4. PARAMETERS FOR POSITIONING CONTROL
4
−
4
(e) The number of pulses per revolution, travel value per revolution, and unit
magnification for the example configuration shown here are calculated
below.
1
25
10[mm]
Servo motor
Gear ratio
=
Z
1
: Z
2
=
1 : 25
Number of feedback pulses=8192[PLS/rev]
Ball screw pitch=10[mm]
1) Travel value per feedback pulse
Z
1
1
∆
S = 10 [mm]
×
Z
2
= 10 [mm]
×
25
∆
S
10 [mm]
∆
l =
P
f
=
25
×
8192
=0.000049[mm] ....
→∆
l = 0.0001[mm]
2) Unit magnification (A
M
)
Since
∆
l is 0.0001[mm], the unit magnification (A
M
) is "1".
3) Travel distance per revolution (A
L
)
10 [mm]
×
1
A
L
=
25
= 0.4 [mm] = 400.0 [
µ
m]
4) Number of pulses per revolution (A
P
)
A
P
= 8192 [PLS/rev] ... fixed according to the encoder model.
(2) Setting method 2
If A
L
cannot be set by using setting method 1, calculate the numerator and
denominator of the electronic gear, and set A
P
as the numerator and A
L
×
A
M
as the denominator.
Servo system CPU
Electronic gear
Amplifier
Motor
Command
M
A
P
A
L
×
A
M
The electronic gear is represented by the following relational expression.
Number of feedback pulses (Pf)
Electronic gear =
Travel value per revolution (
∆
S)
Number of pulses per revolution (A
P
)
=
Travel value per motor revolution (A
L
)
×
unit magnification (A
M
)
Example: With the example configuration shown above, and under the following
conditions;
Gear ratio = Z
1
: Z
2
= 1 : 39
Ball screw pitch = 25.4 [mm] =25.4
×
1000=25400.0 [
µ
m]
25.4 [mm]
A
L
=
29
= 0.65128205 [mm]
= 651.28205 [
µ
m]
and A
L
cannot be set, calculate as follows....
Electronic gear
P
f
8192 [PLS]
319448 ..........A
P
=
∆
S
×
1
=
25400 ..........A
L
×
A
M
25400.0 [
µ
m]
×
39
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