Mitsubishi Electric CR750-Q Instruction Manual page 129

<Precautions on the posture of position data in a pallet definition>
CAUTION
*Explanation
At a position where a posture component (A, B and C) reaches 180 degrees, the component value can
become either +180 degrees or -180 degrees even if the posture is the same. This is due to internal opera-
tion errors, and there is no consistency in which sign is employed.
If this position is used for the start point, end points A and B or diagonal point of the pallet definition and the
same posture component values include both +180 degrees and -180 degrees, the hand will rotate and
move in unexpected ways because the pallet gird positions are calculated by dividing the distance between
-180 degrees and +180 degrees.
Whether a posture component is +180 degrees or -180 degrees, the posture will be the same. Use the
same sign, either + or -, consistently for position data used to define a pallet.
Note also that similar phenomena can occur if posture components are close to +/-180 degrees (e.g., +179
degrees and -179 degrees) as well, if different signs are used. In this case, add or subtract 360 degrees to/
from the posture components and correct the values such that the sign becomes the same. (For example,
to change the sign of -179 degrees to +, add 360 degrees and correct the value to +181 degrees.)
"• Program example 1"
diagonal point (P5) are adjusted according to the start point (P2) when the hand direction is the same in all
grid points of a pallet (values of the A, B and C axes are identical) (line numbers 10 to 90).
ple 2" shows an example where values are corrected to have the same sign as the start point (P2) when the
posture components of a pallet definition position are close to +/-180 degrees and the C-axis values of the
end points (P3 and P4) and diagonal point (P5) are either less than -178 degrees or greater than +178
degrees (line numbers 10 to 100). (+/-178 degrees are set as the threshold values of correction.) Use these
program examples as reference for cases where the pallet precision is not very high and the hand direction
thus must be corrected slightly.
*Program example
Robot movement
CAUTION
The statement examples and program examples are for a
vertical 6-axis robot.The hand advance/retrace direction
relies on the Z axis direction (+/- direction) of the tool
coordinate set for each model.
Refer to the tool coordinate system shown in "Confirma-
tion of movement" in the separate "From Robot unit setup
to maintenance", and designate the correct direction.
Please read "*Explanation"
nents (A, B and C) are approximately +/-180 degrees as the start point, end points A
and B, or the diagonal point.
shows an example where the posture components of the end points (P3 and P4) and
P1
(workpiece supply position)
*1) Specification of forward/
backward movement of the
hand
below if you use position data whose posture compo-
P4
(End point B)
13
Palletize
10
7
4
1
3 pcs.
P2
(Start point)
Pallet pattern = 2(same direction)
4MELFA-BASIC V
"• Program exam-
P5
(Diagonal point)
14 15
11 12
8 9
5 6
2 3
P3
(End point A)
MELFA-BASIC V functions 4-109