UKF-Based Constrained Extremum-Seeking Control with Application to a Large-Bore Gas Engine

Abstract

For a turbo charged gas engine to operate at its peak efficiency with low emissions the operating point needs to be carefully tuned. The composition of the fuel gas changes depending on, e.g., production site in case of natural gas or raw material for bio gas or other gaseous fuels. Variances in the relevant characteristics of the engine environment such as temperature and humidity also have a big impact on the optimal set-point of variables such as ignition timing and waste gate valve settings. As it is difficult to accurately model the highly dynamic aspects of the combustion process these engines are generally operated using predefined maps. In this work an approach using on-line optimization via extremum-seeking control (ESC) of the ignition timing and turbo charger waste gate is presented for a large gas engine. For this a novel concept of using an unscented Kalman Filter for gradient estimation is developed and demonstrated first in a two-degree-of-freedom (2-DoF) benchmark scenario and then applied to an experimentally validated black-box model of a large-bore gas engine.