Nonlinear integral sliding mode variable structure control for electro-hydraulic servo system
The integral sliding mode controller may lead to the deterioration of the transient performance or even instability of the electro-hydraulic servo system when there is an initial error.To address the problem,we propose a nonlinear integral sliding mode variable structure control method.First,considering the uncertainty of the system and the problem of external disturbance,the nonlinear mathematical model of the electro-hydraulic servo system is built.Then,a nonlinear function which enlarges the small error and saturates the large error is introduced to the integral sliding mode surface to form a nonlinear integral sliding mode surface and the stability of the system under this control method is proved by Lyapunov stability theory.Finally,the models of the electro-hydraulic servo system and the nonlinear integral sliding mode controller are built in the Matlab/Simulink environment.Our results are compared with the simulation results of the sliding mode controller and the integral sliding mode controller.They suggest the controller eliminates the overshoot of the system and shortens the adjustment time by 43.33%compared with the integral sliding mode controller.The displacement tracking accuracy is improved by 40.16%compared with that of the sliding mode controller.Therefore,the electro-hydraulic servo system with nonlinear integral sliding mode controller improves the tracking accuracy and the transient performance of the system.
electro-hydraulic servo systemnonlinear integral sliding mode controllerposition trackingtransient performance
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