Improvement of traction performance and off-road mobility for a vehicle with four individual electric motors: Driving over icy road

•A traction control system for electric vehicle with in-wheel motors is introduced.•SMC and PID control are efficient for wheel slip control in traction mode.•An extremum-seeking algorithm is developed for robust estimation of reference slip.•The traction control reduces acceleration time for icy surface conditions.•Traction and speed control ensure near-constant low velocity tracking.

To control speed and wheel slip for severe conditions of tire-surface interaction is a challenging task in the design of traction control system for electric vehicles with off-road capability. In this regard, the present paper focuses on a specific traction control for an electric vehicle with four individual in-wheel motors over icy road. The study demonstrates that a proper integration of the speed controller and wheel slip controller can essentially improve the mobility of the vehicle in the cases of acceleration and slope climbing. The paper discusses relevant case studies with particular attention given to the system architecture (sliding mode and PID control methods), extremum-seeking algorithm for maximum tire-road friction and corresponding slip value, and experimental validation of the tire model used in the controller with the help of the Terramechanics Rig in the Advanced Vehicle Dynamics Laboratory (AVDL) at Virginia Polytechnic Institute and State University.

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