Research On Multi-cylinder Hydraulic Machine Control Based On Discrete-time Sliding Mode Control

Owing to the strong non-linearity and redundancy of the multi-cylinder hydraulic system,it is difficult to establish the non-linear model and complex to design the overall controller.The number of existing control strategies for multi-cylinder hydraulic system is small,and many problems have still to be solved and improved.In view of the above problems,the following research work has been carried out around the control of a five-cylinder hydraulic press:First,a system decomposition multi-level control method based on control allocation is proposed for complex redundant systems,which deal with the coupling between subsystems by decomposing the complex redundant system into a series of simple and controllable subsystems and introducing control allocation methods in every two levels subsystem.This paper also designs a discrete-time model of the five-cylinder hydraulic system on this basis,achieves the control of the five-cylinder hydraulic system by introducing a discrete sliding mode controller,and establishes the effectiveness of the proposed control strategy using MATLAB simulation experiments.Secondly,in view of the problems existing in the existing discrete-time sliding mode control methods,such as the difficulty of chattering elimination and adjustment steps reduction simultaneously,the problem of eliminates steady-state oscillation and several proven problems in stability analysis,a combined reaching law form based on two-parameter adjustment function is proposed,which provides a new solution for chattering elimination and adjustment steps reduction simultaneously,and to eliminate steady-state oscillation.Moreover,the accurate expression of quasi-sliding-mode domain width and a proof form for eliminates steady-state oscillation are proposed in the stability analysis.The effectiveness of the proposed discrete-time sliding mode control method is verified by MATLAB and piezoelectric actuator experiments.Finally,the final five-cylinder hydraulic system controller is designed to preliminaries verify the proposed method effectiveness using MATLAB numerical simulation by combining the proposed control strategy with the sliding mode controller.After that,Lab VIEW control program and overall experimental flow are designed according to the customary five-cylinder hydraulic system.The effectiveness of the proposed method in real control is demonstrated experimentally.In conclusion,the proposed control strategy and discrete-time sliding mode control method resolve the problems of complex controller design,difficult control and poor control effect for complex redundant system of five-cylinder hydraulic press.In addition,the stability analysis method of discrete-time sliding mode reaching law is supplemented and improved,which further promotes the research and development of sliding mode control.