.g., AL802) can be used to braze the electrode to the target area to create a low-resistance contact. In some embodiments, the filler metal is coated with a flux to mitigate oxidation (the formation of an aluminum oxide layer at the braze site). The flux is a material that dissolves oxides at high temperatures and prevents the surface from re-oxidizing until the filler metal wets the surface.

[0162] In some embodiments, the electrode and target area are covered together under pressure and heat. For example, in some embodiments, a compressive force is applied between the electrode and the target area. Without wishing to be bound by theory, the compressive force may reduce the contact resistance between the electrode and the bulk medium according to the following formula:

number

[0163] In some embodiments, a mechanical fastening connector can be used to apply a compressive force to connect the electrode and bulk media. Figure 18B is a schematic diagram of an exemplary attachment configuration 1820 between an electrode 1802 and a target area 102 that is part of a larger bulk media 1806. A solid rivet 1822 is used to apply a compressive force to connect the electrode to the target area.

[0164] In some embodiments, vacuum tape or the like can be used to pressure seal the connection between the electrode and the target area. Figure 18C is a schematic diagram of an exemplary attachment configuration 1840 between an electrode 1802 and a target area 102 that is part of a larger bulk medium 1806. Air seal tape 1842 is used to connect the electrode and the target area. After the air seal is complete, a suction device can be used to create a vacuum between the electrode and the target area, thereby crimping the two together.

[0165] In some embodiments, the compressive force can be applied using a clamp, such as a C-clamp, that clamps the electrode and the target area, increasing the pressure at their interface.

[0166] In some embodiments, the compressive force can be applied using a magnet or a magnetized surface. In some embodiments, either the face of the electrode or the face of the target area is magnetized, allowing for an attractive force between the magnet and the electrode and / or contact area, resulting in the desired compressive force. In some embodiments, two or more magnets are used, with the electrode and target area sandwiched between them, allowing for an attractive force between the magnets, resulting in the desired compressive force. In some embodiments, both the face of the electrode and the face of the target area are magnetized, allowing for an attractive force between the electrode and the target area, resulting in the desired compressive force.

[0167] In some embodiments, the compressive force is applied by an external or internal compression fixation connector that adheres to a surface on or near the target area, converting the adhesive strength into the desired compressive force. In some embodiments, an adhesive (e.g., a curable adhesive) can be used in combination with the fixation connector.

[0168] In some embodiments, the electrodes can be partially or wholly embedded in the bulk medium using one of the methods described above or alternative techniques.

[0169] In some embodiments, a conductive material (eg, graphene) is disposed between the electrode and the target area.

[0170] In some embodiments, the connector material used to connect the electrode to the target area is an adhesive selected for its strength, ensuring long-term bonding to the target area. The strength of the adhesive can be advantageous when the bond area is relatively small and the mechanical constraints imposed on the bond area are relatively strong (e.g., in the case of U-shaped stud electrodes). In one embodiment, when the electrode needs to be held in a fixed position after adhesive application for adhesive curing, an internal or external / disposable fixator using adhesive and mechanical force can be used to hold the electrode in place.

[0171] In some embodiments, the connector material used to connect the electrode to the target area is also selected for higher thermal and / or electrical conductivity to improve the flow of current and heat from the cable to the target area. For example, higher conductivity may be a consideration when the electrode used is attached so that the adhesive is located in the path of the current flowing from the cable / electrode to the target area (e.g., when the electrode used is a circular stud electrode or a one-plate design electrode). To this end, in some embodiments, nanomaterials (e.g., CNTs) are disposed between the electrode and the bulk medium. In some embodiments, the surface of the electrode and the portion of the surface of the bulk medium that contacts the electrode (e.g., the target area) can be treated to increase the "actual" contact area between them.

[0172] In some embodiments, in combination with the above and other embodiments, the connector, electrodes, and portions of the target area are covered with a material that reduces or eliminates electromagnetic losses.

[0173] In some embodiments, any combination of the above methods is used with any of the electrode and connector embodiments. For example, Figure 18D is a schematic diagram of an exemplary combination attachment 1860 between an electrode 1802 and a target area 102 of a bulk media 1806. The attachment includes a brazed joint 1804 and a solid rivet 1822.

[0174] In some embodiments, a connector / cable may not be required for the system because no physical contact is required to generate the desired current, in which case, in some embodiments, the return path for the signal may be an additional section of wire going back to the conditioning network.

[0175] Embodiments of the heating systems described herein can be used as de-icing / anti-icing devices to melt ice from the surface of an aircraft by applying high frequency AC current (e.g., generating Joule heating) to a targeted area on the aircraft skin / airframe. The heat generated in the targeted area on the airframe is conducted to the airframe surface and convected across the airframe-ice interface into the ice. In some embodiments, the ice melts completely. In some embodiments, a portion of the ice (the layer in direct contact with the vehicle) melts, forming a layer of water between the ice and the vehicle, allowing the ice to slide off or be mechanically removed from the vehicle. In some embodiments, heating occurs before ice is present, preventing ice formation.

[0176] In some embodiments, as the ice melts, high frequency AC current continues to be applied, maintaining Joule heat generation within the vehicle, which is transferred by conduction and convection to the water that has formed / remains on the surface.

[0177] 19-32 provide examples of assemblies that convey and deliver electromagnetic energy for bulk media heating systems. These assemblies (referred to herein as "coupling strips") are configured to function similarly to transmission lines in conjunction with the bulk conductive media to which they are attached. For example, in some embodiments, the coupling strips are designed so that the bulk media itself conducts current similar to that flowing through a transmission line. The coupling strips can electromagnetically couple AC signals from the line into the bulk media, thereby generating a corresponding current signal within the bulk media. Thus, in effect, the coupling strip design can be said to cause the bulk media (in combination with the coupling strip) to also operate as a transmission line, or the bulk media and coupling strip together form a system that operates like a transmission line, and can be analyzed and designed as such.

[0178] For example, as described above, embodiments of the present disclosure can be configured to generate heat in a conductive medium (e.g., bulk medium, conductor) by manipulating mechanisms for shaping (e.g., contracting, expanding, etc.) current flow within the medium using, for example, the skin effect and the proximity effect. Both effects rely on passing a high-frequency AC current through the conductive medium to be heated. The skin effect inhibits current flow by taking advantage of the tendency of alternating current ("AC") to distribute within a conductor such that current density is greatest near the surface of the conductor and decreases with increasing depth. The proximity effect can be used to further inhibit current flow in a conductor by placing an additional AC current path near an existing current flowing through the conductor. The proximity effect can also act to lengthen the current path. Coupling strips can be used to generate and control such effects in addition to the systems and processes described above. For example, coupling strips can be used in the various power control systems described above.

[0179] 19 is a cross-sectional view of an exemplary coupling strip 1900. The coupling strip 1900 can be used to supply a high frequency current signal to a bulk medium, such as an aircraft skin 1902, to heat the bulk medium. The coupling strip 1900 has a multi-layer structure including a first dielectric layer 1908 on the bulk medium 1902, a conductive layer 1904 on the first dielectric layer 1908, a second dielectric layer 1908 on the conductive layer 1904, and a conductive shielding layer 1906 on the second dielectric layer 1908.

[0180] The first dielectric layer 1908 has a thickness D1. The conductive layer 1904 has a thickness D2. The second dielectric layer 1908 has a thickness D3. The conductive shielding layer 1906 has a thickness D4. The overall thickness of the bonding strip 1900 is D5. The conductive layer 1904 can be made from a conductive material including, but not limited to, copper, a copper alloy (e.g., brass or bronze), silver, a silver alloy, aluminum, an aluminum alloy, titanium, a titanium alloy, chromium, nickel, a nickel alloy, a cobalt alloy, a corrosion-resistant steel, graphite, or a combination thereof. The conductive shielding layer 1906 can be made from a conductive material including, but not limited to, copper, a copper alloy (e.g., brass or bronze), silver, a silver alloy, aluminum, an aluminum alloy, titanium, a titanium alloy, chromium, nickel, a nickel alloy, a cobalt-based alloy, a corrosion-resistant steel, graphite, or a combination thereof. In some embodiments, the conductive shielding layer 1906 may be formed as a metal foil (e.g., copper foil or aluminum foil) or a braided metal layer. The dielectric layer 1908 may be made from a dielectric material, including, but not limited to, Kapton, Mylar, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), rubber, or a combination thereof.

[0181] In some embodiments, the bonding strip 1900 includes a protective layer over the conductive shielding layer. For example, the protective layer can include, but is not limited to, one or more layers of polyurethane, polyfluoride, paint, paint replacement film, sealant, or combinations thereof.

[0182] As shown in FIG. 20 , coupling strips 1900 may be disposed on a surface of a bulk medium, such as an aircraft skin 2000 (e.g., a wing), to supply electrical current to the bulk medium and create and shape current flow within the bulk to heat the bulk medium. The coupling strips 1900 extend along the surface of the aircraft skin 2000 and are spaced apart from one another. In some embodiments, one or more coupling strips 1900 include a shorting termination that conductively couples at least a portion of the coupling strip (e.g., conductive layer 1904) to the bulk medium 1902. For example, the coupling strip 1900 may terminate at an electrode, as described above, to form a closed circuit (e.g., a short circuit) between the included conductive layer 1904 and the bulk medium 1902. The termination of the coupling strip 1900 is at the distal end of the strip opposite the end to which electrical current is supplied (e.g., opposite the power input end). In some embodiments, one or more coupling strips 1900 terminate at an open circuit. Open termination means that the termination of the coupling strip 1900 remains open and is not connected to electrical ground through either the bulk medium 1902 or the conductive shielding layer of the coupling strip 1900. In some embodiments, one or more coupling strips 1900 terminate with an impedance-adjusting component (e.g., a circuit element) connected between the coupling strip 1900 and the bulk medium 1902. For example, the coupling strip 1900 can be terminated with a capacitive, resistive, or inductive termination. For example, a circuit element such as a capacitor, inductor, or resistor can be connected between the conductive layer 1904 of the coupling strip 1900 and the bulk medium 1902.

[0183] 19 and 20, a power control system (e.g., power control system 104 described above) is coupled to one end of each coupling strip to supply current to each coupling strip. For example, power lines from the power control system can be coupled to the conductive layer of each carrier strip 1900 and can couple one or both of the bulk media 1902 (e.g., aircraft skin 2000) to electrical ground.

[0184] The power control system supplies AC current to each carrier strip 1900. For example, the power control system may provide AC current at a frequency between 1 kHz and 450 MHz. In some embodiments, the frequency is between 1 MHz and 450 MHz. In some embodiments, the frequency is between 1 kHz and 1 MHz. The power control system may be configured to supply 0.1 amps to 200 amps of AC current to each coupling strip 1900. For example, the power control system's power supply and the electrical arrangement of the coupling strips 1900 may be configured to supply a desired amount of current (e.g., between 0.1 amps and 200 amps) to each coupling strip 1900. As one common example, if the coupling strips 1900 are coupled to the power control system in series with each other, a 100 amp power supply may be used to supply 100 amps of current to each coupling strip 1900. If ten coupling strips 1900 are coupled to the power control system in parallel with each other, a 100 amp power supply may be used to supply 10 amps of current to each coupling strip 1900. Note that in this example, the impedance of each coupling strip is the same. As described below, the impedance of the coupling strips 1900 can be adjusted in various ways to control the current distribution between the coupling strips as desired or required for a particular heating application.

[0185] An AC current for heating the aircraft skin 1902 is provided through the conductive layer 1904. The AC current provided through the conductive layer 1904 generates a corresponding current (e.g., by electromagnetic capacitive and inductive coupling) within the aircraft skin 1902, as shown in FIGS. 22A-22B. FIGS. 22A-22B show output plots of an electromagnetic finite element analysis (FEA) simulating the operation of an exemplary coupling strip 1900 attached to a conductive bulk medium 1902. The bulk medium 1902 (e.g., simulated as the skin of the aircraft), the conductive layer 1904, and the conductive shielding layer 1906 are shown in the plot shown in FIG. 22A. In FIG. 22B, the individual components of the coupling strip 1900 are not shown; only the coupling strip 1900 (depicted generically) and the bulk medium 1902 are shown. The area designated 2206 in both plots represents the background environment (e.g., the atmosphere). Both plots show the normalized density (A / m) of current induced in the bulk medium 1902 and shown by the shaded area 2204. 2 ) shows the current density in the bulk medium 1902 is greatest in a narrow region near the surface of the bulk medium 1902. Additionally, the plot in FIG. 22A shows the normalized electric field intensity (light gray scale region 2202) within the dielectric layer of the coupling strip 1900. In particular, the conductive shield layer 1906 shields the surrounding environment 2206 from the electric field generated by the current passing through the conductive layer 1904, e.g., reducing or eliminating electromagnetic radiation and protecting the coupling strip 1900 from external electromagnetic interference. The bulk medium 1902 also functions as a shielding layer, e.g., by minimizing or blocking the electric field. Thus, the conductive shield layer 1906 and the bulk medium 1902 can help to confine the electric field within the coupling strip 1900 (e.g., between the conductive shield layer 1906 and the bulk medium 1902) in embodiments of the coupling strip 1900. This effect reduces or prevents electromagnetic interference between the heating system and other nearby electrical components. Embodiments of the coupling strip 1900 in combination with the bulk medium 1902 can achieve performance comparable to stripline type transmission lines.

[0186] 19, the heating effect of the carrier strip 1900 on the bulk medium, and the impedance of each coupling strip 1900, can be adjusted by modifying the properties of the carrier strip, such as the thickness of the various layers 1904, 1906, and 1908, the width of the conductive layers, the layout of the conductive layers, the materials of each layer (including their dielectric constant and conductivity properties), etc., or by including impedance adjusting elements (capacitors, inductors, resistors, etc.). Additionally, the heating effect of the current generated in the bulk medium 1902 can also be modified by varying these properties, which, as noted above, also serve to adjust the proximity effect and path of the heating current through the bulk medium 1902.

[0187] For example, each of layers 1904, 1906, 1908 can be formed with respective thicknesses (D1-D4) generally ranging between 0.1 mils and 1 inch, or in some embodiments, between 0.5 mils and 10 mils. In some embodiments, coupling strip 1900 can be formed to space conductive layer 1904 at different distances from bulk medium 1902 and conductive layer 1904 from conductive shield layer 1906. In some embodiments, these distances are related by a ratio. For example, coupling strip 1900 can be formed such that the relative thicknesses D1 and D3 of dielectric layer 1908 are related by a ratio. For example, in some embodiments, the ratio of D1:D3 can be in the range of 1:1 to 1:5. The ratio D1:D3 can be reversed in other embodiments, for example, in the range of 1:1 to 5:1, to obtain the desired current density and / or impedance value for a given application. In one exemplary embodiment, D1 is 3 mils, D2 is 1 mil, D3 is 3 mils, and D4 is 1 mil. In another exemplary embodiment, D1 is 7.2 mils, D2 is 1.4 mils, D3 is 2.4 mils, and D4 is 1.4 mils. In yet another exemplary embodiment, D1 is 1000 mils, D2 is 50 mils, D3 is 500 mils, and D4 is 50 mils. In yet another exemplary embodiment, D1 is 10 mils, D2 is 2.5 mils, D3 is 50 mils, and D4 is 2.5 mils. In yet another example, D1 is 2.4 mils, D2 is 1.4 mils, D3 is 7.2 mils, and D4 is 1.4 mils. In yet another example, D1 is 17.6 mils, D2 is 9.8 mils, D3 is 24.5 mils, and D4 is 9.8 mils. In yet another example, D1 is 100 mils, D2 is 20 mils, D3 is 250 mils, and D4 is 20 mils. In yet another example, D1 is 5.5 mils, D2 is 2.5 mils, D3 is 9.0 mils, and D4 is 2.5 mils. In yet another example, D1 is 1.5 inches, D2 is 0.25 inches, D3 is 2.2 inches, and D4 is 0.25 inches. In yet another example, D1 is 3.8 mils, D2 is 2 mils, D3 is 3.8 mils, and D4 is 2 mils. In yet another example, D1 is 2.9 mils, D2 is 1.5 mils, D3 is 5.8 mils, and D4 is 2.5 mils.In yet another example, D1 is 5 mils, D2 is 2.5 mils, D3 is 25 mils, and D4 is 1.5 inches. In yet another example, D1 is 11 mils, D2 is 3 mils, D3 is 5.5 mils, and D4 is 3 mils. In yet another example, D1 is 21 mils, D2 is 1.5 mils, D3 is 7 mils, and D4 is 2.5 mils. In yet another example, D1 is 10 mils, D2 is 2.5 mils, D3 is 2 mils, and D4 is 2.5 inches. In yet another example, D1 is 4.5 inches, D2 is 0.25 inches, D3 is 1.5 inches, and D4 is 0.25 inches. In another example, D1 is 3 mils, D2 is 1 mil, D3 is 3 mils, and D4 is 1 mil. In yet another example, D1 is 10.2 mils, D2 is 3.5 mils, D3 is 40.8 mils, and D4 is 2.5 mils. In yet another example, D1 is 4.8 mils, D2 is 0.5 mils, D3 is 14.4 mils, and D4 is 0.5 mils. In yet another example, D1 is 15 mils, D2 is 1.4 mils, D3 is 3 mils, and D4 is 1.4 mils. In yet another example, D1 is 113 mils, D2 is 10 mils, D3 is 28.25 mils, and D4 is 10 mils. In yet another example, D1 is 127 mils, D2 is 5 mils, D3 is 254 mils, and D4 is 10 mils. In yet another example, D1 is 53 mils, D2 is 12 mils, D3 is 159 mils, and D4 is 12 mils. In yet another example, D1 is 13 mils, D2 is 1.4 mils, D3 is 2.6 mils, and D4 is 1.4 mils. In yet another example, D1 is 23 mils, D2 is 4 mils, D3 is 46 mils, and D4 is 4 mils. In yet another example, D1 is 11.5 mils, D2 is 2.8 mils, D3 is 57.5 mils, and D4 is 2.8 mils. In yet another example, D1 is 10 mils, D2 is 1.4 mils, D3 is 2.5 mils, and D4 is 1.4 mils.

[0188] Furthermore, the width of the conductive layer 1904 can generally range from a few inches to a few mils across the layer. FIG. 21 shows top views of several exemplary bonding strips (Examples 1-9) to illustrate various configurations of the conductive layer 1904 within the bonding strip 1900. The bonding strip 1900 in FIG. 21 is shown with the layers above the conductive layer 1904 (e.g., the second dielectric layer and the conductive shielding layer) removed for illustrative purposes. The cross-sectional area of ​​the conductive layer 1904 can vary along its length. For example, the width of the conductive layer 1904 can vary along its length to adjust the impedance of the bonding strip 1900 and, in some cases, to adjust the current density in the bulk medium and the conductive layer. Examples 1-9 show several exemplary width variation patterns for the conductive layer 1904 of the bonding strip 1900. For example, the width of the conductive layer 1904 across the bonding strip 1900 can vary between a maximum width and a minimum width. In some embodiments, the maximum width is only about 1.5 times the minimum width. In other embodiments, the maximum width is as much as 100 times the minimum width. For example, the width of conductive layer 1904 shown in Example 1 may be 1.5 inches at its widest point (e.g., top end) and 1 inch at its narrowest point (e.g., bottom end). In another example, the width of conductive layer 1904 shown in Example 1 may be 1 inch at its widest point (e.g., top end) and 10 mils at its narrowest point (e.g., bottom end).

[0189] In some embodiments, the thickness of the conductive layer 1904 may vary along its length. For example, the width of the conductive layer 1904 may vary along its length to adjust the impedance of the coupling strip 1900. In some embodiments, both the thickness and width and material of the conductive layer 1904 may vary along its length.

[0190] In some embodiments, the impedance of the bond line 1900 can be adjusted by including impedance-adjusting components (e.g., capacitors, inductors, and resistors) at one or more locations along the length of the conductive layer 1904. For example, the conductive layer can be divided into several segments along its length, and the segments can be connected by one or more impedance-adjusting components. For example, with reference to bonding strip example 4 of FIG. 21 , the conductive layer 1904 can be divided into two segments at region 2102, and an impedance-adjusting component (e.g., a capacitor, inductor, resistor, or combination thereof) can be electrically connected between each segment. Alternatively, or in addition, an impedance-adjusting component can be connected to the conductive layer as a shunt element between the conductive layer 1904 and either the bulk medium 1902 or the conductive shield layer 1906.

[0191] In some embodiments, the width, thickness, or both of the conductive shielding layer 1906 can vary along the length of the bonding strip 1900. In some embodiments, the width, thickness, or both of the dielectric layer 1908 can vary along the length of the bonding strip 1900. For example, in some embodiments, the cross-sectional areas of the conductive layer 1904, the dielectric layer 1908, and the conductive shielding layer 1906 can vary along the length of the strip 1900.

[0192] FIG. 23 shows layout diagrams (Layouts A-E) of several example arrangements of conductive layers 1904 within a bonding strip 1900. First, in a linear arrangement (shown in FIG. 21 ), the conductive layers 1904 extend linearly along the length of the bonding strip. Layouts A-E show bonding strips 1900 in which the conductive layers 1904 are arranged so that they extend along nonlinear patterns or paths. Specifically, the examples shown in FIG. 23 show the conductive layers 1904 arranged in a variety of different serpentine patterns. The illustrated serpentine patterns position segments of the conductive layers 1904 alongside each other across the width of the bonding strip 1900. Such arrangements allow for a reduction in the overall length of the bonding strip 1900 while maintaining a desired overall length of the conductive layers 1904. In some applications, maintaining a relatively uniform length for the conductive layers 1904 of different bonding strips 1900 can help maintain consistent impedance between bonding strips 1900 of different lengths. For example, in each of Layouts A and B, the conductive layers 1904 can be formed to the same overall length. However, the overall length of the joining strip 1900 of layout B can be reduced to half the length of the joining strip 1900 with linearly arranged conductive layers (e.g., as shown in FIG. 21 ). Similarly, the overall length of the joining strip 1900 of layout C can be reduced to one-third the length of the joining strip 1900 with linearly arranged conductive layers. Furthermore, joining strips 1900 of shorter lengths can be placed in space-constrained locations on the aircraft body. For example, joining strips 1900 with conductive layers arranged according to layouts A-E can be placed in narrow areas of the wing (e.g., wing tips) where joining strips 1900 with linearly arranged conductive layers would be too long to fit.

[0193] Each of layouts A-E shows a coupling strip 1900 having a conductive layer 1904 arranged along a non-linear path from input end 2302 to termination 2304. Layout A shows a coupling strip 1900 having a dual-arrangement of conductive layers 1904. The conductive layer 1904 of layout A includes, for example, two segments arranged next to each other along a U-shaped path from input end 2302 to termination 2304. FIG. 24A shows a cross-sectional view of coupling strip 1900 according to layout A taken along line AA′.

[0194] Layout B shows a coupling strip 1900 with a triple-arranged conductive layer 1904. The conductive layer 1904 of layout B includes, for example, three segments arranged next to each other along an S-shaped path from the input end 2302 to the termination end 2304. Figure 24B shows a cross-sectional view of the coupling strip 1900 according to layout B along line BB'.

[0195] Layouts C and D show a coupling strip 1900 with different conductive layers 1904 arranged in a quadruple configuration. Each conductive layer 1904 in layouts C and D includes four segments arranged side-by-side. In layout C, the segments of conductive layer 1904 are arranged, for example, in an M-shaped path (or a W-shaped path) from input end 2302 to termination end 2304. In layout D, the segments of conductive layer 1904 are arranged, for example, as a double-folded, side-by-side configuration. A similar technique can be applied to triple-folded conductive layers 1904, which can then be folded side-by-side. FIG. 24C shows a cross-sectional view of coupling strip 1900 along line CC′ in layouts C and D.

[0196] Layout E illustrates a more general arrangement of the conductive layer 1904. For example, layout E illustrates an example of a conductive layer 1904 in which multiple segments of different widths are arranged alongside one another. Additionally, in some embodiments, the conductive layer 1904 may include inter-segment interconnects 2306 at various locations between the segments, as shown in layout E. In some embodiments, the coupling strip 1900 may also include multiple signal input terminals 2302.

[0197] 25A shows a cross-sectional view of an exemplary configuration for attaching a bonding strip 1900 to a bulk media 1902. FIG. 25A illustrates a bottom-mount configuration. In the bottom-mount configuration, an adhesive 2502 is disposed between the bottom surface (e.g., the bottom dielectric layer) of the bonding strip 1900 and the surface of the bulk media 1902. For example, the adhesive may be, but is not limited to, a layer of double-sided adhesive (e.g., double-sided tape, etc.), resin, or epoxy.

[0198] Figure 25B shows a cross-sectional view of another exemplary configuration for attaching the bonding strip 1900 to the bulk media 1902. Figure 25B shows a top-mount configuration. In the top-mount configuration, an adhesive layer 2504 is applied over the bonding strip 1900 to attach the bonding strip 1900 to the skin 1902 of the aircraft. The adhesive layer 2504 may be, for example, an adhesive coating, an adhesive film, or a tape.

[0199] FIG. 26A is a cross-sectional view of a bonding strip 1900 with a double-sided adhesive bottom layer prior to installation on bulk media 1902, and FIG. 26B is a cross-sectional view of the bonding strip 1900 of FIG. 26A installed on bulk media 1902. In some embodiments, such as a bottom-mounted configuration, the bonding strip 1900 includes an adhesive bottom layer 2608. The adhesive bottom layer can be formed from a double-sided adhesive material (e.g., double-sided tape). In such embodiments, the double-sided adhesive material can function as the bottom dielectric layer (e.g., bottom dielectric layer 1908 of FIG. 19). In some embodiments, the adhesive bottom layer 2608 can be, for example, an adhesive coating or adhesive film applied to the bottom surface of the bottom dielectric layer 1908. Prior to installation, the bonding strip 1900 with the adhesive bottom layer 2608 can include a liner 2610 on the adhesive bottom layer 2608. The liner 2610 can be, for example, a release layer. For example, the liner 2610 may protect the adhesive bottom layer 2608 prior to installation. During installation, the liner 2610 may be removed from the adhesive bottom layer 2608 to expose its adhesive surface, and the bonding strip 1900 may be attached to the surface of the bulk media 1902.

[0200] In some embodiments, one or more adhesive layers 2604 and 2606 can be included to attach the dielectric layer 1908 to the conductive layer 1904 and / or to attach the conductive shielding layer 1906 to the dielectric layer 1908. In some embodiments, the bonding strip 1900 includes a protective layer 2602 over the conductive shielding layer 1906. For example, the protective layer 2602 can include, but is not limited to, one or more layers of polyurethane, polyfluoride, paint, paint substitute film, sealant, or combinations thereof.

[0201] In some applications, it may be necessary to heat a non-conductive bulk medium. In such cases, the heating systems and coupling strips described herein can be modified to heat the non-conductive bulk medium in such cases. For example, a buried layer can be used in conjunction with a coupling strip heating system to heat the non-conductive bulk medium.

[0202] 27A-27F show cross-sectional views of various embodiments of embedded bonding strips. FIG. 27A shows bonding strip 2700, which is similar to bonding strip 1900 of FIG. 19. Like bonding strip 1900, bonding strip 2700 has a multi-layer structure including a first dielectric layer 1908 on a bulk medium 1902, a conductive layer 1904 on first dielectric layer 1908, a second dielectric layer 1908 on conductive layer 1904, a conductive shielding layer 1906 on second dielectric layer 1908, and an optional protective layer 2706 on conductive shielding layer 1906. Protective layer 2706 is similar to protective layer 2602 described above. Bonding strip 2700 differs from bonding strip 1900 in that bonding strip 2700 is attached to the surface of a non-conductive bulk medium 2702, which includes a bulk conductive material 2704 embedded therein. For example, bulk conductive material 2704 can be formed as a metal foil, a metal tape, or as a metal layer embedded within non-conductive bulk medium 2702. For example, non-conductive bulk medium 2702 can be a layered material (e.g., a carbon fiber composite, a glass fiber composite, or a Kevlar composite) with bulk conductive material 2704 disposed between layers of non-conductive bulk medium 2702. Bulk conductive material 2704 can be made from a conductive layer such as, but not limited to, copper, a copper alloy (e.g., brass or bronze), silver, a silver alloy, aluminum, an aluminum alloy, titanium, a titanium alloy, chromium, nickel, a nickel alloy, a cobalt-based alloy, a corrosion-resistant steel, graphite, or a combination thereof.

[0203] 27A-27F, AC current passed through conductive layer 1904 of coupling strip 2700 generates heating current in bulk conductive material 2704 rather than non-conductive bulk medium 2702. Heat generated in bulk conductive material 2704 is then conducted (e.g., by thermal conduction) into non-conductive bulk medium 2702. In some examples, if the non-conductive bulk medium exhibits some conductive behavior, heat is generated in the non-conductive portions in addition to the bulk conductive material layer.

[0204] 27B shows an embodiment of a bonding strip 2700 that includes only a protective layer 2706, a conductive layer 1904, and a dielectric layer 1908. The bonding strip 2700 has the protective layer 2706 disposed over the conductive layer 1904 and the conductive layer 1904 disposed over the dielectric layer 1908. The dielectric layer 1908 is separated from the embedded bulk conductive material 2704 by a portion of the non-conductive bulk medium 2702.

[0205] 27C illustrates an embodiment of a bonding strip 2700 including a conductive layer 1904 embedded within a non-conductive bulk medium 2702. The bonding strip 2700 of FIG. 27C includes a protective layer 2706, a conductive shielding layer 1906, a dielectric layer 1908, and a conductive layer 1904. The bonding strip 2700 has the protective layer 2706, the conductive shielding layer 1906, and the dielectric layer 1908 disposed on the conductive layer 1904. The conductive layer 1904 is embedded within the non-conductive bulk medium 2702 and is spaced from the conductive bulk material 2704 by a portion of the non-conductive bulk medium 2702. For example, the conductive layer 1904 and the bulk conductive material 2704 can each be disposed between different layers of the non-conductive bulk medium 2702.

[0206] FIG. 27D shows a variation of the coupling strip 2700 shown in FIG. 27C, except that the protective layer 2706, the conductive shielding layer 1906, and the dielectric layer 1908 are absent.

[0207] Figure 27E shows a variation of the coupling strip 2700 shown in Figure 27D in which the geometric arrangement of the conductive layer 1904 and the bulk conductive material 2704 is reversed. That is, in the arrangement of the coupling strip 2700 shown in Figure 27E, the bulk conductive material 2704 is positioned closer to the surface of the non-conductive bulk medium 2702 than the conductive layer 1904.

[0208] 27F shows an embodiment of a bonding strip 2700 including a conductive layer 1904 and a conductive shielding layer 1906 embedded within a non-conductive bulk medium 2702. In the bonding strip 2700 shown in FIG. 27F, a portion of the non-conductive bulk medium 2702 (e.g., a layer of the non-conductive bulk medium 2702) separates the conductive layer 1904 from the conductive shielding layer 1906 and the bulk conductive material 2704. The non-conductive bulk medium 2702 serves a similar purpose as the dielectric layer 1908 in the bonding strip 1900 shown in FIG.

[0209] FIG. 28 shows a diagram of one embodiment of a coupling strip connector 2802. FIG. 2805 is a circuit diagram of the connector 2802. The connector 2802 includes an integrated impedance matching network 2804. The impedance matching network 2804 is electrically coupled between an input signal interface 2806 and the coupling strip 1900. For example, the input signal interface 2806 can be a coaxial cable connection. An input terminal 2810 of the input signal interface 2806 (e.g., a center wire of the coaxial cable connection) is coupled to the conductive layer 1904 of the coupling strip 1900 by a wire 2808. A ground terminal 2814 of the input signal interface 2806 (e.g., a shield of the coaxial cable connection) is coupled to one or both of the bulk medium 1902 or the conductive shield layer 1906 of the coupling strip 1900 by one or more wires 2812.

[0210] The impedance tuning network 2804 is configured to adjust the input impedance of the coupling strip 1900 to a desired level as measured at the input signal interface 2806. The impedance tuning network 2804 may be a fixed or variable impedance tuning network. For example, the impedance tuning network 2804 may be implemented as any of the impedance tuning networks described with reference to FIGS. 12-15B. In FIG. 2805, the impedance tuning network 2804 is implemented as a parallel capacitor C1 connected between ground and either or both of the conductive shield layer 1906 and the bulk medium 1902 (or the bulk conductive material 2704 when implemented for a non-conductive bulk medium) of the coupling strip 1900.

[0211] FIG. 29 shows a diagram of another embodiment of a combining strip connector 2902. The connector 2902 includes two input signal interfaces 2906A and 2906B, for example, for chaining multiple combining strips 1900 together. FIG. 2905 is a circuit diagram of the connector 2902. The connector 2902 includes an integrated impedance-matching network 2904. The impedance-matching network 2904 includes series and parallel impedance-matching elements 2904A, 2904B, and 2904C electrically coupled between the input signal interfaces 2906A, 2906B and the combining strip 1900. For example, the input signal interfaces 2906A and 2906B can be coaxial cable connections. The input terminals 2910 of each of the input signal interfaces 2906A, 2906B are coupled to the conductive layer 1904 of the combining strip 1900 and are coupled to each other by wires 2908. A ground terminal 2914 of each of the input signal interfaces 2906A, 2906B is coupled by one or more wires 2912 to one or both of the bulk medium 1902 or the conductive shield layer 1906 of the coupling strip 1900 .

[0212] In diagram 2905, the impedance adjustment network 2904 is implemented as a series capacitor C1 and two shunt capacitors C2, C3 connected between ground and either or both of the conductive shield layer 1906 and the bulk medium 1902 of the coupling strip 1900 (or the bulk conductive material 2704 when implemented for a non-conductive bulk medium).

[0213] 30 is a block diagram of a first exemplary bulk media heating system 3000 using coupling strips 1900 according to an embodiment of the present disclosure. The heating system 3000 includes a plurality of coupling strips 1900 spaced apart from one another and attached to a bulk media 1902 (e.g., an aircraft wing). Each coupling strip 1900 is connected to a power control system 3002. The power control system 3002 can be implemented as any of the embodiments of the power control system 104 described above. The power control system 3002 supplies AC current to each strip.

[0214] One end of each coupling strip 1900 (referred to herein as the "input end") is coupled to the power control system 3002 via a connector 3004. In the illustrated example, the opposite end of each coupling strip 1900 (referred to herein as the "end") has either an open termination 3006 or a closed termination 3008. The coupling strips 1900 are arranged in an alternating pattern, with each pair of adjacent coupling strips 1900 having a different type of termination. For example, one coupling strip 1900 of each adjacent pair has an open termination 3006 at its end, and the other coupling strip 1900 has a closed termination 3008 at its end. The open termination 3006 indicates that the end of that coupling strip 1900 remains open and is not connected to electrical ground through either the bulk medium 1902 or the conductive shielding layer of the coupling strip 1900. In some embodiments, the closed termination 3008 is a short or open circuit between the conductive layer of the coupling strip 1900 and either or both of the bulk medium 1902 or the conductive shield layer of the coupling strip 1900. In some embodiments, the closed termination 3008 is a capacitive termination, where a capacitor is connected between the conductive layer of the coupling strip 1900 and electrical ground. For example, a capacitor is connected between the conductive layer of the coupling strip 1900 and either the bulk medium 1902 or the conductive shield layer of the coupling strip 1900. In some embodiments, the closed termination 3008 is an inductive termination, where an inductor is connected between the conductive layer of the coupling strip 1900 and electrical ground. For example, an inductor is connected between the conductive layer of the coupling strip 1900 and either the bulk medium 1902 or the conductive shield layer of the coupling strip 1900. In some embodiments, the closed termination 3008 is a resistive termination, where a resistor is connected between the conductive layer of the coupling strip 1900 and electrical ground. For example, a resistor may be connected between a conductive layer of the coupling strip 1900 and either the bulk medium 1902 or the conductive shield layer of the coupling strip 1900 .

[0215] Complementary termination types can be applied to adjacent coupling strips 1900 to provide a desired input impedance to the power control system 3002, to provide a desired heating distribution across the bulk medium 1902, or a combination thereof. For example, the coupling strips 1900 can be installed on the bulk medium 1902 in a pattern of adjacent coupling strips 1900 having complementary termination types. For example, the terminations of adjacent coupling strips 1900 can alternate between an open termination 3006 and a short termination (e.g., a closed termination 3008 implemented as a short). In another example, the terminations of adjacent coupling strips 1900 can alternate between a closed termination 3008 implemented as a capacitive termination and a closed termination 3008 implemented as an inductive termination.

[0216] FIG. 31 is a block diagram of a second exemplary bulk media heating system 3100 using a bonding strip 1900 according to an embodiment of the present disclosure. The heating system 3100 is similar to the heating system 3000 described above, but adds a control system 3102 configured to drive variable terminations 3106 attached to the ends of each bonding strip 1900. The variable terminations 3106 include switchable terminations. In some embodiments, the variable terminations 3106 are configured to switch between a short termination and an open termination. For example, the variable terminations 3106 include a controllable switch coupled between the conductive layer of the bonding strip 1900 and electrical ground. The controllable switch can be implemented as an electronic switch (e.g., a transistor, a power diode, a thyristor, a silicon-controlled rectifier, etc.) or a mechanical switch (e.g., a relay). For example, the controllable switch is connected between the conductive layer of the bonding strip 1900 and either the bulk media 1902 or the conductive shield layer of the bonding strip 1900. An output of the control system is coupled to a control terminal of the controllable switch.

[0217] The termination of each bonding strip 1900 can be varied between an open circuit and a short circuit by opening and closing a controllable switch (or by turning an electronic switch off or on). For example, the control system 3102 controls the operation of the variable terminations 3106 of the bonding strips 1900 and, by manipulating the controllable switches, changes the termination type of the bonding strips 1900 as needed to heat the bulk medium 1902. The system 3102 can independently control the variable terminations 3106 of each bonding strip. In some embodiments, the control system 3102 can control groups (e.g., pairs or larger groups) of variable terminations 3106 of bonding strips in synchronization with one another. In some embodiments, the control system 3102 can switch the variable terminations 3106 of one or more bonding strips 1900 at regular intervals, for example, at a regular operating cycle. The operating cycle for switching the variable terminations 3106 can range from 0.01 Hz to 100 Hz.

[0218] In some embodiments, the control system 3102 controls the operation of the variable termination 3106 by alternately switching the variable termination 3106 between an open-circuit termination and a closed-circuit termination. For example, the control system 3102 switches half of the variable termination 3106 to a short-circuit termination and half of the variable termination 3106 to an open-circuit termination during the first half of the operating cycle. Then, during the second half of the operating cycle, the control system 3102 controls the variable termination 3106 so that the termination that was an open-circuit termination is switched to a closed-circuit termination and vice versa. The operating cycle for switching the variable termination 3106 can range from 0.01 Hz to 100 Hz.

[0219] In some embodiments, the variable terminations 3106 of each pair of adjacent coupling strips 1900 are controlled to maintain opposite types of terminations, i.e., the control system 3102 controls the variable terminations 3106 so that, on alternating half-cycles of operation, the termination of one coupling strip 1900 of each adjacent pair is configured as an open circuit and the termination of the other coupling strip 1900 of that pair is configured as a closed circuit.

[0220] The control system 3102 may be a computing device including one or more processors or microcontrollers configured to control the operation of the adjustable termination 3106. For example, the control system 3102 includes memory-stored instructions (e.g., software code) that, when executed by the control system 3102, provide appropriate control signals to controllable switches in the adjustable termination 3106. In some embodiments, the power control system 3002 and the control system 3102 may be integrated into a common power and control system.

[0221] In some embodiments, the variable termination 3106 is configured to switch between capacitive and inductive termination. For example, a controllable switch can be configured to switch between coupling the conductive layer of the coupling strip 1900 to a capacitor connected to ground and coupling the conductive layer of the coupling strip 1900 to an inductor connected to ground. As described above, grounding can be achieved through either the bulk medium 1902 or the conductive shielding layer of the coupling strip 1900. Furthermore, in such embodiments, the control system 3102 can be operated as described above to switch the variable termination 3106 alternately between conductive and inductive termination.

[0222] In other embodiments, the variable termination 3106 can be modified to switch between different termination types, for example, between open-circuit and capacitive termination, between short-circuit and inductive termination, between open-circuit and inductive termination, between short-circuit and capacitive termination, between open-circuit and resistive termination, between short-circuit and resistive termination, or other combinations thereof.

[0223] FIG. 32 is a block diagram of a third exemplary bulk media heating system 3200 using a coupling strip according to an embodiment of the present disclosure. The heating system 3200 is configured to alternately drive adjacent coupling strips 1900. The heating system 3200 is similar to the heating system 3000 described above, but adds a control system 3202 configured to drive a switchable connector 3204 attached to the input end of each coupling strip. The switchable connector 3204 includes a controllable switch positioned to connect and disconnect the associated coupling strip 1900 to the power control system 3002. The controllable switch can be implemented as an electronic switch (e.g., a transistor, a power diode, a thyristor, a silicon-controlled rectifier, etc.) or a mechanical switch (e.g., a relay). For example, the controllable switch is connected between the conductive layer of the coupling strip 1900 and the input terminal of the switchable connector 3204. An output of the control system is coupled to a control terminal of the controllable switch.

[0224] The control system 3202 controls the operation of the switchable connectors 3204 to alternately connect and disconnect the coupling strip 1900 with the power control system 3202, effectively turning the coupling strip 1900 on and off. For example, the control system 3202 can control the switchable connectors 3204 to alternately turn the coupling strip 1900 on and off. For example, the control system 3202 controls the operation of the switchable connectors 3204 of the coupling strip 1900 by operating a controllable switch to turn the coupling strip 1900 on and off as needed to heat the bulk medium 1902. In some embodiments, the control system 3102 can control the variable terminations 3106 of each coupling strip independently. In some embodiments, the control system 3102 can control the variable terminations 3106 of groups (e.g., pairs or larger groups) of coupling strips in synchronization with one another. In some embodiments, the control system 3102 can switch the variable terminations 3106 of one or more coupling strips 1900 at regular intervals, for example, according to a normal operating cycle. The operating cycle for switching the variable terminations 3106 can range from 0.01 Hz to 100 Hz. In some embodiments, the control system 3202 turns on the coupling strips 1900 with open terminations 3006 and turns off the coupling strips 1900 with closed terminations 3008 during the first half of the operating cycle. Then, during the second half of the operating cycle, the control system 3202 switches the switchable connectors 3204 to turn off the coupling strips 1900 with open terminations 3006 and turn on the coupling strips 1900 with closed terminations 3008.

[0225] The control system 3202 may be a computing device with one or more processors or microcontrollers configured to control the operation of the adjustable termination 3106. For example, the control system 3202 may include memory stored instructions (e.g., software code). 3202) which, when executed by control system 3202, provides appropriate control signals to controllable switches in variable termination 3106. In some embodiments, power control system 3002 and control system 3202 may be integrated into a common power and control system.

[0226] As used herein, the terms "perpendicular" or "substantially perpendicular" or "normal" or "substantially normal" refer to the relationship between two elements (e.g., lines, directions, axes, planes, surfaces, or components) that form a 90-degree angle within acceptable engineering or measurement tolerances. For example, directions can be considered perpendicular to one another if the angle between them is within an acceptable range of 90 degrees (e.g., ±1-2 degrees).

[0227] While this specification contains details of many specific embodiments, these should not be construed as limitations on the scope or scope of the invention, but rather as descriptions of features specific to particular embodiments of a particular invention. Certain features described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, even if various features are described above as acting in particular combinations and are initially claimed as such, one or more features from the claimed combinations may, in some cases, be deleted from those combinations, and the claimed combinations may be directed to subcombinations or variations of subcombinations.

[0228] Similarly, while operations are shown in the figures in a particular order, this should not be understood as requiring such operations to be performed in the particular order or sequence shown, or that all of the operations shown be performed, to achieve desirable results. In certain situations, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system modules and components in the above embodiments should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems may generally be integrated into a single software and / or hardware product or packaged into multiple software and / or hardware products.

[0229] Although specific embodiments of the subject matter have been described, other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As an example, the processes depicted in the accompanying figures do not necessarily require the particular order or sequential order shown to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous.

[0230] Control and Sensing: In some embodiments, the controller is a group of sensors and circuitry that performs the control, sensing, and monitoring functions of the power control system. The controller can be, for example, the power control system 104 described with reference to FIG.

[0231] In some embodiments, the control functions include switching the entire power control system on and off, switching on and off specific sections of the power control system designated to supply power to specific target areas of the bulk media, and adjusting the amount of power output to specific areas of the bulk media.

[0232] In some embodiments, the control function includes control of a dynamic regulation network.

[0233] In some embodiments, the monitoring functions include any combination of the following: assessing the health and proper functioning of the heating system as a whole, assessing the health and proper functioning of specific parts and sections of the heating system, performing fault detection on the heating system as a whole, performing fault detection on specific parts and sections of the heating system, performing fault notification to a system user or users, performing fault notification to maintenance or inspection personnel, etc.

[0234] In some embodiments, fault detection refers to any combination of the following faults: detection of electrical faults, detection of heating malfunction, detection of coupling strip fault, or detection of bulk media damage (even when the heating system is functioning properly and undamaged). In this disclosure, a coupling strip may also be referred to as a "strip line" or sometimes simply a "line." The coupling strip may include structural layers, such as those described with reference to FIGS. 19 and 23-27F. As described below, in some embodiments, a coupling strip may include multiple conductive paths, such as sense lines and carrier lines. As used herein, a carrier line refers to a conductive path within a coupling strip that carries the current used to heat the bulk media. A sense line is a separate conductive path that can carry a smaller current, intermittently or continuously, used to detect faults in the carrier line or the entire coupling strip.

[0235] In some embodiments, the electrical fault includes, but is not limited to, input and output power, voltage, or current at any stage of the power control system being at a level that is not within a set interval. In some embodiments, the electrical fault includes a temperature of a circuit, device, or component of the power control system being higher or lower than expected for normal operation of the heating system. In some embodiments, the electrical fault includes input and output impedance at any stage of the power system being at a level that is not within a set interval.

[0236] In some embodiments, a heating malfunction includes, but is not limited to, an overheated condition in any region of the bulk media compared to normal operation of the heating system, an underheated condition in any region of the bulk media compared to normal operation of the heating system, In embodiments where the heating system is a de-icing system, a heating malfunction may include any region of the bulk media not being completely de-iced, freezing or re-freezing of precipitate on the bulk media during or after the de-icing or anti-icing process.

[0237] In some embodiments, a failure of the bonding strip may include any of the following: temperatures at or near the bonding strip and at one or more locations on the bulk media that are higher or lower than expected for normal operation of the heating system; a break anywhere in the bonding strip; a short circuit within the bonding strip (between the trace and the shield or within the trace itself); a short circuit between the bonding strip and the bulk media; a short circuit and open circuit at the input connector of the bonding strip; an open circuit within the bonding strip; delamination of the bonding strip structure; a burnt section of the bonding strip; delamination between the bonding strip and the bulk media; delamination of the bonding strip from the bulk media; mechanical damage such as dents, holes, bumps, cuts, wrinkles, burrs, etc. caused by events such as hail, lightning, mishandling of the bonding strip by a maintenance person or the like, or walking on the bonding strip by a maintenance person or the like; corrosion of the bonding strip; electrostatic discharge between the bonding strip and the bulk media, between the electrode / connector and the bonding strip, or between the electrode / connector and the bulk media; corrosion or oxide buildup of the bonding strip;

[0238] In some embodiments, the sensing capabilities include all sensors used to input and feed back voltage, current, power, forward power, reflected power, voltage standing wave ratio (VSWR), time domain reflectometry (TDR), temperature, etc. to the controller, as well as ice sensors.

[0239] In some embodiments, some or all of the elements of the controller are distributed within the power control system. In some embodiments, some or all of the elements of the controller are installed so that they are independent from the rest of the control system. In some embodiments, these elements are housed in separate, dedicated enclosures.

[0240] In some embodiments, two or more elements of the controller are independent of one another, and are configured such that at least two of these elements must fail simultaneously for the controller to function. In such embodiments, the controllers are independent of one another, which increases the reliability of the controller and reduces the reliability required of each of these elements to meet the controller requirements, making their design, implementation, and integration easier and simpler. This is particularly advantageous in applications where safety and controller reliability are critical or regulated, particularly for heating systems installed on aircraft.

[0241] In some embodiments, two or more subsystems are independently configured to perform monitoring functions to achieve reliability and safety requirements. In some embodiments, two or more subsystems are independently configured to perform sensing functions to achieve reliability and safety requirements. In some embodiments, two or more subsystems are independently configured to perform control functions to achieve reliability and safety requirements. In some embodiments, any combination of control, sensing, and monitoring subsystems are independently configured to achieve reliability and safety requirements.

[0242] In some embodiments, two identical sensors are used at some sensor locations. In such embodiments, both sensors may be connected to and provide data to the same monitoring subsystem. For example, they may each be connected to a separate monitoring subsystem, configured to operate independently of each other, or they may each be connected to two or more monitoring subsystems, both configured to operate independently of each other.

[0243] In some embodiments, two independent sensors are used to collect information about similar areas. Independence can be achieved by using different sensor types and / or by monitoring the same area or collecting similar information while being located within at least some distance of each other. In such embodiments, both sensors can be connected to the same monitoring subsystem to provide data, each of them can be connected to a separate monitoring subsystem that is configured to operate independently of each other, or each of them can be connected to two or more monitoring subsystems that are both configured to operate independently of each other.

[0244] In some embodiments, any combination of the controller's control, sensing, and monitoring subsystems is configured to optimize the reliability and safety of its most critical functions. In the case of a heating system used for aircraft de-icing and anti-icing, in some embodiments, such functions include the following combinations: detecting and notifying the pilot of heating system faults, detecting and notifying the pilot of power control system electrical faults, detecting and notifying the pilot of coupling strip faults, and detecting and notifying the pilot of power control system and bulk media heating faults.

[0245] In some embodiments where the heating system is used for aircraft de-icing and anti-icing, the controller is further optimized to verify that critical aircraft surfaces, once de-iced, are free of frost, frozen precipitation, and frozen contaminants, which refer to sleet, snow, slush, ice, or other materials that may adhere to the aircraft's skin and interfere with proper operation.

[0246] In some embodiments, the controller and the layout of the coupling strips on the bulk medium are designed and optimized to work together. In such embodiments, the coupling strip layout on the bulk medium can be arranged to create regions of interest at selected locations. Such regions can be, by way of example, regions that remain cooler by design than the rest of the bulk medium upon activation of the heating system, or regions that may be the first to experience a refreezing event during operation of the heating system or after deactivation (e.g., from ongoing freezing or frozen precipitation, or from frozen precipitation, or melted contaminants flowing over the surface of the bulk medium). In such embodiments, sensors in the controller can be positioned to collect information about these regions and help assess whether the heating system is functioning properly or whether the bulk medium is experiencing a freezing or refreezing event. In some embodiments, the bulk medium can be locally altered in some of these regions to ensure that they become cooler than other regions of the bulk medium during operation of the heating system, or that they are the first regions to experience a refreezing event (e.g., by adding relatively small features, such as edges or ridges, to allow meltwater to accumulate and stagnate in the cooler regions, facilitating refreezing). In some embodiments, such areas are selected so that they are easily observable by a user of the heating system (e.g., in the case of an aircraft de-icing system, so that they are easily visible to a pilot from the cabin or cockpit of the aircraft), such that a user can infer whether the bulk media has experienced a de-icing event based on visual observation of these areas.

[0247] In some embodiments where the heating system is used for aircraft de-icing and anti-icing, the controller is further optimized to perform verification that specific areas are free of frozen or frozen precipitation and contaminants. Such areas may include horizontal and angled upper surfaces exposed to vertical and near-vertical precipitation, and the upper surfaces of wings and horizontal stabilizers.

[0248] In some embodiments, part of the monitoring function is performed using analytical methods that leverage machine learning, computer vision, and artificial intelligence techniques on the data collected by the sensing subsystem, which in some embodiments can train the technology using data collected empirically from tests performed on the heating system, and can continually train and improve using data collected by installed heating systems.

[0249] In some embodiments, the controller may use a timer to measure time information such as the start-up time of the heating system, the time since the heating system was last started, and the time since the system was last shut down, etc. In some embodiments, information from the timer may be used in conjunction with information from the sensing subsystem for analysis to help the controller perform its intended function.

[0250] As shown in FIG. 37A, a cockpit display and annunciation system may be provided in some embodiments. This system may have multiple indicators to inform the pilot of the system's status. For example, an "ON" indicator may illuminate if the system is powered, and a "WARM" indicator may illuminate if some or all of the required temperature sensors are at or above 15°C. For example, an "OK" indicator may illuminate when some or all of the required temperature sensors indicate a temperature above 15°C for at least 15 minutes. An "OVHT" indicator may illuminate if an overheating condition is detected, such as if any temperature sensor reaches a temperature above 150°C. A "SYSTEM FAIL" indicator may illuminate for various reasons indicating a potential system failure. For example, if the system has been "on" for a predetermined period of time (e.g., 25 minutes) without reaching at least a "warm" state. In another example, if the system is "on" and has been in an "OVHT" state for 10 seconds or more, "SYSTEM FAIL" may illuminate. The temperatures and times listed above are for illustrative purposes and may be changed or adjusted without departing from the scope and spirit of the present disclosure.

[0251] FIG. 37B shows an alternative example of a cockpit display showing system functionality states for a "DE-ICE" system state and an "ANTI-ICE" system state. In this example illustration, the cockpit display may indicate whether the system is in "OFF," "GROUND DE-ICE," "GROUND ANTI-ICE," or "FAULT" status. In some embodiments, separate displays may be presented for each area of ​​the aircraft or area of ​​interest.

[0252] Figure 37C shows an example of where the cockpit view of Figure 37B would be located within the aircraft cabin. Figure 37B can be located in the passenger compartment of the aircraft. In Figure 37C, the cockpit view is located in the upper right corner of the aircraft cockpit, as indicated by the dashed box.

[0253] In some of the above embodiments, the controller's sensing subsystem can include one or more wireless sensors, such as one or more wireless temperature sensors or one or more wireless ice sensors, that can be configured to transmit data to a central receiver over a wireless data network. This reduces the need for additional sensor wires and allows access to various physically separate locations on the bulk medium. The wireless sensors can derive power from the coupling strip 1900 using a direct electrical connection, for example, by utilizing a low-voltage, low-current DC bias maintained on the coupling strip 1900 or by directly harvesting power from AC current passing through the coupling strip. Alternatively, the wireless sensors can derive power without a direct connection to the coupling strip 1900, for example, by utilizing near-field electromagnetic radiation via an antenna or coil.

[0254] Temperature Sensing In some embodiments, the sensing subsystem of the controller includes a temperature sensor that can be used to make point measurements or to measure parameters such as maximum, minimum, average, or temperature mapping over a specified area (e.g., using a sensor mat with multiple sensors that can extract area information).

[0255] In some embodiments, the temperature sensor can include any of the following sensor types: thermocouples, resistance temperature detectors (RTDs), thermistors, fiber optics, and infrared sensors. Thermocouples can be used to measure temperature by measuring changes in voltage. Thermocouples are low-cost, easy to implement, and have a wide measurement range. Because signals are on the order of tens of millivolts, significant noise reduction may be required for accurate measurements in the presence of electromagnetic interference. Resistance temperature detectors (RTDs) can measure temperature by measuring changes in sensor resistance. These elements are typically constructed of platinum and have very high accuracy. This requires performing a four-wire measurement or keeping the leads short, for example, by performing a local voltage measurement that is then converted to a digital signal. Thermistors are similar to RTDs in that they calculate temperature based on resistance measurements. Thermistors have the added advantage of having a high baseline resistance, potentially negligible lead resistance. Fiber optic sensors are typically based on fiber Bragg gratings. The gratings reflect light of specific wavelengths. As the temperature changes, the reflected wavelengths change predictably, allowing the temperature to be calculated. Because each grating reflects only a small band of wavelengths, multiple sensors can be integrated into a single fiber optic element and measured with a single instrument. The fiber optic element itself is very small, ~0.1 mm in diameter, but can be meters or even tens of meters long. Because the measurement is optical, it needs to be free from RF interference.

[0256] In some embodiments, temperature sensors are positioned on the bulk medium in a manner that allows for sensor placement as described previously herein. In some embodiments, temperature sensors can be widely spaced apart, for example, beneath the bulk medium's skin, or both, supported by a lumped capacitance model in which the temperature of the solid is assumed to be spatially uniform within the volume. This is the case when the Biot number Bi is sufficiently small (e.g., Bi<0.1), defined as Bi=h / k·L, where k is the thermal conductivity of the solid, h is the convective heat transfer coefficient, and L is the characteristic dimension of the volume. Lumped capacitance models are particularly useful within volumes where Bi is sufficiently small, since they can assume that the temperature of the bulk medium is nearly uniform, reducing the number of sensors attached to the bulk medium, system complexity, cost, and installation effort. Such techniques are particularly effective for bulk media with high thermal conductivity, such as aluminum alloys that commonly constitute aircraft skins, where the Biot number remains small enough over a relatively large area to justify the use of a limited number of temperature sensors and sensing points. In some embodiments, temperature sensors can be positioned on the bulk media to be located at specific locations, such as hot spots, cold spots, and refreeze spots, among other spots. A hot spot may be a location selected to operate at a relatively higher temperature than other locations on the bulk media when a heating system is activated. A hot spot sensor can be used to perform general controller functions and can be used to detect overheating events of the bulk media or bonding strip. A cold spot may be a location selected to operate at a relatively lower temperature than other locations on the bulk media when a heating system is activated. A cold spot sensor can be used to perform general controller functions and can be used to detect improper heating of the bulk media or bonding strip. A refreeze spot is a location selected to experience a freeze or refreeze event sooner than other locations on the bulk media when a heating system is activated or after it is deactivated. A refreeze spot sensor can be used to perform general controller functions.It can also be used to detect refreezing events or improper heating on the bulk media or bonding strip. Other spots can be placed in other areas of interest as previously described herein.

[0257] In some embodiments, the layout of the bonding strips on the bulk media can be optimized so that there are designated areas with the above spots selected for parameters such as ease of access, ease of installation, or ease of visual observation by a user of the heating system. For example, as shown in Figure 33, an aircraft pilot has a limited line of sight 3302 visible from the cockpit. As a result, portions of the aircraft are invisible to the pilot (3304) and portions of the aircraft are visible (3306). In some embodiments, refreezing or cold spots can be selected within the visible portion of the aircraft (3306) to allow visual confirmation by the pilot.

[0258] Figure 33 further illustrates an exemplary temperature overlay of the wing when the system is active. Location 3308 on the wing is an example of a cold spot that may be selected or designed and monitored for viewing by the pilot so that the pilot can verify the anti-icing condition before takeoff. For example, as shown, location 3308 correlates to a relatively cooler area of ​​the wing (indicated by the yellow gradient) relative to the majority of the wing in the heating pattern generated by the heating element (indicated by the red gradient).

[0259] The locations of cold and / or hot spots can be engineered, for example, by arranging heating strips (such as bonding strips) on the surface of the aircraft in a pattern that creates a heating pattern on the aircraft skin that has a locally lower or warmer skin temperature relative to the rest of the aircraft. For example, the bonding strips can be arranged in a shape that provides locally lower (or higher) power density (wider wire spacing), or selected bonding strips can be operated at lower (or higher) power density in high (low) thermal mass locations, or the output power can be adjusted locally to create a heating pattern that provides cold / hot spots in desired locations.

[0260] In some embodiments, adding redundancy to the sensor subsystem using at least two independent sets of temperature sensors can improve the reliability of critical functions of the controller. In some embodiments, independence can be achieved by adding two identical temperature sensors at each designated sensor location. In some embodiments, independence can be achieved by adding two different temperature sensors (e.g., sensors from different manufacturers or types) at each designated sensor location. In some embodiments, independence can be achieved by adding two temperature sensors far enough apart from each other to reduce the chance of both sensors failing simultaneously, while still being close enough to monitor equivalent parameters. In some embodiments, independence can be achieved using any combination of these methods. In some embodiments, the sets of independent sensors can send information to a single monitoring subsystem, send information to independent sets of monitoring subsystems each dedicated to the independent sets of sensors, or all send information to two independent sets of monitoring subsystems.

[0261] In some embodiments, temperature sensing can be achieved by using one or more temperature sensors (or temperature elements) that are an integral part of the bonding strip, for example, in addition to or instead of using temperature sensors separately located on the bulk. Examples of temperature sensors are described in more detail in the "Temperature Sensing" section above. For example, a temperature sensor can be attached to the bonding strip or a nearby sense line (sense lines are described in more detail below) and can short or open when the temperature exceeds a predetermined threshold. The short or open can be detected elsewhere, for example, at an input connector or in the power control system (system 104). This allows temperature detection at the location of the temperature sensor.

[0262] In some embodiments, an array of temperature sensors can be arranged in parallel. For example, a parallel arrangement can include an array of parallel overheat or underheat sensors arranged as a thermostatic control loop. A thermostatic control loop is a hysteretic control method that uses temperature sensor information to maintain the temperature of a system, such as the heating system 100 of FIG. 1, within a predetermined range, for example, above a minimum temperature Tmin and below a maximum temperature Tmax.

[0263] In some embodiments, an array of temperature elements can be arranged in series, for example, temperature elements can be attached along the coupling strip 1900, such as to a sensing line on or near the coupling strip, or along another cable strip, and arranged to force a thermal shutdown if the temperature becomes too high at any point in the series configuration.

[0264] In some embodiments, temperature elements such as periodic thermistors of different values ​​can be placed in parallel so that when a particular temperature element along the line becomes overheated, an analog value can be detected and decoded to indicate not only that the bonding strip has detected overheating, but also the specific location along the bonding line where the fault occurred.

[0265] In some embodiments, temperature sensing can be achieved by using traces on a flexible circuit, by using additional sense lines running alongside the carrier lines within the bonding strip (sense lines acting as wiring to and from a temperature sensor implemented within the bonding strip), by using additional sense lines and sensors implemented within a sensing strip installed independently from the bonding strip, or by implementing a temperature sensor within the bonding strip along with the carrier lines in a configuration such as a periodic capacitor, a parallel plate capacitor, a trace inductor, or a combination thereof.

[0266] In some embodiments, temperature can be measured as a function of time. For example, temperature changes can be measured and recorded at regular sampling intervals and stored as a vector representing time-based changes in temperature rather than static temperature measurements. Time-based temperature measurements can enable more complex mathematical analysis, such as rate of change (e.g., time-based derivatives) or total heat output (e.g., integrals). In such embodiments, the controller can perform various evaluations, including an evaluation of the current de-icing status, based on temporal information related to temperature changes. As a specific example, in response to a temperature reading sensed by a temperature sensor hovering around 0°C, the controller can determine that the energy supplied by the bulk media heating system is going into latent heat of melting and therefore a de-icing operation is in progress. Furthermore, if the temperature reading sensed by the sensor rises after hovering around 0°C, the controller can determine that the de-icing operation is complete because the energy supplied by the bulk media is going toward increasing temperature and not into latent heat as frozen contamination is dissolved and removed from the bulk media. In other words, the point at which the bulk media is de-iced can be determined when the temperature plotted against time becomes relatively flat (e.g., zero slope) for a predetermined period of time followed by a period of positive slope.

[0267] In some cases, temperature can also be measured as a function of time, and de-icing status can be estimated as well, as further described in the "Ice Detection / Sensing" section below.

[0268] Fig. 38 4 shows a plot of impedance and temperature as a function of time on a coupling strip. As shown in plot 4000, the temperature reading remains near a fixed value (10°C) while the de-icing operation is in progress (from about 07:00 to 07:30), and once the de-icing operation is complete, the temperature reading increases (starting at about 07:30).

[0269] Additionally, in embodiments where the bulk medium is composed of a highly thermally conductive material (such as aluminum), a lumped-capacity thermal model can be used as the basis for assessing the de-icing status of the system. The controller can also use the lumped-capacity thermal model to determine the location of cold spots on the bulk medium and to determine the temperature of the cold spots. This can reduce the total number of sensors required and facilitate more effective sensor placement, including both placing sensors below (i.e., rather than above) the aircraft skin or taking advantage of the thermal conductivity of the bulk medium.

[0270] Ice detection / sensing In some embodiments, the sensing subsystem of the controller includes an ice detector or sensor. Ice detection refers to a method of recognizing ice or frozen precipitation or contaminants, including but not limited to snow, ice, slush, or similar forms of frozen precipitation that accumulate on a surface.

[0271] In some embodiments, ice detection is used to determine if a structure needs de-icing, to track and monitor progress of de-icing, and to monitor ice accumulation after de-icing.

[0272] In some embodiments, ice detection is achieved using a transducer or multiple transducers to monitor acoustic parameters of the structure, including, but not limited to, damping coefficient, resonant frequency, and frequency response. In some embodiments, ice detection is achieved by observing changes in polarized light. In some embodiments, variable polarized light is used to observe changes in incident unpolarized light after interacting with the ice. In some embodiments, changes in incident polarized light are observed. In some embodiments, changes in the intensity of reflected light can be used to detect ice formation. In some embodiments, ice is detected with one or more sensors on the snow / ice collecting surface. As snow or ice collects on the surface, it closes the sensor aperture, signaling the presence of ice. In some embodiments, infrared radiation from the surface can indicate the presence of ice. This includes, but is not limited to, variations in surface emissivity and calculations of surface temperature to determine whether conditions are favorable for ice formation. In some embodiments, ice detection can be achieved using sensors attached to critical surfaces. As ice or frozen precipitation collects on the sensor, a measurable change in electrical impedance occurs. In some embodiments, ice sensors exploit the fact that the presence of ice near a coupling strip affects the electromagnetic field surrounding the line, detectably affecting the frequency and / or time domain response of the coupling strip to electrical signals. These changes can be measured and used to indicate the presence of ice on a structure. In some embodiments, the presence of ice can be predicted by a temperature gradient across the structure or by the rate of change of temperature, which can be measured with the temperature sensors described above. In some embodiments, any of the sensors described herein can be surface mounted to a structure.

[0273] In some embodiments, ice sensors are positioned on the bulk media in a manner similar to the temperature sensors positioned as previously described herein. In some embodiments, ice sensors can be positioned on the bulk media specifically to be positioned at specific locations, such as hot spots, cold spots, or refreeze spots. Hot spot sensors can be used to perform general controller functions and can be used to detect overheating events of the bulk media or bonding strip. Cold spots can be locations selected to operate at relatively lower temperatures than other locations on the bulk media when a heating system is activated. Cold spot sensors can be used to perform general controller functions and can be used to detect improper heating of the bulk media or bonding strip. Refreeze spots can be locations selected to be more likely to experience a freeze or refreeze event than other locations on the bulk media when a heating system is activated or after it is deactivated. Refreeze spot sensors can be used to perform general controller functions and can be used to detect refreeze events or improper heating of the bulk media or bonding strip. Other spots can be placed in other areas of interest, such as those previously listed herein.

[0274] In some implementations, the layout of the bonding strips on the bulk medium can be optimized so that the above-mentioned spots are present in designated areas selected for parameters such as ease of access, ease of installation, or ease of visual observation for users of the heating system.

[0275] In some embodiments, at least two independent sets of ice sensors may be used to improve the reliability of critical controller functions by adding redundancy to the sensing subsystem. In some embodiments, independence may be achieved by adding two identical ice sensors at each designated sensor location. In some embodiments, independence may be achieved by adding two different ice sensors (e.g., sensors from different manufacturers or types) at each designated sensor location. In some embodiments, independence may be achieved by adding two ice sensors far enough away from each other to reduce the chance of both sensors failing simultaneously, while still being close enough to monitor comparable parameters. In some embodiments, independence may be achieved using any combination of these methods. In some embodiments, the sets of independent sensors may send information to a single monitoring subsystem, each set of independent sensors may send information to a set of independent monitoring subsystems dedicated to that set, or all may send information to at least two sets of independent monitoring subsystems.

[0276] In some embodiments, the sensing subsystem of the controller can include one or more capacitance sensors. The one or more capacitance sensors can be used alone or in combination with other sensors, such as temperature sensors, to distinguish between ice and water. For example, a circuit board, such as a flexible printed circuit board (or flex PCB) including an array of one or more capacitance sensors, can be placed on the surface of the bulk media to measure changes in capacitance readings on the surface due to, for example, the presence of ice or water. As another example, the capacitance sensors can be placed under a cover layer (e.g., a paint replacement film) of the bulk media.

[0277] In some embodiments, the temperature on the bonding strip 1900 can be derived from impedance measurements, which can also be measured as a function of time, for example, by comparing the impedance measurements to a database of reference plots of frequency response at various temperatures. For example, a test system can collect data and record the impedance frequency response as a function of ambient temperature. A controller can use the recorded data to infer the temperature of the bonding strip based on the impedance readings.

[0278] In some such embodiments, the coupling strip 1900 includes a material that exhibits significant and predictable impedance variation with temperature, thereby facilitating the use of impedance measurements to assess the temperature of a target region of the bulk medium. For example, the coupling strip 1900 can be constructed in part using a dielectric material or conductor whose permittivity or conductivity can change predictably with temperature, thereby locally varying the impedance in the target region of the bulk medium. For example, the coupling strip 1900 can be constructed using one or more of an acrylic adhesive, a silicone adhesive, an ethylene vinyl acetate adhesive, a polysulfide sealant, a polyurethane sealant, Mylar, PTFE, FEP, Kapton, or an epoxy-based material.

[0279] For example, to determine the current temperature of a particular coupling strip, the controller can measure the impedance value of the particular coupling strip and compare the impedance value to temperature values ​​in a look-up table. As another example, the controller can take an impedance measurement and then calculate the temperature from the measured impedance value (e.g., based on a mathematical relationship between impedance and temperature). As a particular example, an acrylic adhesive material can be used to construct the lower dielectric layer of the coupling strip that separates the strip from the bulk medium.

[0280] Fig. 391 is a 3D plot of the dielectric constant of an exemplary acrylic adhesive material. Fig. 40 1 is a plot of the dielectric constant of an exemplary acrylic adhesive material.

[0281] Fig. 39 As shown in the figure, the dielectric constant (ε r ) varies with temperature (°C). Specifically, the dielectric constant drives the characteristic impedance of the system, including the coupling strip and the bulk medium. Therefore, as the temperature of the coupling strip changes, the dielectric constant changes accordingly. This causes the impedance of the system to vary.

[0282] In some embodiments, the impedance can be measured as a function of time, and because impedance generally varies with temperature, the de-icing condition can be determined from the impedance measurement using a detection scheme similar to that for temperature measurements. In particular, the point at which the bulk medium is de-iced can be determined when the impedance plotted with respect to time becomes relatively flat (e.g., zero slope) for a predetermined period of time following a period of positive or negative slope. Fig. 38 As shown in plot 4500, the impedance readings remain near a fixed value (5.7 Ω) while the de-icing operation is in progress (from approximately 07:00 to 07:20), and once the de-icing operation is complete, the impedance readings increase (at approximately 07:20).

[0283] Electrical In some embodiments, the controller includes control, sensing, and monitoring subsystems used to measure electrical parameters and performance, including voltage, current, input and output power at any output impedance at any stage of the heating system, including the power control system, interconnects, cables, connectors, and electrodes.

[0284] In some embodiments, the controller uses and analyzes the collected electrical parameters to assess the health of the heating system and its components, control the amount of power directed to target areas of the bulk media, ensure proper heating is occurring, report faults and errors to a user of the system, and log the collected data for further diagnosis from a user or maintenance personnel of the system.

[0285] In some embodiments, the controller may verify that all measured electrical parameters are within expected ranges in order to perform its control and monitoring functions.

[0286] In some embodiments, the output and input power of any stage of the power control system are measured simultaneously, allowing the controller to assess the power level and efficiency of said stage. By way of example, monitoring the power level and efficiency (input power divided by power delivered to the heating element) can detect system faults and signal de-icing failures. For example, this can be used to deduce that insufficient power delivered to the load will result in incomplete de-icing.

[0287] In some embodiments, the voltage-to-current ratios of the input and output of any stage of the heating system are measured and utilized by the controller. By way of example, in some stages of heating system embodiments, changes in downstream electrical elements cause changes in the voltage-to-current ratios of upstream stages in the electrical system, and detecting these changes allows for the detection of remote downstream faults and performance indicators.

[0288] Frequency domain analysis is commonly used in the analysis of cables and high frequency systems, for example, by determining the magnitude and phase of the circuit's input impedance over a range of frequencies. This information can be used to assess the health of a heating system, and in embodiments where the system includes coupling strips (which act as transmission lines), it can be used to assess the strip's characteristic impedance, propagation constant, termination, and length.

[0289] For example, for an open-terminated transmission line of known characteristic impedance, the impedance examined may vary from 0 for lengths equal to odd multiples of one-quarter of the wavelength of the traveling signal to Z0 for lengths equal to multiples of one-half the wavelength.

[0290] This analysis can be performed from a single point, or if both ends of the cable are accessible, a "two-port" measurement can be performed to analyze the transmission and reflection of a signal passing from one port to another.

[0291] Measurements across the frequency domain are most commonly performed with a network analyzer, a tool that transmits a series of frequencies at a high level, calculates impedance from voltage / current ratios, interpolates, and displays the data.

[0292] They are also tools that can be used to verify if there have been any changes in the transmission line system. In complex electrical systems where cables travel long distances and are difficult to access, transmission line analysis is an invaluable tool for checking for cable breaks or other undesirable changes.

[0293] Cuts or other direct damage to coupling strips or other cables in the heating system can be detected by impedance measurements. See the examples for more details. For example, it is also possible to determine whether a coupling strip or cable is completely cut or partially cut. An example of a detectable error is a change in length. For example, if a coupling strip or cable is cut, it becomes shorter (its termination may be changed) and its input impedance changes according to the following formula:

number

[0294] Faults can also be detected when terminations are altered away from expected values, for example, if a coupling strip that is normally open terminated becomes shorted, or if a coupling strip that is normally shorted is cut or peeled off, resulting in an open termination.

[0295] It is important to note that passive monitoring of the operating power control system can detect impedance at operating frequencies, so the diagnostic functions described in the remainder of this specification can be performed during operation.

[0296] While network analyzers are active, relying on sending sinusoidal signals to the device under test to obtain its frequency response, passive monitoring involves monitoring the signals (voltage and current) flowing through the device during normal operation and calculating its impedance. Because information can only be extracted from operating signals and conditions, passive monitoring does not provide as comprehensive information as a full frequency sweep. However, it can still be used to monitor for faults. Furthermore, it can operate continuously, even while the heating system is running.

[0297] There are three basic elements to implementing passive monitoring: Interface: The interface between the power system and the monitoring system must be carefully designed. For example, it is important to ensure that excessive power, such as that designated for ice protection, does not enter the monitoring system. ·division: Another critical element of the system is the calculation of impedance from voltage and current (e.g., V / I), which must be accurate and reasonably fast, as well as preserve phase information. Signal conversion: Once the impedance signal is calculated, it is typically converted into a form more useful to the monitoring subsystem, for example using an analog-to-digital converter.

[0298] Passive monitoring is a valuable tool for protecting the entire system, being able to detect faults in real time and prevent damage to the power system that may be caused by said faults.

[0299] In some embodiments, the controller can alternate between operating the network analyzer system and providing power to the coupling strips. For example, the controller can intermittently switch power provided to the coupling strips while connecting the network analyzer to check for faults. After the network analyzer acquires measurements, power flow to the coupling strips can be resumed. The network analyzer can then be disconnected to prevent damage to the power signal. In some embodiments, the network analyzer can rotate while performing measurements on different coupling strips. For example, the controller or control system can alternately shut off power flow to another coupling strip while acquiring network analyzer measurements on that strip. Thus, adjacent coupling strips can maintain some heat on the aircraft surface near the coupling strip undergoing network analyzer measurements.

[0300] In some embodiments, the network analyzer can be configured to operate using a different signal frequency range than the power supply system. For example, the power signal can be provided in the 100-450 MHz range, but the network analyzer can be configured to measure the impedance of the coupling strip using a test signal in the 1-10 MHz range. A low-pass filter can be provided between the network analyzer input / output and the power supply to avoid damage to the network analyzer from the power signal and to enable the impedance measurement of the coupling strip without stopping the heating operation.

[0301] In some embodiments, the controller also uses time-domain reflectometry to perform its functions. Time-domain reflectometry (TDR) is the study of transmission line reflections. It is often used to detect faults in very long or difficult-to-access cables. Its main difference from the previous methods described is its focus on the time domain. This means it can measure the travel time of a signal from the time it reaches the end of a cable or coupling strip until it bounces back to its entry point. It is an effective tool for measuring parameters such as the length and characteristic impedance of a transmission line or coupling strip. TDR is an important complementary tool to frequency-domain analysis because it can derive parameters that are difficult to reverse from a frequency plot.

[0302] FIG. 34 shows an example of a TDR implementation, illustrating how, for example, open circuits, short circuits, and impedance mismatches can be detected using a TDR on a coupling strip attached to an aluminum panel.

[0303] As a result, TDR can be used to characterize and locate discontinuities, faults, or defects in transmission lines, cables, or coupling strips. For example, in a cable of consistent material, the propagation velocity of an electrical signal can be measured. This propagation velocity can be used to measure the distance from the measurement point and any perturbations, faults, termination changes, or modifications can be detected via TDR as a localized change in impedance.

[0304] TDR uses a very fast pulse generator that sends a signal into the system being measured. Key pulse parameters, including the time it takes to transition from low to high voltage, are tailored to the specific system under test and the specific measurement goal to obtain the required data. This pulse is then measured with an oscilloscope. Specialized instruments, such as a combination pulse generator and sampling oscilloscope optimized for periodic measurements, can be used; however, specialized equipment is not necessarily required. The time-domain representation can be reconstructed from the frequency domain. Using an inverse Fourier transform, the output of the network analyzer can be converted into an approximation of the expected time-domain behavior.

[0305] Because TDR allows for the characterization and location of discontinuities in transmission lines, it can be used to detect shorts, opens, delaminations in heating systems (such as cables and coupling strips), and other transmission line damage.

[0306] Figure 35A shows a comparison of two of our transmission lines measured with TDR. After 2 meters, one line has a connector, which appears on the plot as a large change in impedance localized in a small area. The same technique can be used to detect deformations in the transmission line or coupling strip, shorts, and delamination of the transmission line from the bulk medium. In some embodiments, the controller performs automated analysis of the results. With appropriate signal processing and advanced analytical techniques (e.g., leveraging machine learning, computer vision, deep learning, artificial intelligence, and other database techniques), live results can be compared to stored standards to detect, characterize, and quantify changes, and the plots can also be interpreted to determine parameters such as impedance, termination, and length.

[0307] Elements of the heating system, such as cables and coupling strips included in some embodiments, can be shown to have temperature-dependent geometric and material properties. As an example, the geometry of transmission lines and coupling strips can be subject to thermal expansion and contraction. Additionally, it can be shown that the conductivity, permittivity, and permeability of materials included in the construction of coupling strips can change with temperature. The previous section described how faults can be detected by changes in impedance measured at various points in the system. In addition to detecting changes in the physical structure of the coupling strip or bulk medium, the de-icing status of the system can also be assessed. Impedance changes versus temperature can be calculated, simulated, or measured empirically. In some embodiments, the impedance and impedance changes of coupling strips over time can be measured to estimate their temperature, providing the controller with an additional method for performing that function.

[0308] Another useful metric may be the rate of change of the measured impedance. During a phase change, the material (in this case, ice melting into water) continues to absorb energy, but the temperature does not change (in this case, it remains at 0°C until it completely melts). In some embodiments, the controller measures the impedance of the coupling strip and uses this property to help perform its functions, such as determining if de-icing is in progress or complete.

[0309] Detecting damage and changes in bulk media In embodiments where the coupling strip is placed over the bulk medium such that the bulk medium is visible as part of the transmission line geometry (e.g., by placing the coupling strip over an aluminum skin such that the aluminum skin is one of the ground planes for the resulting stripline formed by the combination of the coupling strip and aluminum skin), these methods can be used to detect changes, modifications, and damage to the bulk medium even when the coupling strip itself is unchanged. For structures with adequate coverage of the coupling strip over the bulk medium where these lines are returned to an electrical system such as the heating system described herein, sections of the bulk structure can be analyzed and monitored for possible damage from a centralized measurement point.

[0310] In some embodiments, changes to the structure of the bulk medium can be viewed and analyzed as geometric changes to the transmission line formed by the coupling strip coupled to the bulk medium. For example, a dent may change the shape of the bulk medium, altering the characteristic impedance of the transmission line in the region.

[0311] The systems described herein, when installed on an aircraft's skin, can provide skin and structural damage detection. This damage detection can be performed autonomously through control and sensing circuitry built into the aircraft, or using dedicated diagnostic equipment carried by maintenance personnel to designated locations on the aircraft. Currently, this type of damage is typically detected by visual inspection, a time-consuming and error-prone method. Furthermore, in-flight damage detection is limited to events large enough that the crew can notice them without the aid of a diagnostic system.

[0312] For composite skin aircraft, transmission lines can be embedded in a composite layer of skin material (e.g., utilizing a lightning protection shield and adding conductors in another layer to form embedded microstrips or striplines), allowing for damage detection, including delamination of the composite material.

[0313] In some embodiments, the system may include separate sense lines positioned to detect faults in the coupling strips. For example, the coupling strips may be susceptible to a particular type of fault, i.e., delamination, in which the coupling strip is at least partially peeled off from the bulk media. In some such embodiments, the sense lines may be configured to be more sensitive to particular faults. In some embodiments, the coupling strips in coupling strip 1900 may include sense lines.

[0314] For example, as briefly explained above, Chariarai N , a bonding strip carrying the current used to heat the bulk medium (See Figure 19 and Figures 23-27F) The conductive path of the sense line N , career life Nma or bond strip All A separate conductive pathway configured to sense disturbances in the body. N , which may carry intermittent or continuous current (AC or DC) used to sense faults across the carrier line or coupling strip. The current in the sense line is typically less than the current in the carrier line under normal operating conditions (e.g., no faults). For example, The sense line is , Figure 19 As shown in 1900 Joint Strip can be added to the group The sense lines 3820 can be added on the same layer as the carrier lines of the coupling strip (e.g., conductive path 1904 in FIG. 19) or on a separate layer from the carrier lines 3910. 。

[0315] General More current than normal is drawn by the sense line. NA current sensor that can be configured to detect changes in the flow of electricity in a wire or circuit can be used in the system to determine if current is flowing and thereby detect a correlated delamination. Specifically, the system can perform threshold-based delamination detection. For example, in a properly laminated line, the current measured in the sense line will be relatively low. However, in a (partially) delaminated line, the current will exceed a threshold current value. The threshold value is determined by the presence or absence of a bond strip. P's It can be selected to allow detection of a given peel length (eg, 10 cm) while being high enough to avoid false detections during normal operation.

[0316] Additionally or alternatively, a two-port network analyzer sensor can be used in the system, with the first ground reference port being Career Line and the second ground reference port is connected to the sense line. N The S-parameters (e.g., S21 parameters) of the sensor's two-port network are measured at one or more selected frequencies to identify the sense strip and Sense Line The S21 parameter must be configured to quantify the coupling between the two. Detachment can then be detected when the S21 parameter exceeds a predetermined threshold.

[0317] In some embodiments, the heating system can include any of a variety of self-modifying components that can be used to aid in the detection of system failures, including delamination. In particular, the bonding strip 1900 can be configured to undergo a readily detectable failure configuration when in a specific failure mode. The bonding strip 1900 can be configured so that such a failure configuration is quickly detected and occurs before it causes undesirable failure consequences, such as in the bulk media 1902.

[0318] As an example, the dielectric isolation between the conductive layer 1904 and the conductive shield layer 1906 can be constructed of one or more predetermined materials such that when its temperature exceeds a threshold temperature and begins to melt, the dielectric isolation begins to change shape and lose its insulating properties. For example, when heat accumulates on the bonding strip 1900 from the bulk medium 1902 locally to a delaminated portion of the bonding strip 1900, the delaminated portion of the bonding strip couples the heating signal to the conductive shield layer (instead of the bulk medium 1902), thereby causing the unbonded portion of the bonding strip to self-heat. An altered, e.g., electrically shorted, dielectric isolation between the conductive layer 1904 and the conductive shield layer 1906 results in a dramatic change in the performance and input impedance of the bonding strip, from which delamination can be easily detected using, e.g., a current sensor or an impedance sensor. For example, the sudden change in impedance can be an order of magnitude or more increase or decrease in the impedance of the bonding strip compared to the impedance of the bonding strip during normal (fault-free) operation.

[0319] For example, for de-icing the exterior of an aircraft, heating systems typically operate in the 50-60°C range, so the threshold temperature can be set at a value above the upper end of the normal range but well below harmful temperatures (e.g., fuel tank ignition temperatures), say 130°C. In this example, polysulfide-based materials are an example of a suitable material to use in the construction of the dielectric isolation.

[0320] As another example, the conductive layer 1904 can be constructed of one or more predetermined materials such that as the temperature increases, the conductive layer 1904 loses its conductivity, e.g., degrades to an open state, thereby allowing for direct detection of delamination. In this example, copper, aluminum, and alloys are suitable materials for use in constructing the conductive layer.

[0321] As another example, the bottom dielectric layer may be constructed of one or more predetermined materials whose dielectric constant may change significantly with temperature, resulting in a detectable impedance change that may indicate a fault and allow for accurate temperature measurement. In this example, acrylic adhesives, silicone adhesives, ethylene vinyl acetate adhesives, polysulfide sealants, polyurethane sealants, Mylar, PTFE, FEP, and Kapton are suitable materials for construction of the bottom layer.

[0322] In some embodiments, the conductive layer 1904 can be configured to be less sensitive to certain aspects of the system than others. For example, the conductive layer 1904 can be configured such that the impedance, cross-sectional area, or both of the conductive layer 1904 are relatively independent of temperature. In this way, a fault in the system, such as a delamination that causes a significant impedance change, can be easily distinguished from normal operating fluctuations of the system.

[0323] Specifically, to achieve the desired sensitivity of conductive layer 1904 in these embodiments, different construction materials, different bonding materials and associated bonding methods, different geometric designs such as different cross-sectional dimensions, or different termination configurations may be considered. For example, water-based adhesives exhibit a sharp impedance change near 0°C, while alcohol-based adhesives such as ethylene vinyl acetate (EVA) exhibit a more consistent or stable impedance change. Epoxies also exhibit relatively stable dielectric behavior.

[0324] Frequency domain analysis for detecting mechanical changes in bulk media Impedance changes can also be used to detect mechanical changes (e.g., dents or cracks) in the aircraft skin or other bulk media. For example, impedance changes are detectable following an impact on the structure on or outside the bonding strip. This was demonstrated using an impact test setup. A 1.2 kg indenter was dropped onto a panel from a height of 2.8 m. This was chosen to create a 4 mm indentation 25 mm from the nearest fastener attaching the aircraft skin to a structural element such as a wing rib. The observed changes were small enough not to cause a system malfunction, but large enough to be detected.

[0325] Figure 35B shows the normalized real part of the impedance immediately before and after the impact. "Near Tip," "Near Connector," and "Middle" indicate the effect on the coupling strip at the indicated location. "Between" and "far" indicate the effect between the two branches of the coupling strip and the distance (~18 cm) from the nearest coupling strip. As shown, a jump in impedance is observed after the impact.

[0326] As shown in Figure 35B, a relatively small jump in impedance (approximately 5%) is observed after impact. This is detectable for both impacts on and off the bonding strip. The change in impedance is also noticeable for impacts far from the bonding strip, making it useful for impact detection between tracks, etc. Because the lines cover a large portion of the aircraft's surface, they can be used to monitor the structure and detect mechanical changes (such as dents or cracks).

[0327] Frequency domain analysis for cable fault detection In some embodiments, the frequency domain analysis plots can be used to detect cable faults that may be present in the heating system 100, such as delamination of the bonding strip 1900. They can also be used to detect mechanical changes (such as dents or cracks) in the aircraft skin or other bulk media. In particular, advanced graph analysis techniques, including graph transformation techniques (e.g., Fourier transform) and machine learning techniques (e.g., neural networks), can be used to extract features or characteristics from the frequency response plots and / or data derived from the frequency response plots that can detect the presence of cable faults or mechanical changes in the bulk media. In general, different features or characteristics may be indicative of different types of cable faults and mechanical changes in the bulk media.

[0328] For example, the features or characteristics may include minimum or maximum resistance or theta values, as well as the associated frequency values ​​at which these minimum or maximum values ​​are located. As another example, the features or characteristics may include resonant peak pattern information, including, for example, the dominance of resonant peaks, the inter-peak distance from one another, and the consistency between the inter-peak frequency intervals.

[0329] Fig. 41 43A shows plots of the frequency response of healthy (e.g., defect-free) and defective bonding strips installed on a bulk medium. In this example, a particular type of cable fault, delamination, can be detected based on determining whether the respective values ​​of the resonant peaks, e.g., resonant peak 4310, over a given frequency range are monotonically decreasing or monotonically increasing. As shown in plot 4300, the resonant peak values ​​are monotonically decreasing for a healthy bonding strip. However, as shown in plot 4350, for an unhealthy (e.g., delaminated) bonding strip, the resonant peak values ​​may first decrease, then increase, and then decrease again.

[0330] In some embodiments, faults such as shorts, open circuits, or delaminations in a cable (e.g., a bonding strip) can be detected by comparing the measured impedance versus frequency of a particular cable to data showing the expected pattern of impedance versus frequency for an unfaulted (e.g., healthy) cable. For example, a spectrum analyzer or TDR device can be used to measure the impedance versus frequency or time domain pattern of a particular cable. The measured impedance versus frequency or time domain pattern can be compared to the expected impedance versus frequency or time domain pattern of a similar cable without faults (e.g., as shown in plot 4350). In a frequency domain example, changes in the features or characteristics of the resonant peak pattern of the measured impedance versus frequency pattern can be compared to the expected impedance versus frequency pattern to identify faults in the cable.

[0331] TDR for detecting mechanical changes in bulk media Dents and other mechanical changes in bulk media are localized deformations of the bulk medium and can therefore cause localized changes in the characteristic impedance of a transmission line placed in the bulk medium, making TDR well suited to detecting and locating mechanical changes in bulk media.

[0332] Figure 36 shows examples of TDR for two different bonding strip designs. The red line represents the dented test panel, and the blue line represents the baseline panel. Using TDR, we can see that the impedance changes abruptly along the dented bonding strip, manifesting as impedance fluctuations around the normal value for the undented panel. This information can be used to localize the dent to a specific region of the cable, thus identifying the location of damage in the underlying structure. This data can be difficult to detect using frequency response alone, since the average characteristic impedance along the length of the bonding strip is nearly the same. However, using TDR, localized discontinuities can be identified.

[0333] In one embodiment of a heating system, TDR measurements performed on a bonded strip covering the bulk media, combined with analysis of the resulting data (e.g., using the advanced methods described above), can be used to map the envelope and structure and health of the bulk media, which can be used as a maintenance and service diagnostic tool or as a real-time monitoring tool.

[0334] In embodiments of electric de-icing systems that use coupling strips to heat the bulk medium, multiple coupling strips are powered from the same high-frequency source. In this embodiment, additional cabling can be included to prevent AC power from physically approaching the coupling strip in question. In these embodiments, the fault detection and de-icing evaluation described above are still possible. In fact, a single monitoring system for the AC power source can monitor the performance of all connected coupling strips. However, in other embodiments, additional monitors can be placed at the input of each coupling strip. Each coupling strip can be considered a parallel element, with the additional cabling used as a series element in a network. This network is defined by the geometry and material parameters of its configuration.

[0335] In some embodiments, multiple AC power sources can be combined to power one or more combining strips as described above. As above, this allows a single controller subsystem to detect faults between one or more AC power sources and one or more combining strips. However, separate monitoring of each AC power source can also be performed. This allows the cause of a fault to be isolated to a single system element. In this embodiment, redundant AC power sources can be installed so that the fault detection system can bring the redundant element online to compensate for the fault while completing de-icing.

[0336] Some embodiments of electric de-icing systems may include distributed or in-line circuitry between the AC power source and the combining strips. This circuitry may be passive (including only inductors, capacitors, resistors, and transformers). Alternatively, it may be active (e.g., including transistors, logic gates, or other elements in the case of an active IAN). In embodiments where this circuitry is active, it can be used for fault detection and de-icing evaluation. In embodiments where multiple combining strips are powered from a single or combined AC power source, distributed active circuitry can isolate a fault to a single combining strip element by placing individual monitors on each combining strip element. Furthermore, if additional redundant combining strip elements are installed, the distributed active circuitry can route power to other combining strips to mitigate the fault of a single combining strip and ensure complete de-icing. This distributed circuitry can communicate with the AC power source or any "upstream" circuitry via cabling, known wireless communication protocols, or through manipulation of system voltage, current, or impedance. For example, in one embodiment, this distributed circuitry can use an electrical or electromechanical switch to disconnect any combining strips with impedances outside of their normal range. This disconnection can be detected by an AC power monitoring system, which simultaneously de-energizes the faulty coupling strip to prevent damage to the system. In another embodiment, other sensors (e.g., temperature sensors, ice sensors) can be coordinated with such distribution circuitry to direct power directly to areas with high ice buildup.

[0337] In embodiments where multiple coupling strips are attached to the same bulk medium, a fault in a nearby coupling strip can be detected by sending a signal to a single coupling strip. All coupling strips attached to the same bulk structure may have some degree of electromagnetic coupling. By placing a transmitter on one coupling strip (such as an AC power supply, network analyzer, or TDR) and a receiver, such as an oscilloscope, on another coupling strip, the induced signal can be picked up. This can be used to verify that the coupling is within the expected range. A coupling coefficient outside the expected range may indicate a fault. For example, in one possible embodiment, a poor electrical connection of a coupling strip to the bulk structure can increase coupling to other coupling strips. This can also lead to insufficient heating for de-icing. Monitoring the induced signal on the other coupling strips can detect this error.

[0338] In some embodiments, similar to above, the TDR plot may be used to assist in detecting delamination of the bonding strip by analyzing specific features that are drawn or otherwise extracted from the TDR plot, for example, using graph analysis techniques.

[0339] In addition to detecting defects in the bonding strip or detecting dents in the bulk medium, techniques similar to those described above can be used to detect the presence of various contaminants such as water or ice on the bulk medium, as well as to determine the type of contaminant present on the bulk medium, using either TDR or frequency domain analysis.

[0340] As used herein, the term "electrically connected" includes cases where two electrical components are connected to each other through an object having an electrical function, as opposed to a "direct connection" in which two electrical components are directly coupled to each other (e.g., via a wire or circuit trace without additional components such as a resistor, capacitor, or inductor). Furthermore, a reference to a first component being electrically connected to a particular terminal of a second component is not intended to include an electrical path that passes through the second component itself. For example, a capacitor electrically connected to the gate terminal of a transistor may include cases where the electrical connection passes through another object or component having an electrical function, but does not include cases where the electrical connection passes to the gate of the transistor through another terminal (e.g., source / drain) of the transistor itself.

Claims

1. 1. A system for heating the skin of an aircraft, the system comprising: a series of individual heating elements disposed on the skin of the aircraft and configured to provide locally different power densities; a sensor disposed on the skin at a location corresponding to an area of ​​relatively low temperature within the heating pattern produced by the heating element; a control system connected to the heating element and the sensor, the control system configured to control power supplied to the heating element in response to an output from the sensor; A system comprising:

2. The heating element is a bonding strip including a multi-layer structure extending along a surface of the aircraft skin that forms a power line in combination with the aircraft skin, the multi-layer structure comprising: a first dielectric layer on the aircraft skin; a conductive layer on the first dielectric layer; a second dielectric layer on the conductive layer; and a conductive shield layer on the second dielectric layer; The system of claim 1 , comprising:

3. 2. The system of claim 1, wherein the location includes a cold region on the aircraft skin arranged to maintain a local temperature of the location lower than a temperature of a majority of the aircraft skin with the heating element active.

4. The system of claim 3 , wherein the cold region includes an array of the heating elements that provides less heat to the location than a majority of the aircraft skin.

5. The system of claim 1 , wherein the location includes a cold area on the aircraft skin and is positioned to cause ice to form at the location.

6. The system of claim 5 , wherein the cold region comprises a ridge, an edge, or a wall.

7. The system of claim 1 , wherein the sensor is a temperature sensor or an ice sensor.

8. The system of claim 1 , wherein the location is visible from a window of an aircraft.

9. The control system includes: detecting a characteristic of the aircraft skin at the location based on output from the sensor; comparing the value of the characteristic to a reference characteristic; triggering an indication of a frozen condition in response to determining that the value of the property is indicative of freezing at the location; The system of claim 1 , configured to:

10. a second sensor disposed on the skin of the aircraft at a second location corresponding to a relatively hot area within the heating pattern produced by the heating element; the control system is connected to the second sensor; the control system detects the temperature of the aircraft skin at the second location based on the output from the second sensor, compares the temperature to a reference temperature for the location, and triggers an indication of an overheating condition in response to determining that the temperature is greater than the reference temperature; The system of claim 1 , configured to:

11. The control system includes: detecting a characteristic of the aircraft skin at the location based on output from the sensor; comparing the value of the characteristic to a reference characteristic; The system of claim 1 , configured to provide power to a heating element in response to determining that the value of the property is indicative of freezing at the location.

12. a second sensor disposed on the skin of the aircraft at a second location corresponding to a relatively hot area within the heating pattern produced by the heating element; the control system is connected to the second sensor; the control system detecting the temperature of the aircraft skin at the second location based on an output from the second sensor; Compare that temperature to a reference temperature for that location, The system of claim 1 , configured to reduce power to the heating element in response to determining that the temperature is greater than a reference temperature.

13. The control system includes: measuring the temperature indicated by the sensor over a period of time; by determining that deicing is complete in response to determining that the temperature gradient has remained constant at about zero degrees Celsius for a period of time and then has begun to rise; The system of claim 1 configured to detect a state of de-icing operation.

14. The system of claim 1 , wherein the control system is configured to measure an impedance frequency response of a coupling strip and estimate a temperature of the coupling strip based on the measured impedance frequency response.

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