Linear assistance filter design for electric power steering systems with improved delay margin

This paper studies the achievable delay margin using lead-lag filter structures for Electric Power Steering systems. We propose an approximation of the delay margin as an explicit function of filter parameters. Our results provide useful guidelines for adjusting the different filter parameters to ensure system stability in the presence of a time delay. Simulation results show that the proposed filter structures can attenuate vibrations and improve steering feel and road feel. As a consequence, the influence of the delay on the system can be minimised with little performance degradation.