Advanced control for fuel economy and emissions improvement in spark ignition engines.

Abstract

Fuel economy is one of the major objectives of modern engine control. In addition, three major pollutants from the vehicle (<italic>CO </italic>, <italic>HC</italic> and <italic>NO_x</italic>) have been stringently regulated both in the U.S. and world wide, and these emissions mandates as well as fuel economy have engendered a great deal of research on engine technology. The recently developed engines are fuel-injected and host a wide-array of new aftertreatment devices, sensors, actuators, and recent innovative engine operations such as lean burn and gasoline direct injection. Part of this dissertation exploits the potential benefits of air flow actuation in a SI engine. For this purpose, a mostly classical, and modern nonlinear controllers are designed, and significant engine performance measures such as average manifold pressure, emissions, and drivability are evaluated. In particular, the nonlinear controller has two novel features. Firstly, a recovery scheme for integrator wind-up due to input constraints is directly integrated into the control design. The second novel feature is that the positive semi-definite control Lyapunov function methodology is applied to a discrete-time model. This dissertation also investigates the benefits of a gasoline direct injection engine with novel aftertreatment. The lean burn and gasoline direct injection engine can consume a smaller amount of fuel in part load. However, the major drawback of these engines is that the tailpipe <italic>NO_x</italic> emissions level is not acceptable. A promising solution that has emerged in the area is the implementation of the lean <italic>NO_x</italic> trap for aftertreatment. The lean <italic>NO_x</italic> trap is a catalytic device capable of capturing <italic>NO_x</italic> in fuel-lean exhaust gas, which must be periodically purged by fuel-rich exhaust gas. Thus, the purging strategy, which includes the purging duration, purging frequency, and the amount of rich fuel during purging, strongly affects the fuel economy. In this dissertation, the optimal purging strategy to achieve fuel economy and low <italic>NO_x</italic> emissions is studied.