Optimal Control Based Torque Distribution for In-Wheel Motor Vehicle

Abstract

In-wheel motor vehicles, characterized by their unique feature of independent torque control on all axles, high energy conversion efficiency, rapid motor response times, and the ability to notably decrease curb weight and streamline overall vehicle architecture, represent a significant area of advancement within the electric vehicle domain. The inherent nature of individual wheel propulsion in in-wheel motor vehicles necessitates a more rigorous torque distribution control strategy throughout the vehicle's drivetrain. This study, with a primary focus on improving vehicle stability management, delves deeply into the mechanics of vehicle instability, deriving the correlation between yaw rate, lateral displacement of the vehicle's center of gravity, and overall handling stability. Based on these findings, a specialized phase plane method for assessing instability was formulated. Utilizing an enhanced version of the dynamic surface sliding mode variable structure control technique, a direct yaw moment controller was designed for the in-wheel motor vehicles, considering the equality constraint posed by longitudinal tire forces, alongside inequality constraints related to torque limitations and road surface frictional conditions. Subsequently, an optimal torque allocator was engineered to distribute the direct yaw moment under these constraints, employing a quadratic programming approach for solving the optimal allocation problem. A comprehensive simulation model was built using MATLAB/Simulink to verify the functionality and benefits of the presented design. Moreover, practical validation was conducted through experimental testing on an in-wheel motor vehicles prototype developed by our research team, thereby affirming the practical feasibility and efficacy of the proposed solution.

Keywords: In-wheel motor vehicle, vehicle dynamics modeling, stability control, optimal control, torque distribution optimization