Force Control of In-Wheel-Motored Electric Vehicles

Abstract

Electric vehicles (EVs) are gaining attention, and novel use of cars such as vehicle-to-home is becoming widespread. In particular, in-wheel-motor (IWM) type EVs, which have four motors inside each wheel, are expected to be an ideal power train system because it can achieve precise driving force control and estimation. To exploit these features of IWM-EVs, researchers have proposed numerous control methods, most of which are velocity or position-based control for running or trajectory tracking. Force control technologies are quite popular in robotics divisions, and these methods are quite suitable for the new applications of EVs. By taking advantage of the precise estimation performance of IWM-EVs, the authors have proposed to apply force control to EVs and built the concept of human-friendly EVs as done in the robotics division. We show the external force estimation method using wheel resolvers and propose hand-assisted position adjustment method based on impedance control. The appropriate control structure is discussed for IWM-EVs, and its effectiveness is demonstrated with numerical simulations and experiments. We anticipate this research to generate many control applications suitable for the new application of cars.