Research on the dynamics of a permanent magnet direct-drive bogie with consideration of electromechanical coupling

A vehicle–motor coupled dynamic model for a permanent magnet direct-drive (PMDD) axlebox-built-in bogie operating at 120-200 km/h is developed in this study. The model integrates a multibody vehicle system and a PMSM traction system under an SVPWM vector-control strategy to investigate electromechanical coupling effects. The influence of current-loop and speed-loop control parameters on motor output characteristics and vibration transmission is analyzed. Simulation results show that the dominant frequencies of vehicle lateral and vertical vibrations are mainly concentrated in 3-15 Hz, and the vehicle maintains stable dynamic performance during traction. The speed-loop parameters significantly affect the coupled vibration between the motor and the bogie frame and may induce vertical resonance, while the current-loop parameters have minimal impact. Furthermore, the analysis of motor-suspension stiffness indicates that higher stiffness improves high-speed running stability. The proposed model provides guidance for PMDD traction system control optimization and bogie design for 120-200 km/h urban rail trains.