A New Control Framework of Electric Power Steering System Based on Admittance Control

This brief presents a new control framework of electric power steering (EPS) systems for ground vehicles based on admittance control. An impedance filter is used to define the desired admittance of the system under the torsion bar (T-bar), and a position tracking control loop is used to enforce its apparent admittance. A road feedback path implemented with a road feedback filter provides the driver with awareness of road conditions with selected frequency components and magnitudes. In this new control framework, the base admittance of the system under the T-bar, which determines the base steering feel, can be configured independently from the closed position control loop; such separation of the closed-loop control design and steering feel configuration can potentially reduce the overall system tuning and calibration time. Common EPS characteristics are related to the design parameters of the new control framework. Numerical cosimulations, including an EPS system model and a vehicle model under different road conditions and maneuvers, show that the base steering feel matches the designed steering feel, and the system has good road disturbance rejection. With the road feedback filter, the base steering feel is augmented and the road condition awareness is improved.