Sliding Mode Variable Structure Controller Design On Torsional Vibration Suppression Of Rolling Mill Drive System

With the development of production and social progress, the demand of steel variety and quality becomes more and more demanding in the market. Also modern steel industry has struggled to conserve energy, increase product variety, improve product quality and organize production cleanly and safely. Rolling mill drive system is a multi-mass system, which is composed of some inertia components and flexible components. Especially the motor is connected to the roller by the long flexible shaft, so that the speed between the motor and the roller is not equivalent under the conditions of disturbance. This phenomenon is called torsional vibration. Under the conditions of torsional vibration, drive shaft of the rolling mill transfers not only the normal torque but also the torsional oscillation torque. The torsional oscillation will reduce the dynamic performance of the rolling mill drive system, impact rolling precision and quality of production, even damage mechanical equipments and threaten safe production.To solve the torsional vibration issue of rolling mill drive system, the paper regards the mechanical parts and the electrical parts of rolling mill drive system as a whole to research. In order to study the issue more conveniently, the paper simplifies the rolling mill drive system to two-mass system. The mathematical model of rolling mill drive system is established by utilizing dynamic equations of machinery. The paper analyzes the fundamental forms and characteristic of torsional vibration of rolling mill drive system, studies torsional vibration model of rolling mill drive system. It can be concluded from the analysis that rolling load disturbance is the main reason that causes torsional vibration.From the perspective of control, torsional vibration belongs to external disturbance of control system. So, torsional vibration suppression issue is a typical anti-disturbance issue of control system. Because sliding mode variable structure control can reject external disturbance, the paper employs sliding mode variable structure control to restrain torsional vibration. Also the paper analyzes the reasons of chatter and common methods of eliminating chatter. To eliminate the effect of chatter further, fuzzy control based on sliding mode variable structure control is proposed. Fuzzy sliding mode variable structure control combines the merits of fuzzy logic and sliding mode variable structure control. Simulation results have demonstrated that sliding mode variable structure control can not only satisfy the basic dynamic performance and steady performance, but also suppress torsional vibration of the drive shaft efficiently.