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9 MAJOR POSITIONING CONTROL
POINTS
(1) The movement direction is not checked during interpolation operations. Thus, automatic deceleration to a stop will
not be carried out even if the movement direction is changed (See the figures below).
Because of this, the interpolation axis may suddenly reverse direction.
To avoid this sudden direction reversal in the interpolation axis, set the pass point to continuous positioning control
"01" instead of setting it to continuous path control "11".
[Positioning by interpolation]
Positioning data
No.1
Interpola-
tion axis
Positioning data No.1 • • • Continuous path control
(2) When the interpolation axis reveres direction suddenly, the command pulses from QD75 are output as shown in the
figure below.
Forward run command
Reverse run command
The t1 and t2 are calculated using the following expressions, where a command frequency is f (pps).
t1 = 1/2 f (s) t2 = 1/f (s)
A time of t1 must be maintained by the drive unit for a specified period T (s).
(T depends on the drive unit specifications.)
If t1 cannot be maintained for T or longer, lower the "
(3) When a "0" is set in the "
data, the command speed of about 2 ms is reduced to 0.
When a "0" is set in the "
points in the future, change the "
nonexecutable.
(Refer to Section 9.2.20 "NOP instruction".)
(4) In the continuous path control positioning data, assure a movement distance so that the execution time with that
data is 100 ms or longer, or lower the command speed.
(b) When the operation pattern of the positioning data currently being
executed is "continuous path control: 11", and the movement amount
of the next positioning data is "0".
(c) During operation by step operation.
(Refer to Section 12.7.1 Step function".)
(d) When there is an error in the positioning data to carry out the next
operation.
[Reference axis operation]
V
Positioning data
No.2
Reference axis
Da.6
Positioning address/movement amount" of the continuous path control positioning
Da.6
Positioning address/movement amount" to increase the number of speed change
Da.2
Control system" to the "NOP instruction" to make the control
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Positioning data
Positioning data
No.1
No.2
t1
t2
Da.8
Command speed" of the positioning data.
9 - 10
MELSEC-Q
[Interpolation axis operation]
V
t
Positioning data
Positioning data
No.1
No.2
t
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