Research On Direct Drive Hydraulic Servo System Control Stratety

Hydraulic press is widely used in many fields such as automobile manufacture,non-ferrous metal smelting and other industries because of fast response and high loadcapability. However, valve control system designed on the basis of the principle of throttleoften causes the throttling loss, which makes that the energy utilization rate was lower. Inorder to solve this problem, relevant experts designed a new type of direct-drive hydraulicservo system to avoid the heating problem caused by increasing the system capacityproblem and to reduce the system complexity and cost. Aiming at the position trackingproblem of the new type of direct-drive type hydraulic servo system, many controlstrategies were presented and mathematical modeling was built up. The main works in thispaper as follow:Firstly, based on the direct drive hydraulic servo system position tracking problem,the system dynamics model was established. While considering zero discontinuousnon-differentiable functions and multiple target tracking system requirements, drivesubsystem, commutation subsystem and hydraulic servo drive subsystem dynamics modelwere built up.Secondly, in order to guarantee the hydraulic servo system has stronger stability andhigher tracking accuracy, combining the resistance for the parameters time-varyingperturbation and the response speed of sliding mode variable structure, a design method ofsliding mode variable structure controller was presented. A variable gain reaching law wasadopted to weaken the jitter of sliding mode controller output, which also can shorten thesliding time of arrival.Again, owing to the insensitivity of sliding mode variable structure control formismatching interference, the sliding mode variable structure controller based on extendedstate observer which was used for the compensation control was designed for the slidingmode variable structure controller.Finally, the simulation results show that based on the extended state observer variablegain of sliding mode variable structure controller can effectively reduce the tracking error,eliminate jitter, shorten the sliding time of arrival, and enhance the servo system’s dynamicperformance and robustness.