Abstract: Considering unstable oscillation in the process of rolling mill caused by lubrication condition change between roller and rolled piece, and characteristics of complex electromechanical coupling in main drive system, the nonlinear dynamics equation of coupled electromechanical drive system of rolling mill is established with nonlinear friction drag based on Lagrange-Maxwell theory. According to dynamical bifurcation theory the stability of system is analyzed, and the necessary and sufficient condition of Hopf bifurcation and periodic motion’s stability are given, besides that, the influence of supercritical and subcritical bifurcation on torsional vibration is analyzed. In order to suppress instability oscillation of drive system caused by Hopf bifurcation, a nonlinear feedback controller is proposed, choosing stator voltage of drive electric motor as control variable and motor velocity as state feedback, and controller parameters are determined by using multi-scale and harmonic balance method. After including the controller, the Hopf bifurcation points of system can be thansferred, and the stability and amplitude of limit cycle are controlled. This control method is simple and easy to put into practice. Numerical simulation verifies the effectiveness of the designed controller.

Key words: Hopf bifurcation, Electromechanical coupling system, Limit cycle, Main drive system of rolling mill, Nonlinear feedback control