A method for applying constant force to a half-module balance calibration system

Abstract

The present invention belongs to the technical field of multi-component aerodynamic load measurement sensors, and discloses a method for applying constant force to a half-module balance calibration system. The method for applying constant force includes installing a constant force value loading device; performing precise force loading; performing real-time displacement compensation; maintaining a constant force value output at all force-applying device points; and completing the ground static calibration of the half-module balance. The method for applying constant force 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, the steel spring inevitably generates creep displacement while waiting for the arrival of multiple force-applying device points. The applied force value corresponding to the creep is synchronously measured by a high-precision force sensor, and the corresponding compensation displacement of the piezoelectric ceramic is calculated. The creep displacement is dynamically compensated in real time to ensure that the constant force value loading device is always at the required constant force value, thereby achieving high-precision calibration of the half-module balance.

Description

Technical Field

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

[0002] The half-mold balance is the core force-measuring device for wind tunnel half-mold testing. Prior to conducting wind tunnel half-mold tests, a ground-based static calibration of the half-mold balance is required using a half-mold balance calibration system. This system then generates a working matrix of applied force F and bridge output voltage U. This calibration system typically uses a ground-based axis calibration method and does not reset during the calibration process. Therefore, the accuracy of the calibration data depends on the accuracy of the force-applying device. For large forces (generally greater than 20,000N), the half-mold balance calibration system consists of a steel spring, an electric cylinder, and a high-precision force sensor. The tension is controlled by the electric cylinder's telescopic displacement. The electric cylinder stretches the steel spring, which in turn generates a corresponding tension, which is measured using a high-precision force sensor.

[0003] In a semi-modular balance calibration system consisting of a steel spring, an electric cylinder, and a high-precision force sensor, the force magnitude is simplified by Hooke's law, resulting in a tensile force F = kx (k is the spring constant, x is the distance the spring is stretched). However, due to material inhomogeneity during the steel spring manufacturing process and subsequent rotation at the joint during installation, precise force calculations based on Hooke's law are not possible. Therefore, a one-to-one calibration of each spring set is required upfront. During calibration, a stepwise force F is applied within the required force range, and the corresponding displacement L is recorded. Finally, a functional relationship f(F, L) is fitted between the force F and the displacement L, which is then used to determine the spring displacement when force is applied.

[0004] An electric cylinder is typically composed of a servo motor, a reducer, and a leadscrew. After power is applied, the servo motor pulse count is calculated based on the required displacement combined with the leadscrew lead. Typically, an encoder provides feedback on the cylinder displacement. However, the displacement accuracy of this type of cylinder is limited to 0.02mm due to mechanical errors (a certain gap must be left when installing the reducer) and encoder measurement errors. This limits the maximum control accuracy to 0.02mm, making it impossible to further improve this accuracy through internal improvements. Constant force devices use external feedback to improve cylinder displacement control accuracy. This involves installing a grating ruler on the cylinder body, measuring the cylinder displacement in real time, and feeding it back to the servo motor in the cylinder. The servo motor continues to operate until the set cylinder displacement and the actual cylinder displacement are equal, resulting in a closed-loop cylinder achieving a control accuracy of 0.002mm.

[0005] When the closed-loop electric cylinder reaches the set position, the entire system reaches its ideal state. However, because the semi-modular balance is a multi-component force sensor, multiple components simultaneously apply the calibration force during the calibration process. The force at each point varies depending on the designed range, so the arrival time of the force at each point cannot be guaranteed to be simultaneous. The points that arrive earlier need to maintain a constant force for a certain period of time until all points have completed high-precision force application and unified data collection. Because the spring in the combination of steel spring, closed-loop electric cylinder, and high-precision force sensor inevitably creeps, a slight displacement occurs during the waiting period. This displacement corresponds to a corresponding force value, making it impossible for each point of the force-applying device to maintain the ideal state of constant force.

[0006] Creep is the tendency of a solid material to slowly and permanently move or deform under stress. It occurs as a result of prolonged exposure to stresses below the material's yield strength, and creep often intensifies with increasing temperature. Creep in metallic materials is influenced by multiple factors, primarily metallurgy, microstructure, and external conditions. Metallurgical factors such as alloying elements, grain size, impurities, and phase transformations affect creep resistance. Fine and coarse grains have opposite effects at room and high temperatures. Grain boundary sliding is minimal at room temperature, but can account for the majority of total creep at high temperatures. External conditions include temperature, load, and heat treatment. The higher the temperature and the heavier the load, the greater the creep. The uniformity of the heat treatment also affects the creep morphology. Steel springs are generally made from die steel, and creep occurs throughout the entire force application process. This is unavoidable, and the only way to overcome the force errors caused by creep is to find ways to overcome them.

[0007] Currently, there is an urgent need to develop a method for applying constant force to a half-module 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 constant force to a half-module balance calibration system, so as to overcome the defects of the prior art.

[0009] The method for applying constant force to a half-module balance calibration system of the present invention comprises the following steps:

[0010] S10. Install a constant force loading device;

[0011] The constant force loading device includes an electric cylinder, piezoelectric ceramics 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 half-mold balance and the corresponding force-applying device point on the loading head, and a force sensor is provided on the steel wire rope;

[0012] S20. Perform precise force loading;

[0013] S21. Calculate the displacement L1 of the steel spring. The required force F0 is calculated using the functional relationship f(F1, L1) between the previously calibrated force value F1 and the displacement L1 of the steel spring to obtain the required displacement L1 of the steel spring and the corresponding displacement of the electric cylinder.

[0014] S22 drives the electric cylinder to perform telescopic movement to reach the electric cylinder displacement, causing the steel spring to produce a displacement L1;

[0015] S23 records the measured value F1 of the force sensor;

[0016] S24. Calculate the load error △F1 = F1-F0;

[0017] S25. Determine whether the load error △F1 satisfies the preset error range;

[0018] S26. If the load error △F1 does not meet the pre-set error range, repeat steps S21 to S25 until the real-time force value measured by the force sensor meets the error range;

[0019] S30. Perform real-time displacement compensation;

[0020] Control the piezoelectric ceramics to perform real-time displacement compensation, overcome the creep of the steel spring through the piezoelectric ceramics, and maintain a constant force output. The specific steps are as follows:

[0021] S31 records the force sensor measurement value F2;

[0022] S32. Calculate the creep displacement of the steel spring: △F2=F2-F1;

[0023] S33 calculates the compensation displacement L2 of the piezoelectric ceramic;

[0024] The compensation displacement L2 of the piezoelectric ceramic is calculated by the functional relationship f(F2, L2) between the force value F2 and the displacement L2 of the piezoelectric ceramic calibrated in the early stage;

[0025] S34. Calculate the proportional coefficient μ1=L2 / L T , L T is the full-scale displacement of the piezoelectric ceramic;

[0026] S35. Calculate the voltage U2 required for the piezoelectric ceramic to move, U2=U T ×μ1,U T Control the power supply voltage for the piezoelectric ceramics;

[0027] S36. The power supply of the constant force loading device controls the D / A card to generate a voltage U2, which drives the piezoelectric ceramic to generate a compensation displacement L2;

[0028] S37. Repeat S31 to S36 to maintain a constant force output at the force application point.

[0029] S40. Maintain constant force output at all force application points;

[0030] The force application device points of the half-mold balance and the loading head include a negative Z-direction force application device point, a positive Y-direction force application device point, a positive Z-direction force application device point, and a negative Y-direction force application device point;

[0031] All force-applying device points on the half-mold balance and the loading head maintain a constant force output, completing the loading process of one loading point of the half-mold balance and the loading head;

[0032] S50. Complete the static calibration of the half-module balance on the ground;

[0033] According to the preset loading sequence, the loading process of all loading points is completed to obtain the ground static calibration working matrix of the semi-module balance.

[0034] Furthermore, the applied force error of the constant force loading device is less than or equal to 0.01%.

[0035] The method for applying constant force in the half-module balance calibration system of the present invention calculates the electric cylinder displacement according to the magnitude of the applied force. After the corresponding electric cylinder displacement is completed by the closed-loop control of the driving electric cylinder, the steel spring inevitably produces creep displacement while waiting for the arrival of multiple force-applying device points. The applied force value corresponding to the creep is synchronously measured by a high-precision force sensor, and the corresponding compensation displacement of the piezoelectric ceramic is calculated. The creep displacement is dynamically compensated in real time to ensure that the constant force loading device is always at the required constant force value, thereby achieving high-precision calibration of the half-module balance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A flow chart of a method for applying a constant force to a half-module balance calibration system of the present invention;

[0037] Figure 2 A schematic structural diagram of a constant force loading device used in a method for applying a constant force to a half-module balance calibration system of the present invention;

[0038] Figure 3 Schematic diagram of the position of the force applying device of the method for applying constant force to the half-module balance calibration system of the present invention.

[0039] In the figure, 1. Steel spring; 2. Piezoelectric ceramic; 3. Electric cylinder; 4. Force sensor;

[0040] 21. Half-mold balance and loading head; 22. Negative Z-direction force application device point; 23. Positive Y-direction force application device point; 24. Positive Z-direction force application device point; 25. Negative Y-direction force application device point. DETAILED DESCRIPTION

[0041] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0042] Example: Figure 1 As shown, the method for applying constant force to the half-module balance calibration system of this embodiment includes the following steps:

[0043] S10. Install a constant force loading device;

[0044] like Figure 2 As shown, the constant force 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-applying device point on the half-mold balance and the loading head 21, and a force sensor 4 is provided on the steel wire rope;

[0045] S20. Perform precise force loading;

[0046] S21. Calculate the displacement L1 of steel spring 1. Calculate the required displacement L1 of steel spring 1 and the corresponding displacement of the electric cylinder by applying the required force F0 using the functional relationship f(F1, L1) between the previously calibrated force value F1 and displacement L1 of steel spring 1.

[0047] S22 drives the electric cylinder 3 to perform telescopic movement to reach the electric cylinder displacement, so that the steel spring 1 produces a displacement L1;

[0048] S23 records the measured value F1 of the force sensor 4;

[0049] S24. Calculate the load error △F1 = F1-F0;

[0050] S25. Determine whether the load error △F1 satisfies the preset error range;

[0051] S26. If the load error △F1 does not meet the pre-set error range, repeat steps S21 to S25 until the real-time force value measured by the force sensor 4 meets the error range;

[0052] S30. Perform real-time displacement compensation;

[0053] Control the piezoelectric ceramic 2 to perform real-time displacement compensation, overcome the creep of the steel spring 1 through the piezoelectric ceramic 2, and maintain a constant force output. The specific steps are as follows:

[0054] S31 records the force sensor 4 measured value F2;

[0055] S32. Calculate the creep displacement of the steel spring 1 △F2=F2-F1;

[0056] S33 calculates the compensation displacement L2 of the piezoelectric ceramic 2;

[0057] The compensation displacement L2 of the piezoelectric ceramic 2 is calculated by using the functional relationship f(F2, L2) between the force value F2 and the displacement L2 of the piezoelectric ceramic 2 calibrated in the early stage;

[0058] S34. Calculate the proportional coefficient μ1=L2 / L T , L T is the full-scale displacement of the piezoelectric ceramic;

[0059] S35. Calculate the voltage U2 required for the movement of the piezoelectric ceramic 2, U2=U T ×μ1,U T Control the power supply voltage for the piezoelectric ceramics;

[0060] S36. The power supply of the constant force loading device controls the D / A card to generate a voltage U2, which drives the piezoelectric ceramic 2 to generate a compensation displacement L2;

[0061] S37. Repeat S31 to S36 to maintain a constant force output at the force application point.

[0062] S40. Maintain constant force output at all force application points;

[0063] like Figure 3 As shown, the force applying device points of the half-mold balance and the loading head 21 include a negative Z-direction force applying device point 22, a positive Y-direction force applying device point 23, a positive Z-direction force applying device point 24 and a negative Y-direction force applying device point 25;

[0064] All the force-applying device points on the half-mold balance and the loading head 21 maintain a constant force output, completing the loading process of one loading point of the half-mold balance and the loading head 21;

[0065] S50. Complete the static calibration of the half-module balance on the ground;

[0066] According to the preset loading sequence, the loading process of all loading points is completed to obtain the ground static calibration working matrix of the semi-module balance.

[0067] Furthermore, the applied force error of the constant force loading device is less than or equal to 0.01%.

[0068] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the description and implementation methods. For those familiar with the art, all features disclosed in the present invention, or all steps in the disclosed methods or processes, except for mutually exclusive features and / or steps, can be combined in any way without departing from the principles of the present invention. The present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for applying constant force to a half-module balance calibration system, characterized in that: The method of applying a constant force comprises the following steps: S10. Install a constant force loading device; The constant force loading device comprises 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 point on the half-mold balance and the loading head (21), and a force sensor (4) is provided on the steel wire rope; S20. Perform precise force 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 by applying the force F0 to the steel spring (1) through the functional relationship f(F1, L1) between the force value F1 and the displacement L1 of the steel spring (1) calibrated in advance; S22 drives the electric cylinder (3) to perform telescopic movement to reach the electric cylinder displacement, so that the steel spring (1) produces 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 satisfies the preset error range; S26. If the load error △F1 does not meet the preset error range, repeat steps S21 to S25 until the real-time force value measured by the force sensor (4) meets the error range; S30. Perform real-time displacement compensation; The piezoelectric ceramic (2) is controlled to perform real-time displacement compensation, and the creep of the steel spring (1) is overcome by the piezoelectric ceramic (2) to maintain a constant force output. The specific steps are as follows: S31. Record the force sensor (4) measurement value F2; S32. Calculate the creep displacement of the steel spring (1): △F2=F2-F1; S33. Calculate the compensation displacement L2 of the piezoelectric ceramic (2); The compensation displacement L2 of the piezoelectric ceramic (2) is calculated by using the functional 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 Control the power supply voltage for the piezoelectric ceramics; S36. The power supply of the constant force loading device controls the D / A card to generate a voltage U2, which drives the piezoelectric ceramic (2) to generate a compensation displacement L2; S37. Repeat S31 to S36 to maintain a constant force output at the force application point. S40. Maintain constant force output at all force application points; The force applying device points of the half-mold balance and the loading head (21) include a negative Z-direction force applying device point (22), a positive Y-direction force applying device point (23), a positive Z-direction force applying device point (24) and a negative Y-direction force applying device point (25); All force application device points on the half-mold balance and the loading head (21) maintain a constant force output, completing the loading process of one loading point of the half-mold balance and the loading head (21); S50. Complete the static calibration of the half-module balance on the ground; According to the preset loading sequence, the loading process of all loading points is completed to obtain the ground static calibration working matrix of the semi-module balance.

2. The method for applying constant force to a half-module balance calibration system according to claim 1, characterized in that: The applied force error of the constant force loading device is less than or equal to 0.01%.

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