Research On Robust Control For Speed System Of Tandem Cold Rolling Mill

Based on Shanghai Bao Steel Co. practical project, which is modeling, simulating of dynamic rolling procedure and control optimizing for cold continuing rolling mill, the research of control optimization on the speed control system is studied. The varieties of interior parameter and exterior load disturbance and the presence of saturation nonlinear have great influence on the dynamic process and tracking effect of the system, so there are practical meanings and theory values to apply robust control methods to speed system.The development and status quo of robust control theory is summarized. Then the norm of system, H_∞ control problem bounded real lemma andLinear Matrix Inequalities(LMI) are introduced, and the basic structure and parameters of the speed system for each stand of the cold continuing rolling mill are presented. Three kinds of controller designing methods based on H∞ control and integrator backstepping are introduced. First, a H∞ state feedback robust controller is designed for speed system with time-varying parameters brought by the varieties of rotating inertia and motor torque coefficient during the field weakening process and load disturbance. Second, the sufficient conditions which are expressed by three inequalities to satisfy invariance of closed-loop system and L2 performance of disturbanceattenuation are presented for the speed system with actuator saturation and bounded disturbance. Fixing some parameters and using Schur theorem, three LMIs and the robust state feedback controller are developed. Finally controller designing based on integrator backstepping is presented. Through gradual correcting arithmetic, an unperturbed controller is designed and global regulation or tracking is achieved. In each step, the change of state coordinate, a known Lyapunov function and virtual control are connected and a control Lyapunov function(clf) is derived finally. The simulation results show that the designed speed system has good performance in the dynamic and static accuracy.