A flexible array pressure sensing system for coping with local temperature changes of irregular objects

Abstract

The present invention discloses a flexible array pressure sensing system for coping with local temperature changes of irregular objects. The present invention obtains a depth distribution map and a temperature distribution map from a remote non-contact image acquisition module, and according to the depth distribution map and the temperature distribution map, obtains the bending strain compensation reference quantity and the temperature compensation reference quantity of each unit of the array. According to the compensation reference quantity and the resistance value, the flexible pressure sensor array compensation is realized, ensuring the accuracy of the measured pressure.

Description

Technical Field

[0001] The present invention relates to a flexible array pressure sensing system for coping with local temperature changes of irregular objects, and belongs to the technical field of sensing measurement. Background Art

[0002] As a branch of flexible sensors, the research on the manufacturing materials, output performance and sensing principle of flexible pressure sensors has become increasingly mature. The flexible pressure sensor array made of flexible pressure sensors has been widely used in robot electronic skin, human health monitoring, motion monitoring and other aspects due to its good flexibility and the advantage of realizing distributed pressure measurement. In addition to these conventional application fields, flexible pressure sensor arrays are also applicable to power equipment monitoring.

[0003] Capacitors, storage batteries and transmission and distribution lines in the power system all have the need for distributed temperature and pressure monitoring. However, the traditional monitoring methods have problems such as only performing temperature monitoring, high cost and inconvenient installation. The flexible pressure sensor array can be attached to the surface of these irregular devices for distributed pressure monitoring. However, monitoring these devices is often accompanied by two problems: First, the surface of the device has irregular bends and sometimes bulges, which makes the closely attached flexible pressure sensor array uneven; Second, the temperature on the object surface changes rapidly and is unevenly distributed.

[0004] Due to the limitations of materials and sensing mechanisms, the output resistance value of the flexible pressure sensor array will change with the changes of the array temperature characteristics and bending strain characteristics. Therefore, bending strain and temperature joint compensation are required to ensure the accuracy of measured pressure, but there is no corresponding system at present. Summary of the Invention

[0005] The present invention provides a flexible array pressure sensing system for coping with local temperature changes of irregular objects, and solves the problems disclosed in the background art.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A flexible array pressure sensing system for coping with local temperature changes of irregular objects, comprising a remote non-contact image acquisition module, an acquisition control module and a terminal processing module;

[0008] The remote non-contact image acquisition module acquires the depth distribution map and temperature distribution map of the flexible pressure sensor array;

[0009] The acquisition control module acquires the resistance values output by each column and each row of the flexible pressure sensor array;

[0010] The terminal processing module calculates the bending strain compensation reference quantity of each sensing unit of the flexible pressure sensor array according to the depth distribution map; calculates the temperature compensation reference quantity of each sensing unit of the flexible pressure sensor array according to the temperature distribution map; performs pressure compensation on the flexible pressure sensor array according to the resistance value, the bending strain compensation reference quantity, the temperature compensation reference quantity, and a preset mapping relationship; wherein, the mapping relationship is the mapping relationship of calibrated pressure, temperature compensation reference quantity, bending strain compensation reference quantity, and resistance value.

[0011] The acquisition control module includes a row-column strobe switch, a voltage conversion module, an ADC chip, and a main control chip;

[0012] The input end of the row-column strobe switch is connected to the output end of the flexible pressure sensor array. The row-column strobe switch is controlled by the main control chip to strobe the sensing units in the flexible pressure sensor array;

[0013] The voltage conversion module receives the resistance analog quantity output by the strobed sensing unit and converts the resistance analog quantity into a voltage analog quantity;

[0014] The ADC chip converts the voltage analog quantity into a voltage digital signal;

[0015] The main control chip restores the voltage digital signal into a resistance value in digital quantity form.

[0016] Calculating the bending strain compensation reference quantity of each sensing unit of the flexible pressure sensor array according to the depth distribution map includes:

[0017] Segment the depth distribution map, and the segmented depth distribution map units correspond one by one to the sensing units;

[0018] Calculate the bending strain compensation reference quantity of the corresponding sensing unit according to the depth distribution map unit.

[0019] The formula for calculating the bending strain compensation reference quantity is:

[0020] ε = σ / 0.5B 2 +h

[0021] Wherein, ε is the bending strain compensation reference quantity of the sensing unit, σ is the thickness of the sensing unit, B is the strain width of the sensing unit, and h is the warping height of the sensing unit.

[0022] Calculating the temperature compensation reference quantity of each sensing unit of the flexible pressure sensor array according to the temperature distribution map includes:

[0023] Segment the temperature distribution map, and the segmented temperature distribution map units correspond one by one to the sensing units;

[0024] Calculate the temperature compensation reference quantity of the corresponding sensing unit according to the temperature distribution map unit.

[0025] The temperature compensation reference quantity is the measured temperature value of the geometric center of the temperature distribution map unit or the pixel point closest to the geometric center.

[0026] The remote non-contact image acquisition module includes a depth camera for acquiring a depth distribution map and an infrared camera for acquiring a temperature distribution map. The terminal processing module also focuses the infrared camera in this round according to the compensated pressure obtained in the previous two rounds, and determines the scanning order of the infrared camera in this round according to the temperature compensation reference quantity obtained in the previous two rounds.

[0027] Focusing the infrared camera in this round according to the compensated pressure obtained in the previous two rounds includes:

[0028] Calculating the difference in the compensated pressure of each sensing unit in the previous two rounds;

[0029] If the maximum difference is greater than the first threshold, the area composed of the sensing unit corresponding to the maximum difference and its adjacent sensing units is used as the pressure change area;

[0030] Obtaining the temperature distribution map of the pressure change area and the temperature distribution map corresponding to the preset position; wherein, the preset position is the preset rotation position of the infrared camera driving motor;

[0031] Obtaining the similarity degree between every two temperature distribution maps;

[0032] For each temperature distribution map, calculating the average value of the similarity degree between itself and other temperature distribution maps, and taking the rotation position of the infrared camera driving motor corresponding to the temperature distribution map with the minimum average value as the focusing position.

[0033] Determining the scanning order of the infrared camera in this round according to the temperature compensation reference quantity obtained in the previous two rounds includes:

[0034] If the difference in the temperature compensation reference quantity of sensing unit A in the previous two rounds is greater than the second threshold, the area composed of sensing unit A and its adjacent sensing units is used as the color temperature distribution discontinuous area;

[0035] Calculating the similarity degree between the color temperature distribution discontinuous area and other areas within a preset range around the color temperature distribution discontinuous area; wherein, the other areas include areas connected to the color temperature distribution discontinuous area and non-connected areas with a preset size;

[0036] Taking the color temperature distribution discontinuous area as the priority scanning area of the infrared camera in this round, and determining the scanning order of the infrared camera for other areas according to the similarity degree.

[0037] Determining the scanning order of the infrared camera for other areas according to the similarity degree includes:

[0038] Sort the other regions in descending order of similarity, and use the sorting result as the scanning order of the infrared camera in this round.

[0039] The beneficial effects achieved by the present invention: The present invention obtains the depth distribution map and the temperature distribution map from the remote non-contact image acquisition module, obtains the bending strain compensation reference quantity and the temperature compensation reference quantity of each unit of the array according to the depth distribution map and the temperature distribution map, and realizes the compensation of the flexible pressure sensor array according to the compensation reference quantity and the resistance value, ensuring the accuracy of the measured pressure. Description of the Drawings

[0040] Figure 1 is the system structure block diagram of the present invention;

[0041] Figure 2 is the schematic diagram of the bending strain of the sensing unit;

[0042] Figure 3 is the algorithm flowchart for the infrared camera to automatically focus on the pressure change area;

[0043] Figure 4 is the algorithm flowchart for scanning the flexible pressure sensor array in the discontinuous area of the infrared color temperature distribution. Detailed Implementation Modes

[0044] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0045] As Figure 1 shown, a flexible array pressure sensing system for coping with local temperature changes of irregular objects includes a remote non-contact image acquisition module, an acquisition control module, and a terminal processing module.

[0046] Remote non-contact image acquisition module: Acquire the depth distribution map and the temperature distribution map of the flexible pressure sensor array.

[0047] The remote non-contact image acquisition module specifically includes a depth camera for acquiring the depth distribution map and an infrared camera for acquiring the temperature distribution map. Among them, the depth camera can be the Intel lidar camera RealSense L515, and the output depth value resolution is 1mm, that is, d = 1, and the depth measurement accuracy is less than 5mm when the measurement distance is 1m; the infrared camera can be the Hikvision DS-2TA03-15SVI, its minimum imaging distance is 0.5m, the temperature measurement range is from the ambient temperature to 550°C, and the temperature measurement accuracy is ±2°C or ±2% of the reading.

[0048] Non-contact acquisition is achieved through a depth camera and an infrared camera, avoiding the problem of considering the array structure layout required for combined measurement of multiple flexible sensors, and achieving the purpose of remote measurement without changing the temperature field distribution.

[0049] Acquisition control module: Collect the resistance values output by each column and each row of the flexible pressure sensor array.

[0050] The flexible pressure sensor array is a self-made flexible pressure sensor array based on CB / CNTs (carbon black-carbon nanotube composite material), arranged in an m-row and m-column layout. Generally, m = 8, so there are m 2 flexible pressure sensor array units (hereinafter referred to as "sensing units"). The sensing units are generally square, with a side length of l2 mm, a measurement pressure range of 0 to 2 N, and m wires are led out from each row and column of the flexible pressure sensor array.

[0051] The acquisition control module includes a row-column selection switch, a voltage conversion module, an ADC chip, and a main control chip.

[0052] The input end of the row-column selection switch is connected to the output end of the flexible pressure sensor array. The row-column selection switch is controlled by the main control chip to select the sensing units in the flexible pressure sensor array. The number of input channels of the row-column selection switch can be changed according to the number of rows and columns of the array, with good system structure flexibility.

[0053] The row-column selection switch can select the CD4051B chip of Texas Instruments. This chip realizes 8-channel analog multiplexing, with an input analog voltage range of -15 to 15 V and an output digital voltage range from negative voltage V EE to power supply voltage V DD , a conduction impedance ≤ 125 Ω, and a breakage leakage current range of ±100 pA.

[0054] The row-column selection switch includes a row selection switch and a column selection switch. Both the row selection switch and the column selection switch are m-way 1-selection switches, and the connection between any output end and the output end is controlled by the high and low levels of n pins. m and n satisfy m = 2 n , realizing the row-column selection of the array.

[0055] The voltage conversion module receives the resistance analog quantity output by the selected sensing unit and converts the resistance analog quantity into a voltage analog quantity.

[0056] The voltage conversion module can select RFP-ZHII-10 of Jiangsu Changwei Microelectronics Technology Co., Ltd., with a supply voltage of 3.3 - 5 V, a conversion frequency of 1 KHz, and a conversion accuracy of ±0.01 V.

[0057] The ADC chip converts the analog voltage into a digital voltage signal. The ADS5270 chip from Texas Instruments can be selected, with a resolution of 12 bits and a maximum sampling rate of 40 MSPS.

[0058] The main control chip restores the digital voltage signal into a resistance value in digital form. The STM32F407 microcontroller from STMicroelectronics can be selected as the main control chip, with a 32-bit ARM Cortex-M4 processor core, providing 114 IO ports for controlling the row and column switch gating, controlling the ADC operation and receiving data, and providing various interfaces such as USART and SPI for communicating with the terminal processing module.

[0059] When the flexible pressure sensor array is arranged on the surface of an object with an irregular shape and local temperature change for measurement, the sensing quantity output by the sensing unit will change with the bending strain, temperature, and pressure. After the sensing quantity is transmitted to the voltage conversion module through the continuously traversed and scanned gating switch CD4051B, the voltage conversion module converts the resistance analog quantity into an analog voltage quantity, and then transmits it to the ADC chip ADS5270. After the analog-to-digital conversion is completed, a digital voltage quantity is output to the main control chip STM32F407, and the main control chip calculates the measured resistance value according to the corresponding relationship and stores it. To ensure the reliability of the array information collected by the depth camera and the infrared camera, when half of all the sensing units complete data acquisition, that is, when the gating times equal 32, the depth camera and the infrared camera are turned on to collect the depth distribution map and the temperature distribution map of the array, and transmit them to the terminal processing module. After the main control chip collects the resistance values output by all the sensing units, it packs and sends the data to the terminal processing module.

[0060] The terminal processing module calculates the bending strain compensation reference quantity for each sensing unit of the flexible pressure sensor array according to the depth distribution map; calculates the temperature compensation reference quantity for each sensing unit of the flexible pressure sensor array according to the temperature distribution map; performs pressure compensation for the flexible pressure sensor array according to the resistance value, the bending strain compensation reference quantity, the temperature compensation reference quantity, and the pre-set mapping relationship; among them, the mapping relationship is the calibrated mapping relationship of pressure, temperature compensation reference quantity, bending strain compensation reference quantity, and resistance value.

[0061] The terminal processing module can use a common computer. When calculating the bending strain compensation reference quantity, the depth distribution map is segmented into 64 regions. The segmented depth distribution map units correspond one by one to the sensing units, and the bending strain compensation reference quantity of the corresponding sensing unit is calculated according to the depth distribution map unit.

[0062] The bending strain of the sensing unit is as Figure 2As shown, B is the strain width of the sensing unit, h is the warping height of the sensing unit, σ is the thickness of the sensing unit, and L is the bending arc length of the sensing unit. Therefore, the bending strain compensation reference formula is: ε=σ / 0.5B 2 +h, where ε is the bending strain compensation reference of the sensing unit.

[0063] When the sensing unit undergoes bending strain, the arc length L of the sensing unit remains unchanged. Combined with the relative positions of the pixels in the corresponding area of the sensing unit collected by the depth camera, the arc length position of the sensing unit can be calculated. The projection of its endpoint is B, and the y value of the midpoint is h. Substituting it into the above formula, the reference amount of the bending strain compensation of the sensing unit is obtained.

[0064] When calculating the temperature compensation reference, the temperature distribution map is similarly segmented. The segmented temperature distribution map units correspond one-to-one to the sensing units. The temperature compensation reference is calculated for each sensing unit based on the temperature distribution map unit. The temperature compensation reference is the measured temperature at the geometric center of the temperature distribution map unit or the pixel closest to the geometric center.

[0065] Considering the uneven distribution of pressure changes in the flexible pressure sensor array, it is necessary to prioritize scanning areas with drastic pressure changes. This requires the infrared camera to quickly and accurately focus on the pressure change area. To achieve this goal, the terminal processing module also focuses the infrared camera in this round based on the compensated pressure obtained in the previous two rounds. The specific process is as follows: Figure 3 As shown:

[0066] 1) Calculate the difference in pressure between the first two rounds of each sensor unit after compensation;

[0067] 2) If the maximum difference is greater than the first threshold, the area consisting of the sensing unit corresponding to the maximum difference and its adjacent sensing units is regarded as the pressure change area;

[0068] 3) obtaining a temperature distribution map of the pressure change region and obtaining a temperature distribution map corresponding to a preset position; wherein the preset position is a preset rotation position of the infrared camera drive motor;

[0069] 4) Using the Bhattacharyya coefficient algorithm, obtain the pairwise similarity of the temperature distribution graphs;

[0070] 5) For each temperature distribution map, calculate the average of its similarity with other temperature distribution maps, and use the rotation position of the infrared camera drive motor corresponding to the temperature distribution map with the minimum average as the focus position.

[0071] Considering the situation of local temperature change in the array, the method of polling and scanning the sensing units of the flexible pressure sensor array has the problem that it cannot focus on the temperature change part of the array. To solve this problem, the terminal processing module also determines the scanning order of the infrared camera in this round according to the temperature compensation reference quantities obtained in the previous two rounds. The specific process is as Figure 3 shown:

[0072] S1) If the difference in the temperature compensation reference quantities of the sensing unit A in the previous two rounds is greater than the second threshold, the area composed of the sensing unit A and its adjacent sensing units is regarded as the area with discontinuous color temperature distribution;

[0073] S2) Calculate the similarity between the area with discontinuous color temperature distribution and other areas within a preset range around the area with discontinuous color temperature distribution; among them, the other areas include the areas connected to the area with discontinuous color temperature distribution and the non-connected areas with a preset size;

[0074] S3) The area with discontinuous color temperature distribution is used as the priority scanning area of the infrared camera in this round. Sort the other areas in descending order of similarity, and use the sorting result as the scanning order of the infrared camera in this round.

[0075] Taking the sensing unit in the second row and second column of the pressure sensor array as an example, a spherical wooden block with a diameter of 10 mm is arranged under this sensing unit to form a bulge, and the temperature of this sensing unit is raised to 70 °C using the DB-3EFS constant temperature heater of Lichen Technology. The output resistance value is measured to be 15.37 kΩ by the bench multimeter DMM6500 of Keithley Instruments. The bending strain compensation reference quantity of this sensing unit is calculated to be 0.742% and the temperature compensation reference quantity is 69.7 °C in the terminal processing module. Substitute the compensation reference quantity and the measured resistance value into the mapping relationship table to obtain a pressure value of 0.0063 N, and the reference error is 0.315%, and the pressure compensation is effective.

[0076] The present invention obtains the depth distribution map and temperature distribution map from the remote non-contact image acquisition module, and obtains the bending strain compensation reference quantity and temperature compensation reference quantity of each unit of the array according to the depth distribution map and temperature distribution map. According to the compensation reference quantity and resistance value, the compensation of the flexible pressure sensor array is realized, ensuring the accuracy of the measured pressure.

[0077] The present invention collects the depth distribution information, temperature distribution information, and resistance value distribution information of the array. On this basis, the algorithms for obtaining the temperature and bending strain compensation reference quantities of the pressure sensor array and the compensation algorithm for restoring the collected pressure are realized. These two algorithms comprehensively consider the invocation of historical or empirical data, and support the flexible array pressure sensing system based on different types of flexible substrate materials in multiple aspects, realizing the accurate compensation of the pressure sensor array, and further increasing the applicability of the sensing system.

[0078] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A flexible array pressure sensing system for coping with local temperature changes of irregular objects, characterized in that It includes a remote non-contact image acquisition module, an acquisition control module, and a terminal processing module; The remote non-contact image acquisition module acquires the depth distribution map and the temperature distribution map of the flexible pressure sensor array; The acquisition control module acquires the resistance values output by each column and each row of the flexible pressure sensor array; The terminal processing module calculates the bending strain compensation reference quantity of each sensing unit of the flexible pressure sensor array according to the depth distribution map; Calculates the temperature compensation reference quantity of each sensing unit of the flexible pressure sensor array according to the temperature distribution map; Performs pressure compensation on the flexible pressure sensor array according to the resistance value, the bending strain compensation reference quantity, the temperature compensation reference quantity, and a pre-set mapping relationship; wherein, the mapping relationship is the mapping relationship of calibrated pressure, temperature compensation reference quantity, bending strain compensation reference quantity, and resistance value.

2. The flexible array pressure sensing system for coping with local temperature change of irregular objects according to claim 1, wherein The acquisition control module includes a row-column strobe switch, a voltage conversion module, an ADC chip, and a main control chip; The input end of the row-column strobe switch is connected to the output end of the flexible pressure sensor array. The row-column strobe switch is controlled by the main control chip to strobe the sensing units in the flexible pressure sensor array; The voltage conversion module receives the resistance analog quantity output by the selected sensing unit and converts the resistance analog quantity into a voltage analog quantity; The ADC chip converts the voltage analog quantity into a voltage digital signal; The main control chip restores the voltage digital signal into a resistance value in digital quantity form.

3. The flexible array pressure sensing system for coping with local temperature change of irregular objects according to claim 1, characterized in that Calculating the bending strain compensation reference quantity of each sensing unit of the flexible pressure sensor array according to the depth distribution map includes: Segment the depth distribution map, and the segmented depth distribution map units correspond one-to-one with the sensing units; Calculate the bending strain compensation reference quantity of the corresponding sensing unit according to the depth distribution map unit.

4. A flexible array pressure sensing system for coping with local temperature changes of irregular objects according to claim 3, characterized in that The formula for calculating the bending strain compensation reference quantity is: Among them, is the bending strain compensation reference quantity of the sensing unit, is the thickness of the sensing unit, B is the strain width of the sensing unit, h is the warping height of the sensing unit.

5. The flexible array pressure sensing system for coping with local temperature change of irregular objects according to claim 1, wherein, Calculating the temperature compensation reference quantity of each sensing unit of the flexible pressure sensor array according to the temperature distribution map includes: Segment the temperature distribution map, and the segmented temperature distribution map units correspond one-to-one with the sensing units; Calculate the temperature compensation reference quantity of the corresponding sensing unit according to the temperature distribution map unit.

6. The flexible array pressure sensing system for coping with local temperature change of irregular objects according to claim 5, wherein The temperature compensation reference quantity is the measured temperature value of the geometric center of the temperature distribution map unit or the pixel point closest to the geometric center.

7. A flexible array pressure sensing system for coping with local temperature changes of irregular objects according to claim 1, characterized in that The remote non-contact image acquisition module includes a depth camera for acquiring the depth distribution map and an infrared camera for acquiring the temperature distribution map. The terminal processing module also focuses the infrared camera for this round according to the pressure compensated in the previous two rounds, and determines the scanning order of the infrared camera for this round according to the temperature compensation reference quantity obtained in the previous two rounds.

8. The flexible array pressure sensing system for coping with local temperature change of irregular objects according to claim 7, characterized in that, Focusing the infrared camera for this round according to the pressure compensated in the previous two rounds includes: Calculate the difference in the pressure compensated by each sensing unit in the previous two rounds; If the maximum difference is greater than the first threshold, then the area composed of the sensing unit corresponding to the maximum difference and its adjacent sensing units is used as the pressure change area; Obtain the temperature distribution map of the pressure change area, and obtain the temperature distribution map corresponding to the preset position; wherein, the preset position is the preset rotation position of the infrared camera driving motor; Obtain the pairwise similarity degree of the temperature distribution maps; For each temperature distribution map, calculate the mean value of the similarity degree between itself and other temperature distribution maps, and use the rotation position of the infrared camera driving motor corresponding to the temperature distribution map with the minimum mean value as the focusing position.

9. A flexible array pressure sensing system for coping with local temperature changes of irregular objects according to claim 7, characterized in that, Based on the temperature compensation reference quantities obtained in the previous two rounds, determine the scanning order of the infrared camera in this round, including: If the difference in the temperature compensation reference quantities of the sensing unit A in the previous two rounds is greater than the second threshold, then the area composed of the sensing unit A and its adjacent sensing units is regarded as the area with discontinuous color temperature distribution; Within a preset range around the area with discontinuous color temperature distribution, calculate the similarity degree between the area with discontinuous color temperature distribution and other areas; among them, the other areas include the areas connected to the area with discontinuous color temperature distribution and the non-connected areas with a preset size; Regard the area with discontinuous color temperature distribution as the area to be preferentially scanned by the infrared camera in this round, and determine the scanning order of the infrared camera for other areas according to the similarity degree.

10. The flexible array pressure sensing system for coping with local temperature change of irregular objects according to claim 9, wherein, Determine the scanning order of the infrared camera for other areas according to the similarity degree, including: Sort the other areas in descending order of similarity degree, and use the sorting result as the scanning order of the infrared camera in this round.

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