Method for applying constant force to half-mode balance calibration system

Abstract

The invention belongs to the technical field of multi-component aerodynamic load measurement sensors, and discloses a method for applying a constant force to a half-mode balance calibration system. The method for applying the constant force comprises the following steps: installing the constant force value loading device; accurate force value loading is carried out; carrying out displacement real-time compensation; constant force value output is kept at all the force application device point positions; and completing the ground static calibration of the half-mode balance. According to the method for applying constant force, the displacement of the electric cylinder is calculated according to the value of the applied force, after the corresponding displacement of the electric cylinder is completed through closed-loop control of the driving electric cylinder, the steel spring inevitably generates creep displacement in the process of waiting for arrival of a plurality of force application device point positions, and the creep displacement is changed into the creep displacement. The applied force value corresponding to the creep deformation is synchronously measured by the high-precision force sensor, the compensation displacement of the piezoelectric ceramic is correspondingly calculated, the creep deformation displacement is dynamically compensated in real time, the constant force value loading device is ensured to be always at the required constant force value, and the high-precision calibration of the half-mode balance is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of multi-component aerodynamic load measurement sensors, and particularly relates to a method for applying a constant force to a half-model balance calibration system. Background Art

[0002] The half-model balance is the core force-measuring device for wind tunnel half-model tests. Before a wind tunnel half-model test, it is necessary to use a half-model balance calibration system to perform ground static calibration on the half-model balance and fit the working matrix of the applied force value F and the bridge output voltage U. The half-model balance calibration system generally adopts a ground axis system calibration method and does not perform reset during the calibration process. Therefore, the calibration data accuracy depends on the accuracy of the applied force value device. Under the condition of a large force value (generally greater than 20,000 N), the half-model balance calibration system is a combined system of a steel spring, an electric cylinder, and a high-precision force value sensor. The pulling force value is controlled by the telescopic displacement of the electric cylinder. The electric cylinder stretches the steel spring, and the steel spring is stretched to generate a corresponding pulling force, and a high-precision force value sensor is used to measure the pulling force value.

[0003] In the half-model balance calibration system combined with a steel spring, an electric cylinder, and a high-precision force value sensor, the force value is simplified and calculated by Hooke's law, and the pulling force F = kx (k is the spring coefficient, x is the spring stretching distance) is obtained. However, due to the non-uniform material in the manufacturing process of the steel spring and the rotation at the installation joint in the later stage, the high-precision force value cannot be accurately calculated according to Hooke's law. Therefore, it is necessary to perform one-to-one single-group spring calibration in the early stage. During calibration, the force value F is steppedly loaded within the required force value range for work, and the corresponding displacement L is recorded. Finally, the functional relationship f(F, L) between the force value F and the displacement L is fitted, which is used to determine the spring displacement during later force application.

[0004] The electric cylinder is generally composed of a servo motor, a reducer, and a lead screw. After power-on, the number of servo motor pulses is calculated by combining the required displacement with the lead screw pitch. Generally, the electric cylinder displacement is feedback by an encoder. However, the displacement accuracy of this electric cylinder is not very high because the mechanical error (a certain gap must be left for the installation of the reducer) and the measurement error of the encoder determine that the highest electric cylinder displacement control accuracy is 0.02 mm, and the electric cylinder displacement control accuracy cannot be further improved by internal improvement methods. The constant force device adopts an external feedback method to improve the electric cylinder displacement control accuracy, that is, a grating scale is installed on the electric cylinder body to measure the electric cylinder displacement in real time and feedback it to the servo motor in the electric cylinder, so that the servo motor continues to operate until the set electric cylinder displacement is the same as the actual electric cylinder displacement, and the closed-loop electric cylinder realizes a control accuracy of 0.002 mm level.

[0005] When the closed-loop electric cylinder runs to the set position, the entire system reaches the ideal state. However, since the semi-mode balance is a multi-component force sensor, calibration forces are applied to multiple components simultaneously during the calibration process, and the force values at each point are different according to the designed range. Therefore, it is impossible to ensure that the force values at each point reach simultaneously. The points that arrive earlier need to maintain a constant force value for a certain period of time until all points complete the high-precision force application and then are collected uniformly. Because the spring in the combination of the steel spring, the closed-loop electric cylinder, and the high-precision force sensor will inevitably produce creep, a slight displacement will occur during the waiting period, and this displacement corresponds to the corresponding force value, thus preventing each point of the force application device from maintaining the ideal state of a constant force value.

[0006] Creep is the tendency of solid materials to move or deform slowly and permanently under the influence of stress. It occurs as a result of the long-term action of stress below the yield strength of the material, and creep often intensifies with increasing temperature. The creep of metal materials is affected by multiple factors, mainly including metallurgy, microstructure, and external conditions. Metallurgical factors such as alloying elements, grain size, impurities, and phase changes affect the creep resistance. The effects of fine grains and coarse grains are opposite at room temperature and high temperature. Grain boundary sliding is very insignificant at room temperature and can account for most of the total creep at high temperatures. External conditions include temperature, load, and heat treatment effects. The greater the temperature and the heavier the load, the greater the creep, and the uniformity of heat treatment also affects the creep morphology. Steel springs are generally made of die steel and will produce creep throughout the process of force application, which is inevitable. Only ways need to be found to overcome the force value error caused by creep.

[0007] Currently, there is an urgent need to develop a method for applying a constant force in a semi-mode balance calibration system. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for applying a constant force in a semi-mode balance calibration system to overcome the defects of the prior art.

[0009] The method for applying a constant force in the semi-mode balance calibration system of the present invention includes the following steps: S10. Install a constant force value loading device; The constant force value loading device includes an electric cylinder, a piezoelectric ceramic, and a steel spring connected in sequence. The steel spring is connected to a steel wire rope, the steel wire rope is connected to the semi-mode balance and the corresponding force application device points on the loading head, and a force sensor is arranged on the steel wire rope; S20. Perform precise force value loading; S21. Calculate the displacement L1 of the steel spring, and calculate the required displacement L1 of the steel spring and the corresponding displacement of the electric cylinder by using the functional relationship f(F1, L1) between the force value F1 and the displacement L1 of the steel spring calibrated in advance for the force F0 to be applied; S22. Drive the electric cylinder to perform telescopic motion to reach the displacement of the electric cylinder, causing the steel spring to generate a displacement L1; S23. Record the measured value F1 of the force sensor; S24. Calculate the load error △F1 = F1 - F0; S25. Determine whether the load error △F1 meets the pre-set error range; S26. If the load error △F1 does not meet the pre-set error range, repeat steps S21~S25 until the real-time force value measured by the force sensor meets the error range; S30. Perform real-time displacement compensation; Control the piezoelectric ceramic to perform real-time displacement compensation, overcoming the creep of the steel spring through the piezoelectric ceramic to maintain a constant force value output. The specific steps are as follows: S31. Record the measured value F2 of the force sensor; S32. Calculate the creep displacement of the steel spring △F2 = F2 - F1; S33. Calculate the compensation displacement L2 of the piezoelectric ceramic; Calculate the compensation displacement L2 of the piezoelectric ceramic through the function relation f(F2, L2) of the force value F2 and displacement L2 of the piezoelectric ceramic calibrated in the early stage; S34. Calculate the proportional coefficient μ1 = L2 / L T , L T is the full-scale displacement of the piezoelectric ceramic; S35. Calculate the voltage U2 required for the piezoelectric ceramic to move, U2 = U T × μ1, U T is the control power supply voltage of the piezoelectric ceramic; S36. Through the power control D / A card of the constant force value loading device, generate the voltage U2 to drive the piezoelectric ceramic to generate the compensation displacement L2; S37. Repeat S31~S36 to keep the force application device point at a constant force value output; S40. Keep the constant force value output at all force application device points; [[ID=�0]] The force application device points of the half-mode balance and the loading head include the negative Z-direction force application device point, the positive Y-direction force application device point, the positive Z-direction force application device point, and the negative Y-direction force application device point; Keep the constant force value output at all force application device points on the half-mode balance and the loading head to complete the loading process of one loading point of the half-mode balance and the loading head; S50. Complete the ground static calibration of the half-mode balance; According to the pre-set loading sequence, complete the loading process of all loading points to obtain the ground static calibration working matrix of the half-mode balance.

[0010] Furthermore, the applied force value error of the constant force value loading device is less than or equal to 0.01%.

[0011] The method for applying a constant force by the semi-mode balance calibration system of the present invention calculates the displacement of the electric cylinder according to the magnitude of the applied force value. After the corresponding electric cylinder displacement is completed by the closed-loop control of the driving electric cylinder, during the process of waiting for multiple force application device positions to arrive, the steel spring inevitably generates a creep displacement. The applied force value corresponding to the creep is synchronously measured by a high-precision force sensor, and the compensation displacement of the piezoelectric ceramic is calculated correspondingly to dynamically compensate the creep displacement in real time, ensuring that the constant force value loading device is always at the required constant force value and realizing the high-precision calibration of the semi-mode balance. Description of the Drawings

[0012] Figure 1 is a flowchart of the method for applying a constant force by the semi-mode balance calibration system of the present invention; Figure 2 is a schematic structural diagram of the constant force value loading device used in the method for applying a constant force by the semi-mode balance calibration system of the present invention; Figure 3 is a schematic diagram of the positions of the force application devices in the method for applying a constant force by the semi-mode balance calibration system of the present invention.

[0013] In the figure, 1. Steel spring; 2. Piezoelectric ceramic; 3. Electric cylinder; 4. Force sensor; 21. Semi-mode balance and loading head; 22. Negative Z-direction force application device position; 23. Positive Y-direction force application device position; 24. Positive Z-direction force application device position; 25. Negative Y-direction force application device position. Detailed Embodiment

[0014] The present invention will be described in detail below with reference to the drawings and embodiments.

[0015] Embodiment: As Figure 1 shown, the method for applying a constant force by the semi-mode balance calibration system of this embodiment includes the following steps: S10. Install the constant force value loading device; As Figure 2 shown, the constant force value loading device includes an electric cylinder 3, a piezoelectric ceramic 2, and a steel spring 1 connected in sequence. The steel spring 1 is connected to a steel wire rope, the steel wire rope is connected to the corresponding force application device position on the semi-mode balance and loading head 21, and a force sensor 4 is arranged on the steel wire rope; S20. Perform precise force value loading; S21. Calculate the displacement L1 of the steel spring 1, and calculate the required displacement L1 of the steel spring 1 and the corresponding electric cylinder displacement according to the functional relationship f(F1, L1) between the force value F1 and the displacement L1 of the steel spring 1 calibrated in advance for the force F0 to be applied; S22. Drive the electric cylinder 3 to perform telescopic motion to reach the electric cylinder displacement, causing the steel spring 1 to generate a displacement L1; S23. Record the measured value F1 of the force sensor 4; S24. Calculate the load error △F1 = F1 - F0; S25. Determine whether the load error △F1 meets the preset error range; S26. If the load error △F1 does not meet the preset error range, repeat steps S21 - S25 until the real-time force value measured by the force sensor 4 meets the error range; S30. Perform real-time displacement compensation; Control the piezoelectric ceramic 2 to perform real-time displacement compensation, overcoming the creep of the steel spring 1 through the piezoelectric ceramic 2 to maintain a constant force value output. The specific steps are as follows: S31. Record the measured value F2 of the force sensor 4; S32. Calculate the creep displacement of the steel spring 1 △F2 = F2 - F1; S33. Calculate the compensation displacement L2 of the piezoelectric ceramic 2; Calculate the compensation displacement L2 of the piezoelectric ceramic 2 through the function relationship f(F2, L2) between the force value F2 and the displacement L2 of the piezoelectric ceramic 2 calibrated in the early stage; S34. Calculate the proportional coefficient μ1 = L2 / L T , L T is the full-scale displacement of the piezoelectric ceramic; S35. Calculate the voltage U2 required for the piezoelectric ceramic 2 to move, U2 = U T × μ1, U T is the control power supply voltage of the piezoelectric ceramic; S36. Through the power control D / A card of the constant force value loading device, generate the voltage U2 to drive the piezoelectric ceramic 2 to generate the compensation displacement L2; S37. Repeat S31 - S36 to keep the force application device point at a constant force value output; S40. Keep a constant force value output at all force application device points; As Figure 3 shown, the force application device points of the half-mode balance and the loading head 21 include the negative Z-direction force application device point 22, the positive Y-direction force application device point 23, the positive Z-direction force application device point 24, and the negative Y-direction force application device point 25; Keep a constant force value output at all force application device points on the half-mode balance and the loading head 21 to complete the loading process of one loading point of the half-mode balance and the loading head 21; S50. Complete the ground static calibration of the half-mode balance; Complete the loading process of all loading points according to the pre-set loading sequence to obtain the working matrix of the semi-modal balance ground static calibration.

[0016] Further, the applied force value error of the constant force value loading device is less than or equal to 0.01%.

[0017] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. For those skilled in the art, without departing from the principle of the present invention, all the features disclosed in the present invention, or all the steps in the disclosed methods or processes, except for mutually exclusive features and / or steps, can be combined in any way. The present invention is not limited to the specific details and the illustrated examples here.

Claims

1. A method for applying a constant force in a semi-modal balance calibration system, characterized in that, The method for applying a constant force includes the following steps: S10. Install a constant force value loading device; The constant force value loading device includes an electric cylinder (3), a piezoelectric ceramic (2), and a steel spring (1) connected in sequence. The steel spring (1) is connected to a steel wire rope, and the steel wire rope is connected to the corresponding force application device point on the half-mode balance and the loading head (21). A force sensor (4) is provided on the steel wire rope; S20. Perform precise force value loading; S21. Calculate the displacement L1 of the steel spring (1), and calculate the required displacement L1 of the steel spring (1) and the corresponding electric cylinder displacement through the functional relationship f(F1, L1) between the force value F1 and the displacement L1 of the steel spring (1) calibrated in advance for the force F0 to be applied; S22. Drive the electric cylinder (3) to perform telescopic movement to reach the electric cylinder displacement, so that the steel spring (1) generates a displacement L1; S23. Record the measured value F1 of the force sensor (4); S24. Calculate the load error △F1 = F1 - F0; S25. Determine whether the load error △F1 meets the pre-set error range; S26. If the load error △F1 does not meet the pre-set error range, repeat steps S21~S25 until the real-time force value measured by the force sensor (4) meets the error range; S30. Perform real-time displacement compensation; Control the piezoelectric ceramic (2) to perform real-time displacement compensation, and overcome the creep of the steel spring (1) through the piezoelectric ceramic (2) to maintain a constant force value output. The specific steps are as follows: S31. Record the measured value F2 of the force sensor (4); S32. Calculate the creep displacement △F2 of the steel spring (1) = F2 - F1; S33. Calculate the compensation displacement L2 of the piezoelectric ceramic (2); Calculate the compensation displacement L2 of the piezoelectric ceramic (2) through the functional relationship f(F2, L2) between the force value F2 and the displacement L2 of the piezoelectric ceramic (2) calibrated in advance; S34. Calculate the proportionality coefficient μ1 = L2 / L T , L T is the full-scale displacement of the piezoelectric ceramic; S35. Calculate the voltage U2 required for the movement of the piezoelectric ceramic (2), where U2 = U T ×μ1, U T is the power supply voltage for piezoelectric ceramic control; S36. Control the D / A card through the power supply of the constant force value loading device to generate a voltage U2, and drive the piezoelectric ceramic (2) to generate a compensation displacement L2; S37. Repeat S31~S36 to keep the force application device point output a constant force value; S40. Output a constant force value at all force application device points; The force application device points of the half-mode balance and the loading head (21) include a negative Z-direction force application device point (22), a positive Y-direction force application device point (23), a positive Z-direction force application device point (24), and a negative Y-direction force application device point (25); Output a constant force value at all force application device points on the half-mode balance and the loading head (21) to complete the loading process of one loading point of the half-mode balance and the loading head (21); S50. Complete the ground static calibration of the half-mode balance; According to the pre-set loading sequence, complete the loading process of all loading points to obtain the ground static calibration working matrix of the half-mode balance.

2. The method for applying a constant force in the semi-module balance calibration system according to claim 1, wherein The force application value error of the constant force value loading device is less than or equal to 0.01%.

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