  Because fuel efficiency is significantly impacted by the timing of combustion
in internal combustion engines, accurate control of combustion phasing is
critical. In this paper, a nonlinear combustion phasing model is introduced and
calibrated, and both a feedforward model-based control strategy and an adaptive
model-based control strategy are investigated for combustion phasing control.
The combustion phasing model combines a knock integral model, burn duration
model and a Wiebe function to predict the combustion phasing of a diesel
engine. This model is simplified to be more suitable for combustion phasing
control and is calibrated and validated using simulations and experimental data
that include conditions with high exhaust gas recirculation fractions and high
boost levels. Based on this model, an adaptive nonlinear model-based controller
is designed for closed-loop control, and a feedforward model-based controller
is designed for open-loop control. These two control approaches were tested in
simulations. The simulation results show that during transient changes the CA50
(the crank angle at which 50% of the mass of fuel has burned) can reach steady
state in no more than 5 cycles and the steady state errors are less than +/-0.1
crank angle degree (CAD) for adaptive control, and less than +/-0.5 CAD for
feedforward model-based control.
