Two-Time-Scale Redesign for Antilock Braking Systems of Ground Vehicles

An antilock braking system (ABS) is one of the most effective active safety control systems for ground vehicles, since it can keep the rotational wheel from locking and, consequently, guarantee the braking safety and handling stability. There have been a variety of ABS control schemes proposed by many researchers. However, most of the results employ sundry tire-road friction models, the alleged μ - λ curves (μ is the tire-road friction coefficient, while λ is the tire slip ratio, which is mathematically defined as λ = (v - ωr)/v), making the ABS controller extremely complicated for the highly nonlinear characteristics of the μ - λ relationship. Furthermore, the a priori knowledge of road conditions for these ABS controllers restricts their practicability. To circumvent these problems, a two-timescale ABS control scheme is proposed in this paper, without considering the intricate μ - λ relationship, making the a priori knowledge of the road condition no longer a prerequisite; thus, the designed ABS controller is rather simple. In addition, a modified fast-time-scale estimator is involved to estimate the road condition, which is significant in vehicle active dynamics control. The effectiveness of the proposed ABS controller is verified via numerical simulations and CarSim-MATLAB cosimulations.