Research On Main Drive Control System Of Reversible Rolling Mill

Reversible rolling mill is the main equipment of cold rolled strip production, and its main drive control system is the system that drags strip reciprocally between the roll. The speed control effect of main drive control system has great impact on the flatness and thickness of strip, which are key performance indicators of strip. At present, motors of domestic and foreign main drive control system are mainly salient pole synchronous motors. Therefore the research on the control system of the motor has important application value and theoretical significance.This thesis bases on a stainless steel cold rolling production line and does research on the structure and control strategy of the main drive control system of the reversible rolling mill. Aiming at the problem of coupling between inductance matrix and rotor position angle in the model of salient pole synchronous motor, the thesis simplifies the inductance matrix into ordinary differential linear matrix which is lifting the coupling by coordinate rotation transform. Besides, the thesis introduces the field oriented coordinate system and establishes a motor model under the coordinates to facilitate the analysis and design of control systems.While using the air-gap flux-oriented vector control method, it is hard to design the control system because of the asymmetric magnetic circuit of salient pole synchronous motor. The thesis uses the stator flux oriented vector control method to design the system. Since the mathematical model of salient pole synchronous motor is complex, the thesis simplifies the model reasonably according to the project and designs double closed loop control of flux and speed to control the main drive system. Besides, according to the needs of flux control, this thesis designs a flux observer which offers a feedback signal to flux controller.Finally, through the simulation of the designed main drive control system, a larger overshoot of speed controller is found. The motor parameters often fluctuate and the load torque of motor changes nonlinearly in industry application, and these will exacerbate performance of speed controller as well as the performance of the system. Therefore, the thesis introduces the sliding mode variable structure control method to design the speed controller, it possesses a fast response to the set point and is not sensitive to the outside disturbance, and thus it can enhance the robustness of the controller.