Diagnostické metody a jejich aplikace v automobilovém průmyslu

Abstract

Gasoline engine is a complex power generating machines and used widely in automotive industry, which the failure rate is high. Carrying out the gasoline engine fault diagnostic methods have been studied and still a lasting topic for scientists. Crankshaft instantaneous angular acceleration contains information for fault diagnostic. It can directly reflect the state of applying work and current pressure in each cylinder. By means of analyzing the angular acceleration signal, the instantaneous engine running state and a lot of related faults can be discovered. Under the normal working conditions, the motive force performance of each cylinder is unanimous basically, the gasoline engine operates steadily. Its angular acceleration always fluctuates in a normal range and presents certain regularity. The operation when a certain cylinder is working abnormally, the consistency of motive force is destroyed, the engine becomes bad to the stationary of operation, and the angular acceleration signal will be out of shape. By observing its fluctuation, the working process in each cylinder can be evaluated. In this thesis, the instantaneous angular acceleration is evaluated by phase modulation method using the Hilbert Transform technique. To verify the signal analysis technique, the engine model created originally by Weeks, RW & Moskwa, J.J. is extended by modeling of the non-uniform driving torque in contrast to the original model assuming uniform driving torque to produce fluctuation of the crankshaft angular acceleration. Many subsystems of the engine are also modeled by the simulation program Matlab/Simulink. Torque of engine at some spark advances was simulated to compare and found out the best angle to obtain the maximum brake torque, as well.