Normal stress sensor system

Abstract

The invention relates to a normal stress sensor system comprising: at least one normal stress sensor (1) with a force measuring disc (16) with a resonator (13c) having a first natural frequency dependent, preferably at least substantially linearly, on a mechanical normal stress to be detected, wherein the force measuring disc (16) is designed as a disc perpendicular to the longitudinal axis (X), wherein the resonator (13c) is embedded in the force measuring disc (16) in an annular shape around the longitudinal axis (X), and wherein the force measuring disc (16) and the resonator (13c) are designed to be compressible and radially expandable along the longitudinal axis (X); and comprising an antenna (15) that surrounds the edge of the annular resonator (13c) of the force measuring disc (16) in an arcuate manner at least in sections, wherein the antenna (15) is spaced radially apart from the edge of the annular resonator (13c) of the force measuring disc (16) by a distance (14), and wherein the resonator (13c) and the antenna (15) are designed so that normal mechanical stresses (F) acting on the force measuring disc (16) change the natural frequency of the resonator (13c); and comprising at least one control unit (2) designed to excite the resonator (13c) of the normal stress sensor (1) by means of its antenna (15) to oscillate at its natural frequencies, to detect the resonant oscillations of the resonator (13c) of the normal stress sensor (1) by means of its antenna (15), and to determine the mechanical normal stresses (F) from the detected resonant oscillations of the resonator (13c).

Description

[0001] Description

[0002] Normal voltage sensor system

[0003] The present invention relates to a normal voltage sensor system according to claim 1, a normal voltage sensor for use in such a normal voltage sensor system according to claim 14 and a control unit for use in such a normal voltage sensor system according to claim 15.

[0004] To measure mechanical normal and shear stresses, the transducers must be integrated into the component in such a way that they can capture the force flow to be measured. If this force flow is inhomogeneous, flat sensors are usually required. Elastomer-based pressure measuring foils, which are inserted into the component for one measurement at a time, map the distribution of the maximum stresses through color changes. However, this is usually inaccurate, cannot be recorded electronically, and requires the installation, removal, and evaluation of an unused pressure measuring foil for each measurement, making this method of recording normal and shear stresses unattractive.

[0005] With the help of electronic pressure transducers, normal stress distributions can be measured continuously and electronically. For example, a matrix of piezoresistive transducers provides the data for a spatially resolved image. Alternatively, dielectric elastomer sensors (DES) can be used to measure mechanical normal stresses. However, with the exception of dielectric elastomer sensors, such known sensors are only partially suitable for measuring mechanical stresses in elastomeric bodies because the dielectric elastomer sensors cannot track relatively large strains. Furthermore, piezoresistive pressure transducers are expensive, so they are preferably used for discontinuous measurements.

[0006] From DE 10 2020 216 234 A1 a device for detecting mechanical normal stresses in an elastomer component is known, comprising an elastomer component, at least one normal stress sensor, wherein the normal stress sensor has at least one resonator whose natural frequency is dependent, preferably at least substantially linearly, on the mechanical normal stresses to be detected, wherein at least the resonator is embedded in the elastomer component in such a way that mechanical normal stresses acting on the elastomer component can change the natural frequency of the resonator, and at least one control unit which is designed to excite the resonator to oscillate at its natural frequency and to detect its oscillations, wherein the control unit is further designed to determine the mechanical normal stresses of the elastomer component from the detected oscillations of the resonator.

[0007] In other words, a normal force sensor for elastomeric components is described, which consists of a so-called symmetrical microwave stripline designed as a resonator. Along the longitudinal axis, above and below each conductor strip, there is a dielectric, which is covered on its outer surface with a conductive layer and is electrically connected to ground potential. The normal force to be measured compresses the stripline along the longitudinal axis and thus reduces the distance between the centrally arranged conductor strip and the two outer ground surfaces along the longitudinal axis, which changes the wave impedance and return loss of the arrangement. During the force measurement, the stripline is connected to an impedance spectrometer, which evaluates the wave impedance and return loss and calculates the measurement result from this.

[0008] The disadvantage of the device of DE 10 2020 216 234 A1 is that in this way only the average normal stress can be recorded, which acts in the center of the surface of the normal stress sensor.

[0009] From DE 10 2021 206 816 A1 a normal stress sensor system is known having at least one normal stress sensor with at least one first resonator with a first natural frequency which is dependent on a first mechanical normal stress to be detected, with at least one second resonator with a second natural frequency which is dependent on a second mechanical normal stress to be detected, wherein the normal stress sensor is designed to be arranged between two objects in such a way that mechanical normal stresses acting between the objects can change the natural frequencies of the resonators, and with at least one control unit which is designed to excite the resonators of the normal stress sensor to oscillate at their natural frequencies and to detect their oscillations, wherein the control unit is further designed to determine the mechanical normal stresses from the detected oscillations of the resonators.In the standard voltage sensor described in DE 102021 206 816 A1, a resonant conductor structure is located between two conductive surfaces that are electrically at ground potential. The space between the resonator and the ground surfaces is filled with an elastomeric dielectric.

[0010] Applications in which the standard voltage will be measured by sensors will include future braking systems in which the traditional hydraulic components are to be replaced by electromechanical components (dry brakes). During braking, the driver determines the level of braking force by applying force to the brake pedal. Electronic control regulates the force with which a brake disc or brake drum is braked to this target value. Control requires fast and accurate measurement of the currently effective braking force.

[0011] For this purpose, sensors for measuring braking force within electromechanical brakes are currently being developed. These sensors are based on different measuring principles, such as pressure measurement in a compressible container containing a hydraulic medium, or a load cell based on piezoresistive strain gauges. Normal stress sensors or a normal stress sensor system as described in DE 10 2021 206 816 A1 can also be used for this purpose.

[0012] However, the requirements for operating a force sensor or a standard tension sensor within such a brake are extreme. These requirements include the absorption of high forces, high operating temperatures, fast measurement without hysteresis, small installation space, and low cost.

[0013] The described state-of-the-art solutions only partially meet these requirements. For example, a hydraulic sensor has a inherent latency due to the required pressure accumulator, while the load cell has a comparably high height. The force sensor or the microwave-based standard stress sensor described in DE 10 2021 206 816 A1 has a recovery behavior due to the elastomers used, which can lead to hysteresis and aging-related changes in the dielectric constant.

[0014] DE 102022 206 597.2 (unpublished) describes a

[0015] Normal stress sensor system with at least one normal stress sensor with a first carrier with a resonator with a natural frequency which is dependent, preferably at least substantially linearly, on a mechanical normal stress to be detected, with a second carrier which is spaced from the first carrier along a longitudinal axis, and with a connecting element, preferably compressible along the longitudinal axis, which connects the first carrier and the second carrier to one another at a distance from one another along the longitudinal axis, wherein the resonator is spaced from the second carrier along the longitudinal axis by an air gap of the same size and wherein the resonator is designed such that mechanical normal stresses acting on the connecting element change the natural frequencies of the resonator, and with at least one control unit which is designedto excite the resonator of the normal stress sensor to oscillate at its natural frequencies and to detect its oscillations, wherein the control unit is further configured to determine the mechanical normal stresses from the detected oscillations of the resonator.

[0016] DE 102021 206 816 A1 and DE 10 2022 206 597.2 thus propose sensors that can measure forces using high-frequency resonators. Corresponding bench tests have shown that these systems can measure pure normal stresses reproducibly and with high resolution.

[0017] However, the tests have also shown that even small transverse components lead to an asymmetrical load on the sensor and significantly change its frequency-dependent measured value signal (the reflection factor or the transmission factor).

[0018] An object of the present invention is to provide a force sensor or a normal stress sensor which has the above-mentioned

[0019] The goal is to achieve a system that can meet all requirements at all, and at least better than previously known, while simultaneously being tolerant to transverse forces. In particular, all of the above-mentioned requirements should be met together, preferably as effectively as possible. Additionally or alternatively, a robust mechanical design, in particular low mechanical deflection, contactless excitation, high sensitivity, preferably less than 1% of the maximum force, and / or simple assembly should be achieved. At the very least, an alternative to known methods for measuring normal stresses should be created.

[0020] Thus, the invention relates to a normal stress sensor system with at least one normal stress sensor with a force measuring disc with a resonator having a first natural frequency, which is dependent, preferably at least substantially linearly, on a mechanical normal stress to be measured, wherein the force measuring disc is designed as a disc perpendicular to the longitudinal axis, wherein the resonator is embedded in the force measuring disc in a ring shape around the longitudinal axis, and wherein the force measuring disc and the resonator are designed to be compressible and radially expandable along the longitudinal axis, and with an antenna which surrounds the edge of the ring-shaped resonator of the force measuring disc in an arc shape at least in sections, wherein the antenna is spaced radially from the edge of the ring-shaped resonator of the force measuring disc by a distance, and wherein the resonator and the antenna are designed,so that mechanical normal stresses acting on the force measuring disc change the natural frequency of the resonator, and with at least one control unit which is designed

[0021] • to excite the resonator of the normal stress sensor to oscillate at its natural frequencies using its antenna,

[0022] • to detect the resonance vibrations of the resonator of the normal voltage sensor using its antenna, and

[0023] • to determine the mechanical normal stresses from the recorded resonant oscillations of the resonator. The present invention is based on the finding that with such a design of a normal stress sensor, the force to be measured acts on the force measuring disk and compresses it proportional to the force. As a result, the diameter of the force measuring disk increases by the amount of compression multiplied by the transverse contraction factor of the material from which the force measuring disk is made. The length of the embedded resonator increases with the diameter. At the same time, the expansion of the force measuring disk reduces the distance or air gap between the resonator and the antenna, which is preferably arranged on a metallized inner side of a transmission ring. This increases the capacitance per unit length between the resonator and the electrical reference potential.Both force-proportional changes act multiplicatively in the same direction on the natural frequency of the resonator, so that the change in the natural frequency of the resonator can be used to determine the change in the air gap and thus the acting normal force.

[0024] According to one aspect of the invention, the resonator is a component of a microwave stripline. A microwave stripline or stripline (microstrip) refers to a specific class of electrical waveguide for use in the high-frequency range, consisting of one or more thin, conductive strips, preferably applied to a dielectric. This may represent a concrete implementation possibility.

[0025] According to a further aspect of the invention, the resonator is designed as a high-frequency resonator. A high-frequency resonator is understood to be a resonator that can operate in the frequency range of high-frequency oscillations. This refers to frequencies in the range of 1 to 300 GHz. This is advantageous because such high frequencies have correspondingly short wavelengths, allowing the resonator to be realized with comparatively small dimensions. In this way, the comparatively small resonator can also be integrated into a very small standard voltage sensor.

[0026] Another advantage is that, due to the high frequency, no interaction can occur between the electromagnetic field of the resonator and the surrounding material itself, which could have a negative effect on its functionality.

[0027] Another advantage is that, due to its high operating frequency, the resonator can be very sensitive to the measured value signal and thus to normal force or pressure. This can increase measurement sensitivity.

[0028] According to a further aspect of the invention, the resonator has a conductive structure configured to oscillate at a fundamental frequency between 0.1 GHz and 6 GHz. This can represent a concrete advantageous implementation, as previously described for a wider frequency range.

[0029] According to a further aspect of the invention, the resonator is flanked on both sides along its longitudinal axis by conductive surfaces that complement the resonator to form a first microwave stripline. This can represent a concrete implementation option. In this way, the properties and advantages of microwave striplines can also be applied to the resonator.

[0030] According to a further aspect of the invention, the antenna represents a second microwave stripline. Thus, the corresponding properties and advantages can also be applied to the antenna. According to a further aspect of the invention, the conductive surfaces comprise a Ni-Cr alloy, preferably the conductive surfaces are made of this alloy. This aspect of the invention is based on the finding that the temperature-dependent electrical resistance of the conductive surfaces can dampen the resonator's natural frequency. To reduce the influence of temperature on the resistance and thus on the natural frequency, the conductive surfaces can have an extremely low temperature coefficient (e.g., "isoohm", "evanohm").

[0031] According to a further aspect of the invention, the antenna and the resonator of the force measuring disk are arranged directly radially opposite each other. This can improve or strengthen the interaction between the antenna and the resonator, which can lead to a stronger measurement signal and thus to better results in the evaluation of the measurement signal.

[0032] According to a further aspect of the invention, the antenna is arranged on a transmission ring that at least substantially, preferably completely, surrounds the resonator of the force-measuring disk in the circumferential direction. This may represent a concrete implementation possibility.

[0033] According to a further aspect of the invention, the remaining surface on the inside of the transmission ring and its outer surface are metallized and electrically connected to the reference potential of a control unit. This can represent a concrete implementation possibility.

[0034] According to a further aspect of the invention, the gap between the antenna and the resonator of the force-measuring disk is at least partially, preferably completely, filled with an elastic, preferably elastomeric, material that connects the antenna and the resonator. This prevents or at least reduces measurement errors caused by deposits in the gap or air gap. According to a further aspect of the invention, the force-measuring disk is made of a high-strength, preferably ceramic, material. This limits compression (due to the principle) and minimizes influences due to deflection.

[0035] According to a further aspect of the invention, the control unit is designed to computationally compensate for the influence of temperature. This can improve the accuracy of calculating the normal force. The temperature can be detected by a sensor or determined from other measured variables to avoid the additional expense of a temperature sensor.

[0036] The present invention also relates to a standard voltage sensor for use in a standard voltage sensor system as described above. This provides a standard voltage sensor for implementing a standard voltage sensor system as described above and utilizing its properties and advantages.

[0037] The present invention also relates to a control unit for use in a standard voltage sensor system as described above. This allows a control unit to be created to implement the device described above and utilize its properties and advantages. The control unit can also be used universally, e.g., for similar devices or measuring systems, with appropriate adaptation of the software implementation of the previously described functions to the respective application.

[0038] Normal stress sensor systems according to the invention can be used particularly in elastomeric components such as belts, air springs, hoses, straps, bearings, etc., as well as in measurement technology in general. Several exemplary embodiments and further advantages of the invention are explained below in conjunction with the following figures. Therein: Fig. 1 shows a schematic sectional view of a normal stress sensor according to DE 10 2022 206 597.2 along the longitudinal axis;

[0039] Fig. 2a is a schematic sectional view of a normal stress sensor according to the invention along the longitudinal axis;

[0040] Fig. 2b shows a horizontal central section through the normal stress sensor according to the invention of Fig. 2a;

[0041] Fig. 3 is a block diagram of a first evaluation electronics for operating the normal voltage sensor according to the invention; and

[0042] Fig. 4 is a block diagram of a second evaluation electronics for operating the normal voltage sensor according to the invention.

[0043] The description of the above-mentioned Figures 1, 2a, and 2b is given in cylindrical coordinates with a longitudinal axis X, a radial direction R oriented perpendicular to the longitudinal axis X, and a circumferential direction (not shown) running around the longitudinal axis X. The longitudinal axis X, the radial direction R, and the circumferential direction can collectively be referred to as spatial directions or as cylindrical spatial directions.

[0044] A known standard voltage sensor 1 from DE 10 2022 206 597.2, which can also be referred to as a force sensor 1, has a first carrier 10a and a second carrier 10b along the longitudinal axis X, which are spaced apart from one another along the longitudinal axis X. The first carrier 10a is designed as a first carrier layer 10a or as a first carrier film 10a, and the second carrier 10b is designed as a second carrier layer 10b or as a second carrier film 10b. Both carriers 10a, 10b are fixedly connected to one another along the longitudinal axis X by a compressible connecting element 11. Facing one another along the longitudinal axis X are a first electrical insulator 12a in the form of a first electrically insulating film 12a on the first carrier 10a and a second electrical insulator 12b in the form of a second electrically insulating film 12b on the second carrier 10b.

[0045] A first microwave stripline 13 is arranged on the first electrical insulator 12a, which faces the second electrical insulator 12b along the longitudinal axis X. The first microwave stripline 13 has, starting from the first electrical insulator 12a, a first electrically conductive conductor layer 13a in the form of a first ground plane 3a, a first flexible dielectric 13b, and a first resonator 13c, in this order along the longitudinal axis X. The first resonator 13c is formed using printed electrically conductive ink.

[0046] A second microstrip line 15 is arranged opposite the first resonator 13c along the longitudinal axis X, the layout of which is similar to that of the first microstrip line 13. The first resonator 13c and the second resonator 15c are spaced apart from each other along the longitudinal axis X by an air gap 14. The standard voltage sensor 1, together with a control unit (not shown), forms a standard voltage sensor system.

[0047] If one of the two microstrip lines 13, 15 is excited with a high-frequency electrical signal, an electromagnetic field forms between the first and second microstrip lines 13, 15, coupling the two microstrip lines 13, 15 to each other. The strength of this coupling depends on the distance between the microstrip lines 13, 15, in this case, on the height of the air gap 14 between the cover surfaces of the force sensor 1.

[0048] In other words, if the dimension of the air gap 14, as the distance between the second ground plane 15a and the first resonator 13c, is reduced by the applied normal stress F, this affects the natural frequency of the first resonator 13c, i.e., the natural frequency is detuned. This can be detected or recognized by the control unit, and the applied mechanical normal stress F along the longitudinal axis X can be determined from this. This can be done by means of evaluation electronics 2, which can also be referred to as control unit 2, for operating the normal stress sensor 1.

[0049] Thus, the normal force to be measured compresses the compressible connecting element 11 and thereby reduces the distance between the first microstrip line 13 or its first resonator 13c and the opposite second ground plane 15a of the second microwave strip line 15. The variable distance modulates the wave impedance and with it the measurable reflection factor of the force sensor 1.

[0050] For this purpose, the first microstrip line 13 is excited with a high-frequency alternating voltage. The supplied power can be measured, as can the power transferred from the first microwave strip line 13 to the second microwave strip line 15. The ratio of the transferred powers corresponds to the magnitude of the transmission factor between the two microstrip lines 13, 15. This depends on the distance between the microstrip lines 13, 15, which in turn depends on the force to be measured acting on the compressible connecting element 11.

[0051] A disadvantage here, however, is that the normal forces F acting asymmetrically on the second support 10b, which forms the cover surface of the normal stress sensor 1, result in a bending moment B on the connecting element 11, causing the second support 10b to tilt. As a result, the resonators 13c, 15c approach each other at different distances on one side, altering the measured value signal in terms of its frequency and amplitude distribution. The evaluation of this signal is still possible, but involves considerable time (for multiple sampling) and computing power.

[0052] A further disadvantage of the proposed metal body is that the connecting element 11 absorbs the entire force flow and is therefore significantly deformed. When used in a control loop, this application reduces the phase margin of the control system.

[0053] A further disadvantage is that the measured value signals are available as analog voltages, the evaluation of which requires expensive analog-to-digital converters if high resolution is to be achieved. The aforementioned known systems measure the magnitudes of the transfer parameters of the resonators 13c, 15c, which are represented by analog voltages.

[0054] The normal voltage sensor 1 according to the invention of Figures 2a and 2b as well as its first evaluation electronics 2 of Figure 3 can be regarded as a further development of the normal voltage sensor 1 of Figure 1 as well as its evaluation electronics.

[0055] Figures 2a and 2b show the structure of the normal stress sensor 1 according to the invention, the core of which is designed as a thin force measuring disc 16 made of high-strength material in order to limit the (principle-related) compression and to minimize influences due to deflection.

[0056] Embedded on the outer edge of the force-measuring disk 16 is a resonator 13c made of a conductive structure, which can oscillate with high quality at a fundamental frequency defined by the structure between 0.1 GHz and 6 GHz. The resonator 13c is flanked on both sides by conductive surfaces 13d, 13e, which complement the resonator 13c to form a first microwave stripline 13. Concentric with the force-measuring disk 16 is the transmission ring 17, which is arranged such that an air gap 14 exists between the circumference of the force-measuring disk 16 and the inside of the transmission ring 17. On the inside of the transmission ring 17 is an antenna 15 in the form of a second micro-stripline 15, via which the resonator 13c can be excited to oscillate without contact.The remaining surface on the inside of the transmission ring 17 and its outer surface are metallized and electrically connected to the reference potential of an evaluation electronics 2, see Figures 3 and 4.

[0057] The force to be measured acts on the force measuring disk 16 and compresses it proportionally to the force. As a result, its diameter increases by the amount of compression multiplied by the Poisson's factor of the material from which the force measuring disk 16 is made. The length of the embedded resonator 13c increases with the diameter. At the same time, the expansion of the force measuring disk 16 reduces the distance 14 or the air gap 14 between the resonator 13c and the metallized inner surface of the transmission ring 17, thereby increasing the capacitance per unit length between the resonator 13c and the electrical reference potential. Both force-proportional changes have a multiplicative effect in the same direction on the natural frequency of the resonator 13c, so that the change in the natural frequency of the resonator 13c can be used to determine the change in the air gap 14 and thus the acting normal force F.

[0058] Fig. 3 shows a block diagram of a first evaluation electronics 2 for operating the normal voltage sensor 1 according to the invention.

[0059] At the start of the measurement, a computing unit 26 triggers the transmitter stage 20, which then applies a voltage pulse (pulse duration < 100 picoseconds) to the antenna 15, thereby exciting the resonator 13c to oscillate at a first frequency fres, which is linked to the force to be measured. These oscillations are picked up by the antenna 15, amplified by a receiver 21, and fed to a first input of a multiplying mixer 22. The second input of the multiplying mixer 22 receives the signal of a controllable local oscillator 23, which oscillates at a second frequency fosz. The frequency of the local oscillator 23 is set such that, at the first frequency of the resonator 13c in the unloaded state, a low-frequency beat is produced (tare function).

[0060] Mixer 22 delivers an alternating voltage with the difference frequency {fdiff = magnitude (fres - fosz)} between the first frequency fres and the second frequency fosz, which is superimposed by the alternating voltage with the sum frequency {fsum = magnitude (fres + fosz)}. A low-pass filter 24 passes only the low-frequency signal components.

[0061] A downstream detector 25 generates a binary signal at each zero crossing of the filtered signal, from which the computing unit 26 determines the difference frequency by measuring the temporal interval between the zero crossings with an internal binary counter based on a stabilized base 27. Based on the known frequency fosz of the local oscillator 23, the computing unit 26 calculates the signal frequency of the resonator 13c. Using calibration data stored in a read-only memory 28, the computing unit 26 determines the force acting on the force-measuring disk 1 and outputs the value to an external device via an interface 29.

[0062] The force measuring disc 16 is made of high-strength ceramic material into which the resonator 13c and the conductive surfaces 13d, 13e flanking it are embedded, e.g., using LTCC technology (Low-Temperature Co-Fired Ceramics). The temperature-dependent electrical resistance of the conductive surfaces 13d, 13e dampens the natural frequency of the resonator 13c. To reduce the influence of temperature on the resistance and thus on the natural frequency, the conductive surfaces 13d, 13e are made of a Ni-Cr alloy with an extremely low temperature coefficient (e.g., "isoohm," "evanohm").

[0063] In the simplest case, resonator 13c is designed as a ring. However, other structures with high oscillation quality are suitable, such as split rings or hairpin filter structures. The advantage is that these structures generally continue to function if the conductor path is interrupted. Interruptions create two or more substructures that oscillate at different frequencies, with the individual oscillations overlapping. This special property enables easy fault diagnosis.

[0064] The excitation of the resonator 13c is achieved via the antenna 15, to which a pulse generator with so-called "step recovery diodes" is connected (see Lianfeng Zou, Shulabh Gupta, Christophe Caloz, "A Simple Picosecond Pulse Generator Based on a Pair of Step Recovery Diodes", physics-ins-det, Oct. 23, 2016).

[0065] To avoid incorrect measurements due to deposits, the air gap 14 between the force measuring disc 16 and the transmission ring 17 is filled with a soft elastomer (not shown).

[0066] Fig. 4 shows a block diagram of a second evaluation electronics unit 2 for operating the standard voltage sensor 1 according to the invention. The evaluation electronics unit 2 of Fig. 4 is expanded compared to the evaluation electronics unit of Fig. 3 in order to computationally compensate for the influence of temperature. A differentiator 30 forms the time derivative of the output signal of the mixer 22. A downstream detector 31 generates a binary signal at each zero crossing of the derivative, at the positive edge of which the computing unit 26 samples and reads in the amplitude of the filtered signal with the aid of an analog-to-digital converter 32. The read-in values ​​correspond to the relative minima and maxima of the filtered signal. From a series of several extreme values, the computing unit 26 determines the time constant with which the oscillation of the resonator 13c decays and from this, via the resistance of the conductor track, the temperature at the resonator 13c.

[0067] List of reference symbols (part of the description)

[0068] B bending moment

[0069] F Normal force

[0070] R radial direction

[0071] X Longitudinal axis fdiff Difference frequency fosz Second frequency of the controllable local oscillator 23 fres First frequency of the resonator 13c of the first microwave stripline

[0072] 13 fsum sum frequency

[0073] I Normal tension sensor; force sensor

[0074] 10a first carrier; first carrier layer; first carrier film

[0075] 10b second carrier; second carrier layer; second carrier film

[0076] II (compressible) connecting element

[0077] 12a first electrical insulator; first electrically insulating film

[0078] 12b second electrical insulator; second electrically insulating film

[0079] 13 first microwave stripline

[0080] 13a first electrically conductive conductor layer or first ground plane of the first microwave stripline 13

[0081] 13b first dielectric or dielectric of the first microwave stripline 13

[0082] 13c first resonator or resonator of the first microwave stripline 13

[0083] 13d first conductive surface of the first microwave stripline 13

[0084] 13e second conductive surface of the first microwave stripline 13

[0085] 14 Air gap; distance

[0086] 15 second microwave stripline or antenna a second electrically conductive conductor layer or second ground plane of the second microwave stripline 15 b second dielectric or dielectric of the second microwave

[0087] Stripline 15 c second resonator or resonator of the second microwave stripline

[0088] 15

[0089] force measuring disc

[0090] transmission ring

[0091] Evaluation electronics; control unit

[0092] Transmission level

[0093] Recipient

[0094] mixer

[0095] local oscillator

[0096] Low-pass filter

[0097] detector

[0098] Computing unit stabilized base

[0099] Read-only memory

[0100] interface

[0101] Differentiator downstream detector

[0102] Analog-to-digital converter

Claims

Patent claims 1. A normal stress sensor system comprising at least one normal stress sensor (1) with a force measuring disk (16) having a resonator (13c) with a first natural frequency, which is dependent, preferably at least substantially linearly, on a mechanical normal stress to be measured, wherein the force measuring disk (16) is designed as a disk perpendicular to the longitudinal axis (X), wherein the resonator (13c) is embedded in the force measuring disk (16) in a ring shape around the longitudinal axis (X), and wherein the force measuring disk (16) and the resonator (13c) are designed to be compressible and radially expandable along the longitudinal axis (X), and having an antenna (15) which surrounds the edge of the ring-shaped resonator (13c) of the force measuring disk (16) in an arc shape at least in sections, wherein the antenna (15) is radially spaced from the edge of the ring-shaped resonator (13c) of the force measuring disk (16) by a distance (14) spaced, and wherein the first resonator (13c) and the antenna (15) are formed,so that mechanical normal stresses (F) acting on the force measuring disc (16) change the natural frequency of the resonator (13c), and with at least one control unit (2) which is designed to excite the resonator (13c) of the normal stress sensor (1) by means of its antenna (15) to oscillate at its natural frequencies, to detect the resonant oscillations of the resonator (13c) of the normal stress sensor (1) by means of its antenna (15), and, TI to determine the mechanical normal stresses (F) from the recorded resonance vibrations of the resonator (13c).

2. Normal voltage sensor system according to claim 1, wherein the resonator (13c) is part of a microwave stripline (13).

3. Normal voltage sensor system according to claim 1 or 2, wherein the resonator (13c) is designed as a high-frequency resonator (13c).

4. Normal voltage sensor system according to one of the preceding claims, wherein the resonator (13c) has a conductive structure which is designed to oscillate at a fundamental frequency between 0.1 GHz and 6 GHz.

5. Normal voltage sensor system according to one of the preceding claims, wherein the resonator (13c) is flanked along the longitudinal axis (X) on both sides by conductive surfaces (13d, 13e) which complement the resonator (13c) to form a first microwave stripline (13).

6. Normal voltage sensor system according to claim 5, wherein the antenna (15) is a second microwave stripline (15).

7. Normal voltage sensor system according to claim 5 or 6, wherein the conductive surfaces (13d, 13e) comprise, preferably consist of, a Ni-Cr alloy.

8. Normal stress sensor system according to one of the preceding claims, wherein the antenna (15) and the resonator (13c) of the force measuring disc (16) are arranged directly radially opposite one another.

9. Normal stress sensor system according to one of the preceding claims, wherein the antenna (15) is arranged on a transmission ring (17) which surrounds the resonator (13c) of the force measuring disc (16) in the circumferential direction at least substantially, preferably completely.

10. Normal voltage sensor system according to claim 9, wherein the remaining surface on the inside of the transmission ring (17) and its outer surface are metallized and electrically connected to the reference potential of a control unit (2).

11. Normal stress sensor system according to one of the preceding claims, wherein the distance (14) between the antenna (15) and the resonator (13c) of the force measuring disc (16) is at least partially, preferably completely, filled with an elastic, preferably elastomeric, material which connects the antenna (15) and the resonator (13c) to one another.

12. Normal stress sensor system according to one of the preceding claims, wherein the force measuring disc (16) is made of high-strength, preferably ceramic, material.

13. Normal voltage sensor system according to one of the preceding claims, wherein the control unit (2) is designed to computationally compensate for the influence of the temperature.

14. Normal voltage sensor (1) for use in a normal voltage sensor system according to one of claims 1 to 13.

15. Control unit (2) for use in a normal voltage sensor system according to one of claims 1 to 13.

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