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Thermal design is critical to the performance and reliability of electric vehicle’s traction motor which may suffer from issues such as de-magnetization of permanent magnets and aging of insulation layer of copper winding wires at high temperature. In this work, CFD simulation was first conducted using ANSYS FLUENT to study the heat transfer and fluid flow inside the stator-rotor air gap and the end space of an electric traction motor used in a production vehicle (GAC’s pure electric GE3 SUV). To study the effect of air gap thickness, analytical results based on thermo-fluid theory were also computed and compared to CFD results. We then conducted lumped-parameter thermal network (LPTN) simulation of the traction motor. The model consists of 74 nodes, in which each stator end winding was modeled as three-layer structure to capture the inner temperature gradient.

An analytical tire model of freely-rolling properties is established by using experimental modal parameters. Based on force balance, rolling kinetics and road constrain conditions, the algorithms concerning deformation and force distribution within contact patch are derived, and structural damping is introduced in order to calculate rolling resistance under quasi-static state ( approximate to zero speed ). The derived model can describe the change process of vertical load and friction force distributions from static state to rolling state. Rolling resistance, effective rolling radius, slip ratio, and vertical stiffness of a freely-rolling tire are also calculated. The results are well consistent with literature. The rolling mechanism of tires is revealed and it is the basis for modeling of enveloping and cornering properties. The feasibility and advantages of tire modeling by using experimental modal parameters are reflected.

Based on the modeling of tire vertical characteristics and steady state cornering properties, the model of tire nonsteady cornering is established in this paper using the tire modal parameters extracted experimentally. The dynamic deformation of tire footprint and the influence of tire width for self-aligning torque are taken into account. The footprint is segmented and the influence of speed on non-steady characteristics is included. The analytical formulae for calculation of transfer-function of lateral force and self-aligning torque with respect to lateral displacement and yaw angle are derived. The non-steady characteristics of tire under different loads can be calculated. The calculated results are consistent with the experimental results in the literature. This shows that the tire nonsteady model can be established conveniently using experimental modal parameters. The dynamic characteristics of tires under different working conditions can be calculated directly.