Model-based engine diagnostics and controls utilizing crankshaft speed measurements

A modified sliding mode observer for Compression Ignition engine diagnostics and cylinder pressure reconstruction based on crankshaft speed variation is presented in this thesis. By redesigning the sliding mode observer gain as a crank angle dependent function, the singularity problem near piston Top Dead Center can be avoided. This modified model-based sliding mode observer was validated by testing a Cummins 6-cylinder diesel engine and showed a good correlation. The modified method is suitable for engine diagnostics in a wide speed range and transient operating conditions with a relatively stiff crankshaft.; An alternative method is presented in this research to consider crankshaft torsional vibration. A torsional signal from either the crankshaft free-end and/or from the engine flywheel can be used as the input. This Reversed Torsional Simulation approach takes the engine combustion model, crankshaft torsional model and the crank-slider reciprocating model into consideration. Therefore, it can be applied to engine diagnostics for multi-cylinder engines with non-negligible torsional vibration. The predicted engine Indicated Mean Effective Pressure and the cylinder pressure agree well with the experiment data under both normal firing and misfiring conditions. A Caterpillar 3612 engine was used for model validation. As this RTS approach is derived in the frequency domain, it is more suitable for the quasi steady-state operating conditions that can be found in most marine and generator applications.; Besides these diagnostic approaches for CI engines, the mean value models are used for Spark Ignition engine dynamic simulation and regulating study. Both the engine production torque and its mechanical governor system were modeled and calibrated by experiments. These models are linearized locally for control stability study. By investigating the closed-loop transfer function, an analytical solution is obtained for engine stability study. The interaction between engine performance and governor design can be investigated using parametric study. This analytical solution has been applied to an SI engine and has shown the improvement in engine regulation control.