Reference Torque Tracking Controller for Electric Power Steering Using a Disturbance Observer With System Identification-Based Parameter Selection

In this paper, an innovative control system architecture is presented for electric power steering (EPS) systems, designed to improve reference torque tracking performance. Conventional EPS systems use boost curves to modify assist torque based on vehicle speed and drive modes. However, these approaches require considerable tuning effort, especially when providing configurable steering feel options. To overcome these limitations, this study proposes a novel EPS control system that incorporates a disturbance observer (DOB) to mitigate the effects of system uncertainties and disturbances. Furthermore, a system identification procedure is used to determine the model parameters that critically influence the DOB performance. This process enables the derivation of refined model parameters and the rejection of disturbances such as friction. Subsequent simulation and vehicle testing demonstrate that the proposed control system maintains stable tracking performance in the driver input frequency range, even under varying road conditions and changes in reference steering torque. As a result, the effectiveness of the proposed system is confirmed through its application to production vehicle EPS controllers, achieving stable performance with minimal calibration effort.