Control and stability analysis of a turbocharged diesel engine using singular-perturbation methods
Sprache des Vortragstitels:
GAMM Annual Meeting 2007
Sprache des Tagungstitel:
This contribution is concerned with the application of a nonlinear control and stability analysis for diesel engines equipped with a variable geometry turbocharger (VGT) and an exhaust gas recirculation (EGR) valve, using singular perturbation methods. The recirculation of exhaust gas from the outtake manifold of the intake manifold is an effective way to reduce the concentration of nitrogen oxides in the exhaust gas. Using a VGT, a fast transient response time at low engine speeds and high engine power without turbine overspeeding at high engine speeds is possible. The system to be controlled is described by the following simple scheme: air enters the system through the compressor and is led to the intake manifold. Mixed with the recirculated gas it is pumped into the engine. Inside, fuel is injected and the combustion takes place. The produced exhaust gas flows into the exhaust manifold. A part is recirculated to the intake manifold, the rest flows through the turbine, transferring energy to the compressor. For the controller design a simplified mathematical representation is given by a set of three ordinary differential equations. These equations can be split into two parts with slow and fast transient responce. The goal of the controller is to achieve desired values of the input manifold pressure and the compressor massflow, both given by the motor management system for a given point of operation. To guarantee that the deflection of the desired and actual signals converge to zero, the controller is equipped with two slow integral states. The equations for the closed loop system can be written as a nonlinear standard singular perturbated system. The asymptotic stability is shown with the choice of Lyapunov functions for the reduced and the boundary layer system such that the necessary interconnection conditions are also satisfied. The performance of the controller is demonstrated by simulation results also in combination with a more detailed simulation model.