The Use of Prior Knowledge to Accelerate the Determination of the Permissible Operating Envelope of an Internal Combustion Engine

Abstract

The paper details improvements in the technique used to locate the boundary of the permissible operating envelope (or limit space) of an engine. This process is an important step in the model-based calibration of engines and is currently conducted manually or using cautious automatic search algorithms because of the risks to engine integrity if operating limits are exceeded.

To improve this process, prior knowledge was used to mimic the behaviour of an expert calibrator following two strategies. The first was designed to offer a rapid search based on a similar premise to commercially available tools. The second scheme offers a thorough search of the limit space using a scheme that targets the extremes of the operating envelope. Both patterns were enhanced using prior knowledge generated from previous operating points in order to speed up the search. When implemented on the test bed the use of prior knowledge in this way has shown the potential to shorten the search time by up to 25 per cent. The thorough search pattern increased the accuracy of the limit space definition by up to 40 per cent but resulted in a significantly slower search.