Nonlinear torsional vibration analysis of motor rotor system in shearer semi-direct drive cutting unit under electromagnetic and load excitation

Abstract

Under the influence of electromagnetic excitation and terminal loads disturbance, the motor rotor shaft of the semi-direct cutting section of a shearer may produce electromechanical coupling resonance. Against this background, this work investigates the vibration properties of a motor rotor and the effect of electromechanical couplings. According to the electric machine theory and the Maxwell equation, the electromechanically coupled nonlinear torsional vibration model for the rotor system is first established under the influence of electromagnetic excitation and terminal load disturbance. Besides, its approximate solution is derived through the multi-scale method in the case of main parametric resonance, and the steady-state solution is determined through the numerical method. Moreover, the electromagnetic parameters including internal power factor angle, permanent magnet coefficient, number of pole pairs, and magnetic saturation coefficient and the mechanical parameters such as torsional stiffness of rotor and terminal load, which are responsible for the torsional vibration of rotor system, are studied, respectively. The results show that the stiffness failure and load mutation could cause chaotic motions, and a reasonable selection of electromagnetic and mechanical parameters for the permanent magnet synchronous motor (PMSM) could prevent the jumping and bifurcation from happening. This work is expected to benefit, both theoretically and practically, the design, optimization, and diagnosis of high-performance shearers that are operated in a complex working environment.