Mitsubishi Electric MELSEC-L LD75P User Manual page 398

(1) Circular interpolation error compensation
In circular interpolation control with center point designation, the arc path calculated from the start point address
and center point address may deviate from the position of the end point address set in " Da.6 Positioning
address/movement amount". ( Page 139, Section 5.2.4 (11))
(a) Calculated error  "[Pr.41] Allowable circular interpolation error width"
Circular interpolation control to the set end point address is carried out while the error compensation is carried
out.
(This is called "spiral interpolation".)
In circular interpolation control with center point designation, an angular velocity is calculated on the
assumption that operation is carried out at a command speed on the arc using the radius calculated from the
start point address and center point address, and the radius is compensated in proportion to the angular
velocity deviated from that at the start point. Thus, when there is a difference (error) between a radius
calculated from the start point address and center point address (start point radius) and a radius calculated
from the end point address and center point address (end point radius), the composite speed differs from the
command speed as follows.
• Start point radius > End point radius: As compared with the speed without error, the speed becomes slower
as end point address is reached.
• Start point radius < End point radius: As compared with the speed without error, the speed becomes faster
as end point address is reached.
(b) Calculated error > "[Pr.41] Allowable circular interpolation error width"
At the positioning start, the error "Large arc error deviation" (error code: 506) will occur and the control will not
start.
The machine will immediately stop if the error is detected during positioning control.
396
Path using spiral interpolation
Center point address
Start point address
Error
Calculated end point
address
End point address