A half-car vibration model of an electric vehicle driven by rear in-wheel motors was developed using bond graph theory and the modular modeling method. Based on the bond graph model, modal analysis was carried out to study the vibration characteristics of the electric vehicle. To verify the effectiveness of the established model, the results were compared to ones computed on the ground of modal analysis and Newton equations. The comparison shows that the vibration model of the electric vehicle based on bond graph theory not only is able to better compute the natural frequency but also can easily determine the deformation mode, momentum mode, and other isomorphism modes and describe the dynamic characteristics of an electric vehicle driven by in-wheel motors more comprehensively than other modal analysis methods.

For an in-wheel-motor drive electric vehicle, the driving motors are directly mounted in the wheels. Using this chassis structure, the road excitation can cause a magnet gap deformation in the motor. The magnet gap deformation will lead to magnetic force which not only has a negative impact on vehicle dynamics but also affects the magnet gap deformation in turn. To further analyze the impact of the road and the magnetic force on the motor magnet gap, a test platform was built, and used to simulate cases of road and composite excitation. The results show that 1) road excitation can cause motor magnet gap deformation, and when the excitation frequency is increased for a constant amplitude, the deformation degree also increases. 2) For the same road excitation frequency, the deformation degree increases with the motor speed. This not only proves the existence of the magnetic force but also indicates that the size of the magnetic force is related to the motor rotating frequency. 3) A comparison between the simulated and experimental results not only confirms the validity of the theoretical derivation and analysis but also lays the foundation for subsequent vibration control of in-wheel-motor drive electric vehicles.

No abstract

No abstract

As the core component of in-wheel motor-driven electric vehicles, the in-wheel motor (IWM) directly affects the driving/braking performance of each driving wheel and the driving performance of the vehicle. The IWM operation involves a coupling of multi-fields, including the electromagnetic, temperature, flow, and mechanical fields, which influence each other. It is necessary to study coupling analysis methods to obtain accurate and consistent results. In this paper, a 15 kW in-wheel motor is taken as the research object. Based on the finite element model of the IWM, the coupling factors between the electromagnetic and temperature field, and the influence trend of coupling factors on the two fields are investigated. On this basis, considering the strong coupling factors obtained from the above analysis, the unidirectional coupling and bidirectional coupling analysis methods are used to analyze the electromagnetic–temperature characteristics of the IWM, and the comparative results between the two methods are discussed. It was found that the results showed the temperature of the IWM calculated by the bidirectional coupling method was higher than that obtained by the unidirectional coupling analysis method. The maximum temperature of stator windings calculated by bidirectional coupling was 7.1% higher than that calculated by unidirectional coupling analysis, and the effect on the relative difference of torque could reach 7.4%. Bidirectional coupling can more accurately reflect the variation of variables in the fields and the prediction of motor performance in the process of motor operation. The progress made in the electromagnetic–temperature coupled analysis method can provide a theoretical basis and useful ideas for the multi-fields coupling analysis of IWMs.