A novel application of the adaptive fuzzy sliding-mode control (AFSMC) to the case of an antilock braking system (ABS) is proposed in this paper. ABS is a system in vehicles that allows the wheels to maintain tractive contact with the road and avoid uncontrolled skidding. By using ABS, the stopping distances on dry and slippery surfaces are expected to decrease. The maximum braking force is a nonlinear function of the slip ratios of the wheels, which is sensitive to the vehicle weight and road condition. In this research, a simple low-order model of the braking dynamics is considered and unmodeled dynamics are taken as uncertainties. The robust AFSMC method is used to regulate the wheel slip ratio toward the desired value. The proposed controller employs pulse width modulation (PWM) to generate the braking torque. There is no need to use any reference measured data or experimental knowledge of relevant experts to design the controller. A clear advantage is that the designed controller does not rely on the nonlinear tire–road friction model. The second Lyapunov theorem is employed to prove the closed-loop asymptotic stability. In the simulations, the multibody dynamics method is used for modeling the longitudinal motion of SAIPA X100 and X200 vehicle platforms. Furthermore, the actuation and the switching dynamics of the braking system are taken into account. Resulting performance is compared to the conventional sliding-mode and feedback linearization methods. Analysis of the simulation results reveals the effectiveness of proposed AFSMC method.

Wheel Slide Protection Devices (WSPD) are employed in railway vehicles to maximize the average of the possible frictional braking force, which is a nonlinear function of the slip ratio of the wheel sets. In this paper, to control the WSPD, a low-order model is presented and un-modeled dynamics are considered as uncertainties. Due to the nonlinear dynamics of the system and presence of uncertainties, Adaptive Fuzzy Sliding-Mode Control (AFSMC) is employed to regulate the slip ratio towards the desired value. The proposed controller employs a Pulse Width Modulation (PWM) technique to generate the braking torque. The second Lyapunov theorem is used to prove the closed-loop asymptotic stability. In the simulations, the switching dynamics of WSPD is considered and the multi-body dynamics method is used for modeling the longitudinal dynamics of ER24PC locomotive. The obtained results reveal that by using the AFSMC method, the slip ratios of wheel sets converge to the reference values. Unlike the conventional method, in which the fluctuations of slip ratio diverge near the stopping time, simulation studies reveal that with the AFSMC method, the stopping time of the locomotive and the fluctuation amplitude of the slip ratios are reduced.