.Modelica_Requirements.ChecksInSlidingWindow.MaxFrequency

Information

Syntax

freqLimited = MaxFrequency(check=..., window=..., freqHzMeanMax=...).y;

Description

In any (sliding) time window of length window, the mean frequency of the Boolean input check is limited by freqHzMeanMax. With T the time period for a rising, falling and rising edge of check, the frequency is defined as freqHz = 1/T. Therefore, in any sliding window the following constraint shall hold:

if nCrossing > 1 then
  freqHzMean = 1/(window/( (nCrossing-1)/2 ));
else
  freqHzMean = 0
end if;

freqHzMean ≤ freqHzMax

where nCrossing is the number of crossing edges of check in the last time window of length window. The mean frequency over the sliding time window is also provided as additional output signal freqHzMean. If the mean frequency is not larger as freqHzMeanMax, output y is set to true, otherwise to y = false.

Example

The property is demonstrated with the following example calling the block as:

results in

	simulation result

Note, the check signal has first a frequency of 2 Hz, then of 4 Hz, then of 2 Hz and finally of 0 Hz. The MaxFrequency block can reproduce these frequencies approximately. It is not exact, because the frequency is only determined based on the rising and falling edges of check. However, it is slightly more precise as using the MeanRisingFrequency block that takes only the rising edges of check into account.