Sliding Mode Variable Structure Control And Its Application Research For Electro-Hydraulic Position Servo Systems

Firstly this paper introduces the composition and the development of the electro-hydraulic servo control system, and analyses nonlinear characteristic and uncertainties of the electro-hydraulic servo control system along with their causes, then the development and research status quo of the sliding mode variable structure control is introduced. As a robust-control method, variable structure control can effectively control the systems which exist parameters uncertainties and disturbance by adjusting and changing the controller, which is consistent with the control requirements of electro-hydraulic servo control system including uncertainties (parameters uncertainties, external disturbances and nonlinearities), therefore sliding mode variable structure control theory is highly regarded in the design of electro-hydraulic servo control system. In order to apply to electro-hydraulic servo control system, the paper elaborates on basic concepts and basic issues of the variable structure control, and establishes the mathematical models of all parts in electro-hydraulic servo system, so theoretical model of electro-hydraulic servo system is formed. From the laboratory, parameters involved in the hydraulic cylinders and the servo valve and other parts of electro-hydraulic servo system are measured and calculated, then the every transfer function of the components is determined, and ultimately the system's transfer function block diagram is determined.After the establishment of the electro-hydraulic servo system model, sliding controller is also designed using the proportion switch control of the sliding mode variable structure control theory, and using S-function describes models of the sliding mode controller and electro-hydraulic servo system, then simulation model of the whole system is established in Matlab/Simulink. When the system exists uncertainties, the author compares sliding mode control with PID control adopting step signal and sine signal as a reference. The simulation results show that: sliding mode control algorithm is better than PID algorithm. In order to establish a more precise model of the hydraulic system and improve the performance of the whole control system, the paper has also established co-simulation platform based on ARMSim/Simulink, and made comparative study of the simulation between a sliding mode control and PID control. In addition, control performance of the model established in co-simulation platform is compared with that in Matlab/Simulink simulation platform, the results show that: sliding mode control system has faster response time, better static and dynamic performance and more robust than PID control system in Simulink simulation platform; in ARMSim/Simulink co-simulation platform, response time of variable structure control system is also less than the PID control system; on the whole, control performance in ARMSim/Simulink co-simulation platform is better than Simulink simulation platform.