LQG control for minimization of emissions in a diesel engine

The problem of minimizing emissions of NO_x and soot in a diesel engine using fuel injection timings and exhaust gas recirculation (EGR) valve position in a low-pressure EGR system as control variables is addressed. Two feedback variables are computed from in-cylinder pressure sensor data, the crank angle degree of 50% fuel burnt, and the ignition delay. Empirical maps of NO_x and soot according to the feedback variables form the basis of a quadratic cost function in the feedback variables which is minimized by LQG control. For a multi-cylinder engine, the number of control variables will be less than the number of output variables to be controlled, and the consequences of this setup for the LQG controller is addressed. Experimental results verify the performance of the controller at a fixed operating point of a six-cylinder heavy-duty engine.