ADVANCED DYNAMIC SPARK IGNITION ENGINE MODELLING FOR DIAGNOSTICS AND CONTROL

Abstract

For years, control engineers have used engine models with constant mass moments of inertia to simulate internal combustion engines. These models showed satisfactory results at low–speed operations but deviated from real engine operations at high speed. Also, there are some problems in using the constant inertia models for engine diagnostics because of inaccurate estimates of inertial forces at high speed, and many of the components that degrade or fail in an engine are not modelled with that methodology. In this paper, two approaches are used to formulate more accurate nonlinear engine models; one applies the Newtonian method; the other uses the Lagrangian method to derive the nonlinear governing equations for internal combustion engine kinematics and dynamic forces. Also included is the discussion of the discrepancy between the nonlinear time–varying inertia model and previous constant inertia model in their shaft velocity and acceleration fluctuations, and in the reconstructed cylinder pressure using the Sliding Observer.