This paper presents a parameter estimation, robust controller design and performance analysis for an electric power steering (EPS) system. The parametrical analysis includes the EPS parameters and disturbances, such as the assist motor parameters, sensor-measurement noise, and random road factors, allowing the EPS stability to be extensively investigated. Based on the loop-shaping technique, the system controller is designed to increase the EPS stability and performance. The loop-shaping procedure is proposed to minimize the influence of system disturbances on the system outputs. The simplified refined instrumental variable (SRIV) algorithm, least squares state variable filter (LSSVF) algorithm and instrumental variable state variable filter (IVSVF) algorithm are applied to reduce the model mismatching between the theoretical EPS models and the real EPS model, as the EPS parameters can be accurately identified based on the experimental EPS data. The performance of the proposed method is thus compared to that of the proportional-integral-derivative (PID) test bench results for the EPS system. The experimental results demonstrated that the proposed loop-shaping controller provides good tracking performance while ensuring the stability of the EPS system.

Nowadays, the Kalman filter is being extensively studied in power system modeling and analysis because of its advantages such as high frequency noise filtering effect, multifold fast and accurate performance, etc. In this paper, therefore, the authors proposed a signal processing method using Kalman filter to process voltage and current signals in the modeling of distance protection relay. Then an application for Vietnam's 500 kV power transmission lines was simulated using Matlab/Simulink software. The simulation results showed that the proposed method had high accuracy. In addition, the relay could exactly work and increase the sensitivity and reliability of the power system.