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Description on Dividing/Multiplier Ratio
Relation between Positional Resolution/Moving Speed and Command Dividing Multiplier Ratio
Pulse row position
command
Distance: P1 [P]
Traveling speed: F [PPS]
As an example of a machine, we describe a ball screw driving system below:
When lead of a ball screw is L [mm], actual distance of a ball screw M [mm] with respect to the distance command
PI [P] is expressed with formula (1) below:
M = P1 x (D/E) x (1/R) x L ................................. (1)
Therefore, position resolution (distance DM per command pulse) is expressed by the following formula (2):
∆ ∆ ∆ ∆ ∆ M = (D/E) x (1/R) x L ....................................... (2)
Through transformation of formula (2), a command dividing multiplier ratio D is determined by the formula (3):
D = (∆ ∆ ∆ ∆ ∆ M x E x R)/L ............................................ (3)
In addition, actual traveling speed V [mm/s] of a ball screw with respect to traveling speed command F [PPS] is
expressed by formula (4), and the corresponding motor rotation speed N is determined by formula (5):
V = F x (D/E) x (1/R) x L ................................... (4)
N = F x (D/E) x 60 ............................................. (5)
Through transformation of formula (5), a command dividing multiplier ratio D is determined by the formula (6):
D = (N x E)/(F x 60) ........................................... (6)
<Remarks>
1. Set the positional resolution (∆M) at approx. 1/5 to 1/10 of the positioning accuracy (∆ ε ), in view of mechanical
errors.
2. Set a value from 1 to 10000 to Pr46 and Pr4B.
3. You can set any value depending on numerator and denominator settings. However, if you specify an extreme
dividing/multiplier ratio, we cannot guarantee proper operation of the motor. We recommend that you set the
dividing/multiplier ratio in the range of 1/50 to 20 times.
4.
n
2
Decimal
0
2
1
1
2
2
2
2
4
3
2
8
2
4
16
5
2
32
2
6
64
7
2
128
8
2
256
9
2
512
10
2
1024
2
11
2048
12
2
4096
2
13
8192
14
2
16384
2
15
32768
2
16
65536
17
2
131072
Servo driver
Command dividing multiplier ratio
Pr4A
Pr46 x 2
D =
Pr4B
Example of driving ball screw using the servo motor
Rotation speed: N [r/min]
Number of encoder pulses E [P/r]
10000 = (phase A/B 2500 [P/r] x 4)
178
Servo
Gear
Machine
motor
Reduction ratio: R
Encoder
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