Chen, B., Hsu, W., and Huang, S., "Sliding-Mode Return Control of Electric Power Steering," SAE Technical Paper 2008-01-0499, 2008, doi:10.4271/2008-01-0499.
Steering wheel might not be able to return to the center position due to friction torque in the steering mechanism. A return control strategy for the electric power steering using sliding mode approach is proposed in this paper. The sliding mode controller (SMC) is designed based on the rotational dynamics of the steering column. The uncertainties of the system parameters and friction torque are included in the control discontinuity. A trigger rule is also proposed to switch between assist and return controls. Preliminary simulation results show that the proposed algorithm can not only improve the returnability, but also provide the damping compensation.