Fuzzy Control for Off-center Steering System of a Novel Electric Chassis Based on PWM Technology

A flexible chassis (FC) for an electric vehicle with four in-wheel drive motors is described in this paper. It has a unique structure with an off-center steering shaft. The driving system and steering system are combined, which has considerable advantages in terms of actuation flexibility for the confined spaces. However, there is no rigid constraint for steering, and it is difficult to coordinate the motions of electromagnetic steering lock (ESL) and the wheel. To solve this problem, a pulse-width modulation (PWM) technology is introduced to control the ESL. With the control of PWM signal, the chassis can achieve stepwise driving and steering. Then, fuzzy logic is introduced to control PWM signal of the ESL so that it can match the steering motion of the wheels. To validate the system, steering signal step input tests and sinusoidal input tests were conducted on a self-made test bench. The results demonstrate that, the off-center steering system is with good steering performance, and the linkage and tracking errors of the left and right wheel are all in an acceptable range. The proposed control strategies are feasible and effective, and can ensure smooth turning for the chassis. (paper)