7 Buffer Memory
7.3 Positioning Parameters
58
FX3U-1PG User's Manual
How to use an electronic gear
Some servo motors require pulse trains at 200 kHz or more (in calculation) in order to satisfy the rated
rotation speed. For example, the command pulse frequency required to operate the MR-JN Series servo
amplifier and HF-KN Series servo motor manufactured by Mitsubishi at the rated rotation speed of 3,000 rev/
min can be obtained as follows.
(Suppose that the electronic gear ratio is the initial value "1/1", the number of command input pulses per
revolution is the initial value "10,000".)
However, because the input command pulse in the open collector type servo amplifier and the pulse output
from the FX
3U-1PG is 200 kHz maximum, operation at 500,000 Hz is impossible.
In such a case, you should change the electronic gear in the servo amplifier.
The electronic gear can be obtained as follows.
The table below shows the setting of major electronic gears and pulse rates obtained by the above
calculation.
Rated rotation
speed of servo
motor
Servo amplifier Command pulse frequency (200 kHz)
Maximum input pulse
frequency
Number of command
input pulses per
revolution
Electronic gear Pulse rate
3,000 r/min
200 kHz
(open collector)
10,000 PLS/REV 5/2
4,000 PLS/REV50,000 PLS/REV 25/2
131,072 PLS/REV 4,096/125
f0 = FBP × 100 ×
×
60
N0
CMX
CDV
f0 = 10,000 ×
×1
60
3,000
f0 = 500,000 [Hz]
CMX : Electronic gear (numerator of command
pulse magnification)
CDV : Electronic gear (denominator of command
pulse magnification)
N0 : Rotation speed of servo motor [rev/min]
FBP×100 : Number of command input pulses per
revolution [PLS/REV]
f0 : Command pulse frequency [Hz]
(open collector type)
CDV
CMX
CDV
CMX
2
5
= FBP × 100 ×
×
60
N0
CDV
CMX
f0
1
= 10,000 ×
×
200,000
1
60
3,000
=
CMX : Electronic gear (numerator of command
pulse magnification)
CDV : Electronic gear (denominator of command
pulse magnification)
N0 : Rotation speed of servo motor [rev/min]
FBP×100 : Number of command input pulses per
revolution [PLS/REV]
f0 : Command pulse frequency [Hz]
(open collector type)
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