Axial and radial suspension for magnetically actuated excitation devices

Abstract

A suspension system for an excitation device. The excitation device includes a piston extending through an opening in a movable housing and generates a vibration force by inducing linear reciprocating motion of the housing relative to the piston. The suspension system includes an axial suspension magnet fixedly coupled to the housing and disposed proximate the opening. The axial suspension magnet is configured to oppose a magnetic field of a permanent magnet fixedly coupled to the piston, such that when a first axial suspension magnet approaches the permanent magnet, the opposing magnetic field dampens motion of the housing relative to the piston. A radial guide bush is disposed within the opening surrounding a periphery of the piston. The radial guide bush is formed of a compressible and flexible material and configured to limit radial motion of the housing relative to the piston.

Description

[Technical Field]

[0001] The present invention relates generally to electromagnetic devices, and more particularly to structures for magnetically actuated excitation devices (e.g., vibration shakers). Summary of the Invention [Means for solving the problem]

[0002] In one embodiment, the present invention provides an excitation device for controllably inducing a force in a structure. The excitation device includes a movable housing, a piston, a permanent magnet, a first axial suspension magnet, and a first radial guide bushing. The movable housing includes a first opening disposed on a first end surface of the movable housing, and the piston extends through the first opening. The exciter is configured to generate a vibration force by controllably inducing linear reciprocating motion of the movable housing relative to the piston. The permanent magnet is fixedly coupled to the piston, and the first axial suspension magnet is fixedly coupled to the movable housing and disposed proximate to the first opening. The first axial suspension magnet is configured to oppose the magnetic field of the permanent magnet, and when the first axial suspension magnet approaches the permanent magnet, the opposing magnetic field damps the motion of the movable housing relative to the piston. The first radial guide bushing is disposed within the first opening of the movable housing and surrounds the piston. The first radial guide bushing is formed of a flexible, compressible material in contact with the piston and is configured to limit movement of the moveable housing relative to the piston.

[0003] In some implementations, the opposing magnetic fields between the permanent magnet and the first axial suspension magnet cause the first axial suspension magnet to apply an axial compressive force to the first radial guide bushing, the axial compressive force on the first radial guide bushing causing a corresponding expansion of the first radial guide bushing in the radial direction, and the expansion of the first radial guide bushing in the radial direction resulting in stiffening of the first radial guide bushing against the circumference of the piston.

[0004] In some implementations, the movable housing includes a second opening in a second end face of the movable housing opposite the first end, and the piston extends through both the first opening and the second opening. In some such implementations, the shaker device includes a second axial suspension magnet disposed in the second opening that is also configured to oppose the magnetic field of the permanent magnet, such that when the second axial suspension magnet approaches the permanent magnet, the opposing magnetic field between the permanent magnet and the second axial suspension magnet damps motion of the movable housing relative to the piston.

[0005] In another implementation, the present invention provides a suspension system for an excitation device that includes a piston extending through an opening in a movable housing and generates a vibration force by inducing linear reciprocating motion of the movable housing relative to the piston. The suspension system includes a first axial suspension magnet fixedly coupled to the movable housing and positioned proximate a first opening in the movable housing. The first axial suspension magnet is configured to oppose a magnetic field of a permanent magnet fixedly coupled to the piston, and when the first axial suspension magnet approaches the permanent magnet, the opposing magnetic field between the first axial suspension magnet and the permanent magnet damps motion of the movable housing relative to the piston.

[0006] In some implementations, the suspension system further includes a radial guide bushing disposed within the first opening of the movable housing and surrounding the piston. The radial guide bushing is configured to limit radial movement of the movable housing relative to the piston. In some implementations where the shaker device includes a second opening and the piston extends through both the first opening and the second opening of the movable housing, the suspension system includes a second axial suspension magnet and / or a second radial guide bushing disposed in the second opening of the movable housing.

[0007] Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. [Brief explanation of the drawings]

[0008] [Figure 1A] 1 is a cross-sectional view of a movable housing of an excitation device (eg, a moving body excitation device). [Figure 1B] FIG. 1B is a perspective view of the excitation device of FIG. 1A. [Figure 2A] 1B is a cross-sectional view of the excitation device of FIG. 1A with a selectively attachable impact hammer attachment component. [Figure 2B] FIG. 2B is a perspective view of the excitation device of FIG. 2A. [Figure 3] FIG. 3 is a block diagram of a control system for the excitation device of FIGS. 1A to 2B. [Figure 4] 1C is a graph of control signals applied by the control system of FIG. 3 to the excitation device of FIGS. 1A and 1B to apply a vibration force to a structure / device under test. [Figure 5] 4 is a graph of the control signals applied by the control system of FIG. 3 to the excitation device of FIGS. 2A and 2B to apply an impact force to a structure / device under test. [Figure 6] 1C is a flow diagram of a method for controllably applying a force to a structure / device under test using the excitation device of FIGS. 1A-2B. [Figure 7] FIG. 3 is a cross-sectional view of the magnetic axial and radial suspension system of the excitation device of FIGS. 1A-2B. [Figure 8A] FIG. 1 is a perspective view of a cylindrical body of an excitation device. [Figure 8B] FIG. 10 is a perspective view of the bobbin of the excitation device. [Figure 8C] 8B positioned within the cylindrical body of FIG. 8A during assembly. FIG. [Figure 8D] FIG. 10 is a perspective view of a mode indicator of the excitation device. [Figure 8E] FIG. 10 is a perspective view of a table assembly of the excitation device. [Figure 8F] FIG. 10 is a perspective view of a bottom support plate assembly of the excitation device. [Figure 8G] FIG. 13 is a perspective view of a radial guide bushing (i.e., neoprene O-ring) of the excitation device. [Figure 8H] FIG. 10 is a perspective view of the housing of the impact hammer attachment component of the excitation device. [Figure 8I] FIG. 10 is a perspective view of the hammer tip and set screw of the impact hammer attachment component of the excitation device. [Figure 8J] 8B is a perspective view of a key-lock tool for selectively coupling and decoupling the top support plate, bottom support plate, and / or impact hammer attachment components to the cylindrical body of FIG. 8A. FIG. [Figure 9] 1B is a flow diagram of a method for assembling the excitation device of FIG. 1A using 3D printing. [Figure 10] 1B is a flow diagram of an alternative method for assembling the excitation device of FIG. 1A by 3D printing components directly onto other components. DETAILED DESCRIPTION OF THE INVENTION

[0009] Before describing any embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways.

[0010] Modal testing is the process of measuring structural frequency response functions (FRFs). The user is responsible for selecting the correct sensors, channel coupling, frequency range, etc. to accurately obtain the system frequency response function. Various embodiments of the present invention recognize that an impact hammer, a single shaker, or multiple shakers can be used to excite a device-under-test (DUT) or structure-under-test (SUT). However, conventional impact hammers often cannot apply enough energy to obtain an appropriate response signal in the frequency range of interest, and the direction of the applied force is difficult to control. Furthermore, integrated shaker devices are limited in the range of frequencies they can provide to the DUT.

[0011] Embodiments of the present invention provide an excitation device that includes an impact hammer and a non-contact magnetic axial suspension, thereby providing multiple excitation modes, precise excitation location, and direction for high-precision measurements, eliminating uncertainties due to equipment swapping. As described in detail below, in some implementations, the magnetic axial suspension is implemented in conjunction with a zero-clearance, low-friction radial suspension. Furthermore, the excitation device provides in-line excitation for impact and / or continuous excitation (e.g., vibration) at points with limited access over a wide frequency range (e.g., 10-10,000 Hz), for example, by selectively switching between these two excitation modes and reconstructing frequency response function (FRF) measurements taking into account the quality achieved in different frequency ranges.

[0012] Various embodiments of the present disclosure recognize that challenges exist in limiting component motion when using a magnetic-based system to induce vibration. Some mechanisms for limiting component motion of an excitation device (e.g., a vibration exciter or “shaker device”) during vibration may include, for example, springs, cushions, or brackets that physically prevent the component from moving beyond a certain displacement. However, embodiments of the present disclosure provide a device that utilizes at least one example of a first permanent ring magnet fixed to a non-magnetic table positioned as the primary driving and inducing component of the excitation device, and a second permanent ring magnet positioned to generate a repulsive force with the first permanent ring magnet to provide a magnetic axial suspension for the excitation device. The second permanent ring magnet of the magnetic axial suspension eliminates the need for various mechanisms for limiting component motion, allowing the excitation device to be easily miniaturized, which reduces manufacturing costs. In some implementations, the non-contact magnetic axial suspension involves a zero-clearance (e.g., “self-aligning”) low-friction radial suspension that provides a ring-shaped contact interface between the table / piston attached to the device under test and the moving body.

[0013] Embodiments of the present invention recognize that various challenges exist in the manufacture and assembly of structural devices using conventional machining methods. For example, the wide variety of material properties of solid structures cannot be achieved using conventional machining methods. Furthermore, conventional machining methods are limited to certain shapes / geometry, such as angled channels (e.g., angled through-holes for wire routing, notches, etc.), because the shapes / geometry cannot be achieved using conventional machining methods or is so difficult and / or expensive to manufacture that it is impractical. Embodiments of the present invention also recognize that conventional manufacturing methods involve tolerance and additional assembly issues.

[0014] Embodiments of the present invention enable the additive manufacturing of fully functional shaker devices that include shapes and geometries that are difficult or impossible to machine using conventional methods. Furthermore, the shaker device and corresponding forces are scalable because the shaker device's components can be additively manufactured, with the exception of the coil, permanent magnets, and radial guide bushings, which results in a reduced overall weight of the device. It also provides customized components (e.g., pistons, bases, etc.) that can be designed for a variety of complex surfaces, threaded inserts, and / or limited space areas. Furthermore, additive manufacturing of shaker devices allows multiple components of the device to be formed as a single complex part, which avoids assembly and tolerance issues and reduces costs associated with waste materials over traditional subtractive manufacturing methods. In some implementations, the use of additive manufacturing enables alternative distribution modes. For example, in some implementations, rather than a manufacturer manufacturing a physical device, a design file may instead be tailored to a specific customer (e.g., rescaling components for a specific application) and digitally transferred to the customer, who then manufactures the vibration excitation device using a 3D printer, thereby avoiding the wait times associated with traditional manufacturing and delivery.

[0015] Additionally, additive manufacturing techniques can be used to realize "differently tuned" vibration exciters using the same internal components (e.g., coils, magnets, O-rings, etc., as described in detail below). Minor scaling adjustments to the axial dimensions of the vibration exciter before printing can be used to adjust the spacing of the same suspension magnet and table magnet; thus, reducing the axial dimension increases the repulsive axial force and increases the stiffness of the vibration exciter, which shifts the natural resonance to higher frequencies and makes the vibration exciter less susceptible to damage at low frequency operation. Conversely, scaling the axial dimension of the vibration exciter decreases the axial repulsive force and therefore the axial stiffness, which increases the force output in the low frequency range.

[0016] 1A and 1B illustrate an example of an excitation device 100 for controllably applying vibrations to a device / structure under test. As shown in FIG. 1B, the excitation device 100 (e.g., a shaker device) includes a movable housing 110 having a bottom support plate 112, a top support plate 114, a cylindrical body 116, and a mode indicator 118. As shown in FIG. 1A, the top support plate 114 and the cylindrical body 116 are formed with counter-engaging helical structures such that the top support plate 114 is selectively coupleable to the cylindrical body 116 by threading at a first end of the cylindrical body 116. Similarly, the bottom support plate 112 and the cylindrical body 116 are also formed with counter-engaging helical structures such that the bottom support plate 112 is selectively coupleable to the cylindrical body 116 by threading at a second end of the cylindrical body 116.

[0017] The movable housing 110 is positioned to partially surround a non-magnetic table 120 (e.g., a piston). The bottom support plate 112 and the top support plate 114 each include an opening positioned to allow a respective end of the non-magnetic table 120 to extend from the movable housing 110. Additionally, a mode indicator 118 is coupled to the cylindrical body 116. Additionally, a first end of each end of the non-magnetic table 120 is coupled to a base 170 that is coupleable to a device / structure under test. The base 170 holds the non-magnetic table fixedly relative to the device / structure under test, and, as described in detail below, movement of the movable housing 110 relative to the non-magnetic table 120 applies a force to the device / structure under test.

[0018] Radial guide bushings 140 are disposed in both openings of the movable housing 110. The radial guide bushings 140 are coupled to the movable housing 110. For example, a first radial guide bushing 140 is coupled to the bottom support plate 112 of the movable housing 110 adjacent to a first end of the non-magnetic table 120. Similarly, a second radial guide bushing 140 is coupled to the top support plate 114 adjacent to a second end of the non-magnetic table 120. The radial guide bushings 140 each include a circular opening that surrounds the non-magnetic table 120 and guides the movement of the movable housing 110 relative to the non-magnetic table 120. For example, the radial guide bushings 140 align the movement of the movable housing 110 relative to the non-magnetic table 120. In some implementations, the radial guide bushing 140 is formed of a neoprene material (e.g., a neoprene O-ring) and maintains contact with the non-magnetic table 120 during operation of the excitation device 100 as the movable housing 110 moves relative to the non-magnetic table 120.

[0019] The radial guide bushing 140 acts as a radial suspension for the excitation device 100 and is constructed from a flexible material with a low coefficient of friction between the table / piston 120 and the radial guide bushing 140. In some implementations, the compressible material of the radial guide bushing 140 causes the excitation device 100 to eliminate clearance between the radial guide bushing 140 and the table / piston 120 when the excitation device 100 is assembled. For example, in some implementations, upon final assembly of the excitation device 100, the radial guide bushing 140 is compressed axially between the axial suspension ring magnet 150 and the support plate 112 / 114. This axial compression causes the radial guide bushing 140 to expand in the radial direction, closing any gap that may exist between the radial guide bushing 140 and the table / piston 120.

[0020] Additionally, the axial magnetic force applied to the axially suspended ring magnet 150 further contributes to an axial compressive force applied to the radial guide bushings 140 at both the top and bottom of the excitation device 100. This results in a radial suspension that is "self-adjusting," in that as the permanent ring magnet 130 of the table / piston 120 approaches the axially suspended ring magnets 150 at either end of the excitation device 100, the axially suspended ring magnets 150 provide an opposing magnetic force that further compresses the radial guide bushings 140. Thus, as the movable housing 110 approaches either end of the table / piston 120, the corresponding radial guide bushings 140 expand further radially, increasing the degree of radial stiffness between the movable housing 110 and the table / piston 120. This increased stiffness of the radial suspension further limits rocking of the table / piston 120 and, in some implementations, can result in a "zero play" radial condition even under high load operation and / or compensate for wear at the contact interface between the radial guide bushing 140 and the table / piston 120.

[0021] In some implementations, the radial guide bushing 140 is further configured to provide limited surface area contact between the radial guide bushing 140 and the table / piston 120 (e.g., an idealized "line contact"). The reduced contact area similarly reduces axial friction. In some implementations, the radial guide bushing 140 is fabricated from a neoprene material to balance radial flexibility and the axial coefficient of friction. In some implementations, silicone lubrication may be added between the table / piston 120 and the radial guide bushing 140 to further reduce friction between the components.

[0022] An axially suspended ring magnet 150 is also positioned in an opening in the bottom support plate 112, and a second axially suspended ring magnet is similarly positioned in an opening in the top support plate 114. In some implementations, the axially suspended ring magnet 150 is coupled to the bottom support plate 112 of the movable housing 110 and surrounds the non-magnetic table 120. As described in more detail below, the permanent ring magnet 130 is coupled to the non-magnetic table 120 to drive the movement of the movable housing 110, and the axially suspended ring magnet 150 damps the movement of the movable housing 110 relative to the non-magnetic table 120 by providing an opposing magnetic force when the permanent ring magnet 130 approaches the axially suspended ring magnet 150. The axially suspended ring magnet 150 also limits the distance the non-magnetic table 120 extends from the movable housing 110, preventing the portion of the non-magnetic table 120 to which the permanent ring magnet 130 is attached from extending outside the movable housing 110. For example, the poles of the axially suspended ring magnet 150 are oriented to face like poles of the permanent ring magnet 130 fixed to the non-magnetic table 120, which creates a repulsive force that suspends the non-magnetic table 120 and prevents ejection of the non-magnetic table 120 from the movable housing 110. In some implementations, both the axially suspended ring magnet 150 and the permanent ring magnet 130 are permanent ring magnets constructed of neodymium material.

[0023] A non-magnetic bobbin 160 is disposed within the movable housing 110 and at least partially surrounds the non-magnetic table 120 and the permanent ring magnet 130 attached thereto. The non-magnetic bobbin 160 is coupled to the cylindrical body 116 of the movable housing 110. A coil 165 is formed around the non-magnetic bobbin 160. In the example of FIG. 1A , the coil 165 includes at least two opposing windings. The winding type and geometry of the coil 165 are configured to produce comparable parameters (e.g., inductance, Q factor, insulation strength, and desired magnetic field strength) for the opposing windings. The coil 165 is formed from a conductive material (e.g., copper wire), and when a current is controllably applied to the coil 165 (as described in further detail below), the coil 165 operates as an electromagnet that produces a controllable magnetic field. A controllable magnetic field is applied to the permanent ring magnet 130, selectively causing movement of the movable housing 110 relative to the permanent ring magnet 130 (and the non-magnetic table 120 to which the permanent ring magnet 130 is coupled) by controllably applying a magnetic field that attracts and repels the permanent ring magnet 130. Thus, the movable housing 110 controllably moves up and down relative to the non-magnetic table 120 by controlling the current applied to the coil 165.

[0024] 1A , the mode indicator 118 is disposed between the cylindrical body 116 and the top support plate 114. In some implementations, the mode indicator 118 is a plastic ring body having one or more light-emitting diodes disposed therein to controllably illuminate the mode indicator 118. In some implementations, the mode indicator 118 is coupled to the cylindrical body 116 of the movable housing 110. In other implementations, the mode indicator 118 is coupled to the top support plate 114 of the movable housing 110. In still other implementations, the mode indicator 118 is a separate component that is held in place between the top support plate 114 and the cylindrical body 116 of the movable housing 110 when the top support plate 114 is selectively coupled to the cylindrical body 116 by the action of a screw.

[0025] In the example of FIG. 1A, the mode indicator 118 indicates the operating mode of the excitation device. The mode indicator 118 may include one or more light-emitting diodes (LEDs) that can change color to indicate the operating mode. Additionally, the mode indicator 118 may continuously illuminate or flash (e.g., power off and on) while the excitation device is operating. In the example of FIG. 1A, the mode indicator 118 may be controlled based on an electrical signal input (e.g., a control signal from a controller, a current in the coil 165, etc.) received by the excitation device.

[0026] As described in more detail below, the bottom support plate 112, the top support plate 114, the cylindrical body 116, and / or the mode indicator 118 of the moveable housing 110 may be manufactured by additive manufacturing (e.g., three-dimensional (3D) printing). For example, the bottom support plate 112 and the top support plate 114 may be constructed of composite carbon fiber polylactic acid (PLA), the cylindrical body 116 may be constructed of composite iron PLA, and the mode indicator 118 may be constructed of PLA.

[0027] In some implementations, the non-magnetic table 120 may be constructed of stainless steel. In some implementations, the non-magnetic table 120 and / or the base 170 may be manufactured by additive manufacturing (e.g., 3D printing). In this example, the non-magnetic table 120 and the base 170 may be constructed of composite carbon fiber polylactic acid (PLA). Furthermore, the base 170 may have various shapes suitable for applying the force of the excitation device to the device / structure under test (e.g., a wedge for an inclined surface and / or a rounded adapter for a curved surface). In some implementations, the non-magnetic table 120 may include one or more notches configured to receive a C-shaped washer clip as a mechanism for securing the permanent ring magnet 130 to the non-magnetic table 120.

[0028] 2A and 2B illustrate an example of an excitation device 100 including an impact hammer attachment component 200 configured to controllably apply an impact force in addition to (or instead of) a vibration force to a device / structure under test. As described above, the top support plate 114 of the movable housing 110 in the example of FIG. 1A is selectively coupleable to the cylindrical body 116 of the movable housing 110. Thus, in some implementations, the top support plate 114 can be removed from the cylindrical body 116 and replaced with the impact hammer attachment component 200. As shown in FIG. 2A , in this example, the impact hammer attachment component 200 includes a helical structure similar to the helical structure of the top support plate 114 and is thus selectively engageable with the cylindrical body 116 by thread action. As shown in FIG. 2A , the impact hammer attachment component 200 includes a housing 202, a set screw 210, and a hammer tip 212 coupled to the set screw 210. 2A , a set screw 210 is disposed in the opening of the housing 202 and coupled to the housing 202 of the impact hammer attachment component 200. The set screw 210 is positioned so as to align with the non-magnetic table 120. The set screw 210 includes a hammer tip 212. The hammer tip 212 is secured to the end of the set screw 210 and is positioned to contact the second end (e.g., the top end) of the non-magnetic table 120 when the first end of the non-magnetic table 120 is coupled to the base 170, as described above. For example, instead of imparting a vibration force by applying an alternating current to the coil 165, the movable housing 110 is configured to impart an impact force to the device / structure under test while the impact hammer attachment component 200 is coupled to the movable housing 110 by applying a first control signal / current to the coil that causes the movable housing 110 to move upward and away from the surface of the device / structure under test. This is followed by applying an opposite current to the coil 165, causing the movable housing 110 to move rapidly in the opposite / downward direction relative to the surface of the device / structure under test.The rapid downward movement causes the hammer tip 212 to contact the edge of the non-magnetic table 120, thereby applying an impact force through the non-magnetic table 120 to the device / structure under test.

[0029] The example in FIG. 2A is just one example of an implementation configured to apply an impact force. Other configurations for generating an impact force between the non-magnetic table 120 and either the movable housing 110 or the impact hammer attachment component 200 are possible. For example, in some implementations, the hammer tip 210 may be attached to the distal end of the non-magnetic table 120 and configured to impact the surface of the impact hammer attachment component 200 and / or another top support plate. In other implementations, a structure / component of the non-magnetic table 120 may be configured to impact a structure / component of the movable housing. For example, the device may be configured such that the permanent ring magnet 130 is aligned along a vertical axis with a surface, protrusion, or top plate of the movable housing 110, thereby generating an impact force by applying a magnetic force that causes the surface of the permanent ring magnet 130 to impact an opposing surface / structure of the movable housing 110.

[0030] Furthermore, in some implementations, the device is configured so that elastic deformation of the impact hammer tip 212 does not corrupt excitation measurements when used for frequency response function (FRF) testing. In some implementations, a load cell is attached between the lower end of the non-magnetic table 120 and the base 170 (i.e., downstream from the impact tip). Thus, the load cell can accurately measure the force applied to the structure / device under test and adjust the applied magnetic force to the target force. In this way, measurement uncertainties due to elastic deformation of the hammer tip 212 are reduced or avoided altogether.

[0031] 2A , the radial guide bushing 140 is disposed in an opening of the housing 202 of the impact hammer accessory component 200. The radial guide bushing 140 is coupled to the housing 202 of the impact hammer accessory component 200. The radial guide bushing 140 surrounds the non-magnetic table 120 and guides the movement of the movable housing 110 and the housing 202 relative to the non-magnetic table 120. Furthermore, the axial suspension ring magnet 150 is disposed in an opening of the housing 202 of the impact hammer accessory component 200. The axial suspension ring magnet 150 is coupled to the housing 202 of the impact hammer accessory component 200.

[0032] The set screw 210 is formed as a cylindrical body having a helical structure on its outer surface, and the housing 202 includes an opening having an oppositely formed helical structure for receiving and engaging the set screw 210 by threading. In this manner, the set screw 210 can be selectively coupled and uncoupled from the housing 202. In some implementations, this selective coupling allows the set screw 210 and hammer tip 212 to be removed and replaced if the hammer tip 212 is damaged. Alternatively, in some implementations, multiple set screws 210 may be provided with different types of hammer tips 212 (materials of different hardness), so that the hammer tips 212 are selectively interchangeable to provide hammer tips 212 suitable for particular testing protocols.

[0033] In some implementations (e.g., as described in more detail below), the impact hammer attachment component 200 may be manufactured by additive manufacturing (e.g., 3D printing). In some such implementations, the impact hammer attachment component 200 may be constructed from composite carbon fiber PLA. Similarly, in some implementations, the set screw 210 may be manufactured by additive manufacturing (e.g., 3D printing) and may be constructed from composite carbon fiber PLA. Additionally, the hammer tip 212 may be manufactured and constructed from a material with respect to the material's ability to resist permanent indentation (i.e., material hardness). In some implementations, the hammer tip 212 may be manufactured by additive manufacturing and may be constructed from PLA, composite iron PLA, and / or composite carbon fiber PLA. In other implementations, the hammer tip 212 may be constructed from stainless steel.

[0034] 3 shows the control system of the excitation device 100. The excitation device 100 is operated by a controller 301 to apply a force to the device / structure under test, which can result in various types and scalable forces based on the input signal. Furthermore, it results in consistent, repeatable, and coherent measurements without experimental uncertainties due to device alternation.

[0035] 3, the controller 301 includes an electronic processor 303 and a non-transitory computer-readable memory 305. The memory 305 stores data and instructions that, when executed by the electronic processor 303, provide various functions of the controller 301, including, for example, some or all of the functions described herein. The controller 301 is communicatively coupled to the excitation device 100.

[0036] In addition to storing computer-executable instructions, in some implementations, the memory 305 is also configured to store additional information regarding the excitation device 100, the top support plate 114, and / or the impact hammer attachment component 200 of the excitation device 100. For example, the memory 305 may be configured to store component information (e.g., location, LED functions, etc.) and performance information (e.g., operating frequency, component constraints, goals / limits, etc.). The configuration shown in FIG. 3 provides only one example of the components and connections of the excitation device 100. However, these components and connections may be configured in other ways and may include other components instead of or in addition to the components shown in the example of FIG. 3.

[0037] In some implementations, the controller 301 is communicatively coupled to the coil 165 of the excitation device 100 and configured to provide control signals for operating the excitation device 100. For example, in some implementations, the controller 301 may be configured to send control signals to the coil 165 in the form of a current that causes the coil 165 to generate a corresponding magnetic field that interacts with the magnetic field of the permanent ring magnet 130 of the excitation device 100, which generates movement within the movable housing 110 of the excitation device 100 relative to the non-magnetic table 120. In this example, the controller 301 is configured to modify (e.g., alternate frequency, modify amplitude, etc.) the control signal sent to the coil 165 to generate a force to apply to a device / structure under test coupled to the excitation device 100.

[0038] 4 and 5 show example control signals that may be applied by the controller 301 to the coil 165 to cause the excitation device 100 to generate a vibration force and an impact force, respectively. As described above, the excitation device 100 is configured to induce a vibration force in the device / structure under test by generating a reciprocating motion of the movable housing 110 relative to the non-magnetic table 120. In some implementations, this is achieved by the controller 301 applying an alternating current to the coil 165, as shown in FIG. 4, for example. The frequency of the induced vibration can be adjusted by adjusting the frequency of the alternating current applied to the coil 165. Also, as described above, in some implementations, the coil 165 includes two coils configured oppositely. Thus, applying the same alternating current control signal to the coil 165 causes movement in a first direction by generating a magnetic field in the first coil that attracts the permanent magnet 130 coupled to the non-magnetic table, while generating a magnetic field in the second coil that repels the permanent magnet 130.

[0039] To induce an impact force on the device / structure under test, the applied magnetic field must be configured to raise the movable housing 110 relative to the surface of the device / structure under test and then lower the movable housing 110 toward the surface of the device / structure under test at a relatively high speed. This may be achieved by applying a control signal to the coil 165, as shown in FIG. 5 . A magnetic field induced by a slowly rising current causes the movable housing 110 to move upward, while a magnetic field induced by a relatively high negative slope portion of the control signal causes relatively high speed movement in the opposite direction. This relatively high speed downward movement of the movable housing 110 causes the hammer tip 212 to impact the top edge of the non-magnetic table 120 and apply an impact force to the device / structure under test via the non-magnetic table 120. In some implementations, the excitation device 100 may be configured to apply only an impact force when equipped with the impact hammer attachment component 200 and only a vibration force when equipped with the top support plate 114. In other implementations, the excitation device 100 may be configured to selectively apply both impact and vibration forces when equipped with an impact hammer accessory component 200 .

[0040] 6 shows an example of a method implemented by the controller 301 to operate the excitation device 100. In some implementations, the controller 301 determines whether the excitation device includes an attachment component (step 402). In the example of FIG. 6, the controller 301 determines whether the excitation device 100 includes an impact hammer attachment component 200. For example, the electronic processor 303 receives an input from a user interface of the controller 301 indicating whether the excitation device 100 includes the impact hammer attachment component 200 or the top support plate 114. In other implementations, the excitation device 100 is configured with circuitry that automatically determines whether the impact hammer attachment component 200, the top support plate 114, or another attachment is coupled to the movable housing 110.

[0041] If the controller 301 determines that the excitation device 100 does not include the impact hammer attachment component 200 (step 402, “No” branch), the controller 301 generates a control signal for the excitation device 100 to apply a vibration force to the device / structure under test (e.g., the control signal of FIG. 4 ). However, if the controller 301 determines that the excitation device 100 includes the impact hammer attachment component 200 (step 402, “Yes” branch), the controller 301 generates a control signal for the excitation device 100 to apply an impact force to the device / structure under test (e.g., the control signal of FIG. 5 ). As described above, in some implementations, the excitation device 100 may be configured to selectively provide an impact force and a vibration force when equipped with the impact hammer attachment component 200. Thus, in some implementations, the controller 301 is configured to transmit a control signal for either an impact force or a vibration force based on a user selection or according to a predetermined test protocol in response to determining that the impact hammer attachment component 200 is coupled to the movable housing 110.

[0042] The controller 301 generates a control signal for applying an applicable force to the device / structure under test (step 404) and sends the control signal to the excitation device 100. In some implementations, the controller 301 may be configured to apply the control signal to the excitation device 100 as a current signal applied to the coil 165 to controllably adjust the magnetic field applied by the coil 165. In some implementations, the controller 301 utilizes the electronic processor 303 and instructions / settings stored in the memory 305 to generate the control signal for the excitation device 100. For example, the controller 301 generates an electrical signal having amplitude, frequency, and waveform characteristics. In some implementations, the controller 301 is configured to adjust the signal characteristics according to a test protocol defined by a user. In some implementations, the controller 301 may include one or more signal generators, such as, for example, a function generator, an arbitrary waveform generator, a frequency generator, etc.

[0043] The control signal generated by the controller 301 is then transmitted to the excitation device 100 (step 406). In some implementations, as described above, the control signal is transmitted to the excitation device 100 as an electric current applied to the coil 165 of the non-magnetic bobbin 160 of the excitation device 100. The electric signal passes through opposing windings of the coil 165 of the non-magnetic bobbin 160, generating a magnetic field in response to the electric signal. The coil 165 and the non-magnetic bobbin 160 are electromagnets (e.g., solenoids), which generate an induced magnetic field centered at the center of the non-magnetic bobbin 160 and / or coil 165 in response to an electric signal (e.g., electric current) passing through the wire of the coil 165. Furthermore, the controller 301 may modify the characteristics of the electric signal to affect the induced magnetic field.

[0044] 6 , the base 170 and non-magnetic table 120 of the excitation device 100 apply the force of the moveable housing 110 and / or the impact hammer attachment component 200 to the device / structure under test. For example, the non-magnetic table 120 of the excitation device 100 directs the movement of the moveable housing 110 toward the base 170, which is coupled to the device / structure under test. The movement of the moveable housing 110 corresponds to the interaction of the induced magnetic field of the coil 165 of the non-magnetic bobbin 160 with the magnetic field of the permanent ring magnet 130, which generates repulsive and attractive forces that cause the non-magnetic table 120 to vibrate continuously. In one scenario, the controller 301 sends a control signal (e.g., current) to the excitation device 100 having a waveform of a set frequency and variable polarity that induces an alternating magnetic field when passing through the coil 165 of the moveable housing 110 that interacts with the permanent ring magnet 130 of the non-magnetic table 120. In this scenario, the induced magnetic field of the coil 165 causes the movable housing 110 to move linearly (e.g., up and down) relative to the non-magnetic table with respect to the control signal. Thus, the linear movement of the movable housing 110 of the excitation device 100 induces continuous vibrations in the device under test coupled to the non-magnetic table 120 via the base 170.

[0045] In some implementations, the base 170 of the excitation device 100 and the non-magnetic table 120 apply the force of the movable housing 110 and / or the impact hammer attachment component 200 to the device / structure under test. Movement of the movable housing 110 corresponds to the interaction of the induced magnetic field of the coil 165 of the non-magnetic bobbin 160 and the magnetic field of the permanent ring magnet 130 to bring the hammer tip 212 of the impact hammer attachment component 200 into contact with the second end of the non-magnetic table 120 coupled to the device / structure under test. Thus, a force (e.g., an impact force) corresponds to contact between the second end of the non-magnetic table 120 and the hammer tip 212 of the impact hammer attachment component 200 directed toward the device / structure under test. In some implementations, the force directed toward the device / structure under test is measured using a load cell (force transducer) attached between the first end of the non-magnetic table 120 and the base 170.

[0046] 4 example, the above methodologies may be used alone or in combination to utilize the non-magnetic table 120 to apply the forces of the moveable housing 110 of the excitation device 100 and the impact hammer attachment component 200 to the device / structure under test. Various embodiments of the present invention provide a controllable excitation mechanism that provides the functionality of a modal hammer and an integrated shaker within a single excitation device. As a result, the excitation device may eliminate the need for multi-excitation configurations and provide accurate and repeatable results in impact testing.

[0047] In some implementations, the controller 301 also provides a control input to the mode indicator 118 of the excitation device 100 to indicate the operating mode of the excitation device 100 (step 408). In some implementations, the controller 301 is configured to provide a binary (i.e., on / off) signal to the mode indicator 118 to indicate only whether the excitation device 100 is operating or not (e.g., turning on an LED light of the mode indicator 118 when (a) a control signal current is applied to the coil 165 and / or (b) the excitation device 100 is communicatively coupled to the controller 301). In other implementations, the controller 301 may be configured to operate the mode indicator 118 to convey other information including, for example, (1) the current operating mode (e.g., vibration or shock), (2) active / inactive status, (3) an error indication, and / or (4) the location / grouping of multiple excitation devices. In some implementations, the controller 301 and the mode indicator 118 are configured to utilize various functions of the LED of the mode indicator 118, such as illumination, illumination intensity, flashing, different colors, etc., to indicate the state of the excitation device 100. For example, the mode indicator 118 may illuminate at a first predetermined intensity and / or a first color when the excitation device is providing an impact force, and illuminate at a second, different predetermined intensity and / or a second color when the excitation device 100 is providing a vibration force.

[0048] 3 is operable to apply a control signal (e.g., a current) to the coil 165 of the excitation device 100 to generate a magnetic field. This controllable magnetic field interacts with a permanent ring magnet 130 coupled to the non-magnetic table 120 to cause movement of the moveable housing 110 relative to the non-magnetic table 120. In some implementations, axial and radial suspensions are incorporated into the excitation device 100 to damp the linear movement of the moveable housing 110 and / or limit the movement of the moveable housing 110 to a defined range. FIG. 7 illustrates the magnetic axial and radial suspensions of the excitation device 100. The axial and radial suspension components of FIG. 7 are also shown in the examples of FIGS. 1A and 2A above, but are shown in more detail in FIG. 7 for clarity.

[0049] 7, the axial and radial suspension of the excitation device 100 includes a permanent ring magnet 130, a radial guide bush 140, and an axial suspension ring magnet 150. The permanent ring magnet 130 is fixedly coupled to the non-magnetic table 120. The permanent ring magnet 130 also includes at least one permanent magnet. For example, the permanent ring magnet 130 of the magnetic axial suspension may be an annular ring magnet and may be axially magnetized.

[0050] The magnetic axial suspension of the excitation device 100 includes at least one example of an axially suspended ring magnet 150. The axially suspended ring magnet 150 is positioned to surround the non-magnetic table 120 (e.g., a piston). The axial and radial suspension of the excitation device 100 also includes at least one example of a radial guide bushing 140. The radial guide bushing 140 is also positioned to surround the non-magnetic table 120 (e.g., a piston). The radial guide bushing 140 guides the movement of the non-magnetic table 120 (i.e., aligns the movement of the non-magnetic table 120 with the opening in the movable housing 110). As mentioned above, in some implementations, the opening in the radial guide bushing 140 is designed to provide zero clearance between the radial guide bushing 140 and the non-magnetic table 120 (i.e., the radial guide bushing 140 is in contact with the non-magnetic table 120 around the entire periphery of the non-magnetic table 120). Additionally, in some implementations, the structure of the movable housing 110 provides an axial "preload" compression of the radial guide bushing 140, thereby causing the radial guide bushing 140 to expand radially.

[0051] In this example, the magnetic axial suspension of the excitation device 100 includes a radial guide bushing 140 and an axial suspension ring magnet 150 disposed at each end of the movable housing 110. Accordingly, in FIG. 7, the radial guide bushing 140 and the axial suspension ring magnet 150 disposed at the bottom of the movable housing 110 (i.e., near the opening in the bottom support plate 112) are labeled as radial guide bushing 140-1 and axial suspension ring magnet 150-1, respectively. Similarly, the radial guide bushing 140 and the axial suspension ring magnet 150 disposed at the top of the movable housing 110 (i.e., either near the opening in the top support plate 114 or near the opening in the housing 202 of the impact hammer accessory component 200) are labeled as radial guide bushing 140-2 and axial suspension ring magnet 150-2, respectively. The ring magnets 130 and 150 have two magnetic poles. In the example of Figure 7, the north magnetic pole is indicated by the letter A and the south magnetic pole is indicated by the letter B. For example, the north magnetic pole of the permanent ring magnet 130 is labeled 130A in Figure 7, and the south magnetic pole of the permanent ring magnet 130 is labeled 130B in Figure 7.

[0052] 7 is provided by the relative arrangement of the magnetic poles of the lower axially suspended ring magnet 150-1, the upper axially suspended ring magnet 150-2, and the permanent ring magnet 130. In particular, the south pole 150-1B of the lower axially suspended ring magnet 150-1 is configured to face the south pole 130B of the permanent ring magnet 130, so that the magnetic fields of the permanent ring magnet 130 and the axially suspended ring magnet 150-1 interact to generate a repulsive force. This repulsive force damps the motion of the movable housing 110 as the lower axially suspended ring magnet 150-1 approaches the permanent ring magnet 130 and also limits the distance that the first end of the non-magnetic table 120 can extend relative to the lower axially suspended ring magnet 150-1. Similarly, the north pole 150-2A of the axially suspended ring magnet 150-2 is configured to face the north pole 130A of the permanent ring magnet 130, so that the magnetic fields of the permanent ring magnet 130 and the upper axially suspended ring magnet 150-2 interact to generate a repulsive force. This repulsive force damps the motion of the movable housing 110 as the upper axially suspended ring magnet 150-2 approaches the permanent ring magnet 130 and also limits the distance that the second end of the non-magnetic table 120 can extend relative to the upper axially suspended ring magnet 150-2. The configuration of the axially suspended ring magnets 150-2, 150-1 results in a stable equilibrium position of the permanent ring magnet 130 at the center of the bobbin.

[0053] Furthermore, in some implementations, the axial and radial suspension systems are configured such that operation of the magnetic axial suspension results in further axial compression (and, in turn, corresponding radial expansion) of the radial guide bushings 140-1, 140-2. In particular, as the permanent ring magnet 130 approaches the axially suspended ring magnet 150-2, the opposing magnetic forces between the permanent ring magnet 130 and the axially suspended ring magnet 150-2 cause the axially suspended ring magnet 150-2 to apply a large axial compressive force to the radial guide bushing 140-2, thereby increasing the stiffness of the radial guide bushing 140-2 relative to the non-magnetic table 120. Conversely, when the permanent ring magnet 130 approaches the axially suspended ring magnet 150-1, the opposing magnetic forces between the permanent ring magnet 130 and the axially suspended ring magnet 150-1 cause the axially suspended ring magnet 150-1 to apply a large axial compressive force to the radial guide bush 140-1, thereby increasing the rigidity of the radial guide bush 140-1 relative to the non-magnetic table 120.

[0054] 7 and described above provides several advantages and benefits in some implementations: first, the suspension allows the non-magnetic table 120 to be rotated 360° for threaded coupling with the device under test. Also, after assembly, the movable housing 110 can be freely rotated about the non-magnetic table 120 even while the non-magnetic table 120 is secured to the device under test, allowing for greater user flexibility in positioning and routing of cables coupled to the excitation device 100, for example.

[0055] 8A-8J illustrate an example of the excitation device 100 of FIGS. 1A-2B. In some implementations, the components of the excitation device 100 (e.g., the shaker device) can be fabricated using additive manufacturing (e.g., three-dimensional (3D) printing). For example, the components of the excitation device 100 are 3D printed using fused deposition modeling with a desktop 3D printer, where the components of the excitation device 100 are created layer by layer by applying a molten filament through a nozzle of the desktop printer to form the components. In this example, the molten filament can be plastic with various material properties (e.g., iron-filled metal composite Polylactic acid (PLA), black carbon fiber composite heat-treatable PLA (HTPLA), stainless steel composite metal filament, etc.). In another example, the components of the shaker device are 3D printed using fused deposition modeling with an industrial 3D printer, where the components of the shaker device are created layer by layer by applying a molten filament through a nozzle of the industrial printer to form the components. In this example, the molten filament may be metal (e.g., stainless steel) instead of plastic. In another example, the shaker device components are 3D printed using selective laser sintering, also known as SLS printing, in which a laser selectively sinters particles of polymer or metal powder, fusing them together and building the components layer by layer.

[0056] The example in FIG. 8A shows a perspective view of the cylindrical body 116. The cylindrical body 116 may be manufactured using additive manufacturing. For example, the cylindrical body 116 may be manufactured using a filament with magnetic properties that interact with the magnetic flux generated by the coil 165 for better performance (i.e., generating motion) of the excitation device 100. In another example, the cylindrical body 116 may be manufactured from metal (e.g., using an industrial printer and metal wire) to increase the weight of the cylindrical body 116. Thus, during operation, high forces are applied to the device / structure under test as the cylindrical body 116 moves up and down with the increased dynamic mass due to the metal. The cylindrical body 116 may include a feature-specific identifier (e.g., embossed text, delicate symbols, etc.) to identify a particular shaker device within a large array of shakers. Incorporating an identifier using traditional methods is difficult to achieve when machining an object using subtractive techniques. 3D printing offers a cost-effective solution.

[0057] In yet another example, the cylindrical body 116 may be fabricated from two or more different materials within one solid shaker body, using a plastic with ferromagnetic iron particles where special magnetic properties are required and a carbon fiber reinforced plastic for increased structural strength that cannot be achieved through conventional machining. In one scenario, the central segment of the cylindrical body 116 adjacent to the bobbin 160 and the generated magnetic field may be constructed from a magnetic material, while the remaining segments of the cylindrical body 116 may be constructed from a non-magnetic material or a carbon fiber reinforced material. Also, conductive filaments may be used in manufacturing the cylindrical body 116 to enable low-cost wire terminals printed directly onto the non-conductive housing of the shaker device. In yet another example, the cylindrical body 116 may include angled through-holes, notches, or other types of channels in shapes / geometries that are difficult, impossible, and / or economically unfeasible to fabricate using conventional methods.

[0058] The example of FIG. 8B shows a perspective view of a non-magnetic bobbin 160 including a coil 165. In this example, the bobbin 160 is manufactured by additive manufacturing using a heat-resistant, non-magnetic metal (e.g., brass). The coil 165 is wound onto the bobbin 160 using an automated winding machine. The bobbin 160 may include one or more axial notches around the periphery of the non-magnetic bobbin 160 to improve wire routing. Forming this bobbin 160 with axial notches and winding the coil 165 around the bobbin 160 using conventional milling involves multiple turning steps plus an additional milling step. However, using 3D printing to manufacture the bobbin 160 reduces manufacturing time, complexity, and cost.

[0059] The bobbin assembly (i.e., the bobbin 160 wound with the coil 165) is designed and dimensioned to be pressed into the cylindrical body 116, as shown in FIG. 8C . The mode indicator 118 is also designed and dimensioned to nest around a portion of the cylindrical body 116, as shown in FIG. 8C . FIG. 8D shows a perspective view of the mode indicator 118 as a separate component. In this example, the bobbin 160, the cylindrical body 116, and the mode indicator 118 are formed separately as separate components using 3D printing and then assembled as shown in FIG. 8C . However, in some implementations, the cylindrical body 116 is 3D printed directly around the wound bobbin 160 and / or the mode indicator 118 is 3D printed directly on the cylindrical body 116. 3D printing the components directly onto each other in this manner avoids additional assembly steps and also eliminates tolerance issues (e.g., unwanted gaps / movements between components due to slight dimensional variations).

[0060] FIG. 8E shows an example of a non-magnetic table 120 coupled with a pair of ring magnets 130. In some implementations, the table 120 is formed (e.g., by machining) from an aluminum material. In other implementations, the table 120 is 3D printed using carbon fiber reinforced plastic. By 3D printing the table 120 using a material that is both rigid / hard and lightweight, the table 120 can transmit forces to the device / structure under test while also reducing the static mass load on the device / structure under test. Mass loads change the structural dynamic characteristics of the device / structure under test; therefore, the excess weight of the table 120 will cause measurements with the excitation device 100 attached to the device / structure under test to differ from the actual dynamic characteristics of the device / structure under test.

[0061] As shown in FIG. 8E , multiple ring magnets 130 are arranged in series on the table 120 with opposing poles touching so that the multiple ring magnets 130 together function as a single large magnet. In this example, ferromagnetic disks 124 are placed on either side of the ring magnets 130 to secure the permanent ring magnets 130 to the table 120 (i.e., to prevent the magnets from sliding and rotating) and, in some implementations, act as holding devices to linearize the magnetic field at the end regions of the permanent ring magnets 130 and coils 165. In some implementations, linearizing the magnetic field can help linearize the output force when operating the excitation device 100 at large displacements. Clips 122 (e.g., “c” washers) engage with grooves on the shaft of the table 120 on the outside of the disks 124. In other implementations, the functionality of the ferromagnetic disks 124 and c-clips shown in the example of FIG. 8E may be realized as a single 3D printed part.

[0062] FIG. 8F provides a perspective view of a bottom support plate 112 according to one implementation. The bottom support plate 112 is formed with an integrated clip structure 112A formed concentrically with the opening in the bottom support plate 112 and sized to receive both the radial guide bushing 140 and the axial suspension ring magnet 150. As shown in the example of FIG. 8F, the radial guide bushing 140 is positioned within the bottom support plate 112 around the opening, and the axial suspension ring magnet 150 is positioned on top of the radial guide bushing 140. The clip structure 112A uses pretension to clip the axial suspension ring magnet 150 into place to couple the radial guide bushing 140 and the axial suspension ring magnet 150 to the bottom support plate 112. Due to the stacked arrangement of the axial suspension ring magnet 150 and the radial guide bushing 140 when coupled to the bottom support plate 112, the radial guide bushing 140 is not visible in FIG. 8F. However, the radial guide bushing 140 is shown in Figure 8G before assembly.

[0063] 8F example shows the assembly of the bottom support plate 112, in some implementations, a similar clip structure 112A is also incorporated into the top support plate 114 and / or housing 202 of the impact hammer attachment component 200 to engage and retain corresponding radial guide bushings and / or axial suspension ring magnets. The support plates 112, 114 are 3D printed using carbon fiber reinforced plastic to avoid deformation in the areas of the radial guide bushings 140 and axial suspension ring magnets 150 and to increase the stiffness of these high load areas of the shaker device.

[0064] FIG. 8H shows an example of a housing 202 of the impact hammer attachment component 200. The housing 202 may be 3D printed using carbon fiber PLA and / or stainless steel material. In this example, the composition of the housing 202 may vary based on the target weight of the specification test application (i.e., a heavy housing 202 may apply a large impact force). FIG. 81 shows an example of a set screw 210 and hammer tip 212 of the impact hammer attachment component 200. In some implementations, the set screw 210 and hammer tip 212 are 3D printed using carbon fiber PLA and / or stainless steel material. In various implementations, the set screw 210 and hammer tip 212 may be formed of the same material or different types of materials. In some implementations, the hammer tip 212 is coupled to the set screw 210 as a separate assembly step, while in other implementations, the hammer tip 212 is 3D printed directly onto the set screw 210. In this example, the set screw 210 is formed with a helical outer surface configured to engage a corresponding helical structure within the top opening of the housing 202 of the impact hammer attachment component 200, thereby allowing the set screw 210 and hammer tip 212 to be selectively coupled to the housing 202. However, in other implementations, the set screw 210 and hammer tip 212 may be integrally formed as part of the housing 202 of the impact hammer attachment component 200.

[0065] 8J shows a perspective view of the key 410. In some implementations, the key 410 is 3D printed using a carbon fiber reinforced plastic material and formed to correspond to the unique shape of the impact hammer attachment component 200, the bottom support plate 112, and / or the top support plate 114. Thus, the key-lock design of the support plates prevents disassembly of the components without specific tools (i.e., only authorized users can modify the shaker device).

[0066] FIG. 9 illustrates one example of a method for assembling the excitation device 100. First, 3D printing is used to form the cylindrical body 116, bobbin 160, mode indicator 118, top support plate 114, and bottom support plate 112 (as described above) (step 901). The bobbin 160 is wound with a coil 165 (step 903), and the wound bobbin is pressed into the cylindrical body 116 (step 905). The mode indicator 118 is then placed in place on the cylindrical body 116 (step 907), as shown in FIG. 8C. The radial guide bushing 140 and axial suspension magnet 150 are coupled to the top support plate 114 and bottom support plate 112 (step 909), as shown in FIG. 8F. Next, the table assembly of FIG. 8E is assembled (step 911) and placed inside the bobbin assembly (step 913). The bottom support plate 112 and the top support plate 114 are then locked into place using the key 410 (step 915).

[0067] In the example of FIG. 9, the various components of the excitation device 100 are manufactured separately and then assembled. However, as described above, in some implementations, the various components are formed in place by 3D printing one component directly onto another. FIG. 10 shows another example of how the excitation device 100 can be assembled by 3D printing components directly onto one another. First, as shown in FIG. 8B, the bobbin 160 is 3D printed (step 1001), and the coil 165 is wound around the bobbin 160 (step 1003). The cylindrical body 116 is then 3D printed directly onto the bobbin assembly (step 1005), and the mode indicator 118 is 3D printed directly onto the cylindrical body 116 (step 1007). Next, as shown in FIG. 8F, the top support plate 114 and the bottom support plate 112 are formed using 3D printing (step 1009), and the radial guide bushings 140 and the axial suspension magnets 150 are bonded to the top support plate 114 and the bottom support plate 112 (step 1011). Next, the table assembly of FIG. 8E is assembled (step 1013) and placed inside the bobbin assembly (step 1015). The bottom support plate 112 and the top support plate 114 are then secured in place using keys 410 (step 1017).

[0068] In some implementations of the above-described systems and methods, different materials can be combined in a single printed part by switching between different printing materials (e.g., using plastic with ferromagnetic iron particles where special magnetic properties are required and using carbon fiber reinforced plastic for increased structural strength). The different materials are bonded together throughout the entire printing process. In this way, high-strength parts with specific "local" properties can be achieved. Similar variations in materials within a single "solid" part cannot be achieved with conventional machining techniques. For example, in some implementations, the central portion of the cylindrical body 116 (closest to the bobbin 160 and the magnetic field generated through the coil 165) is formed to include magnetic material, while the rest of the body (and support plate) is formed of non-magnetic or carbon fiber reinforced material. Conductive filaments can also be used to realize low-cost wire terminals printed directly onto the non-conductive housing (e.g., the cylindrical body 116) of the excitation device 100. Similarly, in some implementations, the set screw 210 of the impact hammer attachment component is 3D printed from a rigid carbon fiber plastic, and the hammer tip 212 is 3D printed directly onto the set screw 210 using a plastic material with a different elasticity.

[0069] In some implementations, the cylindrical body 116 may be 3D printed to include angled through-holes for wire routing, notches, or other types of channels required for wire guides during assembly. These shapes / geometry are difficult (or impossible) to machine with conventional processes and would be prohibitively expensive.

[0070] In various implementations, the dimensions (and therefore output force) of the excitation device 100 are scalable. For example, to print a large excitation device 100 (i.e., an application-specific “shaker”) to provide sufficient excitation for testing on commercial vehicles, trucks, and marine vessels, all parts can be printed at a factor of 2. In some implementations, most of the components of the excitation device 100 can be 3D printed (except for the ring magnet, radial guide bushing, and coil). A large shaker with many coil windings, a large (powerful) magnet, and a high dynamic mass of the cylindrical body 116 can provide high-force excitation. Similarly, a small shaker (factor < 1) can be 3D printed, for example, for durability testing of electronic components with limited access. Furthermore, 3D printed parts are customizable. For example, the base 170 can be 3D printed in a form factor designed to connect to curved surfaces and / or other complex shapes.

[0071] Thus, the examples described herein above provide, among other things, an excitation device for inducing vibrational and / or impact forces in a device / structure under test and a mechanism for fabricating the excitation device using 3D printing. Additional features and advantages of these systems and methods are set forth in the following claims.

[0072] As used herein, relational terms such as first and second, top and bottom, etc., may be used solely to distinguish one entity or operation from another, without necessarily requiring or implying any actual relationship or order between such entities or operations. The terms “comprise,” “comprising,” “has,” “having,” “include,” “including,” “contain,” “containing,” or any other variation thereof, are intended to cover a non-exclusive inclusion, whereby a process, method, article, or apparatus that comprises, has, includes, or contains a list of elements does not include only those elements, but may include other elements not expressly listed or inherent in such process, method, article, or apparatus. An element designated by “comprise,” “having,” “including,” or “containing” does not, without further constraints, exclude the presence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, or contains the element. The terms "a" and "an" are defined herein as one or more, unless otherwise specified. The terms "substantially," "essentially," "approximately," "about," or any other variation thereof, are defined as approximating what would be understood by one of ordinary skill in the art. The term "coupled," as used herein, is defined as connected, but not necessarily directly, and not necessarily mechanically. A device or structure that is "configured" in a particular way is configured in at least that way, but may also be configured in unrecited ways.

Claims

1. 1. An excitation device for controllably inducing a force in a structure, said excitation device being selectively coupleable to said structure, said excitation device comprising: a movable housing including a first opening disposed in a first end surface of the movable housing; a piston extending through the first opening, the excitation device configured to controllably induce linear reciprocating motion in the movable housing relative to the piston; a permanent magnet fixedly coupled to the piston at a position of the piston disposed inside the movable housing; a first axial suspension magnet fixedly coupled to the movable housing and positioned proximate the first opening of the movable housing, the first axial suspension magnet configured to oppose a magnetic field of the permanent magnet, such that when the first axial suspension magnet approaches the permanent magnet, the opposing magnetic field damps movement of the movable housing relative to the piston; a first radial guide bushing disposed within the first opening of the movable housing and surrounding the piston, the first radial guide bushing being formed of a flexible, compressible material in contact with the piston and configured to limit radial movement of the movable housing relative to the piston; An excitation device comprising:

2. The excitation device of claim 1 , wherein the first radial guide bushing comprises a neoprene O-ring.

3. 2. The excitation device of claim 1, wherein the opposing magnetic fields between the permanent magnet and the first axial suspension magnet cause the first axial suspension magnet to apply an axial compressive force to the first radial guide bushing, the axial compressive force on the first radial guide bushing causing a corresponding expansion of the first radial guide bushing in a radial direction, the expansion of the first radial guide bushing in the radial direction resulting in stiffening of the first radial guide bushing relative to the circumference of the piston.

4. 2. The excitation device of claim 1, wherein the permanent magnet includes a permanent ring magnet arranged around the piston, and the first axially suspended magnet includes a first axially suspended ring magnet arranged coaxially with the piston and the opening in the movable housing, and the polarity of the first axially suspended ring magnet is arranged opposite to the polarity of the permanent ring magnet.

5. a second opening disposed in a second end face of the movable housing opposite the first end face, the second end of the piston extending through the second opening; a second axial suspension magnet fixedly coupled to the movable housing and positioned proximate the second opening of the movable housing, the second axial suspension magnet configured to oppose the magnetic field of the permanent magnet, such that when the second axial suspension magnet approaches the permanent magnet, the opposing magnetic field between the second axial suspension magnet and the permanent magnet damps movement of the movable housing relative to the piston; and a second radial guide bushing disposed within the second opening of the movable housing and surrounding the periphery of the piston, the second radial guide bushing being formed of a flexible, compressible material in contact with the piston and configured to limit radial movement of the movable housing relative to the piston; The excitation device of claim 4 further comprising:

6. the permanent magnet includes a permanent magnetic ring disposed around the piston; the first axial suspension magnet includes a first axial suspension ring magnet disposed coaxially with the piston and the opening in the movable housing; the second axial suspension magnet includes a second axial suspension ring magnet disposed coaxially with the piston and the second opening of the movable housing; the polarity of the first axially suspended ring magnet is arranged opposite to the polarity of the permanent ring magnet; The excitation device of claim 5 , wherein the polarity of the second axially suspended ring magnet is arranged opposite to the polarity of the permanent ring magnet.

7. 6. The excitation device of claim 5, wherein the opposing magnetic fields between the permanent magnet and the second axial suspension magnet cause the second axial suspension magnet to apply a second axial compression force to the second radial guide bushing, the second axial compression force on the second radial guide bushing causing a corresponding expansion of the second radial guide bushing in the radial direction, the expansion of the second radial guide bushing in the radial direction resulting in stiffening of the second radial guide bushing relative to the circumference of the piston.

8. 10. The excitation device of claim 1, further comprising a controllable electromagnet fixed to the movable housing configured to controllably apply an alternating magnetic field to the permanent magnet, the alternating magnetic field causing linear reciprocating motion of the movable housing relative to the piston.

9. 1. A suspension system for an excitation device, the excitation device including a movable housing and a piston partially disposed within the movable housing, the piston extending through a first opening in the movable housing, the excitation device configured to generate a vibration force by inducing linear reciprocating motion of the movable housing relative to the piston, the suspension system comprising: a first axial suspension magnet fixedly coupled to the movable housing and positioned proximate the first opening of the movable housing, the first axial suspension magnet configured to oppose a magnetic field of a permanent magnet fixedly coupled to the piston, such that when the first axial suspension magnet approaches the permanent magnet, the opposing magnetic field between the first axial suspension magnet and the permanent magnet damps movement of the movable housing relative to the piston; a first radial guide bushing disposed within the first opening of the movable housing and surrounding the piston, the first radial guide bushing being formed of a flexible, compressible material and configured to limit radial movement of the movable housing relative to the piston; Equipped with a first axial suspension magnet applying an axial compressive force to the first radial guide bushing due to the opposing magnetic fields between the permanent magnet and the first axial suspension magnet, the axial compressive force on the first radial guide bushing causing a corresponding expansion of the first radial guide bushing in a radial direction, the expansion of the first radial guide bushing in the radial direction resulting in stiffening of the first radial guide bushing relative to the circumference of the piston.

10. The suspension system of claim 9 , wherein the first radial guide bushing includes a neoprene O-ring in contact with the periphery of the piston.

11. 10. The suspension system of claim 9, wherein the permanent magnet comprises a permanent ring magnet disposed around the piston, and the first axial suspension magnet comprises a first axial suspension ring magnet disposed coaxially with the piston and the opening in the movable housing, and wherein a polarity of the first axial suspension ring magnet is disposed opposite a polarity of the permanent ring magnet.

12. 10. The suspension system of claim 9, wherein the movable housing further includes a second opening disposed in a second end face of the movable housing opposite the first end face in which the first opening is located, the second end of the piston extending through the second opening, and the suspension system further includes a second axial suspension magnet fixedly coupled to the movable housing and disposed proximate the second opening of the movable housing, the second axial suspension magnet configured to oppose the magnetic field of the permanent magnet, and when the second axial suspension magnet approaches the permanent magnet, the opposing magnetic field between the second axial suspension magnet and the permanent magnet damps motion of the movable housing relative to the piston.

13. the permanent magnet includes a permanent ring magnet disposed around the piston; the first axial suspension magnet includes a first axial suspension ring magnet disposed coaxially with the piston and the opening in the movable housing; the second axial suspension magnet includes a second axial suspension ring magnet disposed coaxially with the piston and the second opening of the movable housing; the polarity of the first axially suspended ring magnet is arranged opposite to the polarity of the permanent ring magnet; The suspension system of claim 12 , wherein the polarity of the second axial suspension ring magnet is arranged opposite the polarity of the permanent ring magnet.

14. a second radial guide bushing disposed within the second opening of the movable housing and surrounding the periphery of the piston, the second radial guide bushing configured to limit radial movement of the movable housing relative to the piston at the second opening; The suspension system of claim 12 further comprising:

15. 10. The suspension system of claim 9, wherein the excitation device further includes a controllable electromagnet fixed to the movable housing configured to controllably apply an alternating magnetic field to the permanent magnet, the alternating magnetic field inducing the linear reciprocating motion of the movable housing relative to the piston.

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