Road Feel Simulation Method with Rack Force Observer for Intelligent Vehicle Steer-by-Wire System

To provide the driver with a more realistic and comfortable driving experience, a novel road feel torque planning method based on rack force estimation and an active return control method for the steering wheel with disturbance observation are proposed for intelligent vehicle. First, for road feel feedback during steering, an improved reduced order extended state observer is designed to estimate the rack force, a secondary filter filters the rack force, obtaining the alignment torque, and superimposing the assist, inertia, damping, friction, and limiting torques to replicate the road feel of the electric power steering system. Second, a proportional-integral observer is designed to observe the lumped uncertainties in the steering wheel system and introduce the observation value into the backstepping controller for active return control of the steering wheel. Finally, an integral sliding mode controller is designed to control the road feel motor to achieve accurate feedback of road feel torque. The virtual simulation results show that the observation effect of the proposed observer is better, the designed road feel torque meets the requirements better; the proposed active return controller can achieve accurate return of the steering wheel, and the sliding mode controller achieves more accurate tracking of the road feel torque.