Robust LPV control for vehicle steerability and lateral stability

This paper presents an integrated control of the steering and braking subsystems to improve vehicle handling and directional stability. During normal driving situations (from low to mid-range lateral acceleration), the proposed controller serves as steerability (driveability) controller involving only active front steering. The control objective in this driving zone is to enhance the vehicle steering response by tracking a reference yaw rate. However, when the vehicle reaches the handling limits, the developed controller is used as a stability controller collaborating both active front steering and rear braking. The primary objective becomes to stabilize the vehicle while reducing the vehicle sideslip motion. The proposed MIMO controller, called VDMC (Vehicle Dynamics Management and Control), is synthesized within the gain scheduled LPV framework allowing the selection of the variable to be controlled (yaw rate/sideslip angle) and the coordination of steering/braking actuators according to the vehicle driving conditions. VDMC is built by the solution of an LMI problem, while warranting H_∞ robust performances. Simulation results carried out on a full nonlinear vehicle model confirm the effectiveness of the developed control system and the overall improvements in vehicle handling and directional stability.