4 Feed Axis Operation
4.5.2 Finite-length/Infinite-length Axes and Absolute Position Detection Settings
4-16
Terminology: Absolute Value Data
The absolute value data that is stored in an absolute encoder is the number of turns from the absolute base
position (multiturn data: N).
The initial incremental pulse (PO) is a pulse that represents the transition from the phase C position at the
point when the absolute encoder is initialized.
When the absolute encoder is reset, only the number of rotations from the absolute reference position (mul-
titurn data: N) is cleared. The initial incremental pulse (PO) is not changed.
Additional Information: Absolute Position Calculations
The absolute position is calculated according to the following formula:
Absolute position (P) = N
×
RP + PO
The conditions for the above formula are as follows:
• PO: Number of initial incremental pulses
• N: Number of rotations from the absolute reference position (multiturn data)
• RP: Number of feedback pulses per motor rotation
4.5.2
Finite-length/Infinite-length Axes and Absolute Position Detection Settings
There are two types of axes: infinite-length axes, which reset the current machine coordinate system position
to a specified value every rotation, and finite-length axes, which do not reset the current position.
Use finite-length axes to perform operations within a defined area or range.
Use an infinite-length axis for rotary tables and other operations that require the current machine coordinate
system value to be reset to 0 every rotation.
To manage positions for an infinite-length axis, the current position must be reset at regular intervals. This
must be implemented on the host controller.
For an infinite-length axis, reset the mechanical position, reference position, and current value at a regular
interval when the position reaches the reset position set for the axis (POSMAX). This is primarily effective for
axes such as those used for a rotary table. Implement this functionality on the host controller to use an axis as
an infinite-length axis.
To manage the position of an infinite-length axis, first the pulse position and encoder position are always
stored as paired information in the battery backup memory of the host controller. This data is used as the
power OFF pulse position and the power OFF encoder position when the power supply is turned ON again.
The following formula is used to find the pulse position from the relative encoder position.
Pulse position = Power OFF pulse po (Encoder position - Power OFF encoder position)
*
*The portion in parentheses ( ) represents the travel distance (relative encoder position) while the power
supply is OFF.
Terminology: Encoder Position
The encoder position is the absolute encoder position information (Multiturn data
×
Number of encoder
pulses per encoder ro Initial incremental Incremental pulses moved since turning ON the
power) and corresponds to the machine coordinate system position (APOS).
Terminology: Pulse Position
The pulse position is the position information managed by the host controller converted into pulses.
To use an absolute encoder for absolute position detection, you must set the correct host controller settings and
SERVOPACK parameters. The setting methods for the position detection and coordinate system settings
depend on whether a finite-length or an infinite-length axis is used.
For details on absolute position detection, refer to
4.5.3 Procedure for Setting Up the Absolute Position
Detection System
.
POSMAX
0
