Modeling and Dynamical Feedback Control of a Vehicle Diesel Engine Speed and Air-Path

This paper presents a modeling and dynamical feedback stabilization control of a diesel engine which is equipped with a variable geometry turbocharger (VGT) and exhaust gas recirculation (EGR) valve. A fourth-order dimensional nonlinear model which takes into account the engine crankshaft speed dynamics and the air-path dynamics is proposed for the considered diesel engine. The difficulties for the control design are that the referred system is nonlinear, nonminimum phase unstable and coupled system. The fuel flow rate Wf which is considered as input for the engine crankshaft subsystem and acts as an external perturbation for the three-order dimensional nonminimum phase air-path subsystem. The global control objectives are to track desired values of engine speed, intake manifold pressure and compressor flow mass rate which can be suitably chosen according to low emission criterions. For the considered objectives, a dynamical feedback stabilization control with a two-loop structure of inner outer loop is proposed. The inner loop considers a control based on a Lyapunov function which realizes the desired engine speed trajectory tracking. The outer loop which is developed from a particular extended nonlinear air-path subsystem with its modified outputs concerns the coordinated EGR and VGT control and ensures both the desired intake manifold pressure and the desired compressor mass flow rate trajectory tracking. Meanwhile, this outer loop dynamical feedback stabilization control provides also the external fuel mass flow rate perturbation rejection. From the corresponding numerical simulation results, the proposed method efficiency is validated.