Analysis of the electromechanical coupling torsional vibration characteristics of an electric drive system under harmonic excitation

In the electric drive system of pure electric vehicles, harmonic excitation from the motor and mechanical excitation from gears interact via electromechanical coupling, easily inducing complex torsional vibration. Focusing on a representative electric drive system, this paper develops an electromagnetic torque model incorporating spatial and temporal harmonics, alongside a torsional vibration model for the gear transmission system that accounts for internal gear excitations. A closed-loop coupled mechatronic torsional vibration dynamic model is established through a torque-speed interface. Analysis of the system’s inherent characteristics identifies potential resonant speeds using a Campbell diagram. The torsional vibration responses to harmonic excitations are systematically examined under both speed-up and steady-state operating conditions. The resonance mechanism between harmonic excitations and the natural modes of the gear meshing system is revealed, and the influence of speed and load variations on the modulation sidebands of electromechanical coupling is clarified. Mechatronic torsional vibration experiments were conducted on an electric drive system test bench. In the current spectrum, modulated sidebands separated by the gear meshing frequencies were observed. The angular velocity spectrum of the output shaft exhibited the gear meshing frequencies f m1 , f m2 , and 3 f m2 , as well as the electromagnetic excitation frequencies 4 f e and 6 f e . Simulation and experimental results demonstrate a high degree of agreement in characteristic frequency values, thereby validating the theoretical analysis of electromechanical coupling torsional vibration characteristics under harmonic excitation.