Backstepping Control Of Electro-hydraulic Servo System With Output Constraints

This paper introduces the research status and development history of electrohydraulic servo system,analyzes the nonlinear characteristics of the studied system and several factors that affect the performance,and designs the controller for output constraint condition.Compared to PID control,backstepping control is more inclusive and has more accurate control effect on the control of complex nonlinear systems,so this paper adopts the design of backstepping method,and in addition,backstepping control and other control methods are combined to solve the problem of constraint constraints.Firstly,the mathematical model of the system is constructed according to the working principle and dynamic characteristics of electro-hydraulic servo system,and then design the system control law.The first method is to combine the backstepping control with the Barrier Lyapunov function,both in theory and simulation results show that the control performance has been the ideal effect.but in the process of the design of the controller,the virtual control variable will face the problem of frequent differential,which makes the construction of the controller complex in the actual project,.In order to solve the technical difficulties,the second solutions are proposed,which combine the backstepping control,the barrier Lyapunov function and the dynamic surface control.This control method is mainly to make a dynamic surface by comparing the virtual variables before and after the filter and replace the derivation of virtual control with a dynamic surface.This solution avoids the problem of derivation,which is more easily applied in the actual system.In the end,this paper puts forward the combination of backstepping control and error tansformation technique which convert a constrained system into an unconstrained system through a performance function.In addition to the complexity of the construction of the error conversion function,the construction of the whole controller is more simple than the control method in the previous two.This control method also involves the derivation problem in the process of control law construction,so this paper also adds dynamic surface control based on this control method,so as to avoid the phenomenon of differential surge.In this paper,we design the controller of the electro-hydraulic servo system based on the output constraint.We build four controller with good performance under the condition of known parameters.In this paper,several control methods are combined to overcome the shortcomings of the single control method,so that the control law can not only guarantee the stability of the system,but also solve the problem of output constraint.