Linköpings Universitet

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Torque Modeling and Control of a Variable Compression Engine

Abstract The SAAB variable compression engine is a new engine concept that enables the fuel consumption to be radically cut by varying the compression ratio. A challenge with this new engine concept is that the compression ratio has a direct influence on the output torque, which means that a change in compression ratio also leads to a change in the torque. A torque change may be felt as a jerk in the movement of the car, and this is an undesirable effect since the driver has no control over the compression ratio. The aim of this master's thesis work is to develop a torque control strategy for the SAAB variable compression engine. Where the main control objective is to make the output torque behave in a desirable way despite the influence of compression ratio changes. The controller is developed using a design method called Internal Model Control, which is a straightforward way of both configuring a controller and determining its parameters. The controller has been implemented and evaluated in a real engine, and has proved to be able to reduce the effect of compression ratio disturbance.

Andreas Bergström

2003

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