Air-path control for a prototype PCCI diesel engine

The tightening in diesel engines regulations for emissions control forced the automotive industry to face the challenge coming from these constraints. This led to an increase in the overall engine complexity, in both, mechanical and software domains. For what concerns this paper the increased complexity means to deal with and to manage the cross coupled and nonlinear behavior of the engine air-path. Here we propose a control system able to manage under steady-state conditions the airflow through the engine with the purpose of ensuring a smooth Premixed Charge Compression Ignition combustion behavior using the most simple and economical structure possible. The objective was to design a controller capable to handle the three air-path devices of Exhaust Gas Recirculation, Variable Geometry Turbochargers and \textit{flap} valve all together. Modeling of the system and control design are the two main areas on which we focused our attention in order to retrieve simplicity and system economy. All the trials needed to design the air-path controller were carried out on the mono-dimensional simulation software GT-Power by Gamma Technologies that has proven to be very effective in the simulation domain. The model was created by FPT Industrial and provided to us together with the engine. Based on that model we derived all our computations, in terms of system identification and validation, that led us to a feed-forward plus feedback control structure capable to cover the whole engine operating area. Simulations show very encouraging results also in presence of high disturbances in the outputs.