Optimal nonlinear control of a Diesel engine air-path system using VGT/EGR actuation

In this paper, an optimal nonlinear control technique based on the analytic solution of a performance index is used to derive a controller for the Diesel engine air system. The control objective is to achieve tracking of suitable references (corresponding to low emissions) for the air-fuel ratio and the fraction of the recirculated exhaust gas. The considered Diesel engine is a medium duty Caterpillar 3126B with six cylinders equipped with a variable geometry turbocharger and an exhaust gas recirculation valve. The proposed controller is designed on the reduced third order mean value model and implemented as a closed-form nonlinear model predictive control law on the full order model. In order to eliminate steady state offset, integral action is introduced. The resulting controllers, with and without integral action, are assessed through simulations with a SIL architecture using dSpace Simulator. The controller with integral action, exhibits good control performance, with zero offset and ensures global stability and tracking of output references.