Model-based Condition Monitoring of Anti-lock Braking Systems

The Anti-lock Braking System (ABS) is one of the most important safety features in modern vehicles. It is a device integrating complicated electronic systems, hydraulic systems and mechanical components. It is possible to produce faults in these systems due to extreme vehicle operating conditions, which may lead to the failure of the ABS. However, there has not been an effective mechanism available in current operation and service facilities, which allows the performance of the ABS to be checked on-board or at a service base.

This research therefore aims to investigate and develop approaches which allow the ABS systems to be monitored in different ways. As the ABS is a highly integrated system, conventional monitoring methods cannot be applied to it directly. The primary objective of this research is to develop a condition monitoring model for a typical ABS system under different conditions and then to monitor the dynamic characteristics and performance of the ABS according to simulation and experimental results. The Rapid Control Prototype (RCP) technique is used by applying dSpace MicroAutoBoxII on the ABS controller. A full mathematical model has been developed to simulate the ABS system under different conditions and seeded fault conditions. This results in a full understanding of the characteristics of measurable variables such as wheel velocity and vehicle velocity. This work has led to the conclusion that a model-based condition monitoring approach is the method with the most potential for the monitoring of the ABS systems.

To overcome inevitable measurement noise and model uncertainties, a Kalman filter (KF) has been designed and evaluated through both simulation data and experimental results. This has been found to have acceptable performance and has subsequently been incorporated into the model-based condition monitoring system.

The performance of the model-based condition monitoring system has been evaluated using an ABS test system. The ABS test rig consists of the basic ABS components and also the dSpace MicroAutoBoxII components, together with NI data acquisition equipment. The ABS test rig developed in this research is highly flexible to allow experimental investigations under different fault conditions with different severities. It has demonstrated that the monitoring system can reliably detect different possible faults in the ABS such as speed sensor failure, solenoid valve sticking or stuck, hydraulic fluid leakage and pump efficiency loss. All these faults occur with high possibility according to a systematic failure mode analysis based on that of similar components.

Obviously, there is still considerable work which needs to be carried out to adopt this system in industry. For example, interfaces to integrate this new system into existing vehicle electronics should be investigated. In addition, specific fault conditions from different vehicle manufacturers should be simulated to tailor the system to specific vehicles specifically.