Stochastic modeling and prediction of IMEP for closed loop knock control performance assessment

Abstract Knock control systems aim to maximize power output while also protecting the engine from knock-induced damage. The extent to which this goal is achieved is rarely evaluated, both because the random nature of knock events means that the results of any single experiment are not repeatable, and because control loop performance is generally assessed with respect to the resultant spark angle (the manipulated variable), rather than some measure of output performance. In this work, a new stochastic model for the empirical IMEP distribution is developed and fitted to open-loop experimental data. Stochastic methods are then applied to predict both the steady state and transient closed loop distribution of IMEP based on the open-loop model and the control law that is applied. The results are validated against closed loop data gathered from the engine and show good agreement with the data.