6 "Cam/Cam Track” Technology Object
TOs of S7-1500(T)
Entry ID: 109743134, V1.0, 05/2017
Siemens AG 2017 All rights reserved
6.1.2 Time-based cams
Contrary to distance output cams (position-based cams), time-based (output) cams
are only defined by the absolute start position in relation to the axis. The cam
length is the result of the also specified switch-on time of the cam. Here, it can also
be generally differentiated between the setpoint and actual position of the axis.
Figure 6-3 Time-based (output) cam
The position range in which the time-based cam is switched on depends on the
motion direction and the speed of the axis. The signal output of the cam is started
by moving over the start position and lasts for the switch-on time defined.
Figure 6-4 Direction-dependency of time-based (output) cams
Movement in positive direction Movement in negative direction
Path
100 110 1209080
Path
100 110 1209080
Start position End position Start position
Rising
edge
Rising
edge
Falling
edge
+ -
Switch on
duration
Switch on
duration
End position
Falling
edge
6.1.3 Hysteresis
Undesired switching actions of the cam due to fluctuating speed or small direction
changes, for example, for the actual value reference of the cams, can be
suppressed via the setting of the hysteresis.
The internal position of the axis or the encoder to which the responses of the cams
or the cam track relates, is only changed again after a change of direction when the
difference in position exceeds the set hysteresis value. However, if the axis or the
encoder continuous the movement in the same direction, the internal position of
the axis or the encoder is adjusted straight away again.
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