Fault detection and diagnosis of automobiles without obd systems

Abstract

Early fault diagnosis for automobile engines is very important to ensure reliable operation of the engine. Most of e faults in an automobile engine cannot be detected externally. Detecting faults and its’ location, without dismantling the engme is very difficult. On-board diagnostic (OBD) systems in modem vehicles can be used to detect engine faults up to some extent.'However, OBD systems are not accurate enough in certain conditions and technicians having difficulties when interpretation of information. OBD method cannot be used for old vehicles. Hence, these factors necessitate the development of intelligent and accurate diagnosis method for troubleshooting automobile engine faults. Therefore, a mathematical model is developed to identify engine faults through the simulation of Instantaneous Angular Speed Fluctuation (IASF) of crank shaft. Three force components created by gas pressure, inertia of the moving parts and friction of the moving parts are used to generate the mathematical model. The parameters of the model are modified according to the potential faulty condition and IASF waveform is recorded and compared in different fault scenarios. Type of the fault and the severity of the fault are identified through the comparison. Experiments are conducted using a healthy automobile engine to validate the simulation results. The characteristic parameters for representing potential faults in an automobile engine and their relationship with IASF of the crank shaft are obtained for fault diagnosing. Furthermore a graphical user interface is developed to analyse instantaneous angular speed waveform which can be used as a real time engine condition monitoring system.