Segmented modeling and parameter identification method for asymmetric electro-hydraulic actuator system

Abstract

The invention discloses a segmented modeling and parameter identification method for an asymmetric electro-hydraulic actuator system. The method comprises the following steps that the asymmetric electro-hydraulic actuator system is modularly split into a motor control pump model and a hydraulic transmission model; aiming at the characteristics of the two sub-modules of the motor pump control model and the hydraulic transmission model, respectively establishing mathematical models, and solving corresponding transfer functions; input excitation is applied to each sub-module, output signals are collected, a model parameter relation matrix is established, Bode frequency domain characteristic fitting is carried out on the motor pump control module, an input and output relation is established for the hydraulic transmission model, time domain parameter fitting is carried out, and segmented identification is achieved until the preset identification precision requirement is met; and integrating the sub-module models of which the identification precision is completed, and constructing a complete identification model of the asymmetric electro-hydraulic actuator system. According to the method, the nonlinear characteristic of each module can be accurately identified, the dynamic performance of the system is optimized, and the control precision of the system is improved.

Description

Technical Field

[0001] This invention relates to the field of hydraulic transmission and motor control, and in particular to a method for segmented modeling and parameter identification of asymmetric electro-hydraulic actuator systems. Background Technology

[0002] Asymmetric electro-hydraulic actuator systems are widely used in industrial robots, exoskeletons, and aerospace due to their high power density and energy efficiency. These systems integrate motor servo control and hydraulic drive, exhibiting strong coupling characteristics across multiple physical domains. Their dynamic performance is influenced by a combination of factors, including motor characteristics, hydraulic viscous damping, hydraulic bulk modulus, and internal leakage, which limits high-performance control. Therefore, accurate modeling and parameter identification of asymmetric electro-hydraulic actuator systems are crucial for improving their dynamic performance.

[0003] Traditional modeling methods typically rely on physical laws or simplified linearization, employing linear models to describe asymmetric electro-hydraulic actuator systems. However, nonlinear parameters within the system, such as the electromagnetic torque of the servo motor, the internal leakage of the gear pump, and the hydraulic bulk modulus, prevent these methods from accurately reflecting the actual dynamic response of the system under high-precision control or various operating conditions. Furthermore, traditional identification methods often treat the asymmetric electro-hydraulic actuator system as a whole, lacking in-depth analysis of the complex coupling effects between the servo motor, hydraulic pump, hydraulic cylinder, and load transmission chain, thus limiting the accuracy of the identification results. To improve the accuracy of system modeling and identification, it is crucial to conduct in-depth research on the coupling relationships between each sub-module and to perform separate analysis of nonlinear characteristics.

[0004] Therefore, there is an urgent need to provide a novel method for segmented modeling and parameter identification of asymmetric electro-hydraulic actuator systems to solve the above problems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a segmented modeling and parameter identification method for an asymmetric electro-hydraulic actuator system, which can accurately identify the nonlinear characteristics of each module, optimize the dynamic performance of the system and improve the control accuracy of the system.

[0006] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is: to provide a segmented modeling and parameter identification method for an asymmetric electro-hydraulic actuator system, comprising the following steps:

[0007] S1: Modularly decompose the asymmetric electro-hydraulic actuator system into a motor-controlled pump model and a hydraulic transmission model;

[0008] S2: Based on the characteristics of the two sub-modules, namely the motor-controlled pump model and the hydraulic transmission model, establish mathematical models for each and derive the corresponding transfer functions.

[0009] S3: Apply input excitation and collect output signals to each submodule, establish the model parameter relationship matrix, and perform Bode frequency domain characteristic fitting on the motor pump control module and establish input-output relationship and time domain parameter fitting on the hydraulic transmission model to achieve segmented identification until the preset identification accuracy requirements are met.

[0010] S4: Integrate the sub-module models that have achieved the required identification accuracy to construct a complete identification model for the asymmetric electro-hydraulic actuator system.

[0011] In a preferred embodiment of the present invention, the motor pump control model includes a servo driver, a servo motor, and a gear pump, wherein the servo motor voltage signal is used as the input variable and the actual speed of the gear pump is used as the output variable.

[0012] In a preferred embodiment of the present invention, the hydraulic transmission model includes a gear pump, an asymmetric hydraulic cylinder, a check valve, a hydraulically controlled check valve, and a relief valve, wherein the actual rotational speed of the gear pump is used as the input variable, and the piston displacement of the asymmetric hydraulic cylinder is used as the output variable.

[0013] In a preferred embodiment of the present invention, in step S2, the transfer function of the motor-controlled pump model is:

[0014] Using the servo motor voltage as input and the actual speed of the gear pump as output, the transfer function expression of the motor-pump control module is obtained as follows:

[0015]

[0016] In the formula, This is the transfer function for the motor-controlled pump module; The identification coefficient is N; N is the actual rotational speed of the gear pump.

[0017] Voltage balance equation for servo motors: In the formula, This is the total resistance of the motor armature; This refers to the armature current of the motor. For the armature inductance of the motor; This is the electromagnetic torque coefficient of the motor.

[0018] In a preferred embodiment of the present invention, in step S2, the transfer function of the hydraulic transmission model is:

[0019] Using the actual rotational speed of the gear pump as input and the displacement of the asymmetric hydraulic cylinder as output, the transfer function expression of the hydraulic transmission module is obtained as follows:

[0020]

[0021] In the formula, This is the transfer function for the hydraulic transmission module; X represents the identification coefficient; X represents the displacement data of the asymmetric hydraulic cylinder; and N represents the actual rotational speed data of the gear pump.

[0022] In a preferred embodiment of the present invention, in step S3, for the motor-pump control module, the input excitation is a sinusoidal voltage signal within the operating frequency range of the motor-pump control module, and the output signal is the actual speed response of the gear pump within that frequency range. The Bode plot and model parameter relationship matrix are constructed as follows:

[0023]

[0024] In the formula, , which is the parameter matrix of the motor-pump control module to be identified; N is the input sinusoidal voltage matrix; N is the output actual rotational speed matrix;

[0025] Based on the aforementioned least squares method, frequency domain transfer function fitting is performed on the Bode plot. By minimizing the error between the experimental data and the predicted transfer function value, the transfer function is continuously adjusted. Four undetermined parameters are used to gradually approximate the experimentally measured Bode map with the fitted Bode map until the preset recognition accuracy requirements are met.

[0026] In a preferred embodiment of the present invention, in step S3, for the hydraulic transmission module, the input excitation is the actual speed signal of the gear pump, and the output signal is the piston displacement signal of the asymmetric hydraulic cylinder. The model parameter relationship matrix is ​​constructed as follows:

[0027]

[0028] In the formula, , where is the parameter matrix of the hydraulic transmission module to be identified; N is the input actual speed matrix; and X is the output displacement matrix.

[0029] Based on the aforementioned least squares method, the input-output time-domain transfer function is fitted. By minimizing the error between the experimental data and the predicted value of the transfer function, the parameters in the transfer function are continuously adjusted. Four parameters are set to allow the fitted displacement curve to gradually approximate the experimentally measured displacement curve until the preset identification accuracy requirements are met.

[0030] In a preferred embodiment of the present invention, in step S3, when the identification accuracy requirement is met, parameter identification is completed and the optimal parameter matrices of the motor-controlled pump module and the hydraulic transmission module are obtained respectively: , Output the optimal transfer function for each model: , .

[0031] Furthermore, in step S4, the identification model of the asymmetric electro-hydraulic actuator system is a combination of a motor-controlled pump model and a hydraulic transmission model, and its transfer function can be expressed as a series structure of the transfer functions of two sub-modules, that is: In the formula, It is the transfer function of an asymmetric electro-hydraulic actuator system.

[0032] The beneficial effects of this invention are:

[0033] (1) The complex asymmetric electro-hydraulic actuator system is divided into a motor-controlled pump submodule and a hydraulic transmission submodule. By independently modeling and identifying each submodule, the dynamic performance of each submodule can be described more accurately. This method helps to accurately identify the nonlinear characteristics of each module, optimize the dynamic performance of the system, and improve the control accuracy of the system;

[0034] (2) Identifying sub-modules in both the frequency and time domains allows for a more accurate description of the system's dynamic characteristics. Frequency domain identification captures the response characteristics of the motor-pump control system at different frequencies, aiding in the analysis of system stability and frequency response; while time domain identification more effectively identifies the transient response and nonlinear dynamic behavior of the hydraulic transmission system. Combining these two methods not only improves the system's accuracy and stability but also enhances its adaptability to different operating conditions such as speed variations and load changes.

[0035] (3) Due to the nonlinear coupling characteristics of asymmetric electro-hydraulic actuator systems, segmented decoupling modeling can not only improve the model fitting accuracy, but also reduce the complexity of parameter identification, making the identification process more stable and the parameter estimation results more reliable, thus avoiding overfitting or ill-posed problems caused by using a single high-order model. At the same time, each segment identification can be performed independently, possessing good parallelism and scalability;

[0036] (4) By analyzing the differences between the simulation model and the actual results, not only can the accuracy of the model and its ability to reflect the real behavior of the system be significantly improved, but also a solid theoretical foundation can be provided for subsequent system prediction, parameter optimization and fault prediction. The identified model can be effectively used for simulation evaluation and control design, reducing experimental costs and improving the reliability and maintenance efficiency of system operation. Attached Figure Description

[0037] Figure 1 This is a flowchart illustrating the segmented modeling and parameter identification method for an asymmetric electro-hydraulic actuator system according to the present invention.

[0038] Figure 2 This is a schematic diagram of the platform architecture of an asymmetric electro-hydraulic actuator system;

[0039] Figure 3This is a schematic diagram of an asymmetric electro-hydraulic actuator system;

[0040] Figure 4 This is the Bode plot calculated from the motor-controlled pump model;

[0041] Figure 5 These are the experimental and simulation Bode fitting plots of the motor-controlled pump model under frequency domain identification;

[0042] Figure 6 This is a curve of the displacement output of the asymmetric hydraulic cylinder at the actual rotational speed of the hydraulic transmission model.

[0043] Figure 7 These are the displacement fitting curves from the hydraulic transmission model experiments and simulations.

[0044] The components in the attached diagram are labeled as follows: 1. Servo motor, 2. Gear pump, 31 (32) Check valve, 41 (42) Hydraulic check valve, 51 (52) Overflow valve, 53. Safety overflow valve, 6. Oil filter, 71 (72) Oil tank, 81 (82) Accumulator, 91 (92) Pressure sensor, 10. Asymmetric hydraulic cylinder, 11. Displacement sensor, 12. Load. Detailed Implementation

[0045] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0046] First, a brief explanation of the platform architecture and working principle of the asymmetric electro-hydraulic actuator system will be given:

[0047] The asymmetric electro-hydraulic actuator system includes an asymmetric electro-hydraulic actuator and a host computer, etc., wherein, for example Figure 2 As shown, the asymmetric electro-hydraulic actuator includes: a servo motor 1, a gear pump 2, a check valve 31, a hydraulically controlled check valve 41, an accumulator 81, a relief valve 51, an asymmetric hydraulic cylinder 10, a displacement sensor 11, a pressure sensor 91, and hydraulic pipelines, etc. The displacement sensor 11 monitors the piston displacement value of the asymmetric hydraulic cylinder 10, and the pressure sensor 91 monitors the pressure value of the hydraulic oil circuit.

[0048] The schematic diagram of the asymmetric electro-hydraulic actuator system is as follows: Figure 3As shown, the specific working principle is as follows: Servo motor 1 drives gear pump 2 through a coupling to achieve bidirectional output of hydraulic energy. When servo motor 1 rotates forward, gear pump 2 supplies oil to the rodless chamber of asymmetric hydraulic cylinder 10, pushing the piston rod to extend. At the same time, the oil in the rod chamber flows back to the oil tank 71 through hydraulically controlled check valve 41. The return oil pressure is regulated by relief valve 51 and is drawn from the oil tank 71 through oil filter 6 via check valve 32 to prevent negative pressure. When servo motor 1 rotates in reverse, gear pump 2 supplies oil to the rod chamber, pushing the piston rod to retract. The oil in the rodless chamber flows back to the oil tank 71 through hydraulically controlled check valve 42. Check valve 31 draws oil from the low-pressure side to maintain stable system pressure. The return oil pressure is regulated by relief valve 52. The system is equipped with accumulators 81 and 82 to buffer pressure fluctuations in the hydraulic circuit and improve operational stability. A safety relief valve 53 is also provided. When the system pressure exceeds the preset upper limit, the oil flows back to the oil tank 72 through it to protect system safety. An asymmetric hydraulic cylinder 10 drives a load 12 in reciprocating motion. It is equipped with a displacement sensor 11 and pressure sensors 91 and 92, which are used to collect real-time piston displacement and hydraulic circuit pressure values, respectively. A host computer sends control commands to the controller, which dynamically adjusts the operating state of the servo motor based on the displacement and pressure feedback signals, achieving electromechanical-hydraulic closed-loop control.

[0049] The working mechanism of the asymmetric electro-hydraulic actuator system is that the input voltage signal of the servo motor adjusts the actual output speed of the gear pump, thereby driving the displacement output of the asymmetric hydraulic cylinder, forming an energy conversion and coupling process from voltage drive to hydraulic execution.

[0050] The control variables of an asymmetric electro-hydraulic actuator system include the servo motor input voltage. Gear pump output flow And the output displacement X of the asymmetric hydraulic cylinder. The equation for the output flow rate of the gear pump is as follows:

[0051]

[0052] In the formula, is the displacement of the gear pump, a constant; n is the actual speed of the gear pump; This refers to the internal leakage coefficient of the gear pump. This refers to the system pressure of the hydraulic transmission module.

[0053] See Figure 1 A segmented modeling and parameter identification method for an asymmetric electro-hydraulic actuator system includes the following steps:

[0054] S1: Based on the electro-hydraulic coupling characteristics of the asymmetric electro-hydraulic actuator system, the asymmetric electro-hydraulic actuator system is modularly decomposed into a motor-controlled pump model and a hydraulic transmission model;

[0055] Modular decomposition is a structural division based on the interaction mechanism of control variables in each physical domain of the servo motor, gear pump, and asymmetric hydraulic cylinder. Specifically, the motor-controlled pump model includes a servo driver, a servo motor, and a gear pump, with the servo motor voltage signal as the input variable and the actual speed of the gear pump as the output variable, directly affecting the flow rate of the hydraulic transmission submodule. The hydraulic transmission submodel includes a gear pump, an asymmetric hydraulic cylinder, a check valve, a hydraulically controlled check valve, and a relief valve, etc., with the actual speed of the gear pump as the input variable and the piston displacement of the asymmetric hydraulic cylinder as the output variable. The output displacement of the asymmetric hydraulic cylinder is driven by the hydraulic flow rate regulated by the motor-controlled pump model, completing the displacement response from electric drive control to hydraulic actuation.

[0056] S2: Based on the characteristics of the two sub-modules, namely the motor-controlled pump model and the hydraulic transmission model, establish mathematical models for each and derive the corresponding transfer functions.

[0057] (1) Transfer function of motor-controlled pump module:

[0058] Voltage balance equation for servo motors:

[0059]

[0060] In the formula, This is the total resistance of the motor armature; This refers to the armature current of the motor. For the armature inductance of the motor; This is the electromagnetic torque coefficient of the motor.

[0061] Torque equation of servo motor:

[0062]

[0063] In the formula, This is the motor torque coefficient; This represents the electromagnetic torque of the motor.

[0064] Servo motor torque balance equation:

[0065]

[0066] In the formula, To convert to the equivalent moment of inertia of the motor shaft; This is the equivalent viscous damping coefficient converted to the motor shaft.

[0067] Combining the above equations and performing a Laplace transform, we obtain the transfer function expression for the motor-controlled pump module, which takes the servo motor voltage as input and the actual speed of the gear pump as output:

[0068]

[0069] In the formula, the natural frequency is Damping ratio is .

[0070] Based on the natural frequency and damping ratio, the transfer function of the motor-controlled pump module can be transformed into a standard second-order transfer function identification form:

[0071]

[0072] In the formula, This is the transfer function for the motor-controlled pump module; The identification coefficient is used.

[0073] (2) Transfer function of hydraulic transmission module:

[0074] The flow equation for a gear pump:

[0075]

[0076] The flow equation for an asymmetric hydraulic cylinder is:

[0077]

[0078] In the formula, This refers to the effective working area of ​​an asymmetric hydraulic cylinder. This refers to the total volume of the asymmetric hydraulic cylinder. The effective bulk modulus of hydraulic fluid; The system pressure of the hydraulic transmission module; This represents the internal leakage coefficient of an asymmetric hydraulic cylinder.

[0079] The dynamic equation of an asymmetric hydraulic cylinder:

[0080]

[0081] In the formula, m is the sum of the piston rod and the load mass converted to the piston mass; is the viscous damping coefficient of the piston and the load.

[0082] Combining the above equations and performing a Laplace transform, we obtain the transfer function expression for the hydraulic transmission module, which takes the actual speed of the gear pump as input and the displacement of the asymmetric hydraulic cylinder as output:

[0083]

[0084] In the formula, , where is the total leakage coefficient of the hydraulic transmission module.

[0085] The transfer function of the motor-controlled pump module can be converted into a standard third-order transfer function identification form:

[0086]

[0087] In the formula, This is the transfer function for the hydraulic transmission module; The identification coefficient is used.

[0088] S3: Apply input excitation and collect output signals to each submodule, establish the model parameter relationship matrix, and perform Bode frequency domain characteristic fitting on the motor pump control module and establish input-output relationship and time domain parameter fitting on the hydraulic transmission model to achieve segmented identification until the preset identification accuracy requirements are met.

[0089] Identification of motor-controlled pump module:

[0090] Input a sinusoidal voltage excitation signal within the operating frequency range to the motor-pump control module:

[0091]

[0092] In the formula, The amplitude of the input voltage signal; The frequency of the input voltage signal

[0093] The actual speed output signal of the end gear pump driven by the voltage signal is collected as follows:

[0094]

[0095] In the formula, This is the actual speed range of the gear pump. It is the phase of the actual rotational speed of the gear pump.

[0096] By acquiring the input and output signals of the motor-controlled pump system, the amplitude and phase information at each frequency point are extracted, and the amplitude gain of the motor-controlled pump module within the specified frequency range is calculated. and phase for:

[0097]

[0098] Based on amplitude and phase data, a Bode diagram of the motor-controlled pump module is plotted, as follows: Figure 4 As shown. The model parameter relationship matrix is ​​constructed as follows:

[0099]

[0100] In the formula, The parameter matrix for the motor-controlled pump module to be identified:

[0101]

[0102] For the input sinusoidal voltage matrix:

[0103]

[0104] To output the actual rotational speed matrix:

[0105]

[0106] Based on the aforementioned least squares method, frequency domain transfer function fitting is performed on the Bode plot. By minimizing the error between the experimental data and the predicted transfer function value, the transfer function is continuously adjusted. Four undetermined parameters are used to make the fitted Bode plot gradually approximate the experimentally measured Bode plot, and the fitting effect is as follows: Figure 5 As shown, this example utilizes Matlab. Once the experiments and fitted graphs meet the preset identification accuracy requirements, the parameter identification of the motor-controlled pump model is complete.

[0107] (2) Identification of hydraulic transmission module:

[0108] The input excitation signal is the steady-state speed signal of the gear pump under the triangular wave excitation of the motor-controlled pump module. Simultaneously, the hydraulic transmission module outputs the piston displacement signal of the asymmetric hydraulic cylinder under the input excitation, such as... Figure 6 As shown. The input and output signals are collected, and the model parameter relationship matrix of the hydraulic transmission module is constructed as follows:

[0109]

[0110] In the formula, B is the parameter matrix of the hydraulic transmission module to be identified:

[0111]

[0112] N is the input actual speed matrix:

[0113]

[0114] X is the output displacement matrix:

[0115]

[0116] Based on the least squares method, the time-domain transfer function of the hydraulic transmission module's input and output is fitted. By minimizing the error between the experimental data and the predicted value of the transfer function, the parameters in the transfer function are continuously adjusted. Four undetermined parameters are used to make the fitted displacement curve gradually approximate the experimentally measured displacement curve, and the fitting effect is as follows: Figure 7 As shown in the figure. This example is implemented using Matlab. When the experiment and the fitted graph meet the preset identification accuracy requirements, the parameter identification of the hydraulic transmission model is completed.

[0117] In step S3 above, the system identification accuracy is assessed. Specifically, the error between the fitted curve and the experimental curve must be controlled within a preset threshold, and the error between the preset experimental data and the fitted data must not exceed 2%. When the identification accuracy requirement is met, the parameter identification process is completed, and the optimal parameter matrix is ​​obtained.

[0118]

[0119]

[0120] Output the optimal transfer functions for the motor-controlled pump model and the hydraulic transmission model:

[0121]

[0122]

[0123] S4: Integrate the sub-module models that have achieved the required identification accuracy to construct a complete identification model for the asymmetric electro-hydraulic actuator system.

[0124] The identification model of the asymmetric electro-hydraulic actuator system is a combination of a motor-controlled pump model and a hydraulic transmission model. Its transfer function can be represented as a series structure of the transfer functions of two sub-modules:

[0125]

[0126] In the formula, It is the transfer function of an asymmetric electro-hydraulic actuator system.

[0127] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for segmented modeling and parameter identification of an asymmetric electro-hydraulic actuator system, characterized in that, The method comprises the following steps: S1: modularly split the asymmetric electro-hydraulic actuator system into a motor-controlled pump model and a hydraulic transmission model; S2: establish mathematical models for the motor-controlled pump model and the hydraulic transmission model, and solve the corresponding transfer functions; S3: apply input excitation to each sub-module and collect output signals, establish a model parameter relationship matrix, and perform Bode frequency domain characteristic fitting on the motor-controlled pump module and input-output relationship establishment and time domain parameter fitting on the hydraulic transmission model to realize segmented identification until the preset identification accuracy requirement is met; S4: integrate the sub-module models with completed identification accuracy to construct a complete asymmetric electro-hydraulic actuator system identification model.

2. The method of claim 1, wherein, The motor pump control model comprises a servo driver, a servo motor and a gear pump, wherein the servo motor voltage signal is taken as an input variable, and the actual rotational speed of the gear pump is taken as an output variable.

3. The method of claim 1, wherein, The hydraulic transmission model comprises a gear pump, an asymmetric hydraulic cylinder, a one-way valve, a hydraulic control one-way valve and an overflow valve, wherein the actual rotational speed of the gear pump is taken as an input variable, and the displacement of the asymmetric hydraulic cylinder piston is taken as an output variable.

4. The method of claim 1, wherein, In step S2, the transfer function of the motor-controlled pump model is: The servo motor voltage is taken as an input, and the actual rotational speed of the gear pump is taken as an output to obtain the transfer function expression of the motor-controlled pump module: , wherein is the transfer function of the motor controlled pump module; is the identified coefficient; N is the actual rotational speed data of the gear pump; Voltage balance equation of the servo motor: wherein, is the total motor armature resistance; is the motor armature current; is the motor armature inductance; is the motor electromagnetic torque coefficient.

5. The method of claim 1, wherein, In step S2, the transfer function of the hydraulic transmission model is: The actual rotational speed of the gear pump is taken as an input, and the displacement of the asymmetric hydraulic cylinder is taken as an output to obtain the transfer function expression of the hydraulic transmission module: , wherein is the transfer function of the hydraulic transmission module; is the identification coefficient; X is the asymmetric hydraulic cylinder displacement data; N is the actual gear pump speed data.

6. The method of claim 1, wherein In step S3, for the motor-controlled pump module, the input excitation is a sinusoidal voltage signal in the working frequency range of the motor-controlled pump module, and the output signal is the actual rotational speed response of the gear pump in the frequency range, and the Bode diagram and the model parameter relationship matrix are constructed as: , In the formula, is the motor pump module parameter matrix to be identified; is the input sinusoidal voltage matrix; N is the output actual speed matrix; Based on the least square method, the frequency domain transfer function fitting is performed on the Bode diagram, four undetermined parameters in the transfer function are adjusted constantly by minimizing the error between the experimental data and the predicted value of the transfer function, so that the fitted Bode diagram gradually approaches the Bode diagram measured in the experiment until the preset identification accuracy requirement is met. four undetermined parameters in the transfer function are adjusted constantly by minimizing the error between the experimental data and the predicted value of the transfer function, so that the fitted Bode diagram gradually approaches the Bode diagram measured in the experiment until the preset identification accuracy requirement is met.

7. The method of claim 1, wherein In step S3, for the hydraulic transmission module, the input excitation is the actual rotational speed signal of the gear pump, and the output signal is the piston displacement signal of the asymmetric hydraulic cylinder, and the model parameter relationship matrix is constructed as: , In the formula, is the hydraulic transmission module parameter matrix to be identified; N is the input actual speed matrix; X is the output displacement matrix; Based on the least square method, the input-output time domain transfer function fitting is constantly adjusted the four undetermined parameters in the transfer function by minimizing the error between the experimental data and the predicted value of the transfer function, so that the fitted displacement curve gradually approaches the experimentally measured displacement curve until the preset identification accuracy requirement is met. four undetermined parameters, so that the fitted displacement curve gradually approaches the experimentally measured displacement curve until the preset identification accuracy requirement is met.

8. The method of claim 1, wherein, In step S3, when the identification accuracy requirement is met, the parameter identification is completed and the optimal parameter matrix of the motor-controlled pump module and the hydraulic transmission module is obtained respectively: , , output the optimal transfer function of each model: , .

9. The method of claim 8, wherein, In step S4, the identification model of the asymmetric electro-hydraulic actuator system is composed of the motor-controlled pump model and the hydraulic transmission model, and its transfer function can be expressed as a series structure of the transfer functions of the two sub-modules, i.e. , wherein is the transfer function of the asymmetric electro-hydraulic actuator system.

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