Mitsubishi Electronics QD75P, QD75D user manual Circular interpolation error compensation, Pr.41

9 MAJOR POSITIONING CONTROL

MELSEC-Q

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 " amount".

Da.6

Positioning address/movement

(Refer to "

Pr.41

Allowable circular interpolation error width".)

(1) 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".)

Path using spiral interpolation	Error
	Calculated end point
	address
	End point address

Start point address Center point address

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.

(2) Calculated error > "

Pr.41

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.

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