Fuzzy-proportional Controller of EPS for Autonomous Driving of Small Electric Vehicles

Besides providing assisting torque to the driver, electric power steering (EPS) can also be used as a component of the steering system for autonomous vehicles. Using steer-by-wire (SbW) systems, the EPS dynamic mostly has a second-order one degree of freedom (DOF). This paper proposes a fuzzy-proportional controller of EPS for the autonomous driving of a small electric vehicle (EV) with the EPS dynamic having a fourth-order two DOF. First, a dual-mode EPS dynamic model is adopted, and its parameters’ values are identified through frequency response experiments. Then, a fuzzy-proportional controller is designed, and its performance is compared with that of the conventional PID controller. From the simulation results of step and chirp signal responses, the EPS system with the fuzzy-proportional controller has better tracking ability than the conventional PID controller. The system with the fuzzy-proportional controller has a smaller overshoot of 1.1% and a faster rise time of 0.139 s than the PID controller, as seen in the step response.