| In recent years,electric automobile have become the better choice for many people with the support of national policies.Electric automobile have two driving types: the centralized system and the distributed system.Due to the advantages of simple structure,flexible driving and high transmission efficiency,distributed hub structures have been considered as a better choice for low-speed electric automobile driving system.By sorting out the domestic and international development history and research status of hub motors,this paper analyzed the structural characteristics and electromagnetic characteristics which affected driving stability.The harmonic analysis on electromagnetic torque indicated that the main components of the harmonic torque are low-order harmonics.In order to effectively minimize the torque ripple,a hub motor structure with an additional three-phase independent winding was designed.A method of compensating current injection based on current amplitude iteration was proposed.By use of dynamic step dichotomy,the fast convergence of expected compensation current amplitude was realized.The mathematical relationship between the compensation current and the electromagnetic torque generated by the compensation winding was derived to confirm the parameters such as frequency,amplitude and phase.The simulation research was carried out on the flux-Matlab joint simulation model.An experimental platform was set up to verify the experimental result of the control strategy under complex application scenarios.Simulation results show that the compensation current injection method,which is parameterized by current amplitude iteration,is effective in suppressing the torque harmonics of specific order.The experimental results show that the ratio of the harmonic components to the total torque is high,and the harmonic components of the torque are complex and the main components of the harmonic torque are low-order harmonics.The research results show that the method mentioned above reduces the total harmonic distortion by 2.80% to 5.84%,which proves that the method has good effect and the research results propose a design guideline for practical application. |
