Parameter Identification, Estimation, and Dynamometer Valida tion of the Nonlinear Dynamics of an Automotive Spark-Ignition Engine

Abstract

The identification is described of a nonlinear mathematical model of a modem four-cylinder four- stroke spark-ignition automotive engine for idle-speed control applications. The primary outputs are engine speed and inlet-manifold pressure, and the primary inputs are mass air/fuel ratio, spark timing, air bleed valve duty cycle, and disturbance torque. The model can be used for simulating and predicting the dynamic response of the engine system for control algorithm development as a tool to evaluate various engine control concepts. The nonlinear mathematical engine model is obtained using an assumed nonlinear model structure, and a sequential least squares identification algorithm is used to estimate the model parameters. The model formulation, which is based on nonlinear continuous differential equations, consists of four state variables with 15 parameters to represent the engine dynamics. The model contains representations of the idle air bypass valve, manifold plenum, engine-pumping phenomena, brake output torque, and rotational dynamics. The model structure and identified parameter set are validated using experimental data from an engine in an electric dynamometer. The results indicate the suitability of the model structure and nonlinear identification technique for general engine idle-speed control model applications in both off-line and on-line implementations.