A Flexible Pressure Sensing Array Bending and Temperature Change Joint Compensation Method and Device

Abstract

The present invention discloses a method and device for combined compensation of bending and temperature change of a flexible pressure sensing array. The method includes obtaining a depth distribution map and a temperature distribution map of the flexible pressure sensor array from a remote acquisition device, selecting a reference position for calculating the compensation amount of each unit of the flexible pressure sensor array according to the depth distribution map and the temperature distribution map, calculating the bending strain compensation reference amount and the temperature compensation reference amount of each unit of the flexible pressure sensor array, obtaining the resistance values output by each sensing unit of the flexible pressure sensor array from a data acquisition module, and combining the corresponding bending strain compensation reference amount, temperature compensation reference amount and a pre-trained BP neural network model to obtain the true pressure applied to each unit of the flexible pressure sensor array, thereby achieving precise compensation at the sensing unit level of the flexible pressure sensor array.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensing measurement, and particularly relates to a method and device for jointly compensating bending and temperature changes of a flexible pressure sensing array. Background Art

[0002] Flexible sensors have good flexibility and ductility, and can meet harsh usage environments such as high temperature, humidity, corrosion, and vibration. Due to their excellent stability and adaptability to harsh environments, flexible pressure sensors can fabricate multiple flexible sensing units on the same substrate to form a flexible pressure sensor array according to the usage scenario. At the same time, with the gradual maturity of electronic printing technology, the advantages of simple preparation process and low cost of flexible pressure sensor arrays have become more obvious, and they have become a research hotspot for scholars at home and abroad. For example, a flexible pressure sensor array can be attached to the surfaces of capacitors, storage batteries, and power transmission and distribution lines in the power system for distributed pressure monitoring. However, two problems will inevitably occur during measurement in such a complex environment: First, the surface of the device has irregular bends, and sometimes bulges may occur due to faults; Second, the temperature on the surface of the object changes rapidly and is unevenly distributed. Due to the limitations of materials and sensing mechanisms, the output resistance of a flexible pressure sensor array will change with the changes in the temperature characteristics and bending strain characteristics of the array. For example, in the article "Design and Experiment of a Flexible Pressure-Temperature Sensor Signal Acquisition System Based on LabVIEW", the prepared flexible sensor uses a carbon black / carbon nanotube-silicone rubber conductive composite material as the sensitive material, which has good pressure-sensitive characteristics and certain temperature-sensitive characteristics; in the article "Detection of Dynamic and Static Mechanical Information of a Piezo-Piezoresistive Dual-Mode Flexible Pressure Sensor", the prepared flexible sensor using graphene material as the sensitive material has good pressure sensing performance and bending strain sensing performance at the same time. The above articles illustrate that flexible pressure sensor arrays will exhibit complex pressure characteristics when measuring pressure on the surface of an object with local temperature changes in an irregular object. Therefore, it is necessary to perform joint compensation for bending strain and temperature to ensure the accuracy of measured pressure.

[0003] Currently, some research has applied machine learning methods to solve the temperature drift of flexible pressure sensors, but it has not paid attention to the influence of the complex environment where temperature change and bending strain coexist on flexible pressure sensors, nor has it considered the precise compensation for the differences between the sensing units of the flexible pressure sensor array after arraying, which has had a very large impact on the research and application of flexible pressure sensor arrays and urgently needs to be solved. Summary of the Invention

[0004] To solve the above problems, the present invention discloses a method and device for combined compensation of bending and temperature changes of a flexible pressure sensing array. By using the resistance values output by each sensing unit of the flexible pressure sensor array, in combination with the corresponding bending strain compensation reference quantity, temperature compensation reference quantity, and a pre-trained BP neural network model, the true pressure applied to each unit of the flexible pressure sensor array is obtained, achieving precise compensation at the sensing unit level of the flexible pressure sensor array.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for combined compensation of bending and temperature changes of a flexible pressure sensing array, comprising the following steps:

[0007] S1) Obtain the depth distribution map and RGB map of the flexible pressure sensor array collected by the RGBD camera, obtain the temperature distribution map of the flexible pressure sensor array collected by the infrared camera, and obtain the resistance values output by each sensing unit of the flexible pressure sensor array.

[0008] S2) According to the RGB map, select the reference positions for calculating the compensation amounts of each unit of the flexible pressure sensor array.

[0009] S3) According to the depth distribution map and the reference positions for calculating the compensation amounts of each unit of the flexible pressure sensor array, calculate the bending strain compensation reference quantity of each unit of the flexible pressure sensor array.

[0010] S4) According to the temperature distribution map and the reference positions for calculating the compensation amounts of each unit of the flexible pressure sensor array, calculate the temperature compensation reference quantity of each unit of the flexible pressure sensor array.

[0011] S5) According to the resistance values output by each sensing unit of the flexible pressure sensor array, the bending strain compensation reference quantity of each unit of the flexible pressure sensor array, the temperature compensation reference quantity, and the pre-trained BP neural network model, obtain the true pressure applied to each unit of the flexible pressure sensor array.

[0012] Among them, step S2) according to the RGB map, select the reference positions for calculating the compensation amounts of each unit of the flexible pressure sensor array, including the following steps:

[0013] S21) Divide the sensing unit areas (hereinafter referred to as unit areas) of the depth distribution map and the temperature distribution map according to the boundaries of the sensing units of the flexible pressure sensor array in the RGB map. After division, the unit areas correspond one-to-one with the units of the flexible pressure sensor array. The unit area of the i-th row and j-th column is denoted as C(i,j), and the length and width are the same as those of the sensing unit, denoted as B 0 、B 1 .

[0014] S22) Mark several pixel points in the unit area C(i,j) as the pixel points for comprehensively evaluating the bending strain compensation reference quantity and the temperature compensation reference quantity of the unit. The positions and numbers of these pixel points are adapted to the geometric shape of the unit area. The sensing unit in the present invention is square. Considering symmetry, five special points in the unit area C(i,j) are marked and denoted as where x, y, z are the corresponding coordinates and T is the corresponding temperature. is the center point of the unit area. and are respectively selected on the y-axis and x-axis of the three-dimensional coordinate system established with the center point as the zero point. △x 1 , △x 2 , △y 1 , △y 2 are respectively the distances from the four points to the edge of the unit area. z(x) and z(y) are respectively the functions of the sensing unit contour curves corresponding to the x-axis and y-axis, and are fitted from the point cloud maps obtained from the depth distribution maps.

[0015] S23) Calculate the arc length L of z(x) x0 The expression is:

[0016]

[0017] Due to the influence of the bending strain, L x0 ≥B 0 , and the length of the bent sensing unit is always B 0 . By controlling the magnitudes of △x 1 , △x 2 calculate the arc length L on the z(x) curve x :

[0018]

[0019] L x The corresponding arc is the arc of the sensing unit after bending on the x-axis.

[0020] S24) Calculate in the same way as step S23) and positions.

[0021] Step S3) Calculate the reference positions according to the depth distribution map and the compensation amounts of each unit of the flexible pressure sensor array, and calculate the bending strain compensation reference amounts of each unit of the flexible pressure sensor array, including:

[0022] The formula for calculating the bending strain ε of the sensing unit is:

[0023]

[0024] Among them, B is the strain width of the flexible pressure sensor array unit, h is the warping height of the flexible pressure sensor array unit, and λ is the bending strain material coefficient of the flexible sensor, and the expression is:

[0025]

[0026] Among them, d f and d s are the thicknesses of the insulating layer and the sensitive layer of the flexible pressure sensor array unit respectively. The expression formulas of η and χ are η = d f / d s and χ = Y f / Y s , Y f and Y s are the Young's moduli of the insulating layer and the sensitive layer of the flexible pressure sensor array unit respectively.

[0027] The formula for calculating the compensated bending strain reference quantity ε (i,j) of the sensing unit C(i,j) is:

[0028]

[0029] Among them, ε x , ε y are the bending strain reference quantities of the sensing unit with respect to the x-axis and the y-axis respectively, β 0 , β 1 are the bending strain evaluation coefficients. ε x is calculated from the positional relationship of the three evaluation points, and the expression is:

[0030]

[0031] Among them, B x represents the width of the bending strain of the sensing unit on the x-axis, and the expression is B x =|x 3 -x 4 |, x 3 , x 4 are the x-coordinate values of the evaluation point , represents the warping height of the bending strain of the sensing unit on the x-axis, and the expression is:

[0032]

[0033] Among them, z 0 , z 3 , z 4 are the z-coordinate values of the evaluation point , |z 3 -z0 |and| z 4 -z 0 |represent the warpage heights of the left and right halves of the sensing unit respectively, and γ 1 , γ 2 is the warpage height weighting coefficient. Substituting it in, we can obtain the expression of ε x with respect to the coordinates of the evaluation point:

[0034]

[0035] Similarly, ε y is calculated from the positional relationship of . Let the warpage height weighting coefficient in the expression of ε y be γ 3 , γ 4 , and ε x , ε y Substituting these values, we obtain the reference amount of compensated bending strain for the sensing unit C(i,j).

[0036] Step S4) Calculate the reference position according to the compensation amounts of each unit of the flexible pressure sensor array based on the temperature distribution map, and calculate the temperature compensation reference amounts of each unit of the flexible pressure sensor array, including:

[0037] The calculation formula for the temperature compensation reference amount of the sensing unit C(i,j) is:

[0038]

[0039] where T m , m = 0, 1, 2, 3, 4 represent the temperatures of five evaluation points. Considering that the resolution limit of the infrared camera may cause data loss at the evaluation points on the temperature distribution map, in this case, the temperature of this evaluation point is taken as the temperature value of the pixel point closest to this evaluation point, and α (m = 0, 1, 2, 3, 4) are the temperature evaluation coefficients of the five evaluation points. m (m = 0, 1, 2, 3, 4) are the temperature evaluation coefficients of the five evaluation points.

[0040] Step S5) Obtain the true pressure applied to each unit of the flexible pressure sensor array according to the resistance values output by each sensing unit of the flexible pressure sensor array, the bending strain compensation reference amounts and temperature compensation reference amounts of each unit of the flexible pressure sensor array, and the pre-trained BP neural network model, including:

[0041] S51) Collect BP neural network training sample data: Arrange the flexible pressure sensor array on a rigid curved surface, calculate the bending strain ε of each sensing unit, and apply pressures of magnitude A 1 to A 2 , every A 0For the spaced pressure F, change the temperature T of the test sensing unit under each pressure sample, and the temperature range is B 1 to B 2 and, every B 0 is the interval, measure the output resistance value corresponding to the sensing unit under the combined action of a certain bending strain ε, a certain test pressure F, and a certain test temperature T, and take it as a group of samples. A total of P groups of samples are measured.

[0042] S52) Configure a neural network. The BP neural network includes an input layer, a hidden layer, and an output layer. The input layer includes three input nodes, which respectively input the bending strain of the sensing unit, the test temperature of the sensing unit, and the output resistance value of the sensing unit. The output layer includes one output node, which outputs the corresponding test pressure of the sensing unit.

[0043] Initialize the neural network, select the activation function between each layer of the BP neural network, determine the number of hidden layers, and divide parameters such as the proportion of the training set and the test set.

[0044] Train the neural network. The BP neural network outputs the predicted value of the sensing unit pressure through forward propagation. If the error between the predicted value of the sensing unit pressure and the true value of the sensing unit pressure does not meet the requirements, the error is backpropagated in the neural network, and the connection weights and offsets between neurons in each layer are adjusted layer by layer, so that the error continuously decreases, that is, the predicted value of the sensing unit pressure continuously approaches the true value of the sensing unit pressure. Repeat this process until the training reaches the set error threshold or reaches the maximum number of training times.

[0045] S53) Input the output resistance value, bending strain compensation reference quantity, and temperature compensation reference quantity of each sensing unit of the measured flexible pressure sensor array into the BP neural network model in step S52) to obtain the true value of the pressure applied to each unit.

[0046] A flexible pressure sensing array bending and temperature change joint compensation device includes an RGBD camera, an infrared camera, a data acquisition module, and a terminal processing module.

[0047] The RGBD camera collects the RBG map and depth distribution map of the flexible pressure sensor array;

[0048] The infrared camera collects the temperature distribution map of the flexible pressure sensor array;

[0049] The data acquisition module collects the resistance values output by each sensing unit of the flexible pressure sensor array;

[0050] The terminal processing module uses the flexible pressure sensing array bending and temperature change joint compensation method to perform pressure compensation on each sensing unit of the flexible pressure sensor array and outputs the true pressure values of each sensing unit of the flexible pressure sensor array.

[0051] In addition, the terminal processing module will complete the priority scanning of the units with drastic changes in output values according to the bending changes and temperature compensation reference quantities of each unit collected in the previous two rounds, so as to improve the real-time performance of the sensing of the entire device, specifically as follows:

[0052] Let the priority scanning rate of the sensing unit C be A, and the expression is A = η 1 (|ε 2 - ε 1 | / ε 1 ) + η 2 (|T 2 - T 1 | / T 1 ), where ε 1 , T 1 are the bending strain and temperature compensation reference quantities of the first round of unit C, and ε 2 , T 2 are the bending strain and temperature compensation reference quantities of the second round of unit C. η 1 , η 2 are the weighting coefficients of the bending strain change rate and the temperature change rate respectively, and are related to the shape and array distribution of the sensing unit. The terminal processing module assigns the scanning order of the next round of the flexible pressure sensor array according to the magnitude of the priority scanning rate.

[0053] The beneficial effects of the present invention are as follows:

[0054] (1) Focusing on the complex pressure characteristics shown by the flexible pressure sensor array when measuring pressure on the surface of an object with local temperature change on an irregular object, the present invention proposes a method for jointly compensating the bending and temperature changes of the flexible pressure sensing array, and uses an infrared camera and a depth camera to accurately and efficiently calculate the bending strain compensation amount and temperature compensation amount of each sensing unit of the flexible pressure sensor array, providing reliable input for subsequent BP neural network to compensate the pressure value.

[0055] (2) In the method for jointly compensating the bending and temperature changes of the flexible pressure sensing array provided by the present invention, the calculation formula of the bending strain and temperature compensation reference quantity of the sensing unit includes material parameter information and weighting coefficients, supports the flexible pressure sensor array based on different types of flexible substrate materials, realizes accurate compensation of the pressure sensor array, and further increases the applicability of the compensation method.

[0056] (3) The present invention uses a BP neural network to realize the restoration of the real pressure value. This method is simple to implement and has high accuracy, greatly improving the accuracy of the flexible pressure sensor array during use. At the same time, when training the BP neural network model, the differential precise compensation between the sensing units of the flexible pressure sensor array is considered, and the difference in the bending strain amount of the sensing unit is controlled and recorded as a training sample during testing, further expanding the application scenario of the flexible pressure sensor array. Description of the Drawings

[0057] Figure 1 is a flowchart of the method of the present invention;

[0058] Figure 2 is a schematic diagram of the selection of the evaluation positions of the sensing units of the present invention;

[0059] Figure 3 is a schematic diagram of the bending strain of the sensing units of the present invention;

[0060] Figure 4 is a structure diagram of the BP neural network used in the present invention;

[0061] Figure 5 is a distribution diagram of the pressure compensation error of the present invention. Detailed Embodiments

[0062] The present invention will be further clarified below in conjunction with the drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0063] As Figure 1 shown, a method for joint compensation of bending and temperature changes of a flexible pressure sensing array described in this embodiment includes the following steps, specifically as follows:

[0064] S1) Obtain the depth distribution map and RGB map of the flexible pressure sensor array collected by the RGBD camera, obtain the temperature distribution map of the flexible pressure sensor array collected by the infrared camera, and obtain the resistance values output by each sensing unit of the flexible pressure sensor array.

[0065] S2) Select the reference positions for calculating the compensation amounts of each unit of the flexible pressure sensor array according to the RGB map.

[0066] S3) Calculate the reference amounts of bending strain compensation for each unit of the flexible pressure sensor array according to the depth distribution map and the reference positions for calculating the compensation amounts of each unit of the flexible pressure sensor array.

[0067] S4) Calculate the reference amounts of temperature compensation for each unit of the flexible pressure sensor array according to the temperature distribution map and the reference positions for calculating the compensation amounts of each unit of the flexible pressure sensor array.

[0068] S5) Obtain the actual pressures applied to each unit of the flexible pressure sensor array according to the resistance values output by each sensing unit of the flexible pressure sensor array, the reference amounts of bending strain compensation for each unit of the flexible pressure sensor array, the reference amounts of temperature compensation, and the pre-trained BP neural network model.

[0069] Among them, step S2) of selecting the reference positions for calculating the compensation amounts of each unit of the flexible pressure sensor array according to the RGB map includes the following steps:

[0070] S21) Divide the sensing unit areas of the depth distribution map and the temperature distribution map (hereinafter referred to as unit areas) according to the boundaries of the sensing units of the flexible pressure sensor array in the RGB map. After segmentation, the unit areas correspond one by one to the units of the flexible pressure sensor array. The unit area in the i-th row and j-th column is denoted as C(i,j), and its length and width are the same as those of the sensing unit, denoted as B 0 , B 1 .

[0071] In this embodiment, the selected flexible pressure sensor array is a 4-row and 4-column array, with a total of 16 sensing units. The sensing unit is a square with a side length equal to 10 mm, so B 0 = B 1 = 10 mm.

[0072] S22) Mark several pixel points in the unit area C(i,j) as the pixel points for comprehensively evaluating the bending strain compensation reference quantity and the temperature compensation reference quantity of the unit. The positions and numbers of these pixel points are adapted to the geometric shape of the unit area. The sensing unit in the present invention is a square. As Figure 2 shown, considering symmetry, five special points in the unit area C(i,j) are marked and denoted as where x, y, z are the corresponding coordinates and T is the corresponding temperature, is the center point of the unit area, and are respectively selected on the y-axis and x-axis of the three-dimensional coordinate system established with the center point as the zero point. △x 1 , △x 2 , △y 1 , △y 2 are respectively the distances from the four points to the edge of the unit area. z(x) and z(y) are respectively the functions of the sensing unit contour curves corresponding to the x-axis and y-axis, and are fitted from the point cloud map obtained from the depth distribution map.

[0073] S23) On the basis of the previous step, calculate the position of . Taking the calculation of as an example, the arc length L x0 expression of z(x) is:

[0074]

[0075] Due to the influence of the bending strain, L x0 ≥B 0 , and the length of the bent sensing unit is always B 0 . By controlling the sizes of △x 1 , △x 2 , calculate the arc length L x, in this embodiment, considering that in actual measurement, it is impossible to predict the distance between the sensing unit and the edge of the unit area after bending strain, so △x is controlled 1 , △x 2 When determining the size of, △x 1 follows the principle of △x 2 = △x x . The expression of the arc length L

[0076]

[0077] L x The corresponding arc is the arc of the sensing unit on the x-axis after bending.

[0078] S24) Calculate in the same way as step S23) and positions.

[0079] Step S3) Calculate the reference position according to the depth distribution map and the compensation amount of each unit of the flexible pressure sensor array, and calculate the bending strain compensation reference amount of each unit of the flexible pressure sensor array, including:

[0080] As Figure 3 shown, the formula for calculating the bending strain ε of the sensing unit is:

[0081]

[0082] Among them, B is the strain width of the flexible pressure sensor array unit, h is the warping height of the flexible pressure sensor array unit, and λ is the bending strain material coefficient of the flexible sensor, and the expression is:

[0083]

[0084] Among them, d f and d s are the thicknesses of the insulating layer and the sensitive layer of the flexible pressure sensor array unit respectively. The expression formulas of η and χ are η = d f / d s and χ = Y f / Y s , Y f and Y s are the Young's moduli of the insulating layer and the sensitive layer of the flexible pressure sensor array unit respectively. In this embodiment, the Young's moduli of the sensitive layer (PI is the flexible substrate, Pt thin film is the sensitive material) and the insulating layer (PMMA) of the flexible pressure sensor array sensing unit are close, and the thickness of the sensitive layer is equal to the thickness of the insulating layer, both are 0.5 mm, so λ = 1 is taken.

[0085] The formula for calculating the compensated bending strain reference amount ε (i,j) of the sensing unit C(i,j) is:

[0086]

[0087] where ε x , ε y are respectively the reference bending strain amounts of the sensing unit with respect to the x-axis and the y-axis, and β 0 , β 1 are the bending strain amount evaluation coefficients. ε x is calculated from the positional relationship of three evaluation points, and the expression is:

[0088]

[0089] where B x represents the width of the bending strain of the sensing unit on the x-axis, and the expression is B x = |x 3 - x 4 |, and x 3 , x 4 are the x-coordinate values of the evaluation point . represents the warping height of the bending strain of the sensing unit on the x-axis, and the expression is:

[0090]

[0091] where z 0 , z 3 , z 4 are the z-coordinate values of the evaluation point . |z 3 - z 0 | and |z 4 - z 0 | respectively represent the warping heights of the left and right halves of the sensing unit, and γ 1 , γ 2 are the warping height weighting coefficients. Substituting, the expression of ε x with respect to the evaluation point coordinates can be obtained:

[0092]

[0093] Similarly, ε y is calculated from the positional relationship of . Let the warping height weighting coefficients in the expression of ε y be γ 3 , γ 4 , and substituting ε x , ε y obtains the compensated bending strain reference amount of the sensing unit C(i, j).

[0094] In this embodiment, considering that the deformation position of the sensing unit is unknown during actual measurement and is the center point of the sensing unit, so the warping height weighting coefficient γ is taken 1 = γ 2 = γ 3 = γ 4 = 0.5, and ε is calculated x , ε y , also considering that the deformation position is unknown and the sensing unit is square and has symmetry, the bending strain evaluation coefficient β is taken 0 = β 1 = 0.5

[0095] Step S4) Calculate the reference position according to the compensation amount of each unit of the flexible pressure sensor array based on the temperature distribution map, and calculate the temperature compensation reference amount of each unit of the flexible pressure sensor array, including:

[0096] The calculation formula for the temperature compensation reference amount of the sensing unit C(i, j) is:

[0097]

[0098] where T m , m = 0, 1, 2, 3, 4 represents the temperature of the five evaluation points. Considering that the resolution limit of the infrared camera may cause data loss at the evaluation points on the temperature distribution map, in this case, the temperature of this evaluation point is taken as the temperature value of the pixel point closest to this evaluation point, and α (m = 0, 1, 2, 3, 4) are the temperature evaluation coefficients of the five evaluation points m (m = 0, 1, 2, 3, 4) are the temperature evaluation coefficients of the five evaluation points

[0099] In this embodiment, considering that the selection factors of the temperature evaluation coefficient are the same as those of the bending strain evaluation coefficient, so the temperature evaluation coefficient α is taken 0 = α 1 = α 2 = α 3 = α 4 = 0.5

[0100] Step S5) Obtain the true pressure applied to each unit of the flexible pressure sensor array according to the resistance values output by each sensing unit of the flexible pressure sensor array, the bending strain compensation reference amount of each unit of the flexible pressure sensor array, the temperature compensation reference amount, and the pre-trained BP neural network model, including:

[0101] S51) Collect BP neural network training sample data: In this embodiment, the training samples are obtained by COMSOL Multiphysics simulation calculation. Select "two-dimensional axis of symmetry" in the spatial dimension, simplify the calculation with a two-dimensional model, and set the flexible pressure sensor array in an expression of y = 2.0 (x / 7)On the surface, calculate the bending strain ε of each sensing unit. Apply pressures F ranging from 0 to 50 N to each sensing unit at intervals of 10 N. At each pressure sample, change the temperature T of the tested sensing unit within the range of 25 °C to 115 °C at intervals of 10 °C. Measure the corresponding output resistance values of the sensing unit under the combined action of a certain bending strain ε, a certain tested pressure F, and a certain tested temperature T as a set of samples, and a total of 300 sets of samples are measured.

[0102] S52) As Figure 4 shown, configure a neural network. The BP neural network includes an input layer, a hidden layer, and an output layer. The input layer includes three input nodes, which respectively input the bending strain of the sensing unit, the tested temperature of the sensing unit, and the output resistance of the sensing unit. The output layer includes one output node, which outputs the corresponding tested pressure of the sensing unit.

[0103] Initialize the neural network. The activation functions of the hidden layer of the BP neural network all adopt the tansig function. The number of hidden layers is 15. Select 85% of the samples as the training set, and the remaining 15% of the samples as the test set. The maximum number of training times is 1000, the learning rate is 0.01, and the error threshold is 0.0000001.

[0104] Train the neural network. The BP neural network outputs the predicted value of the sensing unit pressure through forward propagation. If the error between the predicted value of the sensing unit pressure and the true value of the sensing unit pressure does not meet the requirements, then the error is backpropagated in the neural network, and the connection weights and offsets between neurons in each layer are adjusted layer by layer, so that the error continuously decreases, that is, the predicted value of the sensing unit pressure continuously approaches the true value of the sensing unit pressure. Repeat this process until the training reaches the set error threshold or reaches the maximum number of training times.

[0105] S53) Input the output resistance values, bending strain compensation reference quantities, and temperature compensation reference quantities of each sensing unit of the measured flexible pressure sensor array into the BP neural network model in step S52) to obtain the true values of the pressures applied to each unit.

[0106] For the trained BP neural network model, the error distribution of all samples is as Figure 5 shown. After the combined compensation of bending strain and temperature change, the percentage of the relative error between the pressure compensation value and the true value is controlled within 0.4%, and the compensation accuracy is high.

[0107] A device for joint compensation of bending and temperature changes of a flexible pressure sensing array includes an RGBD camera, an infrared camera, a data acquisition module, and a terminal processing module.

[0108] The RGBD camera collects the RBG image and depth distribution map of the flexible pressure sensor array;

[0109] An infrared camera, which collects the temperature distribution map of the flexible pressure sensor array;

[0110] A data acquisition module, which collects the resistance values output by each sensing unit of the flexible pressure sensor array;

[0111] A terminal processing module, which uses the combined compensation method of bending and temperature change of the flexible pressure sensing array to perform pressure compensation on each sensing unit of the flexible pressure sensor array and outputs the true pressure values of each sensing unit of the flexible pressure sensor array.

[0112] In addition, the terminal processing module will complete the priority scanning of the units with drastic changes in the output value according to the bending strain and temperature compensation reference quantities of each unit collected in the previous two rounds, so as to improve the real-time performance of the sensing of the entire device. Specifically as follows:

[0113] Let the priority scanning rate of the sensing unit C be A, and the expression is A = η 1 (|ε 2 - ε 1 | / ε 1 ) + η 2 (|T 2 - T 1 | / T 1 ), where ε 1 , T 1 are the bending strain and temperature compensation reference quantities of the C unit in the first round, and ε 2 , T 2 are the bending strain and temperature compensation reference quantities of the C unit in the second round. η 1 , η 2 are the weighting coefficients of the bending strain change rate and the temperature change rate respectively, and are related to the shape of the sensing unit and the array distribution. The terminal processing module assigns the scanning order of the next round of the flexible pressure sensor array according to the magnitude of the priority scanning rate.

[0114] In this embodiment, since the sensing unit is square and has symmetry, η 1 = η 2 = 0.5.

[0115] It should be noted that the above content only illustrates the technical idea of the present invention and cannot limit the protection scope of the present invention. For those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements all fall within the protection scope of the claims of the present invention.

Claims

1. A combined compensation method for bending and temperature variation of a flexible pressure sensing array, characterized in that, it includes the following steps: S1) Obtain the depth distribution map and RGB map of the flexible pressure sensor array collected by the RGBD camera, obtain the temperature distribution map of the flexible pressure sensor array collected by the infrared camera, and obtain the resistance values output by each sensing unit of the flexible pressure sensor array; S2) According to the RGB map, select the reference positions for calculating the compensation amounts of each unit of the flexible pressure sensor array; including: According to the boundaries of the sensing units of the flexible pressure sensor array in the RGB image, the sensing unit areas of the depth distribution map and the temperature distribution map are divided. After segmentation, the unit areas correspond one-to-one with the units of the flexible pressure sensor array. The unit area in the i-th row and j-th column is denoted as C(i,j), and its length and width are the same as those of the sensing unit, denoted as B 0 , B 1 ; Mark several special pixel points in the unit area C(i,j) as the calculation reference points for comprehensively evaluating the bending strain compensation reference quantity and the temperature compensation reference quantity of the unit The selection position and number of calculation reference points are adapted to the geometric shape of the unit area. The sensing unit is square and has symmetry. Therefore, five special points in the unit area C(i,j) are marked and denoted as where x, y, z are the corresponding coordinates and T is the corresponding temperature, is the center point of the unit area, and are respectively selected on the y-axis and x-axis of the three-dimensional coordinate system established with the center point as the zero point; S3) According to the depth distribution map and the reference positions for calculating the compensation amounts of each unit of the flexible pressure sensor array, calculate the reference amounts for bending strain compensation of each unit of the flexible pressure sensor array; including: Calculate the bending strain compensation reference quantity ε of the sensing unit area C(i,j) (i,j) The formula for ε (i,j) is: ε 0 =(β x ε 1 +β y ε 0 ) / (β 1 +β x ), where ε y , ε 0 are the bending strain reference quantities of the sensing unit with respect to the x-axis and y-axis respectively, and β 1 , β x are the bending strain evaluation coefficients; ε x is calculated from the positional relationship of three evaluation points, and the expression is where B x represents the width of the bending strain of the sensing unit on the x-axis, and the expression is B 3 =|x 4 -x 3 |, and x 4 , x 0 are the x-coordinate values of the evaluation points , represents the warping height of the bending strain of the sensing unit on the x-axis, and the expression is: where z 3 , z 4 , z 3 are the z-coordinate values of the evaluation points , |z 0 -z 4 | and |z 0 -z 1 | respectively represent the warping heights of the left and right halves of the sensing unit, and γ 2 , γ x are the warping height weighting coefficients. Substituting them can obtain the expression of ε y with respect to the evaluation point coordinates; similarly, ε y is calculated from the positional relationship of . Let the warping height weighting coefficients in the expression of ε 3 , γ 4 , and substitute ε x , ε y to obtain the bending strain compensation reference quantity of the sensing unit area C(i,j); S4) According to the temperature distribution map and the reference positions for calculating the compensation amounts of each unit of the flexible pressure sensor array, calculate the reference amounts for temperature compensation of each unit of the flexible pressure sensor array; S5) According to the resistance values output by each sensing unit of the flexible pressure sensor array, the reference amounts for bending strain compensation of each unit of the flexible pressure sensor array, the reference amounts for temperature compensation, and the pre-trained BP neural network model, obtain the true pressures applied to each unit of the flexible pressure sensor array.

2. The combined compensation method for bending and temperature variation of a flexible pressure sensing array according to claim 1, characterized in that, Step S3) Calculate The arc length L of z(x) x0 The expression is as follows: Δx 1 , Δx 2 , are the distances from the point to the edge of the unit area respectively, z(x) is the function of the contour curve of the sensing unit corresponding to the x-axis, which is fitted from the point cloud map obtained from the depth distribution map. Due to the influence of bending strain, L x0 ≥B 0 , and the length of the bent sensing unit is always B 0 , by controlling Δx 1 , Δx 2 to calculate the arc length L on the z(x) curve x : L x The corresponding arc is the arc of the sensing unit on the x-axis after bending; similarly, calculate and positions.

3. A combined compensation method for bending and temperature variation of a flexible pressure sensing array according to claim 1, characterized in that, The formula for calculating the bending strain ε of the sensing unit is: Among them, B is the strain width of the flexible pressure sensor array unit, h is the warping height of the flexible pressure sensor array unit, and λ is the bending strain material coefficient of the flexible sensor, and the expression is: λ = (d f + d s )(1 + 2η + χη 2 ) / (1 + η)(1 + χη); where, d f and d s are the thicknesses of the insulating layer and the sensitive layer of the flexible pressure sensor array unit respectively; the expression formulas of η and χ are η = d f / d s and χ = Y f / Y s , Y f and Y s are the Young's moduli of the insulating layer and the sensitive layer of the flexible pressure sensor array unit respectively.

4. A combined compensation method for bending and temperature variation of a flexible pressure sensing array according to claim 1, characterized in that, The formula for calculating the reference amount for temperature compensation in S4) is: where T m , m = 0, 1, 2, 3, 4 represents the temperatures of five evaluation points. Considering that the resolution limit of the infrared camera may cause data loss at the evaluation points on the temperature distribution map, in this case, the temperature of this evaluation point is taken as the temperature value of the pixel point closest to this evaluation point, α m (m = 0, 1, 2, 3, 4) are the temperature evaluation coefficients of the five evaluation points.

5. A combined compensation method for bending and temperature variation of a flexible pressure sensing array according to claim 1, characterized in that, S5) The obtaining of the true pressures applied to each unit of the flexible pressure sensor array according to the resistance values output by each sensing unit of the flexible pressure sensor array, the reference amounts for bending strain compensation of each unit of the flexible pressure sensor array, the reference amounts for temperature compensation, and the pre-trained BP neural network model includes: S51) Collect BP neural network training sample data; S52) Train the neural network according to the training sample data; S53) Input the resistance values output by each sensing unit of the measured flexible pressure sensor array, the reference amounts for bending strain compensation, and the reference amounts for temperature compensation into the BP neural network model in step S52) to obtain the true values of the pressures applied to each unit.

6. The combined compensation method for bending and temperature variation of a flexible pressure sensing array according to claim 5, characterized in that, The BP neural network includes an input layer, a hidden layer and an output layer. The input layer includes three input nodes, which respectively input the bending strain of the sensing unit, the test temperature of the sensing unit, and the resistance value output by the sensing unit. The output layer includes one output node, which outputs the test pressure of the corresponding sensing unit.

7. A combined compensation device for bending and temperature variation of a flexible pressure sensing array, characterized in that, it includes: RGBD camera, infrared camera, data acquisition module, terminal processing module; The RGBD camera collects the RBG map and depth distribution map of the flexible pressure sensor array; Infrared camera,collected temperature distribution map of flexible pressure sensor array; A data acquisition module collects the resistance value output by each sensing unit of the flexible pressure sensor array; The terminal processing module uses the method described in any one of claims 1 to 6 to perform pressure compensation on each sensing unit of the flexible pressure sensor array, and outputs the real pressure value of each sensing unit of the flexible pressure sensor array.

8. A flexible pressure sensing array bending and temperature change combined compensation device according to claim 7, It is characterized in that The terminal processing module will complete the priority scanning of the units with drastic output value changes based on the bending strain and temperature compensation reference of each unit collected in the first two rounds, so as to improve the real-time sensing performance of the entire device, including: Let the priority scanning rate of the sensing unit C be A, and the expression is A = η 1 (|ε 2 -ε 1 | / ε 1 ) + η 2 (|T 2 -T 1 | / T 1 ), where ε 1 , T 1 are the bending strain and temperature compensation reference quantities of the C first-round unit, and ε 2 , T 2 are the bending strain and temperature compensation reference quantities of the C second-round unit. η 1 , η 2 are the weighting coefficients of the bending strain change rate and the temperature change rate respectively, which are related to the shape and array distribution of the sensing unit; the terminal processing module assigns the scanning order of the next-round flexible pressure sensor array according to the magnitude of the priority scanning rate.

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