Research on Transmission Efficiency of the Electric-Drive-Wheel with Temperature Modification Coefficient Method

The Electric Drive Wheel (EDW) with a Planetary Gear Train offers a highly integrated propulsion system for the chassis-by-wire vehicle, which achieves a compact unit within the wheel rim spatial constraints. A key challenge is the significant internal temperature fluctuations during acceleration and braking, which critically impact the EDW transmission efficiency. This paper introduces a novel Temperature Modification Coefficient (TMC) methodology to address the limitation of conventional efficiency models with steady-state thermal equilibrium. By dynamically modifying the lubricant viscosity within the elastohydrodynamic lubrication power loss model, the instantaneous EDW transmission efficiency can be computed theoretically. The TMC model’s accuracy was confirmed on a test bench, with a maximal error below 0.82% across 49 operating points in the given test environment. When the EDWs are equipped on a test vehicle for chassis dynamometer NEDC driving cycles, the TMC model successfully decoupled the temperature-dependent efficiency losses in the test data, providing valuable data support for the EDW development and applications in passenger cars.