Strain sensor automatic calibration device

Abstract

In order to solve the technical problems of low efficiency and on-site confusion caused by manual operation of high-precision variable resistance box for calibration, the application provides a strain sensor automatic calibration device, which comprises an adjustable resistance box, the adjustable resistance box comprises N resistance wires, and the special features are that the device further comprises N motors, a motor driver, a motor controller and N rotary dial switches; the N rotary dial switches are connected with the N resistance wires one by one; the motor controller is used for sending control instructions to the motor driver, the motor driver drives the corresponding motor to act according to the control instructions, so as to drive each rotary dial switch to rotate and realize the adjustment and switching of the output resistance value; N is greater than or equal to 6.

Description

Technical Field

[0001] This invention relates to an automatic calibration device for strain sensor testing, mainly used for the automatic calibration of strain sensor parameters before ignition testing. Background Technology

[0002] In solid rocket motor testing, parameter acquisition of strain sensors is a crucial part of data acquisition. To ensure the accuracy and reliability of the acquired data, parameter calibration must be performed on each strain test channel before the test. The traditional calibration process mainly uses a high-precision resistance box instead of strain gauges for parameter calibration, that is, the resistance value of different steps of the strain gauge is calculated by using the factory parameters of the strain gauge (including zero resistance, coefficient K and maximum strain).

[0003] The testing process is as follows: the output resistance of the resistance box is adjusted to the factory zero-value of the strain parameter. Then, based on this output resistance value, the output resistance of the resistance box is further adjusted to output different resistance signals to simulate the working state of the strain sensor. This test often requires calibrating multiple types of strain sensors and setting step values ​​to obtain the regression coefficients during the operation of the strain sensor.

[0004] Due to the differences among strain sensors, it is necessary to calculate the corresponding resistance value of each strain sensor, set the step number, and complete the calibration in conjunction with the data acquisition system. Traditional solid rocket motor strain test parameter acquisition methods require individual calibration of each strain sensor, often necessitating manual operation of a high-precision variable resistance box. When there are many strain acquisition channels in the test, this method consumes a long preparation time. Furthermore, when multiple strain channels are required, the large number of voltage signals, DC power supplies, cables, and connection points necessitate the use of multiple external power supplies and cables, easily causing chaos at the test site, leading to operational errors, and affecting the reliability and efficiency of parameter acquisition. To a certain extent, this method cannot meet the evolving needs of engine testing in terms of safety, mobility, and accuracy. Summary of the Invention

[0005] Based on the above background technology, to solve the technical problems of low efficiency and chaotic on-site operation caused by manual operation of high-precision variable resistance boxes for calibration, this invention proposes an automatic calibration device for strain sensors. This invention can simultaneously provide multiple strain simulation signals to complete the automatic calibration of strain sensors, ensuring the reliability and accuracy of actual strain parameter acquisition during test ignition, while greatly improving the efficiency of strain calibration during testing.

[0006] The technical solution of this invention is:

[0007] An automatic calibration device for strain sensors includes an adjustable resistance box comprising N resistance wires. Its unique feature is that it also includes N motors, motor drivers, a motor controller, and N rotary toggle switches. Each of the N rotary toggle switches is connected to one of the N resistance wires. The motor controller sends control commands to the motor drivers, which in turn drive the corresponding motors to rotate, thereby adjusting the output resistance value. N ≥ 6.

[0008] Furthermore, N = 6.

[0009] Furthermore, the six output resistance levels are represented by X1, X2...X6, which represent the ×100 level, ×10 level, ×1 level, ×0.1 level, ×0.01 level and ×0.001 level, respectively. The resistance adjustment number for the X3 level is 1 to 11, and the resistance adjustment number for the other levels is 0 to 9.

[0010] Furthermore, the motor is set to rotate 30° per step, and a stall signal is set at the maximum rotation angle of 300°.

[0011] Furthermore, the control flow of the motor by the motor controller is as follows:

[0012] Step 1: Initialize the motors for each gear position;

[0013] Step 2: Determine if the required output resistance value X6X5X4.X3X2X1 is greater than 0.1 ohms. If not, the output resistance value X6X5X4.X3X2X1 is 0.1 ohms, and all 6 motors need to rotate at 0 degrees. If yes, proceed to Step 3.

[0014] Step 3: Determine if the value of X3 in the required output resistance value X6X5X4.X3X2X1 is 0. If not, determine the gear positions according to the values ​​of each digit in the required output resistance value X6X5X4.X3X2X1: X6 gear takes the current value of X6, X5 gear takes the current value of X5, X4 gear takes the current value of X4, X3 gear takes the current value of X3, X2 gear takes the current value of X2, and X1 gear takes the current value of X1. Drive each motor to rotate to the corresponding angle according to each gear value. If yes, proceed to Step 4.

[0015] Step 4: Determine if the value of X4 in the required output resistance value X6X5X4.X3X2X1 is 0. If not, determine the gear positions according to the values ​​of each digit in the required output resistance value X6X5X4.X3X2X1: X6 gear takes the current value of X6, X5 gear takes the current value of X5, X4 gear takes the current value of X4 - 1, X3 gear takes 10, X2 gear takes the current value of X2, and X1 gear takes the current value of X1. Drive each motor to rotate to the corresponding angle according to each gear value. If yes, proceed to Step 5.

[0016] Step 5: Determine if the value of X5 in the required output resistance value X6X5X4.X3X2X1 is 0. If not, determine the gear positions according to the values ​​of each digit in the required output resistance value X6X5X4.X3X2X1: X6 gear takes the current value of X6, X5 gear takes the current value of X5 - 1, X4 gear takes the current value of X4 - 1, X3 gear takes 10, X2 gear takes the current value of X2, and X1 gear takes the current value of X1. Drive each motor to rotate to the corresponding angle according to the value of each gear. If yes, proceed to step 6.

[0017] Step 6: Determine if the value of X6 in the required output resistance value X6X5X4.X3X2X1 is 0. If not, determine the gear positions according to the values ​​of each digit in the required output resistance value X6X5X4.X3X2X1: X6 position takes the current value of X6 minus 1, X5 position takes the current value of X5 minus 1, X4 position takes the current value of X4 minus 1, X3 position takes 10, X2 position takes the current value of X2, and X1 position takes the current value of X1. Drive each motor to rotate to the corresponding angle according to the value of each gear. If the value is 0, the resistance value is abnormal, and return to step 1.

[0018] The advantages of this invention are:

[0019] 1. This invention allows for the pre-input and saving of strain sensor parameters. By calculating the optimal step value, it automatically outputs the corresponding strain resistance value to the acquisition circuit, enabling the rapid completion of strain sensor calibration in conjunction with existing acquisition systems, thus greatly improving work efficiency.

[0020] 2. This invention is highly versatile and can meet the requirements of multiple strain signals in the testing of various types of solid rocket engines. It does not require external multiple power supplies and cables. The overall structure of the chassis is lightweight and easy to carry, solving the problems of messy wiring and easy misoperation on site. In actual work, it is safe and reliable to operate and stable, shortens the preparation time before the test, improves the efficiency of on-site work, and avoids interference between power supplies in the field test, achieving a strong anti-interference capability and ensuring the reliability and safety of strain sensor calibration before engine test ignition.

[0021] 3. This invention can provide up to 16 channels of precise resistance values ​​from 0.100Ω to 999.999Ω at a time, with the resistance accuracy of the display and output being ±0.001Ω, and the interval between continuous adjustment of the output resistance value being greater than 1 second.

[0022] 4. The output resistance of this invention is controlled by the motor control circuit at the input end. Since the output resistance of each gear is independent of each other, interference caused by rapid switching is well avoided. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the automatic calibration device of the present invention.

[0024] Figure 2 This is a schematic diagram of the rotary switching switch in the automatic calibration device of the present invention.

[0025] Figure 3 This is a schematic diagram of the structure of the housing in the automatic calibration device of the present invention.

[0026] Figure 4 This is a schematic diagram of the drive circuit in the automatic calibration device of the present invention.

[0027] Figure 5 This is a schematic diagram of the control circuit in the automatic calibration device of the present invention.

[0028] Figure 6 This is a schematic diagram of the working principle of the resistance output switching relay circuit in the automatic calibration device of this invention.

[0029] Figure 7 This is a flowchart of the motor control process in the automatic calibration device of the present invention.

[0030] Figure 8 This is a diagram of the human-machine interface in the automatic calibration device of the present invention. Detailed Implementation

[0031] The automatic calibration device for strain sensors of the present invention includes an adjustable resistance box and a data acquisition system. The data acquisition system is the same as that of existing automatic calibration devices. The main feature of the present invention is that it improves upon the existing adjustable resistance box, which can output multiple high-precision strain resistance values. The resistance values ​​are switched using a toggle switch, and then controlled by a stepper motor to achieve rapid and automatic output of high-precision resistance values. In implementation, it is first necessary to determine the linear relationship between the strain value and the resistance value of the strain sensor, and secondly, to determine the number of calibration steps for the strain sensor.

[0032] The key technical problems that this invention needs to solve are threefold:

[0033] First, it requires high-precision resistance output to achieve the conversion of multiple signals at the test site, meet the needs of the acquisition system for both continuous voltage signal adjustment and high-precision stable signal output, and realize unattended automatic calibration process.

[0034] Secondly, the optimal calculation of the step value of the strain gauge is used to solve the problem of selecting the step value during the calibration process of the strain sensor, reduce invalid calibration, and improve test efficiency.

[0035] Thirdly, the control of motors at each gear position, especially the zero-position judgment.

[0036] The present invention is implemented as follows:

[0037] Welding on the resistance wire of an existing high-precision resistance box Figure 2 The rotary toggle switch shown is equipped with a stepper motor to drive its rotation, serving as a basic resistance output unit. It features a simple structure, convenient operation, and reliable contact. Since the motor's rotation drives the rotary toggle switch, and the rotary toggle switch is connected to a resistance wire, the motor's rotation can switch the resistance value. This invention uses six stepper motors, corresponding to six resistance value levels (i.e., ×0.001, ×0.01, ×0.1, ×1, ×10, ×100). Each resistance value level uses a rotatable multi-way switch, allowing adjustment of the circuit resistance range from 0.100Ω to 999.999Ω.

[0038] The present invention will be further described below with reference to the accompanying drawings.

[0039] like Figure 1 As shown, the automatic calibration device of the present invention includes a power supply module, an interface module, a motor, a motor driver, a motor controller, a display module, a touch panel, a relay module, and a rotary toggle switch. The power supply module supplies power to the motor driver, motor controller, and other modules; the power supply module is externally connected to a DC24V power supply and generates six stable DC12V drive voltages through a voltage conversion circuit. The power supply modules are independent of each other, improving the device's anti-interference capability. The front and rear ends of the circuits are opto-isolated, ensuring that the acquired signals are independent and do not interfere with each other, thus improving reliability.

[0040] The interface module is used to flexibly configure the resistance values ​​of each range by switching the relay module, which can realize the output of the channel resistance value or the output of the acquired signal of the channel. The interface module includes a DC power input interface, a remote communication interface and an output interface, all of which are located on the rear panel of the device enclosure.

[0041] The touch panel is used for on-site input of strain sensor parameters and is located on the top panel of the device housing.

[0042] The motor controller sends control commands to the motor driver. The motor driver, based on the received control commands, drives the corresponding motor action to rotate the rotary toggle switch, thereby adjusting and switching the output resistance value. The output resistance value is then displayed through the display module. For example... Figure 5 As shown, the motor controller circuit uses the PIC32MX series chip, a 32-bit microcontroller from Microchip Technology. Its main frequency can reach up to 50MHz, enabling it to send high-frequency pulse signals. It also features built-in SPI and UART interfaces and can use up to four timers. The control circuit primarily receives data from the interactive interface (including remote data and touchscreen data) and sends pulse and direction commands to the motor driver.

[0043] The power module, motor, motor driver, and motor controller are all housed inside the device enclosure.

[0044] To achieve seamless integration with existing high-precision resistance boxes, this invention designs as follows: Figure 3 The box shown.

[0045] The motor control principle of this invention is:

[0046] The six output resistance levels are represented by X1, X2...X6, where X6 represents the ×100 level, X5 represents the ×10 level, X4 represents the ×1 level, X3 represents the ×0.1 level, X2 represents the ×0.01 level, and X1 represents the ×0.001 level. By driving the corresponding rotary switches with each motor, the output resistance values ​​can be X6X5X4.X3X2X1, that is, the output resistance range is 0.100 to 999.999 ohms.

[0047] For ease of adjustment, each 30° rotation of the motor is defined as one step, and six motors are controlled simultaneously. The adjustment values ​​for each gear are specified as follows:

[0048] The resistance adjustment numbers for the X3 setting (i.e., the ×0.1 setting) range from 1 to 11, where: 0 degrees corresponds to a value of 1, 30 degrees to a value of 2, 60 degrees to a value of 3, ..., 270 degrees to a value of 10, and 300 degrees to a value of 11.

[0049] The resistance adjustment values ​​for the X1 (×0.001), X2 (×0.01), X4 (×1), X5 (×10), and X6 (×100) range from 0 to 9, where: 0 degrees corresponds to 0, 30 degrees to 1, 60 degrees to 2, ..., 240 degrees to 8, and 270 degrees to 9.

[0050] Divide 360° (one rotation of the motor) into 12 equal parts, and set a stall signal at the maximum rotation angle of 300°, meaning that the motor deflection angle is not allowed to exceed 300°. This will allow X to... i The motor rotation angle corresponding to the resistance value of the gear is converted to 30*(X). i (Number of rotation steps of the gear).

[0051] Based on the aforementioned range adjustment parameters, the output resistance of this invention must be greater than 0.1 ohms. Therefore, by means of... Figure 7 The judgment process shown controls the motor at each gear position. When a stall occurs, it is considered an abnormality in rotation, requiring a return to zero and re-execution. The specific control process is as follows:

[0052] Step 1: Initialize the motors for each gear position;

[0053] Step 2: Determine if the required output resistance value X6X5X4.X3X2X1 is greater than 0.1 ohms. If not, the output resistance value X6X5X4.X3X2X1 is 0.1 ohms, and all 6 motors need to rotate at 0 degrees. If yes, proceed to Step 3.

[0054] Step 3: Determine if the value of X3 (i.e., the ×0.1 level) in the required output resistance value X6X5X4.X3X2X1 is 0. If not, determine the level as follows based on the values ​​of each element in the required output resistance value X6X5X4.X3X2X1: X6 level takes the current value of X6, X5 level takes the current value of X5, X4 level takes the current value of X4, X3 level takes the current value of X3, X2 level takes the current value of X2, and X1 level takes the current value of X1. Drive each motor to rotate to the corresponding angle according to each level value. If yes, proceed to Step 4.

[0055] Step 4: Determine if the value of X4 (i.e., the ×1 level) in the required output resistance value X6X5X4.X3X2X1 is 0. If not, determine the level as follows based on the values ​​of each element in the required output resistance value X6X5X4.X3X2X1: X6 level takes the current value of X6, X5 level takes the current value of X5, X4 level takes the current value of X4 - 1, X3 level takes 10, X2 level takes the current value of X2, and X1 level takes the current value of X1. Drive each motor to rotate to the corresponding angle according to each level value. If yes, proceed to Step 5.

[0056] Step 5: Determine if the value of the X5 range (i.e., the ×10 range) in the required output resistance values ​​X6X5X4.X3X2X1 is 0. If not, determine the ranges as follows based on the values ​​of each element in the required output resistance values ​​X6X5X4.X3X2X1: X6 range takes the current value of X6, X5 range takes the current value of X5 minus 1, X4 range takes the current value of X4 minus 1, X3 range takes 10, X2 range takes the current value of X2, and X1 range takes the current value of X1. Drive each motor to rotate to the corresponding angle according to the value of each range. If yes, proceed to Step 6.

[0057] Step 6: Determine if the value of X6 (i.e., the ×100 range) in the required output resistance value X6X5X4.X3X2X1 is 0. If not, determine the ranges as follows: X6 range takes the current value of X6 minus 1, X5 range takes the current value of X5 minus 1, X4 range takes the current value of X4 minus 1, X3 range takes 10, X2 range takes the current value of X2, and X1 range takes the current value of X1. Drive each motor to rotate to the corresponding angle according to the value of each range. If yes, the resistance value is abnormal, and return to Step 1.

[0058] The method for determining the number of steps in this invention:

[0059] Assume the minimum resistance of the strain sensor is R. min The maximum resistance is R max The maximum output resistance value that needs to be calibrated for the test is R.

[0060] If R min <R<(1 / 2)R max Set the number of calibration steps to 3;

[0061] If (1 / 2)R max <R<(2 / 3)R max Set the number of calibration steps to 4;

[0062] If (2 / 3)R max <R<R max Set the number of calibration steps to 5.

[0063] Once the number of steps in the calibration process is determined, the linear relationship between the strain value and the resistance value can be calculated. Then, the controller can control the motor to achieve a stable output of the resistance value. The output resistance value is then automatically switched to the acquisition loop, and the automatic calibration process can be achieved using existing methods.

[0064] like Figure 8 The diagram shows the human-machine interface of the calibration device of the present invention. Through the interactive interface, the channel number, sensor number, factory zero-position resistance value, coefficient K value and maximum calibration value can be input to calculate multiple step values ​​for strain calibration of the channel.

[0065] The control buttons on the interactive interface include system reset, return to zero, and next step. When the "next step" button is clicked, the three sets of resistance values ​​for that channel are sent to the controller, which then drives the motor to complete the resistance value setting. Different channel resistance values ​​are output according to the channel selected on the touchscreen.

[0066] The strain calibration parameters (channel number, strain sensor model, number of calibration steps, factory resistance value (zero resistance value), maximum strain value, and strain coefficient) of the automatic strain sensor calibration device of the present invention can be input not only through the human-machine interface, but also through the existing acquisition system via the communication cable. When the strain calibration parameters of each channel are sent through the remote acquisition system, they are downloaded to the automatic calibration device in text file format and displayed.

[0067] In practical operation, the strain calibration parameters of different types of strain sensors are first input into the automatic calibration device via the input interface. Each time, the automatic calibration device automatically adjusts the channels and resistance values ​​to complete the calibration process of the strain sensors. According to the signal timing requirements, the signals generated by the device are simultaneously received by the testing system and the acquisition system, completing various calibration controls required for the test. The automatic calibration device can provide up to 16 channels of precise resistance values ​​ranging from 0.100Ω to 999.999Ω at a time, with a display and output resistance accuracy of ±0.001Ω, and continuous adjustment intervals of output resistance values ​​greater than 1 second. It can be said that the automatic calibration device of this invention fully meets the technical specifications and requirements for automatic calibration of strain sensors in engine ground ignition tests.

Claims

1. An automatic calibration device for a strain sensor, comprising an adjustable resistance box, wherein the adjustable resistance box comprises N resistance wires; characterized in that: It also includes N motors, motor drivers, motor controllers, and N rotary toggle switches; the N rotary toggle switches are connected one-to-one with the N resistance wires; the motor controller is used to send control commands to the motor drivers, and the motor drivers drive the corresponding motors to move according to the control commands, so as to drive each rotary toggle switch to rotate and realize the adjustment and switching of the output resistance value; N=6; The six output resistance levels are respectively used... The numbers represent the x100, x10, x1, x0.1, x0.01, and x0.001 levels, respectively. The resistance adjustment numbers for the x3 level are 1 to 11, and the resistance adjustment numbers for the other levels are 0 to 9. Set the motor to rotate every As a step, at the maximum rotation angle Set a stall signal; The control process of the motor controller for the motor is as follows: Step 1: Initialize the motors for each gear position; Step 2: Determine the required output resistance value Is it greater than 0.1 ohms? If not, then the output resistance value is... If the value is 0.1 ohms, then all 6 motors need to rotate at 0 degrees; if so, proceed to step 3. Step 3: Determine the required output resistance value In If the value is 0, then the required output resistance value is determined. The individual values ​​in the data determine the gear positions as follows: File retrieval The current value, File retrieval The current value, File retrieval The current value, File retrieval The current value, Retrieve the current value of X2. File retrieval The current value is determined, and each motor is driven to rotate to the corresponding angle according to the value of each gear; if so, proceed to step 4. Step 4: Determine the required output resistance value Is the value of X4 in the output resistor 0? If not, then the required output resistance value should be determined. The individual values ​​in the data determine the gear positions as follows: X6 gear is taken as... The current value, File retrieval Current value, X4 mode The current value -1 File 10 File retrieval The current value, File retrieval The current value is determined, and each motor is driven to rotate to the corresponding angle according to the value of each gear; if so, proceed to step 5. Step 5: Determine the required output resistance value In If the value is 0, then the required output resistance value is determined. The individual values ​​in the data determine the gear positions as follows: File retrieval The current value; for X5 mode, the current value of X5 minus 1; for X4 mode, the current value of X4 minus 1. File 10 File retrieval The current value, File retrieval The current value is used to drive each motor to rotate to the corresponding angle based on the value of each gear. If so, proceed to step 6; Step 6: Determine the required output resistance value In If the value is 0, then the required output resistance value is determined. The individual values ​​in the data determine the gear positions as follows: X6 gear is taken as... The current value -1 File retrieval The current value -1 File retrieval The current value -1 File 10 File retrieval The current value, File retrieval The current value is used to drive each motor to rotate to the corresponding angle based on the value of each gear. If so, the resistance value is abnormal, and return to step 1.

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