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MELSEC-Q
9 MAJOR POSITIONING CONTROL
POINTS
(1) When the movement amount is converted to the actual number of output pulses, a fraction
appears after the decimal point, according to the movement amount per pulse. This fraction is
normally retained in the QD75 and reflected at the next positioning.
For the fixed-feed control, since the movement distance is maintained constant (= the output
number of pulses is maintained constant), the control is carried out after the fractional pulse is
cleared to zero at start.
Accumulation/cutoff for fractional pulses
When movement amount per pulse is 1.0 m and movement for 2.5 m is executed two times;
Conversion to output pulses: 2.5[ m] 1.0 = 2.5 pulses
2.5 m 2.5 m
INC line1
Fixed-feed 1
2 pulses
3 pulses (=2.5+0.5)
2 pulses
2 pulses
Movement
amount
Output pulses
0.5 pulse hold by the QD75 is
carried to next positioning.
0.5 pulse hold by the QD75 is cleared to 0 at start
and not carried to next positioning.
(2) For 4-axis fixed-feed control, set the "reference axis speed" and make setting so that the major
axis side becomes the reference axis. If the minor axis side is set as the reference axis, the major
axis side speed may exceed the "
Pr.8
Speed limit value".
(3) Refer to Section 9.1.6 "Interpolation control" for the reference axis and interpolation axis
combinations.
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