The electro-mechanical brake (EMB) system is a novel dry-type brake-by-wire
system that features superior control performance and a compact structural
design, effectively meeting the development demands of intelligent and
electrified vehicles. However, current research on anti-lock braking system
(ABS) primarily focuses on hydraulic brake system and mostly remains at the
simulation and hardware-in-the-loop testing stages. Therefore, this paper
validates the feasibility of slip ratio control based on EMB actuators through
both simulation and real-vehicle experiments. First, this paper establishes an
equivalent second-order response model for the closed-loop EMB control system
through theoretical derivation and identifies the dynamic response
characteristics of the EMB actuator via sinusoidal frequency sweep testing.
Next, it compares two control strategies: one that uses the reference slip ratio
as the direct control target, and another that uses reference wheel speed as the
direct control target to indirectly regulate slip ratio. The latter effectively
avoids the nonlinearities in slip ratio control caused by variations in vehicle
speed. Based on reference wheel speed control, three types of slip ratio
controllers were designed and derived: proportional-integral control (PI),
integral sliding mode control (ISM), and super-twisting integral sliding mode
control (STISM). Finally, simulation and real-vehicle tests on high-adhesion
road surfaces verified that sliding mode slip ratio control based on reference
wheel speed offers robustness, avoids the risks associated with overestimated
controller gains, and improves the overall stability of the control system. In
particular, the STISM, as a representative of high-order sliding mode control,
effectively addresses the chattering issue present in traditional first-order
sliding mode methods, offering enhanced braking safety and comfort.