Flexible sensors and sensor systems

Abstract

Sensor systems are described that are designed to be integrated with gloves for the human hand. An array of sensors detects forces associated with action of a hand in the glove, and associated circuitry generates corresponding control information that may be used to control a wide variety of processes and devices.

Description

BACKGROUND

Demand is rapidly rising for technologies that bridge the gap between computing devices and the physical world. These interfaces typically require some form of sensor technology that translates information from the physical domain to the digital domain. The “Internet of Things” contemplates the use of sensors in a virtually limitless range of applications, for many of which conventional sensor technology is not well suited.

SUMMARY

According to various implementations, sensors and applications of sensors are provided. According to some implementations, a sensor system includes a flexible substrate for alignment or integration with a portion of a glove. A plurality of conductive trace groups formed directly on the substrate at sensor locations correspond to at least some finger joints of a human hand. Each of the conductive trace groups includes two or more conductive traces. The resistance between the conductive traces in each of the conductive trace groups varies with force on piezoresistive material in contact with the conductive trace group. Circuitry is configured to receive a signal from each of the conductive trace groups and generate control information in response thereto. The control information represents the force on the piezoresistive material in contact with each of the conductive trace groups.

According to a particular class of implementations, the flexible substrate is a dielectric material, and the piezoresistive material is a plurality of patches. Each patch of piezoresistive material is in contact with a corresponding one of the conductive trace groups at the sensor locations. According to a more specific implementation, the dielectric material is a thermoplastic material, and the sensor system includes a second flexible substrate of the thermoplastic material. The flexible substrate on which the conductive trace groups are formed, the patches of piezoresistive material, and the second flexible substrate are thermally bonded together such that the patches of piezoresistive material are secured in contact with the corresponding conductive trace groups.

According to another class of implementations, the flexible substrate is the piezoresistive material which may be, for example, a piezoresistive fabric.

A further understanding of the nature and advantages of various implementations may be realized by reference to the remaining portions of the specification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows examples of trace patterns that may be integrated with a flexible substrate.

FIG. 2 shows examples of different types of distortions to a flexible substrate.

FIG. 3 shows a particular implementation of a sensor array.

FIG. 4 is a simplified block diagram of sensor circuitry suitable for use with various implementations.

FIG. 5 shows examples of relationships among a piezoresistive substrate, conductive traces, and other conductive elements in one-sided and two-sided sensor implementations.

FIG. 6 shows another implementation of a sensor array.

FIG. 7 shows another implementation of a sensor array.

FIG. 8 shows an example of a cross-section of some of the components of a sensor system.

FIG. 9 shows an example of a sensor array integrated with a glove blank.

FIG. 10 shows another implementation of a sensor array.

FIG. 11 shows another implementation of a sensor array.

FIGS. 12-14C show another implementation of a sensor system.

FIGS. 15 and 16 show another implementation of a sensor system.

DETAILED DESCRIPTION

Sensors and sensor systems incorporating piezoresistive materials are described in this disclosure. In particular, sensor systems for integration with gloves for the human hand are described. Specific implementations are described herein including the best modes contemplated. Examples of these implementations are illustrated in the accompanying drawings. However, the scope of this disclosure is not limited to the described implementations. Rather, this disclosure is intended to cover alternatives, modifications, and equivalents of these implementations. In the following description, specific details are set forth in order to provide a thorough understanding of the described implementations. Some implementations may be practiced without some or all of these specific details. In addition, well known features may not have been described in detail to promote clarity.

Piezoresistive materials include any of a class of materials that exhibit a change in electrical resistance in response to mechanical force or pressure applied to the material. One class of sensor systems described herein includes conductive traces formed directly on or otherwise integrated with a flexible substrate of piezoresistive material, e.g., a piezoresistive fabric or other flexible material. Another class of sensor systems described herein includes conductive traces formed directly on or otherwise integrated with a flexible dielectric substrate with flexible piezoresistive material that is tightly integrated with the dielectric substrate and in contact with portions of the traces. When force or pressure is applied to such a sensor system, the resistance between traces connected by the piezoresistive material changes in a time-varying manner that is representative of the applied force. A signal representative of the magnitude of the applied force is generated based on the change in resistance. This signal is captured via the conductive traces (e.g., as a voltage or a current), digitized (e.g., via an analog-to-digital converter), processed (e.g., by an associated processor, controller, or suitable control circuitry), and mapped (e.g., by the associated processor, controller, or control circuitry) to a control function that may be used in conjunction with virtually any type of process, device, or system. The output signals from such sensor systems may also be used to detect a variety of distortions and/or deformations of the substrate(s) on which they are formed or with which they are integrated such as, for example, bends, stretches, torsions, rotations, etc.

Printing, screening, depositing, or otherwise forming conductive traces directly onto flexible substrates allows for the creation of a sensor or sensor array that fits any arbitrary shape or volume. The piezoresistive material on which the traces are formed or with which the traces are in contact may be any of a variety of woven and non-woven fabrics having piezoresistive properties. Implementations are also contemplated in which the piezoresistive material may be any of a variety of flexible, stretchable, or otherwise deformable materials (e.g., rubber, or a stretchable fabric such as spandex or open mesh fabrics) having piezoresistive properties. The conductive traces may be formed on the piezoresistive material or a flexible dielectric substrate using any of a variety of conductive inks or paints. Implementations are also contemplated in which the conductive traces are formed using any flexible conductive material that may be formed on a flexible substrate. It should therefore be understood that, while specific implementations are described with reference to specific materials and techniques, the scope of this disclosure is not so limited.

Both one-sided and two-side implementations are contemplated, e.g., conductive traces can be printed on one or both sides of flexible substrate. As will be understood, two-sided implementations may require some mechanism for connecting conductive traces on one side of the substrate to those on the other side. Some implementations use vias in which conductive ink or paint is flowed through the vias to establish the connections. Alternatively, metal vias or rivets may make connections through the flexible substrate.

Both single and double-sided implementations may use insulating materials formed over conductive traces. This allows for the stacking or layering of conductive traces and signal lines, e.g., to allow the routing of signal line to isolated structures in a manner analogous to the different layers of a printed circuit board.

Routing of signals on and off the flexible substrate may be achieved in a variety of ways. A particular class of implementations uses elastomeric connectors (e.g., ZEBRA® connectors) which alternate conductive and non-conductive rubber at a density typically an order of magnitude greater than the width of the conductive traces to which they connect (e.g., at the edge of the substrate). Alternatively, a circuit board (possibly made of a flexible material such as Kapton), or a bundle of conductors may be riveted to the substrate. The use of rivets may also provide mechanical reinforcement to the connection.

Matching conductive traces or pads on both the flexible substrate and a circuit board can be made to face each. A layer of conductive adhesive (e.g., a conductive epoxy such as Masterbond EP79 from Masterbond, Inc. of Hackensack, N.J.) can be applied to one of the surfaces and then mated to the other surface. The conductive traces or pads can also be held together with additional mechanical elements such as a plastic sonic weld or rivets. If conductive rivets are used to make the electrical connections to the conductive traces of the flexible substrate, the conductive adhesive may not be required. Conductive threads may also be used to connect the conductive traces of the flexible substrate to an external assembly.

According to a particular class of implementations, the piezoresistive material is a pressure sensitive fabric manufactured by Eeonyx, Inc., of Pinole, Calif. The fabric includes conductive particles that are polymerized to keep them suspended in the fabric. The base material is a polyester felt selected for uniformity in density and thickness as this promotes greater uniformity in conductivity of the finished piezoresistive fabric. That is, the mechanical uniformity of the base material results in a more even distribution of conductive particles when the slurry containing the conductive particles is introduced. The fabric may be woven. Alternatively, the fabric may be non-woven such as, for example, a calendared fabric e.g., fibers, bonded together by chemical, mechanical, heat or solvent treatment. For implementations in which conductive traces are formed on the piezoresistive fabric, calendared material presents a smoother outer surface which promotes more accurate screening of conductive inks than a non-calendared material.

The conductive particles in the fabric may be any of a wide variety of materials including, for example, silver, copper, gold, aluminum, carbon, etc. Some implementations may employ carbon graphenes that are formed to grip the fabric. Such materials may be fabricated using techniques described in U.S. Pat. No. 7,468,332 for Electroconductive Woven and Non-Woven Fabric issued on Dec. 23, 2008, the entire disclosure of which is incorporated herein by reference for all purposes. However, it should again be noted that any flexible material that exhibits a change in resistance or conductivity when force or pressure is applied to the material will be suitable for implementation of sensors as described herein.

According to a particular class of implementations, conductive traces having varying levels of conductivity are formed on flexible piezoresistive material or an adjacent flexible dielectric substrate using conductive silicone-based inks manufactured by, for example, E.I. du Pont de Nemours and Company (DuPont) of Wilmington, Del., and/or Creative Materials of Ayer, Mass. An example of a conductive ink suitable for implementing highly conductive traces for use with various implementations is product number 125-19 from Creative Materials, a flexible, high temperature, electrically conductive ink. Examples of conductive inks for implementing lower conductivity traces for use with various implementations are product numbers 7102 and 7105 from DuPont, both carbon conductive compositions. Examples of dielectric materials suitable for implementing insulators for use with various implementations are product numbers 5018 and 5036 from DuPont, a UV curable dielectric and an encapsulant, respectively. These inks are flexible and durable and can handle creasing, washing, etc. The degree of conductivity for different traces and applications is controlled by the amount or concentration of conductive particles (e.g., silver, copper, aluminum, carbon, etc.) suspended in the silicone. These inks can be screen printed or printed from an inkjet printer. Another class of implementations uses conductive paints (e.g., carbon particles mixed with paint) such as those that are commonly used for EMI shielding and ESD protection.

Examples of sensors and arrays of sensors that may be used with various implementations enabled by the present disclosure are described in U.S. patent application Ser. No. 14/299,976 entitled Piezoresistive Sensors and Applications filed on Jun. 9, 2014, the entire disclosure of which is incorporated herein by reference for all purposes. However, it should be noted that implementations are contemplated that employ a variety of other suitable sensor technologies.

Forming sensors on flexible substrates enables numerous useful devices. Many of these devices employ such sensors to detect the occurrence of touch events, the force or pressure of touch events, the duration of touch events, the location of touch events, the direction of touch events, and/or the speed of motion of touch events. The output signals from such sensors may also be used to detect a variety of distortions and/or deformations of the substrate on which they are formed or with which they are integrated such as, for example, bends, stretches, torsions, rotations, etc. The information derived from such sensors may be used to effect a wide variety of controls and/or effects. Examples of distortions and/or deformations are described below with reference to the accompanying figures. As will be understood, the specific details described are merely examples for the purpose of illustrating the range of techniques enabled by this disclosure.

FIG. 1 shows an example of a sensor trace pattern 100 integrated with a flexible substrate 102. The flexible substrate may be a piezoresistive material or a dielectric material. In the latter case, a flexible piezoresistive material is tightly integrated with the dielectric material and in contact with the sensor trace pattern. Trace pattern 100 includes a pair of conductive traces, one of which (trace 104) provides a sensor signal to associated circuitry (not shown), and the other of which (trace 106) is connected to ground or a suitable reference. Some representative examples of other trace patterns 108-116 are shown. In some implementations, the traces of a trace pattern may be formed directly, e.g., by screening or printing, on the flexible substrate which might be, for example, a piezoresistive fabric. However, it should be noted that, among other things, the geometries of the sensor trace pattern(s), the number of traces associated with each sensor, the number, spacing, or arrangement of the sensors, the relationship of the sensors to the substrate, the number of layers or substrates, and the nature of the substrate(s) may vary considerably from application to application, and that the depicted configurations are merely examples for illustrative purposes.

FIG. 2 shows examples of different types of distortions to flexible substrate 102 that may be detected via sensor trace pattern 100. FIG. 2(a) shows substrate 102 in its non-distorted state. FIG. 2(b) shows a side view of substrate 102 bending; FIG. 2(c) shows substrate 102 stretching; FIG. 2(d) represents substrate 102 rotating relative to surrounding material; and FIG. 2(e) shows a side view of substrate 102 twisting due to an applied torque (i.e., torsion). In each of these scenarios, the resistance of the piezoresistive material in contact with trace pattern 100 changes in response to the applied force (e.g., goes down or up due to compression or increased separation of conductive particles in the piezoresistive material). This change (including its magnitude and time-varying nature) is detectable via sensor trace pattern 100 and associated electronics (not shown).

According to a particular implementation illustrated in FIG. 3, sensor trace patterns are formed on the stretchable material of a sensor glove 300 that may be used, for example, to translate a human's hand motions and the hand's interactions with the physical world into a virtual representation of the hand (or some other virtual object) and its interactions in a virtual environment. In another example, the hand's motions and interactions may be used to control a robotic hand or device in the physical world. The material on which the trace patterns are formed may be a flexible piezoresistive material or a flexible dielectric material. Again, in the latter case, a flexible piezoresistive material is tightly integrated with the flexible substrate on which the trace patterns are formed and in contact with the trace patterns at the various sensor locations (i.e., S1-S19).

As shown, trace patterns corresponding to some of the sensors (e.g., S1-S5 and S14-S18) are placed to coincide with various joints of the fingers (e.g., knuckles or finger joints) to capture distortion and/or deformation of the glove in response to bending and flexing of those joints. Other sensors (e.g., S6-S13 and S19) are placed to capture stretching of the glove, e.g., as occurs when the fingers of the hand are spread out. Other sensors (not shown) may also be placed on the palm of the glove and/or the tips of the fingers to detect bending and flexing forces as well as forces relating, for example, to touching, gripping, or otherwise coming into contact with objects or surfaces.

Portions of the conductive traces that are not intended to be part of a sensor (e.g., signal routing traces) may be shielded or insulated to reduce any unwanted contributions to the sensor signals. That is, the portions of the conductive traces that bring the drive and sense signals to and from the sensors may be insulated from the piezoresistive material using, for example, a dielectric or non-conducting material between the piezoresistive material and the conductive traces. According to some implementations in which the conductive traces are formed on a flexible dielectric material, isolated pieces of piezoresistive material may be selectively located at the respective sensor locations.

In the depicted implementation there are 19 sensors, S1-S19. Each of the sensors includes two adjacent traces, the respective patterns of which include extensions that alternate. See, for example, the magnified view of sensor S4. One of the traces 301 receives a drive signal; the other trace 302 transmits the sensor signal to associated sensor circuitry (not shown). The drive signal might be provided, for example, by connecting the trace (permanently or temporarily) to a voltage reference, a signal source that may include additional information in the drive signal, a GPIO (General Purpose Input Output) pin of an associated processor or controller, etc. And as shown in the example in FIG. 3, the sensor signal might be generated using a voltage divider in which one of the resistors of the divider includes the resistance between the two traces through the intervening piezoresistive material. The other resistor (represented by R1) might be included, for example, with the associated sensor circuitry. As the resistance of the piezoresistive material changes with applied force or pressure, the sensor signal also varies as a divided portion of the drive signal.

The sensors are energized (via the drive signals) and interrogated (via the sensor signals) to generate an output signal for each that is a representation of the force exerted on that sensor. As will also be appreciated, and depending on the application, implementations are contemplated having more or fewer sensors.

According to various implementations, different sets of sensors may be selectively energized and interrogated thereby reducing the number and overall area of traces on the substrate, as well as the required connections to sensor circuitry on an associated PCB (which may be positioned, for example, in cutout 322). For example, in the sensor system of FIG. 3, the 19 sensors are driven via 11 drive signal outputs from the sensor circuitry (not shown), and the sensor signals are received via 2 sensor signal inputs to the sensor circuitry; with 13 connections between the flexible substrate on which the conductive traces are formed and the PCB in cutout 322 as shown. The set of sensors providing sensor signals to one of the 2 sensor signal inputs (e.g., S6-S13 in one set and S1-S5 and S14-S19 in the other) may be energized in any suitable sequence or pattern such that any signal received on the corresponding sensor signal input can be correlated with the corresponding sensor drive signal by the sensor circuitry.

And because the sensor signals in this implementation are received by the sensor circuitry via two different sensor signal inputs, two sensors can be simultaneously energized as long as they are connected to different sensor signal inputs to the sensor circuitry. This allows for the sharing of drive signal lines. For example, in the implementation of FIG. 3, eight pairs of sensors share a common drive signal line, i.e., S2 and S8, S3 and S10, S4 and S12, S6 and S14, S7 and S15, S9 and S16, S11 and S17, and S13 and S19. The sharing of the common drive signal lines may be enabled by insulators which allow the conductive traces to cross, as well as locations at which the conductive traces simply diverge. Other suitable variations on this theme will be understood by those of skill in the art to be within the scope of this disclosure.

According to some implementations, a PCB may be connected to the conductive traces of the sensor array as described U.S. patent application Ser. No. 14/671,821 entitled Flexible Sensors and Applications filed on Mar. 27, 2015, the entire disclosure of which is incorporated herein by reference for all purposes. According to other implementations, any of a variety of techniques may be employed to make such a connection including, for example, elastomeric connectors (e.g., ZEBRA® connectors) which alternate conductive and non-conductive rubber at a density typically an order of magnitude greater than the width of the conductive traces to which they connect (e.g., at the edge of the fabric). A variety of other suitable alternatives are available to those of skill in the art.

FIG. 4 is a simplified diagram of sensor circuitry that may be provided on a PCB for use with implementations described herein. For example, in the implementation described above with reference to FIG, 3, such sensor circuitry could be provided on a PCB in cutout 322 and connected to the conductive traces associated with sensors S1-S19. When force is applied to one of the sensors, a resulting signal (captured via the corresponding traces) is received and digitized (e.g., via multiplexer 402 and A-D converter 404) and may be processed locally (e.g., by processor 406) and/or transmitted to a connected device (e.g., via a Bluetooth or other wireless connection, or even via a USB connection). The sensors may be selectively energized by the sensor circuitry (e.g., under the control of processor 406 via D-A converter 408 and multiplexer 410) to effect the generation of the sensor signals. The C8051F380-GM controller (provided by Silicon Labs of Austin, Tex.) is an example of a processor suitable for use with various implementations.

In addition to transmission of data to and from a connected device, power may be provided to the sensor circuitry via a USB connection. Alternatively, systems that transmit data wirelessly (e.g., via Bluetooth) may provide power to the sensor circuitry using any of a variety of mechanisms and techniques including, for example, using one or more batteries, solar cells, and/or mechanisms that harvest mechanical energy. The LTC3588 (provided by Linear Technology Corporation of Milpitas, Calif.) is an example of an energy harvesting power supply that may be used with at least some of these diverse energy sources. Other suitable variations will be appreciated by those of skill in the art. And as will be appreciated, the sensor circuitry shown in FIG. 4 is merely an example. A wide range of sensor circuitry components, configurations, and functionalities are contemplated.

Both one-sided and two-side implementations are contemplated, e.g., conductive traces can be formed on one or both sides of a flexible substrate. As will be understood, two-sided implementations may require some mechanism for connecting conductive traces on one side of the substrate to those on the other side. Some implementations use vias in which conductive ink or paint is flowed through the vias to establish the connections. Alternatively or additionally, metal vias or rivets may make connections through the substrate. FIG. 5 illustrates the use of vias or rivets through the flexible substrate (e.g., configuration 502), and the use of insulating materials to insulate conductive traces from the substrate where the substrate is a piezoresistive material (e.g., configuration 504). Such mechanisms enable complex patterns of traces and routing of signals in a manner analogous to the different layers of a PCB.

For example, assuming an implementation in which the conductive traces are formed on piezoresistive material and referring again to FIG. 3, conductive traces that transmit signals to and from the sensors of glove 300 may be insulated from the underlying piezoresistive substrate by an insulating material. This is most clearly illustrated in the figure by insulators 304 and 306 that are associated with the drive and sense signal lines connected to sensor S4. In addition, sense signal lines from multiple sensors are connected to each other on the opposite side (not shown) of the material depicted in FIG. 3 through the use of vias at locations 310-318.

According to a particular implementation of a sensor glove and as shown in FIG. 6, sensor trace patterns (e.g., 601-604) may be placed in a roughly cylindrical configuration around the wrist to detect bending of the wrist in two dimensions (e.g., up, down, left, right). When all four sensors register a similar response, this could mean that the wrist is twisting. However, this configuration may not provide sufficient information to determine the direction of the twist. Therefore, according to a particular implementation, an outer cylinder 608 may be attached to an inner cylinder 610 with at least two stretch sensors (e.g., 612 and 614). By comparison of the outputs of these stretch sensors, the direction (e.g., 616) as well as the amount of the rotation can be captured.

FIG. 7 illustrates particular class of implementations of a sensor array 700 for use in a sensor glove in which conductive traces are formed on a flexible dielectric substrate 702. Operation of sensor array 700 is similar to operation of the sensor array of sensor glove 300 as described above. And it should be noted that the depicted configuration of traces might also be included in implementations in which the traces are formed on piezoresistive material.

According to a particular implementation, substrate 702 may be constructed from a thermoplastic polyurethane (TPU) material such as, for example, Products 3415 or 3914 from Bemis Associates Inc. of Shirley, Mass. The conductive traces may be screen printed on the substrate using a conductive flexible ink such as, for example, conductive silicone-based inks manufactured by E.I. du Pont de Nemours and Company (DuPont) of Wilmington, Del., or Creative Materials of Ayer, Mass. Patches of a piezoresistive material (e.g., the Eeonyx fabric discussed above) are placed in contact with the conductive traces at the locations of sensors S1-S14. See for example, piezoresistive patch 704 at sensor S4. A second substrate of the TPU material (not shown) is placed over array 700, and the assembly is heated to thermally bond the components together, fixing the piezoresistive patches in contact with their respective sensor traces.

The relationships of the components of this assembly may be understood with reference to FIG. 8 which shows a flexible substrate 802 on which a conductive trace 804 is formed. Piezoresistive material 806 is maintained in contact with trace 804 by a second flexible substrate 808. In the depicted example, substrates 802 and 808 are TPU substrates and trace 804 is a conductive ink that is screen printed on TPU substrate 802. According to a particular implementation, TPU substrate 802 has an adhesive-barrier-adhesive (ABA) structure that allows for the assembly to be thermally bonded (e.g., melted) to another substrate such as, for example, a fabric glove blank 900 as depicted in FIG. 9. The other TPU substrate 808 is shown an adhesive-barrier (AB) structure so that it only bonds to the assembly. However, implementations are contemplated in which this substrate has an ABA structure to enable thermal bonding on both sides of the assembly.

According to a more specific implementation, stiffeners (not shown) may be placed in alignment with at least some of the piezoresistive patches and the corresponding trace patterns for the purpose of amplifying the signals generated by the corresponding sensors, e.g., by the force of the stiffener resisting bending of a knuckle and compressing the piezoresistive material. A stiffener might be a plastic film (e.g., polyethylene terephthalate or PET). Alternatively, a stiffener may be another piece of fabric. As yet another alternative, a stiffening material such as DuPont 5036 Dielectric ink may be silk-screened or printed on one of the components of the stack. As will be appreciated, stiffeners may be inserted at any point in the stack of materials (e.g., as depicted in FIG. 8) as long as the electrical connection between the conductive traces and the piezoresistive material is not unduly degraded.

Referring back to FIG. 7, a stiffener 706 (e.g., of PET or other suitable material) may be adhered to substrate 702 near the terminations of the conductive traces to allow for the insertion of the assembly into a connector 708 (see the exploded view in the lower right hand corner of the drawing). As will be appreciated, with stiffener 706 and the appropriate conductor spacing, this configuration allows for connection of sensor array 700 to any of a wide variety of industry standard connectors. According to a particular implementation, connector 708 is a Molex ZIF flat flex connector such as, for example, the Molex connector 52207-2860 (a 28 position connector) or the Molex connector 0522710869 (an 8 position connector as shown in FIG. 11).

As discussed above, sensor glove implementations are contemplated in which sensors are placed on the palm of the glove and/or the tips of the fingers to detect, for example, touching, gripping, or otherwise coming into contact with objects or surfaces. An example of how such a sensor might be integrated with an array is shown in FIG. 10. In the depicted example, flexible substrate 1002 extends beyond sensor S4 and includes a tab 1004 on which the conductive traces of sensor S15 are formed. Tab 1004 can be wrapped around inside the glove (as indicated by the arrow) so that it coincides with the fingertip of the glove. Thus, any forces acting on the fingertip of the glove (e.g., by virtue of the fingertip coming into contact with a surface) will be detected by sensor S15. As will be appreciated, such sensors may be integrated with a sensor array for the back of the hand as shown in FIG. 10. Alternatively, such sensors may be implemented as separate array for the palm and fingertips.

FIG. 11 shows an alternative design for a sensor array 1100 for use in a sensor glove which includes only four elongated sensors; S1-S3 for the three middle fingers, and S4 for the thumb. As will be appreciated, this simpler design may be easier and/or cheaper to manufacture and may be sufficient or even more well-suited for some applications than the designs described above with reference to FIGS. 3 and 7. Nevertheless, sensor array 1100 operates similarly to the sensor arrays described and may be constructed using either approach. According to a particular implementation, substrate 1102 is constructed from a TPU material and the conductive traces are screen printed on substrate 1102 using a conductive flexible ink as described above with reference to FIGS. 7 and 8. Patches of a piezoresistive material (e.g., the Eeonyx fabric discussed above) are placed in contact with the conductive traces at the locations of sensors S1-S4. See for example, piezoresistive patch 1104 at sensor S3. A second substrate of the TPU material (not shown) is placed over array 1100, and the assembly is heated to thermally bond the components together, fixing the piezoresistive patches in contact with their respective sensor traces.

As with sensor array 700, a stiffener (not shown) may be adhered to substrate 1102 near the terminations of the conductive traces to allow for the insertion of the assembly into a connector 1108. As discussed above, use of the stiffener allows for connection of sensor array 1100 to any of a wide variety of industry standard connectors including, for example, the Molex connector 0522710869. Also as discussed above with reference to sensor array 700, stiffeners (not shown) may be placed in alignment with at least some of the piezoresistive patches and the corresponding trace patterns of sensor array 1100 for the purpose of amplifying the signals generated by the corresponding sensors.

FIGS. 12-14C illustrate another class of implementations for use in a sensor glove. Referring to the partially exploded view of FIG. 12, sensor system 1200 includes five digit assemblies 1202 (one for each finger or digit of the hand) and four abductor assemblies 1204 (one for each space between each pair of adjacent digits). These assemblies are connected to a circuit board 1206 on which is implemented the circuitry (not shown) for energizing and reading signals from the knuckle sensors and abductor sensors on each assembly. Digit assemblies 1202 are interconnected via substrate 1208 and abductor assemblies 1204 are interconnected via substrate 1210. Substrates 1208 and 1210 are secured to opposite sides of circuit board 1206 to form sensor system 1200. Conductors on substrates 1208 and 1210 provide connections between conductors on digit assemblies 1202 and abductor assemblies 1204 and corresponding conductors on circuit board 1206 (not shown). Sensor system 1200 is secured by top enclosure 1209 and ergonomic back plate 1211 and is aligned with the back of a hand inserted in a sensor glove 1300 as illustrated in FIG. 13.

Each digit assembly 1202 includes two knuckle sensors, each knuckle sensor being formed using a strip of piezoresistive material 1212 (e.g., a fabric) in contact with a group of sensor traces (obscured by material 1212 in FIG. 12) on the surface of a flexible dielectric substrate 1214. Routing traces 1216 by which signals are transmitted to and received from the individual sensors are adjacent the opposite surface of substrate 1214 from the sensor trace groups (i.e., the underside of substrate 1214 in the figure). Routing traces 1216 are connected to the sensor traces through substrate 1214, e.g., using vias. Substrate 1214 is depicted as being transparent so that routing traces 1216 on its underside are at least partially visible. Each knuckle sensor generates a sensor signal that represents the degree of bend in the corresponding knuckle.

Each abductor assembly 1204 includes one abductor sensor formed using a strip of piezoresistive material 1218 (only one of which is shown in FIG. 12), e.g., a fabric, in contact with a group of sensor traces 1219 (one set of which is obscured by material 1218) on the surface of a flexible dielectric substrate 1220. Routing traces (not shown) by which signals are transmitted to and received from the abductor sensor are adjacent the opposite surface of substrate 1220 from the sensor trace group (i.e., the underside of substrate 1220 in the figure). The routing traces are connected to sensor traces 1219 through substrate 1220, e.g., using vias. Each abductor sensor generates a sensor signal that represents the spread angle between two adjacent digits. The orientation of sensor system 1200 within a glove may be understood with reference to FIG. 13.

As shown in FIG. 13, each digit assembly 1302 extends along the back of the glove and along one of the corresponding fingers (referring to the thumb as one of the fingers). As a particular finger bends, the degree of bend of its knuckles are represented by the sensor signals generated by the corresponding knuckle sensors. And as will be understood from the figure, when the fingers of the hand are together, the portion of each abductor assembly 1304 including the abductor sensor is bent back on itself almost 180 degrees (e.g., like a taco shell or a “v”) with the center line of the bend being aligned with the crux of the two corresponding adjacent digits. The abductor sensor is considered to be “at rest” in this position. As the fingers are spread apart, the abductor sensor flattens out and stretches, generating a corresponding sensor signal representing the spread angle.

The individual sensors on the digit and abductor assemblies may be energized and interrogated as described above with reference to FIG. 3 using sensor circuitry such as that described with reference to FIG. 4. That is, each of the sensors includes two traces. One of the traces receives a drive signal, and the other transmits the sensor signal to the sensor circuitry. As discussed above, the sensor signal may be generated using a voltage divider in which one of the resistors of the divider includes the resistance between the two traces through the intervening piezoresistive material, and the other is included with the sensor circuitry. As the resistance of the piezoresistive material changes with applied force or pressure, the sensor signal also varies as a divided portion of the drive signal.

And as will be understood, the responses of the individual sensors in sensor systems enabled by the present disclosure may exhibit variation relative to each other as well as the corresponding sensors in similar systems. According to some implementations, calibrated sensor data are stored (e.g., in memory 407 of processor 406) that represent the response of each of the sensors. Such data ensure consistency and accuracy in the way the sensor outputs are processed and used to represent the motion and articulation of the parts of the hand. During calibration, the output of each sensor (e.g., as captured by ADC 404) is measured for a range of known input forces corresponding to specific positions of the hand. In this way, a set of data points for each sensor is captured (e.g., in a table in memory 407) associating ADC values with corresponding finger positions. The data set for each sensor may capture a value (or an offset value) for many (or even every) of the possible values of the ADC output. Alternatively, fewer data points may be captured and the sensor circuitry may use interpolation to derive force values for ADC outputs not represented in the data set.

The calibration data for each abductor sensor represent a range of the spread of the corresponding pair of fingers with a range of data values. The calibration data for each knuckle sensor represent a range of the bend of the corresponding knuckle with a range of data values. According to a particular implementation, calibration involves holding the hand in various positions and storing data values for those positions. For example, the user might be instructed (e.g., in a video or animation) to hold her hand out relaxed with the fingers together, make a fist, spread the fingers out, etc. Data values for each sensor may then be captured for each position.

According to a particular implementation, the calibration data capture two positions of the range for each sensor. These positions may be, for example, at the extreme ends of each range. For example, for an abductor sensor, the two positions might be (1) the pair of fingers together and (2) the pair of fingers spread apart as far as possible. Similarly, for a knuckle sensor, the two positions might be (1) the knuckle straight and (2) the knuckle bent as far as possible. Interpolation (e.g., linear interpolation) is then used at run time to determine positions in the range between the extremes for each knuckle and abductor sensor. These calibration data can be stored across sessions. And because such data can be user-specific, this might include the storing of multiple sets; one for each unique user. Alternatively, the calibration data can be regenerated for each session, e.g., by running the user through the various hand positions of the calibration routine.

According to some implementations, the sensor circuitry on circuit board 1206 includes an inertial measurement unit (IMU) (not shown) that includes a 3-axis accelerometer, a 3-axis gyroscope, and a 3-axis magnetometer. The information from these components is blended by the IMU to give the attitude of the hand, i.e., pitch, roll, and yaw. Translation, i.e., movement of the hand in x, y, and z, may be tracked using one or more cameras (e.g., gaming system cameras), one or more ultrasonic sensors, one or more electromagnetic sensors, etc., to determine the position of the glove in space. Thus, using the information generated by the sensor system, the IMU, and any translation sensing system, the position, attitude, and finger articulations of the user's hand can be captured. An example of an IMU that may be employed with various implementations is the BNO055 provided by Bosch Sensortec GmbH of Reutlingen/Kusterdingen, Germany. Other examples of suitable IMUs are provided by InvenSense, Inc. of San Jose, Calif., and ST Microelectronics of Geneva, Switzerland.

In the implementation depicted in FIG. 12, each digit assembly also includes a haptic actuator (not shown for clarity) which is connected to its own set of routing traces (partially visible) via pads 1224. The haptic actuators are aligned with each fingertip for the purpose of creating the sensation that the fingertip is in contact with an object or a surface (e.g., in a virtual space or at a remote location) thereby giving the user a sense of feel. Because sensor system 1200 is aligned with the back of the hand, the haptic actuators are connected to pads 1224 via conductors (not shown) that wrap around the finger.

According to a particular implementation, each actuator is a flexible metal membrane (e.g., a kapton-mylar film) stretched over a rigid substrate. The membrane shrinks or expands based on a voltage applied by the sensor circuitry via pads 1224. The haptic actuators can be thought of as tiny “speakers” that are driven with different waveforms to simulate different surfaces, signaling that the fingers have contacted something in the virtual world or at the remote location. The waveforms for these contact events depend on the nature of the surface being simulated, the number of fingertips contacting the surface, the rate of movement across the virtual surface, etc. In some cases, accompanying audio may be provided to enhance the perception of the contact. Examples of haptic actuators that may be used with various implementations include those provided by Novasentis Inc. of Berkeley, Calif.

FIGS. 14A-14C show a stack of components of a sensor system that includes the knuckle sensors and haptic actuators. The components relating to the abductor sensors are not shown for clarity. However, it will be understood that the abductor assemblies may be formed similarly to the depicted digit assemblies in terms of the materials and the ordering of the components (without the components relating to the haptic actuators).

Referring to FIG. 14A, ergonomic back plate 1402 is shown at the bottom of the stack relative to the orientation of the figure. Back plate 1402 has a curved surface that conforms to the back of the user's hand. Haptic bus lines 1404 (for connection to the haptic actuators which are not shown) are printed with conductive ink on one side of PET substrate 1406. Sensor bus lines 1408 (including pads for connection to the sensor circuitry circuit board) that are used to energize and read signals from each of the knuckle sensors are printed with conductive ink on the other side of PET substrate 1406.

Referring to FIG. 14B, PET substrates 1410 are placed over sensor bus lines 1408 and PET substrate 1406. Sensor traces 1412 (including some traces to connect to the bus lines) are printed in conductive ink on PET substrates 1410 (and partially on PET substrate 1406 to connect with bus lines 1408). Each parallel pair of traces (e.g., 1413) on PET substrates 1410 corresponds to a knuckle sensor. A carbon passivation layer 1414 is printed over sensor traces 1412, and exposed portions of bus lines 1408 to protect the conductive traces from tarnishing and creeping. Dielectric strips may be placed over portions of the bus traces to insulate them from the sensor traces and the piezoresistive material.

Referring to FIG. 14C, piezoresistive fabric strips 1416 are placed in contact with each pair of sensor traces 1412 to form the knuckle sensors. Each fabric strip 1416 has a PET strip 1418 applied as a stiffener that is secured using pressure sensitive adhesive (PSA) 1420. PET 1418 makes fabric 1416 asymmetrically stiffer, resisting the bend of the fabric, causing it to distort, thereby enhancing the bend signal and helping to achieve the desired sensor response and dynamic range. As will be appreciated, a variety of materials of varying stiffness and/or thickness can be used as stiffeners depending on the desired response and dynamic range. TPU strips 1422 are placed over the knuckle sensors and heated to thermally bond the components together, fixing the piezoresistive strips in contact with their respective sensor traces.

As mentioned above, sensor traces 1412 are printed such that portions of the sensor traces are on PET substrates 1410 and other portions are contacting and connecting with bus lines 1408 on the underlying PET substrate 1406. Connections between sensor traces 1412 and bus lines 1408 may also be made through PET substrate 1406, e.g., using vias. And although the knuckle sensors are depicted as using two parallel traces other trace group configurations are contemplated. For example, sensor traces having interdigitated extensions are employed with some implementations as discussed above. Another example of such an implementation is shown in FIGS. 15 and 16.

FIG. 15 shows the sensor traces and bus lines of a sensor system 1500 without other layers and components so as not to obscure details of these structures. Each of the five digit assemblies 1502 includes four knuckle sensors 1504 as indicated on the digit assembly corresponding to the middle finger. Having two sensors per knuckle may allow for finer detection and/or representation of motion. Four abductor assemblies 1506 are also shown.

According to this class of implementations and as depicted in FIG. 16, bus lines 1602 (which include both sensor and haptic bus lines) are printed in conductive ink on one side of a TPU substrate 1604. Sensor traces 1606 are printed in conductive ink on the other side of TPU substrate 1604 and connected to the corresponding bus lines through TPU substrate 1604, e.g., using vias. This assembly is then placed in contact with piezoresistive fabric, e.g., in the shape of a glove blank (not shown). These components are then heated, securing the sensor traces 1606 to the piezoresistive fabric from which a sensor glove is then made. Abductor assemblies 1608 (of which only the traces are shown) may be similarly constructed. Alternatively, because of their relatively simple structures, abductor assemblies 1608 may be formed on the piezoresistive fabric, e.g., printed using conductive ink and insulators (for the bus lines extending to and from the abductor sensors).

As should be appreciated with reference to the foregoing description, the applications for sensor gloves enabled by the present disclosure are numerous and diverse. As mentioned above, the action of a human hand in such a sensor glove may be translated to control systems, devices, and processes in both the real and virtual worlds. Using a sensor glove, a human can interact with objects in a virtual space, having utility in video and online gaming, as well as educational and artistic applications. For example, a sensor glove may be used to simulate a surgical procedure, playing of a virtual musical instrument, conducting of a virtual orchestra, painting of a virtual work of art, etc. Translation of the movements of a human hand into the virtual world could support more realistic computer aided animation. Industrial applications might include remote control of manufacturing apparatus or robotics handling hazardous materials. As will be appreciated from the diversity of these examples, the range of applications is virtually limitless. The scope of this disclosure should therefore not be limited by reference to specific applications.

It will be understood by those skilled in the art that changes in the form and details of the implementations described herein may be made without departing from the scope of this disclosure. In addition, although various advantages and aspects may have been described with reference to particular implementations, the scope of this disclosure should not be limited by reference to such advantages and aspects.

Claims

1. A sensor array, comprising: a first thermoplastic polyurethane (TPU) substrate;a plurality of conductive traces on the first TPU substrate, the conductive traces including a plurality of sensor traces and a plurality of signal routing traces;piezoresistive fabric thermally bonded to the first TPU substrate such that the piezoresistive fabric is in contact with the sensor traces, the piezoresistive fabric and the sensor traces forming a plurality of sensors, the sensor traces for each sensor being on a same surface of the first TPU substrate; andsensor circuitry configured to selectively activate the sensors via first signal routing traces, and to receive sensor signals from the sensors via second signal routing traces;wherein a first sensor of the plurality of sensors includes a portion of the piezoresistive fabric, a first sensor trace of the plurality of sensor traces, and a second sensor trace of the plurality of sensor traces, the portion of the piezoresistive fabric, the first sensor trace, and the second sensor trace forming part of a voltage divider configured to generate a corresponding one of the sensor signals.

2. The sensor array of claim 1, wherein the piezoresistive fabric comprises a plurality of patches, each of the patches being associated with one of the sensors.

3. The sensor array of claim 1, further comprising a second TPU substrate thermally bonded to the first TPU substrate and the piezoresistive fabric, thereby enclosing the plurality of sensors between the first and second TPU substrates.

4. The sensor array of claim 3, wherein one or both of the first and second TPU substrates is characterized by an adhesive-barrier-adhesive structure such that the sensor array is configured to be thermally bonded to an additional substrate.

5. The sensor array of claim 1, wherein the conductive traces comprise a conductive flexible ink printed on the first TPU substrate.

6. The sensor array of claim 1, wherein the sensor traces are on a first surface of the first TPU substrate facing toward the piezoresistive fabric, and wherein at least some of the signal routing traces are on a second surface of the first TPU substrate facing away from the piezoresistive fabric.

7. The sensor array of claim 1, wherein the sensor circuitry is further configured to process the sensor signals to detect one or more of mechanical force on the piezoresistive fabric, pressure on the piezoresistive fabric, distortion of the piezoresistive fabric, or deformation of the piezoresistive fabric.

8. The sensor array of claim 1, wherein the sensor circuitry is further configured to process the sensor signals to determine a speed and a direction of motion of an object in contact with a surface of the sensor array.

9. The sensor array of claim 1, wherein the sensor circuitry is further configured to generate force data using the sensor signals and stored sensor data that represent a response of each of the sensors.

10. The sensor array of claim 9, wherein the sensor circuitry includes an analog-to-digital converter (ADC) configured to convert the sensor signals to corresponding digital signals, and wherein the stored sensor data for each sensor represent a data point for each possible value of the corresponding digital signal.

11. The sensor array of claim 9, wherein the sensor circuitry includes an analog-to-digital converter (ADC) configured to convert the sensor signals to corresponding digital signals, wherein the stored sensor data for each sensor represent a data point for fewer than all of the possible values of the corresponding digital signal, and wherein the sensor circuitry is configured to generate the force data for each sensor by interpolating between the data points stored for that sensor.

12. The sensor array of claim 1, further comprising a plurality of stiffeners, each stiffener being aligned with at least one of the sensors.

13. The sensor array of claim 1, further comprising an insulating material formed over a first conductive trace, thereby allowing a second conductive trace to cross the first conductive trace.

14. A method for fabricating a sensor array, comprising: forming a plurality of conductive sensor traces on a first surface of a first thermoplastic polyurethane (TPU) substrate;forming a plurality of conductive signal routing traces on the first TPU substrate, at least some of the signal routing traces being formed on a second surface of the first TPU substrate;placing piezoresistive fabric adjacent the first surface of the first TPU substrate and facing away from the second surface of the first TPU substrate; andthermally bonding the piezoresistive fabric to the first TPU substrate such that the piezoresistive fabric is secured in contact with the sensor traces, the piezoresistive fabric and the sensor traces forming a plurality of sensors, the sensor traces for each sensor being on a same surface of the first TPU substrate.

15. The method of claim 14, wherein the piezoresistive fabric comprises a plurality of patches, and wherein placing the piezoresistive fabric adjacent the TPU substrate comprises aligning each of the patches with a corresponding set of the sensor traces.

16. The method of claim 14, further comprising: placing a second TPU substrate adjacent the first TPU substrate and the piezoresistive fabric; andthermally bonding the second TPU substrate to the first TPU substrate and the piezoresistive fabric, thereby enclosing the plurality of sensors between the first and second TPU substrates.

17. The method of claim 16, wherein one or both of the first and second TPU substrates is characterized by an adhesive-barrier-adhesive structure, the method further comprising thermally bonding the sensor array to an additional substrate.

18. The method of claim 14, wherein forming the sensor traces and the signal routing traces on the first TPU substrate comprises printing the sensor traces and the signal routing traces on the first TPU substrate using a conductive flexible ink.

19. The method of claim 14, further comprising connecting the sensor traces to corresponding signal routing traces through the TPU substrate.

20. The method of claim 14, further comprising: selectively activating the sensors via first signal routing traces;receiving sensor signals from the sensors via second signal routing traces; andfor each of the sensors:applying a range of known forces to the sensor;generating force data for the sensor based on a corresponding one of the sensor signals, the force data representing a response of the sensor to the range of known forces; andstoring sensor data for the sensor, the sensor data representing a plurality of data points that correlate the force data with the range of known forces.

21. The method of claim 20, wherein the sensor data for each sensor represent a data point for each possible value of the corresponding force data, or wherein the sensor data for each sensor represent a data point for fewer than all of the possible values of the corresponding force data.

22. The method of claim 14, further comprising integrating a plurality of stiffeners with the sensor array, each stiffener being aligned with at least one of the sensors.

23. The method of claim 14, wherein forming the sensor traces and the signal routing traces on the first TPU substrate comprises: forming an insulating material over a first conductive trace; andforming a second conductive trace over the insulating material, thereby allowing the second conductive trace to cross the first conductive trace.

24. A sensor, comprising: a first thermoplastic polyurethane (TPU) substrate;a plurality of conductive traces on the first TPU substrate, the conductive traces including two or more sensor traces and two or more signal routing traces;piezoresistive fabric thermally bonded to the first TPU substrate such that the piezoresistive fabric is in contact with the sensor traces, the piezoresistive fabric and the sensor traces forming the sensor, the sensor traces for the sensor being on a same surface of the first TPU substrate; andsensor circuitry configured to activate the sensor via a first signal routing trace, and to receive a sensor signal from the sensor via a second signal routing trace, wherein the piezoresistive fabric, and the sensor traces form part of a voltage divider configured to generate the sensor signal, the sensor circuitry being further configured to process the sensor signal to detect one or more of mechanical force on the piezoresistive fabric, pressure on the piezoresistive fabric, distortion of the piezoresistive fabric, or deformation of the piezoresistive fabric.

25. The sensor of claim 24, further comprising a second TPU substrate thermally bonded to the first TPU substrate and the piezoresistive fabric, thereby enclosing the sensor between the first and second TPU substrates.

26. The sensor of claim 25, wherein one or both of the first and second TPU substrates is characterized by an adhesive-barrier-adhesive structure such that the sensor is configured to be thermally bonded to an additional substrate.

27. The sensor of claim 24, wherein the conductive traces comprise a conductive flexible ink printed on the first TPU substrate.

28. The sensor of claim 24, wherein the sensor circuitry is further configured to generate force data using the sensor signals and stored sensor data that represent a response of the sensor.

29. The sensor of claim 28, wherein the sensor circuitry includes an analog-to-digital converter (ADC) configured to convert the sensor signal to a digital signal, and wherein the stored sensor data for the sensor represent a data point for each possible value of the digital signal.

30. The sensor of claim 28, wherein the sensor circuitry includes an analog-to-digital converter (ADC) configured to convert the sensor signal to a digital signal, wherein the stored sensor data for each sensor represent a data point for fewer than all of the possible values of the digital signal, and wherein the sensor circuitry is configured to generate the force data for the sensor by interpolating between the data points.

31. The sensor of claim 24, further comprising a stiffener aligned with the sensor.

32. The sensor of claim 24, wherein at least one of the signal routing traces is formed on a surface of the first TPU substrate facing away from the piezoresistive fabric.

33. A sensor array, comprising: a first thermoplastic polyurethane (TPU) substrate;a plurality of conductive traces on the first TPU substrate, the conductive traces including a plurality of sensor traces and a plurality of signal routing traces; andpiezoresistive fabric thermally bonded to the first TPU substrate such that the piezoresistive fabric is in contact with the sensor traces, the piezoresistive fabric and the sensor traces forming a plurality of sensors, the sensor traces for each sensor being on a same surface of the first TPU substrate;wherein the sensor traces are on a first surface of the first TPU substrate facing toward the piezoresistive fabric, and wherein at least some of the signal routing traces are on a second surface of the first TPU substrate facing away from the piezoresistive fabric.

34. The sensor array of claim 33, wherein the piezoresistive fabric comprises a plurality of patches, each of the patches being associated with one of the sensors.

35. The sensor array of claim 33, further comprising a second TPU substrate thermally bonded to the first TPU substrate and the piezoresistive fabric, thereby enclosing the plurality of sensors between the first and second TPU substrates.

36. The sensor array of claim 35, wherein one or both of the first and second TPU substrates is characterized by an adhesive-barrier-adhesive structure such that the sensor array is configured to be thermally bonded to an additional substrate.

37. The sensor array of claim 33, wherein the conductive traces comprise a conductive flexible ink printed on the first TPU substrate.

38. The sensor array of claim 33, further comprising sensor circuitry configured to selectively activate the sensors via first signal routing traces, and to receive sensor signals from the sensors via second signal routing traces.

39. The sensor array of claim 38, wherein the sensor circuitry is further configured to process the sensor signals to detect one or more of mechanical force on the piezoresistive fabric, pressure on the piezoresistive fabric, distortion of the piezoresistive fabric, or deformation of the piezoresistive fabric.

40. The sensor array of claim 38, wherein the sensor circuitry is further configured to process the sensor signals to determine a speed and a direction of motion of an object in contact with a surface of the sensor array.

41. The sensor array of claim 38, wherein the sensor circuitry is further configured to generate force data using the sensor signals and stored sensor data that represent a response of each of the sensors.

42. The sensor array of claim 41, wherein the sensor circuitry includes an analog-to-digital converter (ADC) configured to convert the sensor signals to corresponding digital signals, and wherein the stored sensor data for each sensor represent a data point for each possible value of the corresponding digital signal.

43. The sensor array of claim 41, wherein the sensor circuitry includes an analog-to-digital converter (ADC) configured to convert the sensor signals to corresponding digital signals, wherein the stored sensor data for each sensor represent a data point for fewer than all of the possible values of the corresponding digital signal, and wherein the sensor circuitry is configured to generate the force data for each sensor by interpolating between the data points stored for that sensor.

44. The sensor array of claim 38, wherein a first sensor of the plurality of sensors includes a portion of the piezoresistive fabric, a first sensor trace of the plurality of sensor traces, and a second sensor trace of the plurality of sensor traces, the portion of the piezoresistive fabric, the first sensor trace, and the second sensor trace forming part of a voltage divider configured to generate a corresponding one of the sensor signals.

45. The sensor array of claim 33, further comprising a plurality of stiffeners, each stiffener being aligned with at least one of the sensors.

46. The sensor array of claim 33, further comprising an insulating material formed over a first conductive trace, thereby allowing a second conductive trace to cross the first conductive trace.