Abstract: By analyzing the structure and dynamic characteristics of an electrical power steering system (EPS), the mathematical model of a three-degree of freedom is established. In order to overcome the uncertainties of the dynamic behavior of a practical EPS system, adaptive LQG control strategy is adopted. By identifying the model parameters on-line, adaptive LQG control is easy to be carried out. Under several running conditions of the automobile, the simulation of adaptive LQG and LQG control are implemented. The simulation results show that adaptive LQG control scheme is more effective and robustness is better than LQG control scheme. In order to verify simulation results, a test vehicle with an EPS mechanical and control system was experimented. The test results coincide closely with those obtained from simulation, and they exhibit good performance leading to improvement of steering and handling.

Key words: Adaptive control, Electrical power steering, Parameter identification