Second order sliding mode observer for estimation of SI engine Volumetric Efficiency & Throttle Discharge Coefficient

Identification and estimation of non-measurable critical parameters of automotive engine provide significant information to monitor its functions and health. This article proposes a novel estimation scheme of identifying such parameters. Two of the critical parameters are: Volumetric Efficiency and Throttle Discharge Coefficient. These parameters are estimated from the single nonlinear equation of engine inlet manifold pressure dynamics. The estimation scheme utilizes second order sliding mode observer based on super twisting algorithm. Mean Value Engine Model is considered to model the inlet manifold behavior. The estimation is carried out on production vehicle equipped with engine control unit compliant to OBD-II standards. The proposed observer is simple enough for implementation. The estimated parameters have vast application in the area of engine controller design and fault diagnosis/prognosis.