EHA drive control system three-closed-loop control system and dynamic hysteresis compensation method

Abstract

The invention discloses an EHA drive control system three-closed-loop control system and a dynamic hysteresis compensation method. The technical problems that an existing electro-hydrostatic actuator is large in hydraulic hysteresis error, poor in dynamic response and insufficient in environmental adaptability are solved. The method comprises a three-stage control structure of a position control loop, a speed control loop and a current control loop, the position control loop introduces load disturbance feed-forward compensation based on a state observer, the speed control loop adopts an adaptive sliding mode control strategy, the current control loop executes a decoupling vector control algorithm, and the load disturbance feed-forward compensation is realized. And a dynamic hysteresis compensation model based on historical input and disturbance estimation is established in the controller. According to the system, the servo motor, the gear pump, the hydraulic cylinder and the sensor module are integrated into an integrated drive control structure, and the effects of improving the control precision, reducing the response time delay and correcting the hydraulic hysteresis error are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of EHA drive control systems, and in particular to a three-closed-loop control system and a dynamic hysteresis compensation method for an EHA drive control system. Background Art

[0002] An electro-hydrostatic actuator (EHA) is a servo system that directly controls the movement of an actuator via an electric motor-driven hydraulic pump. It is widely used in aerospace, industrial robotics, and high-performance equipment. In this system, the electric motor, hydraulic pump, valves, and actuators form a closed drive loop, and an electronic controller controls position, speed, or force. Compared to traditional centralized hydraulic systems, EHA systems offer decentralization, fast response, and a high degree of integration, making them particularly suitable for scenarios requiring high reliability and dynamic response.

[0003] Existing EHA control systems mostly use an electro-hydraulic conversion structure based on a permanent magnet synchronous motor, combining typical control strategies such as position control, speed control, and current control to form a feedback loop. At the same time, to improve control accuracy, some solutions introduce feedforward compensation or nonlinear modeling methods, such as the Preisach model hysteresis compensation method. However, in actual engineering applications, there are still several key issues: First, the hydraulic cylinder system has obvious dynamic hysteresis, which is affected by factors such as valve core friction and oil compressibility, and easily leads to tracking error accumulation; second, the control system's stability decreases when there are sudden load changes or parameter disturbances; third, EHA control components generally adopt a discrete configuration, the system is large in size, and the structural connections are complex, making it difficult to adapt to miniaturization and high-integration application scenarios.

[0004] Therefore, how to provide a three-closed-loop control system and a dynamic hysteresis compensation method for an EHA drive control system is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] One purpose of the present invention is to propose a three-closed-loop control system and a dynamic hysteresis compensation method for an EHA drive control system, aiming to solve the problems of large hydraulic hysteresis error, unstable dynamic response and low system structure integration existing in the existing electric hydrostatic actuator control system.

[0006] According to an embodiment of the present invention, a dynamic hysteresis compensation method for three closed-loop control of an EHA drive control system includes the following steps:

[0007] S1. The host computer outputs a target position command, and obtains the current position of the hydraulic cylinder piston rod through a linear displacement sensor installed at the end of the hydraulic cylinder piston rod. The displacement error between the target position command and the current position is calculated as the input signal of the position control loop in the electrohydrostatic actuator control system;

[0008] S2. A controller of the electro-hydrostatic actuator control system processes the displacement error based on a proportional-integral-differential control law and generates a speed reference signal in combination with a load disturbance feedforward compensation model, wherein the load disturbance feedforward compensation model uses a state observer to estimate the external disturbance load torque and superimposes it on the control signal;

[0009] S3, inputting the speed reference signal into a speed control loop, constructing a sliding mode surface function using an adaptive sliding mode control method, and generating a current command based on the speed error, wherein the speed control loop includes a disturbance estimator and a boundary layer switching function module;

[0010] S4. Input the current command into the current control loop, calculate the d-axis voltage command and the q-axis voltage command respectively through a decoupling vector control method based on the dq-axis electrical model of the permanent magnet synchronous servo motor, and compensate for the motor back electromotive force and electrical coupling term;

[0011] S5. Convert the d-axis voltage command and the q-axis voltage command into a three-phase PWM control signal via a power drive module to drive the permanent magnet synchronous servo motor to rotate, thereby driving the gear pump to output hydraulic oil and push the piston rod of the hydraulic cylinder;

[0012] S6. Based on the historical control signals and the estimated load disturbance data within the current control cycle, a dynamic hysteresis compensation module is established to correct the nonlinear hysteresis error caused by the compressibility of the oil inside the hydraulic cylinder and the friction of the valve core. The dynamic hysteresis compensation module is periodically updated within the controller and superimposed on the control channel;

[0013] S7. During the operation of the electric hydrostatic actuator drive control system, the servo motor current signal, DC bus voltage signal, servo motor speed signal and hydraulic cylinder piston rod displacement signal are collected in real time. If any of the signals exceeds the preset safety threshold, the controller's internal fault processing module is triggered to shut down the power output path and send a fault code to the host computer through the communication interface.

[0014] Optionally, the S1 specifically includes:

[0015] S11. The host computer sends a target position instruction to the electro-hydrostatic actuator controller through a communication interface, wherein the target position instruction is a value in millimeters;

[0016] S12, a linear displacement sensor is provided at the end of the hydraulic cylinder piston rod to measure the current position of the hydraulic cylinder piston rod and output a displacement signal in millimeters;

[0017] S13, the electro-hydrostatic actuator controller calculates a displacement error signal according to the target position command and the current position;

[0018] S14. The electro-hydrostatic actuator controller updates the target position command, current position and displacement error signal at a fixed sampling period, and inputs the displacement error signal into the position control loop.

[0019] Optionally, the S2 specifically includes:

[0020] S21, the electro-hydrostatic actuator controller inputs the displacement error signal into the position control loop, executes the proportional-integral-differential control law consisting of the superposition of the proportional term, the integral term, and the differential term, and obtains a preliminary speed reference signal;

[0021] S22, the electro-hydrostatic actuator controller estimates the disturbed load torque τ of the hydraulic cylinder based on the state observation model f , the state observation model is:

[0022]

[0023] Among them, τ f Denotes the disturbance load torque, K t Represents the motor torque constant, J eq Denotes the equivalent moment of inertia of the system, B eq represents the equivalent damping coefficient, ω m Indicates the servo motor speed, Indicates the acceleration of the servo motor;

[0024] S23, the electro-hydrostatic actuator controller converts the disturbance load torque τ f It is superimposed with the preliminary speed reference signal output by the proportional-integral-differential control law to form a corrected speed reference signal;

[0025] S24. The electro-hydrostatic actuator controller inputs the corrected speed reference signal into the speed control loop in the electro-hydrostatic actuator control system, and uses the corrected speed reference signal as an input signal of the sliding mode control algorithm in the speed control loop to participate in the next current command generation calculation.

[0026] Optionally, the S3 specifically includes:

[0027] S31, the electro-hydrostatic actuator controller compares the speed reference signal with the current speed of the servo motor to obtain a speed error signal e v ;

[0028] S32. The electric hydrostatic actuator controller constructs a sliding surface function s based on the velocity error signal. The sliding surface function expression is:

[0029]

[0030] Among them, s is the sliding surface function, e v is the speed error, is the first-order derivative of the velocity error, β is the sliding surface convergence rate coefficient;

[0031] S33, the electric hydrostatic actuator controller sets the switching function and constructs the control law, which includes the proportional-integral term, the sliding mode term and the disturbance estimation term. The sliding mode control current command u sm( The calculation formula is:

[0032]

[0033] Among them, K vo Proportional gain, K vi is the integral gain, λ is the sliding mode gain, is the boundary layer thickness, sat(·) is the saturation function, is the disturbance term estimated online;

[0034] S34. The electric hydrostatic actuator controller inputs the sliding mode control current command output by the control law into the current control loop.

[0035] Optionally, the S4 specifically includes:

[0036] S41, the electric hydrostatic actuator controller decomposes the current command output by the speed control loop into the d-axis current command i d and q-axis current command i q , and calculate the target driving voltage command v d With v q ;

[0037] S42. The electric hydrostatic actuator controller calculates the drive voltages of the d-axis and q-axis based on the electrical model of the permanent magnet synchronous servo motor. The control formula is:

[0038]

[0039] Among them, v d ,v q is the d-axis and q-axis driving voltage command, i d ,i q is the actual current of d-axis and q-axis, R s is the stator resistance, L d ,L q is the d-axis and q-axis inductance, ω e is the motor electrical angular velocity, ψ f is the permanent magnet flux;

[0040] S43, Electrohydrostatic Actuator Controller Calculation Cross-coupling Term -ω e ·L q ·i q With +ω e ·(L d ·id +ψ f ), and perform decoupling compensation operations between voltage channels;

[0041] S44, the electro-hydrostatic actuator controller sets the target drive voltage instruction v d With v q Input to the power drive module and output three-phase PWM control signal to the permanent magnet synchronous servo motor.

[0042] Optionally, the S6 specifically includes:

[0043] S61, the electric hydrostatic actuator controller records the control input signal u(t-Δt) and the current position of the hydraulic cylinder piston rod θ(t-Δt) in the previous cycle during the control cycle, and combines the load disturbance estimation value τ collected in the current cycle f (t), forming the dynamic hysteresis compensation input vector;

[0044] S62: The electro-hydrostatic actuator controller constructs a dynamic hysteresis compensation model based on the input vector and uses the following form to perform error estimation:

[0045] Δθ hyst (t)=α1·u(t-Δt)+α2·τ f (t)+α3·θ(t-Δt);

[0046] Where Δθ hyst (t) is the estimated value of the hysteresis error, u(t-Δt) is the control input signal, τ f (t) is the disturbance load torque, θ(t-Δt) is the piston rod displacement in the previous cycle, and α1, α2, and α3 are the hysteresis modeling coefficients;

[0047] S63, the electro-hydrostatic actuator controller calculates the hysteresis error estimate Δθ hyst (t) is subtracted from the position control path to form the corrected position feedback signal:

[0048] θ (orr (t) = θ(t) - Δθ hyst (t);

[0049] Among them, θ corr (t) represents the corrected position input signal;

[0050] S64, the electro-hydrostatic actuator controller inputs the corrected position signal θ corr (t) Replace the original feedback position signal input to the position control loop to complete the online dynamic compensation of the hydraulic hysteresis effect.

[0051] Optionally, the S7 specifically includes:

[0052] S71, the electric hydrostatic actuator controller collects the servo motor current signal, the DC bus voltage signal, the servo motor speed signal, and the hydraulic cylinder piston rod displacement signal in each control cycle;

[0053] S72: The electro-hydrostatic actuator controller compares the four types of signals with their preset safety thresholds respectively. If any signal exceeds the corresponding threshold, it is determined to be an abnormal state.

[0054] S73: The electric hydrostatic actuator controller responds to the abnormal state and immediately shuts down the PWM output signal of the power drive module, thereby blocking the drive channel to the servo motor.

[0055] S74: The electric hydrostatic actuator controller sends a fault code to the host computer through the CAN FD communication interface, and simultaneously drives the fault status indicator light to light up and the operation status indicator light to turn off, completing the fault prompt action.

[0056] Optional, EHA drive control system three closed-loop control system, including the following modules:

[0057] Electric hydrostatic actuator controller module: used to implement a three-loop control strategy based on position control loop, speed control loop, and current control loop;

[0058] Host computer module: connected to the electric hydrostatic actuator controller and sends a target position command signal;

[0059] Linear displacement sensor module: installed at the end of the hydraulic cylinder piston rod, collects the current position of the hydraulic cylinder piston rod and outputs the current position signal to the electric hydrostatic actuator controller;

[0060] Servo motor encoder module: installed at the end of the permanent magnet synchronous servo motor shaft, collects the motor's speed and position signals and outputs them to the electro-hydrostatic actuator controller;

[0061] Three-phase permanent magnet synchronous servo motor module: receives the PWM control signal output by the electro-hydrostatic actuator controller and drives the connected gear pump to rotate;

[0062] Gear pump module: driven by the servo motor to rotate and output hydraulic oil;

[0063] Hydraulic system component module: includes a hydraulically controlled one-way valve, a relief valve and a hydraulic cylinder. Hydraulic oil is input into the hydraulic cylinder after being controlled by the hydraulic system component, causing the piston rod to produce linear displacement;

[0064] Power drive module: Equipped with a SiC MOSFET three-phase full-bridge structure, it receives the d-axis and q-axis voltage command signals output by the electro-hydrostatic actuator controller, generates a three-phase PWM control signal, and outputs it to the servo motor;

[0065] Current detection module: configured at the input end of the electric hydrostatic actuator controller to collect the servo motor bus current signal;

[0066] DC bus voltage detection module: collects the DC bus voltage value of the system and feeds it back to the electric hydrostatic actuator controller;

[0067] The beneficial effects of the present invention are:

[0068] (1) By constructing a three-loop control structure consisting of a position control loop, a speed control loop, and a current control loop, and combining a state observer with a sliding mode control algorithm, the controller maintains strong control stability and response consistency under conditions such as load disturbances, friction changes, and parameter offsets;

[0069] (2) A dynamic hysteresis compensation model based on historical control input, external disturbance estimation, and the position state of the previous cycle is used to estimate and correct the hysteresis error caused by oil compressibility and valve core friction in the hydraulic system in real time, thereby improving the positioning accuracy of the hydraulic cylinder piston rod;

[0070] (3) The system structure adopts an integrated integration of servo motor, hydraulic pump, controller and sensor module to simplify wiring connection and reduce system volume, which is conducive to the construction of a miniaturized and highly integrated drive control platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0072] Figure 1 This is a block diagram of the three-closed-loop control system of the EHA drive control system proposed in the present invention;

[0073] Figure 2 This is the internal three-closed-loop control structure diagram of the three-closed-loop control system and dynamic hysteresis compensation method of the EHA drive control system proposed in the present invention;

[0074] Figure 3 It is a logic block diagram of the dynamic hysteresis compensation path of the three-closed-loop control system and dynamic hysteresis compensation method of the EHA drive control system proposed in the present invention. DETAILED DESCRIPTION

[0075] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner.

[0076] refer to Figure 1-3The three-closed-loop control system and dynamic hysteresis compensation method of the EHA drive control system include the following steps:

[0077] S1. The host computer outputs a target position command, and obtains the current position of the hydraulic cylinder piston rod through a linear displacement sensor installed at the end of the hydraulic cylinder piston rod. The displacement error between the target position command and the current position is calculated as the input signal of the position control loop in the electrohydrostatic actuator control system;

[0078] S2. A controller of the electro-hydrostatic actuator control system processes the displacement error based on a proportional-integral-differential control law and generates a speed reference signal in combination with a load disturbance feedforward compensation model, wherein the load disturbance feedforward compensation model uses a state observer to estimate the external disturbance load torque and superimposes it on the control signal;

[0079] S3, inputting the speed reference signal into a speed control loop, constructing a sliding mode surface function using an adaptive sliding mode control method, and generating a current command based on the speed error, wherein the speed control loop includes a disturbance estimator and a boundary layer switching function module;

[0080] S4. Input the current command into the current control loop, calculate the d-axis voltage command and the q-axis voltage command respectively through a decoupling vector control method based on the dq-axis electrical model of the permanent magnet synchronous servo motor, and compensate for the motor back electromotive force and electrical coupling term;

[0081] S5. Convert the d-axis voltage command and the q-axis voltage command into a three-phase PWM control signal via a power drive module to drive the permanent magnet synchronous servo motor to rotate, thereby driving the gear pump to output hydraulic oil and push the piston rod of the hydraulic cylinder;

[0082] S6. Based on the historical control signals and the estimated load disturbance data within the current control cycle, a dynamic hysteresis compensation module is established to correct the nonlinear hysteresis error caused by the compressibility of the oil inside the hydraulic cylinder and the friction of the valve core. The dynamic hysteresis compensation module is periodically updated within the controller and superimposed on the control channel;

[0083] S7. During the operation of the electric hydrostatic actuator drive control system, the servo motor current signal, DC bus voltage signal, servo motor speed signal and hydraulic cylinder piston rod displacement signal are collected in real time. If any of the signals exceeds the preset safety threshold, the controller's internal fault processing module is triggered to shut down the power output path and send a fault code to the host computer through the communication interface.

[0084] In this embodiment, S1 specifically includes:

[0085] S11. The host computer sends a target position instruction to the electro-hydrostatic actuator controller through a communication interface, wherein the target position instruction is a value in millimeters;

[0086] S12, a linear displacement sensor is provided at the end of the hydraulic cylinder piston rod to measure the current position of the hydraulic cylinder piston rod and output a displacement signal in millimeters;

[0087] S13, the electro-hydrostatic actuator controller calculates a displacement error signal according to the target position command and the current position;

[0088] S14. The electro-hydrostatic actuator controller updates the target position command, current position and displacement error signal at a fixed sampling period, and inputs the displacement error signal into the position control loop.

[0089] This implementation achieves real-time acquisition of position deviation by constructing an error calculation path between the target position command and the actual displacement of the hydraulic cylinder piston rod, and establishes a complete position control loop input signal path, providing a stable data basis for subsequent control closed loops and compensation modules.

[0090] In this embodiment, S2 specifically includes:

[0091] S21, the electro-hydrostatic actuator controller inputs the displacement error signal into the position control loop, executes the proportional-integral-differential control law consisting of the superposition of the proportional term, the integral term, and the differential term, and obtains a preliminary speed reference signal;

[0092] S22, the electro-hydrostatic actuator controller estimates the disturbed load torque τ of the hydraulic cylinder based on the state observation model f , the state observation model is:

[0093]

[0094] Among them, τ f Denotes the disturbance load torque, K t Represents the motor torque constant, J eq Denotes the equivalent moment of inertia of the system, B eq represents the equivalent damping coefficient, ω m Indicates the servo motor speed, Indicates the acceleration of the servo motor;

[0095] S23, the electro-hydrostatic actuator controller converts the disturbance load torque τ f It is superimposed with the preliminary speed reference signal output by the proportional-integral-differential control law to form a corrected speed reference signal;

[0096] S24. The electro-hydrostatic actuator controller inputs the corrected speed reference signal into the speed control loop in the electro-hydrostatic actuator control system, and uses the corrected speed reference signal as an input signal of the sliding mode control algorithm in the speed control loop to participate in the next current command generation calculation.

[0097] This embodiment introduces a load disturbance feedforward compensation module based on a state observer into the position control loop, so that the speed reference signal includes load dynamic prediction information while containing position deviation information, constructs a speed command generation path with parallel feedback and prediction, and enhances the system's continuous control capability under external disturbance conditions.

[0098] In this embodiment, S3 specifically includes:

[0099] S31, the electro-hydrostatic actuator controller compares the speed reference signal with the current speed of the servo motor to obtain a speed error signal e v ;

[0100] S32. The electric hydrostatic actuator controller constructs a sliding surface function s based on the velocity error signal. The sliding surface function expression is:

[0101]

[0102] Among them, s is the sliding surface function, e v is the speed error, is the first-order derivative of the velocity error, β is the sliding surface convergence rate coefficient;

[0103] S33, the electric hydrostatic actuator controller sets the switching function and constructs the control law, which includes the proportional-integral term, the sliding mode term and the disturbance estimation term. The sliding mode control current command u smc The calculation formula is:

[0104]

[0105] Among them, K vp Proportional gain, K vi is the integral gain, λ is the sliding mode gain, is the boundary layer thickness, sat(·) is the saturation function, is the disturbance term estimated online;

[0106] S34. The electric hydrostatic actuator controller inputs the sliding mode control current command output by the control law into the current control loop.

[0107] This embodiment embeds an adaptive sliding mode control method in the speed control loop, constructs a sliding mode surface function and a disturbance estimation channel, achieves convergence adjustment of the dynamic characteristics of the speed error and real-time estimation of uncertain external disturbances, provides a robust current command input for the current control loop, and improves the system's adaptability to sudden loads or friction fluctuations.

[0108] In this embodiment, S4 specifically includes:

[0109] S41, the electric hydrostatic actuator controller decomposes the current command output by the speed control loop into the d-axis current command i d and q-axis current command i q , and calculate the target driving voltage command v d With v q ;

[0110] S42. The electric hydrostatic actuator controller calculates the drive voltages of the d-axis and q-axis based on the electrical model of the permanent magnet synchronous servo motor. The control formula is:

[0111]

[0112] Among them, v d ,v q is the d-axis and q-axis driving voltage command, i d ,i q is the actual current of d-axis and q-axis, R s is the stator resistance, L d ,L q is the d-axis and q-axis inductance, ω e is the motor electrical angular velocity, ψ f is the permanent magnet flux;

[0113] S43, Electrohydrostatic Actuator Controller Calculation Cross-coupling Term -ω e ·L q ·i q With +ω e ·(L d ·i d +ψ f ), and perform decoupling compensation operations between voltage channels;

[0114] S44, the electro-hydrostatic actuator controller sets the target drive voltage instruction v d With v q Input to the power drive module and output three-phase PWM control signal to the permanent magnet synchronous servo motor.

[0115] This embodiment uses a vector decoupling control method based on the motor electrical model to compensate for the voltage cross-interference between the d-axis and q-axis and the influence of the permanent magnet back electromotive force, making the motor drive current channel response more independent, helping to maintain the high dynamic characteristics of the motor and providing continuous and stable flow drive capabilities for the subsequent hydraulic actuators.

[0116] In this embodiment, S6 specifically includes:

[0117] S61, the electric hydrostatic actuator controller records the control input signal u(t-Δt) and the current position of the hydraulic cylinder piston rod θ(t-Δt) in the previous cycle during the control cycle, and combines the load disturbance estimation value τ collected in the current cyclef (t), forming the dynamic hysteresis compensation input vector;

[0118] S62: The electro-hydrostatic actuator controller constructs a dynamic hysteresis compensation model based on the input vector and uses the following form to perform error estimation:

[0119] Δθ hyst (t)=α1·u(t-Δt)+α2·τ f (t)+α3·θ(t-Δt);

[0120] Where Δθ hyst (t) is the estimated value of the hysteresis error, u(t-Δt) is the control input signal, τ f (t) is the disturbance load torque, θ(t-Δt) is the piston rod displacement in the previous cycle, and α1, α2, and α3 are the hysteresis modeling coefficients;

[0121] S63, the electro-hydrostatic actuator controller calculates the hysteresis error estimate Δθ hyst (t) is subtracted from the position control path to form the corrected position feedback signal:

[0122] θ corr (t) = θ(t) - Δθ hyst (t);

[0123] Among them, θ corr (t) represents the corrected position input signal;

[0124] S64, the electro-hydrostatic actuator controller inputs the corrected position signal θ corr (t) Replace the original feedback position signal input to the position control loop to complete the online dynamic compensation of the hydraulic hysteresis effect.

[0125] This implementation establishes a dynamic hysteresis compensation model within the controller based on control input, disturbance estimation, and historical displacement to correct the position lag error caused by the nonlinearity of the hydraulic system in real time, making the position feedback path closer to the actual physical response and improving the tracking consistency and control accuracy of the system under high-frequency dynamic conditions.

[0126] In this embodiment, S7 specifically includes:

[0127] S71, the electric hydrostatic actuator controller collects the servo motor current signal, the DC bus voltage signal, the servo motor speed signal, and the hydraulic cylinder piston rod displacement signal in each control cycle;

[0128] S72: The electro-hydrostatic actuator controller compares the four types of signals with their preset safety thresholds respectively. If any signal exceeds the corresponding threshold, it is determined to be an abnormal state.

[0129] S73: The electric hydrostatic actuator controller responds to the abnormal state and immediately shuts down the PWM output signal of the power drive module, thereby blocking the drive channel to the servo motor.

[0130] S74: The electric hydrostatic actuator controller sends a fault code to the host computer through the CAN FD communication interface, and simultaneously drives the fault status indicator light to light up and the operation status indicator light to turn off, completing the fault prompt action.

[0131] This embodiment implements real-time monitoring and fault handling of the operating status of the electric hydrostatic actuator drive control system by periodically detecting and limiting the current, voltage, speed, and displacement signals, combined with communication feedback and fault indication mechanisms, ensuring that the system promptly terminates control output under abnormal circumstances to prevent equipment damage and uncontrolled operation.

[0132] In this embodiment, the three-closed-loop control system of the EHA drive control system includes the following modules:

[0133] Electric hydrostatic actuator controller module: used to implement a three-loop control strategy based on position control loop, speed control loop, and current control loop;

[0134] Host computer module: connected to the electric hydrostatic actuator controller and sends a target position command signal;

[0135] Linear displacement sensor module: installed at the end of the hydraulic cylinder piston rod, collects the current position of the hydraulic cylinder piston rod and outputs the current position signal to the electric hydrostatic actuator controller;

[0136] Servo motor encoder module: installed at the end of the permanent magnet synchronous servo motor shaft, collects the motor's speed and position signals and outputs them to the electro-hydrostatic actuator controller;

[0137] Three-phase permanent magnet synchronous servo motor module: receives the PWM control signal output by the electro-hydrostatic actuator controller and drives the connected gear pump to rotate;

[0138] Gear pump module: driven by the servo motor to rotate and output hydraulic oil;

[0139] Hydraulic system component module: includes a hydraulically controlled one-way valve, a relief valve and a hydraulic cylinder. Hydraulic oil is input into the hydraulic cylinder after being controlled by the hydraulic system component, causing the piston rod to produce linear displacement;

[0140] Power drive module: Equipped with a SiC MOSFET three-phase full-bridge structure, it receives the d-axis and q-axis voltage command signals output by the electro-hydrostatic actuator controller, generates a three-phase PWM control signal, and outputs it to the servo motor;

[0141] Current detection module: configured at the input end of the electric hydrostatic actuator controller to collect the servo motor bus current signal;

[0142] DC bus voltage detection module: collects the DC bus voltage value of the system and feeds it back to the electric hydrostatic actuator controller;

[0143] This embodiment realizes the mapping of d-axis and q-axis voltage commands to three-phase PWM power waveforms by establishing an SVPWM modulation mechanism and a digital isolation drive path, ensuring the full-link controllability of the drive signal from coordinate transformation, sector determination to switching time generation. Through digital isolation logic and dead time control, bridge arm direct pass is avoided, and the operational safety of the drive circuit is improved. The power drive module achieves high-speed switching capability through SiC devices, reducing switching losses while achieving current modulation accuracy, and combines the bus voltage dynamic limiting processing to maintain the linear control range of the motor voltage output stable, thereby completing the complete power closed-loop path from control command output to motor electromagnetic energy injection, forming a dynamic response mechanism under multi-link linkage.

[0144] Example 1:

[0145] To verify the feasibility of this invention, it was applied to the commissioning of a tracked, highly maneuverable engineering robot platform. Traditional electro-hydrostatic actuation systems suffer from response lag, poor control accuracy, and insufficient noise immunity. Especially under non-stationary load variations or with significant hydraulic hysteresis, the system is prone to error amplification and position drift, severely impacting the safety and control experience of the platform. The platform requires high-frequency reciprocating motion at a frequency of 1 Hz within a ±25 mm actuation range, with a control error limit of ±0.1 mm. In traditional position-velocity dual-loop control, the lack of current level regulation and inherent hysteresis in the hydraulic system result in slow closed-loop response, poor system stability, and nonlinear anomalies such as crawling and rebound during actuation. To address these issues, this embodiment utilizes a three-loop closed-loop control system and dynamic hysteresis compensation method for the EHA drive control system. The system integrates the controller, motor drive, power bridge, current sampling, and sensor interface into a highly integrated system, offering high integration, sensitive control, remote upgradeability, and strong adaptability to extreme operating conditions. The software structure adopts dual program division of Boot Loader and APP, and remote maintenance is realized through the upgradeable architecture; the control algorithm adopts a three-closed-loop nested structure of position-speed-current, combined with hysteresis modeling and real-time compensation mechanism, which significantly improves the control accuracy and dynamic stability of the actuator system.

[0146] After the platform is powered on, the controller first starts the Boot Loader program and monitors for a remote upgrade command within 2 seconds. If an upgrade flag is received, the system reads the current software version, receives the new firmware package from the host computer, performs a data integrity check, and writes it to the Flash memory. After the write is complete, the Flash memory data is read back for verification. After confirming the write is correct, the controller jumps to the App program. If no upgrade request is received, the system automatically enters the App segment control program and loads the control algorithm logic.

[0147] The app first completes system initialization, including configuration of the ADC, PWM, DIDO, and CAN communication modules, clock calibration, hardware interrupt enablement, and loading control parameters from the EEPROM. After initialization, the system enters the soft-start control process, initially closing soft-start relay K1 while keeping input relay K2 open. The bus voltage begins to slowly rise, with the system sampling the voltage every 0.2 seconds via the ADC. When the voltage exceeds 80% of the bus reference value, the system closes K2 and opens K1, returning to normal power supply. The entire soft-start process lasts 3.4 seconds, with the current ramp rate controlled within 1.3A / s and the maximum inrush current not exceeding 4.6A.

[0148] The system then enters a three-loop closed-loop control phase. The outer loop is the position loop, which receives displacement feedback from the position sensor, compares it with the command, and outputs a drive signal. The middle loop is the velocity loop, which receives the command from the previous stage and adjusts the error between the target and actual speeds, providing strong noise immunity. The inner loop is the current loop, which samples the current in real time and adjusts the voltage output to achieve rapid control of the servo motor. The motor controls the three-phase power bridge output via an SVPWM modulator, driving the gear pump and ultimately controlling the hydraulic cylinder. This control structure enables fine-grained adjustment of position, velocity, and current, ensuring stable operation under complex loads and rapid response requirements.

[0149] The system interrupt service program is executed every 0.5ms, including sampling and over-limit judgment of current, voltage, speed, and position. If the sampling value exceeds the system-set threshold (such as current > 48A, voltage > 65V, temperature > 70℃, displacement deviation > ±3mm), the system will immediately turn off the running indicator light, light up the fault light, send a fault frame to the host computer and disable the PWM output to ensure that the system is in a protected state. If the parameters are normal, the PWM duty cycle is updated according to the latest output instruction and the closed-loop operation is continued. The main loop program executes non-real-time tasks such as communication processing, LED control, parameter reporting, key input recognition, etc. in a 10ms period to ensure communication stability and human-computer interaction responsiveness.

[0150] This system uses a hysteresis estimation and correction algorithm based on the Preisach model. By storing the control direction, response deviation, and output error from the previous cycle, dynamically matching the hysteresis curve segment and introducing a feedforward correction into the next cycle's control instructions, it achieves early offset of hysteresis. During dynamic response, the system maintains excellent tracking performance even in sudden load changes, direction reversals, or within a narrow valve opening range, avoiding the jumps, overshoots, and steady-state swings common in traditional systems.

[0151] The platform vehicle runs a 1Hz square wave displacement command within a ±20mm actuation range. After running for 10,000 cycles, the system operating status and test results are as follows:

[0152] Table 1 EHA system performance comparison data

[0153]

[0154] In multiple actual control scenarios, the system exhibits good stability and robustness, especially in stages of frequent reverse motion, switching between different loads, or drastic changes in hydraulic hysteresis. The control error converges significantly, and common problems of traditional systems such as creeping, jumping, and control oscillation do not occur.

[0155] In the test under extreme low-temperature conditions (–30°C), the system ran continuously for 12 hours under high-frequency actuation. The surface temperature of the controller housing did not exceed 45°C, the thermal junction temperature of the internal power devices was within a safe range, and no fault protection mechanisms such as overvoltage, overcurrent, and overtemperature were triggered. The system status remained stable.

[0156] The system's remote upgrade capability was also verified during testing. Even after a network disconnection and reconnection, the Boot Loader mechanism completed a complete software update in 13.5 seconds, achieving 100% data integrity and automatically jumping to the new version of the app to continue running. This demonstrates the software architecture's strong fault tolerance and engineering practicality.

[0157] The above data and actual operating performance show that the three-closed-loop control structure and dynamic hysteresis compensation mechanism in the integrated EHA drive and control system can systematically solve the problems of slow response, large error, strong hysteresis, and high energy consumption of traditional hydraulic actuators. It has extremely high technical adaptability, stability and control accuracy under extreme combat conditions, meets the multiple key indicator requirements of the actuation system put forward by high-performance unmanned platforms, and has broad engineering promotion value.

[0158] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. The dynamic hysteresis compensation method of the three-closed-loop control of the EHA drive control system is characterized by: The following steps are involved: S1. The host computer outputs a target position command, and obtains the current position of the hydraulic cylinder piston rod through a linear displacement sensor installed at the end of the hydraulic cylinder piston rod. The displacement error between the target position command and the current position is calculated as the input signal of the position control loop in the electrohydrostatic actuator control system; S2. A controller of the electro-hydrostatic actuator control system processes the displacement error based on a proportional-integral-differential control law and generates a speed reference signal in combination with a load disturbance feedforward compensation model, wherein the load disturbance feedforward compensation model uses a state observer to estimate the external disturbance load torque and superimposes it on the control signal; S3, inputting the speed reference signal into a speed control loop, constructing a sliding mode surface function using an adaptive sliding mode control method, and generating a current command based on the speed error, wherein the speed control loop includes a disturbance estimator and a boundary layer switching function module; S4. Input the current command into the current control loop, calculate the d-axis voltage command and the q-axis voltage command respectively through a decoupling vector control method based on the dq-axis electrical model of the permanent magnet synchronous servo motor, and compensate for the motor back electromotive force and electrical coupling term; S5. Convert the d-axis voltage command and the q-axis voltage command into a three-phase PWM control signal via a power drive module to drive the permanent magnet synchronous servo motor to rotate, thereby driving the gear pump to output hydraulic oil and push the piston rod of the hydraulic cylinder; S6. Based on the historical control signals and the estimated load disturbance data within the current control cycle, a dynamic hysteresis compensation module is established to correct the nonlinear hysteresis error caused by the compressibility of the oil inside the hydraulic cylinder and the friction of the valve core. The dynamic hysteresis compensation module is periodically updated within the controller and superimposed on the control channel; S7. During the operation of the electric hydrostatic actuator drive control system, the servo motor current signal, DC bus voltage signal, servo motor speed signal and hydraulic cylinder piston rod displacement signal are collected in real time. If any of the signals exceeds the preset safety threshold, the controller's internal fault processing module is triggered to shut down the power output path and send a fault code to the host computer through the communication interface.

2. The dynamic hysteresis compensation method for three-closed-loop control of an EHA drive control system according to claim 1, characterized in that: Said S1 specifically includes: S11. The host computer sends a target position instruction to the electro-hydrostatic actuator controller through a communication interface, wherein the target position instruction is a value in millimeters; S12, a linear displacement sensor is provided at the end of the hydraulic cylinder piston rod to measure the current position of the hydraulic cylinder piston rod and output a displacement signal in millimeters; S13, the electro-hydrostatic actuator controller calculates a displacement error signal according to the target position command and the current position; S14. The electro-hydrostatic actuator controller updates the target position command, current position and displacement error signal at a fixed sampling period, and inputs the displacement error signal into the position control loop.

3. The dynamic hysteresis compensation method for three-closed-loop control of an EHA drive control system according to claim 1, characterized in that: The S2 specifically includes: S21, the electro-hydrostatic actuator controller inputs the displacement error signal into the position control loop, executes the proportional-integral-differential control law consisting of the superposition of the proportional term, the integral term, and the differential term, and obtains a preliminary speed reference signal; S22, the electro-hydrostatic actuator controller estimates the disturbed load torque τ of the hydraulic cylinder based on the state observation model f , the state observation model is: Among them, τ f Denotes the disturbance load torque, K t Represents the motor torque constant, J eq Denotes the equivalent moment of inertia of the system, B eq represents the equivalent damping coefficient, ω m Indicates the servo motor speed, Indicates the acceleration of the servo motor; S23, the electro-hydrostatic actuator controller converts the disturbance load torque τ f It is superimposed with the preliminary speed reference signal output by the proportional-integral-differential control law to form a corrected speed reference signal; S24. The electro-hydrostatic actuator controller inputs the corrected speed reference signal into the speed control loop in the electro-hydrostatic actuator control system, and uses the corrected speed reference signal as an input signal of the sliding mode control algorithm in the speed control loop to participate in the next current command generation calculation.

4. The dynamic hysteresis compensation method for three-closed-loop control of an EHA drive control system according to claim 1, characterized in that: The S3 specifically includes: S31, the electro-hydrostatic actuator controller compares the speed reference signal with the current speed of the servo motor to obtain a speed error signal e v ; S32. The electric hydrostatic actuator controller constructs a sliding surface function s based on the velocity error signal. The sliding surface function expression is: Among them, s is the sliding surface function, e v is the speed error, is the first-order derivative of the velocity error, β is the sliding surface convergence rate coefficient; S33, the electric hydrostatic actuator controller sets the switching function and constructs the control law, which includes the proportional-integral term, the sliding mode term and the disturbance estimation term. The sliding mode control current command u smc The calculation formula is: Among them, K vo Proportional gain, K vi is the integral gain, λ is the sliding mode gain, is the boundary layer thickness, sat(·) is the saturation function, is the disturbance term estimated online; S34. The electric hydrostatic actuator controller inputs the sliding mode control current command output by the control law into the current control loop.

5. The dynamic hysteresis compensation method for three-closed-loop control of an EHA drive control system according to claim 1, characterized in that: The S4 specifically includes: S41, the electric hydrostatic actuator controller decomposes the current command output by the speed control loop into the d-axis current command i d and q-axis current command i q , and calculate the target driving voltage command v d With v q ; S42. The electric hydrostatic actuator controller calculates the drive voltages of the d-axis and q-axis based on the electrical model of the permanent magnet synchronous servo motor. The control formula is: Among them, v d ,v q is the d-axis and q-axis driving voltage command, i d ,i q is the actual current of d-axis and q-axis, R s is the stator resistance, L d ,L q is the d-axis and q-axis inductance, ω e is the motor electrical angular velocity, ψ f is the permanent magnet flux; S43, Electrohydrostatic Actuator Controller Calculation Cross-coupling Term -ω e ·L q ·i q With +ω e ·(L d ·i d +ψ f ), and perform decoupling compensation operations between voltage channels; S44, the electro-hydrostatic actuator controller sets the target drive voltage instruction v d With v q Input to the power drive module and output three-phase PWM control signal to the permanent magnet synchronous servo motor.

6. The dynamic hysteresis compensation method for three-closed-loop control of an EHA drive control system according to claim 1, characterized in that: The S6 specifically includes: S61, the electric hydrostatic actuator controller records the control input signal u(t-Δt) and the current position of the hydraulic cylinder piston rod θ(t-Δt) in the previous cycle during the control cycle, and combines the load disturbance estimation value τ collected in the current cycle f (t), forming the dynamic hysteresis compensation input vector; S62: The electro-hydrostatic actuator controller constructs a dynamic hysteresis compensation model based on the input vector and uses the following form to perform error estimation: Dth hyst (t)=α1·u(t-Δt)+α2·τ f (t)+α3·θ(t-Δt); Where Δθ hyst (t) is the estimated value of the hysteresis error, u(t-Δt) is the control input signal, τ f (t) is the disturbance load torque, θ(t-Δt) is the piston rod displacement in the previous cycle, and α1, α2, and α3 are the hysteresis modeling coefficients; S63, the electro-hydrostatic actuator controller calculates the hysteresis error estimate Δθ hyst (t) is subtracted from the position control path to form the corrected position feedback signal: i corr (t)=θ(t)-Δθ hyst (t); Among them, θ corr (t) represents the corrected position input signal; S64, the electro-hydrostatic actuator controller inputs the corrected position signal θ (orr (t) Replace the original feedback position signal input to the position control loop to complete the online dynamic compensation of the hydraulic hysteresis effect.

7. The dynamic hysteresis compensation method for three-closed-loop control of an EHA drive control system according to claim 1, characterized in that: The S7 specifically includes: S71, the electric hydrostatic actuator controller collects the servo motor current signal, the DC bus voltage signal, the servo motor speed signal, and the hydraulic cylinder piston rod displacement signal in each control cycle; S72: The electro-hydrostatic actuator controller compares the four types of signals with their preset safety thresholds respectively. If any signal exceeds the corresponding threshold, it is determined to be an abnormal state. S73: The electric hydrostatic actuator controller responds to the abnormal state and immediately shuts down the PWM output signal of the power drive module, thereby blocking the drive channel to the servo motor. S74: The electric hydrostatic actuator controller sends a fault code to the host computer through the CAN FD communication interface, and simultaneously drives the fault status indicator light to light up and the operation status indicator light to turn off, completing the fault prompt action.

8. An EHA drive control system three-closed-loop control system, applied to the EHA drive control system three-closed-loop control dynamic hysteresis compensation method according to any one of claims 1 to 7, characterized in that: Includes the following modules: Electric hydrostatic actuator controller module: used to implement a three-loop control strategy based on position control loop, speed control loop, and current control loop; Host computer module: connected to the electric hydrostatic actuator controller and sends a target position command signal; Linear displacement sensor module: installed at the end of the hydraulic cylinder piston rod, collects the current position of the hydraulic cylinder piston rod and outputs the current position signal to the electric hydrostatic actuator controller; Servo motor encoder module: installed at the end of the permanent magnet synchronous servo motor shaft, collects the motor's speed and position signals and outputs them to the electro-hydrostatic actuator controller; Three-phase permanent magnet synchronous servo motor module: receives the PWM control signal output by the electro-hydrostatic actuator controller and drives the connected gear pump to rotate; Gear pump module: driven by the servo motor to rotate and output hydraulic oil; Hydraulic system component module: includes a hydraulically controlled one-way valve, a relief valve and a hydraulic cylinder. Hydraulic oil is input into the hydraulic cylinder after being controlled by the hydraulic system component, causing the piston rod to produce linear displacement; Power drive module: Equipped with a SiC MOSFET three-phase full-bridge structure, it receives the d-axis and q-axis voltage command signals output by the electro-hydrostatic actuator controller, generates a three-phase PWM control signal, and outputs it to the servo motor; Current detection module: configured at the input end of the electric hydrostatic actuator controller to collect the servo motor bus current signal; DC bus voltage detection module: collects the DC bus voltage value of the system and feeds it back to the electric hydrostatic actuator controller.

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