Modeling and model based control design of the VGT-EGR system for intake flow regulation in diesel engines

Model based control design has been gaining popularity in the control research community. In this research we tackle the problem of multivariable control design for the coordinated actuation of the VGT-EGR system. A mean value model of a Diesel engine for automotive application is developed. The model is developed based on a combination of physics based first principles and empirical formulations. Essential subsystems like the variable geometry turbocharger and the intercooler and the EGR cooler are included in the model. It is shown that the presence of exhaust gas recirculation introduces a substantial degree of subsystem coupling. The effect of sharp fueling transients is also discussed. Control design is further complicated by the highly nonlinear nature of the plant and its nonminimum phase type behavior. Results of the detailed analysis of both the open loop and closed loop plant behavior under these interacting influences are presented.; Control design is based on a reduced order model and is carried out in stages. The control objective is to achieve desired EGR and airflow rates into the engine. In the first stage single input control is designed for the EGR under the assumption that the other control inputs, fuel command and VGT, are available in an ideal manner from an external controller, this process is then reversed for control design of the VGT. In the second stage a multivariable controller for VGT-EGR is designed. Results of closed loop performance of the plant suggest that better regulation of the desired flow rates can be achieved under the influence of a coordinated control action. A substantial improvement in the transient performance is observed with multivariable control.; Control design is carried out in the Sliding Mode framework. An in depth analysis for the selection of the sliding surfaces based on an understanding of the essential dynamics of the system is presented. For the multivariable control design we extended the input output linearization technique to the Sliding Mode framework.