Mitsubishi MELSEC-Q QD77MS, User Manual

Page: 487 / 976

9 - 54
Chapter 9 Major Positioning Control
POINTS
•
When the movement amount is converted to the actual number of command
pulses, a fraction appears after the decimal point, according to the movement
amount per pulse. This fraction is normally retained in the QD77MS and reflected
at the next positioning.
For the fixed-feed control, since the movement distance is maintained constant (=
the command number of pulses is maintained constant), the control is carried out
after the fraction pulse is cleared to zero at start.
[Accumulation/cutoff for fractional pulses]
When movement amount per pulse is 1.0 [
μ
m] and movement for 2.5 [
μ
m] is
executed two times.
→
Conversion to command pulses: 2.5 [
μ
m] ÷ 1.0 = 2.5 [PLS]
2PLS
2PLS 2PLS
3PLS(=2.5+0.5)
Movement
amount
0.5 PLS hold by the QD77MS is
carried to next positioning.
INC Linear 1
Fixed-feed 1
0.5 PLS hold by the QD77MS is
cleared to 0 at start and not
carried to next positioning.
2.5 m 2.5 m
• When the "reference axis speed" is set during 2-axis fixed-feed control, set so 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".
9.2.8 3-axis fixed-feed control (interpolation)
In "3-axis fixed-feed control" (" Da.2 Control system" = fixed-feed 3), three motors are
used to carry out fixed-feed control in a linear path while carrying out interpolation for
the axis directions set in each axis.
In fixed-feed control, any remainder of below control accuracy is rounded down to
convert the movement amount designated in the positioning data into the command
value to servo amplifier.
(Refer to Section 9.1.6 "Interpolation control" for details on interpolation control.)