Detecting Leakages in the PneumaticSystem of Heavy Vehicles : Modelling Using Simulink

Abstract: In this thesis an algorithm for detecting leakages in the pneumatic system of heavy vehicles is developed. Besides a description of this algorithm, the thesis includes a description of the pneumatic system of heavy vehicles, a review of some basic statistics and change detection analysis, and a description and analysis of some validation tests. Heavy vehicles use compressed air for various applications, including brakes and suspensions. Leakages in the pneumatic system are quite common and results in an increase in fuel usage, since more compressed air has to be produced. This is of course both environmentally and economically damaging. In order to avoid this damage, leakages need to be fixed. The first step is to notice the presence of leakages. The leakage detecting algorithm is based on a statistical deviation analysis. Inputs used are pressure measurements from the different compressed air circuits and some state variables regarding the compressed air users. All this information is communicated aboard on the vehicles’ controller area network (CAN). The algorithm has been validated using real data measurements from test drives, some of them including a vehicle suffering from leakages. The results indicate that the algorithm manages to identify leakages, but also that there are some problems regarding incorrectly interpreting other events as leakages. The results also indicate that the algorithm fail in the ambition to locate the leakages. If this algorithm should be implemented in a real time system to be used aboard, it is suggested that some improvements are made. These improvements mainly concern avoiding false alarms.