8-10
Drive Functions
MPH-02, MPB-02, MPD-02
DOK-INDRV*-MP*-02VRS**-FK01-EN-P
The motion range required for homing depends on the encoder used:
•
For encoders of group 1, 2 or 3 motion over the entire travel distance
of the axis can be required.
•
For encoders of group 4 the axis only has to pass two neighboring
distance-coded reference marks (see section "Motion Range for
Homing Encoders with Distance-Coded Reference Marks").
Note:
With encoders of group 4 the controller can calculate the
position of the dedicated point on the basis of the detected
position difference of two neighboring distance-coded
reference marks!
To identify a dedicated point of an axis the following signals can be used:
•
reference marks of the encoder
•
home switch at the axis
The reference mark signal is generally used for detecting the position of
the dedicated point because this signal allows detecting the position within
the scope of the encoder precision.
The reference mark signal is generally used
•
for detecting the end of the travel range in the case of linear axes
- and -
•
for selecting a reference mark signal, when these signals occur
several times over the travel range.
Number of reference mark signals occurring over the travel range
one signal
several signals
Relative encoder of ...
rotary axis
linear axis
rotary axis
linear axis
... group 1,2 (rotary encoder)
HS: no
HS: yes
HS: yes
HS: yes
... group 3 (linear encoder)
------------
HS: yes
------------
HS: yes
... group 4 (rotary/linear encoder)
------------
------------
HS: no
HS: yes
Fig. 8-4:
Recommendation for using a home switch (HS)
In
S-0-0147, Homing parameter
select which signals are to be evaluated
by the controller for determining the dedicated point (reference marks
and/or home switches).
Note:
If there isn’t any reference mark signal available on the
encoder-side, the edge reversal of a home switch signal can
also be used of detecting the dedicated point. This has to be
set in parameter S-0-0147 by deactivating the reference mark
evaluation!
The axis zero point and the reference point are positions determined on
the machine side. The position of the dedicated point ideally is identical to
the reference point, the position of the dedicated point, however, mostly is
influenced by the encoder arrangement. The position difference between
reference point and dedicated point is transmitted to the controller via the
so-called reference offset.
Motion Range for Homing
Identifying a Dedicated Point
Reference Point, Axis Zero Point
and Dedicated Point for
Encoders of Groups 1, 2, 3
Courtesy
of
CMA/Flodyne/Hydradyne
▪
Motion
Control
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Hydraulic
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Pneumatic
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Electrical
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Mechanical
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(800)
426-5480
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www.cmafh.com
