Scalable distributed tactile sensors without integrated circuits using resonance multiplexed piezoelectric sensors

Abstract

A sensor system is disclosed that achieves scalable sensing through mechanical multiplexing. The system comprises a plurality of sensor members, each characterized by a distinct mechanical signature based on its physical properties. The sensor members are coupled to a shared electrical interface, providing a composite signal to a processor. The processor is configured to demultiplex the composite signal by identifying the known mechanical signatures of the sensors, thereby determining which sensors have been actuated without requiring integrated circuits at the sensing locations.

Description

Attorney Docket No. 0184.0314-PCTClient Ref. No. C18042_P 18042-02Scalable Distributed Tactile Sensors without Integrated Circuits using Resonance Multiplexed Piezoelectric SensorsCross Reference to Related Applications

[0001] This application claims priority to U.S. Patent Provisional Application No. 63 / 682,440 filed on August 13, 2024, the contents of which are hereby incorporated by reference in its entirety.Field

[0002] The present disclosure relates to tactile sensors, and more particularly to scalable distributed tactile sensors.Background

[0003] State-of-the-art scalable tactile sensor arrays embed electronic processing inside each tactile sensor to achieve low latency and low wiring complexity through local multiplexing. However, the integrated circuits at each sensing pixel pose many problems including limiting density, limiting robustness in extreme environments (outer space / underwater), and incurring large costs and fabrication complexity.Summary

[0004] According to examples of the present disclosure, a sensor system is disclosed that comprises an array of sensors, where each sensor in the array of sensors has a unique mechanical signature. The sensor system provides for a multiplexing of signals from each sensor in the array of sensors for analysis and processing. In operation, when a sensor in the array of sensors responds to a stimulus, the sensor response is characterized by a unique signal that is based on, or programmed by, the particular mechanical structure of the sensor. As a result of each sensor’s unique response signal or characteristic, all signals produced by the sensor system can be combined together in parallel or multiplexed to allow for all the sensors in the sensor system to transmit their data simultaneously. Because of the uniqueness of each sensor’s output signal, the output signal provides a unique identity of the sensor that produced the output signal. These combined signals can be appropriately decoded or demultiplexed because each sensor in the sensor system is unique based on the particular mechanical arrangement of each sensor.

[0005] According to examples of the present disclosure, a sensor system is disclosed. The sensor system comprises a plurality of mechanically responsive sensor members, eachAtorney Docket No. 0184.0314-PCTClient Ref. No. C18042_P 18042-02 comprising a movable portion and a fixed portion, each sensor member configured to produce a distinct response signal when actuated by an external stimulus, wherein each sensor member is characterized by a distinct mechanical signature based on one or more structural properties of the sensor member; a shared electrical interface coupling all of the sensor members to a processor via a common signal pathway; and the processor configured to receive a composite signal from the sensor members and to identify one or more actuated sensor members by demultiplexing the composite signal using the known mechanical signatures of the sensor members. The mechanical signature of each sensor member comprises a characteristic resonant frequency. The mechanical signature comprises a time-domain impulse response unique to the sensor member. The shared electrical interface comprises a pair of wires connecting the plurality of sensor members in parallel to the processor. The processor demultiplexes the composite signal using frequency domain, time-domain, or transfer function analysis to detect the presence of mechanical signatures corresponding to one or more sensor members. The sensor members are cantilevered structures mounted to a housing. Each sensor member comprises a piezoelectric element configured to generate a voltage in response to deformation caused by external mechanical input. The processor is located remotely from the sensor members.

[0006] According to examples of the present disclosure, a sensor system is disclosed that comprises a first mechanical sensor member comprising a first mechanical sensor member fixed end and a first mechanical sensor member movable end, wherein the first sensor member has a first characteristic mechanical signature, such as a first characteristic resonance frequency when actuated, that is based on one or more properties of the first mechanical sensor member; and a processor in electrical communication with the first mechanical sensor member to obtain a response signal from the first mechanical sensor member when actuated by an outside force, wherein the response signal identifies the first mechanical sensor member based on the one or more properties of the first mechanical sensor member.

[0007] Various additional features can be included with the disclosed sensor system including one or more of the following features. The sensor system can further comprise a housing that comprises an insulation material. The first mechanical sensor is a cantilevered such that the first mechanical sensor member fixed end is mounted to a first position on an interior surface of the housing. The first mechanical sensor member comprises a first insulation layer, a first metal layer, a first piezoelectric layer, a second metal layer, and a second insulation layer. The first piezoelectric layer is arranged between the first metal layer and the second metal layer. The first piezoelectric layer, the first metal layer, and the second metal layer areAtorney Docket No. 0184.0314-PCTClient Ref. No. C18042_P 18042-02 arranged between the first insulation layer and the second insulation layer. The first metal layer and the second metal layer comprise copper. The first insulation layer and the second insulation layer comprise a same material of the housing. The insulation material of the housing comprises a polydimethylsiloxane (PDMS) material. The sensor system can further comprise a second mechanical sensor member comprising a second mechanical sensor member fixed end and a second mechanical sensor member movable end, wherein the second mechanical sensor member fixed end is mounted to a second position on the interior surface of the housing, wherein the second mechanical sensor member has a second characteristic resonance frequency when actuated that is based on one or more properties of the second mechanical sensor member. The sensor system can further comprise additional mechanical sensor members, wherein each additional mechanical sensor members comprise a mechanical sensor member fixed end and a mechanical sensor member movable end, wherein the mechanical sensor member fixed end is mounted to a position on the interior surface of the housing, wherein each of the additional mechanical sensor members has a characteristic resonance frequency when actuated that is based on one or more properties of each of the additional mechanical sensor members. The processor is connected to the first mechanical sensor member, the second mechanical sensor member, and the additional mechanical sensor members by a pair of wires. The processor is configured to multiplex, demultiplex, or both multiplex and demultiplex signals from the first mechanical sensor member, the second mechanical sensor member, and the additional mechanical sensor members received over a pair of wires using a multiplexing algorithm, a demultiplexing algorithm, or both a multiplexing and a demultiplexing algorithm. The processor is arranged remote from the housing. The first mechanical sensor member comprises a first piezoelectric element near the first mechanical sensor member fixed end, the second mechanical end comprises a second piezoelectric element near the second mechanical sensor member fixed end, and the additional mechanical sensor members comprises additional piezoelectric element near each of the additional mechanical sensor members fixed end. The processor is connected to the first piezoelectric element, the second piezoelectric element, and each additional piezoelectric element by a pair of wires. According to examples of the present disclosure, the sensor members are mounted to an interior surface of the housing and the housing comprises a polydimethylsiloxane (PDMS) material. The cantilevered structures each comprise a first insulation layer, a first metal layer, the piezoelectric element, a second metal layer, and a second insulation layer. The first and second metal layers comprise copper. The at least one sensor member comprises two or more cantilevered structures to produce a dual-tone or multi-tone mechanical signature.Atorney Docket No. 0184.0314-PCTClient Ref. No. C18042_P 18042-02

[0008] According to examples of the present disclosure, a sensor system is disclosed that comprises a housing comprises an insulation material; a first cantilevered sensor member comprising a first cantilevered sensor member fixed end and a first cantilevered sensor member movable end, wherein the first cantilevered sensor member fixed end is mounted to a first position on an interior surface of the housing, wherein the first cantilevered sensor member has a first characteristic mechanical signature, such as a first characteristic resonance frequency when actuated, that is based on one or more properties of the first cantilevered sensor member; and a processor in electrical communication with the first cantilevered sensor member to obtain a response signal from the first cantilever sensor member when actuated by an outside force, wherein the response signal identifies the first mechanical sensor member based on the one or more properties of the first mechanical sensor member.

[0009] Various additional features can be included with the disclosed sensor system including one or more of the following features. The first cantilevered sensor member comprises a first insulation layer, a first metal layer, a first piezoelectric layer, a second metal layer, and a second insulation layer. The first piezoelectric layer is arranged between the first metal layer and the second metal layer. The first piezoelectric layer, the first metal layer, and the second metal layer are arranged between the first insulation layer and the second insulation layer. The first metal layer and the second metal layer comprise copper. The first insulation layer and the second insulation layer comprise a same material of the housing. The insulation material of the housing comprises a poly dimethylsiloxane (PDMS) material. The sensor system can further comprise a second cantilevered sensor member comprising a second cantilevered sensor member fixed end and a second cantilevered sensor member movable end, wherein the second cantilevered sensor member fixed end is mounted to a second position on the interior surface of the housing, wherein the second cantilevered sensor member has a second characteristic resonance frequency when actuated that is based on one or more properties of the second cantilevered sensor member. The sensor system can further comprise a third cantilevered sensor member comprising a third cantilevered sensor member fixed end and a third cantilevered sensor member movable end, wherein the third cantilevered sensor member fixed end is mounted to a third position on the interior surface of the housing, wherein the third cantilevered sensor member has a third characteristic resonance frequency when actuated that is based on one or more properties of the third cantilevered sensor member. The processor is connected to the first cantilevered sensor member, the second cantilevered sensor member, and the third cantilevered sensor member by a pair of wires. The processor is configured to multiplex, demultiplex, or both multiplex and demultiplex signals from the first cantileveredAtorney Docket No. 0184.0314-PCT Client Ref. No. C18042_P 18042-02 sensor member, the second cantilevered sensor member, and the third cantilevered sensor member received over a pair of wires using a multiplexing algorithm, a demultiplexing algorithm, or both a multiplexing and a demultiplexing algorithm. The processor is arranged remote from the housing. The first cantilevered sensor member comprises a first piezoelectric element near the first cantilevered sensor member fixed end, the second cantilevered end comprises a second piezoelectric element near the second cantilevered sensor member fixed end, and the third cantilevered sensor member comprises a third piezoelectric element near the third cantilevered sensor member fixed end. The processor is connected to the first piezoelectric element, the second piezoelectric element, and the third piezoelectric element by a pair of wires.Brief Description of the Figures

[0010] FIG. 1 shows a sensor array system according to examples of the present disclosure applied over an exploratory rover. The inset box shows zoomed-in view of the present sensor, with each cell containing a piezoelectric cantilever with a different resonance frequency (packaging not shown for clarity).

[0011] FIG. 2A, FIG. 2B, FIG. 2C, and FIG. 2D shows the operation of a sensor according to examples of the present disclosure, where FIG. 2A shows a side view of a sensor cell of the present sensor where a cantilevered beam has a piezoelectric disc integrated at its base that converts the vibrations of the beam into a voltage across its two wires, FIG. 2B shows a drawing of the vibration of a cantilever beam from an applied force fresonance is determined by the dimensions of the beam and the material properties, FIG. 2C shows a plot of applied force versus time depicting the voltage response of the piezoelectric cantilever to force where the frequency of the response ( resonance) is determined by the resonance frequency of the cantilever in the cell, and FIG. 2D shows a response plot of the sensor of FIG. 2A.

[0012] FIG. 3 shows a state-of-the-art scalable tactile sensor (TS) with integrated circuits (ICs) compared to a cantilevered sensor without ICs according to examples of the present disclosure.

[0013] FIG. 4A shows a top perspective view of an individual sensor cell according to examples of the present disclosure.

[0014] FIG. 4B shows a botom perspective view of FIG. 4 A.

[0015] FIG. 4C shows a response plot of the individual sensor cell of FIG. 4 A.

[0016] FIG. 4D shows plots of DFT of three sensors in real-time according to examples of the present disclosure.Atorney Docket No. 0184.0314-PCT Client Ref. No. C18042_P 18042-02

[0017] FIG. 5 shows a block diagram of a number of cells arranged in parallel with a processor according to examples of the present disclosure.

[0018] FIG. 6A shows a picture of a miniaturized cell according to examples of the present disclosure.

[0019] FIG. 6B shows a close-up picture of two cantilevered beams used in the example ofFIG. 6A.

[0020] FIG. 6C shows a response plot of the miniaturized cell of FIG. 6 A.

[0021] FIG. 7A shows a block diagram of a radiation testing system according to examples of the present disclosure.

[0022] FIG. 7B shows a picture of a testing system according to examples of the present disclosure.

[0023] FIG. 8 shows a plot of voltage output versus time depicting the varied voltage value actuation of the same cantilever according to examples of the present disclosure.

[0024] FIG. 9A shows plots of ADC values with offsets versus time depicting the behavior of single beam at different weights according to examples of the present disclosure.

[0025] FIG. 9B shows plots of magnitude with offset versus frequency depicting FFT versus weights of the plots shown in FIG. 9A.

[0026] FIG. 10 shows a plot of resonance frequency versus trial number depicting the effect of applied weight on resonance frequency according to examples of the present disclosure.

[0027] FIG. 11 A shows a piezoelectric circuit model according to examples of the present disclosure.

[0028] FIG. 1 IB shows a sensor circuit according to examples of the present disclosure.

[0029] FIG. 11C shows a block representation of a plurality of sensor cells arranged in parallel with a processor according to examples of the present disclosure.

[0030] FIG. 12A shows a picture of three different proof mass sizes on each cantilever beam according to examples of the present disclosure.

[0031] FIG. 12B shows a response plot for a first proof mass of FIG. 12 A.

[0032] FIG. 12C shows a response plot for a second proof mass of FIG. 12 A.

[0033] FIG. 12D shows a response plot for a third proof mass of FIG. 12 A.

[0034] FIG. 13 A shows a picture of an experimental setup according to examples of the present disclosure.

[0035] FIG. 13B shows a response plot for a first cantilever beam after tapping using the setup of FIG. 13 A.Atorney Docket No. 0184.0314-PCTClient Ref. No. C18042_P 18042-02

[0036] FIG. 13C shows a response plot for a second cantilever beam after tapping using the setup of FIG. 13 A.

[0037] FIG. 13D shows a response plot for a third cantilever beam after tapping using the setup of FIG. 13 A.

[0038] FIG. 13E shows screenshots of real-time Goertzel output after tapping the different sensors of FIG. 13 A where the y-axis represents DFT amplitude and the x-axis represents time.

[0039] FIG. 14 shows a picture of the internals of a sensor cell according to examples of the present disclosure.

[0040] FIG. 15 shows a picture of another view of the sensor cell of FIG. 14 showing the sensor cell silicone cap.

[0041] FIG. 16 shows screenshot of a computer model of the sensor cell according to examples of the present disclosure.Detailed Description

[0042] According to the below examples, the phrase “mechanical signature” can include any physically encoded feature of the sensor that affects its dynamic output in a unique way. For example, the mechanical signature can include a resonant frequency. Also, the phrase “mechanical multiplexing” can include a strategy, a technique, a method, a process, a device, a system, etc., of identifying sensor responses via a mechanical signature that enables shared wiring and scalable sensing.

[0043] According to examples of the present disclosure, a system, a device, and a method of developing a scalable tactile sensor array without integrated circuits using resonance multiplexed structures is disclosed. The disclosed system, device, and method can use one or more mechanical structures for frequency multiplexing. The disclosed scalable sensor array can be self-powered, electronics-free tactile sensors that are immune to various hazards, such as the hazards of cosmic radiation (which would destroy conventional tactile sensor arrays with integrated circuits). For context, a ‘scalable’ tactile sensor array is a low latency sensor array that requires only a few interfacing wires regardless of the number of sensing units. In some examples, the disclosed scalable sensor array can resolve dynamic forces over a wide range, can operate underwater and in high radiation environments, can provide simultaneous proprioceptive insights in addition to force recordings, uses one wire for simultaneous asynchronous sensor communication, and has sub -millisecond latency. The disclosed sensor array can be responsive to diverse and relevant tactile stimuli and its proprioceptive capabilities and robustness can be usable in a variety of extreme environments. In some examples, theAtorney Docket No. 0184.0314-PCT Client Ref. No. C18042_P 18042-02 sensor array can be arranged to enable high-density tactile sensorization of robotic systems in outer space and other extreme environments. The disclosed examples solve the problem of creating a scalable tactile array without electronics, which makes it extremely robust in outer space conditions or wherever integrated circuits become compromised. This allows the present sensor array to operate as tactile sensing systems in outer space and allows for the. It is the creation of a scalable tactile array without electronics inside the taxel.

[0044] FIG. 1 shows a sensor array system 100 according to examples of the present disclosure applied over an exploratory rover. The inset box shows zoomed-in view of the present sensor array, with each cell containing a piezoelectric cantilever with a different resonance frequency (silicon package not shown for clarity). For example, the sensor array can be arranged in one or more positions on the rover for contact detection, delicate grasping, and / or terrain detection. The rover is just one non-limiting example where the present sensor arrays can be used.

[0045] On earth, whole-body tactile sensing has been recognized as a crucial requirement for the next generation of robots by numerous studies, especially for enabling precise and safe robotic interactions in unstructured environments. But in outer space, the crucial need for large- area force sensing is even greater as mistakes cannot be tolerated. As examples, several cases of this need are shown in FIG. 1. In space it is imperative to detect unexpected contacts with dangerous objects, such as to protect robotic rovers and humans in spacesuits (which can be difficult if relying on cameras or distance sensors during adverse conditions such as sandstorms), or in future exploration of tight spaces such as caverns. Exploratory robots require delicate grasping to manipulate and collect unknown, potentially fragile samples in the field. Space vehicles need to detect the texture and type of terrain that they are traversing, to avoid dangerous terrain like sand. Remarkably in all these examples, tactile sensing is vital for success (FIG. 1)- and hence there is a significant need for tactile sensing systems in space.

[0046] However, despite the demonstrated requirement for tactile sensing in space, the previously developed scalable tactile sensing systems on Earth cannot be applied to outer space. This is due to the omnipresent use of integrated circuits (FIG. 3) which cannot survive cosmic radiation without excessive shielding. Without shielding, these circuits get damaged by radiation due to energetic protons, electrons, heavy ions, and cosmic ray particles that damage transistors and lead to single event effects (SEE) and an accumulating total ionizing dose (TID). Both SEE and TID cause transistors in integrated circuits to fail (and have even caused the failure of entire missions).Atorney Docket No. 0184.0314-PCTClient Ref. No. C18042_P 18042-02

[0047] Furthermore, due to the nature of using tactile sensor arrays on the outside of a robot / subject / tool, shielding tactile sensors would render the sensors useless as it would desensitize the sensors to contact forces. Hence, there is a need to develop a new tactile sensing system that does not contain integrated circuits and does not require shielding.

[0048] The disclosed system solves this problem through a novel approach herein termed "mechanical multiplexing." In this system, each sensor is designed with a unique "mechanical signature," which can include any physically encoded feature that affects its dynamic output in a unique way, such as a characteristic resonant frequency. This strategy of identifying sensor responses via their inherent mechanical signatures enables shared wiring and truly scalable sensing without local electronics.

[0049] Two additional desired properties for tactile sensors in space are self-powered sensors, and sensor arrays with minimal wiring. In some examples, a tactile sensor can be used for space applications that satisfies all three requirements: a tactile sensor that is self-powered, has minimal wiring, and has no integrated circuits.

[0050] FIG. 2A, FIG. 2B, FIG. 2C, and FIG. 2D shows the operation of a sensor according to examples of the present disclosure, where FIG. 2A shows a side view 200 of a sensor cell of the present sensor where a cantilevered beam 202 has a piezoelectric disc integrated at its base that converts the vibrations of the beam into a voltage across its two wires, FIG. 2B shows a drawing of the vibration of a cantilever beam from an applied force resonance is determined by the dimensions of the beam and the material properties, FIG. 2C shows a plot of applied force versus time depicting the voltage response of the piezoelectric cantilever to force where the frequency of the response ( resonance) is determined by the resonance frequency of the cantilever in the cell, and FIG. 2D shows a response plot of the sensor of FIG. 2 A. As shown in FIG. 2 A, the sensor cell comprises an insulation package 204, such as a polydimethylsiloxane (PDMS) insulation package, that houses the cantilevered beam 202. The cantilevered beam 202 can comprise a first insulation layer 206, a first metal layer 208, such as a copper layer, a piezoelectric material layer 210, a second metal layer 212, such as a copper layer, and a second insulation layer 214. The first insulation layer 206 and the second insulation layer 214 can be formed of the same material used in the insulation package 204. The sensor cell is responsive to a force as indicated by arrow 216. The cantilevered beam 202 is connected at one end of the cantilevered beam 202 to one interior surface of the insulation package 204. As shown in FIG. 2B, the cantilevered beam 202 is shown oscillating at its resonance frequency, denoted asAtorney Docket No. 0184.0314-PCTClient Ref. No. C18042_P 18042-02

[0051] FIG. 3 shows a state-of-the-art scalable tactile sensor (TS) with integrated circuits (ICs) 300 compared to a cantilevered sensor without ICs 310 according to examples of the present disclosure.

[0052] To create a self-powered, single-wire, electronics-free, tactile sensor, frequency- multiplexed piezoelectric cantilever structures are used. Cantilever structures vibrate when a force is applied to them (FIG. 2B). The frequency of vibration (the resonance frequency, / ^) is dependent on the beam’s material properties and dimensions (p=mass density, L=length, I=area moment of inertia, E=elasticity modulus), and the amplitude of vibration is dependent on the amplitude of the applied force. By integrating a piezoelectric element on the cantilever, the movement of the beam is translated into proportional voltage patterns that a microcontroller can measure (FIG. 2C and FIG. 4C). Additionally, unlike integrated circuits which are normally fabricated in CMOS processes, piezoelectric materials such as PZT are highly resistant towards radiation doses. PZT is known to withstand radiation doses greater than 150 MRad without a change of function, while CMOS circuits have a total dose limit of only 3 kRad. This makes PZT categorized as a “Rad Hard” material by NASA because the total dose threshold for “Rad Hard” is >1 MRad. From these numbers we can estimate that a PZT-based tactile sensor is 50,000x more tolerant of radiation than a tactile sensor with integrated circuits.

[0053] FIG. 4A shows a top perspective view 400 of an individual sensor cell according to examples of the present disclosure. As shown in FIG. 4A, a cantilever beam 402 with piezoelectric element 404 atached is shown. FIG. 4B shows a bottom perspective view 410 of FIG. 4A. As shown in FIG. 4B, an enclosed sensor cell with 3D printed package and with two connection wires 406 is shown. FIG. 4C shows a response plot of the individual sensor cell of FIG. 4A. As shown in FIG. 4C, the voltage response of the sensor cell to a tap on the top of the sensor cell is shown where the frequency of the voltage response (132 Hz) is the resonance frequency of the cantilever beam. FIG. 4D shows plots of DFT of three sensors in real-time according to examples of the present disclosure. As shown in FIG. 4D, the real-time Fourier analysis of three sensor cells tuned to different frequencies is shown, where sensor one and sensor two are tapped at the same time and sensor three is not tapped, demonstrating how multiple sensors can communicate simultaneously over a single common wire without interference.

[0054] FIG. 5 shows a wiring block diagram 500 of a number of sensor cells arranged in parallel with a processor according to examples of the present disclosure. The wiring block diagram 500 comprises a first sensor cell 502, a second sensor cell 504, and a third sensor cell 506 arranged and wired in parallel with a processor 508 using wires 510. Although FIG. 5Atorney Docket No. 0184.0314-PCT Client Ref. No. C18042_P 18042-02 shows three sensor cells, this is just one example and other applications may use more or less than three sensor cells, including just one sensor cell.

[0055] To multiplex the sensors, each beam is designed with a different resonance frequency, and thus all sensors can be connected to a single common wire for voltage readout, and one wire for ground (FIG. 5). By making each sensor communicate at a different frequency, the signal is frequency-multiplexed, and all sensors can communicate simultaneously without interference (FIG. 4D). Furthermore, the sensors do not require powering as the piezoelectric layer produces a voltage in response to an applied force, and no external power is needed to activate the sensors (unlike resistive or capacitive tactile sensors).

[0056] In some examples, the sensor array can include 3D printed cantilever beams and commercially available piezoelectric sensing elements (FIG. 4). For example, FIG. 4C shows the voltage output of a sensor cell in response to a tap, with excellent agreement with the simulated response in FIG. 2C. Additionally, FIG. 4D demonstrates the frequency multiplexing of the sensor array, showing how three cells tuned to different frequencies can respond simultaneously over the same common wire without interference.

[0057] FIG. 6A shows a picture of a miniaturized cell according to examples of the present disclosure. As shown in FIG. 6A, a comparison of 3D-printed prototype with PCB-based cells 602 with the miniaturized cell 604 is shown. FIG. 6B shows a close-up picture of two differently sized cantilevered beams 606, 610 with corresponding piezoelectric elements 608, 612 that have different resonance frequencies used in the example of FIG. 6A. The cell 604 is connected with two wires 614. As shown in FIG. 6B, the picture shows the PCB-based cells with a two-beam design at 15mm scale. FIG. 6C shows a response plot of the miniaturized cell of FIG. 6 A.

[0058] To improve the scalability of the sensor array, the sensor array can use two cantilever beams in each sensor cell (FIG. 6B). This gives each cell a unique dual-tone frequency response which requires fewer frequencies (and less beam dimension variations) for large arrays. Additionally, FIG. 6B shows how the sensor array can be manufactured at smaller scales using PCB processes. By dual-tone encoding with two beams in each sensor, the total number of beam dimensions for a large array shrinks substantially. Given N beam dimensions, for each cell to have a unique two beam combination, the total number of cells becomes N choose 2, which grows factorially with N. This makes it significantly simpler to create large arrays with many sensors.Atorney Docket No. 0184.0314-PCTClient Ref. No. C18042_P 18042-02

[0060] The sensor arrays can be arranged as frequency-multiplexed piezoelectric sensor arrays. The frequency-multiplexed sensor arrays can be used with one or more real-time embedded de-multiplexing algorithms that can resolve sensor readings with 1kHz temporal resolution. The sensor array can be arranged to as tactile sensor arrays for the prosthetic hand. The sensors can be miniaturized using microfabrication techniques. The sensors can provide enhanced shape and object recognition capabilities and texture recognition capabilities. The radiation tolerance of the sensors can be tested using high energy x-rays (from CT scanning machines) and high energy proton beams (from a Proton Synchotron). Proton radiation testing is more closely matched to space conditions because energetic protons are one of the more hazardous forms of cosmic radiation.

[0061] The piezoelectric devices can be fabricated using microfabrication processes, such as the MEMSCAP PiezoMUMPS process to microfabricate sensor cells. MUMPs (acronym for Multi-User-MEMS Process) is a service that allows universities to microfabricate piezoelectric devices without large costs and upfront fees by sharing resources among many users and designs.

[0062] The sensors can be used in space exploration tasks, such as contact detection and delicate object grasping. By covering the body of a rover with the sensors, this can help it avoid harmful collisions with hazardous objects and improve navigation.

[0063] Sensor cells can be applied with a high-density at the contact surfaces of robotic grippers can statistically improve manipulation and grasping of objects collected on the field, showing that rovers can recover delicate samples. Terrain detection. This task will show that the sensor cells applied to the tires of a rover can detect the textures of different terrains, specifically to differentiate between hazardous terrain and safe terrain.

[0064] FIG. 7A shows a block diagram of a radiation testing system 700 according to examples of the present disclosure. FIG. 7B shows a picture of a radiation testing system 720 according to examples of the present disclosure. As shown in FIG. 7A, a solenoid actuates a sensor cell 702 while the sensor cell 702, such as any of the presently disclosed sensor cell discussed herein, is exposed to radiation produced by a linear accelerator 706.

[0065] FIG. 8 shows a plot of voltage output versus time 800 depicting the varied voltage value actuation of the same cantilever according to examples of the present disclosure.

[0066] FIG. 9A shows plots of ADC values with offsets versus time 900 depicting the behavior of single beam at different weights according to examples of the present disclosure. FIG. 9B shows plots of magnitude with offset versus frequency 910 depicting FFT versus weights of the plots shown in FIG. 9A.Atorney Docket No. 0184.0314-PCTClient Ref. No. C18042_P 18042-02

[0067] FIG. 10 shows a plot of resonance frequency versus trial number 1000 depicting the effect of applied weight on resonance frequency according to examples of the present disclosure.

[0068] FIG. 11A shows a piezoelectric circuit model 1100 according to examples of the present disclosure. FIG. 1 IB shows a sensor circuit 1110 according to examples of the present disclosure. FIG. 11C shows a block representation 1120 of a plurality of sensor cells arranged in parallel with a processor according to examples of the present disclosure. The block representation 1120 is similar to the wiring block diagram 500 and comprises a first sensor cell 1122, a second sensor cell 1124, and a third sensor cell 1126 arranged and wired in parallel with a processor 1128 using wires 1130. Although FIG. 11C shows three sensor cells, this is just one example and other applications may use more or less than three sensor cells, including just one sensor cell.

[0069] FIG. 12A shows a picture of three different proof mass sizes on each cantilever beam 1200 according to examples of the present disclosure. Each proof mass comprises a resin material 1202, a polylactic acid or polylactide (PL A) material 1204, and a thermoplastic polyurethane (TPU) material 1206. FIG. 12B shows a response plot 1210 for a first proof mass of FIG. 12 A. FIG. 12C shows a response plot 1220 for a second proof mass of FIG. 12 A. FIG. 12D shows a response plot 1230 for a third proof mass of FIG. 12 A.

[0070] FIG. 13A shows a picture of an experimental setup 1300 of three separate sensors with different mechanical sensor member lengths according to examples of the present disclosure. As shown in FIG. 13A, a first sensor with a cantilevered beam 1302 with a first resonance frequency fi, a second sensor with a cantilevered beam 1304 with a second resonance frequency / j, and a third sensor with a cantilevered beam 1306 with a third resonance frequency fs. As shown, the third cantilevered beam 1306 is longer than the second cantilevered beam 1304 and the second cantilevered beam 1304 is longer than the first cantilevered beam 1302. FIG. 13B shows a response plot 1310 for the first cantilever beam 1302 after tapping using the setup of FIG. 13A showing the first resonance frequency fi of 143 Hz. FIG. 13C shows a response plot 1312 for the second cantilever beam 1304 after tapping using the setup of FIG. 13A showing the first resonance frequency f2 of 75.8 Hz. FIG. 13D shows a response plot 1314 for the third cantilever beam 1306 after tapping using the setup of FIG. 13A showing the first resonance frequency fs of 39.7 Hz. FIG. 13E shows screenshots 1316 of real-time Goertzel output after tapping the different sensors of FIG. 13 A where the y-axis represents DFT amplitude and the x-axis represents time.Atorney Docket No. 0184.0314-PCTClient Ref. No. C18042_P 18042-02

[0071] FIG. 14 shows a picture of the internals of a sensor cell 1400 according to examples of the present disclosure. As shown in FIG. 14, a bottom enclosure portion 1402 is shown that houses a cantilevered beam 1404. A piezoelectric element 1408 is arranged near the base (closest portion to an edge of the enclosure) of the cantilevered beam 1404. A top enclosure portion 1410 is shown to the right of the bottom enclosure portion 1402. The top enclosure portion 1410 and the bottom enclosure portion 1402 can be sealed together using various sealing elements, such screws 1412 and nuts 1414. FIG. 15 shows a picture of another view of the sensor cell 1500 of FIG. 14 showing the sensor cell silicone cap.

[0072] FIG. 16 shows screenshot of a computer model of the sensor cell according to examples of the present disclosure.

[0073] In one or more embodiments, the functions described can be implemented in hardware, software, firmware, or any combination thereof. For a software implementation, the techniques described herein can be implemented with modules (e.g., procedures, functions, subprograms, programs, routines, subroutines, modules, software packages, classes, and so on) that perform the functions described herein. A module can be coupled to another module or a hardware circuit by passing and / or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, or the like can be passed, forwarded, or transmitted using any suitable means including memory sharing, message passing, token passing, network transmission, and the like. The software codes can be stored in memory units and executed by processors. The memory unit can be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art.

[0074] Further, the steps in the processing methods described herein may be implemented by running one or more functional modules in information processing apparatus such as general purpose processors or application specific chips, such as ASICs, FPGAs, PLDs, or other appropriate devices. These modules, combinations of these modules, and / or their combination with general hardware are all included within the scope of protection of the invention.

[0075] The examples set forth herein represent the necessary information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.Atorney Docket No. 0184.0314-PCTClient Ref. No. C18042_P 18042-02

[0076] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0077] It will be understood that when an element such as a layer, region, or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. Likewise, it will be understood that when an element such as a layer, region, or substrate is referred to as being “over” or extending “over” another element, it can be directly over or extend directly over the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly over” or extending “directly over” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present.

[0078] Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures.

[0079] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and / or “including” when used herein specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which thisAtorney Docket No. 0184.0314-PCT Client Ref. No. C18042_P 18042-02 disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Claims

Atorney Docket No. 0184.0314-PCT Client Ref. No. C18042_P 18042-02What is Claimed is:

1. A sensor system comprising: a plurality of mechanically responsive sensor members, each comprising a movable portion and a fixed portion, each sensor member configured to produce a distinct response signal when actuated by an external stimulus, wherein each sensor member is characterized by a distinct mechanical signature based on one or more structural properties of the sensor member; a shared electrical interface coupling all of the sensor members to a processor via a common signal pathway; and the processor configured to receive a composite signal from the sensor members and to identify one or more actuated sensor members by demultiplexing the composite signal using the known mechanical signatures of the sensor members.

2. The sensor system of claim 1, wherein the mechanical signature of each sensor member comprises a characteristic resonant frequency.

3. The sensor system of claim 1, wherein the mechanical signature comprises a timedomain impulse response unique to the sensor member.

4. The sensor system of claim 1, wherein the shared electrical interface comprises a pair of wires connecting the plurality of sensor members in parallel to the processor.

5. The sensor system of claim 1 , wherein the processor demultiplexes the composite signal using frequency domain, time-domain, or transfer function analysis to detect the presence of mechanical signatures corresponding to one or more sensor members.

6. The sensor system of claim 1, wherein the sensor members are cantilevered structures mounted to a housing.

7. The sensor system of claim 1, wherein each sensor member comprises a piezoelectric element configured to generate a voltage in response to deformation caused by external mechanical input.Atorney Docket No. 0184.0314-PCT Client Ref. No. C18042_P 18042-028. The sensor system of claim 1, wherein the processor is located remotely from the sensor members.

9. A sensor system comprising: a housing comprises an insulation material; a first cantilevered sensor member comprising a first cantilevered sensor member fixed end and a first cantilevered sensor member movable end, wherein the first cantilevered sensor member fixed end is mounted to a first position on an interior surface of the housing, wherein the first cantilevered sensor member has a first characteristic mechanical signature that is based on one or more properties of the first cantilevered sensor member; and a processor in electrical communication with the first cantilevered sensor member to obtain a response signal from the first cantilever sensor member when actuated by an outside force, wherein the response signal identifies the first mechanical sensor member based on the one or more properties of the first mechanical sensor member.

10. The sensor system of claim 9, wherein the first cantilevered sensor member comprises a first insulation layer, a first metal layer, a first piezoelectric layer, a second metal layer, and a second insulation layer.

11. The sensor system of claim 10, wherein the first piezoelectric layer is arranged between the first metal layer and the second metal layer.

12. The sensor system of claim 11, wherein the first piezoelectric layer, the first metal layer, and the second metal layer are arranged between the first insulation layer and the second insulation layer.

13. The sensor system of claim 10, wherein the first metal layer and the second metal layer comprise copper.

14. The sensor system of claim 10, wherein the first insulation layer and the second insulation layer comprise a same material of the housing.

15. The sensor system of claim 9, wherein the insulation material of the housing comprises a poly dimethylsiloxane (PDMS) material.Attorney Docket No. 0184.0314-PCTClient Ref. No. C18042_P 18042-0216. The sensor system of claim 9, further comprising a second cantilevered sensor member comprising a second cantilevered sensor member fixed end and a second cantilevered sensor member movable end, wherein the second cantilevered sensor member fixed end is mounted to a second position on the interior surface of the housing, wherein the second cantilevered sensor member has a second characteristic mechanical signature that is based on one or more properties of the second cantilevered sensor member.

17. The sensor system of claim 9, further comprising a third cantilevered sensor member comprising a third cantilevered sensor member fixed end and a third cantilevered sensor member movable end, wherein the third cantilevered sensor member fixed end is mounted to a third position on the interior surface of the housing, wherein the third cantilevered sensor member has a third characteristic mechanical signature when actuated that is based on one or more properties of the third cantilevered sensor member.

18. The sensor system of claim 17, wherein the processor is connected to the first cantilevered sensor member, the second cantilevered sensor member, and the third cantilevered sensor member by a pair of wires.

19. The sensor system of claim 17, wherein the processor is configured to multiplex, demultiplex, or both multiplex and demultiplex signals from the first cantilevered sensor member, the second cantilevered sensor member, and the third cantilevered sensor member received over a pair of wires using a multiplexing algorithm, a demultiplexing algorithm, or both a multiplexing and demultiplexing algorithm.

20. The sensor system of claim 9, wherein the processor is arranged remote from the housing.

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