Model development and control methodology of a new electric power steering system

In this study, a new column-type electric power steering (EPS-TT) system is investigated. The remarkable features of this EPS-TT system are its opto-isolated torque sensor, which is used to make steering torque measurements, and its assist torque control methodology, which uses a unidirectional motor and two clutches. Thus it does not require a complicated motor drive system that consumes a large amount of electrical energy when the direction of rotation is reversed. This allows the new system to use a smaller and simpler assist motor. A full steering system model and a simplified model are developed to evaluate the EPS-TT system. A full car model is also used to investigate the vehicle response. A map-based control method and a proportional-integral-derivative control algorithm are designed to control the EPS-TT system. Various sinusoidal inputs are applied to the system and the resulting performance is analysed. The results show that the performance achieved by the EPS-TT system is similar to that of a conventional EPS system across the frequency domain. The results for the full steering system model are similar to those for the simplified model, but the vehicle response is slightly different. The map-based controller provided good performance without affecting the stability or controllability of the vehicle.