A robot plantar force distribution sensing system based on a flexible piezoresistive array

Abstract

The application provides a robot sole force distribution sensing system based on a flexible piezoresistive array, and relates to the technical field of robot sole force sensing. The system comprises a flexible sensing array module, an acquisition control module and an upper computer; wherein the acquisition control module comprises a region gating control module, a multiplexer and a master control module. The application has the advantages of good flexibility, strong anti-interference, low cost and high integration, can acquire robot sole pressure distribution information in real time and accurately, provides reliable data support for balance control, gait planning and terrain self-adaptation of the foot-type robot, and is suitable for military robots, medical assistance, security inspection and other fields.

Description

Technical Field

[0001] This invention relates to the field of robot foot force sensing technology, specifically to a robot foot force distribution sensing system based on a flexible piezoresistive array. Background Technology

[0002] Real-time perception of plantar pressure distribution is crucial for legged robots to achieve gait planning, balance control, and terrain adaptation when walking in complex, unstructured environments (such as stairs, grass, and rugged mountain paths). Existing plantar force sensing technologies suffer from the following shortcomings: 1. Traditional rigid sensor solutions, such as six-dimensional force sensors, are large and heavy, making it difficult to conform to the curvature of the foot. They are also prone to damage due to stress concentration under the high-frequency impacts generated by robot walking. In addition, rigid sensors can usually only measure total force and torque, and cannot accurately sense the pressure distribution in different areas of the foot.

[0003] 2. Existing flexible sensor solutions: Some technologies (such as air cavity solutions) are sensitive to ambient temperature, are easily affected by thermal expansion, and can only sense the total pressure of the area, resulting in low spatial resolution; other solutions (such as visual-tactile sensors or flexible magnetic film sensors) have large hardware volume, high power consumption, and high cost, making it difficult to achieve lightweight and low-cost integration in the robot's foot.

[0004] 3. Challenges in signal acquisition and integration: Array sensors suffer from signal crosstalk, and multi-channel data acquisition requires complex hardware support, making system integration difficult.

[0005] Therefore, there is an urgent need for a robot foot force distribution sensing system that is flexible, has strong anti-interference capabilities, low cost, high integration, and can acquire real-time foot force distribution. Summary of the Invention

[0006] The purpose of this invention is to provide a robot foot pressure distribution sensing system based on a flexible piezoresistive array, which has the advantages of good flexibility, strong anti-interference ability, low cost and high integration. It can acquire foot pressure distribution information in real time and accurately, and provide reliable data support for balance control, gait planning and terrain adaptation of legged robots.

[0007] To achieve the above objectives, the present invention provides a robot foot force distribution sensing system based on a flexible piezoresistive array, comprising a flexible sensor array module, a data acquisition and control module, and a host computer; the data acquisition and control module includes a region gating control module, a multiplexer, and a main control module; The flexible sensor array module includes a flexible substrate and multiple flexible piezoresistive sensors disposed on the flexible substrate. The flexible substrate is attached to the bottom of the robot's foot, which is divided into multiple zones, each zone corresponding to at least one flexible piezoresistive sensor. The area gating control module, multiplexer, and host computer are all connected to the main control module. Multiple flexible piezoresistive sensors are connected to multiple input channels of the multiplexer respectively; the main control module is used to output timing control signals to control the area selection control module to start the flexible piezoresistive sensors in multiple zones in a time-division manner, and to collect the pressure analog signals output by the corresponding flexible piezoresistive sensors through the multiplexer, and then convert the pressure analog signals into pressure digital signals. The host computer receives the pressure digital signal and, based on the location of multiple flexible piezoresistive sensors, reconstructs the corresponding pressure digital signal into a continuous pressure field and generates a pressure distribution map.

[0008] According to the present invention, a robot foot force distribution sensing system based on a flexible piezoresistive array is provided, wherein the main control module is wirelessly connected to the host computer via WiFi and / or Bluetooth.

[0009] According to the present invention, a robot foot force distribution sensing system based on a flexible piezoresistive array is provided, wherein the robot foot is divided into four zones: heel zone, midfoot zone, metatarsal zone, and toe zone.

[0010] According to the present invention, a robot foot force distribution sensing system based on a flexible piezoresistive array is provided, the host computer comprising: The contour coordinate extraction unit is used to parse the DXF file containing the robot's foot contour and the coordinate information of the flexible piezoresistive sensor, and automatically extract the position of the flexible piezoresistive sensor. The continuous pressure field construction unit is used for spatial interpolation based on the Gaussian kernel function to map discrete digital pressure signals into a continuous pressure field distribution within the robot's foot region. The dynamic visualization unit is used to dynamically generate a pressure heat map based on the continuous pressure field distribution, showing the spatiotemporal changes in the pressure distribution on the robot's foot.

[0011] According to the present invention, a robot foot force distribution sensing system based on a flexible piezoresistive array is provided. The acquisition and control module further includes a filtering module. The filtering module includes multiple RC low-pass filter circuits. Each flexible piezoresistive sensor is connected to one RC low-pass filter circuit and then connected to the corresponding input channel.

[0012] According to the present invention, a robot foot force distribution sensing system based on a flexible piezoresistive array is provided, wherein the main control module includes a microcontroller.

[0013] According to the present invention, a robot foot force distribution sensing system based on a flexible piezoresistive array is provided. The region selection control module includes multiple high-side switches, each corresponding to a different zone. The main control module controls the multiple high-side switches to open in a time-division manner by outputting timing control signals.

[0014] According to the present invention, a robot foot force distribution sensing system based on a flexible piezoresistive array is provided. The microcontroller uses an ESP32 chip, the high-side switch uses a switching transistor, and the multiplexer uses a CD74HC4067 chip.

[0015] According to the present invention, a robot foot force distribution sensing system based on a flexible piezoresistive array is provided. The acquisition and control module further includes a power supply module. Multiple input pins of a multiplexer are connected to corresponding flexible piezoresistive sensors via RC low-pass filter circuits. The output pin of the multiplexer is connected to the ADC pin of the microcontroller. Multiple channel selection pins of the multiplexer are connected to multiple GPIO pins of the microcontroller. The source of each high-side switch is connected to the power supply module, the drain is connected to all flexible piezoresistive sensors in the corresponding partition, and the gate is connected to the corresponding GPIO pin of the microcontroller via a current-limiting resistor. A pull-up resistor is connected between the source and gate of each high-side switch.

[0016] According to the present invention, a robot foot force distribution sensing system based on a flexible piezoresistive array is provided, wherein the flexible substrate is a flexible printed circuit board.

[0017] Compared with the prior art, the present invention has at least the following technical effects: 1. High flexibility and excellent fit. Using FPC as the carrier and flexible piezoresistive sensor, the overall structure has good flexibility, can closely fit the curved surface of the robot's foot, and is impact-resistant, fatigue-resistant, and not easily damaged.

[0018] 2. Strong anti-interference capability. The use of switching transistors, such as P-channel MOSFETs, for time-division multiplexing solves the problem of crosstalk in array sensor signals at its source; combined with an RC low-pass filter circuit, high-frequency noise is effectively filtered out, ensuring high-precision acquisition of weak pressure signals.

[0019] 3. Low cost and low power consumption. It adopts commercially available flexible piezoresistive sensors and general-purpose microcontrollers, such as the ESP32 chip, resulting in low material costs; the overall power consumption of the system is reduced through time-sharing power supply.

[0020] 4. High integration and easy deployment. Utilizing a multiplexer, multiple pressure analog signals can be acquired using only one ADC channel of the main control module, simplifying circuit design; wireless communication methods, such as WiFi / Bluetooth, eliminate the need for complex wiring.

[0021] 5. High level of visualization. The software can automatically extract sensor coordinates, construct continuous pressure heat maps, and generate dynamic animations via a host computer, providing researchers with an intuitive data analysis tool. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] In the attached diagram: Figure 1 This is a block diagram of the robot foot force distribution sensing system based on a flexible piezoresistive array according to the present invention. Figure 2 This is a distribution diagram of the flexible piezoresistive sensor of the present invention in the robot's foot section; Figure 3 This is a physical diagram of the flexible sensor array module and the acquisition control module of the present invention; Figure 4 This is a circuit structure diagram of the power module of the present invention; Figure 5 This is a circuit structure diagram of the region selection control module of the present invention; Figure 6 This is a circuit structure diagram of the filtering module of the present invention; Figure 7 This is a circuit diagram of the multiplexer of the present invention; Figure 8 This is a circuit diagram of the main control module of the present invention; Figure 9 This is a schematic diagram showing the position of the flexible piezoresistive sensor on the FPC during the experiment of this invention; Figure 10a , Figure 10b , Figure 10c , Figure 10d and Figure 10e These are pressure thermograms of five gait keyframe sequences during the experiment of this invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0025] The following detailed description of some embodiments of the present invention will be provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] Please see Figure 1This invention provides a robot foot force distribution sensing system based on a flexible piezoresistive array, comprising: 1. A flexible sensor array module 10 includes a flexible substrate and multiple flexible piezoresistive sensors disposed thereon. The flexible substrate can be a flexible printed circuit board (FPC), and the multiple flexible piezoresistive sensors are integrated on the flexible substrate. The flexible substrate is attached to the bottom of the robot's foot, which is divided into multiple zones, each zone corresponding to at least one flexible piezoresistive sensor. Therefore, the multiple flexible piezoresistive sensors form an array-arranged sensor network within each zone according to a preset bottom zone layout. The multiple flexible piezoresistive sensors are respectively connected to multiple input channels of a multiplexer.

[0027] 2. Acquisition and control module, connected to the flexible sensor array module, including: Power module 20 is used to provide a stable operating voltage.

[0028] The area selection control module 30 includes multiple high-side switches, each corresponding to a different zone. The main control module 60 controls the multiple high-side switches to open in a time-sharing manner by outputting timing control signals.

[0029] The filtering module 40 includes multiple RC low-pass filter circuits. Each flexible piezoresistive sensor is connected to one RC low-pass filter circuit and then to its corresponding input channel. The RC low-pass filter circuits are used to filter out high-frequency noise in the pressure analog signal.

[0030] Multiplexer 50, connected to filter module 40, is used to time-division multiplex multiplexed pressure analog signals into a single pressure analog signal output. Multiplexer 50 can use a CD74HC4067 chip. Multiple input pins of multiplexer 50 are connected to corresponding flexible piezoresistive sensors via RC low-pass filter circuits. Output pins of multiplexer 50 are connected to the ADC pins of the microcontroller. Multiple channel selection pins of multiplexer 50 are connected to multiple GPIO pins of the microcontroller. High-side switches can be transistors. The source of each high-side switch is connected to the power supply module, the drain is connected to all flexible piezoresistive sensors within the corresponding zone, and the gate is connected to the corresponding GPIO pin of the microcontroller via a first resistor. A pull-up resistor is connected between the source and gate of each high-side switch.

[0031] The main control module 60 includes a microcontroller (such as an ESP32 chip), which is connected to the regional gating control module 30 and the multiplexer 50. It is used to output timing control signals and to acquire the pressure analog signals output by the corresponding flexible piezoresistive sensors through the multiplexer 50, and then convert the pressure analog signals into pressure digital signals.

[0032] 3. The host computer 70 is connected to the main control module 60 and is used to receive pressure digital signals. Based on the location of multiple flexible piezoresistive sensors, it reconstructs the corresponding pressure digital signals into a continuous pressure field and generates a pressure distribution map.

[0033] In at least one embodiment of the present invention, the flexible substrate is an FPC designed according to the shape of the robot's foot, and the foot is divided into a heel area, a midfoot area, a metatarsal area, and a toe area.

[0034] In at least one embodiment of the present invention, the high-side switch is a switching transistor, such as a P-channel MOSFET. The source of each high-side switch is connected to the power module 20, the drain is connected to all flexible piezoresistive sensors in the corresponding partition, and the gate is connected to the corresponding GPIO pin of the microcontroller through a current-limiting resistor. A pull-up resistor is connected between the source and the gate of each high-side switch, that is, the power module is connected through the pull-up resistor.

[0035] In at least one embodiment of the present invention, the filtering module 40 includes a multi-channel RC low-pass filter circuit, one end of which is connected to the output terminal of the flexible piezoresistive sensor and the other end of which is connected to the input terminal of the multiplexer 50.

[0036] In at least one embodiment of the present invention, the main control module 60 adopts a microcontroller, such as an ESP32 chip, which supports WiFi and / or Bluetooth wireless communication, thereby enabling the main control module 60 to wirelessly connect with the host computer 70 via WiFi and / or Bluetooth.

[0037] In at least one embodiment of the present invention, the host computer 70 includes: The contour coordinate extraction unit parses the DXF file containing the robot's foot contour and the coordinate information of the flexible piezoresistive sensor, and automatically extracts the position of the flexible piezoresistive sensor. Continuous pressure field construction unit: used for spatial interpolation based on Gaussian kernel function to map discrete digital pressure signals into a continuous pressure field distribution within the robot's foot plate; Dynamic visualization unit: used to dynamically generate pressure heat maps based on the continuous pressure field distribution, showing the spatiotemporal changes of the pressure distribution on the robot's foot.

[0038] In summary, the robot foot force distribution sensing system based on a flexible piezoresistive array provided by this invention includes: a flexible sensor array module, a data acquisition and control module, and a host computer. The flexible sensor array module uses a flexible printed circuit board (FPC) as a substrate and integrates multiple flexible piezoresistive sensors, arranged according to the functional zones of the robot foot. The data acquisition and control module includes a power supply module, a region selection control module, a filtering module, a multiplexer, and a main control module. The region selection control module selects the flexible piezoresistive sensors region by region in a time-division manner, suppressing signal crosstalk at its source; the filtering module filters out high-frequency noise; the multiplexer switches multiple analog pressure signals to a single ADC for acquisition in a time-division manner, simplifying the circuit structure. The host computer automatically extracts the position of the flexible piezoresistive sensors, reconstructs the discrete pressure digital signals into a continuous pressure field distribution based on a Gaussian kernel function, and dynamically generates a pressure heatmap. This invention has the advantages of good flexibility, strong anti-interference ability, low cost and high integration. It can acquire the pressure distribution information of the robot's foot in real time and accurately, providing reliable data support for the balance control, gait planning and terrain adaptation of legged robots. It is applicable to military robots, medical assistance and security inspection fields.

[0039] The following is a specific embodiment of the present invention.

[0040] like Figure 1 As shown, this embodiment provides a robot foot force distribution sensing system based on a flexible piezoresistive array and ESP32, including a flexible sensor array module, a data acquisition and control module, and a host computer, as detailed below: 1. Flexible sensor array module like Figure 2 and Figure 3 As shown, 16 flexible piezoresistive sensors (model IMS-C10A-50kg) were selected and arranged according to the functional zones of the robot's foot (2 in the heel, 6 in the midfoot, 6 in the metatarsals, and 2 in the toes). A 42-size FPC (Flexible Printed Circuit) with the shape of the robot's foot was used as the substrate. The electrode traces of all the flexible piezoresistive sensors were integrated onto the FPC, and the signal, power, and ground lines were led out through a 22-pin gold-fingered FPC connector. The FPC substrate was PET. This design allows the sensor array to fit snugly against the robot's foot and provides excellent impact resistance.

[0041] 2. Data Acquisition and Control Module like Figure 4 As shown, the power module uses a USB Type-C interface to input 5V voltage, which is converted to 3.3V voltage through a linear regulator (model AMS1117-3.3). A 10μF electrolytic capacitor and a 100nF ceramic capacitor are connected in parallel at the input for filtering. A 100nF ceramic decoupling capacitor and a 10μF electrolytic capacitor are placed near the chip pins at the output to provide a stable, clean, and low-noise 3.3V power supply for the entire system.

[0042] like Figure 5 As shown, the region selection control module uses four P-channel MOSFETs (model AO3401A, designated Q1-Q4) as high-side switches. The source (S) of each MOSFET is connected to 3.3V, the drain (D) is connected to the power supply terminals (VCC1-VCC4) of all flexible piezoresistive sensors within the corresponding region, and the gate (G) is connected to the GPIO pin of the ESP32 via a 10kΩ resistor and pulled up to 3.3V via a 100kΩ resistor. A low-level output from the main control module controls the MOSFETs to turn on, enabling region-by-region selection of sensors within each region and avoiding signal crosstalk.

[0043] like Figure 6 As shown, the filtering module includes 16 identical RC low-pass filter circuits. Each RC low-pass filter circuit consists of a 10kΩ resistor and a 100nF ceramic capacitor connected in parallel, with a cutoff frequency of approximately 159Hz, used to filter out high-frequency noise in the sensor signal.

[0044] like Figure 7 As shown, the multiplexer uses the CD74HC4067 chip. Its 16 input pins are connected to 16 filtered signals from flexible piezoresistive sensors (i.e., pressure analog signals), and its output pins are connected to the ADC pins of the ESP32. Its four channel selection pins (S0-S3) are connected to the four GPIO pins of the ESP32. The binary address is set by the main control module, and the 16 sensing signals are time-division multiplexed to a single ADC for acquisition.

[0045] like Figure 8 As shown, the main control module uses the ESP32-S3-WROOM-1 module. Its minimum system circuit includes a reset circuit, a BOOT download circuit, and an LED indicator circuit. The ESP32 is responsible for controlling the timing of the MOSFET and the CD74HC4067 chip, acquiring the pressure analog signal and converting it into a pressure digital signal, and transmitting the pressure digital signal to the host computer via WiFi or Bluetooth.

[0046] The system's operating sequence is as follows: The ESP32 first controls the MOSFET to select all flexible piezoresistive sensors in the first partition, and then controls the CD74HC4067 chip to sequentially switch the sensing signals of the multiple flexible piezoresistive sensors in the first partition. After the signal stabilizes, the ADC value is acquired. After acquiring data for one partition, the MOSFET in that partition is turned off, and the next partition is selected. This process is repeated until all 16 sensing signals from the four partitions are acquired.

[0047] 3. Host computer In this embodiment, the host computer is implemented using a Python program. First, the DXF file exported from EDA is parsed using the ezdxf library, automatically extracting the contour coordinates of the FPC and the center coordinates of the flexible piezoresistive sensors labeled 1-16. Then, the host computer receives time-series CSV data from the ESP32 via an HTTP request. Using the scipy library, spatial interpolation based on a Gaussian kernel function is performed to map the readings of the 16 discrete flexible piezoresistive sensor points onto a continuous grid within the plantar contour. Finally, combining the masking techniques and animation functions of the matplotlib library, a pressure heatmap is dynamically drawn within the robot's plantar contour area.

[0048] The system of this invention was used to conduct data collection and recognition experiments for five gait types: walking, running, climbing stairs, walking backwards, and fatigue walking. Figure 9 This is a schematic diagram showing the position of the flexible piezoresistive sensor on the FPC during the experiment of this invention. Figure 10a , Figure 10b , Figure 10c , Figure 10d and Figure 10e The images show pressure heatmaps of keyframe sequences (one-fifth, two-fifths, three-fifths, four-fifths, and one frame, respectively) from the experimental stages of walking, running, climbing stairs, walking backwards, and walking while fatigued. The pressure heatmaps clearly demonstrate the spatiotemporal characteristics of pressure distribution under different time states, such as the smooth transition from hindfoot to forefoot during walking, the forefoot dominance and high-pressure peak during running, the concentrated force on the midfoot and forefoot during climbing stairs, the reverse force sequence during walking backwards, and the dispersed and dragging force characteristics during walking while fatigued. Experiments prove that the system can stably and accurately collect and present plantar pressure distribution information, exhibiting excellent response speed and practicality.

[0049] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the embodiments disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. It should be understood that the invention is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A robot foot force distribution sensing system based on a flexible piezoresistive array, characterized in that, It includes a flexible sensor array module, a data acquisition and control module, and a host computer; the data acquisition and control module includes a region gating control module, a multiplexer, and a main control module; The flexible sensor array module includes a flexible substrate and multiple flexible piezoresistive sensors disposed on the flexible substrate. The flexible substrate is attached to the bottom of the robot foot, and the bottom of the robot foot is divided into multiple zones, each zone corresponding to at least one flexible piezoresistive sensor. The region selection control module, the multiplexer, and the host computer are all connected to the main control module. Multiple flexible piezoresistive sensors are respectively connected to multiple input channels of the multiplexer; The main control module is used to output timing control signals to control the area selection control module to start the flexible piezoresistive sensors in multiple zones in a time-division manner, and to collect the pressure analog signals output by the corresponding flexible piezoresistive sensors through the multiplexer, and then convert the pressure analog signals into pressure digital signals. The host computer is used to receive pressure digital signals and, based on the locations of multiple flexible piezoresistive sensors, reconstruct the corresponding pressure digital signals into a continuous pressure field and generate a pressure distribution map.

2. The robot foot force distribution sensing system based on a flexible piezoresistive array according to claim 1, characterized in that, The main control module is wirelessly connected to the host computer via WiFi and / or Bluetooth.

3. The robot foot force distribution sensing system based on a flexible piezoresistive array according to claim 1, characterized in that, The robot's foot is divided into four zones: the heel zone, the midfoot zone, the metatarsal zone, and the toe zone.

4. The robot foot force distribution sensing system based on a flexible piezoresistive array according to claim 1, characterized in that, The host computer includes: The contour coordinate extraction unit is used to parse the DXF file containing the robot's foot contour and the coordinate information of the flexible piezoresistive sensor, and automatically extract the position of the flexible piezoresistive sensor. The continuous pressure field construction unit is used for spatial interpolation based on the Gaussian kernel function to map discrete digital pressure signals into a continuous pressure field distribution within the robot's foot region. The dynamic visualization unit is used to dynamically generate a pressure heat map based on the continuous pressure field distribution, and to display the spatiotemporal changes of the pressure distribution on the robot's foot.

5. The robot foot force distribution sensing system based on a flexible piezoresistive array according to claim 1, characterized in that, The acquisition and control module also includes a filtering module; the filtering module includes multiple RC low-pass filter circuits, and each flexible piezoresistive sensor is connected to one RC low-pass filter circuit and then connected to the corresponding input channel.

6. The robot foot force distribution sensing system based on a flexible piezoresistive array according to claim 5, characterized in that, The main control module includes a microcontroller.

7. The robot foot force distribution sensing system based on a flexible piezoresistive array according to claim 6, characterized in that, The area selection control module includes multiple high-side switches, each corresponding to a different zone. The main control module controls the multiple high-side switches to open in a time-sharing manner by outputting timing control signals.

8. The robot foot force distribution sensing system based on a flexible piezoresistive array according to claim 7, characterized in that, The microcontroller uses an ESP32 chip, the high-side switch uses a switching transistor, and the multiplexer uses a CD74HC4067 chip.

9. The robot foot force distribution sensing system based on a flexible piezoresistive array according to claim 8, characterized in that, The acquisition and control module also includes a power supply module; the multiple input pins of the multiplexer are respectively connected to the corresponding flexible piezoresistive sensors via RC low-pass filter circuits, the output pins of the multiplexer are connected to the ADC pins of the microcontroller, and the multiple channel selection pins of the multiplexer are respectively connected to the multiple GPIO pins of the microcontroller; the source of each high-side switch is connected to the power supply module, the drain is connected to all the flexible piezoresistive sensors in the corresponding partition, the gate is connected to the corresponding GPIO pin of the microcontroller via a current-limiting resistor, and a pull-up resistor is connected between the source and gate of each high-side switch.

10. The robot foot force distribution sensing system based on a flexible piezoresistive array according to claim 1, characterized in that, The flexible substrate is a flexible printed circuit board.

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