Research On Nonlinear Control Method Of Hydraulic Machine Based On Adaptive Fault Tolerance Strategy

This paper aims at a kind of electro-hydraulic servo system with affine nonlinear,analyzes its existing control strategy and existing problems,tries to solve some hot spots and difficult problems,and tries to propose the related advanced control strategy.The following aspects are studied:Firstly,this paper summarizes the current development status of hydraulic press control at home and abroad,points out the current deficiencies in the control of single cylinder and multi-cylinder hydraulic press,especially in the case of parameter time-varying,system failure,control system research blank,and leads to the main research content of this paper.Secondly,a control law based on feedback linearization is derived for a class of electro-hydraulic servo systems with nonlinear and uncertain parameters by using Lyapunov theory,in which the uncertainty of initial volume and bulk modulus is considered.The control law can be adjusted automatically according to the change of initial volume,thus the problem that control precision is reduced by the difficulty of measuring the volume of long pipe is solved.The simulation results show that the controller has high control precision and strong robustness,and it has good control performance compared with the traditional controller.Thirdly,an adaptive fault-tolerant control allocation method based on sliding mode is proposed for a class of multi-cylinder hydraulic press.This method not only considers the problem of single actuator failure,but also meet the performance requirements when all the actuators present failure simultaneously.The control scheme includes three separate control parts,namely virtual control part,control allocation part and actuator control part.Firstly,the three virtual control are designed by the integral sliding mode method.Secondly the virtual control are assigned to the hydraulic cylinder actuators by weighted matrix pseudo-inverse method and the desired output force are obtained.Finally the high-precision control of the system is achieved by adjusting the valve opening area of the hydraulic valve.The advantage of this method is that when a certain hydraulic cylinder fails,the control allocation part uses fault-tolerant control allocation method to compensate the loss to healthy actuators;When multiple hydraulic cylinders fail at the same time,the on-line adaptive control method is proposed to solve the problem of the virtual control error.This method can adjust the control gain of the high-level sliding mode controller,thus the influence of the virtual control error is eliminated,and the stability of the closed-loop system is maintained.In summary,according to the characteristics of non-linearity,time variation of parameters and redundancy of multi-cylinder,the present control strategy is improvedto solve the problem of demotion of control performance caused by time variation of parameters of single-cylinder hydraulic machine,as well as the problem of fault tolerant control allocation of multi-cylinder hydraulic machines.It not only makes up for the gaps in fault tolerant control in the hydraulic field,but also further promotes research field of nonlinear control.