Electro-hydraulic Position Servo Research Articles

A backstepping sliding mode control algorithm of electro-hydraulic position servo system of valve-controlled symmetric cylinder based on extended state observer

Electro-hydraulic position servo system of valve-controlled symmetrical cylinder (EPSSVCS) is a very important and widely used electro-hydraulic servo system, the performance of which is often affected by friction nonlinearity and external random disturbances together with unmodeled dynamic factors such as parameter uncertainty in practical work. To improve the tracking performance of the system, a backstepping sliding mode control algorithm (BSMC) based on an extended state observer was presented in this paper. Firstly, a nonlinear mathematical model of the EPSSVCS was established which takes into account the composite disturbance induced by the systematic friction nonlinearity, external disturbances and unmodeled dynamic factors. Then, an extended state observer (ESO) was designed which can effectively estimate the velocity, acceleration, and composite disturbance of the valve-controlled cylinder online. Furthermore, a kind of BSMC was presented based on the online ESO estimates and the displacement feedback signals. The control law was given and the system stability was proved. The analysis results showed that the output signal of the system can effectively track the input signal under the influence of typical external disturbances and unmodeled dynamic factors, which illustrated the effectiveness of the established nonlinear mathematical model and the stability of the designed control system. Moreover, by taking the parameters of the electro-hydraulic servo system of a certain type of CNC machine tool as a real example, the proposed algorithm (BSMC) was compared with the conventional PID control algorithm, the backstepping sliding mode control algorithm (BSC), and the adaptive robust control algorithm (ARC), and the results verified the superiority of the BSMC. This work may provide a useful reference for the research in the field of related control systems.

Research on control of electro-hydraulic servo system based on third-order linear ADRC

PurposeThe purpose of this paper is to design a third-order linear active disturbance rejection controller (LADRC) to improve the response characteristics and robustness of the electrohydraulic servo system.Design/methodology/approachThe LADRC was designed by replacing the nonlinear functions in each part of ADRC with linear functions or linear combinations, and the parameters of each part of the LADRC were connected with their bandwidth through the pole configuration method to reduce the required tuning parameters, and used an improved grey wolf optimizer to tune the LADRC parameters.FindingsThe anti-interference control simulation and experiment on the LADRC, ADRC and proportion integration differentiation (PID) were carried out to test the robustness, anti-interference ability and superiority of the designed LADRC. The simulation and experiment results showed that the LADRC control and anti-interference control had excellent performance, and because of its simple structure and fewer parameters, LADRC was easier to implement and had a better control effect and anti-interference.Originality/valueFor the problems of parameter perturbation, unknown interference and inaccurate model in the electrohydraulic position servo system, the designed third-order LADRC has good tracking accuracy and anti-interference, has few parameters and is conducive to promotion.

Research on High-Precision Position Control of Valve-Controlled Cylinders Based on Variable Structure Control

During the operation of valve-controlled cylinder position systems, there are some problems, such as uncertainty and time-varying of the system parameters, imprecise modeling, and external interference. These problems will affect the position loading accuracy and safety reliability of the electro-hydraulic position servo system. This paper used the position servo system of a valve-controlled cylinder as the research object, and a mathematical model was established. Then, a sliding mode variable structure controller and dynamic soft variable structure controller were designed, and the Grey Wolf algorithm was used to adjust the controller parameters. The control effect of the two controllers in the valve-controlled cylinder system was verified with a simulation and experiment. The results showed that compared with the sliding mode variable structure controller, the dynamic soft variable structure controller had higher control precision and better stability and avoided the chattering phenomenon.

Disturbance Observer based Backstepping Control for Electro-hydraulic Position Servo System of the Projectile Coordination Arm

Due to the existence of unmodeled friction and unknown load disturbance, the position tracking control of electro-hydraulic position servo system of projectile coordination arm becomes an important problem to be solved urgently. In this paper, a dynamic surface backstepping control strategy is proposed based on the disturbance observer(DOB). To be specific, the disturbance observer is applied to estimate the unknown disturbance force, and the backstepping controller realizes the position tracking control. In order to improve the position tracking performance, The estimated value of the observer output is brought into the backstepping controller to realize the model compensation of the disturbance. Meanwhile, the dynamic surface method is utilized to handle the differential explosion problem in the backstepping method. The global stability of the closed-loop system is verified by Lyapunov stability theory. The co-simulation results show that the proposed method can effectively compensate the unknown disturbance in the electro-hydraulic position servo system, and has better tracking performance and strong robustness.

Sliding Mode Control of Electro-Hydraulic Position Servo System Based on Adaptive Reaching Law

For the problem of the system state variable taking a long time to reach the sliding mode surface and the chattering frequency being high in the sliding mode surface, a sliding mode control method based on the adaptive reaching law is proposed, the system state variable is introduced based on the subreaching law, and an improved variable-speed reaching law is added with reference to the characteristics of the hyperbolic tangent function. The sliding mode control method is divided into two stages, namely, the initial state to the critical value s = ±1 and the system state variable reaching the equilibrium point of the sliding mode surface, and the total time obtained is less than the sum of these two stages. Secondly, this method is adopted in the electro-hydraulic position servo system, and a sliding mode controller is established. Through an AMESim/Simulink co-simulation, it is compared with the sliding mode controller based on the traditional exponential reaching law. The results show that this method can effectively reduce the jitter of the system, reduce the time for the system to reach the sliding surface, and improve the robustness of the system.

A multi-model based adaptive reconfiguration control scheme for an electro-hydraulic position servo system

A multi-model based adaptive reconfiguration control scheme for an electro-hydraulic position servo system

Optimal robust adaptive fuzzy backstepping control of electro-hydraulic servo position system

In this paper, an optimal robust adaptive fuzzy backstepping control is presented to the position control of the electro-hydraulic servo (EHS) system in the presence of structured and unstructured uncertainties. Initially, the robust control using the backstepping technique is presented to overcome the existing uncertainties in the dynamic equations. Mathematical proof demonstrates that the closed-loop system in the presence of uncertainties has a global asymptotic stability. Then, to overcome the chattering problem, a very simple fuzzy approximator is presented where it approximates the bounds of the uncertainties. Although the proposed robust fuzzy backstepping control has a desirable performance, it has no mathematical analysis to prove the stability of the closed-loop system. Therefore, to solve this problem, the proposed fuzzy approximator has been transformed into a one-law adaptive fuzzy approximator with a single-input single-output fuzzy rule. Mathematical analysis illustrates that the closed-loop system in the presence of uncertainties has a global asymptotic stability under the proposed robust adaptive fuzzy backstepping control. Furthermore, a novel modified harmony search algorithm (MHSA) has been developed, by using the original harmony search algorithm (OHSA) as an optimization technique, to achieve the optimal values of the membership functions and the control coefficients. Finally, a comparative study has been conducted between the proposed control scheme under the MHSA and the OHSA, and other existing advanced control approaches to verify the effectiveness of the proposed control. Results show that the proposed control scheme under the MHSA can suppress the chattering problem and reduce the disturbances effectively while ensuring that the performance is tracked.

Electro-hydraulic position servo system based on sliding mode active disturbance rejection compound control

This study proposes a compound control method based on sliding mode and active disturbance rejection control to address the difficulty of controlling the cutting head for boom-type roadheader with parameter changes and uncertain disturbances. The fastest discrete tracking differentiator and extended state observer based on the traditional active disturbance rejection control are designed. Additionally, the controller of the sliding mode and active disturbance rejection control is constructed. Theoretical analysis indicates that the proposed controller ensures asymptotic stability, despite the existing uncertain disturbances. Moreover, a system based on AMESim and MATLAB/Simulink Co-simulation model is developed to further verify the performance of proposed algorithm. Compared with traditional active disturbance rejection control, proportional-integral-derivative(PID) and sliding mode control, co-simulation results demonstrate that the sliding mode active disturbance rejection compound control improves the tracking accuracy and robustness of the position servo system.

Trajectory control of electro-hydraulic position servo system using improved PSO-PID controller

This paper presents an improved particle swarm optimization (PSO) algorithm to optimize the coefficients of the proportional integral derivative (PID) controller for trajectory tracking accuracy problems. Nonlinear adaptive methods are adopted on the inertia weight to built a balance between the local and global search areas, asynchronous change strategies are introduced into the learning coefficients to rationally use individual and group experience, an elite mutation method is designed to mutate the global best position in each iteration. Basic PSO (BPSO-PID) and Ziegler-Nichols PID controller (ZN-PID) are implemented with step, sinusoidal and slope references on a co-simulation platform. The simulation results illustrate that high accuracy and fast convergence can be obtained based on the improved PSO algorithm PID controller (IPSO-PID). Experimental results demonstrated that the IPSO-PID method can achieve the highest tracking accuracy, compared with the BPSO-PID method, this method can improve the tracking accuracy by 37.14% and 50.32%, respectively.

Linear active disturbance rejection control for the electro-hydraulic position servo system.

Valve-controlled asymmetric cylinder is widely used in servo loading system. As a kind of typical electro-hydraulic servo system (EHSS), it inherently has the characteristics such as high order nonlinear, strong coupling, and uncertain, therefore, conventional control strategy is difficult to satisfy the requirements of high-performance control. In this paper, a novel linear active disturbance rejection control (LADRC) method was proposed, in which the internal and external disturbances were actively estimated by the third-order linear extended state observer (LESO) in real-time, and rejected by the control law of proportional integral control (PID) with acceleration feed-forward. The stability of the proposed method was proved, and the influence rules of the LADRC parameters on the control performance were revealed by simulation. Finally, comparative experiments between LADRC and PID control were carried out, results showed that the disturbances can be effectively compensated and the control goals can be successfully achieved with the proposed method.

Adaptive sliding mode control of electro-hydraulic servo system based on RBF network

In order to solve the steady-state error in position tracking control for electro-hydraulic servo universal testing machine, caused by uncertain parameters in the system model, an adaptive sliding mode control strategy based on RBF neural network is proposed for this situation. This paper utilizes the adaptive ability of RBF neural network to improve the control quality of the electro-hydraulic position servo system. The strategy has three parts: the equivalent control, the reaching law control and the compensation control based on RBF network. Simulations verify that the control system can track the reference curve well with unknown parameters.

Stable Switching Control Strategy of the Support Pressure and Velocity of Shield Machine Gripper Shoes

An electro-hydraulic servo position and pressure compound control method was investigated considering the working principle of a hydraulic stepping motor of a shield machine gripper shoe and its practical working characteristics in the supporting process. The control targets were to improve the support efficiency and reduce the disturbance of gripper shoes on the surrounding rock. In this method, a fuzzy switching controller was used to switch between electro-hydraulic position control and electro-hydraulic pressure control. Numerical and prototype simulation experiments were conducted on the control method. The theoretical analysis and experimental results showed that the control method could effectively convert the gripper shoes from an unsupported state to a supported state in a short amount of time, as well as realize surge-free switching between position control and pressure control. Thus, disturbance of the gripper shoes on the surrounding rock could be reduced. The results of this study provide a theoretical basis for research on control strategies of hydraulic stepping propulsion of shield machines.

Faults Detection Using Sliding Mode Observer and Its Application on Elevating Servo Systems

The elevating servo system (ESS) of vehicle-mounted howitzer (VMH) is a typical closed-loop electrohydraulic position servo system, and the faults of its actuator and sensor seriously affect the safety and reliability of the system. In practice, model uncertainty, nonlinearities, unknown disturbance, and output noise present enormous challenges to conduct fault detection of the system. In the current paper, an online fault detection scheme using the sliding mode technology is proposed. Not only the derivation method of state equation and some common fault expressions but also a new design of sliding mode observer with the ability to eliminate the influences of the above factors on detection results is given. The observer’s parameter matrices are obtained by the linear matrix inequality. To promote the fault detection capability, a statistical-based dynamic threshold is developed to detect actuator faults and sensor faults simultaneously. Finally, experimental studies are implemented on a test rig for validating the system model, and the results of four experiments show the effectiveness of proposed methods.

Adaptive Sliding Mode Control of a Nonlinear Electro-hydraulic Servo System for Position Tracking

In view of the electro-hydraulic position servo system with parameter uncertainty and bounded disturbances, an improved adaptive sliding mode control scheme is proposed. The mathematical model of the valve-controlled system is first constructed with consideration of the external disturbance, matched and mismatched unknown parameters. Then, the parametric adaptive estimation laws are established by Lyapunov technique to estimate the generalized uncertainty parameters, and the discontinuous projection algorithm is used to ensure the boundedness of parameter estimation. In order to eliminate the chattering phenomenon in sliding mode control, the saturation function is designed to replace the sign function and the gain coefficient is adjustable on the sliding surface. Finally, the comparative experimental results clarify that the proposed control scheme has better control performance than the PID controller and the SMC controller.

Semi‐physical real‐time control of electro‐hydraulic proportional position servo system based on Matlab/xPC

A set of semi-physical simulation system based on real-time working simulation platform tools (Matlab/RTW) was established for electro-hydraulic proportional position servo system in the development of missile weapons and other equipment. The system is mainly composed of hydraulic system consisting of hydraulic actuators and Simulink simulation model. It is a closed-loop real-time simulation system of physical equipment in the loop. The simulation and experiment of proportional servo control system show that the system has high simulation real-time performance, the positioning accuracy and control stability. Two controllers are designed for different application conditions, which can obtain the good practicality and feasibility.

PID–PFC control of continuous rotary electro‐hydraulic servo motor applied to flight simulator

Due to the uncertainties caused by high non-linearity, friction, leakage and other external factors existing in the flight simulator with continuous rotary electro-hydraulic servo motor and the traditional control strategies discontenting with the high-performance requirements, the mathematical model of continuous rotary electro-hydraulic position servo system is established and the compound control theory combining proportional-integral-derivative (PID) and the predictive function control (PFC) method is proposed. In order to enable the servo system to estimate the influence of uncertainties and correct it by repeating online optimisation continuously, PID–PFC compound controller basing on the structure of internal model control is designed and then applied to continuous rotary electro hydraulic servo system. The simulation results show that compared with the traditional PID, PFC controller, PID–PFC compound control can effectively inhibit the interferences of the electro-hydraulic servo system, and greatly improve the response speed and tracking performances and expanding the system frequency band width. The accurate control of motor's position can be realised by applying PID–PFC compound control, which can make the servo system has stronger robustness.

An Electro-hydraulic Position Control System with Dual-controller Switching

This article focuses on the improvement of the control performance of the electro-hydraulic position servo system. A three-order state feedback (3OSF) controller is designed to eliminate static error. For the purpose that overcome the inadequacy due to high order in the 3OSF control system, a weighted switching algorithm in the finite frequency domain is adopted to realize the switching control using the 3OSF-2OSF dual-controller. Experiments show that the control system using the 3OSF-2OSF dual-controller weighted switching in the finite frequency domain has better dynamic performance and static performance than the control system using the 2OSF. Comparing with the threshold switching, the developed switching algorithm has smaller switching impact.

Research of Electro-Hydraulic Position Servo System Based on PID with Disturbance Observer

According to the characteristics of the electro-hydraulic position servo system of asymmetric hydraulic cylinder controlled by symmetric valve and its performance requirements, the PID controller based on disturbance observer is introduced. The improved controller can observe the equivalent disturbances and introduce the equivalent compensation to the control system, so it can achieve suppression of disturbance. In the MATLAB Simulink environment, the simulation results show that the controller has the very good quick response, the stronger robustness and the higher tracking precision.

Nonlinear robust control of valve controlled electro-hydraulic position servo system

Nonlinear robust control of valve controlled electro-hydraulic position servo system

Nonlinear Robust Adaptive Control of Electro-hydraulic Position Servo System

For the influence of time varying parameter on servo accuracy of electro-hydraulic position servo system, nonlinear robust adaptive controller with the ability of restraining the parameter perturbation for symmetry valves-control symmetry cylinder system is put forward which is based on the Lyapunov stability theory, The nonlinear state equation of symmetry valves-control symmetry cylinder system was derived, and the controller design process was given. the control strategy was verified on Co-simulation of MATLAB & AMESim and semi-physical simulation platform respectively, the simulation and experimental results show that the tracking performance of electro-hydraulic position servo with nonlinear robust adaptive controller meet the double ten index, and verify efficiency of the method presented through simulations. © 2014 SERSC.