Delta RMC151 - Manual (Page 909)

9 Register Reference
9.2.2.2.2. Position Offset
Type: Axis Parameter Register
RMC70 Address: %MDn.1, where n = 12 + the axis number
RMC150 Address: %MDn.1, where n = 24 + the axis number
System Tag: _Axis[n].PosOffset, where n is the axis number
How to Find: Axes Parameters Pane, Setup tab: Primary Control Setup
Data Type: REAL
Units: pu
Range: all
Default Value: 0
Description
Linear Axes
This parameter is used on position axes together with the Position Scale parameter to
convert the transducer feedback Counts to an Actual Position. After the Counts are scaled
to position units, this parameter is used to shift the position units.
Rotary Axes
This parameter is used on rotary position axes together with the Position Unwind and
Count Unwind parameters to convert the transducer feedback Counts to an Actual
Position.
The Count Unwind defines the number of counts in one machine cycle. The Position
Unwind defines the number of position units per machine cycle. The Position Offset
defines the value at which those position units begin.
Examples:
Position
Unwind
Position
Offset Position Range
360 0 0 to 360
360 -180 -180 to 180
360 60 60 to 420
Absolute Rotary axes also use the Count Offset parameter to move the zero point of the
Counts. The position range begins where the Counts are zero.
Changing this Parameter
Because this parameter affects motion, the axis must be disabled or in Direct Output
before writing to this parameter. The Enabled and Direct Output Status Bits indicate these
states of the axis. When changing this parameter from RMCTools, the software will
automatically do this for you. This may cause a halt on the axis, which is expected.
Setting the Offset
To set the Position Offset, first set the Position Scale. Then, determine the position, P
0
, at
which the Actual Position should be zero. Set the Position Offset to -P
0
. For details on
scaling counts to Position Units, see the appropriate topic:
• MDT Scaling
• SSI Scaling
• Analog Position Scaling
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