Applied Output Error Identification: SI Engine Under Normal Operating Conditions

Abstract: This report presents work done in the field of output error identification, with application to spark ignition (SI) engine identification for the purpose of air to fuel ratio control. The generic parts of the project consist mainly in setting out the basis for the design of output error identification software. Efficiency issues related to linear state space models have also been explored, and although the software design is not made explicit in this report, many of the important concepts have been implemented in order to provide powerful abstractions for the application to SI engine identification. The SI engine identification data was obtained under normal operating conditions. The goal is to re- estimate models without utilizing a virtual measurement which has been used successfully to estimate models in the past. This turns out to be a difficult problem much related to the lack of excitation in the system input, shortcomings of the fuel dynamics model and the unknown and hard to estimate exhaust sensor characteristics. Indeed, the larger of the previously estimated models are found not to be identifiable in the present situation. However, trivial restrictions of the models (not meaning restriction to trivial models) avoid that problem.