STM32-based silicon resonance sensor calibration system and method

Abstract

The invention belongs to the field of aviation electromechanical atmosphere data systems, and relates to a silicon resonance sensor calibration system and method based on STM32. Comprising a PC (Personal Computer), an STM32 acquisition circuit module, a frequency meter / digital multimeter, a pressure controller assembly, a power supply, an RS422 serial port and an incubator, the PC computer is connected with an RS422 communication interface of the STM32 acquisition circuit module through an RS422 serial port; the RS422 is powered by a power supply; the N paths of silicon resonance sensors are connected with a multiplexing SPI bus of the STM32 acquisition circuit module; the N paths of silicon resonance sensors are also connected with a frequency acquisition adapter of the STM32 acquisition circuit module, the other end of the frequency acquisition adapter is connected with a frequency meter / digital multimeter, and the frequency meter / digital multimeter is connected with a PC (Personal Computer); the pressure interfaces of the N paths of silicon resonance sensors are connected with the pressure controller assembly; the N paths of silicon resonance sensors are connected with the STM32 acquisition circuit module and then are placed in the incubator; and the PC is connected with the pressure controller assembly through a GPIB (General Purpose Interface Bus) port.

Description

Technical Field

[0001] The invention belongs to the field of aviation electromechanical air data systems, and relates to a calibration system and method for silicon resonant sensors based on STM32. Background Art

[0002] After the air data system sensor collects the measured static pressure of the aircraft, it outputs the measured static pressure to the flight control system for flight control rate calculation.

[0003] The core sensor for measuring static pressure is a silicon resonant pressure sensor. To enable the sensor to output high-precision pressure data within the full temperature range and the entire pressure range, temperature calibration of the silicon resonant pressure sensor is required. The output form of this sensor is a pressure frequency signal and a pressure temperature signal. The calibration process requires repeated measurement of the output data of the sensor at different pressure test points under different temperature points. According to the test data of the sensor at each temperature calibration point and pressure calibration point, the unique calibration coefficient matrix of the sensor is calculated. Finally, the actual pressure value measured by the sensor is calculated using the pressure frequency signal, pressure temperature signal, and calibration coefficient matrix output by the sensor. Therefore, this calibration process involves a large amount of testing work. When multiple silicon resonant sensors need to be calibrated, the test workload will increase exponentially, the calibration period is long, the efficiency is low, and a large amount of human and material resources will be consumed. Therefore, it is necessary to invent a calibration system and method for silicon resonant sensors based on STM32 to improve the efficiency of silicon resonant sensor calibration testing. Summary of the Invention

[0004] Object of the Invention: To provide a calibration system and method for silicon resonant sensors based on STM32 to solve the problems of long test period and low efficiency of silicon resonant sensors.

[0005] Technical Solution of the Invention:

[0006] A calibration system for silicon resonant sensors based on STM32 includes: a PC computer, an STM32 acquisition circuit module, a frequency meter / digital multimeter, a pressure controller assembly, a power supply, an RS422 serial converter, and a temperature chamber;

[0007] The PC computer is connected to the RS422 communication interface of the STM32 acquisition circuit module through the RS422 serial converter to receive and parse the pressure frequency and pressure temperature output by N silicon resonant sensors; the RS422 is powered by the power supply;

[0008] The N silicon resonant sensors are connected to the multiplexed SPI bus of the STM32 acquisition circuit module, and the STM32 acquisition circuit module reads the pressure temperature output by the N silicon resonant sensors using the SPI bus;

[0009] The N-channel silicon resonant sensor is also connected to the frequency acquisition adapter of the STM32 acquisition circuit module. The other end of the frequency acquisition adapter is connected to a frequency meter / digital multimeter, which is connected to a PC computer. The PC computer controls the frequency meter / digital multimeter through the USB to sequentially read the pressure frequencies output by the N-channel silicon resonant sensor;

[0010] The pressure interfaces of the N-channel silicon resonant sensors are connected to the pressure controller assembly;

[0011] After the N-channel silicon resonant sensors are connected to the STM32 acquisition circuit module, they are placed in an incubator;

[0012] The PC computer is connected to the pressure controller assembly through the GPIB port and automatically controls the pressure controller assembly to output different pressure test points through a preset program.

[0013] Further, the pressure controller assembly includes a pressure controller, a vacuum pump, and a gas source;

[0014] The vacuum pump provides a negative pressure source for the pressure controller, and the gas cylinder provides a positive pressure source for the pressure controller.

[0015] Further, the STM32 acquisition circuit module is connected to the N-channel silicon resonant sensors through the built-in SPI3 communication module; one SPI3_MISO IO port is multiplexed for N channels to collect pressure and temperature data, one SPI3_MOSI IO port is multiplexed for N channels to control the N-channel silicon resonant sensors, one SPI3_CLK IO port is multiplexed for N channels to provide a clock, and N SPI3_CS chip select IO ports are respectively connected to the corresponding N-channel silicon resonant sensors to provide chip select signals. The main program of the STM32 acquisition circuit module sequentially reads the pressure and temperature signals output by the N-channel silicon resonant sensors through the SPI3 bus every 500 ms and packs the N-channel temperature signals and sends them to the PC computer to realize the simultaneous acquisition of the pressure and temperature signals of the N-channel silicon resonant sensors.

[0016] Further, the frequency acquisition adapter is N-channel.

[0017] A calibration method for a silicon resonant sensor based on STM32 is implemented based on the described system, and the process is as follows:

[0018] Step 1: Connect the silicon resonant sensors and place them in an incubator, and initialize the parameters i = 1, j = 1;

[0019] Step 2: The PC computer controls the incubator to switch to the i-th temperature test point through the network port and waits for the incubator temperature to stabilize for 2 h. The purpose is to ensure that the N-channel silicon resonant sensors inside the incubator are all kept at temperature balance;

[0020] Step 3: Control the pressure controller assembly to provide the j-th pressure source for the silicon resonant sensors;

[0021] Step 4: After the pressure source is stabilized, sequentially collect the temperature-pressure data and frequency data output by the N silicon resonant sensors.

[0022] Step 5: j = j + 1, determine whether j is greater than J. If it is equal, proceed to the next step; otherwise, return to Step 3.

[0023] Step 6: i = i + 1, determine whether i is greater than I. If it is equal, proceed to the next step; otherwise, return to Step 2.

[0024] Step 7: Perform median filtering on the temperature-pressure data and frequency data corresponding to different pressures at each temperature point of the N silicon resonant sensors, and then save them as a two-dimensional matrix.

[0025] Step 8: Calculate the calibration coefficients based on the two-dimensional matrix data of different pressure points at different temperature points.

[0026] Step 9: Calibrate the silicon resonant sensors using the calibration coefficients.

[0027] Furthermore, J is the number of pressure points to be tested, with a quantity of 15, which are 140 kPa, 130 kPa, 120 kPa, 110.4 kPa, 100 kPa, 90 kPa, 80 kPa, 70 kPa, 60 kPa, 50 kPa, 40 kPa, 30 kPa, 20 kPa, 10 kPa, and 3.5 kPa respectively.

[0028] Furthermore, I is the number of temperature points to be tested, with a quantity of 9, which are -55 °C, -40 °C, -20 °C, 0 °C, 15 °C, 30 °C, 50 °C, 70 °C, and 85 °C respectively.

[0029] Furthermore, the process of calculating the calibration coefficients is as follows:

[0030] In the actual application scenario, a pressure-frequency signal f and a temperature-voltage signal v are output by the silicon resonant sensor to calculate the measured pressure P, and the pressure value is calculated using a polynomial:

[0031]

[0032] where K mn is a 6*6 upper triangular coefficient matrix

[0033] f is the pressure frequency, calculated according to formula (1), and f′ and Δf are constant coefficients;

[0034] t is the measured pressure temperature, calculated according to formula (1), and v′ and Δv are constant coefficients;

[0035] Substitute the pressure standard values Pij, their corresponding pressure frequencies fi, and temperature voltages vj of each temperature and pressure test point into the above polynomial to construct a linear equation system with I*J equations and 21 unknowns, and find its least squares solution to obtain the calibration coefficient K mn 。

[0036] Advantageous Effects

[0037] Based on the test environment of traditional silicon resonant sensors, the present invention adds an STM32 acquisition circuit module and a PC computer. The temperature conditions and pressure conditions are automatically set through a program, and the test data of N silicon resonators at each temperature calibration point and pressure calibration point are collected and saved, realizing automatic testing during the silicon resonator testing process and greatly reducing the human and material resources consumed. In addition, through the pressure frequency and temperature voltage data obtained from the test, calibration coefficients of N silicon resonators are generated, and the pressure output by the silicon resonator sensor is calculated by using the pressure frequency signal, temperature voltage signal, and calibration coefficient, realizing temperature calibration of the pressure output by the silicon resonator sensor and improving the output accuracy of the silicon resonator sensor. Brief Description of the Drawings

[0038] Figure 1 is a schematic diagram of the principle block diagram of the present invention;

[0039] Figure 2 is the STM32 multi-channel acquisition circuit diagram of the present invention. Detailed Embodiments

[0040] The following further describes the specific implementation of the present invention with reference to the drawings.

[0041] The multi-channel silicon resonator sensor test system based on STM32 of the present invention is characterized in that it includes a PC computer, an STM32 acquisition circuit module with high and low temperature resistance and multi-channel signal acquisition function, a frequency meter / digital multimeter, a pressure controller with a vacuum pump and gas cylinder, a dual-channel DC regulated power supply, and twenty silicon resonator pressure sensors.

[0042] This system simultaneously conducts test work on 20 silicon resonator sensors. There are a total of 9 temperature points (-55°C, -40°C, -20°C, 0°C, 15°C, 30°C, 50°C, 70°C, 85°C) and 15 pressure points (140 kPa, 130 kPa, 120 kPa, 110.4 kPa, 100 kPa, 90 kPa, 80 kPa, 70 kPa, 60 kPa, 50 kPa, 40 kPa, 30 kPa, 20 kPa, 10 kPa, 3.5 kPa) for the test. The outputs of the silicon resonators at each temperature and pressure point are tested, including the pressure frequency f signal and the temperature voltage vt signal.

[0043] The STM32 multi-channel acquisition circuit board is used to control the ADC built in 20 silicon resonant sensors through the multiplexed SPI bus to acquire the temperature voltage vt of the silicon resonant sensors, and a frequency meter / digital multimeter and the frequency acquisition module on the circuit board are used to acquire the pressure frequency f of the 20 silicon resonant sensors.

[0044] A high and low temperature chamber is used to control 9 temperature points during the test of the silicon resonant sensors, and a pressure controller with a vacuum pump and gas cylinder, with a range of 200 kPa and an accuracy not less than 0.005% FS, is used to control 15 pressure points during the test of the silicon resonant sensors.

[0045] The PC computer collects the temperature voltage vt of 20 silicon resonant sensors sent by the STM32 multi-channel acquisition circuit board through the serial port; controls the frequency meter / digital multimeter to collect the pressure frequency f of the silicon resonant sensors through USB, and saves the test data of the temperature voltage vt and pressure frequency f of the silicon resonant sensors in the excel data format. Using the polynomial pressure calculation formula, a linear equation system is constructed, and through the least squares solution, the calibration coefficients of the silicon resonant sensors are obtained.

[0046] The present invention will be further described below in conjunction with the accompanying drawings:

[0047] As Figure 1 shown, the present invention is a multi-channel silicon resonant sensor test system based on STM32. It includes a PC computer, an STM32 acquisition circuit module that is resistant to high and low temperatures and has a multi-channel signal acquisition function, a frequency meter / digital multimeter, a pressure controller with a vacuum pump and gas cylinder, a dual-channel DC regulated power supply, and twenty silicon resonant pressure sensors.

[0048] a) As Figure 1 shown, after installing 20 silicon resonant sensors on the STM32 multi-channel acquisition circuit board in sequence through connectors, the circuit board is arranged in the high and low temperature chamber. The DC power supply provides 15VDC and 5VDC to the circuit board for power supply. The PC computer is connected to the acquisition circuit board through an RS422 to serial port communication line respectively, and is connected to the frequency meter / digital multimeter through USB. The vacuum pump provides a negative pressure source for the pressure controller, and the gas cylinder provides a positive pressure source for the pressure controller. The pressure controller and the silicon resonant sensors are connected through a high-temperature resistant air pipe with good sealing performance.

[0049] b) Communicate with 20 silicon resonant sensors through the built-in SPI3 communication module of STM32. The SPI bus controls and acquires the temperature voltage of the built-in ADC of 20 silicon resonant sensors through 1 SPI3_MISO IO port, 1 SPI3_MOSI IO port, 1 SPI3_CLK IO port, and 20 SPI3_CS chip select IO ports. The working process is to sequentially pull down the corresponding SPI3_CS chip select IO ports of the silicon resonators, configure the sampling rate, conversion mode, range and other modes of each silicon resonator's built-in ADC, and acquire the temperature voltage vt converted by the ADC. See the circuit diagram of the local interface between the circuit board and the silicon resonator in Figure 2 .

[0050] c) Connect the 20-channel frequency signals of the STM32 multi-channel acquisition circuit board to a frequency meter / digital multimeter (with a multi-channel acquisition card) through a dedicated electrical connection interface. The PC computer uses USB to control the frequency meter / digital multimeter to acquire the frequencies of each channel. The PC computer is connected to the RS422 communication interface of the STM32 multi-channel acquisition circuit board through an RS422 to serial communication cable.

[0051] d) Control the high and low temperature chamber to a certain temperature test point. After waiting for the temperature to stabilize for 2 hours, sequentially control the pressure controller to give different pressure test points.

[0052] e) At each temperature and pressure test point, use the upper computer acquisition software of the PC computer for single acquisition. When performing single acquisition, the PC computer will open the serial port to parse the temperature voltage data sent by the STM32 multi-channel acquisition circuit board 5 times, and perform median filtering on the temperature voltage data of each channel (remove the maximum value once, remove the minimum value once, and average the other 3 data). At the same time, it will sequentially control the frequency meter to sample the silicon resonator frequency signals of each channel 5 times (remove the maximum value once, remove the minimum value once, and average the other 3 data), perform median filtering on the pressure frequency data of each channel, and save the data to an Excel data table. The data corresponds to the temperature and pressure test points.

Claims

1. A silicon resonant sensor calibration system based on STM32, characterized in that: The system includes: a PC computer, an STM32 acquisition circuit module, a frequency meter / digital multimeter, a pressure controller component, a power supply, an RS422 serial port, and a temperature box; The PC calculation is connected to the RS422 communication interface of the STM32 acquisition circuit module through the RS422 serial port; RS422 is powered by power supply; N-channel silicon resonant sensors are connected to the multiplexed SPI bus of the STM32 acquisition circuit module; The N-channel silicon resonant sensor is also connected to the frequency acquisition adapter of the STM32 acquisition circuit module, the other end of the frequency acquisition adapter is connected to a frequency meter / digital multimeter, and the frequency meter / digital multimeter is connected to a PC computer; The pressure interface of the N-channel silicon resonant sensor is connected to the pressure controller assembly; The N-channel silicon resonant sensor is connected to the STM32 acquisition circuit module and placed in a temperature box; The PC computer is connected to the pressure controller assembly via the GPIB port.

2. The system according to claim 1, characterized in that The force controller assembly includes a pressure controller, a vacuum pump, and an air source; The vacuum pump provides a negative pressure source for the pressure controller, and the gas cylinder provides a positive pressure source for the pressure controller.

3. The system according to claim 2, characterized in that The STM32 acquisition circuit module is connected to the N-channel silicon resonant sensor through the built-in SPI3 communication module; one SPI3_MISO IO port is multiplexed in N channels for collecting pressure and temperature data, one SPI3_MOSI IO port is multiplexed in N channels for controlling the N-channel silicon resonant sensor, one SPI3_CLK IO port is multiplexed in N channels to provide the clock, and N SPI3_CS chip select IO ports are respectively connected to the N-channel silicon resonant sensors to provide chip select signals.

4. The system according to claim 3, characterized in that The frequency acquisition interface is N-channel.

5. A method for calibrating a silicon resonant sensor based on STM32, implemented based on the system of any of the preceding claims, characterized in that: The process is as follows: Step 1: Connect the silicon resonant sensor and put it in the incubator, and initialize the parameters i=1, j=1; Step 2: Control the temperature box to switch to the i-th temperature test point; Step 3: After the temperature of the incubator is stable for 2 hours, the pressure controller assembly is controlled to provide the jth pressure source for the silicon resonant sensor; Step 4: After the pressure source is stable, collect temperature, pressure and frequency data; Step 5: j=j+1, determine whether j is greater than J, if so, proceed to the next step, otherwise return to step 3; Step 6: i=i+1, determine whether i is greater than I, if so, proceed to the next step, otherwise return to the second step; Step 7: Filter the temperature and pressure data and frequency data corresponding to different pressures at each temperature point respectively, and then store them as two two-dimensional matrices respectively; Step 8: Calculate the calibration coefficient based on the two-dimensional matrix data of different pressure points at different temperature points; Step 9: Use the calibration coefficient to calibrate the silicon resonant sensor.

6. The method according to claim 5, characterized in that J is the number of pressure points to be tested, which is 15, namely 140kPa, 130kPa, 120kPa, 110.4kPa, 100kPa, 90kPa, 80kPa, 70kPa, 60kPa, 50kPa, 40kPa, 30kPa, 20kPa, 10kPa and 3.5kPa.

7. The method according to claim 6, characterized in that I is the number of temperature points to be measured, which is 9, namely -55℃, -40℃, -20℃, 0℃, 15℃, 30℃, 50℃, 70℃, and 85℃.

8. The method according to claim 7, characterized in that The process of calculating the calibration coefficient is as follows: The silicon resonant sensor outputs a pressure frequency signal f and a temperature voltage signal v to calculate the measured pressure P. The pressure value can be calculated using a polynomial: In the formula, K mn It is a 6*6 upper triangular coefficient matrix; f is the pressure frequency, calculated according to formula (1), f′ and Δf are constant coefficients; v is the measured pressure temperature, calculated according to formula (1), v′ and Δv are constant coefficients; Substitute the pressure standard value P_ij of each temperature and pressure test point and its corresponding pressure frequency fi and temperature voltage vj into the above polynomial, construct a linear equation system with the number of equations I*J and the number of unknowns 21, and find its least square solution to obtain the calibration coefficient K mn .

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