A multi-interaction electromechanical coupling dynamic model and lateral-torsional vibration mechanism of the propulsion shaft system

The usage of an electrical propulsion energy system brings not only a wide speed range and large diving depth to the underwater vehicle but also the new electromechanical features of the PSS (Propulsion Shaft System). Revelation of the electromechanical coupling mechanisms and vibration characteristics is the key to the vibration suppression of PSS. This work presents a reinforced electromechanical dynamic modeling method of the PSS. The inductances and permanent magnet flux linkage functions of the IPMSM (Interior Permanent Magnet Synchronous Motor) based on the MWFA (Modified Winding Function Approach) are derived and introduced into the coupling model to consider the effects of the mechanical vibration on the electric system and the IPMSM of PSS. The electromechanical model fully considers the effects of the non-ideal currents with time harmonics, time-varying inductances and flux linkage with spatial harmonics, fluctuated electromagnetic torque, and UMP (Unbalanced Magnetic Pull). Based on the model, the characteristics of the electromagnetic excitations are studied. The time waveforms and spectra of the rotor angular velocities and lateral accelerations are compared to study the coupling mechanisms of the lateral and torsional vibrations. The results indicate that the UMP strengthens the coupling effects between the lateral and torsional vibrations and new harmonics are emerged on spectra due to the electromechanical coupling.