Study On Impact Torsional Vibration And Electromechanical Coupling Vibration Of Rolling Mill's Main Drive System

The torsional vibration phenomena occur frequently in rolling mill working processes has becoming a difficult and urgent research problem in the world. This study researched the nonlinear dynamics behavior of impact torsional vibration and the ruler and characteristic of torsional vibration based on strip mills. In the context of electromechanical coupling, this paper researched the self-oscillation because of structure parameter and nonlinear damping variation. Then a controller is proposed for restraining self-oscillation based on bifurcation control theory.Firstly, the fountainhead of torsional vibration in rolling mill's drive system is studied. Then, the dynamics equations of main drive system with nonlinear damping, nonlinear stiffness and dual nonlinear are established. Based on the equations, the torsional vibration of rolling mill can be analyzed further.Secondly, the dynamics equations of main drive system with nonlinear damping and nonlinear stiffness are established under the action of impact moment to deal with rolling mill's impact torsional vibration. The stability of system is analyzed. And the torsional vibration responses is obtained with the aid of multiple time scales method. By means of simulation, the influences of nonlinear factors on vibration responses are discussed, then the methods of impact vibration reduction are found.Thirdly, in order to solve the problem of low frequency vibration in rolling mill's drive system driven by AC motor, from the aspects of electromechanical coupling, the nonlinear dynamics equations of drive system are established which include the electromagnetic energy and mechanical energy. The nonlinear differential equations'approximate analytical solutions are solved with the aid of multiple time scales and harmonic balance, and more the normal form is yielded without the application of center manifold theory. According to the normal form, the periodic and quasi-periodic solutions'stability are analyzed by the theory of dynamical bifurcation, and further, the stable regions are given for each solution. The research above can supply a theory for the stable work of rolling mill.Finally, in order to solve unstable oscillation caused by nonlinear damping of the load, the electromechanical coupling dynamics equation with nonlinear damping of drive system are established based on Lagrange-Maxwell theory. According to dynamical bifurcation theory, the necessary and sufficient condition of Hopf bifurcation and periodic motion's stability are given. And a state feedback controller is proposed, which parameters can be obtained with the aid of multiple time scales and harmonic balance method. After including the controller, the Hopf bifurcation points of system can be transformed, and the stability and amplitudes of limit cycle are controlled. The analytical results are in good agreement with numerical simulations.