Data-Driven Near-Optimal On-Line Control for an Electrically Heated Catalyst-Equipped Gasoline Engine

Abstract

An integrated electrically heated catalyst (EHC) in the three-way catalyst (TWC) of a gasoline internal combustion engine (ICE) is a promising technology to reduce engine cold-start pollutant emissions. Pre-heating the TWC ensures earlier catalyst light-off of a significant portion of the TWC. In such a case, the engine could readily be operated in a fuel-optimal manner since the engine cold-start emission is efficiently treated by the warmed-up EHC-equipped TWC. Pre-heating the EHC is an effective way to reduce cold-start emissions, among other possible EHC strategies. However, it might not always be possible to use pre-heating if the engine-start time is uncertain. In such a case, pre-heating can be started when the engine start is known with greater confidence and post-heating the catalyst could be followed. It would then be natural to turn off the EHC when the payoff for the electrical energy spent is no longer effective in engine cold-start emission reduction. The point in time at which to stop the EHC thus needs to be controlled. A model-free on-line adaptive controller aimed at minimizing the total equivalent emission is proposed, which is based on a set of precomputed look-up optimum EHC stop times for the various possible fuel consumption trajectories. Compared to the theoretically optimal controller, the proposed controller gives a penalty of about 1% emission-based cost. A simulation framework for cold-start control and equivalent emission metric developed earlier are used in conjunction with a validation proposal to compare the performance of the candidate controllers.