Zizhen Qiu

In-wheel motor (IWM) is a key trend in distributed drive electric vehicle powertrains. The increased unsprung mass, road surface, vehicle axle loads and unbalanced electromagnetic force (UEF) coupling induces IWM eccentricity. But it has not been verified by road tests, and eccentricity mechanism under road is unclear. In this research, both bench and road tests are designed, publicly reporting existence of IWM eccentricity under road. And multi-dimension eccentricity electromechanical coupling model (MDEEC) is proposed considering detailed IWM structural features. It consists of vertical dynamics model considering axial deflection (VDMAD) and UEF model with multi-dimension eccentricity (MDE). Through the study, mechanism of IWM eccentricity under road conditions is explained, which is caused by static MDE by vehicle axle loads and MDE fluctuations by np (n=1,2,3…, p represents the number of the pole pairs) order UEF. Besides, coupling between axial and vertical displacement is nonnegligible. Based on the results of MDEEC and the validation of tests, above factors lead to radial and axial deflection of 0.107 mm and 4.05×10^-4 rad, which means eccentricity over 10% and leads to vibration deterioration. This research provides theoretical guidance for dynamics analysis and design of the IWM.

This article proposes a new adaptive gain, full-order terminal sliding mode control algorithm for the speed regulation of a surface-mounted permanent magnet synchronous motor (SPMSM) control system. To deal with the mismatched uncertainties in the double-loop nonlinear system of the SPMSMs, a virtual control technique is constructed with the full-order terminal sliding mode control to ensure that the tracking error trajectory can converge to equilibrium in finite time. Owing to the integral control law, the output signals of the controllers are smoothed, with the chattering phenomenon attenuated and the gain-margin overestimation avoided. Comprehensive simulation and experimental results have been carried out to demonstrate the superiority of the proposed method in improving tracking accuracy, rapidness, and robustness to the matched and mismatched uncertainties.

In the research on electric vehicle transmission vibration characteristics, the dynamic model involving a multistage gear system is still rare, especially the influences of driving motor excitation and load excitation which are not considered, and which makes the gear system research deviate from the actual situation. In addition, the changing processes of variables are usually simplified or neglected in the study of gear systems, which is not conducive in revealing the mechanism of gear dynamic behavior. In this paper, an improved dynamic model of a motor-gear system is established. The influences of driving motor excitation and load excitation are included, and the changing processes of tangential, axial, and torsional vibration variables of driving gear and driven gear are obtained using the state space method. Furthermore, the transmission housing vibration responses are investigated. By comparing the simulation results with the measurement data, the improved dynamic model, as well as the state space solution method, are verified as reliable and universal. On this basis, the influence of motor excitation on the state change of the gear system is discussed, which provides a theoretical approach for further study of motor drive gear systems.