A force tracking control method for an electro-hydrostatic elastic actuator

Abstract

The present invention discloses a force tracking control method for an electric hydrostatic elastic actuator. The method comprises: establishing a dynamic model of the electric hydrostatic elastic actuator; establishing a robust position controller, inputting the displacement of the piston rod, outputting the control speed of the motor, and controlling the motor to obtain the contact force between the electric hydrostatic elastic actuator and the external environment and the displacement of the load mass block; inputting an environmental parameter estimator, and outputting an estimated value of the environmental elastic coefficient; inputting the estimated values ​​of the contact force and the environmental elastic coefficient into an impedance position signal generator, outputting a position tracking signal of the displacement of the piston rod of the hydraulic cylinder, and performing position tracking on the displacement of the piston rod of the hydraulic cylinder. The method of the present invention performs force tracking control on the electric hydrostatic elastic actuator in an unknown external environment, and the force tracking error can converge to zero in a steady state. Compared with PID control in a dynamic process, it has a faster dynamic response, and can be applied in the field of hydraulic drive with high force control accuracy requirements.

Description

Technical Field

[0001] The invention relates to a force tracking control method, in particular to a force tracking control method for an electric hydrostatic elastic actuator. Background Art

[0002] Tracking control technology has now become one of the essential functions of actuators, so the research field of force control has received widespread attention. In order to achieve good force tracking control performance, the use of elastic actuators has become an effective solution. This solution is widely used in robotic arms, human-machine interactive robots, and teleoperated actuators. Electric hydrostatic elastic actuators, due to the use of hydraulic drive, have the advantages of large torque output and large mass-power ratio compared to existing electric elastic actuators. They have good application potential in the heavy-load field. Therefore, the research work on the force tracking control method of electric hydrostatic elastic actuators is of great significance.

[0003] At present, there have been relevant research works on the prototype of the electric hydrostatic elastic actuator, but there are few studies on precise force control. The main problems faced include two aspects. First: severe nonlinearity and model uncertainty of the hydraulic system; second: unknown external environment. Among the existing force tracking control methods, impedance control is a method that can realize force tracking control in an unknown environment. The impedance model is used to achieve compliance with the unknown external environment, but the force tracking accuracy is difficult to guarantee. In the fields of processing and manufacturing, mold stamping, and polishing, precise force control is related to the quality of the product. Therefore, precise force tracking impedance control in an unknown environment is a key technology that needs to be solved urgently. With the development of control technology, control methods such as adaptive control and robust control have been widely used in practice. The use of adaptive technology to estimate the unknown external environment and the use of robust control to overcome the nonlinearity and model uncertainty of the hydraulic system itself can solve the problem of force tracking impedance control. Summary of the invention

[0004] In order to solve the problems existing in the background technology, the present invention provides a force tracking control method for an electric hydrostatic elastic actuator.

[0005] The technical solution adopted by the present invention is:

[0006] The force tracking control method of the present invention comprises the following steps:

[0007] Step 1: Establish a dynamic model of the electric hydrostatic elastic actuator; use the backstepping control method to establish a robust position controller that meets the feedback constraints based on the dynamic model, input the displacement of the piston rod of the hydraulic cylinder into the robust position controller for processing, and the robust position controller outputs the control speed of the motor, which is input into the electric hydrostatic elastic actuator to control the motor, and obtain the contact force between the electric hydrostatic elastic actuator and the external environment and the displacement of the load mass block.

[0008] Step 2: Establish an environmental parameter estimator for the interaction between the electric hydrostatic elastic actuator and the external environment, input the displacement of the load mass block and the contact force between the electric hydrostatic elastic actuator and the external environment into the environmental parameter estimator for processing, and the environmental parameter estimator outputs an estimated value of the environmental elastic coefficient.

[0009] Step 3: Establish an impedance position signal tracker, input the contact force between the electric hydrostatic elastic actuator and the external environment and the estimated value of the environmental elastic coefficient into the impedance position signal tracker for processing, and the impedance position signal tracker outputs the final position tracking signal of the displacement of the piston rod of the hydraulic cylinder, and tracks the displacement of the piston rod of the hydraulic cylinder, thereby realizing the force tracking control of the electric hydrostatic elastic actuator. The final position tracking signal of the displacement of the piston rod of the hydraulic cylinder is further input into the robust position controller to perform the next round of position tracking on the displacement of the piston rod of the hydraulic cylinder.

[0010] In the step 1, the electric hydrostatic elastic actuator includes a motor, a hydraulic cylinder, a piston rod of the hydraulic cylinder, a hydraulic pump and an elastic actuator. An installation groove is provided inside the elastic actuator, and a spring is installed in the installation groove. The end of the piston rod of the hydraulic cylinder passes through one end of the compression spring of the elastic actuator, and the other end of the spring is against the groove wall of the installation groove. A load mass block is installed on the side of the elastic actuator away from the piston rod of the hydraulic cylinder. The load mass block is connected to an external load by a threaded or flange connection to drive the external load to move and complete the working task. Displacement sensors are installed on the piston rod of the hydraulic cylinder and the load mass block.

[0011] The motor drives the hydraulic pump to pump hydraulic oil into the two chambers of the hydraulic cylinder. The pressure difference between the two chambers of the hydraulic cylinder drives the piston rod of the hydraulic cylinder to move. The elastic actuator is cylindrical and has a mounting groove inside for installing a spring. A mounting hole is provided on the end face of the elastic actuator. The piston output rod is connected to the spring inside the elastic actuator through the mounting hole. The internal spring has a pre-compression force, so that the piston rod is in close contact with the spring.

[0012] In the step 1, the dynamic model of the electro-hydrostatic elastic actuator is established as follows:

[0013]

[0014]

[0015]

[0016] Among them, m cyl is the mass of the piston rod of the hydraulic cylinder; x cyl is the displacement of the piston rod of the hydraulic cylinder, The speed of the piston rod of the hydraulic cylinder collected by the displacement sensor, B is the acceleration of the piston rod of the hydraulic cylinder; cyl is the friction damping of the hydraulic cylinder piston rod; K s is the elastic coefficient of the spring inside the elastic actuator; x load is the displacement of the load mass block collected by the displacement sensor, is the speed of the load mass, F is the acceleration of the load mass; 1 It is the hydraulic driving force generated by the two chambers of the hydraulic cylinder. is the differential of the hydraulic driving force generated by the two chambers of the hydraulic cylinder; m load is the mass of the load mass block; B e is the damping coefficient of the external environment; K e is the elastic coefficient of the electro-hydrostatic elastic actuator interacting with the external environment; α(), β( ) and are the first, second and third nonlinear model parameters of the dynamic model respectively; w p is the controlled speed of the motor of the electro-hydrostatic elastic actuator; d 1 It is the total model uncertainty of the hydraulic system, including the model uncertainty caused by the uncertainty of the dynamic model parameters and the uncertainty that cannot be modeled.

[0017] In the step 1, the established robust position controller satisfying the feedback constraint is specifically as follows:

[0018]

[0019]

[0020] w s1 =-k 3 z 3

[0021] w s2 =-k 3s2 z 3

[0022]

[0023] x 5eq =x 5eqa +x 5eqs1

[0024]

[0025] x 5eqs1 =-k 2 z 2

[0026]

[0027]

[0028]

[0029] Among them, w p is the third backstepping control law, i.e., the control speed of the motor of the electrohydrostatic elastic actuator; wa is the model compensation term of the third backstepping control law, w s1 is the linear error feedback term of the third backstepping control law, w s2 is the nonlinear error feedback term of the third backstepping control law; x5eq is the second backstepping control law, is the differential term of the second backstepping control law; k 3 The linear feedback gain of the third backstepping control rate, z 3 is the deviation between the actual motion acceleration signal of the piston rod of the hydraulic cylinder and the second backstepping control law; k 3s2 The nonlinear feedback gain of the third backstepping control rate; x 5eqa is the model compensation term of the second backstepping control law, x 5eqs1 is the error feedback term of the second backstepping control law; x 4eq is the first backstepping control law; is the differential term of the first backstepping control law; k2 is the linear feedback gain of the second backstepping control law, z 2 is the deviation between the actual motion speed signal of the piston rod of the hydraulic cylinder and the first backstepping control law; c is the final position tracking signal of the displacement of the piston rod of the hydraulic cylinder, k is the differential of the final position tracking signal of the displacement of the piston rod of the hydraulic cylinder; 1 is the linear feedback gain of the first backstepping control rate, z 1 is the actual motion position signal of the piston rod of the hydraulic cylinder and the final position tracking signal x of the displacement of the piston rod of the hydraulic cylinder c The deviation between .

[0030] The third backstepping control law w p As the output of the robust controller, it is transmitted to the motor of the electro-hydrostatic elastic actuator to achieve control. The motor is a servo motor with speed closed-loop control function. The third backstepping control law w p The input is sent to the motor to control the motor, which drives the hydraulic pump to work. The hydraulic pump pumps in and out hydraulic oil to push the piston rod of the hydraulic cylinder to move.

[0031] A position tracking controller, namely a robust position controller, is designed based on the dynamic model of the electric hydrostatic elastic actuator. The robust position controller adopts the backstepping method to overcome the high-order characteristics of the hydraulic system and the robust control method to overcome the parameter uncertainty and uncertain nonlinearity of the system, and finally realizes a position tracking controller with tracking trajectory as input and motor speed control as output.

[0032] The feedback constraints are as follows:

[0033] z 3 (k 3s2 -d 1 )≤ε 3

[0034] k 3s2 ≤0

[0035] Among them, ε 3 is a preset parameter that is small enough.

[0036] In the step 2, the environmental parameter estimator for the interaction between the electro-hydrostatic elastic actuator and the external environment is established as follows:

[0037]

[0038]

[0039]

[0040]

[0041]

[0042] in, is the environmental parameter estimation matrix, Differentiation of the matrix for environmental parameter estimation; is the estimated value of environmental elasticity coefficient, K e is the environmental elasticity coefficient; is the estimated value of the environmental damping coefficient, B e is the environmental damping coefficient; Γ is the positive definite adaptive parameter matrix; φ is the parameter measurement matrix of the electro-hydrostatic elastic actuator; F e The contact force between the electro-hydrostatic elastic actuator and the external environment measured by the force sensor; is the estimated error of the contact force between the electro-hydrostatic elastic actuator and the external environment, is the estimated value of the contact force between the electro-hydrostatic elastic actuator and the external environment; x e is the displacement of the external environment. The force sensor is installed on the electric hydrostatic elastic actuator.

[0043] Parameter estimation of the external environment is a prerequisite for generating the final position tracking signal. The contact force between the actuator and the environment is estimated based on the established model. The estimated force and the force information fed back by the force sensor at the end of the actuator are used to design an adaptive law for environmental parameters. The adaptive law uses the gradient descent method to realize online estimation of environmental parameters.

[0044] In the step 3, establishing an impedance position signal tracker includes an impedance model, a position signal trajectory generator and a position signal tracker, as follows:

[0045] a) Impedance model:

[0046]

[0047] E=F r -F s

[0048] Among them, x p is the first position tracking signal of the displacement of the piston rod of the hydraulic cylinder based on the force tracking error; E is the contact force error between the electric hydrostatic elastic actuator and the external environment; M t is the quality parameter of the impedance model, B t is the damping parameter of the impedance model, K t is the elastic parameter of the impedance model, s is the variable in the frequency domain of the impedance model; F r It is the preset contact force between the electro-hydrostatic elastic actuator and the external environment.

[0049] b) Position signal trajectory generator:

[0050]

[0051]

[0052] Among them, x r A second position tracking signal for the displacement of the piston rod of the hydraulic cylinder based on the environmental information parameter; e is the displacement of the external environment; K es Preset parameters for the position signal trajectory generator; is the estimated value of the environmental elasticity coefficient.

[0053] c) Position signal tracker

[0054] x c =x p +x r

[0055] Among them, x c It is the final position tracking signal of the displacement of the piston rod of the hydraulic cylinder.

[0056] Through stability analysis, it can be found that in steady state, the impedance position signal generator can achieve accurate force tracking effect.

[0057] The beneficial effects of the present invention are:

[0058] The present invention designs a force tracking controller for an electric hydrostatic elastic actuator in an unknown external environment. The force tracking error of the controller can converge to zero in a steady state, and in a dynamic process, it has a faster dynamic response than PID control. Therefore, it has important application value in the field of hydraulic drive with high force control accuracy requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a force tracking control framework diagram of the present invention;

[0060] Figure 2 Tracking curve diagrams of two force tracking controllers of the present invention;

[0061] Figure 3 It is a schematic diagram of the force tracking error of two controllers of the present invention;

[0062] Figure 4 It is a schematic diagram of the environmental parameter estimation performance of the present invention. DETAILED DESCRIPTION

[0063] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0064] like Figure 1 As shown, the force tracking control method of the present invention comprises the following steps:

[0065] Step 1: Establish a dynamic model of the electric hydrostatic elastic actuator; use the backstepping control method to establish a robust position controller that meets the feedback constraints based on the dynamic model, input the displacement of the piston rod of the hydraulic cylinder into the robust position controller for processing, and the robust position controller outputs the control speed of the motor, which is input into the electric hydrostatic elastic actuator to control the motor, and obtain the contact force between the electric hydrostatic elastic actuator and the external environment and the displacement of the load mass block.

[0066] In step one, the electric hydrostatic elastic actuator includes a motor, a hydraulic cylinder, a piston rod of the hydraulic cylinder, a hydraulic pump and an elastic actuator. An installation groove is opened inside the elastic actuator, and a spring is installed in the installation groove. The end of the piston rod of the hydraulic cylinder passes through one end of the compression spring of the elastic actuator, and the other end of the spring is against the groove wall of the installation groove. A load mass block is installed on the side of the elastic actuator away from the piston rod of the hydraulic cylinder. The load mass block is connected to an external load by a threaded or flange connection to drive the external load to move and complete the working task. Displacement sensors are installed on the piston rod of the hydraulic cylinder and the load mass block.

[0067] The motor drives the hydraulic pump to pump hydraulic oil into the two chambers of the hydraulic cylinder. The pressure difference between the two chambers of the hydraulic cylinder drives the piston rod of the hydraulic cylinder to move. The elastic actuator is cylindrical and has a mounting groove inside for installing a spring. A mounting hole is provided on the end face of the elastic actuator. The piston output rod is connected to the spring inside the elastic actuator through the mounting hole. The internal spring has a pre-compression force, so that the piston rod is in close contact with the spring.

[0068] In step 1, the dynamic model of the electro-hydrostatic elastic actuator is established as follows:

[0069]

[0070]

[0071]

[0072] Among them, m cyl is the mass of the piston rod of the hydraulic cylinder; x cyl is the displacement of the piston rod of the hydraulic cylinder, The speed of the piston rod of the hydraulic cylinder collected by the displacement sensor, B is the acceleration of the piston rod of the hydraulic cylinder; cyl is the friction damping of the hydraulic cylinder piston rod; K s is the elastic coefficient of the spring inside the elastic actuator; x load is the displacement of the load mass block collected by the displacement sensor, is the speed of the load mass, F is the acceleration of the load mass; 1 It is the hydraulic driving force generated by the two chambers of the hydraulic cylinder. is the differential of the hydraulic driving force generated by the two chambers of the hydraulic cylinder; m load is the mass of the load mass block; B e is the damping coefficient of the external environment; K e are the elastic coefficients of the electro-hydrostatic elastic actuator interacting with the external environment; α(), β() and are the first, second and third nonlinear model parameters of the dynamic model respectively; w p is the controlled speed of the motor of the electro-hydrostatic elastic actuator; d 1 It is the total model uncertainty of the hydraulic system, including the model uncertainty caused by the uncertainty of the dynamic model parameters and the uncertainty that cannot be modeled.

[0073] In step 1, the robust position controller that satisfies the feedback constraints is established as follows:

[0074]

[0075]

[0076] w s1 =-k 3 z 3

[0077] w s2 =-k 3s2 z 3

[0078]

[0079] x 5eq =x 5eqa +x5 eqs1

[0080]

[0081] x 5eqs1 =-k 2 z 2

[0082]

[0083]

[0084]

[0085] Among them, w p is the third backstepping control law, i.e., the control speed of the motor of the electrohydrostatic elastic actuator; w a is the model compensation term of the third backstepping control law, w s1 is the linear error feedback term of the third backstepping control law, w s2 is the nonlinear error feedback term of the third backstepping control law; x 5eq is the second backstepping control law, is the differential term of the second backstepping control law; k 3 The linear feedback gain of the third backstepping control rate, z 3 is the deviation between the actual motion acceleration signal of the piston rod of the hydraulic cylinder and the second backstepping control law; k 3s2 The nonlinear feedback gain of the third backstepping control rate; x 5eqa is the model compensation term of the second backstepping control law, x 5eqs1 is the error feedback term of the second backstepping control law; x 4eq is the first backstepping control law; is the differential term of the first backstepping control law; k2 is the linear feedback gain of the second backstepping control law, z 2 is the deviation between the actual motion speed signal of the piston rod of the hydraulic cylinder and the first backstepping control law; cis the final position tracking signal of the displacement of the piston rod of the hydraulic cylinder, k is the differential of the final position tracking signal of the displacement of the piston rod of the hydraulic cylinder; 1 is the linear feedback gain of the first backstepping control rate, z 1 is the actual motion position signal of the piston rod of the hydraulic cylinder and the final position tracking signal x of the displacement of the piston rod of the hydraulic cylinder c The deviation between .

[0086] The third backstepping control law w p As the output of the robust controller, it is transmitted to the motor of the electro-hydrostatic elastic actuator to achieve control. The motor is a servo motor with speed closed-loop control function. The third backstepping control law w p The input is sent to the motor to control the motor, which drives the hydraulic pump to work. The hydraulic pump pumps in and out hydraulic oil to push the piston rod of the hydraulic cylinder to move.

[0087] A position tracking controller, namely a robust position controller, is designed based on the dynamic model of the electric hydrostatic elastic actuator. The robust position controller adopts the backstepping method to overcome the high-order characteristics of the hydraulic system and the robust control method to overcome the parameter uncertainty and uncertain nonlinearity of the system, and finally realizes a position tracking controller with tracking trajectory as input and motor speed control as output.

[0088] The feedback constraints are as follows:

[0089] z 3 (k 3s2 -d 1 )≤ε 3

[0090] k 3s2 ≤0

[0091] Among them, ε 3 is a preset parameter that is small enough.

[0092] Step 2: Establish an environmental parameter estimator for the interaction between the electric hydrostatic elastic actuator and the external environment, input the displacement of the load mass block and the contact force between the electric hydrostatic elastic actuator and the external environment into the environmental parameter estimator for processing, and the environmental parameter estimator outputs an estimated value of the environmental elastic coefficient.

[0093] In step 2, the environmental parameter estimator for the interaction between the electro-hydrostatic elastic actuator and the external environment is established as follows:

[0094]

[0095]

[0096]

[0097]

[0098]

[0099] in, is the environmental parameter estimation matrix, Differentiation of the matrix for environmental parameter estimation; is the estimated value of environmental elasticity coefficient, K e is the environmental elasticity coefficient; is the estimated value of the environmental damping coefficient, B e is the environmental damping coefficient; Γ is the positive definite adaptive parameter matrix; φ is the parameter measurement matrix of the electro-hydrostatic elastic actuator; F e The contact force between the electro-hydrostatic elastic actuator and the external environment measured by the force sensor; is the estimated error of the contact force between the electro-hydrostatic elastic actuator and the external environment, is the estimated value of the contact force between the electro-hydrostatic elastic actuator and the external environment; x e is the displacement of the external environment. The force sensor is installed on the electric hydrostatic elastic actuator.

[0100] Parameter estimation of the external environment is a prerequisite for generating the final position tracking signal. The contact force between the actuator and the environment is estimated based on the established model. The estimated force and the force information fed back by the force sensor at the end of the actuator are used to design an adaptive law for environmental parameters. The adaptive law uses the gradient descent method to realize online estimation of environmental parameters.

[0101] Step 3: Establish an impedance position signal tracker, input the contact force between the electric hydrostatic elastic actuator and the external environment and the estimated value of the environmental elastic coefficient into the impedance position signal tracker for processing, and the impedance position signal tracker outputs the final position tracking signal of the displacement of the piston rod of the hydraulic cylinder, and tracks the displacement of the piston rod of the hydraulic cylinder, thereby realizing the force tracking control of the electric hydrostatic elastic actuator. The final position tracking signal of the displacement of the piston rod of the hydraulic cylinder is further input into the robust position controller to perform the next round of position tracking on the displacement of the piston rod of the hydraulic cylinder.

[0102] In step three, an impedance position signal tracker is established, including an impedance model, a position signal trajectory generator, and a position signal tracker, as follows:

[0103] a) Impedance model:

[0104]

[0105] E=F r -F s

[0106] Among them, x pis the first position tracking signal of the displacement of the piston rod of the hydraulic cylinder based on the force tracking error; E is the contact force error between the electric hydrostatic elastic actuator and the external environment; M t is the quality parameter of the impedance model, B t is the damping parameter of the impedance model, K t is the elastic parameter of the impedance model, s is the variable in the frequency domain of the impedance model; F r It is the preset contact force between the electro-hydrostatic elastic actuator and the external environment.

[0107] b) Position signal trajectory generator:

[0108]

[0109]

[0110] Among them, x r A second position tracking signal for the displacement of the piston rod of the hydraulic cylinder based on the environmental information parameter; e is the displacement of the external environment; K es Preset parameters for the position signal trajectory generator; is the estimated value of the environmental elasticity coefficient.

[0111] c) Position signal tracker

[0112] x c =x p +x r

[0113] Among them, x c It is the final position tracking signal of the displacement of the piston rod of the hydraulic cylinder.

[0114] Through stability analysis, it can be found that in steady state, the impedance position signal generator can achieve accurate force tracking effect.

[0115] The present invention performs digital simulation on the above method, analyzes the force tracking effect of the force tracking controller of the present invention, and compares it with the PID force controller to verify the effectiveness of the method of the present invention.

[0116] In terms of simulation parameter settings of the force tracking controller:

[0117] Feedback gain parameter selection of the robust position tracking controller of the present invention:

[0118]

[0119] The PID force tracking control controller is designed as follows

[0120]

[0121] Where u is the control output of the PID force tracking control controller; k p , k i and k d are the gain parameters of the PID force tracking control controller, and are selected as: p =100, k i =10, k d =0.1.

[0122] Positive definite adaptive parameter matrix selection for the environmental parameter estimator:

[0123]

[0124] Impedance model parameter selection:

[0125] M t =10, B t =100, K t =250

[0126] The model parameters of the electro-hydrostatic elastic actuator are shown in Table 1:

[0127] Table 1

[0128]

[0129] like Figure 2 As shown in FIG. , the force tracking effect of the force tracking controller proposed in the present invention is compared with the force tracking effect of the PID force controller. Figure 3 The force tracking error of the force tracking controller proposed by the present invention and the force tracking error of the force tracking controller of the PID controller, wherein C 1 is the force tracking controller proposed in this invention, C 2 It is a PID force controller. Figure 4 The effect of parameter estimation on the environmental parameter estimator.

[0130] It can be seen from the simulation results that the force tracking controller proposed in the present invention has faster dynamic response performance, can track the preset contact force faster, and in steady state, the force tracking error is smaller, and the tracking accuracy is improved by 10 times compared with the PID force tracking control method.

Claims

1. A force tracking control method for an electro-hydrostatic elastic actuator, characterized in that: The method comprises the following steps: Step 1: Establish a dynamic model of the electric hydrostatic elastic actuator; use the backstepping control method to establish a robust position controller that meets the feedback constraint based on the dynamic model, input the displacement of the piston rod of the hydraulic cylinder into the robust position controller for processing, the robust position controller outputs the control speed of the motor, and inputs the control speed of the motor into the electric hydrostatic elastic actuator to control the motor, thereby obtaining the contact force between the electric hydrostatic elastic actuator and the external environment and the displacement of the load mass block; Step 2: Establish an environmental parameter estimator for the interaction between the electric hydrostatic elastic actuator and the external environment, input the displacement of the load mass block and the contact force between the electric hydrostatic elastic actuator and the external environment into the environmental parameter estimator for processing, and the environmental parameter estimator outputs an estimated value of the environmental elastic coefficient; Step 3: Establish an impedance position signal tracker, input the contact force between the electric hydrostatic elastic actuator and the external environment and the estimated value of the environmental elastic coefficient into the impedance position signal tracker for processing, and the impedance position signal tracker outputs the final position tracking signal of the displacement of the piston rod of the hydraulic cylinder, and performs position tracking on the displacement of the piston rod of the hydraulic cylinder, thereby realizing force tracking control of the electric hydrostatic elastic actuator; In the step 1, the electric hydrostatic elastic actuator comprises a motor, a hydraulic cylinder, a piston rod of the hydraulic cylinder, a hydraulic pump and an elastic actuator, a mounting groove is provided inside the elastic actuator, a spring is installed in the mounting groove, the end of the piston rod of the hydraulic cylinder passes through one end of the elastic actuator compression spring, the other end of the spring abuts against the groove wall of the mounting groove, and a load mass block is installed on the side of the elastic actuator away from the piston rod of the hydraulic cylinder; In the step 1, the dynamic model of the electro-hydrostatic elastic actuator is established as follows: Among them, m cyl is the mass of the piston rod of the hydraulic cylinder; x cyl is the displacement of the piston rod of the hydraulic cylinder, is the speed of the piston rod of the hydraulic cylinder, B is the acceleration of the piston rod of the hydraulic cylinder; cyl is the friction damping of the hydraulic cylinder piston rod; K s is the elastic coefficient of the spring inside the elastic actuator; x load is the displacement of the load mass, is the speed of the load mass, is the acceleration of the load mass; F1 is the hydraulic driving force generated by the two chambers of the hydraulic cylinder, is the differential of the hydraulic driving force generated by the two chambers of the hydraulic cylinder; m load is the mass of the load mass block; B e is the damping coefficient of the external environment; K e are the elastic coefficients of the electro-hydrostatic elastic actuator interacting with the external environment; α(), β() and are the first, second and third nonlinear model parameters of the dynamic model respectively; w p is the controlled speed of the motor of the electric hydrostatic elastic actuator; d1 is the total model uncertainty of the hydraulic system; In the step 1, the established robust position controller satisfying the feedback constraint is specifically as follows: <h2 style=";text-align:left;direction:ltr">w<h2 style=";text-align:left;direction:ltr"> s1 <h2 style=";text-align:left;direction:ltr"> =-k3z3 w s2 =-k 3s2 z3 x 5eq =x 5eqa +x 5eqs1 x 5eqs1 =-k2z2 Among them, w p is the third backstepping control law, i.e., the control speed of the motor of the electrohydrostatic elastic actuator; w a is the model compensation term of the third backstepping control law, w s1 is the linear error feedback term of the third backstepping control law, w s2 is the nonlinear error feedback term of the third backstepping control law; x 5eq is the second backstepping control law, is the differential term of the second backstepping control law; k3 is the linear feedback gain of the third backstepping control rate, z3 is the deviation between the actual motion acceleration signal of the piston rod of the hydraulic cylinder and the second backstepping control law; k 3s2 The nonlinear feedback gain of the third backstepping control rate; x 5eqa is the model compensation term of the second backstepping control law, x 5eqs1 is the error feedback term of the second backstepping control law; x 4eq is the first backstepping control law; is the differential term of the first backstepping control law; k2 is the linear feedback gain of the second backstepping control rate; z2 is the deviation between the actual motion speed signal of the piston rod of the hydraulic cylinder and the first backstepping control law; x c is the final position tracking signal of the displacement of the piston rod of the hydraulic cylinder, is the differential of the final position tracking signal of the displacement of the piston rod of the hydraulic cylinder; k1 is the linear feedback gain of the first backstepping control rate, z1 is the actual motion position signal of the piston rod of the hydraulic cylinder and the final position tracking signal x of the displacement of the piston rod of the hydraulic cylinder c The deviation between The feedback constraints are as follows: z3(k 3s2 -d1)≤ε3 k 3s2 ≤0 Among them, ε3 is the preset parameter; In the step 2, the environmental parameter estimator for the interaction between the electro-hydrostatic elastic actuator and the external environment is established as follows: in, is the environmental parameter estimation matrix, Differentiation of the matrix for environmental parameter estimation; is the estimated value of environmental elasticity coefficient, K e is the environmental elasticity coefficient; is the estimated value of the environmental damping coefficient, B e is the environmental damping coefficient; Γ is the positive definite adaptive parameter matrix; φ is the parameter measurement matrix of the electro-hydrostatic elastic actuator; F e is the contact force between the electro-hydrostatic elastic actuator and the external environment; is the estimated error of the contact force between the electro-hydrostatic elastic actuator and the external environment, is the estimated value of the contact force between the electro-hydrostatic elastic actuator and the external environment; x e is the displacement of the external environment; In the step 3, establishing an impedance position signal tracker includes an impedance model, a position signal trajectory generator and a position signal tracker, as follows: a) Impedance model: E=F r -F s Among them, x p is the first position tracking signal of the displacement of the piston rod of the hydraulic cylinder; E is the contact force error between the electric hydrostatic elastic actuator and the external environment; M t is the quality parameter of the impedance model, B t is the damping parameter of the impedance model, K t is the elastic parameter of the impedance model, s is the variable in the frequency domain of the impedance model; F r is the preset contact force between the electro-hydrostatic elastic actuator and the external environment; b) Position signal trajectory generator: Among them, x r A second position tracking signal for the displacement of the piston rod of the hydraulic cylinder; e is the displacement of the external environment; K es Preset parameters for the position signal trajectory generator; is the estimated value of environmental elasticity coefficient; c) Position signal tracker x c =x p +x r Among them, x c It is the final position tracking signal of the displacement of the piston rod of the hydraulic cylinder.

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