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The 30 minus 5 encoder pattern has 30 teeth distributed equidistantly about a rotating target of which 5 specific teeth have been removed. The figure illustrates the pattern.
The distribution of missing teeth about the target allows each detected missing tooth to act as a synchronization point. The crank encoder will synchronize from a stall condition upon observing two missing teeth. Each detected missing tooth after initial synchronization allows resynchronization to occur. A crank synchronization error results if the tracked crank angle position does not equate to the absolute position inferred at the resynchronization point.
A resynchronization can temporarily impact the behavior of crank-synchronous blocks. Impacts include a pulse not scheduling as expected, having it occur twice, or being malformed. The system will recover, but the initial impact is unavoidable because the correction to the crank angle position results in a step change in position that may disrupt the underlying pulse scheduling software.
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