Research On Adaptive Control Method Of Electro-hydraulic Servo System Based On Output Constraint

Electro-hydraulic servo system(EHS)is a valve-controlled servo system commontly used in actual production because of the fast response,high output power,and easy to realize various parameter feedback,et al.,but due to the manufacturing process and material physical characteristics defects the system has uncertain parameters such as unknown viscous damping coefficient,unknown leakage coefficient,load rigidity change,hydraulic oil volume elastic modulus parameter change and oil temperature change,et al.,which cannot accurately obtain numerical values resulting the reduces the dynamic performance,steady-state performance,and system stability margin during operation.For the above problems,after extensive literature research,this paper finally decided to adopt the parameter adaptive control method.The first step,combined with the characteristics of the electro-hydraulic servo system,builds a mathematical model of the electro-hydraulic servo position system;the second step,construct the parameter estimation rate and the adaptive controller to maintain good tracking performance in the case of unknown parameters or deviations.The third step is to further optimize the performance of the controller according to the characteristics of the electro-hydraulic servo system and the control effect of the controller.In order to enable EHS to avoid reduce system stability,and even cause instrument damage caused by excessive overshoot,this paper uses output constraint functions,including conversion function and barrier Lyapunov function(BLF)two output constraint algorithms to control the servo position of EHS.The barrier Lyapunov function can control the position parameter within the set range.If the position limit close the preset range,the barrier Lyapunov function will quickly tend to infinity.The application of the barrier Lyapunov function can not only improve the system in certain but also improve the sensitivity of the system.Different from the BLF,the transfer function is a relatively young algorithm,it is a dynamic output constraint method,which can ensure that the tracking error of the system is within the dynamic preset constraints to ensure the robustness of the system.In order to optimize the performance of the controller,this paper use the mapping function to constrain the estimated parameters to avoid reducing the dynamicperformance of the system caused by the estimated parameters are too large.Because this paper use the backstepping control method,so the control will present Higher order differential term.The higher-order differential terms will cause the controller to be complicated to build and will reduce the steady-state performance of the system.Therefore,this paper adopt dynamic surface control method to solve this problem.The dynamic surface control method is to use the first-order filter equation to convert the differential terms into fractions,thereby solve various problems caused by differential explosion.All controller derived in this paper are made simulation experiments using the Simulink module,and analyze the results of the simulation experiments.From the simulation results,it can be seen that compared with the traditional backstep adaptive controller,the with adaptive control method whit output constraints has faster response and better dynamic performance,and the tracking effect is obviously better than the traditional backstepping adaptive controller.In addition,this paper add additional algorithm to optimize the controller.The performance of the new controller finally obtained through simulation experiments is superior.