Control Structures for Low-Emission Combustion in Multi-Cylinder Engines

Traditionally, heavy-duty diesel engines have high efficiencies but also high emissions of NOx and soot particles. New engine concepts show the potential to retain diesel-like efficiencies while reducing emissions by forming a completely or partially homogeneous mixture of fuel and air prior to ignition through compression. The long ignition delay required to form this homogeneous mixture makes the combustion process less predictable and inherently more difficult to control.

This thesis summarizes work on control structures for three different setups of such low-emissions combustion engines. In a port-fuel injection engine, it was shown that combining two control variables in a mid-ranging control structure can address the problem of actuator saturation. In a fumigation engine, control was proven to be a powerful tool for automatic calibration in a laboratory setting. In a direct injection engine, LQG controllers were designed to optimize an emissions trade-off cost function during transients. Experiments were performed on a six-cylinder heavy-duty engine, and multi-cylinder effects and complications were explicitly considered in the work.