Multi-Objective Design Optimization of an Electric Motor Thermal Management System for Autonomous Vehicles 2021-01-0257

The integration of electric motors into ground vehicle propulsion systems requires the effective removal of heat from the motor shell. As the torque demand varies based on operating cycles, the generated heat from the motor windings and stator slots must be rejected to the surroundings to ensure electric machine reliability. In this paper, an electric motor cooling system design will be optimized for a light duty autonomous vehicle. The design variables include the motor cradle volume, the number of heat pipes, the coolant reservoir dimensions, and the heat exchanger size while the cost function represents the system weight, overall size, and performance. The imposed requirements include the required heat transfer per operating cycle (6, 9, 12kW) and vehicle size, component durability requirement, and material selection. The application of a nonlinear optimization package enabled the cooling system design to be optimized. Through numerical studies, a 50% reduced overall mass could be achieved for a 12kW heat generating scenario while the operating conditions are secured. These findings establish a design tool for multiple pathway cooling systems in electric motor propelled vehicles.