Observer-based Purge Estimation for Robust Air Fuel Ratio Control of Internal Combustion Engines

This paper presents a purge estimation method for a robust air fuel ratio control of internal combustion engines. The air fuel ratio control is a primary emission control mechanism of gasoline engines, and purge is one of the most critical disturbances that can lead to significant air fuel ratio excursions. In this work, Luenberger-like unknown input observers are proposed to estimate purge flow rate and purge fuel fraction using existing sensors available in production engine management systems. The convergence properties of the proposed observers are investigated analytically and numerically. The estimation method allows to improve accuracy of the air fuel ratio control by compensating for the purged fuel, thereby it allows aggressive purge in a wide range of operational conditions to meet stringent evaporative emission standards. Copyright (C) 2022 The Authors. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/license/by-nc-nd/4.0)