Cyclic referencing
4.8.4.1 Cyclic referencing with digital input
The value range of the rotary table can be referenced when passing the defined
home switch by hm08 home switch source. Thereby the positive edge of the initia-
tor is selected at positive direction and the negative edge at negative direction.
This function is activated by presetting a value unequal zero in ps20 range ref win-
dow.
The referencing is only executed if the edge is in the defined window by ps20. At
valid edge the internal position offset hm09 is modified by way that the actual posi-
tion st33 position actual value is assigned to the preset reference value set with
hm00 (CiA 0x607C) home offset at triggering edge.
Contrary an error counter is increased in ps21 if the window defined in ps20 range
ref window is passed without recognizing an initiator. The error counter is reset
again with valid initiator.
The homing mode with method 18 is reasonable for the first referencing to reach
the same mechanical position which is used also for the cyclic referencing.
4.8.4.2 Automatic cyclic referencing
If a systematic error occurs due to an odd gear factor, it can be corrected automati-
cally. The following two objects are installed for this purpose.
Example:
A drive shall operate a rotary table via a 7/9 gearbox and a toothed belt with gear
ratio 1/13. For 7 rotations of the rotary table, the motor must rotate 9 * 13 = 117
times.
The encoder is mounted on the motor, so the position is specified as motor posi-
tion.
The total gear ratio results to:
One revolution of the rotary table = 117 / 7 = 16.714 motor revilutions.
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