Spark ignition engine fuel-to-air ratio control: An adaptive control approach

This paper presents the control of spark ignition (SI) internal combustion (IC) engine fuel-to-air ratio (FAR) using an adaptive control method of time-delay systems. The objective is to maintain the in-cylinder FAR at a prescribed set point, determined primarily by the state of the three-way catalyst (TWC), so that the pollutants in the exhaust are removed with the highest efficiency. The FAR controller must also reject disturbances due to canister vapor purge and inaccuracies in air charge estimation and wall-wetting (WW) compensation. Two adaptive controller designs are considered. The first design is based on feedforward adaptation while the second design is based on both feedback and feedforward adaptation incorporating the recently developed adaptive posicast controller (APC). Both simulation and experimental results are presented demonstrating the performance improvement by employing the APC. Modifications and improvements to the APC structure, which were developed during the course of experimentation to solve specific implementation problems, are also presented.