A calibration device and method for a flexible pressure sensor array

Abstract

The application discloses a kind of calibration device and method for flexible pressure sensor array.The calibration device of the application includes motion control module, positioning module, pressure exerting module and signal acquisition module;Motion control module drives positioning module and pressure exerting module, positioning module guides the pressurizing module to move to the position above target sensor unit, and the pressurizing module applies force linearly increasing with time to sensor unit.Signal acquisition module obtains the accurate value of applied pressure and the response value of sensor unit under corresponding pressure, and is transmitted to computer through corresponding circuit, and is calibrated by calibration software.The calibration method of the application includes two parts of pressure value extraction and calibration, obtains the pressure value applied to sensor unit and the sensor output signal corresponding thereto, and obtains the pressure response curve of each sensor unit.The application solves the problem of independent pressure calibration for each sensor unit in high-precision sensor array, and improves calibration efficiency and calibration accuracy.

Description

Technical Field

[0001] This invention relates to the field of sensor calibration, and more specifically to a calibration device and method for flexible pressure sensor arrays. Background Technology

[0002] Flexible pressure sensor arrays, composed of multiple flexible pressure sensor units, are capable of detecting pressure distribution and are widely used in wearable electronic devices, electronic skin, human-computer interaction, and health monitoring. However, due to limitations in materials and manufacturing processes, current flexible pressure sensor arrays cannot guarantee that the pressure sensitivity and pressure characteristic curves of each sensing unit are completely consistent. Since many applications require the use of flexible pressure sensor arrays to obtain accurate pressure distribution, the calibration of the sensor array is crucial for product quality control and effective application.

[0003] Flexible pressure sensor arrays often contain a large number of sensor units. Manually calibrating each sensor unit individually is time-consuming and impractical. Existing automatic calibration methods typically use pneumatic or hydraulic pressure to apply uniform pressure to all sensor units in the array and obtain the characteristic curve of each unit. These methods often require the size and shape of the sensor array to match the device dimensions, resulting in poor versatility. Furthermore, to ensure equal force on each sensor unit, these methods require uniform force across the entire sensing area, a flat pressurization module, and a perfect, gapless fit between the sensor array and the bottom surface. These requirements are often difficult to guarantee in practice, leading to errors in the final calibration results.

[0004] Therefore, an automated calibration method is needed to apply pressure to each pressure sensor unit individually and obtain its characteristic curve, thereby achieving accurate calibration of the entire flexible pressure sensor array. Summary of the Invention

[0005] To address the shortcomings of existing flexible pressure sensor array calibration methods, which fail to ensure uniform force distribution across all sensor units and require time-consuming manual application of force to individual units, this invention proposes a calibration device and method for flexible pressure sensor arrays. The calibration device automatically applies varying magnitudes of force to each sensor unit in the array using a stepper motor and a three-axis guide rail, while simultaneously acquiring the response values ​​of the sensor units and the precise applied pressure values. The calibration method extracts the corresponding response values ​​of each pressure sensor unit under different pressure magnitudes, thereby obtaining a pressure response curve or response table for the sensor unit.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a calibration device for a flexible pressure sensor array, the device comprising: a motion control module, a positioning module, a pressure application module, and a signal acquisition module;

[0007] The motion control module consists of an STM32 microcontroller system board and a stepper motor driver, and is used to control the motion of the positioning module and the pressure application module.

[0008] The positioning module includes a horizontal front-to-back moving guide rail, a horizontal moving guide rail, and a stepper motor. The horizontal moving guide rail is mounted on the front-to-back moving guide rail. Both the front-to-back moving guide rail and the horizontal moving guide rail are equipped with stepper motors. The stepper motors are connected to stepper motor drivers and are used to adjust the position of the pressure application module on the horizontal plane.

[0009] The pressure application module includes a stepper motor, a tension / compression sensor, a force loading head, a photoelectric switch, and a longitudinal moving guide rail. The stepper motor, tension / compression sensor, and photoelectric switch are mounted on the longitudinal moving guide rail. The force loading head is installed below the tension / compression sensor and is used to apply force to the sensor unit. The tension / compression sensor determines the accurate value of the force.

[0010] The signal acquisition module includes a tension / compression sensor acquisition circuit and a sensor array acquisition circuit, which are used to acquire the precise value of the applied pressure and the response value of the flexible sensor unit, and transmit them to the computer.

[0011] Furthermore, the two front and rear moving guide rails of the positioning module are placed in parallel, and the left and right moving guide rails are installed above the front and rear moving guide rails. The front and rear moving guide rails and the stepper motor are used to drive the left and right moving guide rails to move forward and backward, and the left and right moving guide rails and the stepper motor are used to drive the longitudinal moving guide rail installed on the left and right moving guide rails to move left and right.

[0012] Furthermore, the longitudinal moving guide rail and the stepper motor drive the movement of the tension / compression sensor and the force loading head mounted on the longitudinal moving guide rail; the upper end of the tension / compression sensor is connected to the longitudinal moving guide rail through an L-shaped plate.

[0013] Furthermore, the force loading head is made of an elastic material, and its compressive stress is linearly related to its compression length. By changing the compression length of the force loading head, the magnitude of the applied pressure can be controlled, and the compressive stress of the force loading head can be transmitted to the tension and compression sensor.

[0014] Furthermore, the photoelectric switch is mounted on the longitudinal moving guide rail to limit the movement range of the tension / compression sensor and the force loading head. When the tension / compression sensor moves on the longitudinal moving guide rail to trigger the photoelectric switch, the photoelectric switch is turned on and feeds the signal back to the microcontroller system board of the motion control module, stopping the longitudinal movement of the pressure application module.

[0015] According to a second aspect of this specification, a calibration method for a flexible pressure sensor array is provided, characterized by comprising the following steps:

[0016] Step 1. Move the pressure application module to directly above the first sensor unit of the flexible pressure sensor array via the positioning module to zero the tension and compression sensors;

[0017] Step 2. The pressure application module sequentially applies a continuous force that increases linearly with time to each sensor array unit, while the signal acquisition module acquires the output values ​​of the tension and compression sensors and the response values ​​of all units in the sensor array and transmits them to the computer.

[0018] Step 3. Extract the maximum response value signal of all units in the sensor array, align the output value signal of the tension and compression sensors and the maximum response value signal of the sensor array in the time domain, and extract the tension and compression sensor signal and sensor array signal corresponding to each sensor unit when the pressure application module applies pressure;

[0019] Step 4. For the tensile and compressive sensor signals and sensor array signals of each sensor unit, select multiple sampling points at uniform time intervals and plot the relationship curve.

[0020] Furthermore, step 2 specifically includes the following sub-steps:

[0021] Step 2-1. Set the maximum value h of the downward displacement of the pressure application module. press The system begins collecting output values ​​from the tension and compression sensors and response values ​​from the sensor array.

[0022] Step 2-2. The pressure application module rises rapidly along the longitudinal moving guide rail to trigger the photoelectric switch;

[0023] Steps 2-3: The pressure application module is quickly pressed down onto the contact sensor unit;

[0024] Steps 2-4. The pressure application module presses down at a constant speed h. press ,pause;

[0025] Steps 2-5. The pressure application module rises rapidly to trigger the photoelectric switch, and is then positioned above the next sensor unit via the positioning module;

[0026] Step 2-6. Repeat steps 2-3, 2-4, and 2-5 until all sensor units in the array have been pressurized;

[0027] Steps 2-7. End the acquisition of tensile and compressive sensor output values ​​and sensor array response values.

[0028] Furthermore, step 3 specifically includes the following sub-steps:

[0029] Step 3-1. Define the threshold th. A Search for each tension / compression sensor signal that increases from zero by more than th AThe position is used as the starting position for pressurizing each sensor unit, posA. Start The location of all peak points exceeding the threshold in the search signal is used as the end position posA for pressurizing each sensor unit. End ; Determine the segmentation in the tension / compression sensor signal when pressurizing each sensor unit [posA] Start ,posA End ];

[0030] Step 3-2. Define the threshold th. B The search sensor array's response signal contains all values ​​that increase from zero to more than th. B The position, posB, serves as the starting point for pressure on each sensor unit. start The location of all peak points exceeding the threshold in the search signal is used as the end position posB of the pressure applied to each sensor unit. End ; Determine the segment in the maximum response signal of the sensor array representing each sensor unit under pressure [posB] Start ,posB End ];

[0031] Step 3-3. Based on the signal segments obtained in Steps 3-1 and 3-2, take N sampling points with equal time intervals for each segment, and obtain the value of each sampling point in each segment, that is, the N pressure values ​​ValueA received by each sensor unit. n | 1≤n≤N and N read values ​​ValueB n | 1≤n≤N ;

[0032] Step 3-4. Based on the time values ​​of the sampling points, adjust the pressure value ValueA from Step 3-3. n | 1≤n≤N and read the value ValueB n | 1≤n≤N Perform point-by-point matching.

[0033] Furthermore, in step 4:

[0034] If the relationship curve can be fitted to a common function form, save the calibration file, including the output values ​​of the tension and compression sensors, the maximum response value of the sensor array, the calibration coefficients, and the fitting function; otherwise, perform calibration using a lookup table method and save the calibration file, including the output values ​​of the tension and compression sensors and the maximum response value of the sensor array.

[0035] The beneficial effects of this invention are as follows: This invention designs a calibration device and method for flexible pressure sensor arrays. The device can automatically apply different pressures to each sensor unit in the array and acquire the sensor unit's response value. The method can automatically calibrate the pressure response characteristics of each sensor unit based on the applied pressure value and the acquired response value. This method achieves automatic calibration of flexible pressure sensor arrays, ensuring the consistency and accuracy of the sensor array output, and meeting the needs of environmental monitoring, medical health, and other fields for obtaining accurate values ​​from sensor arrays. This device avoids the problem of inconsistent pressure application within a range that existing methods cannot guarantee, and uses point-by-point calibration to ensure the measurement accuracy of the flexible pressure sensor array. The device has a simple structure, is easy to use, and achieves automatic calibration, saving the time spent on manual calibration. Attached Figure Description

[0036] Figure 1 This is a block diagram of the calibration device of the present invention;

[0037] Figure 2 This is a structural diagram of the calibration device of the present invention;

[0038] Figure 3 This is a flowchart of the calibration method of the present invention;

[0039] Figure 4 This is a graph showing the relationship between the sensor units of this invention;

[0040] Figure 5 This is a probability density distribution diagram of the fitting coefficients of the relationship curve of this invention.

[0041] Among them, 1. Front and rear moving guide rail, 2. Left and right moving guide rail, 3. Longitudinal moving guide rail, 4. Connecting rod, 5. Stepper motor, 6. Photoelectric switch, 7. L-shaped plate, 8. Tension and compression sensor, 9. Force loading head, 10. Flexible pressure sensor array, 11. Tension and compression sensor acquisition circuit, 12. Sensor array acquisition circuit, 13. Computer. Detailed Implementation

[0042] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0043] according to Figure 1 As shown, a calibration device for a flexible pressure sensor array 10 includes a motion control module, a positioning module, a pressure application module, and a signal acquisition module.

[0044] The motion control module includes an STM32 microcontroller system board and a stepper motor driver. The STM32 microcontroller system board outputs control signals to the stepper motor driver, which controls the direction and speed of the stepper motor to control the movement of the positioning module and the pressurization module.

[0045] The positioning module includes a horizontal front-to-back moving guide rail 1, a horizontal moving guide rail 2, and a stepper motor 5, which are used to adjust the position of the pressure application module on the horizontal plane.

[0046] The pressure application module includes a longitudinal moving guide rail 3 and a stepper motor 5, a tension / compression sensor 8, a force loading head 9 and a photoelectric switch 6, which are used to apply forces of different magnitudes to the sensor unit;

[0047] The signal acquisition module includes a tension / compression sensor acquisition circuit 11 and a sensor acquisition circuit 12, which are used to acquire the precise value of the applied pressure and the response value of the flexible sensor unit, and transmit them to the computer 13.

[0048] according to Figure 2 As shown, in this embodiment, the positioning module includes two front-to-back moving guide rails 1, one left-to-right moving guide rail 2, and a stepper motor 5 on a horizontal plane. The two front-to-back moving guide rails are placed in parallel and connected by a connecting rod 4. The left-to-right moving guide rail is installed above the front-to-back moving guide rail. The front-to-back moving guide rail and the stepper motor are used to drive the movement of the left-to-right moving guide rail. The left-to-right moving guide rail and the stepper motor are used to drive the movement of the pressure module installed on the left-to-right moving guide rail.

[0049] The pressure application module includes a longitudinal moving guide rail 3, a stepper motor, a tension / compression sensor 8, a force loading head 9, and a photoelectric switch 6. The longitudinal moving guide rail 3 and the stepper motor drive the movement of the tension / compression sensor 8 and the force loading head 9, which are mounted on the longitudinal moving guide rail. The tension / compression sensor 8 has external threads at both ends, and its upper end is connected to the longitudinal moving guide rail 3 through an L-shaped plate 7. The force loading head 9 is made of an elastic material, and its compressive stress is linearly related to its compression length. Changing the compression length of the force loading head 9 controls the applied pressure. The upper end of the force loading head 9 has an internal thread and is connected to the lower end of the tension / compression sensor 8, transmitting the compressive stress of the force loading head 9 to the tension / compression sensor 8. The photoelectric switch 6 is used to limit the movement range of the tension / compression sensor 8 and the force loading head 9. When the tension / compression sensor 8 moves on the longitudinal moving guide rail 3 to the point where the photoelectric switch is triggered, the photoelectric switch is turned on and feeds a signal back to the microcontroller system board of the motion control module, stopping the longitudinal movement of the pressure application module.

[0050] The acquisition module includes a tension / compression sensor acquisition circuit 11 and a sensor array acquisition circuit 12. The tension / compression sensor acquisition circuit 11 is a 485 digital module and peripheral circuits that convert the tension / compression sensor signals into digital signals and input them into a computer 13. The sensor array acquisition circuit 12 includes a power supply circuit, a control circuit, an analog-to-digital converter circuit, a multiplexer, and a zero-compensation circuit, employing a row scanning sampling method. The power supply circuit meets the power requirements of each module in the acquisition circuit. The control circuit is responsible for signal reading / writing and multiplexer control. The analog-to-digital converter circuit uses a 12-bit resolution analog-to-digital converter to convert analog signals into digital signals. The multiplexer is responsible for row and column selection. The zero-compensation circuit uses an operational amplifier circuit to zero the potential difference between two segments of an unselected column, thereby eliminating the inherent crosstalk noise of the array structure.

[0051] According to the appendix Figure 3 As shown, the calibration method flow in this embodiment is as follows:

[0052] Step 1. Move the pressure application module directly above the first sensor unit of the flexible pressure sensor array 10 to zero the tension and compression sensors;

[0053] Step 2. The pressure application module sequentially applies a continuous, linearly increasing force over time to each sensor array unit. Simultaneously, the signal acquisition module acquires the output values ​​of the tension and compression sensors and the response values ​​of all units in the sensor array and transmits them to the computer 13. Detailed steps are as follows:

[0054] Step 2-1. Set the maximum value h of the downward displacement of the pressure application module. press The system begins collecting output values ​​from the tension and compression sensors and response values ​​from the sensor array.

[0055] Step 2-2. The pressure application module rises rapidly along the longitudinal moving guide rail to trigger the photoelectric switch;

[0056] Steps 2-3: The pressure application module is quickly pressed down onto the contact sensor unit;

[0057] Steps 2-4. The pressure application module presses down at a constant speed h. press ,pause;

[0058] Steps 2-5. The pressure application module rises rapidly to trigger the photoelectric switch and moves above the next sensor unit via the horizontal guide rail;

[0059] Step 2-6. Repeat steps 2-3, 2-4, and 2-5 until all sensor units in the array have been pressurized;

[0060] Steps 2-7. End the acquisition of tensile and compressive sensor output values ​​and sensor array response values.

[0061] Step 3. Extract the maximum value of the response signal of all units in the sensor array, align the output signal of the tension / compression sensor and the maximum response signal of the sensor array in the time domain, and extract the tension / compression sensor signal and sensor array signal corresponding to each sensor unit when the pressure application module applies pressure; the specific steps are as follows.

[0062] Step 3-1. Define the threshold th. A For tension and compression sensor signals, search for all signals that increase from zero to more than th. A The position is used as the starting position for pressurizing each sensor unit, posA. Start The location of all peak points exceeding the threshold in the search signal is used as the end position posA for pressurizing each sensor unit. End ; Determine the segmentation in the tension / compression sensor signal when pressurizing each sensor unit [posA] Start ,posA End ];

[0063] Step 3-2. Define the threshold th. B For the maximum response value signal of the sensor array, search for all signals in the signal that increase from zero to more than th. B The position, posB, serves as the starting point for pressure on each sensor unit. Start The location of all peak points exceeding the threshold in the search signal is used as the end position posB of the pressure applied to each sensor unit. End ; Determine the segment in the maximum response signal of the sensor array representing each sensor unit under pressure [posB] Start ,posB End ];

[0064] Step 3-3. Based on the signal segments obtained in Steps 3-1 and 3-2, take N sampling points with equal time intervals for each segment, and obtain the value of each sampling point in each segment, that is, the N pressure values ​​ValueA received by each sensor unit. n | 1≤n≤N and N read values ​​ValueB n | 1≤n≤N ;

[0065] Step 3-4. Based on the time values ​​of the sampling points, adjust the pressure value ValueA from Step 3-3. n | 1≤n≤N and read the value ValueB n | 1≤n≤N Perform point-by-point matching.

[0066] Step 4. For each sensor unit's tension / compression sensor signal and sensor array signal, select multiple sampling points at uniform time intervals and plot the relationship curve. If the relationship curve can be fitted to a common function form such as a linear function, exponential function, logarithmic function, or power function, save the calibration file, including the output value of the tension / compression sensor, the maximum response value of the sensor array, calibration coefficients, and the fitting function; otherwise, perform calibration using a lookup table method and save the calibration file, including the output value of the tension / compression sensor and the maximum response value of the sensor array.

[0067] To verify the effectiveness of the calibration device and method proposed in this invention, an embodiment of this invention uses the device and method to calibrate a 32×32 flexible pressure sensor array 10. (See attached...) Figure 4 The pressure-response curves of some sensor units shown are all close to bivariate linear functions, but the curves of each unit are different. Therefore, it is necessary to calibrate each sensor unit individually. This invention provides an independent pressure calibration curve for each sensor unit, which improves calibration efficiency and calibration accuracy.

[0068] like Figure 5 The graph shown is a probability density fitting curve of slope k versus intercept b obtained by linear fitting of the relationship curve for each sensor unit. The horizontal axis represents the normalized value of the parameter, and the vertical axis represents the probability density function value corresponding to that value. It can be seen that the distributions of slope k and intercept b are approximately normal distributions and have randomness. Through calibration, the differences between sensor units can be eliminated.

[0069] The specific embodiments described above illustrate the technical solution and beneficial effects of the present invention in detail. It should be understood that the above description is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calibrating a flexible pressure sensor array, characterized by, The application is based on a calibration device, which comprises a motion control module, a positioning module, a pressure applying module and a signal acquisition module. The motion control module is composed of a single-chip system board and a step motor driver, which is used to control the motion of the positioning module and the pressure applying module. The positioning module comprises front and back moving rails, left and right moving rails and step motors. The pressure applying module comprises a step motor, a tensile pressure sensor, a force loading head, a photoelectric switch and a longitudinal moving rail. The signal acquisition module comprises a tensile pressure sensor acquisition circuit and a sensor array acquisition circuit, which are used to acquire the accurate value of the applied pressure and the response value of the flexible sensor unit and transmit them to a computer. The two front and back moving rails are parallelly placed, and the left and right moving rails are installed above the front and back moving rails. The front and back moving rails and the step motors are used to drive the front and back movement of the left and right moving rails. The left and right moving rails and the step motors are used to drive the left and right movement of the longitudinal moving rail installed on the left and right moving rail. The longitudinal moving rail and the step motor drive the movement of the tensile pressure sensor and the force loading head installed on the longitudinal moving rail. The force loading head is made of elastic material, and its compressive stress and compression length are in linear relationship. The photoelectric switch is installed on the longitudinal moving rail, which is used to limit the movement range of the tensile pressure sensor and the force loading head. The method comprises the following steps: Step 1. Move the pressure applying module to the top of the first sensor unit of the flexible pressure sensor array through the positioning module, and calibrate the zero tensile pressure sensor. Step 2. The pressure applying module applies a continuous force with a linear increase from small to large over time to each sensor unit in turn, while the signal acquisition module acquires the output value of the tensile pressure sensor and the response value of all units of the sensor array and transmits them to the computer. Step 3. Extract the maximum response value signal of all units of the sensor array, time-domain align the tensile pressure sensor output value signal and the maximum response value signal of the sensor array, and intercept the corresponding tensile pressure sensor signal and sensor array signal when the pressure applying module applies pressure to each sensor unit. Step 4. The tensile and compressive force sensor signals of each sensor unit and the sensor array signals are selected at multiple sampling points at uniform time intervals, a relationship curve is drawn, and calibration is completed; The step 2 specifically comprises the following sub-steps: Step 2-1. Set the maximum value of the down displacement of the pressure applying module Start to collect the output value of the tension-compression force sensor and the response value of the sensor array; Step 2-2. The pressure applying module is quickly raised to trigger the photoelectric switch through the longitudinal movement guide rail; Step 2-3. The pressure applying module is quickly pressed to contact the sensor unit; Step 2-4. Pressure application module uniform speed down , pause; Step 2-5. The pressure applying module is quickly raised to trigger the photoelectric switch, and is displaced to above the next sensor unit through the positioning module; Step 2-6. Steps 2-3, 2-4 and 2-5 are repeated until all the sensor units in the array are subjected to the pressure applying operation; Step 2-7. The collection of the tensile and compressive force sensor output values and the sensor array response values is ended; The step 3 specifically comprises the following sub-steps: Step 3-1. Define the increase threshold Search for the position in each tensile-compressive force sensor signal where the increase from zero exceeds as the start position of the pressurization of each sensor unit Search for the position of all peak points in the signal that exceed the threshold as the end position of the pressurization of each sensor unit Determine the segment that represents the pressurization of each sensor unit in the tensile-compressive force sensor signal ; Step 3-2. Define the increase threshold Search for all positions in the response value signal of the sensor array where the increase from zero exceeds the threshold value as the start of the pressure on each sensor element Search for all positions in the signal where the peak value exceeds the threshold value as the end of the pressure on each sensor element Determine the segment in the maximum response value signal of the sensor array that represents the pressure on each sensor element ; Step 3-3. Based on the signal segments obtained in Step 3-1 and Step 3-2, take N sampling points of equal time intervals for each segment, and obtain the value of each sampling point of each segment, i.e. N pressure values received by each sensor unit and N reading values ; Step 3-4. The pressure values in step 3-3 are point- by-point matched according to the time values of the sampling points and the read values .

2. The method for calibrating a flexible pressure sensor array of claim 1, wherein, In the step 4: If the relationship curve can be fitted into a common function form, a calibration file is saved, including the output value of the tensile and compressive force sensor, the maximum response value of the sensor array, the calibration coefficient and the fitted function; otherwise, the calibration is performed through a table lookup method, and a calibration file is saved, including the output value of the tensile and compressive force sensor and the maximum response value of the sensor array.

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