Engine Diagnostics by Dynamic Shaft Measurement: A Progress Report

Abstract

<div class="htmlview paragraph">The feasibility of relating crankshaft free end torsional signals to the misfiring of an individual cylinder has been established in earlier torsional simulation work [<span class="xref">1</span>]. This paper advances two diagnostic methods for detection of the IMEP level of individual cylinders.</div> <div class="htmlview paragraph">The first method is an enhanced pattern recognition method using both the flywheel torque fluctuation as the primary signal; and the model based reciprocating inertia knowledge for gas pressure torque harmonics determination. The enhanced pattern recognition method ensures IMEP level detection for each individual cylinder.</div> <div class="htmlview paragraph">The second method i s based on a reverse simulation algorithm. The dynamic flywheel speed fluctuation is used as the input signal to reconstruct cylinder pressure diagrams for each cylinder.</div> <div class="htmlview paragraph">In both methods, a rigorous, multi-mass, lumped mass, elastic crankshaft model is used to depict the mass-elasticity damping system.</div> <div class="htmlview paragraph">In the torsional vibration simulation mode, individual cylinder gas pressure and engine RPM are the two operating inputs. Flywheel torque fluctuation and flywheel speed fluctuation are the outputs.</div> <div class="htmlview paragraph">In the reverse simulation mode, the flywheel speed fluctuation is the input for reconstruction of the individual cylinder pressure. A normalized heat release rate map is used to bridge the gas pressure torque harmonics and the individual cylinder pressure harmonics.</div> <div class="htmlview paragraph">This paper reports the progress made on the analysis of the enhanced pattern recognition method and on the reverse simulation algorithm using a rigorous multi mass, multi cylinder engine model. Analysis shows that the reverse simulation algorithm is most promising for on-board firing diagnostics and cylinder pressure reconstruction.</div>