A method for reconstructing the force feedback signal of a hydraulic cylinder

Abstract

The present invention relates to the technical field of hydraulic control and testing, and discloses a method for reconstructing the force feedback signal of a hydraulic cylinder, including: collecting the actual displacement of a test specimen by using a displacement sensor of the hydraulic cylinder, and calculating the theoretical load value of the test specimen in combination with the theoretical stiffness of the test specimen; collecting the force feedback signal of the hydraulic cylinder by using a force sensor of the hydraulic cylinder, and performing band-pass filtering by using a band-pass filter; taking the actual displacement of the test specimen as the abscissa and the force feedback signal after band-pass filtering as the ordinate to draw a load-displacement hysteresis curve after band-pass filtering; obtaining the maximum displacement point on the load-displacement hysteresis curve after band-pass filtering to obtain the maximum true load exerted by the hydraulic cylinder on the test specimen, and reconstructing the load-time history actually exerted by the hydraulic cylinder on the test specimen; this method eliminates the influence of the friction force of the hydraulic cylinder on the force feedback signal, accurately restores the true load applied by the hydraulic cylinder to the test specimen, and improves the reliability of the test results.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic control and testing, and particularly relates to a method for reconstructing the force feedback signal of a hydraulic cylinder. Background Art

[0002] Hydraulic cylinders have the advantages of strong load capacity, fast response speed, etc., and are therefore widely used in various testing systems. For example, shock absorber dynamic simulation test benches, vehicle motion attitude simulation test benches, etc. all complete the loading test through hydraulic cylinders.

[0003] The operating principle of a hydraulic cylinder is to push the piston rod of the hydraulic cylinder to expand and contract in the cylinder body through the pressure formed by hydraulic oil, so as to complete the loading of the testing system. The piston rod of the hydraulic cylinder and the cylinder body usually adopt a sealed contact, and the friction force between the two is the main factor affecting the reliability of the testing system. A force sensor is usually arranged at the end of the hydraulic cylinder to collect the force signal during the loading process and feedback the force signal to the control system. The control system will compare the command signal and the feedback signal and then perform adjustment and compensation control commands. However, in the feedback force signal, in addition to the real load applied to the test specimen, it also includes the friction force between the piston rod and the cylinder body of the hydraulic cylinder, which will cause the control system to give incorrect loading instructions and increase the test error. In addition, various parameters of the test specimen are often calculated by using the force signal and displacement signal feedback by the hydraulic cylinder. For example, when performing a spring stiffness measurement test, the spring stiffness, an important parameter, can be obtained by the ratio of the force signal and displacement signal feedback by the hydraulic cylinder. However, when the feedback force signal contains the friction force of the hydraulic cylinder itself, it will directly affect the test result of the spring stiffness. Summary of the Invention

[0004] In view of the above deficiencies in the prior art, the present invention provides a method for reconstructing the force feedback signal of a hydraulic cylinder, which eliminates the influence of the friction force of the hydraulic cylinder itself from the force feedback signal of the hydraulic cylinder and restores the real load applied to the test specimen by the testing system, thereby solving the problems of large experimental error and low test accuracy caused by using a hydraulic cylinder for loading test in the prior art.

[0005] In order to achieve the above invention purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for reconstructing the force feedback signal of a hydraulic cylinder includes the following steps:

[0007] S1. Use the displacement sensor of the hydraulic cylinder to collect the actual displacement of the test specimen, and calculate the theoretical load value of the test specimen in combination with the theoretical stiffness of the test specimen;

[0008] S2. Use the force sensor of the hydraulic cylinder to collect the force feedback signal of the hydraulic cylinder;

[0009] Among them, the force feedback signal of the hydraulic cylinder includes the friction force of the hydraulic cylinder itself and the real load exerted by the hydraulic cylinder on the test specimen;

[0010] S3. Design a band-pass filter according to the loading frequency, and use the band-pass filter to perform band-pass filtering on the force feedback signal of the hydraulic cylinder to obtain the band-pass filtered force feedback signal;

[0011] S4. Taking the actual displacement of the test specimen as the abscissa and the band-pass filtered force feedback signal as the ordinate, plot the load-displacement hysteresis curve after band-pass filtering;

[0012] S5. Obtain the maximum displacement point on the load-displacement hysteresis curve after band-pass filtering to get the maximum real load exerted by the hydraulic cylinder on the test specimen;

[0013] S6. According to the maximum real load exerted by the hydraulic cylinder on the test specimen and the loading frequency, reconstruct the load time history actually exerted by the hydraulic cylinder on the test specimen to obtain the reconstructed force feedback signal of the hydraulic cylinder.

[0014] Furthermore, the calculation formula for the theoretical load value of the test specimen in step S1 is:

[0015] F t =K t ·Δx

[0016] Among them, F t represents the theoretical load value of the test specimen, K t represents the theoretical stiffness of the test specimen, and Δx represents the actual displacement of the test specimen.

[0017] Furthermore, step S3 specifically includes:

[0018] S31. Obtain the lower cut-off frequency and upper cut-off frequency of the loading frequency, set the filter order and select the filter type as a band-pass filter, and calculate the numerator coefficient and denominator coefficient of the transfer function of the band-pass filter;

[0019] S32. According to the numerator coefficient and denominator coefficient of the transfer function of the band-pass filter, use the band-pass filter to perform band-pass filtering on the force feedback signal of the hydraulic cylinder to obtain the band-pass filtered force feedback signal.

[0020] Furthermore, the calculation formulas for the numerator coefficient and denominator coefficient of the transfer function of the band-pass filter in step S31 are:

[0021] [b,a]=butter(N,f min ,f max ,′bandpass′)

[0022] Among them, b represents the numerator coefficient of the transfer function of the band-pass filter, a represents the denominator coefficient of the transfer function of the band-pass filter, butter represents the filter design function, N represents the filtering order, and f min represents the lower cut-off frequency of the loading frequency, and f max represents the upper cut-off frequency of the loading frequency, and bandpass represents the type of filter.

[0023] Furthermore, the force feedback signal after band-pass filtering in step S32 is:

[0024] F band = filter(b, a, F ori )

[0025] Among them, F band represents the force feedback signal after band-pass filtering, fikter represents the filtering function, and F ori represents the force feedback signal of the hydraulic cylinder.

[0026] Furthermore, the reconstructed force feedback signal of the hydraulic cylinder in step S6 is:

[0027] F r = A m ·sin(2·π·f·t)

[0028] Among them, F r represents the reconstructed force feedback signal of the hydraulic cylinder, A m represents the maximum load exerted by the hydraulic cylinder on the test specimen, sin represents the sine function, f represents the loading frequency, and t represents the loading time.

[0029] The present invention has the following beneficial effects:

[0030] A method for reconstructing the force feedback signal of a hydraulic cylinder proposed by the present invention eliminates the influence of the friction force of the hydraulic cylinder on the force feedback signal, and quickly and accurately restores the real load applied by the hydraulic cylinder to the test specimen, greatly improving the reliability of the test results; at the same time, this force signal reconstruction process is simple and convenient, easy to program, and can be quickly transplanted into the test data processing program for data processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic flow chart of a method for reconstructing the force feedback signal of a hydraulic cylinder proposed by the present invention;

[0032] Figure 2 is an axonometric schematic diagram of the experimental bench for measuring the dynamic stiffness of a spiral spring group driven by a hydraulic cylinder in the embodiment;

[0033] Figure 3Front view schematic diagram of the experimental bench for measuring the dynamic stiffness of the helical spring group driven by a hydraulic cylinder in the embodiment;

[0034] Figure 4 Structural schematic diagram of the helical spring group in the embodiment;

[0035] Figure 5 Structural schematic diagram of the hydraulic cylinder in the embodiment;

[0036] Figure 6 Displacement signal of the test system feedback by the displacement sensor of the hydraulic cylinder in the embodiment;

[0037] Figure 7 Theoretical load schematic diagram of the helical spring group in the embodiment;

[0038] Figure 8 Schematic diagram of the actual force feedback signal of the hydraulic cylinder in the embodiment;

[0039] Figure 9 Force feedback signal after traditional band-pass filtering in the embodiment;

[0040] Figure 10 Comparison schematic diagram of the theoretical load-displacement hysteresis curve, actual load-displacement hysteresis curve, and load-displacement hysteresis curve after band-pass filtering of the test specimen in the embodiment;

[0041] Figure 11 Comparison schematic diagram of the load-time history obtained after reconstruction and the theoretical load-time history of the test specimen in the embodiment. Specific implementation manner

[0042] The following describes the specific implementation manner of the present invention to facilitate those skilled in the art of the present technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation manner. For those of ordinary skill in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0043] As Figure 1 shown, a method for reconstructing the force feedback signal of a hydraulic cylinder includes the following steps S1 - S6:

[0044] S1. Use the displacement sensor of the hydraulic cylinder to collect the actual displacement of the test specimen, and combine the theoretical stiffness of the test specimen to calculate the theoretical load value of the test specimen.

[0045] Specifically, the calculation formula for the theoretical load value of the test specimen in step S1 is:

[0046] F t = K t ·Δx

[0047] Among them, F t represents the theoretical load value of the test specimen, K t represents the theoretical stiffness of the test specimen, and Δx represents the actual displacement of the test specimen.

[0048] In this embodiment, a set of helical springs with known stiffness is selected as the test specimen. The theoretical stiffness of the set of helical springs is 1.55 MN / m and it has good linearity. The set of helical springs is loaded by a hydraulic cylinder, that is, a test bench (testing system) for measuring the dynamic stiffness of the set of helical springs driven by a hydraulic cylinder is constructed to test the stiffness of the set of helical springs. By eliminating the influence of the self-friction of the hydraulic cylinder from the force feedback signal of the hydraulic cylinder, the true load applied to the test specimen by the testing system is restored, thereby reducing the error of the testing system and improving the test accuracy. Among them, the purpose of selecting a set of helical springs with known stiffness as the test specimen is: the theoretical load received by the set of helical springs can be calculated from the measured displacement (actual displacement) of the set of helical springs and the known theoretical stiffness, so that it can be used as a standard reference value. Otherwise, lacking a reference, it is impossible to compare the gap between the actual force signal feedback by the hydraulic cylinder and the theoretical value, and finally it is also impossible to verify whether the reconstructed load has truly eliminated the influence of friction.

[0049] As Figures 2 - 3 shown, they are respectively the axonometric view and the front view of the test bench for measuring the dynamic stiffness of the set of helical springs driven by a hydraulic cylinder; Figures 2 - 3 In it, 1 is the test bench base of the testing system, 2 is the column, 3 is the crossbeam, 4 is the piston rod of the hydraulic cylinder, 5 is the cylinder block of the hydraulic cylinder, 6 is the displacement sensor, 7 is the force sensor, 8 is the upper transition plate, 9 is the lower transition plate, 10 is the set of helical springs; and the test bench base provides support for the entire testing system; the frame structure composed of the column 2 and the crossbeam 3 provides the constraint reaction force for the testing system; the cylinder block 5 of the hydraulic cylinder is hung below the crossbeam 3, the piston rod 4 of the hydraulic cylinder is fitted inside the cylinder block 5, and at the same time, the inner cavity of the cylinder block 5 is filled with hydraulic oil, and the pressure formed by the hydraulic oil pushes the piston rod 4 of the hydraulic cylinder to move; the end of the piston rod 4 of the hydraulic cylinder is connected to the upper surface of the upper transition plate 8, a set of helical springs 10 is installed between the upper transition plate 8 and the lower transition plate 9, and the lower transition plate 9 is installed on the upper surface of the test bench base 1; and the set of helical springs 10 is composed of 8 helical steel springs installed side by side, and its structure is as Figure 4 shown; among them, the hydraulic cylinder includes the piston rod 4 of the hydraulic cylinder, the cylinder block 5 of the hydraulic cylinder, the displacement sensor 6, and the force sensor 7, and its structure is as Figure 5As shown; and the piston rod 4 of the hydraulic cylinder is driven by a hydraulic control system to move downward to apply pressure to the tested helical spring group 10, and the movement displacement of the piston rod 4 of the hydraulic cylinder is the same as that of the helical spring group 10, and the displacement amount can be directly obtained by the displacement sensor 6 at the tail of the cylinder block. The load applied by the hydraulic cylinder can be obtained by the force sensor 7 at the end of the piston rod of the hydraulic cylinder.

[0050] In addition, a standard sine wave loading command is adopted during the dynamic stiffness test of the helical spring group, as Figure 6 shown. Figure 6 shows the actual displacement of the helical spring group feedback by the displacement sensor at the tail of the cylinder block of the hydraulic cylinder during the test. Therefore, according to the actual displacement and the theoretical stiffness of the helical spring group, the theoretical value of the load received by the helical spring group can be calculated, as specifically shown in Figure 7 shown.

[0051] S2. Collect the force feedback signal of the hydraulic cylinder by using the force sensor of the hydraulic cylinder; wherein, the force feedback signal of the hydraulic cylinder includes the friction force of the hydraulic cylinder itself and the real load applied by the hydraulic cylinder on the test sample.

[0052] In this embodiment, due to the influence of the friction force of the hydraulic cylinder itself, the real force signal feedback by the force sensor at the end of the piston rod of the hydraulic cylinder is no longer a standard harmonic signal, as specifically shown in Figure 8 shown, and through analysis Figure 8 it can be known that the friction force action of the hydraulic cylinder can be divided into two stages, specifically: the first stage: when the movement speed is close to zero, and at the same time when the movement direction changes, the lubrication between the piston rod of the hydraulic cylinder and the cylinder block is insufficient, and the friction force of the hydraulic cylinder shows as static friction force. In this stage, the force feedback signal of the hydraulic cylinder will be suddenly lifted due to the superposition of the static friction force, and the force feedback signal is no longer continuous; the second stage, after the movement direction change is completed, the piston rod of the hydraulic cylinder starts to reciprocate in the cylinder block. After several initial reciprocating movements, an oil film is formed between the piston rod of the hydraulic cylinder and the cylinder block, and the two are in a fully lubricated state. In this stage, the friction force between the piston rod of the hydraulic cylinder and the cylinder block is viscous friction, and the magnitude of this friction force is related to the movement speed. After the force feedback signal of the hydraulic cylinder is superimposed with the viscous friction force, it will also be greater than the theoretical value; therefore, if the force feedback signal of the hydraulic cylinder is directly used to calculate the stiffness value of the tested helical spring group, its value is 3.2 MN / m, which is twice the theoretical value.

[0053] S3. Design a band-pass filter according to the loading frequency, and use the band-pass filter to perform band-pass filtering on the force feedback signal of the hydraulic cylinder to obtain the band-pass filtered force feedback signal.

[0054] Specifically, step S3 specifically includes S31 - S32:

[0055] S31. Obtain the lower cut-off frequency and upper cut-off frequency of the loading frequency, set the filter order and select the filter type as a band-pass filter, and calculate the numerator coefficients and denominator coefficients of the transfer function of the band-pass filter, that is:

[0056] [b,a]=butter(N,f min ,f max ,′bandpass′)

[0057] where b represents the numerator coefficients of the transfer function of the band-pass filter, a represents the denominator coefficients of the transfer function of the band-pass filter, butter represents the filter design function, N represents the filter order, f min represents the lower cut-off frequency of the loading frequency, f max represents the upper cut-off frequency of the loading frequency, and bandpass represents the filter type.

[0058] S32. According to the numerator coefficients and denominator coefficients of the transfer function of the band-pass filter, use the band-pass filter to perform band-pass filtering on the force feedback signal of the hydraulic cylinder to obtain the force feedback signal after band-pass filtering, that is:

[0059] F band =filter(b,a,F ori )

[0060] where F band represents the force feedback signal after band-pass filtering, fikter represents the filtering function, and F ori represents the force feedback signal of the hydraulic cylinder.

[0061] In this embodiment, there are many noise signals mixed in the force feedback signal of the hydraulic cylinder. Therefore, band-pass filtering is first performed on the force feedback. As Figure 9 shown, Figure 9 shows the force feedback signal after traditional band-pass filtering; since traditional band-pass filtering will remove most of the noise signals in the signal, although the signal curve will become smoother, it still cannot eliminate the influence of the friction force of the hydraulic cylinder. The amplitude of the force signal after band-pass filtering is still greater than the theoretical value. This is because the friction force of the hydraulic cylinder is caused by the reciprocating motion of the hydraulic cylinder. Therefore, the acting frequency of the friction force is the same as the motion frequency of the hydraulic cylinder. Therefore, traditional band-pass filtering can never eliminate the influence of the friction force. And if the force feedback signal after traditional band-pass filtering is used to calculate the stiffness value of the tested helical spring group, its value is 2.5 MN / m, which is 1.6 times the theoretical value.

[0062] In summary, in order to obtain accurate test results, it is necessary to further analyze and eliminate the influence of the friction force from the force feedback signal of the hydraulic cylinder to restore the true force condition of the tested specimen.

[0063] S4. With the actual displacement of the test specimen as the abscissa and the force feedback signal after band-pass filtering as the ordinate, plot the load-displacement hysteresis curve after band-pass filtering.

[0064] In this embodiment, the following analysis process is carried out to eliminate the friction force in order to obtain the true load exerted by the hydraulic cylinder on the test specimen, that is, the reconstructed force feedback signal of the hydraulic cylinder. The specific analysis is as follows:

[0065] First, with the actual displacement of the test system as the abscissa and the theoretical load value of the test specimen as the ordinate, plot the theoretical load-displacement hysteresis curve. That is, still using the helical spring group as the test specimen for the test, with the actual displacement of the test system as the abscissa and the theoretical value of the load of the helical spring group as the ordinate, plot the relationship curve between the two. The relationship curve is Figure 10 the theoretical load-displacement hysteresis curve in. Since the stiffness of the helical spring group has good linearity, the theoretical load-displacement hysteresis curve is a straight line segment, and the endpoints of this line segment are point E and point F;

[0066] Second, use the force sensor of the hydraulic cylinder to collect the force feedback signal of the hydraulic cylinder, and with the actual displacement of the test system as the abscissa and the force feedback signal of the hydraulic cylinder as the ordinate, plot the actual load-displacement hysteresis curve. That is, still using the helical spring group as the test specimen for the test, with the actual displacement of the test system as the abscissa and the force signal actually feedback by the hydraulic cylinder as the ordinate, plot the relationship curve between the two. The relationship curve is Figure 10 the actual load-displacement hysteresis curve in. Due to the influence of the friction force of the hydraulic cylinder, the two-dimensional curve between the actual displacement and the actual force feedback signal shows a rhombus. The four endpoints of the rhombus are respectively denoted as A, B, C, and D, corresponding to the moments when the motion acceleration is the largest; at the same time, affected by noise, the curve of the actual force feedback signal is not smooth; among them, the line segment AB shows a sharp drop in the force signal, and the line segment CD shows a sharp increase in the force signal, which is caused by the static friction force of the hydraulic cylinder; among them, the line segment BC and the line segment DA correspond to the process of the reciprocating motion of the piston rod of the hydraulic cylinder in the cylinder body. After several initial reciprocating motions, an oil film is formed between the piston rod and the cylinder body of the hydraulic cylinder, and the two are in a fully lubricated state. In this stage, the friction force between the piston rod and the cylinder body is viscous friction, and the magnitude of this friction force is related to the motion speed; that is, since the system friction force is superimposed on the force feedback signal of the hydraulic cylinder, the amplitude of the force signal is greater than the theoretical value.

[0067] Therefore, on the basis of analyzing the above-mentioned theoretical load-displacement hysteresis curve and the actual load-displacement hysteresis curve, it is proposed to plot the load-displacement hysteresis curve after band-pass filtering in order to reconstruct the force feedback signal of the hydraulic cylinder, so as to eliminate the influence of friction. The specific operation process is as follows: Still use the spiral spring group as the test sample for the test. Take the actual displacement of the test system as the abscissa and the force feedback signal after band-pass filtering as the ordinate, and plot the relationship curve between the two. The relationship curve is Figure 10 the load-displacement hysteresis curve after band-pass filtering in Figure 10 . Due to the data smoothing effect of band-pass filtering, the relationship curve between the force feedback signal after band-pass filtering and the actual displacement changes from the original sharp rhombus ABCD to a smooth ellipse; in addition, since the traditional band-pass filtering method cannot completely eliminate the influence of friction, the maximum value of the force signal on the ellipse is still greater than the theoretical value.

[0068] S5. Obtain the maximum displacement point on the load-displacement hysteresis curve after band-pass filtering to obtain the maximum true load exerted by the hydraulic cylinder on the test sample.

[0069] In this embodiment, from Figure 10 it can also be known that the line segment EF formed by the theoretical load-displacement hysteresis curve of the spiral spring group is exactly the chord length of the ellipse formed by the load-displacement hysteresis curve after band-pass filtering. The abscissas of the two endpoints of this chord length correspond to the maximum value of the actual displacement, and the ordinates of the two endpoints of this chord length correspond to the maximum value of the true load received by the test sample. The reason is that since the moving speed corresponding to the moment of the maximum displacement is zero, and the friction force of the hydraulic cylinder is also zero when the moving speed is zero; therefore, the maximum true load exerted by the hydraulic cylinder on the test sample can be obtained corresponding to the displacement maximum point on the load-displacement hysteresis curve after band-pass filtering.

[0070] S6. According to the maximum true load exerted by the hydraulic cylinder on the test sample and the loading frequency, reconstruct the load time history actually exerted by the hydraulic cylinder on the test sample to obtain the reconstructed force feedback signal of the hydraulic cylinder.

[0071] Specifically, the reconstructed force feedback signal of the hydraulic cylinder in step S6 is as follows:

[0072] F r =A m ·sin(2·π·f·t)

[0073] where F r represents the reconstructed force feedback signal of the hydraulic cylinder, A m represents the maximum load exerted by the hydraulic cylinder on the test sample, sin represents the sine function, f represents the loading frequency, and t represents the loading time.

[0074] In this embodiment, the force feedback signal of the hydraulic cylinder obtained after reconstruction is compared with the theoretical value of the force on the test specimen as shown in Fig. 11, and it can be seen that the two completely coincide. Therefore, by using the method for reconstructing the force feedback signal of the hydraulic cylinder proposed in the present invention, the influence of the friction force of the hydraulic cylinder on the force feedback signal can be eliminated, and the true load exerted by the hydraulic cylinder on the test specimen can be obtained, thereby improving the test accuracy.

[0075] In summary, a method for reconstructing the force feedback signal of a hydraulic cylinder proposed in the present invention eliminates the influence of the friction force of the hydraulic cylinder on the force feedback signal, quickly and accurately restores the true load applied by the hydraulic cylinder to the test specimen, and greatly improves the reliability of the test results. At the same time, this force signal reconstruction process is simple and convenient, easy to program, and can be quickly transplanted into the test data processing program for data processing.

[0076] In the present invention, specific embodiments are used to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation on the present invention.

[0077] Those of ordinary skill in the art will realize that the embodiments described herein are for helping the reader understand the principle of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations that do not depart from the essence of the present invention based on the technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the present invention.

Claims

1. A method for reconstructing a force feedback signal of a hydraulic cylinder, characterized in that: The following steps are involved: S1. Use the displacement sensor of the hydraulic cylinder to collect the actual displacement of the test sample, and calculate the theoretical load value of the test sample in combination with the theoretical stiffness of the test sample; S2, using the force sensor of the hydraulic cylinder to collect the force feedback signal of the hydraulic cylinder; Among them, the force feedback signal of the hydraulic cylinder includes the friction force of the hydraulic cylinder itself and the real load of the hydraulic cylinder acting on the test sample; S3. Design a bandpass filter according to the loading frequency, and use the bandpass filter to perform bandpass filtering on the force feedback signal of the hydraulic cylinder to obtain a force feedback signal after bandpass filtering, specifically: S31, obtaining the lower cutoff frequency and the upper cutoff frequency of the loading frequency, setting the filter order and selecting the filter type as a bandpass filter, and calculating the transfer function numerator coefficient and the transfer function denominator coefficient of the bandpass filter, that is: in, represents the numerator coefficient of the transfer function of the bandpass filter, represents the denominator coefficient of the transfer function of the bandpass filter, represents the filter design function, represents the filter order, Indicates the lower cutoff frequency of the loading frequency, Indicates the upper cutoff frequency of the loading frequency, Indicates the type of filter; S32, according to the transfer function numerator coefficient and the transfer function denominator coefficient of the bandpass filter, the force feedback signal of the hydraulic cylinder is bandpass filtered by using the bandpass filter to obtain the force feedback signal after bandpass filtering, that is: in, represents the force feedback signal after bandpass filtering, represents the numerator coefficient of the transfer function of the bandpass filter, represents the denominator coefficient of the transfer function of the bandpass filter, represents the filter function, Represents the force feedback signal of the hydraulic cylinder; S4. Using the actual displacement of the test sample as the abscissa and the force feedback signal after bandpass filtering as the ordinate, draw a load-displacement hysteresis curve after bandpass filtering; S5, obtaining the maximum displacement point on the load-displacement hysteresis curve after bandpass filtering, and obtaining the maximum true load of the hydraulic cylinder acting on the test sample; S6. According to the maximum true load and loading frequency of the hydraulic cylinder acting on the test sample, the load time history of the hydraulic cylinder actually acting on the test sample is reconstructed to obtain a reconstructed force feedback signal of the hydraulic cylinder.

2. The method for reconstructing the force feedback signal of a hydraulic cylinder according to claim 1, characterized in that: The calculation formula of the theoretical load value of the test sample in step S1 is: in, Indicates the theoretical load value of the test specimen, represents the theoretical stiffness of the test specimen, Indicates the actual displacement of the test specimen.

3. The method for reconstructing the force feedback signal of a hydraulic cylinder according to claim 2, characterized in that: The force feedback signal of the hydraulic cylinder reconstructed in step S6 is: in, represents the reconstructed force feedback signal of the hydraulic cylinder, Indicates the maximum load of the hydraulic cylinder on the test specimen, represents the sine function, Indicates the loading frequency, Indicates loading time.

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