Dynamics control of an In-Wheel Electric Vehicle with Steer-by-Wire

Abstract

The new generation of electric vehicles will replace the traditional power-train by on-hub motors. Consequently, it will offer new options and flexibilities in vehicle lateral motion control due to its structural merits. An In-wheel Electric Vehicle (IEV) powered by two independently embedded driven rear wheels, and with Steer-by-Wire is considered here. The present paper deals with the design of a yaw rate model matching controller intended to maintain vehicle steerability and lateral stability. The reference yaw rate is properly designed to enhance maneuverability when the vehicle is moving in the safety region, and to restrain the sideslip dynamics when the vehicle enters the critical driving zone. The difference between the stable and unstable regions is judged in the phase plane defined by the body sideslip angle and its velocity. The proposed MIMO controller, called VSSC (Vehicle Steerability and Stability Control), coordinates active steering and braking/traction wheel torques to achieve the control goals. VSSC is synthesized within the gain scheduled LPV framework based on Hinfinity robust performances. The conditions for designing such a controller are derived in terms of linear matrix inequalities (LMIs) considering the polytopic approach. Simulation results carried out on a full nonlinear IEV model confirm the effectiveness of the developed control system and the overall improvements in vehicle handling and directional stability.