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.
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Last updated: 2019-08-05