Integrated Active Front Steering and Semiactive Rear Differential Control in Rear Wheel Drive Vehicles

Abstract

Many vehicle control systems are based on the yaw rate error to help the driver during oversteer and understeer conditions. The control systems usually operate on brake pressures distributions such as ESP and/or on active front and rear steering control. Recently many papers are focused on the design of integrated global chassis control systems. The main contribution of this paper is to show for a CarSim® small SUV model the stability of a proportional-integral active front steering control from the yaw rate tracking error integrated with an electronically controlled semiactive rear differential from the rear wheel speed measurements; the stability analysis is based on Lyapunov techniques. The integrated controlled system shows increased performances: new stable cornering manoeuvres and increased safety especially in emergency conditions. Several simulations are carried out on a standard CarSim® small SUV model to confirm the analysis and to explore the robustness with respect to unmodelled combined lateral and longitudinal tire forces according to combined slip theory and unmodelled dynamics such pitch and roll. The simulations on CarSim® vehicle show the benefits of using the proposed integrated control with respect to the case in which only active front steering is employed.