Mitsubishi Electric QD77MS User Manual page 523

[2] 2-axis circular interpolation control with sub point designation (INC
circular sub)
Operation chart
In the incremental system, 2-axis circular interpolation control with sub point
designation, positioning is carried out from the current stop position (start point
address) to a position at the end of the movement amount set in "[Da.6]
Positioning address/movement amount" in an arc path that passes through the sub
point address set in "[Da.7] Arc address". The movement direction depends on the
sign (+ or -) of the movement amount.
The resulting control path is an arc having as its center the intersection point of
perpendicular bisectors of the straight line between the start point address (current
stop position) and sub point address (arc address) calculated from the movement
amount to the sub point, and a straight line between the sub point address (arc
address) and end point address (positioning address) calculated from the
movement amount to the end point.
Forward direction
Movement amount
to sub point
Reverse direction
Reverse direction
Chapter 9 Major Positioning Control
Sub point address
(arc address)
Start point
address
Movement
amount to the
sub point
Movement amount to the end point
9 - 65
Movement by circular interpolation
Movement amount
to the end point
Arc center
Forward direction