Rockwell Automation GMLC Reference Manual - Manual (Page 852)

Publication GMLC-5.2 - November 1999
Chapter
38
Axis Locked and Axis Done Conditions
To move an axis, input new command position parameters into a selected
motion block, then execute the block (or run the program). In the case of a
Move Axis block, for instance, the command position is ramped up at the
acceleration rate, incremented at the velocity, and decelerated at the
deceleration rate specified in the block.
The motion controller compares the actual position of the axis—the
current position as measured by the encoder or other feedback device—
against its command position, and computes position error. The motion
controller moves the axis by continually attempting to drive position error
to zero.
Moves, Jogs, and Time-Lock Cams
To the motion controller, a move, jog, or time-lock cam is considered
done—the Move Done condition—once the command position has been
reached (provided that the command position has not been changed by a
subsequent Move Axis, Jog Axis, or Time Lock Cam block). At this
moment, the controller stops commanding the axis to move.
However, because a small amount of position error can exist, the axis may
still be moving, and its actual position changing. The axis is not
considered locked (the Axis Locked condition) until both of the following
occurs:
• The Move Done condition is met.
• The position error (set as Error Tolerance in the Dynamics page of the
Configure Axis Use dialog box) of the axis is less than the position
lock tolerance (set as Lock Tolerance in the Positioning page of the
Configure Axis Use dialog box) for the axis.