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Knock Intensity and Torque Conrol on an SVC Engine

Knock is a phenomenon that limits how efficiently an engine can operate. Severe knock is harmful to the engine and must therefore be avoided. Controlling the knock intensity is complicated by a phenomenon called cycle to cycle variations. Because of these variations, the knock intensity must be considered a stochastic variable and the control is made on a mean value from a large number of cycles. The SVC (Saab Variable Compression) concept adds the compression ratio as an extra degree of freedom. At Vehicular systems, research is done on how to put this additional variable to its best use. A controller is developed that control the engine to a desired knock intensity and torque, using the ignition angle and the pedal position. The controller is implemented as two separate controllers in Matlab and Simulink. These are merged together with a Stateflow chart. A confidence interval calculation is implemented for the mean value of the knock intensity. A program is also developed to process a large number of operating points and make measurements in all of them. The conclusion is that the basic construction of the controller and the script are filling their functions but that there are some improvements left to be done. The controller is rather slow and the calculations of the confidence interval needs further refinement.

Klara Sinnerstad


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