Improved Rear Wheel Unlocking Function of Electronic Parking Brake System Based on Fuzzy Control Algorithm

A fuzzy logic rolling wheel unlocking algorithm that explicitly incorporates the instantaneous tyre road adhesion coefficient is presented. The controller uses vehicle speed, average deceleration, slip ratio error and its rate of change obtained after online road identification as fuzzy inputs to compute the optimal caliper release time. Hardware in the loop and proving ground tests were conducted at 30 km/h and 50 km/h on six road surfaces (high μ, low μ, jump μ and split μ). Compared with the conventional logic threshold RWU, the proposed scheme reduces vehicle stopping time by 0.88 s to 3.11 s and increases average deceleration by 9.03 % to 45.39 % under various road conditions. In summary, compared with the traditional logic threshold rear wheel unlocking control, the proposed fuzzy control algorithm achieves a lower slip ratio and better braking control under different road conditions.