PCT PATENT APPLICATION

TITLE: SYSTEM AND METHOD FOR GENERATING ELECTRIC

POWER FROM MECHANICAL STRAINS WITHIN A VEHICLE SUSPENSION SYSTEM

FIELD OF THE INVENTION

[0001] The present invention generally concerns a system and method of subjecting piezoelectric structures to the mechanical energy generated within a vehicle suspension system, thereby generating electric power for integrated electronic components. Piezoelectric technology is utilized to convert mechanical strains within a vehicle suspension system to electric charge that is then conditioned and stored in an energy storage device. Sufficient accumulations of such stored energy can then power electronic systems, including suspension monitoring and feedback systems.

BACKGROUND OF THE INVENTION

[0002] The incorporation of electronic monitoring and feedback systems within vehicles yields many practical advantages. Electronic monitoring systems may include sensors and other components for obtaining information regarding various physical parameters of vehicle performance.

[0003] One known example of a vehicle monitoring system involves the incorporation of sensory components within a tire or wheel environment, where parameters such as temperature, pressure, number of tire revolutions, vehicle speed, etc. maybe determined. Such performance information may become useful in tire monitoring and warning systems, and may even potentially be employed with feedback systems to regulate proper tire pressure levels. U.S. Patent No. 5,749,984 (Frey et al.) discloses a tire monitoring system and method that is capable of determining such information as tire deflection, tire speed, and number of tire revolutions. Another example of a tire electronics system can be found in U.S. Patent No. 4,510,484 (Snyder), which concerns an abnormal tire condition warning system. U.S.

Patent No. 4,862,486 (Wing et al.) also relates to tire electronics, and more particularly discloses an exemplary revolution counter for use in conjunction with automotive and truck tires.

[0004] Monitoring systems within a tire or wheel assembly or associated with other portions of a motor vehicle may provide the additional benefits afforded through provision of identification parameters, such as may be useful for asset tracking and performance characterization for commercial vehicular applications. Commercial truck fleets, aviation crafts and earthmover/mining vehicles are all viable industries that could utilize the benefits of vehicle monitoring systems and related information transmission. Vehicle location and performance can be optimized for more expensive applications such as those concerning earth mining equipment. Entire fleets of vehicles could be tracked using RF tag transmission, exemplary aspects of which are disclosed in U.S. Patent No. 5,457,447 (Ghaem et al.). [0005] Certain aspects of the present technology, as will be discussed later in further detail, concern an electronic monitoring system provided in conjunction with a vehicle suspension system. Like electronic systems integrated with a tire or wheel assembly, an electronics package integrated with a vehicle suspension system would attain benefits by being self-powered. Integrated tire electronics systems have conventionally been powered by a variety of techniques and different power generation systems. Examples of mechanical features for generating energy from tire movement are disclosed in U.S. Patent Nos. 4,061,200 (Thompson) and 3,760,351 (Thomas). Such examples provide bulky complex systems that are generally not preferred for incorporation with modern tire applications. [0006] Some tire electronics systems have been powered by various piezoelectric devices. U.S. Patent No. 6,438,193 (Ko et al.) discloses a self-powered tire revolution counter that includes a piezoelectric element mounted in a tire in a manner so as to be subjected to periodic mechanical stresses as the tire rotates and to provide periodic pulses in response thereto. Yet another example of piezoelectric devices used for powering tire electronics systems is disclosed in U.S. Patent No. 4,510,484 (Snyder), which concerns a piezoelectric reed power supply symmetrically configured about a radiating center line of a tire.

[0007] Another typical solution for powering tire or other vehicle electronics systems corresponds to the use of a non-rechargeable battery, which inherently provides an inconvenience to the user since proper electronics system operation is dependent on periodic

battery replacement. Conventional batteries also often contain heavy metals that are not environmentally friendly and which present disposal concerns, especially when employed in highly numerous quantities. Still further, batteries tend to deplete their energy storage quite rapidly when powering electronic applications characterized by complex levels of functionality. Battery storage depletion is especially prevalent in electronic systems that transmit information over a relatively far distance such as from truck wheel locations to a receiver in the truck cabin. Even when batteries are used in electronics systems that transmit from wheel locations to a closer receiver location, information is then typically relayed via hard-wire transmission medium from the RF receiver location to the vehicle cab thus requiring the installation of additional and often expensive communications hardware in a vehicle.

[0008] Yet another known method for deriving power for tire monitoring systems relates to scavenging RF beam power with an interrogation antenna in close proximity to a tire and integrated electronic features. Energy that is radiated from the antenna is scavenged to power the electronics, which must often be very specialized ultra-low-power electronics limited to within a few microwatts. Interrogation antennas employed in conjunction with beam- powered electronics must typically be placed in relatively close proximity (within about two feet) to each wheel well due to limited transmission ranges. This typically requires multiple interrogation antennas per vehicle, thus adding to potential equipment costs. Each antenna is also quite susceptible to damage from road hazards, and thus for many reasons may not be the most desirable solution for powering certain tire electronic applications. [0009] Many known methods for harvesting power and providing power to vehicle electronics systems exist. While various such methods and systems have been developed, no design appears to have emerged that generally encompasses all of the desired characteristics as hereafter presented in accordance with the subject technology. The disclosures of all of the foregoing United States patents are hereby fully incorporated into this application for all purposes by reference thereto.

SUMMARY OF THE INVENTION

[0010] In view of the recognized features encountered in the prior art and addressed by the present subject matter, an improved system and method for powering electronic systems

integrated within a vehicle suspension has been developed. A vehicle suspension system may incorporate a piezoelectric device for converting mechanical strains incident therein to electric charge that is then conditioned and stored in one or more energy storage devices. Sufficient accumulations of such stored energy can then power various electronic components associated with a suspension system, such as but not limited to sensory components for monitoring shock absorbers, springs and other suspension components as well as control elements for coordinating feedback to the vehicle suspension system. [0011] hi accordance with more particular aspects of the disclosed technology, it is an object of the present subject matter to provide a vehicle electronics package with components that are self-powered by energy harvested from integrated piezoelectric structures, and may correspond with numerous electronic applications. One exemplary electronic application concerns a monitoring system designed to measure and transmit information regarding suspension conditions such as the occurrence of a high deflection driving condition. Feedback components may also be coupled to the monitoring system to facilitate potential adjustment of suspension system parameters.

[0012] Various features and aspects of the subject vehicle suspension monitoring system and specialized power generation device offer a plurality of advantages. The disclosed technology provides for a self-powered electronics system that is not dependent on replacement of batteries. Although batteries and battery-operated devices may still be incorporated with aspects of the present subject matter, many complications regarding electronics that are solely powered by batteries are obviated in accordance with the disclosed technology.

[0013] An advantage of the present subject matter is that there are fewer limitations regarding the type and amount of electronic equipment capable of utilization within a monitoring system. Vehicle electronics powered by conventional methods other than as in accordance with the disclosed piezoelectric technology are often limited to ultra-low power devices. Devices in accordance with the disclosed technology are not necessarily subject to such extreme power limitations. This advantage further facilitates greater functionality of a vehicle suspension monitoring system, as more components and/or higher-level equipment may potentially be utilized.

[0014] Another advantage of the present subject matter is that the disclosed system and method for generating power and utilizing such power can be used in accordance with a

variety of existing applications. Measurement capabilities, monitoring and warning systems, vehicle feedback systems, and asset tracking potential maybe possible for applications such as commercial truck fleets, airplanes, and mining/earthmover equipment. [0015] In one exemplary embodiment of the present subj ect matter, a piezoelectric device is configured to generate electric charge therein when the support structure to which the piezoelectric device is attached is subjected to mechanical strains. The piezoelectric device may be integrated with a portion of the vehicle suspension system and is configured to generate electric charge therein upon the suspension system generating mechanical strains during normal operation of a vehicle. An electronics assembly may be coupled to the piezoelectric device and selected components therein may be powered by the electric charge generated by the piezoelectric device. In addition, signals from the piezoelectric device may also provide strain related signals to the electronic assembly thereby providing a sensor function for the electronics assembly.

[0016] In accordance with more particular embodiments of the presently disclosed technology, some embodiments of the aforementioned piezoelectric device(s) may correspond to a fiber composite structure with a plurality of piezoelectric fibers embedded in an epoxy matrix. The piezoelectric device(s) may alternatively include a piezoceramic wafer substantially surrounded by a protective casing and provided with embedded first and second electrical leads for connecting to the piezoceramic wafer (e.g., via electrodes), hi still further embodiments, the piezoelectric device(s) include a layer of piezoceramic material with respective conductive layers (e.g., aluminum or stainless steel layers) adhered to opposing sides thereof with a polyimide adhesive (e.g., a high temperature thermoplastic polyimide). Piezoelectric devices may sometimes include multiple piezoelectric elements connected together in series or parallel. Such multiple piezoelectric elements may also be configured with polarization directions that are either in-phase or opposing, and with either d33 or d31 displacement modes. The piezoelectric elements may include such materials as lead zirconate titanate (PZT), barium titanate, quartz, cadmium sulfide, polyvinyl fluoride (PVF) and polyvinyl chloride (PVC).

[0017] Additional objects and advantages of the present subject matter are set forth in, or will be apparent to, those of ordinary skill in the art from the detailed description herein. Also, it should be further appreciated that modifications and variations to the specifically illustrated, referred and discussed features and steps hereof may be practiced in various

embodiments and uses of the invention without departing from the spirit and scope of the subject matter. Variations may include, but are not limited to, substitution of equivalent means, features, or steps for those illustrated, referenced, or discussed, and the functional, operational, or positional reversal of various parts, features, steps, or the like. [0018] Still further, it is to be understood that different embodiments, as well as different presently preferred embodiments, of the present subject matter may include various combinations or configurations of presently disclosed features, steps, or elements, or their equivalents (including combinations of features, parts, or steps or configurations thereof not expressly shown in the figures or stated in the detailed description of such figures). [0019] Additional embodiments of the present subject matter, not necessarily expressed in this summarized section, may include and incorporate various combinations of aspects of features, components, or steps referenced in the summarized objectives above, and/or other features, components, or steps as otherwise discussed in this application. Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the remainder of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] A full and enabling disclosure of the present subject matter, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

[0021] Figures IA, IB, and 1C display generally schematic illustrations of portions of representative vehicle suspension assembly with which the present subject matter may be associated;

[0022] Figure 2A displays a generally perspective view of a first exemplary piezoelectric structure for use with a power generation device in accordance with the present subject matter;

[0023] Figure 2B displays a generally perspective view of a second exemplary piezoelectric structure for use with a power generation device in accordance with the present subject matter;

[0024] Figure 2C displays a generally exploded perspective view of a third exemplary piezoelectric structure for use with a power generation device in accordance with the present subject matter;

[0025] Figure 3 provides a schematic representation of additional exemplary aspects of a power generation device in accordance with the present subject matter, particularly regarding an exemplary power conditioning module;

[0026] Figure 4 provides a block diagram representation of exemplary integrated self- powered electronics including a power generation device and an application electronics system and exemplary interaction thereof in accordance with the present subject matter; [0027] Figures 5 A, 5B, 5 C and 5D illustrate respective exemplary configurations of multiple piezoelectric elements in stacked combination for use in a power generation device in accordance with the present subject matter;

[0028] Figures 6A and 6B respectively illustrate exemplary configurations of multiple piezoelectric elements in series and parallel combination for use in a power generation device in accordance with the present subject matter;

[0029] Figures 7A, 7B and 7C respectively illustrate exemplary configurations of multiple piezoelectric elements coupled to one or more energy storage devices and one or more application electronics modules in accordance with exemplary power generation device and application electronics system embodiments of the present subject matter; [0030] Figure 8 provides a block diagram representation of an exemplary application electronics system in accordance with the disclosed technology; and

[0031] Figure 9 provides a block diagram representation of an exemplary remote receiver configuration in accordance with the present subject matte.

[0032] Repeat use of reference characters throughout the present specification and appended drawings is intended to represent same or analogous features or elements of the present subject matter. It should be appreciated that various features illustrated in the appended drawings are not necessarily drawn to scale, and thus relative relationships among the features in such drawings should not be limiting the presently disclosed technology.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] As discussed in the Summary of the Invention section, the present subject matter is particularly concerned with an improved system and method for powering electronic systems integrated within a vehicle suspension. A power generation device utilizes piezoelectric technology to convert mechanical strain associated with vehicle suspension flexure to electric current that is then conditioned and stored in an energy storage device. Sufficient accumulations of such stored energy can then power electronic systems, examples of which include components for identifying various physical parameters as well as radio frequency (RF) transmission devices. The piezoelectric technology may also be used as sensory components for monitoring shock absorbers, springs and other suspension components as well as control elements for coordinating feedback to the vehicle suspension system.

[0034] A power generation device in accordance with the disclosed technology generally includes two exemplary components, a piezoelectric structure and a power conditioning module. Aspects of various exemplary piezoelectric structures are described with reference to Figures 2A, 2B and 2C and an exemplary power conditioning module (with energy storage device) is presented in and discussed with reference to Figure 3. Additional aspects related to exemplary configurations of one or more piezoelectric elements in a power generation device are illustrated in Figures 5A-5D, respectively, and in Figures 6A and 6B. The output of the power conditioning module may then preferably be used to power electronics systems associated with a vehicle suspension assembly. Aspects of exemplary interaction between a power generation device and an application electronics system is discussed with reference to Figure 4. Further aspects of exemplary interaction between multiple piezoelectric elements and one or more application electronics modules are represented in Figures 7 A, 7B and 7C. Selected combinations of the aforementioned aspects of the disclosed technology correspond to a plurality of different embodiments of the present subject matter. [0035] It should be noted that each of the exemplary embodiments presented and discussed herein should not insinuate limitations of the present subject matter. Features or steps illustrated or described as part of one embodiment may be used in combination with aspects of another embodiment to yield yet further embodiments. Additionally, certain features may be interchanged with similar devices or features not expressly mentioned which

perform the same or similar function. Similarly, certain process steps may be interchanged or employed in combination with other steps to yield additional exemplary embodiments of a method for generating electric power from a flexing vehicle suspension's mechanical energy. [0036] Reference will now be made in detail to the presently preferred embodiments of the subject system and method of generating power for electronics systems integrated within a vehicle suspension assembly 200.

[0037] It should be clearly understood that while the principle portion of the disclosure herein maybe directed to vehicles primarily intended for off-road use including vehicles such as earthmovers and dump truck, such is not a limitation of the present technology. In particular, the present technology maybe applied to any vehicle capable of movement over a travel path, the vehicle including at least some form of suspension assembly even if the suspension system is not in continuous use. As such, a vehicle as described herein may encompass any vehicle including land, sea, rail, and air vehicles wherein a suspension system is provided for use at least briefly during operation of the vehicle. For example, an aircraft landing gear may incorporate a suspension system used only during landing or takeoff of the craft that may take advantage of the present technology. Likewise, certain seagoing craft including hydrofoil craft incorporate suspension systems that may take advantage of the present technology. Moreover, it should be understood that while portions of the present disclosure may refer more or less specifically to suspension components related to motor vehicles and the incorporation there into of piezoelectric devices, such is not intended as a limitation of the present subject matter but rather a convenient exemplary embodiment thereof. In particular, the present subject matter may be applied to any vehicle, motor driven or not, that incorporates any type of suspension system subject to mechanical strain upon movement of the vehicle.

[0038] Referring now to the drawings, Figure IA provides a generally schematic illustration of portions of a representative vehicle suspension assembly 200 with integrated self-powered electronic components in accordance with the present subject matter. One or more power generation devices (PGD) 14 are preferably provided in conjunction with electronic components integrated with the vehicle suspension assembly 200 such that the electronics components are self-powered within vehicle suspension assembly 200. Ih accordance with the variety of possible locations for PGD 14, it should be understood that the

term "integrated" generally encompasses all possible locations, including being mounted on or within certain components of the vehicle suspension assembly 200. [0039] The capabilities of the subject power generation device with piezoelectric materials, as hereafter presented, offer numerous advantages over conventional techniques for providing power for electronics assemblies associated with a vehicle suspension assembly. Antenna beam power scavenging techniques, as previously discussed, are no longer one of limited options to choose from for powering vehicle electronics. As such, the functional capabilities of many types of vehicle electronics are generally increased. The option of utilizing batteries for power generation is no longer essential, thus avoiding costly and cumbersome battery replacement. Although the presently disclosed technology provides for a power generation device that enables antenna beam power and batteries to be eliminated, it should be appreciated that a power generation device could employ a hybrid combination of piezoelectric technology and/or batteries and/or antenna beam scavenging to power different selected electronic components within a vehicle suspension assembly. [0040] PGD 14, as illustrated in the exemplary vehicle suspension assembly 200 of Figure IA, may be mounted to various locations in or on the vehicle suspension assembly 200. Representative possible locations include on an outer surface of shock absorber 230, and support structure 226 as illustrated in Figure IA. Alternate locations for mounting PGD 14 are illustrated in Figure IB at support structures 224 and 226. In addition, although not illustrated in the drawing, PGD 14 may be mounted in or within spring 222. Further, with reference to Figure 1C, PGD 14 may be mounted to a leaf spring structure 232 as may commonly be associated with a rear wheel 212 of a vehicle. PGD 14 may be mounted directly to the various vehicle suspension components or, alternatively, may be bonded to the vehicle suspension component by way of decoupling intermediary. In an exemplary embodiment, such decoupling intermediary may be, but is not limited to, rubber. [0041] Although these locations are generally well-suited for actuation of the piezoelectric device within PGD 14 as the exterior tread portion of tire 210 moves along a ground surface 240 and results in flexure of the tire structure and vehicle suspension assembly 200, these exemplarily illustrated location should be understood to be non-limiting in that suitable locations include virtually any location associated with the vehicle suspension assembly that may be subject to flexure as the associated vehicle moves over a travel surface. This vehicle suspension assembly flexure coupled with the general mechanical vibrations as

the tire 210 moves along a surface 240 enable piezoelectric device within the power generation device 14 to generate electric current, which is then conditioned and stored in an energy storage device for powering the application electronics as will be described later with respect to Figures 3 and 4.

[0042] The piezoelectric device associated with PGD 14 may comprise a variety of piezoelectric materials, including but not limited to barium titanate, polyvinylidene fluoride (PVDF), lead zirconate titanate (PZT) crystals, or PZT fibers. A particular type of piezoelectric material that maybe utilized in accordance with the subject power generation device is a piezoelectric fiber composite structure, such as those disclosed in U.S. Patent Nos. 5,869,189 and 6,048,622 issued to Hagood, IV et al, hereby incorporated by reference for all purposes. A similar example of such Active Fiber Composites (AFCs) that may be utilized in accordance with the present subject matter corresponds to "PiezoFlex" brand technology, such as offered for sale by Continuum Control Corporation.

[0043] Figure 2A displays an isometric view of a piezoelectric AFC structure 28 in accordance with exemplary aspects of the presently disclosed power generation device. Such a piezoelectric AFC structure 28 includes a plurality of piezoelectric fibers 30 that are unidirectionally aligned to provide actuation and stiffness of AFC structure 28. The fibers 30 are surrounded by a resin matrix 32 of epoxy or polymer that provides a damage tolerance through load transfer mechanisms. The piezoelectric fibers have a common poling direction 34 transverse to their substantially co-parallel axial arrangement. [0044] Electrode layers are preferably provided on separate substrates along two opposing surfaces of the fiber/resin matrix configuration to provide electrical input and output to the AFC structure 28. In accordance with the exemplary embodiment of Figure 2 A, electrode layers 36 are configured with an interdigital arrangement with alternating finger-to- finger polarity. Such interdigitated electrode layers 36 may be etched onto separate substrate layers (of polyimide or polyester, for example) using screen-printing techniques as known in the art and conductive ink such as silver-loaded epoxy. The alignment of the interdigital electrode configuration of Figure 2 A is designed to enhance the directionality of the electromechanical response of the AFC structure 28, as well as provide for relatively high charge and coupling coefficients. The amount of resin matrix 32 between electrodes 36 and fibers 30 is preferably minimized to achieve greater performance capabilities.

[0045] More specific characteristics of a piezoelectric AFC structure, such as the exemplary embodiment of Figure 2A, can be tailored for different applications. For instance, the piezoelectric fibers may correspond to a variety of different PZT materials, including PZT 5A, PZT 5H, PZT 4, PZT 8, and PMN-33PT. Another specific design constraint corresponds to the diameter 38 of the piezoelectric fibers, which may typically be in a range from about three thousandths of an inch (mils) to about fifteen mils. Other specific dimensions that may be designed for particular applications include the width 40 and pitch 42 of the electrode fingers in interdigital layers 36. An example of electrode finger width 40 corresponds to about twenty-five mils, and an exemplary range for electrode pitch 42 corresponds to from about twenty mils to about one-hundred mils. A specific example of an overall piezoelectric AFC structure for use in accordance with the present subject matter comprises interdigital electrodes with a forty-five mil electrode finger pitch and PZT-5 A piezoelectric fibers with a ten mil diameter.

[0046] Additional design constraints of a piezoelectric structure for use in a power generation device in accordance with the present subject matter may be considered for certain applications. For instance, there may be certain design constraints relative to the size and processing capabilities of a piezoelectric patch for integration within a vehicle suspension assembly. Assume that a PGD 14 in accordance with the disclosed technology comprises a piezoelectric device mounted on vehicle suspension assembly with an integrated power conditioning module. The PGD 14 may be bonded directly in or on a vehicle suspension component or may preferably be provided in a rubber or elastomeric casing or supported on a rubber, fiberglass, or other supportive substrate when it is adhered in or on the vehicle suspension assembly to provide it with protection from damage caused by road hazards including, for example, rocks and other debris as may be present on a travel surface. A rubber casing or substrate additionally provides for facilitated adhesion of the PGD 14 to a vehicle suspension structure.

[0047] In accordance with such exemplary PGD configurations as mentioned above, there is generally no length constraint of the piezoelectric patch; however, a maximum width of about eighty mm may be desired for certain applications. A maximum thickness of the piezoelectric patch (without a power conditioning module) may be about seven-hundred micrometers, and a maximum mass of about twenty grams (including a piezoelectric patch and a power conditioning module) may be desired for certain applications. In addition, a

PGD in accordance with the present subject matter should preferably be able to withstand operating conditions from about negative forty degrees Celsius to about one-hundred-twenty- five degrees Celsius, and an endurance of either about ten years or seven-hundred-thousand miles.

[0048] Yet another type of piezoelectric patch that may be utilized in PGD 14 in accordance with some embodiments of the present invention corresponds to generally solid piezoeceramic wafers. Such piezoceramic wafers may be single-crystal or polycrystalline structures, including but not limited to wafers made of polycrystalline ferroelectric materials such as barium titanate (BaTiO3) and lead zirconate titanate (PZT).

[0049] Referring now to Figure 2B, a more particular example of a potential piezoelectric device 28' for use in a power generation device (PGD) 14 of the presently disclosed technology is illustrated. Piezoelectric device 28' corresponds to one or more piezoceramic wafers provided in one of a unimorph, bimorph or stacked/sandwich arrangement and packaged within a protective skin 108. A unimorph arrangement generally corresponds to a single modular portion (i.e., layer) of piezoceramic material, which may be bonded to an inactive substrate in some embodiments. A bimorph arrangement generally corresponds to two modular portions (i.e., layers) of piezoceramic material that are bonded to opposing sides of a center metallic shim layer, and a stacked, or sandwich, arrangement corresponds to several piezoelectric elements provided adjacent to and coupled with one another. Bimorph and stacked arrangements may yield a higher level of generated charge versus amount of mechanical displacement than unimorph arrangements for certain applications. [0050] Referring still to Figure 2B, the protective casing 108 in which one or more piezoceramic wafers may be provided may serve as electrical insulation for the piezoceramic wafers as well as a defense against humidity and potentially harsh contaminants. In some embodiments, the piezoceramic wafers may comprise specific PZT materials such as PZT-5A and/or PZT-5H. Distributed electrodes 110 may be made of such material such as nickel and may be provided on top and bottom surfaces of the assembly for coupling to pre-attached first and second electrical leads 112 and 114, respectively. Pins for connecting to leads 112 and 114 may be accessible via a connector element 120 for a reliable component with no soldered wires. Additional pins at connector element 120 may provide respective electrical connections 116 and 118 for poling the piezoceramic element(s) within piezoelectric device 28' . A specific example of the type of piezoelectric device represented in Figure 2B and that

may be utilized in accordance with the present subject matter corresponds to "QuickPack" brand technology (e.g., ACX QuickPack-PowerAct QP 15W), such as offered for sale by Mide Technology Corporation.

[0051] A still further example of a piezoelectric device for use in a power generation device in accordance with the present subject matter is represented in Figure 2C as element 28" . Figure 2C depicts a generally exploded perspective view of a piezoelectric element 28", including multiple layers provided in a generally stacked arrangement in which individual materials are layered on top of one another. A first layer in the layered composite comprising piezoelectric element 28" corresponds to a metal substrate layer 120, for example but not limited to a layer of stainless steel. Subsequent adhesive layers 122 are provided around an internal layer 124 of piezoelectric material. Piezoelectric layer 124 may correspond in some embodiments to a piezoceramic material such as PZT. Adhesive layers 122 may in some embodiments comprise a polyimide material or more specifically a high temperature thermoplastic polyimide (e.g., LaRCTM-SI brand material such as developed by NASA's Langley Research Center). A top layer 126 of piezoelectric element 28" comprises a metallic material such as but not limited to aluminum. Such multiple layers may be combined together by placing the entire assembly in an autoclave in which the multiple layers are heated, squeezed together, allowed to cook, and then cooled to around room temperature. As the piezoelectric element 28' begins to cool, the substrate layer 120 which is bonded to piezoceramic layer 124 acts to keep piezoceramic layer 124 in compression while is itself in a continuous state of tension. This induced pre-stress may cause the piezoelectric device to be ultimately formed in a slightly curved configuration, and allows the finished device to be subjected to much higher levels of mechanical deflection than some conventional piezoelectric devices without cracking.

[0052] A specific example of the type of piezoelectric device represented in Figure 2C and that may be utilized in accordance with the present subject matter corresponds to "THUNDER" brand technology (e.g., Face Thunder Actuator 6R), such as offered for sale by Face International Corporation. THUNDER products generally correspond to Thin Layer Unimorph Ferroelectric Driver and Sensor devices that are made of multiple layers of material held together in a "sandwich-like" package with high strength bonding materials configured to provide internal pre-stresses. The adhesive layers 122 of piezoelectric element

28" hold the various device layers together despite relatively high internal stresses that are created during device manufacturing.

[0053] It should be appreciated that variations to the exemplary piezoelectric devices discussed above for incorporation with a power generation device of the present subject matter as appreciated by one of ordinary skill in the art may be implemented, and that such variations are within the spirit and scope of the present invention. For example, although the piezoelectric elements presented herein are generally rectangular in shape, it should be appreciated that piezoelectric elements of different shapes such as circular, square or otherwise may also be utilized. Additional modifications to the geometry, dimensions, material type, etc. of the piezoelectric elements are generally considered within the purview of one of ordinary skill in the art.

[0054] Still further design aspects that may be implemented in accordance with the present technology concern combination of multiple piezoelectric elements, such as now discussed with reference to Figures 5 A-5D and 6A-6B respectively. Figures 5 A-5D illustrate respective exemplary configurations of how multiple elements 130 maybe stacked vertically inside a PGD. Although only two piezoelectric elements 130 are illustrated in each configuration of Figures 5A-5D, it should be appreciated that more than two piezoelectric elements may be utilized. Pieozoelectric elements 130 may correspond to single-crystal or polycrystalline piezoceramic wafers, including but not limited to wafers made of polycrystalline ferroelectric materials such as barium titanate (BaTiCβ) and lead zirconate titanate (PZT). Although not illustrated in Figures 5A-5D, it should be appreciated that a center conductive shim layer may be provided in between each adjacent piezoelectric element 130, such as characteristic of some bimorph and stacked piezoelectric arrangements. [0055] The various configurations depicted in Figures 5 A-5D illustrate different poling and displacement modes for the combined piezoelectric elements 130. Shorter arrows 132 and 134 within each piezoelectric element 130 represent the poling direction in each piezoelectric element, generally pointing from the positive to the negative poling electrode to which a high DC voltage would have been applied during manufacture of such pieozelectric elements 130. Although not limited to the exemplary poling configurations shown in Figures 5A-5D, all such piezoelectric elements 130 are characterized by polarization vectors 132 and 134. Figures 7B and 7D respectively illustrate configurations with both piezoelectric elements 130 having polarization vectors that are in-phase, while Figures 5 A and 5D

respectively illustrate configurations with both piezoelectric elements 130 having polarization vectors that are opposing, or out of phase.

[0056] The piezoelectric configurations of Figures 5A and 5B are both in d33 mode, wherein displacement forces (represented by arrows 136) correspond to an expansion in the same direction as the electrical field and the poling direction. The piezoelectric configurations of Figures 5C and 5D are both in d31 mode, wherein displacement forces (represented by arrows 138) correspond to a contraction perpendicular to the electrical field and the poling direction.

[0057] The configurations of Figures 5A-5D illustrate respective examples of how more piezoelectric material can be provided in a given strain field with the same footprint as a single piezoelectric element. Such an arrangement has the potential to yield more energy output than may be obtained with a single piezoelectric element.

[0058] Referring now to Figures 6A and 6B, it should be appreciated that piezoelectric elements 140 can be electrically connected in series (such as depicted in Figure 6A), in parallel (as depicted in Figure 6B), or in some combination thereof when more than two piezoelectric elements are combined. A series connection among piezoelectric elements 140 provides a generally higher voltage and lower current output than a single piezoelectric element. Such a configuration, as represented in Figure 6A, may be especially useful for sensing applications, such as detection of rough terrain as a vehicle tire passes higher vibrational content to the vehicle suspension assembly with which the piezoelectric elements may be associated. A parallel connection among piezoelectric elements 140 provides a generally lower voltage and higher current output, which may be especially useful in energy harvesting applications. Such a configuration, as represented in Figure 6B, helps to reduce energy leakages and may simplify power conditioning electronics. Piezoelectric elements 140 may correspond to such specific piezoelectric elements 28, 28' and 28" as illustrated and discussed with reference to Figures 2A ₅ 2B and 2C, respectively, or in other embodiments as piezoceramic wafers such as elements 130 depicted in Figures 5A-5D, respectively. [0059] A second main component of PGD 14, in addition to a piezoelectric element is a power conditioning module, an exemplary embodiment of which is represented in Figure 3. The major functionality of a power conditioning module in accordance with the present subject matter is to rectify, condition and store the electric charge that is generated in the piezoelectric structure 140. In general, power conditioning modules may be particularly

designed for different electronics applications for which power is harvested. In accordance with an exemplary embodiment of a vehicle suspension monitoring system as disclosed in the present specification, the exemplary power conditioning module of Figure 3 is designed according to certain dynamic energy requirements. In particular, the exemplary power conditioning module of Figure 3 is designed such that the voltage output 44 is generally about five volts, the maximum ripple of output voltage 44 is within ± ten mvolts, the minimum duty cycle of output voltage 44 is about sixty seconds, and the maximum duty cycle of output voltage 44 is about five seconds. Additional design requirements within which the exemplary power conditioning module embodiment of Figure 3 operates correspond to a maximum energy requirement into an electronics system of about four mJoules and a time duration for which an electronics system can operate between about twenty- five msec and about two-hundred msec, depending on the functionality of the electronics system.

[0060] With further reference to the exemplary power conditioning module of Figure 3, one or more piezoelectric elements 140 are connected in parallel with a rectifier, for example full-bridge rectifier 46. Alternative rectifier configurations could correspond to a doubling rectifier or an N-stage voltage multiplier. The rectified signal from rectifier 46 is then stored in electrolytic capacitor 48. A specific example of an electrolytic capacitor 48 suitable for employment in the exemplary power conditioning module of Figure 3 corresponds to a Panasonic TEL series tantalum capacitor with a capacitance of about forty-seven μFarads. Other specific electrolytic capacitors may similarly be suitable for utilization as a storage element in accordance with the disclosed power conditioning module. Other energy storage elements, such as rechargeable batteries or super capacitors, may provide a suitable alternative in certain applications as an energy storage device for a power conditioning module.

[0061] Once a sufficient amount of energy has accumulated in electrolytic capacitor 48 (or other suitable energy storage device), a DMOS FET transistor 54 acts as a switch to release the stored energy in capacitor 48 to a voltage regulator 52. An example of a voltage regulator suitable for use in the exemplary embodiment of Figure 3 is a dual- mode five- volt programmable micropower voltage regulator such as the MAX666 brand offered for sale by Maxim Integrated Products. Such a voltage regulator is ideally suited for electronics systems that may typically have been battery-powered systems, and effectively convert the voltage

across capacitor 48 to a regulated five volt output voltage 44. A bipolar PNP transistor 50 and zener diode 56 are additionally provided in the exemplary power conditioning module of Figure 3.

[0062] Initially, transistors 50 and 54 are off, and the ground at the drain of transistor 54 is floating such that no output voltage 44 is provided. As capacitor 48 charges to a sufficient voltage level (determined by zener diode 56 and the base-emitter junction of transistor 50), transistor 50 turns on, activating transistor 54 and latching transistor 50. At this point, capacitor 48 is allowed to discharge through the circuitry providing a five volt regulated output 44 to an electronics system. Typically, when the application electronics to which output voltage 44 is supplied has finished its useful work, the electronics system sends a signal back at signal path 58, through resistor 60 and capacitor 62 to turn off PNP transistor 50 and deactivate FET 54 such that energy can once again begin to accumulate on capacitor 48.

[0063] Energy that is generated by PGD 14 may be applied to a variety of different vehicle application electronics systems in accordance with the present subject matter. Figure 4 illustrates an exemplary aspect of interaction between a PGD 14 and a vehicle application electronics system (AES) 12.

[0064] In accordance with Figure 4, energy is allowed to accumulate on an energy storage device in the PGD (for example, capacitor 48) until a sufficient charge has been obtained to perform the desired functions in AES 12. Between power cycles, AES 12 remains unpowered, and thus the activation of AES 12 is governed by the rate at which energy is accumulated in the energy storage device of PGD 14. When sufficient energy is accumulated in PGD 14, a supply voltage "Vdd" and ground voltage "Vss" will be provided at paths 64 and 66 respectively to AES 12. AES 12 will return an "Active" signal along path 58 indicating electronics in AES 12 are currently functioning. When the given electronics in AES 12 are done with their respective tasks, then the "Active" signal goes low and the energy storage device in PGD 14 once again accumulates energy. This cycle will repeat as long as a vehicle suspension assembly vibrates at or above a given threshold. [0065] It should be appreciated in accordance with the disclosed technology that other electronic devices other than those specifically disclosed in the present specification may be utilized with the subject power generation technology. For instance, it may be desired to transmit other types of information other than tat related to travel path texture. A vehicle

suspension assembly electronics system may be coupled with a global positioning system (GPS) to pinpoint a vehicle's precise location. A piezoelectric PGD may alternatively be utilized to power light assemblies or feedback systems in a wheel assembly. The number of electronics applications capable of being powered in accordance with aspects of the disclosed technology are vastly numerous and should in no way be limiting to the present subject matter.

[0066] It should be further appreciated in accordance with the presently disclosed technology that embodiments of the subject system and method for generating electric power are not limited to one power generation device and one electronics module per vehicle suspension assembly. The selective combination of multiple elements as disclosed herein should not be limiting to the spirit and scope of the present invention. [0067] Referring now to Figures 7A, 7B and 7C, different exemplary combinations of features are presented for potential incorporation within a vehicle suspension, such as depicted in Figure IA. With reference to Figures 7A, 7B and 7C, multiple piezoelectric elements 140 may be associated with a vehicle suspension assembly. Such piezoelectric elements 140 may be positioned in close proximity to one another on a vehicle suspension assembly or may be distributed at different locations throughout the vehicle suspension assembly. Piezoelectric elements 140 may in some embodiments comprise such specific exemplary piezoelectric elements 28, 28' and 28" as illustrated and discussed with reference to Figures 2A, 2B and 2C, respectively, or in other embodiments may comprise piezoceramic wafers such as elements 130 depicted in Figures 5A-5D, respectively. Each piezoelectric element 140 of Figure 5 A generates energy subjected to strain as a tire coupled to the vehicle suspension assembly passes over bumps or other variations in the vehicles travel path. [0068] Referring particularly to Figure 7 A, the piezoelectric elements 140 may be electrically connected in series or in parallel and are all coupled to a central energy storage module 142. Energy storage module 142 includes selected power conditioning circuitry, such as described in the example of Figure 3, including an energy storage device such as a capacitor or battery for storing the energy generated by respective piezoelectric elements 140. The single energy storage module 142 is further coupled to an electronics module such as AES 12, such that selected application electronics within AES 12 may receive power stored by energy storage module 142.

[0069] Referring particularly to Figures 7B and 7C, the distributed piezoelectric elements 140 may be electrically connected in series or in parallel and are each respectively coupled to distinct local energy storage modules 142. Each energy storage module 142 includes selected power conditioning circuitry, such as described in the example of Figure 3, including an energy storage device such as a capacitor or battery for storing the energy generated by a respective piezoelectric element 140. Referring to Figure 7B, the multiple storage modules 142 may be connected electrically in series or parallel to deliver energy to a central electronics module such as AES 12, such that selected application electronics within AES 12 may receive power stored by the energy storage modules 142. Alternatively, as in Figure 7C, each of the plurality of energy storage modules 142 may deliver energy to a respective local electronics module, such as AES 12. It should be appreciated that the plurality of local application electronics modules 12 may be distributed in various locations throughout a vehicle suspension assembly and may perform similar functions to one another or may be configured to perform different functions, such as to measure different parameters at distinct respective locations.

[0070] As previously mentioned, AES 12 could comprise a variety of different electronic applications depending on what sort of components are included in the vehicle suspension assembly. A specific example of an application electronic system 12 corresponds to a vehicle suspension monitoring system, such as hereafter discussed with reference to Figure 8. In particular, the vehicle suspension monitoring system of Figure 8 measures various aspects of travel path induced strain and mechanical vibrations within a vehicle suspension and sends the results by means of a radio frequency (RF) transmitter 68 to a remote receiver location. An example of respective transmitter and receiver modules for utilization with aspects of the disclosed technology corresponds to respective TX2 and RX2 brand UHF FM Data Transmitter and Receiver Modules such as offered for sale by Radiometrix Ltd. [0071] A five-volt power signal "V _dd ", ground signal "V _ss ", and an "Active" signal as discussed with reference to Figure 4 are preferably provided from PGD 14 to a microcontroller 70 by way of lines 64, 66, and 58, respectively. An example of a suitable microcontroller for use with the disclosed technology is a Microchip brand PIC16LF87628- pin CMOS RISC microcontroller. Microcontroller 70 is activated when power is applied at input path 64 and then applies power to both temperature sensor 72 and pressure sensor 74 (as well as any additional sensors or appropriate electronic devices in AES 12). An example

of a temperature sensor 72 suitable for utilization with the disclosed technology is a LM50 SOT-23 Single-Supply Centigrade Temperature Sensor such as offered for sale by National Semiconductor. An example of a pressure sensor 74 suitable for utilization with the disclosed technology is a Model 1471 PC Board Mountable Pressure Sensor such as offered for sale by ICSensors and Measurement Specialties Inc. Sensors 76, 78 and 80, respectively, may measure characteristics of the vehicle suspension assembly corresponding, for example, to induced strain and mechanical vibrations in three dimensions of the vehicle suspension assembly.

[0072] Yet another component of the exemplary AES 12 embodiment of Figure 8 corresponds to a rechargeable battery 81 that may also be configured to receive electric charge generated within piezoelectric structure 28 of PGD 14 and to store additional energy for the integrated electronics. Energy stored in battery 81 can typically be stored for a much longer period of time than in other storage devices such as exemplary capacitor 48. Energy stored in battery 81 can be provided to microcontroller 70 when not enough power is generated by actuation of the piezoelectric device. Such a situation could occur, for instance, when the vehicle is stationary. For example, stored energy may be needed to power AES 12 when maintenance personnel may wish to obtain vehicle related information as may be store in a memory associated with microprocessor 70. Also, battery 81 may serve to provide power to AES 12 such that information for managing vehicle maintenance is available when the vehicle is stationary.

[0073] With further reference to the exemplary TES 12 embodiment of Figure 5, microcontroller 70 preferably includes an analog-to-digital [AfD) converter that receives information from sensors 72 through 80, respectively, and converts it to digital information. Microcontroller 70 also comprises memory, preferably non-volatile EEPROM, which stores a unique identification tag that provides sufficient information to identify the vehicle as well as various vehicle components including suspension components. Once the desired information, such as that provided by sensors 72 through 80 respectively, is acquired by microcontroller 70 and converted to digital information, microcontroller 70 preferably shuts off power to the sensors and turns on power to RF transmitter 68 at lines 82 and 84 respectively. The desired digitized information is then output on data line 86 to RF transmitter 68, where the data is modulated onto an FM carrier signal and transmitted via antenna 88 to a remote receiver location.

[0074] A vehicle employing vehicle suspension assemblies with self-powered electronics in accordance with the present subject matter are preferably equipped with a single receiver for obtaining the wirelessly transmitted information from each monitored point of the vehicle suspension. Figure 9 provides a block diagram representation of an exemplary remote receiver configuration 90 in accordance with the present subject matter. Receiver antenna 92 facilitates receipt of information transmitted from each wheel assembly and relays the information to RF receiver 94, where the received information is demodulated from its carrier signal and provided on path 96 to signal processor 98. A carrier detection signal is also provided from RF receiver 94 to signal processor 98 via signal path 100. The data outputted from RF receiver 94 and the carrier detection signal are preferably multiplied together in signal processor 98 such that a signal without spurious noise is obtained. This data signal with reduced error probability is then preferably routed to a driver circuit that converts the digital signal to a signal with voltage levels suitable for transmission via an RS232 interface 102 to a host computer 104. Terminal emulation software is preferably provided at host computer 104 such that the data received via RS232 interface 102 is converted to information readily usable by an end user, such as that provided on a readable display module or usable in connection with control functions as may be desirable in connection with automated adjustments to selected components of the vehicle suspension assembly. Such automated adjustments may provide adjustment of off road handling of a vehicle or suspension adjustment system for fully loaded vehicles such as earthmover dump trucks. [0075] While the present subject matter has been described in detail with respect to specific embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing may readily produce alterations to, variations of and equivalents to such embodiments. Accordingly, the scope of the present disclosure is by way of example rather than by way of limitation, and the subject disclosure does not preclude inclusion of such modifications, variations and/or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art.