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Abstract |
Ignition Control by Ionization Current Interpretation
Spark advance setting in spark-ignited engines is used to place the
in-cylinder pressure curve relative to the top dead center. It is
demonstrated that ionization current interpretation is feasible to use
for spark advance control to optimize engine performance. A feedback
scheme, not a calibration scheme, based on ionization current is
proposed. It is thus related to pressure sensor feedback schemes, that
have reported good results, but have not yet proven cost effective due
to the cost of the pressure sensor. The method proposed here is very
cost effective since it uses exactly the same hardware and
instrumentation (already used in production cars) that is used to
utilize the spark plug as a sensor to detect misfire and as a sensor
for knock control. The only addition for ignition control is further
signal interpretation in the electronic engine control unit.
A key idea in our method is to use parameterized functions to describe
the ionization current. These parameterized functions are used to
separate out the different phases of the ionization current. Special
emphasis is made to get a correct description of the pressure
development. The results are validated on a SAAB 2.3 l production
engine by direct comparison with an in-cylinder pressure sensor (used
only for validation, not for control), but also by using a physical
model relating the ionization current to the pressure.
Lars Eriksson, Lars Nielsen and Jan Nytomt
1996
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Last updated: 2021-11-10
