Search Results

This paper introduces a model-based adaptive controller designed to compensate mixture ratio dynamics in an SI engine. In the basic model the combined dynamics of wall-wetting and oxygen sensor have to be considered because the only information about process dynamics originates from measuring exhaust λ. The controller design is based on the principles of indirect Model Reference Adaptive Control (MRAC). The indirect approach connotes that explicit identification of the system parameters is required for the determination of the controller parameters. Due to nonlinearities and delays inherent in the process dynamics, an adaptive extended Kalman filter is used for identification purposes. The Kalman filter method has already been described in detail within an earlier paper [1]. It proves to be ideally suited to deal with nonlinear identification problems. The estimated parameters are further used to tune an adaptive observer for wall-wetting dynamics.

Anti-knock index (AKI) is a metric that can be used to quantify the anti-knock performance of a fuel and is the metric used in the United States. AKI is the average of Research Octane Number (RON) and Motor Octane Number (MON), which are calculated for every fuel on a Cooperative Fuel Research (CFR) engine under controlled conditions according to ASTM test procedures. Fuels with higher AKI have better knock mitigating properties and can be run with a combustion phasing closer to MBT in the knock limited operating region of a gasoline engine. However, fuels with higher AKI tend to be costlier and less environmentally friendly to produce. As an alternative, the anti-knock characteristics of lower AKI fuels can be improved with water injection. In this sense, the water injection increases the ‘effective AKI’ of the fuel.