This block detects when a PID tuning period should start and
end. Specifically, the tuning period is triggered to begin when
either tOn or tOff becomes greater than
0. The tuning period is triggered to end when either
tOn or tOff changes after the tuning
period starts, as illustrated below:

Note:
This block monitors the values oftOn and
tOff to detect the start and end of the tuning period.
Rapid changes in these values can cause unreliable event triggering
during variable time-step integration. To enhance robustness, a
small tolerance eps is introduced. Increasing
eps can help ensure correct event detection if any
events are missed.
J. Berner (2017). "Automatic Controller Tuning using Relay-based Model Identification." Department of Automatic Control, Lund University.