Two loops Control Based SMC for High Precision Tracking

A novel controller is designed for servo tracking system based sliding mode control, which is robust and insensitive to plant uncertainties and the external disturbances. The structure of the controller is two loops control realized easily in practice, made up of equivalent nonlinear PID controller in position loop and speed feedforward controller. A saturation function is proposed to design variable structure part of the SMC, which reduces magnitude of the control input and avoids great chattering. Simulation results indicate the proposed controller has great robustness and high performance. At last, the parameters in variable structure part and its influence to the system are analyzed. Some tracking results about different uncertainties are given