Colloquia

Summary

For the purpose of increasing the energy efficiency of electric vehicles, vehicle manufactures are experimenting with in-wheel motors. By placing the electric motor in the wheel the requirement for drive line components is removed, as well as the efficiency losses that accompany those drive line components. However, the placement of the electric motor in the wheel greatly increases the unsprung mass of the vehicle. Increasing the unsprung mass negatively affects the comfort and road holding performance of the vehicle. 

In this work simulations are done to investigate if active suspension can decrease the negative effects of the unsprung mass. For this investigation a quarter car model is used to simulate a midsize electric vehicle driving over a smooth road with a standardized bump. The parameters of the quarter car are not certain since they are affected by environmental influences, component wear, manufacturing tolerances and daily routine. To model uncertainties the probability theory is employed such that uncertain parameters are modeled as random variables described by appropriate distributions. To quantify uncertainty in the response, the  polynomial chaos expansion is adopted.  A proportional integral controller is used to control the active suspension and optimized by taking uncertainties into account. The comfort and road holding performance of four vehicle configurations are compared using a performance score system.

The results show that the active suspension significantly outperforms the passive suspension in dealing with the negative effects of the in-wheel motors mass. Additionally, the vehicle configuration with active suspension and the in wheel motor also outperformed the configuration with passive suspension without the in wheel motor.