On-line statistical combustion phase optimization and control of SI gasoline engines

Abstract

This paper focuses on analysis and control of the ignition timing of spark ignition (SI) engines to maximize fuel efficiency, in which the optimal reference of combustion phase and moving average based control strategy are discussed. To extract the fuel efficiency information from combustion, in-cylinder pressure sensor is available to calculate combustion phase and indicated mean effective pressure (IMEP). Then, employing CA50 as combustion phase indicator, statistical gradient descent method is utilized to seek the CA50 set point that ensures the maximum indicated fuel conversion efficiency (IFCE) and satisfies the probability constraint of incorrect adjustment with least cycles. Since the combustion suffers from cyclic variation, moving average based feedback control approach on the evaluation of consecutive in-cylinder pressure traces, is designed to track CA50 set point by adjusting spark advance. Finally, the experiments on a 6-cylinder 3.5-l SI gasoline engine validate the performance of the proposed strategies.