Using nonlinear energy sink to suppress the torsional vibration of electromechanical coupling transmission system

The permanent magnet synchronous motor (PMSM) has been widely used in the new energy electric vehicle, due to its reliable structure, high efficiency and high torque density, the PMSM driven transmission system is a electromechanical coupling transmission system (ECTS), which could occur torsional vibration in the PMSM startup, braking and other transient conditions. Here, a novel nonlinear energy sink (NES) based on the elastic connected disc mechanism is proposed and applied in the PMSM driven transmission system to attenuate the torsional vibration. The dynamic model of the ECTS coupled with NES is established, which considers the electromagnetic excitation nonlinearity and NES nonlinear characteristic. The dynamic performance of the ECTS coupled with NES under harmonic excitation, shock excitation and random excitation are studied, and evaluated by the torsional angle of transmission system and the relative torsional angle between the PMSM and transmission system, also compared with those of the original ECTS and ECTS coupled with traditional dynamic vibration absorber (DVA). The effects of PMSM and NES structural parameters on the dynamic performance of the ECTS are studied, and the NES structural parameters are further optimized using the genetic algorithm. The results show that compared with the original ECTS and ECTS coupled with DVA, applying the NES in the ECTS can reduce the torsional angle peak amplitude and widen the stable frequency region when the system is under harmonic excitation, can decrease the torsional angle amplitude and reduce the vibration attenuation time when the system is under shock excitation, can reduce the root mean square (RMS) value of the relative torsional angle between the PMSM and transmission system when the system is under random excitation. The dynamic performance of the ECTS coupled with NES can be improved by selecting larger internal power factor angle, larger ampere-turn, larger pole pair and smaller saturation ratio of the PMSM. In addition, the torsional vibration suppression performance of the NES can be enhanced by choosing larger rotational inertia and appropriate damping, the effect of the stiffness of the spring inside the NES is limited. Therefore, the proposed NES is a novel mechanism and can improve the dynamic performance of the ECTS effectively.