Combining adaptive neural-fuzzy inference system with field-oriented control strategy for electric power steering system in cars

This article presents complete control architecture for electric power steering systems (EPS). First, the ideal power assist steering characteristics are built based on data obtained from real vehicle testing or dynamic simulation. Second, a formula is developed to calculate road resistance torque based on the structural parameters of the steering system. Third, an EPS dynamic model is established, which closely reflects the operating conditions of the system. Fourth, a dynamic model of the electric power steering motor is built. Fifth, an Adaptive Neural-Fuzzy Inference System (ANFIS) is designed with Field-Oriented Control (FOC) for the EPS controller. Sixth, the entire mathematical model is simulated and evaluated, including the above dynamic models, under three different working scenarios of EPS, considering the impact of random disturbance torque. The simulation results show that the constructed models closely reflect the physical and dynamic laws of the system, and in theory the proposed controller has obvious efficiency and strong adaptability to the effects of disturbance torque. The research results also identify three problems: (1) Due to the elasticity of the links in the steering system, there is a difference between the actual steering wheel rotation angle and the rotation angle calculated according to the steering wheel kinematics. (2) Due to the viscous drag and the influence of dry friction in the steering system, steering power is consumed, and the response delay of the steering system increases. (3) The steering frequency greatly affects the time delay of the system: the higher the frequency, the greater the delay. Therefore, it is proposed that future research should develop an algorithm and design an EPS controller that can: compensate for the difference due to the elasticity of the material; compensate for the delay due to viscous drag and dry friction in the system; and compensate for the delay when changing the steering frequency, especially when turning quickly and sharply.