9-14
Extended Drive Functions
MPH-02, MPB-02, MPD-02
DOK-INDRV*-MP*-02VRS**-FK01-EN-P
By starting the "set absolute measuring" command the previous,
incremental actual position value of the measuring encoder at a reference
position of the axis or shaft is set to a defined value. The reference
position corresponds to the current axis position at the start of the
command.
The new actual position value at the reference position after "set absolute
measuring" is the value of parameter
•
P-0-0087, Actual position value offset of measuring encoder
.
P-0-0052
new
= P-0-0087
P-0-0052:
actual position value of measuring encoder
P-0-0087:
actual position value offset of measuring encoder
Fig. 9-9:
Actual position value of the measuring encoder after "set absolute
measuring"
In order that an encoder to be evaluated in absolute form maintains the
position data reference to the axis or shaft after "set absolute measuring",
the absolute encoder offset is stored in the encoder data memory
(
P-0-1022, Absolute encoder offset 3, encoder memory
) and in the
parameter memory (
P-0-0179, Absolute encoder buffer 3 (measuring
encoder)
).
Note:
Storing the absolute encoder offset in the encoder data
memory and in the parameter memory allows recognizing
whether the absolute encoder that had been homed was
replaced!
If the command "set absolute measuring" is cyclically used in the
operational sequence, it makes sense to store the absolute encoder
offset temporarily only. This kind of storage does not affect the service life
of the encoder data memory and the parameter memory. In parameter
S-0-0269, Parameter buffer mode
it is possible to select whether
parameter values are to be stored permanently or temporarily.
Note:
When the absolute encoder offset is stored temporarily, the
measuring encoder loses the position data reference to the
axis when the controller is switched off or when the parameter
mode ("P2") is activated.
For the measuring encoder the command "set absolute measuring" can
only be activated when the drive is ready for operation but inactive ("bb",
"AB").
When the "set absolute measuring" command is started, the reference of
the selected encoder is cleared first (
P-0-0331, Status of measuring
encoder
). After the reference was cleared the new actual position value
(
P-0-0087, Actual position value offset of measuring encoder
) takes
effect immediately and the reference bit is set again.
Establishing Position Data Reference for Relative Measuring
Encoder
The position data reference of a relative measuring encoder to an axis or
shaft is established by means of a reference mark signal of the encoder.
To do this, it is first necessary to activate the reference mark evaluation
for the measuring encoder in the respective bit of
P-0-0330, Control
word of measuring encoder
.
If the reference mark evaluation is still active, it first has to be deactivated
and then activated again.
Reference Position
Storing the Absolute Encoder
Offset
Parameter Buffer Mode
Sequence of "Set Absolute
Measuring"
Activating the Homing
Procedure
Courtesy
of
CMA/Flodyne/Hydradyne
▪
Motion
Control
▪
Hydraulic
▪
Pneumatic
▪
Electrical
▪
Mechanical
▪
(800)
426-5480
▪
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