Comparison of the Braking Performance of Electromechanical and Hydraulic ABS Systems

Abstract

The benefits potentially available by replacing conventional hydraulic ABS brake systems with electromechanical brake-by-wire systems (EMB) are extensive and have been well documented. They include increased functionality, packaging and design flexibility, reduced assembly costs, and elimination of hydraulic fluids [1, 2]. A characteristic of most ABS systems is a sequence of discontinuous build-hold-dump pressure cycles, whereas EMB systems will allow continuous control of brake torque. In this paper, the antilock performance of an EMB using a continuous brake torque control strategy is compared against that of a current state-of-the-art hydraulic ABS system. The comparison was performed using a half-car model developed in the Simulink environment. The hydraulic system characteristics were identified from ABS test data on a recent production vehicle and the simulated ABS logic was also validated using this data. A simple model of the dynamics of an EMB actuator with clamp force control was developed, and validated against limited test results from a prototype EMB system. A continuous gain-scheduled PID wheel slip controller was developed for the EMB to replace the conventional ABS logic. Brake system performances were compared using an Antilock Performance Index (API). The results of the comparison indicate that an EMB with continuous slip control has the potential to perform better than a conventional ABS system, provided a suitably robust wheel slip controller and algorithm for determining the appropriate target slip are available.

Tyre curve estimation in slip-controlled braking

“…As a result, the ABS cycle at frequencies of 1–2 Hz in HGVs, leading to substantial reductions in the braking force due to the periodic locking and unlocking of the wheel (by comparison, the ABS of passenger cars cycle at frequencies of 6–8 Hz). 6,7 It has been shown by Miller et al 8 and Miller and Cebon 9 that actuation delays in heavy vehicles can be reduced by an order of magnitude (from over 40 ms to under 4 ms) by placing fast pneumatic valves featuring ‘binary-actuation’ technology directly on brake chambers, instead of conventional valves located on a central controller (i.e. an electronic control unit (ECU)).…”

Modelling and Validation of An Electronic Wedge Brake System with Realistic Quarter Car Model for Anti-Lock Braking System Design

“…Continental company invented an EMB brake in 1995 which was tested in vehicles in 1997 [4]. Companies like Bosch, Siemens, Continental TEVES and other companies also presented their EMB ideas [5]. Continental, Siemens and BREMBO collaborated for development of fourth generation of EMB [6].…”