Position Offset

Type:	Axis Parameter Register
Address:	RMC75: %MDn.1, where n = 12 + the axis number RMC150: %MDn.1, where n = 24 + the axis number RMC200: %MDn.21, where n = 384 + 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, P0, at which the Actual Position should be zero. Set the Position Offset to -P0. For details on scaling counts to Position Units, see the appropriate topic: