Modelling and control of hydraulic looper nonlinear multi-variable systems

In order to improve the control accuracy and quality of automatic gauges in hot trip rolling, a nonlinear muhiple-input multiple-output (MIMO) model of hydraulic loopers was built close to the working point in consideration of strip weight and the nonlinearity of hydraulic cylinders and loopers, and its validity was verified. A decoupling method based on back-stepping and extended state observers (ESO) was proposed for this new model taking all unmodelled dynamics and various disturbances into account. The robust stability of the closed-loop system was proved with the Lyapunov stability theory. Simulation results show that the proposed model and decoupling control method are available.