AUTOMOBILE GEARBOX DIAGNOSTICS ON THE BASIS OF THE REFERENCE MODEL

A method of diagnostics of the automobile gearbox wearing out is presented in this paper. The procedure can be automatically realised during driving. To be able to perform such diagnostics the reference model of the vibration signal on the basis of the synchronously averaged signal was created for a new gearbox (in a good technical con­dition). In order to realize the procedure on-board this model must be easily identifiable. A complicated structural model was given up for the simpler model of the abstract vibrations signal. Three ways of modelling were pre­sented: harmonic series, parametric ARMA (Auto Regressive Moving Average) model, and the wavelet model. The current vibration signal is recorded at the determined moment of driving and then compared with the referen­ce model. After each overhaul or exchange of drive system elements the reference model should be identified again. Diagnostics is being done by comparing measures for the reference model and the currently measured - adequately processed - signal. The method was verified in the active experiment performed on the Fiat Punto automobile with a 5-speed gearbox. The described method can constitute the supplementation of on-board auto­mobile system by the mechanical failures of the drive system. This procedure can be broadened by defects of the main gear, differential gear, articulated joints, bearing, engine exhaust valves, and engine head gasket.