Siemens SIMATIC FM 452, Руководство пользователя

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Machine Data and Cam Data
8-10
FM 452 Electronic Cam Controller
C79000-G7076-C452-04
Distance Cams and Hysteresis
A distance cam is activated in the following situation:
•
the detected actual value is within the distance cam and
•
no hysteresis is active.
The position of the switching point depends on where the direction changes.
Activation direction
2 3 4 5 6 7 8 9
1
0
Change of
direction
CS
CE
Change of
direction
Cam
Hysteresis
1)
Cam is activated since the cam
start is reached in the positive
activation direction
Cam remains active despite
new direction due to hysteresis
2)
3)
4)
5)
1)
Cam is deactivated at the end
of the hysteresis
Cam remains deactivated after
the change in direction
Cam is activated again at the
end of the hysteresis
2)
3)
4)
5)
Figure 8-1 Activation of a Distance Cam with Hysteresis
Note
Distance cams that are shorter than the hysteresis can be hidden by the
hysteresis when there is a change in direction.
Time Cams with Hysteresis
A time cam is activated in the following situation:
•
the cam start is reached in the activation direction and
•
no hysteresis is active.
Note
If the range between the reversal point and the start of the time cam is less than
the hysteresis, the time cam will be “hidden” by the hysteresis.
Figure 8-2 illustrates a time cam that is not activated again.
2 3 4 5 6 7 8 9
1
0
Change of
direction
Change of
direction
CS
Cam Hysteresis
Activation direction
1)
Cam is activated since the cam
start is passed in the
positive activation direction
After the change in direction,
the cam remains active until the
on time has expired regardless
of the hysteresis
2)
3)
Cam start is hidden by the
hysteresis, the cam is not
activated
3)
2)
1)
Figure 8-2 Activation of a Time Cam with Hysteresis