Estimating SI Engine Efficiencies and Parameters in Second-Order Sliding Modes

Identification and estimation of immeasurable critical parameters/efficiencies of automotive engine provide significant information to monitor its functions and health. This paper proposes a novel estimation scheme for identifying such parameters. Four of the critical parameters discussed are frictional torque, combustion efficiency, volumetric efficiency, and throttle discharge coefficient. These parameters are estimated from a two-state nonlinear inlet manifold pressure and rotational speed dynamics-based engine model. The estimation scheme utilizes a second-order sliding mode observer based on a super twisting algorithm. The estimation is carried out on a production vehicle equipped with an engine control unit compliant to On-Board Diagnostics II standards. The proposed observers are simple enough for implementation. The estimated parameters have vast application in the area of engine modeling, controller design, and fault diagnosis/prognosis.