Mitsubishi A1SD75P1-S3 User Manual page 341

9 MAIN POSITIONING CONTROL
During arc interpolation control with center point designation, the angle is calculated on
the assumption that movement at the command speed occurs on an arc drawn in the
radius calculated from the start point and center point addresses, and the radius is
corrected in proportion to the angular velocity from the start point.
Therefore, if there is difference between the radius (radius at start point) calculated
from the start point and center point addresses and the radius (radius at end point)
calculated from the end point and center point addresses, the resultant velocity has the
following tendency, different from the command speed.
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Circular interpolation error compensation
In circular interpolation control with center point designation, the arc path
calculated from the start point address and arc address may deviate from the
position of the end point address set in " Da.5 Positioning address/movement
amount".
(Refer to " Pr.42 Allowable circular interpolation error width".)
(1) Calculated error " Pr.42 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".)
(2) Calculated error > " Pr.42 Allowable circular interpolation error width"
At the positioning start, an 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.
Path using spiral interpolation
Start point address
If the radius at the start point is larger than that at the end point:
The velocity becomes slower as the end point address draws nearer when
compared with the case including no error.
If the radius at the start point is smaller than that at the end point:
The velocity becomes faster as the end point address draws nearer when
compared with the case including no error.
Error
Center point address
9 - 40
MELSEC-A
Calculated end point
address
End point address