Extended state observer based nonsingular terminal sliding-mode control for non-sinusoidal oscillation of continuous casting mold driven by servo motor
A new driving mode that using servo motor to drive continuous casting mold oscillated following the expected non-sinusoidal (include sinusoidal) is introduced. For this system, the integral nonlinear mathematical model is built, which contains the nonlinear model of servo motor and the mechanical transmission parts of the mold. Because the servo motor rotates continuously in single direction while the oscillation waveform of the mold is nonlinear periodic function, firstly, establish the mapping between them to solve the irreversible of this system, and use a third-order tracking differentiator (TD) which has high-speed tracking ability and good tracking precision to track the result of the mapping function and obtain its derivative signal simultaneously. Then a new type of control scheme combined the extended state observer (ESO) with nonsingular terminal sliding-mode control is adopted in investigation. The controller is designed for the integral system by adopting a non-singular terminal sliding mode manifold and can make the singularity avoided by preventing differentiating terms deriving the control laws and applying a continuous control strategy to resolve the chattering. Meanwhile, the ESO is designed to estimate the states and the lumped uncertain disturbances accurately without requiring exact mathematical model and the sensors. The proposed controller can guarantee stabilization of the tracing system. Simulated results are provided to demonstrate the effectiveness of the proposed control scheme.