A thin film pressure sensor for a wheelless snake-like robot and its preparation and calibration method

Abstract

A thin film pressure sensor for use in a wheelless snake-like robot and a method for preparing and calibrating the same belong to the field of robotics. The present invention aims to solve the problems existing in existing thin film pressure sensors used in wheelless snake-like robots. The thin film pressure sensor of the present invention comprises a connection substrate, a first connection layer, a first insulating layer, a first electrode layer, a piezoresistive sensitive layer, a second electrode layer, a second insulating layer, a second connection layer and a wear-resistant and anti-skid protective layer, which are arranged in sequence from bottom to top; each layer is made of a thin film flexible material, and each layer is custom-cut and pasted according to the surface shape of the wheelless snake-like robot joint module by a lamination method; the wear-resistant and anti-skid protective layer is made of nitrile rubber and serves as a protective skin. The thin film pressure sensor of the present invention can be directly installed on the surface of a wheelless snake-like robot as a pressure-sensing skin, and the thin film pressure sensors installed at different positions can be directly calibrated by the provided calibration method.

Description

Technical Field

[0001] The invention relates to a thin film pressure sensor suitable for the surface of a wheelless snake-shaped robot and a preparation and calibration method thereof, belonging to the technical field of robots. Background Art

[0002] Thin-film pressure sensors are often used on mobile robots for pressure detection due to their light weight and small size. However, for wheelless snake-like robots with multiple bionic joints and redundant degrees of freedom, current thin-film pressure sensors struggle to fully realize their surface pressure sensing capabilities.

[0003] On the one hand, wheelless snake-like robots have multiple joint modules, requiring a large number of thin-film pressure sensors with shapes and dimensions that match the joint module surfaces. This requires that the thin-film pressure sensors be custom-made in large quantities based on the robot's surface shape. On the other hand, wheelless snake-like robots rely on friction between their body surface and the ground to navigate complex environments, such as narrow and irregular shapes. The robot's surface requires both pressure sensing and a high coefficient of friction with the ground or objects. Currently, researchers mostly install the thin-film pressure sensors inside the robot structure or install them on the robot surface and then cover the wheelless snake-like robot with a skin to protect the thin-film pressure sensors. Both methods isolate the thin-film pressure sensors from external objects, affecting the accuracy of pressure sensing. The internal installation method also increases the robot's size, affecting the snake-like robot's agility.

[0004] Existing customizable thin-film pressure sensors suffer from insufficient durability when used in wheelless snake-like robots. This is especially true when the robot is moving across diverse terrains and environments. Repeated collisions and impacts can damage the sensor or degrade its performance. Furthermore, existing thin-film pressure sensors fail to adequately consider surface friction, making them inefficient for the creeping and crawling movements of wheelless snake-like robots.

[0005] The existing pressure sensor calibration process basically adopts a top-down pressure loading method, which requires ensuring that the pressure-bearing surface of the sensor is parallel to the fixed base. However, the surface of the thin film pressure sensor installed on the wheelless snake-like robot is not necessarily parallel to the fixed base surface, so the fixed base in the calibration device needs to be customized, which increases the complexity of the calibration. Summary of the Invention

[0006] To address the challenges of existing thin-film pressure sensors used in wheelless snake-like robots, the present invention provides a robot thin-film pressure sensor and its preparation and calibration methods. The thin-film pressure sensor can be directly mounted on the surface of the wheelless snake-like robot as a pressure-sensing skin. The provided calibration method allows for direct calibration of thin-film pressure sensors installed at different locations.

[0007] In one aspect, the present invention provides a thin film pressure sensor for a wheelless snake-like robot. The thin film pressure sensor 1 comprises, arranged from bottom to top, a connection base 1-1, a first connection layer 1-2, a first insulating layer 1-3, a first electrode layer 1-4, a piezoresistive sensitive layer 1-5, a second electrode layer 1-6, a second insulating layer 1-7, a second connection layer 1-8, and a wear-resistant and anti-slip protective layer 1-9. Each layer is made of a thin film flexible material and is custom-cut and bonded according to the surface shape of the wheelless snake-like robot's joint module through a lamination process.

[0008] The wear-resistant and anti-skid protective layer 1-9 is made of nitrile rubber and serves as skin protection.

[0009] Preferably, the connecting matrix 1-1 is made of polylactic acid PLA material;

[0010] The piezoresistive sensitive layers 1-5 are made of Velostat polymer material;

[0011] The first insulating layer 1-3 and the second insulating layer 1-7 are made of polyester single-sided tape, and the backing material is polyester film;

[0012] The first electrode layer 1-4 and the second electrode layer 1-6 are made of copper foil;

[0013] The first connecting layer 1-2 and the second connecting layer 1-8 are made of polyacrylate double-sided tape.

[0014] Another aspect of the present invention provides a method for preparing a thin film pressure sensor for use with a wheelless snake-like robot. The method is a method for preparing the thin film pressure sensor for use with a wheelless snake-like robot, and the method comprises the following steps:

[0015] Step A1: obtaining the design dimensions of the thin film pressure sensor 1 according to the surface shape of the joint module of the wheelless snake-like robot;

[0016] Step A2: Cutting the wear-resistant and anti-slip protective layer 1-9, the first connecting layer 1-2, the second connecting layer 1-8, the first insulating layer 1-3, the second insulating layer 1-7, and the piezoresistive sensitive layer 1-5 to the same size as the thin film pressure sensor 1;

[0017] Step A3: Cut the copper foil of the first electrode layer 1-4 and the second electrode layer 1-6 so that the length and width are shorter than the design size of the thin film pressure sensor 1 by a distance d, and an extra protruding portion is left at one of the corners;

[0018] Step A4: Fix the two signal lines to the protruding portions of the first electrode layer 1 - 4 and the second electrode layer 1 - 6 respectively by welding;

[0019] Step A5: utilizing the adhesion of the first insulating layer 1-3, fixing the first insulating layer 1-3 to the first electrode layer 1-4 and the piezoresistive sensitive layer 1-5 in sequence;

[0020] Using the adhesive property of the second insulating layer 1-7, the second insulating layer 1-7 is fixed to the second electrode layer 1-6 and the other surface of the piezoresistive sensitive layer 1-5 in sequence;

[0021] Step A6: Using the double-sided adhesive property of the second connecting layer 1-8, fix the wear-resistant and anti-slip protective layer 1-9 to the second insulating layer 1-7;

[0022] Step A7: Using the double-sided adhesive property of the first connection layer 1-2, the first insulating layer 1-3 is fixed on the connection base 1-1.

[0023] Preferably, the four sides of the first electrode layer 1-4 in the middle layer are retracted by a distance d / 2 from the outer edges of the first insulating layer 1-3 and the piezoresistive sensitive layer 1-5; the edge area of ​​the first insulating layer 1-3 is bonded to the edge area of ​​the piezoresistive sensitive layer 1-5, and the other areas of the first insulating layer 1-3 are bonded to the first electrode layer 1-4;

[0024] The four sides of the second electrode layer 1-6 in the middle layer are retracted by a distance d / 2 compared to the outer edges of the second electrode layer 1-6 and the piezoresistive sensitive layer 1-5; the edge area of ​​the second insulating layer 1-7 is bonded to the edge area of ​​the piezoresistive sensitive layer 1-5, and the other areas of the second insulating layer 1-7 are bonded to the second electrode layer 1-6.

[0025] A third aspect of the present invention provides a calibration method for a thin film pressure sensor used in a wheelless snake-like robot. The method calibrates the thin film pressure sensor used in the wheelless snake-like robot. The calibration method comprises the following steps:

[0026] Step B1: Install thin film pressure sensors 1 of corresponding sizes on all joints of the wheelless snake-like robot, with a total of 1 to N thin film pressure sensors 1 installed on each side of each joint;

[0027] Step B2: Fix all joints on the test platform in turn, calibrate the thin film pressure sensors 1 on different sides of each joint, and calibrate the thin film pressure sensors 1 of the next joint after calibrating all the thin film pressure sensors 1 of one joint. The process of calibrating any thin film pressure sensor 1 is as follows:

[0028] Step B21: using the six-degree-of-freedom robotic arm 4 to drive the pressure-loading actuator 2 to apply M sets of pressure values ​​to the thin film pressure sensor 1, with the direction of the applied force being perpendicular to the surface of the thin film pressure sensor 1;

[0029] Step B22: The pressure value applied by the pressure-loading actuator 2 is collected by the six-dimensional force sensor 3 and sent to the computer 6; the single-chip microcontroller MCU5 synchronously collects the conductivity data of the thin film pressure sensor 1; a total of M groups of pressure-conductance matching data are obtained as calibration data of the thin film pressure sensor 1 and stored in the computer 6.

[0030] Preferably, the six-dimensional force sensor 3 is installed between the end of the six-degree-of-freedom robotic arm 4 and the pressure loading actuator 2 .

[0031] Preferably, the process of the single-chip microcontroller MCU5 synchronously collecting the conductivity data of the thin film pressure sensor 1 is:

[0032] Step C1: Two signal lines of the thin film pressure sensor 1 are connected to the thin film pressure sensor data acquisition circuit. Specifically, one signal line of the thin film pressure sensor 1 is connected to a constant voltage DC power supply VCC, and the other signal line of the thin film pressure sensor 1 is connected to one end of a fixed resistor R1 and an input end of a single-chip microcontroller MCU5. The other end of the fixed resistor R1 is grounded. The single-chip microcontroller MCU5 has a built-in analog-to-digital conversion module.

[0033] Step C2: Connect the fixed resistor R1 in series with the resistance value R of the thin film pressure sensor to be calibrated. v The voltage V output from the common node adc Collected by the single-chip microcontroller MCU5;

[0034] Step C3: The single-chip microcontroller MCU5 processes the collected voltage V adc After the analog-to-digital conversion, the conductivity value of the thin film pressure sensor to be calibrated is obtained according to the following formula, and the data is sent to the computer 6:

[0035]

[0036] Where V full is the theoretical maximum value, V full The size is determined by the resolution of the analog-to-digital conversion module of the single-chip microcontroller MCU5.

[0037] Beneficial effects of the present invention:

[0038] 1. The thin film pressure sensor of the present invention can be directly installed on the surface of a wheelless snake-like robot as a sensing skin. The structure from bottom to top is a connecting base, a first connecting layer, a first insulating layer, a first electrode layer, a piezoresistive sensitive layer, a second electrode layer, a second insulating layer, a second connecting layer, and a wear-resistant and anti-slip protective layer. The connecting base is a robot. Except for the connecting base, each layer is made of a thin film flexible material. The layers are prepared by custom cutting and laminating by a lamination method. The wear-resistant and anti-slip protective layer acts as a protective skin to ensure that the thin film pressure sensor can still operate normally when it is impacted or scratched during use. The large friction coefficient of its surface can improve the efficiency of the wheelless snake-like robot's creeping movement. The piezoresistive sensitive layer uses a Velostat polymer material with a large piezoresistive coefficient and high linearity. The thin film pressure sensor prepared by the above structure and method has the characteristics of high linearity, surface wear resistance, customizable shape and simple preparation. After being prepared according to the surface shape of the wheelless snake-like robot joint module, it can be directly installed on the robot surface as a sensing skin to realize the pressure sensing function during the creeping movement of the wheelless snake-like robot.

[0039] 2. The calibration method provided by this invention improves upon previous process steps. It utilizes a combination of a six-dimensional force sensor and a robotic arm to perform calibration by applying precise force to a thin-film pressure sensor, with the MCU synchronously reading the sensor's output data. After securing the wheelless snake-like robot, this calibration method can directly calibrate thin-film pressure sensors installed in different locations without requiring further readjustment. This ensures consistency in calibration data across multiple sensors and improves calibration efficiency, significantly reducing the development cycle for surface pressure sensing in wheelless snake-like robots. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings are part of this application and are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention but do not constitute improper limitations on the present invention.

[0041] Figure 1 A schematic diagram of the structural hierarchy of a thin film pressure sensor provided by an embodiment of the present invention;

[0042] Figure 2 A schematic diagram of another structural hierarchy of a thin film pressure sensor provided by an embodiment of the present invention;

[0043] Figure 3 A schematic diagram of a thin film pressure sensor calibration device provided in an embodiment of the present invention;

[0044] Figure 4A measurement circuit diagram for collecting thin film pressure sensor data provided by an embodiment of the present invention;

[0045] Explanation of the accompanying figures: 1-thin film pressure sensor; 1-1-connecting substrate; 1-2-first connecting layer; 1-3-first insulating layer; 1-4-first electrode layer; 1-5-piezoresistive sensitive layer; 1-6-second electrode layer; 1-7-second insulating layer; 1-8-second connecting layer; 1-9-wear-resistant and anti-slip protective layer; 2-pressure loading actuator; 3-six-dimensional force sensor; 4-six-degree-of-freedom robotic arm; 5-MCU; 6-laptop computer. DETAILED DESCRIPTION

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0047] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0048] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0049] Specific implementation method 1: Figure 1 and Figure 2 This embodiment describes a thin film pressure sensor for a wheelless snake-like robot. The thin film pressure sensor 1 includes, arranged from bottom to top, a connection base 1-1, a first connection layer 1-2, a first insulating layer 1-3, a first electrode layer 1-4, a piezoresistive sensitive layer 1-5, a second electrode layer 1-6, a second insulating layer 1-7, a second connection layer 1-8, and a wear-resistant and anti-slip protective layer 1-9. Each layer is made of a thin film flexible material and is custom-cut and pasted according to the surface shape of the wheelless snake-like robot joint module through a lamination method.

[0050] The wear-resistant and anti-skid protective layer 1-9 is made of nitrile rubber and serves as a protective skin. Preferred embodiment: The thickness is 1mm, which is used to prevent the sensor from being worn, so that when the sensor is installed on the surface of the robot, it provides greater friction between the robot and the ground, and can be used normally in harsh working environments. The present invention uses nitrile rubber as a protective skin to ensure that the thin film pressure sensor can still maintain normal operation when it is impacted or scratched during use. The larger friction coefficient of its surface can improve the efficiency of the wheelless snake-like robot in creeping movement. In addition to being a part of the thin film pressure sensor 1, the wear-resistant and anti-skid protective layer 1-9 of the present invention also serves as a protective skin. After the thin film pressure sensor 1 is installed at the joint of the wheelless snake-like robot, there is no need to install a separate electronic skin. This not only simplifies the process steps, but also reduces costs, and makes subsequent maintenance and replacement of parts more convenient.

[0051] The connecting matrix 1-1 is made of polylactic acid (PLA) material, and its shape is formed by 3D printing according to the robot structure. PLA is the abbreviation of Poly lactic acid.

[0052] The first connecting layer 1-2 and the second connecting layer 1-8 are made of polyacrylate double-sided tape; preferred embodiment: the material model is 3M4905VHB, the thickness is 0.5mm, the first connecting layer 1-2 plays the role of fixing the sensor on the robot base, and the second connecting layer 1-8 plays the role of fixing the wear-resistant and anti-slip protective layer 1-9.

[0053] The first insulating layer 1-3 and the second insulating layer 1-7 are made of polyester single-sided tape, with a polyester film backing material. In a preferred embodiment, the material used is 3M56, with a thickness of 0.064 mm. The first insulating layer 1-3 is connected to the first electrode layer 1-4 and the piezoresistive sensitive layer 1-5, respectively. The second insulating layer 1-7 is connected to the second electrode layer 1-6 and the piezoresistive sensitive layer 1-5, respectively, providing insulation, packaging, and structural fixation.

[0054] The first electrode layer 1-4 and the second electrode layer 1-6 are made of copper foil; in a preferred embodiment, the thickness is 0.066 mm, and the piezoresistive sensitive layer 1-5 is sandwiched in the middle to play a role in signal transmission.

[0055] The piezoresistive sensitive layers 1-5 are made of Velostat polymer material; in a preferred embodiment, they have a thickness of 0.1 mm, exhibit excellent piezoresistive effect, a low temperature coefficient of resistance, are stretchable, and can be tailored to various shapes and sizes according to different application requirements. The piezoresistive sensitive layers 1-5 are made of Velostat polymer material with a high piezoresistive coefficient and high linearity. The resulting thin-film pressure sensor exhibits high linearity, a wear-resistant surface, customizable shapes, and ease of fabrication. After being fabricated to the surface shape of a wheelless snake robot's joint module, it can be directly mounted on the robot's surface as a sensing skin, enabling pressure sensing during the robot's peristaltic motion.

[0056] Specific implementation method 2: The following is combined Figure 1 and Figure 2 This embodiment describes a method for preparing a thin film pressure sensor for a wheelless snake-like robot. This method is a method for preparing a thin film pressure sensor for a wheelless snake-like robot described in Embodiment 1. The method comprises the following steps:

[0057] Step A1: obtaining the design dimensions of the thin film pressure sensor 1 according to the surface shape of the joint module of the wheelless snake-like robot;

[0058] Step A2: Cutting the wear-resistant and anti-slip protective layer 1-9, the first connecting layer 1-2, the second connecting layer 1-8, the first insulating layer 1-3, the second insulating layer 1-7, and the piezoresistive sensitive layer 1-5 to the same size as the thin film pressure sensor 1;

[0059] Step A3: Cut the copper foil of the first electrode layer 1-4 and the second electrode layer 1-6 so that the length and width are shorter than the design size of the thin film pressure sensor 1 by a distance d, and an extra protruding portion is left at one of the corners;

[0060] Step A4: Fix the two signal lines to the protruding portions of the first electrode layer 1-4 and the second electrode layer 1-6 respectively by welding;

[0061] Step A5: Utilizing the adhesive properties of the first insulating layer 1-3, the first insulating layer 1-3 is fixed to the first electrode layer 1-4 and the piezoresistive sensitive layer 1-5 in sequence; the four sides of the first electrode layer 1-4 in the middle layer are retracted inward by a distance d / 2 relative to the outer edges of the first insulating layer 1-3 and the piezoresistive sensitive layer 1-5; the edge region of the first insulating layer 1-3 is bonded to the edge region of the piezoresistive sensitive layer 1-5, and the remaining region of the first insulating layer 1-3 is bonded to the first electrode layer 1-4;

[0062] Utilizing the adhesion of the second insulating layer 1-7, the second insulating layer 1-7 is fixed to the other side of the second electrode layer 1-6 and the piezoresistive sensitive layer 1-5 in sequence; the four sides of the second electrode layer 1-6 in the middle layer are retracted by a distance d / 2 compared to the outer edges of the second electrode layer 1-6 and the piezoresistive sensitive layer 1-5; the edge area of ​​the second insulating layer 1-7 is bonded to the edge area of ​​the piezoresistive sensitive layer 1-5, and the other areas of the second insulating layer 1-7 are bonded to the second electrode layer 1-6.

[0063] Step A6: Using the double-sided adhesive property of the second connecting layer 1-8, fix the wear-resistant and anti-slip protective layer 1-9 to the second insulating layer 1-7;

[0064] Step A7: Using the double-sided adhesive property of the first connection layer 1-2, the second insulating layer 1-7 is fixed on the connection base 1-1.

[0065] The following is an example of a preparation method:

[0066] Step A1: Obtain the design dimensions of the thin film pressure sensor 1 according to the surface shape of the joint module of the wheelless snake-like robot; the wheelless snake-like robot has 16 joints, of which three thin film pressure sensors 1 need to be installed on the three sides of joint No. 1, with dimensions of 4×4cm, 4×6cm, and 4×3cm respectively. The number of sides and the dimensions of the thin film pressure sensors 1 installed in other joints are different and are determined according to actual conditions.

[0067] Step A2: Cut materials of equal size according to the design size of the required sensor. Cut the nitrile rubber into wear-resistant and anti-slip protective layers 1-9, cut the 3M4905VHB into the first connecting layer 1-2 and the second connecting layer 1-8, cut the 3M56 into the first insulating layer 1-3 and the second insulating layer 1-7, and cut the Velostat into the piezoresistive sensitive layer 1-5.

[0068] Step A3: Cut the copper foil into the first electrode layers 1-4 and the second electrode layers 1-6. Compared to the design dimensions of the thin-film pressure sensor 1, the length and width are shortened by a distance d = 4-10 mm. This means that each edge is retracted by d / 2 = 2-5 mm, and an additional portion is left protruding at one corner. This retraction is to allow for the bonding of the first insulating layers 1-3 and the second insulating layers 1-7 to the piezoresistive sensing layer 1-5, respectively. The additional portion is left protruding at the corner to facilitate wire soldering and lead out the signal transmission interface.

[0069] Step A4: Solder the two signal wires to the protruding portions of the first electrode layer 1 - 4 and the second electrode layer 1 - 6 respectively, to mechanically and electrically fix the signal wires to the sensor.

[0070] Step A5: Utilizing the adhesive properties of the first insulating layer 1-3, the adhesive surface of the first insulating layer 1-3 is sequentially fixed to the first electrode layer 1-4 and the piezoresistive sensitive layer 1-5. Utilizing the adhesive properties of the second insulating layer 1-7, the adhesive surface of the second insulating layer 1-7 is sequentially fixed to the second electrode layer 1-6 and the other surface of the piezoresistive sensitive layer 1-5. The edge of the surface of the insulating layer is in contact and adhered to the edge of the surface of the piezoresistive sensitive layer 1-5, and the interior of the surface of the insulating layer is in contact and adhered to the electrode layer.

[0071] Step A6: Using the double-sided adhesive property of the second connecting layer 1-8, fix the wear-resistant and anti-slip protective layer 1-9 to the second insulating layer 1-7;

[0072] Step A7: Using the double-sided adhesive property of the first connection layer 1-2, the first insulating layer 1-3 is fixed on the connection base 1-1, thereby fixing the thin film pressure sensor on the surface of the robot.

[0073] Specific implementation method three: Figure 3 and Figure 4 This embodiment will be described. A calibration method for a thin film pressure sensor applied to a wheelless snake-like robot described in this embodiment is used to calibrate the thin film pressure sensor applied to a wheelless snake-like robot described in the first embodiment.

[0074] The calibration device used in the calibration method of this embodiment is shown in FIG. Figure 3 As shown, it includes a set of pressure loading equipment that can stably output pressure, and a set of measuring equipment that can collect information of the thin film pressure sensor in real time, and the time between the two devices is synchronized; a joint with a thin film pressure sensor installed is fixed on a measuring platform, and a thin film pressure sensor to be calibrated on one side is calibrated. Within the measuring range of the thin film pressure sensor, the pressure loading equipment is used to apply accurate pressure vertically to the surface of the thin film pressure sensor, and the signal collected by the measuring equipment is recorded. After data calibration, M groups of pressure-conductance matching data are obtained.

[0075] The pressure-loading device, capable of stably outputting pressure, comprises a pressure-loading actuator 2, a six-dimensional force sensor 3, and a six-degree-of-freedom robotic arm 4. The pressure-loading actuator 2 is mounted at the end of the six-degree-of-freedom robotic arm 4, and the six-dimensional force sensor 3 is mounted between the end of the six-degree-of-freedom robotic arm 4 and the pressure-loading actuator 2. The six-degree-of-freedom robotic arm 4 can carry the pressure-loading actuator 2 to the location of the thin film pressure sensor to be calibrated and adjust the force output direction to be perpendicular to the surface of the thin film pressure sensor. By controlling the six-degree-of-freedom robotic arm 4, the pressure-loading actuator 2 applies pressure to the thin film pressure sensor 1, and accurate pressure loading is achieved using force data feedback from the six-dimensional force sensor 3.

[0076] In this embodiment, the six-degree-of-freedom robotic arm 4 utilizes the Universal Robots UR3, with a maximum load of 3 kg. The six-dimensional force sensor 3 utilizes the Kunwei Technology KWR75A, capable of detecting a maximum force of 50 N in three orthogonal directions with a resolution of 0.03% FS. The pressure-loading actuator 2 is 3D-printed from PLA. Its bottom can be either a smooth surface or shaped with protrusions of varying shapes, enabling it to simulate collisions or compression of the thin-film pressure sensor by various objects. The robotic arm is moved so that the bottom surface of the pressure-loading actuator 2 is parallel to the surface of the thin-film pressure sensor 1.

[0077] The measuring device capable of collecting information of the thin film pressure sensor in real time includes a single-chip microcontroller MCU5, a computer 6 and a measuring circuit (see Figure 4 ), MCU is the abbreviation of Micro Control Unit.

[0078] In this embodiment, MCU 5 uses a Cortex-M3 core, model STM32F103C8T6, and a built-in analog-to-digital conversion module with a 12-bit resolution for collecting voltage changes in the measurement circuit. Figure 4 As shown, the sensor element is connected in series with a fixed resistance element. A fixed voltage is applied to both ends of the two elements. The connection between the two elements is connected to the analog-to-digital conversion interface of the MCU. The conversion formula between the MCU acquisition signal and the conductivity of the thin film pressure sensor to be calibrated is:

[0079]

[0080] Among them G v is the conductivity value of the thin film pressure sensor to be calibrated, R v is the resistance value of the thin film pressure sensor to be calibrated, V adc is the value collected by MCU, V full is the theoretical maximum value, V adc Range and V full The size of V is related to the resolution of MCU analog-to-digital conversion. full is 2 12 ,, R1 is a fixed value resistor connected in series. The parameters provided in the embodiment of the present application are: V full is 2 12 , R1 is 330Ω, V adc The range is 0~4096.

[0081] In this embodiment, the computer is used to receive the signal acquisition data transmitted by the MCU, calculate the conductivity change of the thin film pressure sensor 1 to be calibrated according to the conversion formula, and establish a connection with the six-dimensional force sensor 3 and the six-degree-of-freedom robotic arm 4 to simultaneously save the pressure and conductivity data of the thin film pressure sensor 1 to be calibrated.

[0082] Specifically, the calibration method includes the following steps:

[0083] Step B1: Install thin film pressure sensors 1 of corresponding sizes on all joints of the wheelless snake-like robot, with a total of 1 to N thin film pressure sensors 1 installed on each side of each joint;

[0084] Step B2: Fix all joints on the test platform in turn, calibrate the thin film pressure sensors 1 on different sides of each joint, and calibrate the thin film pressure sensors 1 of the next joint after calibrating all the thin film pressure sensors 1 of one joint. The process of calibrating any thin film pressure sensor 1 is as follows:

[0085] Step B21: using the six-degree-of-freedom robotic arm 4 to drive the pressure-loading actuator 2 to apply M sets of pressure values ​​to the thin film pressure sensor 1, with the direction of the applied force being perpendicular to the surface of the thin film pressure sensor 1;

[0086] Step B22: The pressure value applied by the pressure-loading actuator 2 is collected by the six-dimensional force sensor 3 and sent to the computer 6; the single-chip microcontroller MCU5 synchronously collects the conductivity data of the thin film pressure sensor 1; a total of M groups of pressure-conductance matching data are obtained as calibration data of the thin film pressure sensor 1 and stored in the computer 6.

[0087] The process of the single-chip microcontroller MCU5 synchronously collecting the conductivity data of the thin film pressure sensor 1 is as follows:

[0088] Step C1: Two signal lines of the thin film pressure sensor 1 are connected to the thin film pressure sensor data acquisition circuit. Specifically, one signal line of the thin film pressure sensor 1 is connected to a constant voltage DC power supply VCC, and the other signal line of the thin film pressure sensor 1 is connected to one end of a fixed resistor R1 and an input end of a single-chip microcontroller MCU5. The other end of the fixed resistor R1 is grounded. The single-chip microcontroller MCU5 has a built-in analog-to-digital conversion module.

[0089] Step C2: Connect the fixed resistor R1 in series with the resistance value R of the thin film pressure sensor to be calibrated. v The voltage V output from the common node adc Collected by the single-chip microcontroller MCU5;

[0090] Step C3: The single-chip microcontroller MCU5 processes the collected voltage V adc After the analog-to-digital conversion, the conductivity value of the thin film pressure sensor to be calibrated is obtained according to the following formula, and the data is sent to the computer 6 through the serial port:

[0091]

[0092] In this embodiment, within the measuring range of the thin film pressure sensor, the computer controls the robotic arm to apply multiple sets of precise forces to the thin film pressure sensor, synchronously reads the output data of the thin film pressure sensor through the computer, saves the applied force and the read data, and finally processes the saved data to achieve data calibration.

[0093] After the film pressure sensors on all joints are calibrated, the joints are installed on the wheelless snake-like robot.

[0094] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in conjunction with other described embodiments.

Claims

1. A thin film pressure sensor for a wheelless snake-like robot, characterized in that: The thin film pressure sensor (1) comprises a connection base (1-1), a first connection layer (1-2), a first insulating layer (1-3), a first electrode layer (1-4), a piezoresistive sensitive layer (1-5), a second electrode layer (1-6), a second insulating layer (1-7), a second connection layer (1-8) and a wear-resistant and anti-slip protective layer (1-9) arranged in sequence from bottom to top; each layer is made of a thin film bendable material, and each layer is custom-cut and pasted according to the surface shape of the wheelless snake robot joint module through a lamination method; The wear-resistant and anti-skid protective layer (1-9) is made of nitrile rubber and serves as a skin protector; The connecting matrix (1-1) is made of polylactic acid (PLA) material; The piezoresistive sensitive layer (1-5) is made of Velostat polymer material; The first insulating layer (1-3) and the second insulating layer (1-7) are made of polyester single-sided tape, and the backing material is polyester film; The first electrode layer (1-4) and the second electrode layer (1-6) are made of copper foil; The first connecting layer (1-2) and the second connecting layer (1-8) are made of polyacrylate double-sided tape; The four sides of the first electrode layer (1-4) in the middle layer are all retracted by a distance d / 2 relative to the outer edges of the first insulating layer (1-3) and the piezoresistive sensitive layer (1-5); the edge region of the first insulating layer (1-3) is bonded to the edge region of the piezoresistive sensitive layer (1-5), and the other regions of the first insulating layer (1-3) are bonded to the first electrode layer (1-4); The four sides of the second electrode layer (1-6) in the middle layer are all retracted by a distance d / 2 compared to the outer edges of the second electrode layer (1-6) and the piezoresistive sensitive layer (1-5); the edge area of ​​the second insulating layer (1-7) is bonded to the edge area of ​​the piezoresistive sensitive layer (1-5), and the other areas of the second insulating layer (1-7) are bonded to the second electrode layer (1-6).

2. A method for preparing a thin film pressure sensor for a wheelless snake-like robot, the method being the method for preparing a thin film pressure sensor for a wheelless snake-like robot according to claim 1, characterized in that: The preparation method comprises the following steps: Step A1: Obtain the design dimensions of the thin film pressure sensor (1) according to the surface shape of the joint module of the wheelless snake-like robot; Step A2: cutting the wear-resistant and anti-slip protective layer (1-9), the first connecting layer (1-2), the second connecting layer (1-8), the first insulating layer (1-3), the second insulating layer (1-7), and the piezoresistive sensitive layer (1-5) to have the same design dimensions as the thin film pressure sensor (1); Step A3: cutting the copper foil of the first electrode layer (1-4) and the second electrode layer (1-6) so that the length and width are shorter than the design size of the thin film pressure sensor (1) by a distance d, and leaving an extra protruding portion at one of the corners; Step A4: fixing the two signal wires to the protruding portions of the first electrode layer (1-4) and the second electrode layer (1-6) respectively by welding; Step A5: utilizing the adhesion of the first insulating layer (1-3), fixing the first insulating layer (1-3) to the first electrode layer (1-4) and the piezoresistive sensitive layer (1-5) in sequence; The second insulating layer (1-7) is fixed sequentially to the second electrode layer (1-6) and the other side of the piezoresistive sensitive layer (1-5) by utilizing the adhesion of the second insulating layer (1-7); Step A6: using the double-sided adhesive property of the second connecting layer (1-8) to fix the wear-resistant and anti-slip protective layer (1-9) and the second insulating layer (1-7); Step A7: utilizing the double-sided adhesive property of the first connecting layer (1-2) to fix the first insulating layer (1-3) on the connecting substrate (1-1); The four sides of the first electrode layer (1-4) in the middle layer are all retracted by a distance d / 2 relative to the outer edges of the first insulating layer (1-3) and the piezoresistive sensitive layer (1-5); the edge region of the first insulating layer (1-3) is bonded to the edge region of the piezoresistive sensitive layer (1-5), and the other regions of the first insulating layer (1-3) are bonded to the first electrode layer (1-4); The four sides of the second electrode layer (1-6) in the middle layer are all retracted by a distance d / 2 compared to the outer edges of the second electrode layer (1-6) and the piezoresistive sensitive layer (1-5); the edge area of ​​the second insulating layer (1-7) is bonded to the edge area of ​​the piezoresistive sensitive layer (1-5), and the other areas of the second insulating layer (1-7) are bonded to the second electrode layer (1-6).

3. A calibration method for a thin film pressure sensor used in a wheelless snake-like robot, wherein the thin film pressure sensor used in a wheelless snake-like robot according to claim 1 is calibrated, characterized in that: The calibration method comprises the following steps: Step B1: Install thin film pressure sensors (1) of corresponding sizes on all joints of the wheelless snake-like robot, and install a total of 1 to N thin film pressure sensors (1) on each side of each joint; Step B2: Fix all joints on the test platform in turn, calibrate the thin film pressure sensors (1) on different sides of each joint, and calibrate the thin film pressure sensors (1) of the next joint after calibrating all the thin film pressure sensors (1) of one joint. The process of calibrating any thin film pressure sensor (1) is as follows: Step B21: using the six-degree-of-freedom robotic arm (4) to drive the pressure loading actuator (2) to apply M sets of pressure values ​​to the thin film pressure sensor (1), with the direction of the applied force being perpendicular to the surface of the thin film pressure sensor (1); Step B22: The pressure value applied by the pressure-loading actuator (2) is collected by the six-dimensional force sensor (3) and sent to the computer (6); the single-chip microcontroller MCU (5) synchronously collects the conductivity data of the thin film pressure sensor (1); a total of M groups of pressure-conductance matching data are obtained as calibration data of the thin film pressure sensor (1) and stored in the computer (6).

4. A calibration method for a thin film pressure sensor used in a wheelless snake-like robot according to claim 3, characterized in that: The six-dimensional force sensor (3) is installed between the end of the six-degree-of-freedom robotic arm (4) and the pressure loading actuator (2).

5. The calibration method of a thin film pressure sensor applied to a wheelless snake-like robot according to claim 3, characterized in that: The process of the single-chip microcontroller MCU (5) synchronously collecting the conductivity data of the thin film pressure sensor (1) is as follows: Step C1: The two signal lines of the thin film pressure sensor (1) are connected to the thin film pressure sensor data acquisition circuit. Specifically, one signal line of the thin film pressure sensor (1) is connected to the constant voltage DC power supply VCC, and the other signal line of the thin film pressure sensor (1) is connected to the constant value resistor R One end of 1 is connected to the input end of the single-chip microcontroller MCU (5), and the other end of the fixed resistor R1 is grounded; wherein the single-chip microcontroller MCU (5) has a built-in analog-to-digital conversion module; Step C2: Fixed value resistors in series R 1 and the resistance value of the thin film pressure sensor to be calibrated R v The voltage output from the common node V adc It is collected by a single-chip microcontroller MCU (5); Step C3: The single-chip microcontroller MCU (5) collects the voltage V adc After the analog-to-digital conversion, the conductivity value of the thin film pressure sensor to be calibrated is obtained according to the following formula, and the data is sent to the computer 6: Where, V full is the theoretical maximum value. V full The size is determined by the resolution of the analog-to-digital conversion module of the single-chip microcontroller MCU (5).

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