Browse Publications Technical Papers 2005-01-2128
2005-05-11

Transient Control of HCCI Combustion by aid of Variable Valve Timing Through the use of a Engine State Corrected CA50-Controller Combined with an In-Cylinder State Estimator Estimating Lambda 2005-01-2128

One of the main challenges with the Homogeneous Charge Compression Ignition, HCCI, combustion system is to control the Start Of Combustion, SOC, for varying load and external conditions. A method to achieve this on a cycle-by-cycle basis is to vary the valve timing based on a feedback signal from the SOC of previous cycles. The control can be achieved with two basic valve-timing strategies named the Overlap- and the IVC-method. The Overlap-method works by trapping of residuals while the IVC-method affects the effective compression ratio.
In an earlier paper it has been shown that if the two methods are incorporated into one controller, SOC can be controlled in a relatively large operating window although the transient performance was not sufficient. The reason is that a simple PI-controller cannot be made fast enough to cope with the transients without magnifying the cycle-to-cycle variations of the combustion into instability. It has also been shown that a controller based around a non-linear compensation extended with an engine state correction will improve the control performance. The non-linear compensation used is based on the inverse of the non-linear function from valve timings to ignition delay.
In this work an in-cylinder state estimator is added to the non-linear compensation controller in order to further improve the control performance. The in-cylinder state estimator is in the present version estimating lambda and aimed at improving load transients. Control performance from engine tests conducted on a single cylinder engine equipped with a hydraulic valve system is reported.

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