Manual – IPOSplus®
65
6
Referencing
Position Detection and Positioning
When deciding whether to reference to the reference cam or zero pulse, note the follow-
ing points:
• The zero pulse moves when the motor is replaced.
• The reference cam could become inaccurate as a result of age, wear or switching
hysteresis.
• If the reference point is determined using the zero pulse and reference cam, and the
zero pulse is located exactly at the end of the reference cam, the switching transition
of the reference cam may be detected before or after the zero pulse (switching
hysteresis). The result may be a reference position which varies by a motor
revolution from one time to the next. The situation can be remedied by shifting the
reference cam (by about half a motor revolution).
• Unidirectional drives can only be referenced using a reference cam. Also note that
there is no defined distance between the reference cam and zero pulse of the
encoder for non-integer ratios. This means that in this case only the end of the
reference cam can be selected as the reference point.
• The length of the reference cam and the reference speeds must be selected so the
drive can reliably decelerate to the slower reference speed (reference speed 2) on
the reference cam. The end of the reference cam or the closest zero pulse of the
encoder system can be used as reference point.
• The zero pulse can only be used as a reference point when the encoder has a zero
pulse, the zero track is connected to the inverter and the PPR count < 5000 inc./
revolution.
INFORMATION
In case of reference travel of a drive system with absolute encoder (Hiperface
®
or
DIP), the position offset will be recalculated and overwritten by the reference travel
P905 Hiperface
®
offset X14 / P947 Hiperface
®
offset X15 or DIP offset P953 Position
offset, depending on the source set for the actual position.
INFORMATION
If you change P350/P351 reverse direction of rotation, you have to change these pa-
rameters prior to the reference offset or perform the reference offset again after
changing the parameters, because this change affects the actual position of the axis.
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