Omron TJ2-MC64 - PROGRAMMING Programming Manual page 271

Examples and tips
Caution
To make sure that the absolute position is always correct, you
must make sure that
(Pn205 + 1) . . encoder_resolution < 2
and that
(Pn205 + 1) .
Note that this is not obvious for the high-resolution encoders of the
Sigma-V motors.
Example 3
The mechanical system uses a servo motor with an 17-bit absolute encoder.
The mechanical gear ratio of the gearbox is 1:6.31. One rotation of the
pulley moves the moving part on the belt 320 mm. The total length of the
belt, and therefore the total moving range of the motion part, is 4160 mm.
The mechanical measurement units must be mm. This means that all axis
parameters and commands given to Trajexia are expressed in mm. Using
the same procedure as in example 1, the equation expressing the
relationship between user units and encoder counts is:
17
.
Pn202
2 encoder_counts
UNITS =
.
Pn203 1 motor_revolution
17
.
2 6.31 encoder_counts
320 mm
Therefore:
17
.
Pn202 2 6.31
UNITS =
Pn203 320
One solution is:
PROGRAMMING MANUAL
32
Pn203
32
.
encoder_resolution < 2
Pn202
. .
6.31 motor_revolution 1 pulley_revolution
.
1 pulley_revolution 320mm
17
2 631 631 631
12 9
12
= = 2 = 2 = 2
5 3
.
2 1000 8.125 2 125
M
17-bit absolute 1:6.31
encoder Gear
=
631
125
fig. 21
Total length (perimeter) of belt: 4160
r
r = 320/(2*PI)
1 turn = 320mm move
265