There are many advantages to an in-wheel motor drive (IWMD) vehicle. However, installing the motor in the wheel will increase the unsprung mass and deteriorate the vehicle ride comfort. In this paper, this conclusion is verified by a comparative simulation test of ride comfort. To solve the above problems, this paper puts forward a new in-wheel motor drive (NIWMD) model and comprehensively evaluates the vertical performance of the vehicle from two aspects: vehicle ride comfort and motor vibration. The vertical performance evaluation indexes include body acceleration, wheel dynamic load, suspension dynamic deflection, motor acceleration, and motor relative displacement. The vertical performance of the NIWMD model, CMD model, and IWMD model is compared. The results show that, especially in the high-frequency resonance region, the NIWMD model can effectively suppress the peak vibration response and improve the vehicle vertical performance. The influence of system parameters of the NIWMD model is studied, and the sensitivity of system parameters is calculated. The research results show the parameters that have a great influence on the vehicle vertical performance, which points out the direction for the optimization of the vertical performance of the NIWMD model.

Compared with other electric vehicles, the ride comfort of the electric vehicle with the in-wheel motor as a dynamic vibration absorber has significantly improved. However, the in-wheel motor is used as a dynamic vibration absorber, aggravating the motor vibration, thus affecting motor performance and life. In addition, the space inside the wheel is limited, so the vibration displacement of the motor relative to the hub needs to be constrained. In fact, the literature on ride comfort of the electric vehicle with the in-wheel motor as a dynamic vibration absorber has hardly considered motor vibration. So, this article comprehensively investigates the ride comfort and motor vibration of this electric vehicle. Firstly, the vibration model of the electric vehicle with the in-wheel motor as a dynamic vibration absorber is established. Then, the optimisation model of this electric vehicle is founded. Next, the multi-objective particle swarm optimisation algorithms based on adaptive grid and crowding distance are used to optimise the model, and these two algorithms are compared. The optimal solutions in three typical cases are obtained. Finally, the vibration responses of this electric vehicle model before and after optimisation, the traditional electric vehicle model, and the in-wheel motor drive electric vehicle model are compared in case 1. The results show that all vibration responses are improved to different degrees after optimisation; the algorithm based on crowding distance can seek out the optimal solutions faster, but it takes longer to complete the whole optimisation process.

To resolve the problems of adding unsprung mass and worsening ride comfort of hub motor drive electric vehicles, a new drive system with hub motor as dynamic absorber is studied and proposed. The mathematical models of the new hub motor drive system and the centralized motor drive system are established, and their ride comfort is compared and analyzed. The impact of dynamic absorber parameters on ride comfort of the new hub motor drive system is analyzed, and the parameter sensitivity is calculated. The results show that the body acceleration, suspension dynamic deflection, wheel dynamic load of the new hub motor drive system are better than those of the centralized motor drive system, and the dynamic absorber parameters have a great effect on the electric vehicle performance.