Study On Strongly Nonlinear Vibration Performance For Rolling Mill’s Electromechanicl Coupling Main Drive System

One major reason for the damage of rolling mill equipment is torsional vibration. The torsional vibration not only affects the quality of steel strip, reduces the endurance life of transmission parts, but also threats the whole drive system’s normal work. So the researches about the torsional vibration are of great practical significance.In this paper, an electromechanical coupling torsional vibration model of rolling mill’s main drive system driven by AC synchronous motor is established based on mechanical and electrical analytical dynamics. The strongly nonlinear vibration behavior under strongly nonlinear condition is studied using the incremental harmonic balance(IHB) method. The stability of the periodic solutions is examined according to the Floquet theory. The dynamic bifurcation behavior of the system with excitation amplitude is studied.Firstly, based on the electric motor principle and the electromagnetic field theory,the expressions of electromagnetic torque and electromagnetic stiffness are derived from the energy analysis perspective. Then a torsional vibration model of rolling mill main drive system driven by salient pole synchronous motor is established. It is found that the system is an electromechanical coupling system with strongly nonlinear characteristics.Secondly, according to the IHB method, the periodic solutions of the strongly nonlinear torsional vibration system are obtained. Compared with the fourth order Runge-Kutta method, the IHB method with one harmonic is not accurate enough, and the IHB method with three harmonics can achieve high calculation precision. When main resonance occurs, the system periodic solution is always a closed ring curve. While the behavior of the 3/1 super-harmonic solution will change with the excitation amplitude and the electromagnetic stiffness. The results presented in this paper contain both the quantitative and qualitative information.Thirdly, with varying different electromechanical parameters, the amplitudefrequency response curves of primary resonance and 3 ultra-harmonic resonance are obtained by the IHB method. The influences of different electrical and mechanical parameters on the resonance phenomena of the system are analyzed. It is noticed that with the increase of excitation amplitude or electromagnetic stiffness, the amplitude of torsional vibration and the resonance region of the system increased. And under the condition of primary resonance, multi-valued coexistence and jumping phenomena will occur.Finally, the stability of the periodic motions is investigated by the Floquet theory, and the bifurcation behavior is traced. Parametric studies are preformed to understand the effect of system parameters. With the increase of excitation amplitude, the period doubling bifurcation route leading to chaos is observed. It is found that the possibility for onset of chaotic motion is higher along with the increase of excitation amplitude. Our results are helpful for further understanding of dynamics and bifurcation mechanism in electromechanical coupling main drive system of rolling mill, which is important to the vibration suppression of rolling mill.