Flexible strain sensor array, shape sensing system and method

Abstract

The invention provides a flexible strain sensor array and a shape sensing system and method, and relates to the technical field of sensors. The sensor array comprises a flexible substrate layer; the strain layer comprises a common-ground circuit formed on the flexible substrate layer, a plurality of output channels and a plurality of strain sensing units arranged in an array; each strain sensing unit corresponds to one output channel; each strain sensing unit comprises a first conductive pattern and a second conductive pattern arranged in the first conductive pattern; one end of the first conductive pattern is connected with one end of the common-ground circuit; the other end of the first conductive pattern is connected with one end of the corresponding output channel; one end of the second conductive pattern is connected with one end of the common ground circuit; the other end of the second conductive pattern is connected with one end of the corresponding output channel; the packaging layer covers the strain layer on the substrate layer; and the other end of the common-ground circuit and the other end of the output channel corresponding to each strain sensing unit serve as the output end of the flexible strain sensor array.

Description

Technical Field

[0001] The present disclosure relates to the field of sensor technology, and more specifically, to a flexible strain sensor array, a shape sensing system and a method. Background Art

[0002] With its unique flexibility, adaptability and safety, flexible robots have shown broad application prospects in many fields. For example, limb rehabilitation training in the medical field, precision assembly in the industrial field, housework in the service field, pipeline inspection, ruins exploration, and rescue in small spaces in the exploration and rescue field. However, the application of flexible robots still faces some key challenges. For example, the sensors used in flexible robots are rigid, sensitive to humidity and temperature, easily affected by external magnetic fields, have poor anti-interference ability, or are complex to manufacture. Summary of the invention

[0003] In view of this, the present disclosure provides a flexible strain sensor array, a shape sensing system and a method.

[0004] One aspect of the present disclosure provides a flexible strain sensor array, comprising: a flexible substrate layer; a strain layer, comprising a common ground circuit formed on the flexible substrate layer, multiple output channels, and multiple strain sensing units arranged in an array; each of the strain sensing units corresponds to an output channel; each of the strain sensing units comprises a first conductive pattern and a second conductive pattern arranged in the first conductive pattern; one end of the first conductive pattern is connected to one end of the common ground circuit; the other end of the first conductive pattern is connected to one end of the corresponding output channel; one end of the second conductive pattern is connected to one end of the common ground circuit; the other end of the second conductive pattern is connected to one end of the corresponding output channel; and a packaging layer covering the strain layer on the substrate layer; wherein the other end of the common ground circuit and the other end of the output channel corresponding to each of the strain sensing units serve as output ends of the flexible strain sensor array.

[0005] According to an embodiment of the present disclosure, the above-mentioned first conductive pattern is in a rectangular shape; the above-mentioned first conductive pattern includes a first line segment, a second line segment, a third line segment and a fourth line segment; one end of the above-mentioned first line segment is connected to one end of the above-mentioned second line segment by a chamfer; the other end of the above-mentioned second line segment is connected to one end of the above-mentioned third line segment by a chamfer; the other end of the above-mentioned third line segment is connected to one end of the above-mentioned fourth line segment by a chamfer; the other end of the above-mentioned fourth line segment is connected to the other end of the above-mentioned first line segment by a chamfer; the above-mentioned second conductive pattern is in a U-shaped shape; one end of the above-mentioned second conductive pattern is connected to the above-mentioned first line segment; the other end of the above-mentioned second conductive pattern is connected to the above-mentioned third line segment.

[0006] According to an embodiment of the present disclosure, the material of the flexible base layer is thermoplastic polyurethane elastomer rubber.

[0007] According to an embodiment of the present disclosure, the materials of the first conductive pattern and the second conductive pattern include polydimethylsiloxane and multi-walled carbon nanotubes.

[0008] According to an embodiment of the present disclosure, the material of the encapsulation layer is polydimethylsiloxane.

[0009] Another aspect of the present disclosure provides a shape sensing system, comprising: a signal conditioning module, a shape sensing module and the above-mentioned flexible strain sensor array; the above-mentioned flexible strain sensor array is arranged at the end of the flexible robot; the above-mentioned flexible strain sensor array is used to output a resistance value array corresponding to the deformation of the above-mentioned flexible robot end; the above-mentioned signal conditioning module is connected to the above-mentioned flexible strain sensor array; the above-mentioned signal conditioning module is used to convert the above-mentioned resistance value array into a digital deformation signal; the above-mentioned shape sensing module is connected to the above-mentioned signal conditioning module; the above-mentioned deformation sensing module is used to construct a kinematic model of the above-mentioned flexible robot end, and input the above-mentioned digital deformation signal into the above-mentioned kinematic model to determine the deformation parameters of the above-mentioned flexible robot end; the above-mentioned deformation parameters include bending angle and bending direction.

[0010] According to an embodiment of the present disclosure, the above-mentioned signal conditioning module includes an analog-to-digital conversion unit and a multi-channel signal conditioning circuit; each channel of the above-mentioned signal conditioning circuit corresponds to a strain sensing unit of the above-mentioned flexible strain sensor array; the above-mentioned signal conditioning circuit includes an amplifier and a feedback unit; the above-mentioned feedback unit includes a feedback resistor and a feedback capacitor; the above-mentioned feedback capacitor and the above-mentioned feedback resistor are connected in parallel; the reverse input terminal of the above-mentioned amplifier is connected to the output terminal of the above-mentioned amplifier through the above-mentioned feedback unit; the reverse input terminal of the above-mentioned amplifier is also connected to the other end of the output channel of the corresponding strain sensing unit; the other end of the ground supply line of the above-mentioned corresponding strain sensing unit is connected to the ground wire; the positive input terminal of the above-mentioned amplifier is connected to a preset voltage signal; the output terminal of the above-mentioned amplifier is connected to the above-mentioned analog-to-digital conversion unit; the above-mentioned analog-to-digital conversion unit is used to convert the analog voltage signal output by the output terminal of the above-mentioned amplifier into a digital deformation signal; the above-mentioned analog-to-digital conversion unit is connected to the above-mentioned deformation sensing module.

[0011] According to an embodiment of the present disclosure, it also includes a flexible circuit; one end of the flexible circuit is connected to the output end of the flexible strain sensor array; the other end of the flexible circuit is connected to the signal conditioning module.

[0012] Another aspect of the present disclosure provides a shape sensing method, including: constructing a kinematic model of a flexible robot end; obtaining a resistance value array output by a flexible strain sensor array in the above-mentioned shape sensing system; inputting the above-mentioned resistance value array into the above-mentioned kinematic model to obtain deformation parameters of the above-mentioned flexible robot end; the above-mentioned deformation parameters include a bending angle and a bending direction.

[0013] According to an embodiment of the present disclosure, the process of constructing the kinematic model of the flexible robot includes: when the terminal of the flexible robot is not deformed, the plane perpendicular to the terminal of the flexible robot is taken as the XY plane, the X-axis and the Y-axis are set on the XY plane, and the central axis of the terminal of the flexible robot is taken as the Z-axis to construct a three-dimensional coordinate system; when the terminal of the flexible robot is deformed, based on the three-dimensional coordinate system, a first geometric relationship between the bending angle of the terminal of the flexible robot and the deformation amount and a second geometric relationship between the bending direction of the terminal of the flexible robot and the deformation amount are determined; when the terminal of the flexible robot undergoes a preset deformation amount, an array of resistance values ​​output by the flexible strain sensor array corresponding to the output of the flexible strain sensor array is obtained to obtain an initial data set; based on the initial data set, a mathematical relationship between the deformation amount of the terminal of the flexible robot and the array of resistance values ​​output by the flexible strain sensor array is determined; based on the mathematical relationship, the first geometric relationship and the second geometric relationship, a first corresponding relationship between the bending angle and the resistance value array and a second corresponding relationship between the bending direction and the resistance value array are determined, and the first corresponding relationship and the second corresponding relationship are used as the kinematic model of the terminal of the flexible robot.

[0014] According to the embodiments of the present disclosure, the preparation complexity of the flexible sensor array is reduced by arranging the strain layer and the packaging layer in sequence on the flexible base layer, and since the strain layer is encapsulated between the flexible base layer and the packaging layer, the anti-interference ability of the flexible sensor array is improved, and the sensitivity to humidity is reduced. Since the flexible base layer, the strain layer and the packaging layer are all flexible materials, the flexible sensor array can better fit the surface of the flexible robot and generate more precise strain according to the deformation of the flexible robot. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0016] Figure 1 The schematic diagram of the structure of the flexible strain sensor array according to the embodiment of the present disclosure is shown;

[0017] Figure 2 The schematic diagram of the preparation process of the flexible strain sensor array according to the embodiment of the present disclosure is schematically shown;

[0018] Figure 3 The structure diagram of a shape perception system according to another embodiment of the present disclosure is schematically shown;

[0019] Figure 4 A schematic diagram of a connection structure between a flexible circuit and a flexible strain sensor array according to an embodiment of the present disclosure is shown;

[0020] Figure 5 The structure diagram of the signal conditioning module according to the embodiment of the present disclosure is schematically shown;

[0021] Figure 6 The structure diagram of the signal conditioning circuit according to the embodiment of the present disclosure is schematically shown;

[0022] Figure 7 A flowchart of a shape perception method according to another embodiment of the present disclosure is schematically shown; and

[0023] Figure 8 A kinematic modeling reference diagram according to an embodiment of the present disclosure is schematically shown; wherein, Figure 8 (a) is a schematic diagram of the principle of a single flexible strain sensing unit when the flexible robot is bent. Figure 8 (b) is a top view of three flexible strain sensing units in the same row of the flexible strain sensor array when the flexible robot is bent. Figure 8 (c) is a schematic diagram of the principle of the flexible strain sensor array when the flexible robot is bent. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0025] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0026] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0027] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0028] In the embodiments of the present disclosure, the collection, updating, analysis, processing, use, transmission, provision, disclosure, storage, etc. of the data involved (for example, including but not limited to user personal information) are in compliance with the provisions of relevant laws and regulations, are used for legitimate purposes, and do not violate public order and good morals. In particular, necessary measures are taken for user personal information to prevent illegal access to user personal information data and maintain the security of user personal information and network security.

[0029] In the embodiments of the present disclosure, the user's authorization or consent is obtained before obtaining or collecting the user's personal information.

[0030] With the development of minimally invasive surgery, surgical robots have become a powerful tool for surgeons to perform complex operations. Compared with traditional open surgery, minimally invasive surgery can reduce patient trauma and recovery time through smaller incisions. Traditional rigid surgical robots increase the difficulty of operation and potential damage to surrounding tissues due to their limited flexibility. Flexible surgical robots are able to adapt to complex surgical environments due to their soft and bendable structure and flexibility similar to human organs, especially for applications such as natural cavity surgical robots and endoscopic surgical robots, which can pass through narrow and curved anatomical structures. This flexibility and compliance greatly improve the safety and effectiveness of surgery. However, the application of flexible surgical robots still faces some key challenges, such as the shape perception of the end instrument. In remote surgery or minimally invasive surgery, flexible robots need to operate in the narrow and curved anatomical structures of the human body. If the shape of the robot cannot be accurately sensed and controlled, it may touch or damage surrounding tissues, causing surgical complications. The application of shape perception technology can provide real-time feedback to doctors, help doctors monitor the posture of the robot, and ensure the safety of the operation.

[0031] Flexible strain sensors are sensors that can be attached to the surface of soft structures and produce resistance changes as they bend, and are less affected by external magnetic fields and electromagnetic interference. This type of sensor has high stretchability, high flexibility and sensitivity, and can be used for small deformations of flexible surgical robots.

[0032] At present, shape sensing technology in the field of flexible surgical robots mainly uses optical fiber and electromagnetic sensing. Shape sensing based on flexible sensors has some applications in industrial soft robots, mainly capacitive sensing. It includes shape sensing systems based on fiber Bragg grating sensors, shape sensing systems based on electromagnetic sensors, and shape sensing systems based on capacitive sensors.

[0033] 1. Shape perception system based on fiber Bragg grating sensor. Fiber Bragg grating sensors are widely used in flexible surgical robots to measure the deformation of flexible robots during operation. This sensor senses the shape of the end of the flexible robot by measuring the strain change in the optical fiber. The main drawback of this technical solution is that due to the poor stretchability of the fiber Bragg grating sensor, its response to bending and stretching is limited, and the installation is complicated and easily disturbed by the external environment, especially the high sensitivity to humidity and temperature, which affects the accuracy of shape perception.

[0034] 2. Shape perception system of electromagnetic sensors. Electromagnetic sensors monitor the changes in the magnetic field around the soft robot to deduce its position and deformation in three-dimensional space. Magnetic sensors or magnetic materials are installed on the robot to detect its deformation through the external magnetic field. This technical solution often performs poorly in complex surgical environments, and the interference of the magnetic field makes the measurement unstable. In addition, the installation of magnetic sensors is relatively complex, and their accuracy is greatly affected by the distribution of the external magnetic field, which is prone to error accumulation and cannot provide real-time high-precision shape perception.

[0035] 3. Shape perception system based on capacitive sensors. Capacitive sensors sense robot deformation by detecting changes in capacitance. The capacitance value of the sensor changes to varying degrees with bending or twisting, and the shape of each section of the robot can be deduced using the capacitance change value. Although capacitive sensors have good flexibility, their signals are easily affected by the external environment, especially humidity, temperature, and external electromagnetic noise. In addition, the manufacturing process of capacitive sensors usually requires high-precision geometric structures to ensure that changes in capacitance can accurately reflect deformation, increasing manufacturing costs. Flexible capacitive sensors require a certain amount of space to form a stable electric field, which will face limitations in small-size applications.

[0036] An embodiment of the present disclosure provides a flexible strain sensor array, comprising: a flexible substrate layer; a strain layer, comprising a common ground circuit formed on the flexible substrate layer, multiple output channels, and multiple strain sensing units arranged in an array; each strain sensing unit corresponds to an output channel; each strain sensing unit comprises a first conductive pattern and a second conductive pattern arranged in the first conductive pattern; one end of the first conductive pattern is connected to one end of the common ground circuit; the other end of the first conductive pattern is connected to one end of the corresponding output channel; one end of the second conductive pattern is connected to one end of the common ground circuit; the other end of the second conductive pattern is connected to one end of the corresponding output channel; and a packaging layer covering the strain layer on the substrate layer; wherein the other end of the common ground circuit and the other end of the output channel corresponding to each strain sensing unit serve as the output end of the flexible strain sensor array.

[0037] Figure 1 The schematic diagram of the structure of a flexible strain sensor array according to an embodiment of the present disclosure is shown schematically.

[0038] like Figure 1 As shown, the flexible strain sensor array is a sensor having a plurality of flexible strain sensing units, and the plurality of flexible strain sensing units are arranged in an array. Taking a 3×3 flexible strain sensor array as an example, the flexible strain sensor array includes a common ground circuit and nine output channels. The flexible strain sensor array includes strain sensing units 101, strain sensing units 102, strain sensing units 103, strain sensing units 104, strain sensing units 105, strain sensing units 106, strain sensing units 107, strain sensing units 108, strain sensing units 109, an output channel 118 corresponding to the strain sensing unit 101, an output channel 117 corresponding to the strain sensing unit 102, an output channel 116 corresponding to the strain sensing unit 103, an output channel 111 corresponding to the strain sensing unit 104, an output channel 112 corresponding to the strain sensing unit 105, an output channel 115 corresponding to the strain sensing unit 106, an output channel 110 corresponding to the strain sensing unit 107, an output channel 112 corresponding to the strain sensing unit 108, an output channel 113 corresponding to the strain sensing unit 109, and a common ground circuit 119. A 3×3 integrated flexible strain sensor array 302 is designed according to the size of the flexible robot and wrapped outside the end of the flexible robot to form a uniform sensor array. The end of the flexible robot may be cylindrical.

[0039] According to an embodiment of the present disclosure, the first conductive pattern is in a rectangular shape; the first conductive pattern includes a first line segment, a second line segment, a third line segment and a fourth line segment; one end of the first line segment is connected to one end of the second line segment by a chamfer; the other end of the second line segment is connected to one end of the third line segment by a chamfer; the other end of the third line segment is connected to one end of the fourth line segment by a chamfer; the other end of the fourth line segment is connected to the other end of the first line segment by a chamfer; the second conductive pattern is in a U-shaped shape; one end of the second conductive pattern is connected to the first line segment; the other end of the second conductive pattern is connected to the third line segment.

[0040] According to an embodiment of the present disclosure, the material of the flexible base layer is thermoplastic polyurethane elastomer rubber. The materials of the first conductive pattern and the second conductive pattern include polydimethylsiloxane and multi-walled carbon nanotubes. The material of the encapsulation layer is polydimethylsiloxane.

[0041] According to the embodiment of the present disclosure, the substrate is TPU material, which has strong stretchability, and the flexible sensing unit is selected to mix multi-walled carbon nanotube conductive filler in PDMS with large stretchability, and the U-shaped structure design of the strain sensing unit enhances its stretchability to a certain extent. The second conductive pattern can include a U-shaped pattern or multiple U-shaped patterns, each U-shaped pattern presents a U-shaped structure, and each U-shaped pattern includes multiple line segments, and multiple line segments are chamfered and connected in sequence to form a U-shaped structure. One end of the first line segment of each U-shaped structure is the starting end of the U-shaped structure, and one end of the last line segment is the terminal end of the U-shaped structure, the starting end is connected to the first line segment, and the terminal end is connected to the third line segment. The second conductive pattern includes multiple places where each line segment is connected to other line segments, and chamfer design is performed, which can increase the toughness of the connecting part of the line segment in the U-shaped structure. The connection between the line segment corresponding to each side of the rectangular shape of the first conductive pattern and the line segment corresponding to other sides of the rectangular shape is also chamfered, which increases the toughness and tensile performance of the first conductive pattern. Therefore, the prepared sensor has good flexibility and tensile performance. The signal transmission of the flexible strain sensor array is based on the instantaneous change of resistance. The response of the conductive material to the deformation is directly reflected in the resistance. Therefore, the signal response speed is fast, and it has the characteristics of high integration and small size.

[0042] According to the embodiments of the present disclosure, the flexible strain sensor array is very suitable for application in small surgical robots with complex deformations. Its excellent flexibility, stretchability and response speed can stably and quickly respond to bending and stretching operations during surgery in complex deformations, reducing delays.

[0043] According to the embodiments of the present disclosure, the flexible strain sensor array works on the principle of strain detection based on resistance change. Compared with capacitive sensors and electromagnetic sensors, it does not rely on changes in electric or magnetic fields, and is therefore not affected by external electromagnetic noise. This enables it to maintain stable working performance in complex electromagnetic environments (operating rooms). The selected base material and conductive seasoning have good chemical and physical stability, are not easily affected by the chemical substances and physical environment (temperature, humidity) in the external environment, and therefore have good anti-interference capabilities.

[0044] According to the embodiments of the present disclosure, a flexible strain sensor with a U-shaped structure is used, which can fit tightly on the surface of a flexible robot. At the same time, the U-shaped flexible strain sensor has the characteristic of changing resistance with deformation, and is more sensitive to small strains. The material of the strain sensing unit is highly flexible and suitable for complex three-dimensional shape perception. In addition, the selected conductive filler carbon nanotubes have extremely high sensitivity and can quickly sense small strain changes. This sensitivity ensures that the sensor can provide rapid feedback even when deformed slightly, thereby improving the accuracy of shape perception.

[0045] Figure 2 The schematic diagram of the preparation process of the flexible strain sensor array according to the embodiment of the present disclosure is schematically shown.

[0046] like Figure 2As shown, the flexible strain sensor array includes a TPU (Thermoplastic Polyurethane, thermoplastic polyurethane elastomer rubber) substrate 201, a silver paste circuit 202, a flexible strain sensing unit 203, and a PDMS (Polydimethylsiloxane, polydimethylsiloxane) encapsulation layer 204. The preparation process of the flexible strain sensor unit 203 includes: weighing 10g of PDMS solution and 1g of cross-linking agent, ultrasonic stirring for 30min until dense bubbles are generated, and then adding 0.78g of multi-walled carbon nanotubes and 0.5g of silicone oil dispersant and magnetic stirring for 30min until the raw materials form a uniform colloid. The silver paste is placed in a dispensing cylinder, and the silver paste circuit is printed on the TPU substrate 201 using the dispensing technology of a microelectronic printer. After printing, the electrodes of the FPC (Flexible Printed Circuit, flexible printed circuit board) flexible circuit 03 are placed on the TPU substrate 201 corresponding to each channel of the silver paste circuit, and heated at 90°C for 20min. After the silver paste is cured, the prepared colloid is placed in the dispensing cylinder, and the dispensing technology of the microelectronic printer is used to print the flexible strain sensing unit on the TPU substrate 201 with the silver paste circuit. After the printing is completed, it is heated at 90°C for 20 minutes. After the flexible strain sensing unit is cured, 5g of PDMS solution and 0.5g of cross-linking agent are weighed again and ultrasonically stirred for 30 minutes to produce dense bubbles. The stirred PDMS is placed in the dispensing cylinder, and the scraping technology of the microelectronic printer is used to scrape PDMS on the surface of the flexible sensing unit for packaging. After the scraping is completed, it is heated at 90°C for 20 minutes. After standing for 24 hours, a flexible strain sensor array 302 is obtained. Among them, the model of the microelectronic printer is not limited, and a DB100 microelectronic printer can be selected. According to the embodiment of the present disclosure, the preparation process of the flexible strain sensor array combines modern manufacturing technologies such as dispensing, scraping and other technologies to integrate multiple flexible strain sensing units on a substrate, reducing the complexity of connection and installation. Through a simplified manufacturing process, an integrated multi-dimensional flexible sensor can be mass-produced at a lower cost. Compared with the strict requirements of capacitive sensors on geometric accuracy, the flexible strain sensor of the present invention is simple to manufacture, low in cost, and suitable for commercial promotion.

[0047] The embodiment of the present disclosure provides a shape perception system, including a signal conditioning module, a shape perception module and a flexible strain sensor array. The flexible strain sensor array is arranged at the end of the flexible robot; the flexible strain sensor array is used to output a resistance value array corresponding to the deformation of the end of the flexible robot; the signal conditioning module is connected to the flexible strain sensor array; the signal conditioning module is used to convert the resistance value array into a digital deformation signal; the shape perception module is connected to the signal conditioning module; the deformation perception module is used to construct a kinematic model of the end of the flexible robot, and input the digital deformation signal into the kinematic model to determine the deformation parameters of the end of the flexible robot; the deformation parameters include bending angle and bending direction.

[0048] Figure 3 A schematic diagram of the structure of a shape perception system according to another embodiment of the present disclosure is shown schematically.

[0049] like Figure 3 As shown, the shape perception system includes a signal conditioning module 304, a shape perception module and a flexible strain sensor array 302, and may also include a Bluetooth module 305 and a host computer. Taking a flexible robot used for pipeline detection as an example, the flexible strain sensor array 302 is attached to the end of the flexible robot 301. During the use of the flexible robot 301, the technician operates the flexible robot 301 to enter the pipeline to be detected. The flexible strain sensor array 302 is deformed by the bending of the flexible robot end. The resistance of the flexible sensing unit changes due to tension or pressure. The flexible sensor array transmits the signal to the signal conditioning circuit 304. The signal conditioning circuit 304 converts the inversely proportional resistance into a proportionally proportional voltage signal. The shape perception module determines the deformation parameter according to the voltage signal, and transmits the deformation parameter to the host computer through the Bluetooth module 305, so as to realize the real-time display of the shape change of the end of the flexible robot 301. The shape sensing system can also use the host computer as a deformation sensing module. The signal conditioning circuit 304 uploads the voltage signal to the host computer through the Bluetooth module 305, and the host computer determines the shape change of the end of the flexible robot 301 according to the voltage signal.

[0050] According to an embodiment of the present disclosure, it also includes a flexible circuit; one end of the flexible circuit is connected to the output end of the flexible strain sensor array; and the other end of the flexible circuit is connected to the signal conditioning module.

[0051] Figure 4 The figure schematically shows a connection structure diagram of a flexible circuit connecting a flexible strain sensor array according to an embodiment of the present disclosure.

[0052] like Figure 4As shown, electrode 401 of the FPC flexible circuit board is connected to output channel 119 of the flexible sensor array 302, electrode 402 of the FPC flexible circuit board is connected to output channel 118 of the flexible sensor array 302, electrode 403 of the FPC flexible circuit board is connected to output channel 117 of the flexible sensor array 302, electrode 404 of the FPC flexible circuit board is connected to output channel 116 of the flexible sensor array 302, electrode 405 of the FPC flexible circuit board is connected to output channel 111 of the flexible sensor array 302, electrode 406 of the FPC flexible circuit board is connected to output channel 112 of the flexible sensor array 302, electrode 407 of the FPC flexible circuit board is connected to output channel 115 of the flexible sensor array 302, electrode 408 of the FPC flexible circuit board is connected to output channel 110 of the flexible sensor array 302, electrode 409 of the FPC flexible circuit board is connected to output channel 113 of the flexible sensor array 302, and electrode 410 of the FPC flexible circuit board is connected to output channel 114 of the flexible sensor array 302. The electrode part of the FPC flexible circuit 303 is wound around the rigid part of the flexible robot end 301, realizing the integrated design of the flexible surgical robot end, the flexible sensor array sensor, and the signal transmission circuit. The strain parameters of the shape of the flexible robot end are collected through the voltage signal changes of the nine channels displayed by the host computer.

[0053] According to an embodiment of the present disclosure, the signal conditioning module includes an analog-to-digital conversion unit and a multi-channel signal conditioning circuit; each signal conditioning circuit corresponds to a strain sensing unit of the flexible strain sensor array; the signal conditioning circuit includes an amplifier and a feedback unit; the feedback unit includes a feedback resistor and a feedback capacitor; the feedback capacitor and the feedback resistor are connected in parallel; the reverse input terminal of the amplifier is connected to the output terminal of the amplifier through the feedback unit; the reverse input terminal of the amplifier is also connected to the other end of the output channel of the corresponding strain sensing unit; the other end of the ground supply line of the corresponding strain sensing unit is connected to the ground wire; the positive input terminal of the amplifier is connected to a preset voltage signal; the output terminal of the amplifier is connected to the analog-to-digital conversion unit; the analog-to-digital conversion unit is used to convert the analog voltage signal output by the output terminal of the amplifier into a digital deformation signal; the analog-to-digital conversion unit is connected to the deformation sensing module.

[0054] Figure 5 The structure diagram of the signal conditioning module according to the embodiment of the present disclosure is schematically shown.

[0055] like Figure 5 As shown, the signal conditioning module may also include a Bluetooth module. Multiple signal conditioning circuits convert the resistance value output by the flexible strain sensor array collected into a voltage signal and transmit it to the analog-to-digital conversion unit. The analog-to-digital conversion unit converts the voltage signal into a digital signal and converts the digital signal to the deformation sensing module through the Bluetooth module.

[0056] According to the embodiment of the present disclosure, a 5V voltage is reduced to 1.2V by means of a resistor voltage divider and then input to the positive input terminal of the amplifier. The flexible sensor array is equivalent to a potentiometer connected to the reverse input terminal of the amplifier. The amplifier output terminal and the reverse input terminal are connected to a resistor to realize the function of active reverse amplification. One end of the potentiometer equivalent to the flexible sensor array is connected to the reverse input terminal of the amplifier, and the other end is connected to the ground. Figure 6 A1, A2, A3, A4, A5, A6, A7, A8 and A9 are the output signals of the amplifier. The nine output voltage signals are converted into digital signals and communicate with the host computer using the MQTT protocol. After data processing, the real-time shape changes of the end of the flexible robot are displayed on the host computer.

[0057] Figure 6 The structure diagram of the signal conditioning circuit according to the embodiment of the present disclosure is schematically shown.

[0058] like Figure 6 As shown, each signal conditioning circuit conditions the resistance value output by the corresponding strain sensing unit to obtain a corresponding voltage signal. The signal conditioning circuit includes an amplifier 604, a feedback unit and a voltage stabilizing capacitor 603; the feedback unit includes a feedback resistor 602 and a feedback capacitor 601; the feedback capacitor 601 and the feedback resistor 602 are connected in parallel; the reverse input end of the amplifier 604 is connected to the output end of the amplifier 604 through the feedback unit; the reverse input end of the amplifier 604 is also connected to the other end of the output channel of the corresponding strain sensing unit; the other end of the common ground line of the corresponding strain sensing unit is connected to the ground line; that is, the strain sensing unit is connected to the amplifier as an equivalent resistor 605. The reverse input terminal of the amplifier 604, one end of the equivalent resistor 605 is connected to the reverse input terminal of the amplifier 604, and the other end of the equivalent resistor 605 is connected to the ground; the positive input terminal of the amplifier 604 is connected to the preset voltage signal; the preset voltage signal is 1.2V, and the output terminal of the amplifier 604 is connected to the analog-to-digital conversion unit; the power supply voltage input terminal of the discharger is connected to the preset power supply voltage signal, the preset power supply voltage signal is 5V voltage, and the power supply voltage input terminal of the discharger is also connected to one end of the voltage stabilizing capacitor 603; the other end of the voltage stabilizing capacitor 603 is connected to the ground. Among them, the capacitance of the voltage stabilizing capacitor 603 can be selected as 100nf, the capacitance of the feedback capacitor 601 can be selected as 100nf, and the resistance of the feedback resistor 602 can be selected as 20K; the parameters of the amplifier 604, the voltage stabilizing capacitor 603, the feedback resistor 602 and the feedback capacitor 601 can be selected according to actual conditions, and are not limited here.

[0059] Figure 7 A flow chart of a shape perception method according to another embodiment of the present disclosure is schematically shown.

[0060] like Figure 7As shown, the method includes operations S701 to S703.

[0061] In operation S701 , a kinematic model of the flexible robot end is constructed.

[0062] In operation S702 , a resistance value array output by a flexible strain sensor array in a shape sensing system is obtained.

[0063] In operation S703, the resistance value array is input into a kinematic model to obtain deformation parameters of the end of the flexible robot; the deformation parameters include a bending angle and a bending direction.

[0064] According to an embodiment of the present disclosure, a process of constructing a kinematic model of a flexible robot includes: when the end of the flexible robot is not deformed, the surface perpendicular to the end of the flexible robot is taken as the XY plane, the X-axis and the Y-axis are set on the XY plane, and a three-dimensional coordinate system is constructed with the center axis of the end of the flexible robot as the Z-axis; when the end of the flexible robot is deformed, based on the three-dimensional coordinate system, a first geometric relationship between the bending angle of the end of the flexible robot and the deformation amount and a second geometric relationship between the bending direction of the end of the flexible robot and the deformation amount are determined.

[0065] The resistance value array output by the flexible strain sensor array corresponding to the preset deformation amount of the end of the flexible robot is obtained to obtain an initial data set; based on the initial data set, the mathematical relationship between the deformation amount of the end of the flexible robot and the resistance value array output by the flexible strain sensor array is determined; based on the mathematical relationship, the first geometric relationship and the second geometric relationship, the first corresponding relationship between the bending angle and the resistance value array and the second corresponding relationship between the bending direction and the resistance value array are determined, and the first corresponding relationship and the second corresponding relationship are used as the kinematic model of the end of the flexible robot.

[0066] Figure 8 A kinematic modeling reference diagram according to an embodiment of the present disclosure is schematically shown. Figure 8 (a) is a schematic diagram of the principle of a single flexible strain sensing unit when the flexible robot is bent. Figure 8 (b) is a top view of three flexible strain sensing units in the same row of the flexible strain sensor array when the flexible robot is bent. Figure 8 (c) is a schematic diagram of the principle of the flexible strain sensor array when the flexible robot is bent.

[0067] like Figure 8 As shown in (a), the geometric relationship before and after bending deformation and the relative change of resistance are shown in Equations (1) to (5).

[0068] Taking the shape of the flexible robot end as a cylindrical shape as an example, a 3×3 flexible strain sensor array is designed corresponding to the cylindrical size, and the 3×3 flexible strain sensor array is wrapped around the cylindrical flexible robot end. Each row of the flexible strain sensor array is evenly distributed at the cylindrical flexible robot end. When the flexible robot end is not deformed, the original length L of the flexible sensor unit is equal to the neutral axis length K of the flexible robot end corresponding to the flexible sensor unit; when the flexible robot end is deformed, the neutral axis length of the flexible robot remains unchanged. At this time, k is used to represent the neutral axis length of the flexible robot when the flexible robot end is deformed. The corresponding bending angle of the flexible robot end is θ, and the corresponding curvature radius is r. Then k is the product of the curvature radius and the bending angle of the flexible robot end, and formula (1) is obtained.

[0069] (1)

[0070] When the end of the flexible robot is deformed, the radius of curvature r is added to the radius of the cross section of the cylindrical flexible robot end as the new radius of curvature. The product of the new radius of curvature and the bending angle θ of the flexible robot end is used to obtain the length of the flexible sensing unit after bending. , and we get formula (2).

[0071] (2)

[0072] Then, the length of the flexible sensing unit after bending is The difference between the original length L of the flexible sensing unit without deformation at the end of the flexible robot is equal to the strain ε of the flexible sensing unit. When the strain ε of the flexible sensing unit is within the linear variation range of the strain sensing unit, the strain ε of the flexible sensing unit and the relative change of the resistance of the flexible sensing unit are There is a linear relationship between them. According to formula (1) and formula (2), we get formula (3).

[0073] (3)

[0074] Thus, the bending angle θ of the flexible robot end and the relative change of the resistance of the flexible sensing unit can be deduced. The relationship between and obtains formula (4), and the length of the flexible sensing unit after bending Relative change in resistance of the flexible sensing unit The relationship between , we get formula (5).

[0075] (4)

[0076] (5)

[0077] Formula (1)-Formula (5) is based on a flexible strain sensing unit as an example. Figure 8 As shown in (a), (b) and (c), the following takes the three flexible strain sensing units in each row of the flexible strain sensor array as an example to illustrate the relationship between the bending direction and the relative change of resistance, as shown in equations (6) to (14).

[0078] The flexible sensing unit in the xy plane includes sensor 1, sensor 2 and sensor 3. When the end of the flexible robot is not deformed, the central axis of the end of the cylindrical flexible robot is Figure 8 The r-axis direction shown in (b) is the angle between the r-axis direction and the y-axis. , the angle between sensor 1 and the r axis is , the angle between sensor 2 and the r axis is , the angle between sensor 3 and r axis is .

[0079] like Figure 8 As shown in (a), when the end of the cylindrical flexible robot is deformed, the curvature radius corresponding to sensor 1 is r1, the curvature radius corresponding to sensor 2 is r2, and the curvature radius corresponding to sensor 3 is r3. is the length of the flexible sensing unit sensor i after bending, and formula (6) can be obtained. Where, and The values ​​of i are 1, 2 and 3, and the values ​​of i correspond to sensor 1, sensor 2 and sensor 3.

[0080] (6)

[0081] Since the length of the arc is equal to the product of the angle θ corresponding to the arc and the corresponding radius of curvature, that is, , according to formula (6), we can get formula (7).

[0082] (7)

[0083] According to formula (7), formula (8) and formula (9) can be derived.

[0084] (8)

[0085] (9)

[0086] The angle θ can be obtained according to formula (8), and the angle θ can also be obtained according to formula (9), thereby formula (10) can be derived.

[0087] (10)

[0088] Since sensor 1, sensor 2 and sensor 3 are evenly distributed on the outer surface of the cylindrical flexible robot end, the angle between sensor 1, sensor 2 and sensor 3 is 120 degrees. According to formula (10), formula (11) is derived.

[0089] (11)

[0090] Divide formula (11) by After the formula transformation, we get formula (12).

[0091] According to formula (12), formula (13) is obtained. Formula (13) is the first geometric relationship.

[0092] (12)

[0093] (13)

[0094] According to formula (5), the length of the flexible sensing unit after bending is Relative change in resistance of the flexible sensing unit There is a linear relationship between , and , according to formula (13), we get formula (14). Formula (14) is the first corresponding relationship.

[0095] 14)

[0096] in, , is the relative change in resistance of the flexible sensing unit sensor 1, is the relative change in resistance of the flexible sensing unit sensor 2, is the relative change in resistance of the flexible sensing unit sensor 3.

[0097] like Figure 8 As shown in (a), (b) and (c), the following takes the three flexible strain sensing units in each row of the flexible strain sensor array as an example to illustrate the relative change relationship between the bending angle and the resistance, as shown in equations (15) to (19).

[0098] According to formula (7), formula (15) and formula (16) can be derived.

[0099] (15)

[0100] (16)

[0101] Due to the positional relationship among sensor 1, sensor 2 and sensor 3, , ,so , and we get formula (17).

[0102] (17)

[0103] Formula (18) is obtained according to formula (17) and formula (15). Formula (18) is the second geometric relationship.

[0104] (18)

[0105] According to formula (5), the length of the flexible sensing unit after bending is Relative change in resistance of the flexible sensing unit There is a linear relationship between , and , according to formula (18), we get formula (19). Formula (19) is the second corresponding relationship.

[0106] (19)

[0107] Wherein, L is the original length of the flexible sensing unit, is the length of the flexible sensing unit after bending, K is the neutral axis length of the flexible robot end corresponding to the flexible sensing unit, θ is the bending angle of the flexible robot end, D is the diameter of the cylindrical flexible robot end, ε is the strain of the flexible sensing unit, is the angle between the flexible sensing unit and the y-axis in the xy plane.

[0108] According to formula (14) and formula (19), the kinematic equation of the flexible robot end can be obtained.

[0109] When the strain ε of the flexible sensing unit is within the linear variation range of the strain sensing unit, the strain ε of the flexible sensing unit and the relative variation of the resistance of the flexible sensing unit are There is no linear relationship between them, so the above formula cannot be used for calculation. In this case, a neural network model is used to predict the length of the flexible sensor unit after bending. Relative change in resistance of the flexible sensing unit The relationship between.

[0110] According to an embodiment of the present disclosure, the neural model may adopt an LSTM (Long Short-Term Memory) model. The resistance value array output by the corresponding flexible strain sensor array when a preset deformation occurs at the end of the flexible robot is obtained to obtain an initial data set; based on the initial data set, the LSTM model is trained so that the trained LSTM model learns the mathematical relationship between the deformation of the end of the flexible robot and the resistance value array output by the flexible strain sensor array. When the model is actually applied, the deformation of the corresponding flexible robot end can be output by the trained LSTM model through the resistance value array output by the detected flexible strain sensor array. Then, the deformation parameters can be determined according to formula (13) and formula (18).

[0111] Taking the three flexible strain sensing units in each row of the flexible strain sensor array as an example, after obtaining the deformation parameters of each row, the deformation state of the central axis of the flexible robot end corresponding to each row of flexible strain sensing units can be obtained. By splicing the deformation states of each row, the overall deformation state of the central axis of the flexible robot end can be obtained. Figure 8 (c) shows the deformation state of the central axis of the flexible robot end corresponding to three flexible strain sensing units in a row. If the flexible strain sensor array is three rows, there are three segments such as Figure 8 (c) shows the deformation state. According to the positions of the three flexible strain sensing units in the three rows of the flexible strain sensor array, it is determined that there are three segments such as Figure 8 (c) shows the positional relationship of the deformation states, thereby splicing together to obtain the overall deformation state of the central axis of the flexible robot end.

[0112] The flowcharts and block diagrams in the accompanying drawings illustrate the possible implementation architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each box in the flowchart or block diagram may represent a module, a program segment, or a part of a code, and the above-mentioned module, program segment, or a part of the code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box may also occur in an order different from that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flowchart, and the combination of boxes in the block diagram or flowchart, can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions. It can be understood by those skilled in the art that the features recorded in the various embodiments of the present disclosure can be combined and / or combined in a variety of ways, even if such a combination or combination is not explicitly recorded in the present disclosure. In particular, without departing from the spirit and teaching of the present disclosure, the features described in the various embodiments of the present disclosure may be combined and / or combined in a variety of ways. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0113] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A flexible strain sensor array, characterized in that: include: A flexible base layer; The strain layer includes a common ground circuit, a plurality of output channels and a plurality of strain sensing units arranged in an array formed on the flexible substrate layer; Each of the strain sensing units corresponds to an output channel; each of the strain sensing units includes a first conductive pattern and a second conductive pattern arranged in the first conductive pattern; one end of the first conductive pattern is connected to one end of the common ground circuit; the other end of the first conductive pattern is connected to one end of the corresponding output channel; One end of the second conductive pattern is connected to one end of the common ground circuit; the other end of the second conductive pattern is connected to one end of the corresponding output channel; as well as an encapsulation layer, covering the strain layer on the base layer; The other end of the common ground circuit and the other end of the output channel corresponding to each of the strain sensing units serve as output ends of the flexible strain sensor array.

2. The flexible strain sensor array according to claim 1, characterized in that: The first conductive pattern is in a rectangular shape; the first conductive pattern includes a first line segment, a second line segment, a third line segment and a fourth line segment; one end of the first line segment is connected to one end of the second line segment by a chamfer; the other end of the second line segment is connected to one end of the third line segment by a chamfer; the other end of the third line segment is connected to one end of the fourth line segment by a chamfer; the other end of the fourth line segment is connected to the other end of the first line segment by a chamfer; The second conductive pattern is in a U-shaped shape; One end of the second conductive pattern is connected to the first line segment; The other end of the second conductive pattern is connected to the third line segment.

3. The flexible strain sensor array according to claim 1, characterized in that: The material of the flexible base layer is thermoplastic polyurethane elastomer rubber.

4. The flexible strain sensor array according to claim 1, characterized in that: The materials of the first conductive pattern and the second conductive pattern include polydimethylsiloxane and multi-walled carbon nanotubes.

5. The flexible strain sensor array according to claim 1, characterized in that: The material of the encapsulation layer is polydimethylsiloxane.

6. A shape perception system, characterized in that: It comprises a signal conditioning module, a shape sensing module and the flexible strain sensor array according to any one of claims 1 to 5; The flexible strain sensor array is arranged at the end of the flexible robot; the flexible strain sensor array is used to output a resistance value array corresponding to the deformation of the end of the flexible robot; The signal conditioning module is connected to the flexible strain sensor array; the signal conditioning module is used to convert the resistance value array into a digital deformation signal; The shape sensing module is connected to the signal conditioning module; the deformation sensing module is used to construct a kinematic model of the flexible robot end, and input the digital deformation signal into the kinematic model to determine the deformation parameters of the flexible robot end; the deformation parameters include bending angle and bending direction.

7. The shape sensing system according to claim 6, characterized in that: The signal conditioning module includes an analog-to-digital conversion unit and a multi-channel signal conditioning circuit; Each of the signal conditioning circuits corresponds to a strain sensing unit of the flexible strain sensor array; The signal conditioning circuit includes an amplifier and a feedback unit; the feedback unit includes a feedback resistor and a feedback capacitor; the feedback capacitor and the feedback resistor are connected in parallel; The reverse input end of the amplifier is connected to the output end of the amplifier through the feedback unit; the reverse input end of the amplifier is also connected to the other end of the output channel of the corresponding strain sensing unit; the other end of the ground supply line of the corresponding strain sensing unit is connected to the ground wire; The positive input terminal of the amplifier is connected to a preset voltage signal; The output end of the amplifier is connected to the analog-to-digital conversion unit; the analog-to-digital conversion unit is used to convert the analog voltage signal output by the output end of the amplifier into a digital deformation signal; The analog-to-digital conversion unit is connected to the deformation sensing module.

8. The shape sensing system according to claim 6, characterized in that: It also includes a flexible circuit; one end of the flexible circuit is connected to the output end of the flexible strain sensor array; and the other end of the flexible circuit is connected to the signal conditioning module.

9. A shape perception method, characterized in that: The method comprises: Construct the kinematic model of the flexible robot end; Obtaining a resistance value array output by a flexible strain sensor array in a shape sensing system according to any one of claims 6 to 8; The resistance value array is input into the kinematic model to obtain the deformation parameters of the end of the flexible robot; the deformation parameters include a bending angle and a bending direction.

10. The shape perception method according to claim 9, characterized in that: The process of constructing the kinematic model of the flexible robot includes: When the end of the flexible robot is not deformed, the plane perpendicular to the end of the flexible robot is taken as the XY plane, the X axis and the Y axis are set on the XY plane, and the central axis of the end of the flexible robot is taken as the Z axis to construct a three-dimensional coordinate system; When the end of the flexible robot is deformed, determining, based on the three-dimensional coordinate system, a first geometric relationship between a bending angle of the end of the flexible robot and the deformation amount and a second geometric relationship between a bending direction of the end of the flexible robot and the deformation amount; Obtaining an array of resistance values ​​output by the flexible strain sensor array corresponding to when a preset deformation occurs at the end of the flexible robot, to obtain an initial data set; Determining, based on the initial data set, a mathematical relationship between the deformation amount of the end of the flexible robot and the resistance value array output by the flexible strain sensor array; According to the mathematical relationship, the first geometric relationship and the second geometric relationship, a first corresponding relationship between the bending angle and the resistance value array and a second corresponding relationship between the bending direction and the resistance value array are determined, and the first corresponding relationship and the second corresponding relationship are used as the kinematic model of the flexible robot end.

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