Proposal of Active Sensing Wheel Based Optimal Slip Ratio Estimation for In-Wheel Motor Vehicles

This paper proposes a method for online estimation of optimal slip ratio, thereby enhancing the conventional Driving Force Control (DFC) system in which the slip ratio limiter is commonly fixed at a predefined value. Especially, in the scenario of an in-wheel motor electric vehicle operating on a uniform road surface, the road condition can be sequentially estimated by assigning one wheel as an Active Sensing Wheel (ASW) and the others as a Passive Limiter Wheel (PLW). The ASW continuously seeks the slip ratio peak, which is utilized to update the slip ratio limiter that connects the outer- and inner-loops of PLW’s DFC. Real-time experiments show that the peak of slip ratio was successfully estimated using ASW. The estimated peak is also utilized to update the slip ratio limiter in the DFC of PLW, thereby enabling adaptive control by the road condition. Notably, the total driving force of the vehicle was increased by 8 % in the proposed method compared to the conventional method with fixed slip ratio limiter. Furthermore, the driving force generated by the PLW alone was improved by approximately 46 %, indicating that the proposed method enhances the traction performance of not only the PLW but also the total system.