Pressure and temperature-based adaptive observer of air charge for turbocharged diesel engines

In this paper we design an adaptive air charge estimator for turbocharged diesel engines using intake manifold pressure, temperature and engine speed measurements. This adaptive observer scheme does not depend on mass air flow sensors and can be applied to diesel engines with no exhaust gas recirculation (EGR). The performance of the adaptive scheme is shown in simulations to be comparable to conventional air charge estimation schemes if perfect temperature measurements are available. The designed scheme cannot estimate fast transients and its performance deteriorates with temperature sensor lags. Despite all these difficulties, this paper demonstrates that (i) the proposed scheme has better robustness to modelling errors because it provides a closed-loop observer design, and (ii) robust air charge estimation is achievable even without air flow sensors if good (fast) temperature sensors become available. Finally, we provide a rigorous proof and present the implementation challenges as well as the limiting factors of this adaptation scheme and point to hardware and temperature sensor requirements. Copyright (C) 2004 John Wiley Sons, Ltd.