Omron R88M-K - Page 350

6 Basic Control Functions
6-20
G5-series AC Servomotors and Servo Drives User’s Manual (with Built-in EtherCAT Communications)
Set the dividing ratio for the encoder resolution and external encoder resolution.
Check the number of encoder feedback pulses and the number of external encoder output pulses per
motor rotation, and set the External Feedback Pulse Dividing Numerator (3324 hex) and External
Feedback Pulse Dividing Denominator (3325 hex) the so that the following equation is true.
Precautions for Correct UsePrecautions for Correct Use
• If this divider setting is wrong, there will be error between the position calculated from encoder
pulses and the position calculated from external encoder pulses. If the movement distance is
long, this error accumulates and causes a Excessive Hybrid Deviation Error (Error No. 25.0).
• The recommended divider setting is 1/40 ≤ External Feedback Pulse Ratio ≤ 160. If the ratio is
set too small, control to the unit of 1 external feedback pulse may be disabled. On the other
hand, if the external feedback pulse ratio is increased, operating noise may increase.
z Setting Example
• Ball screw pitch: 10 mm
• External encoder resolution: 0.1 µm
• Encoder resolution: 20 bits
External Feedback Pulse Dividing Ratio Setting (3324 Hex, 3325 Hex)
Index Name Description Setting range Unit
3324 hex External
Feedback
Pulse Dividing
Numerator
Set the numerator of the external feedback
pulse divider setting. Normally, set the number
of encoder output pulses per motor rotation. If
the set value is 0, the encoder resolution is set
automatically.
0 to 1,048,576 −
3325 hex External
Feedback
Pulse Dividing
Denominator
Set the denominator of the external feedback
pulse divider setting. Normally, set the number
of external encoder output pulses per motor
rotation.
1 to 1,048,576 −
=
Encoder resolution per motor rotation [pulses]
External encoder resolution per motor rotation [pulse
s
Object 3324 hex
Object 3325 hex
Servomotor
Encoder resolution: 20 bits/rotation
10 mm
Ball screw
Ball screw pitch: 10 mm
1 rotation
External encoder
resolution: 0.1
µ
m
External Encoder Output Pulse per Motor Rotation (3325 hex
)
10 [mm]/0.1 [
µ
m/pulse] = 100,000 [pulses]
Encoder Output Pulses per Motor Rotation (3324 hex)
20 bits = 1,048,576
Object 3325 hex
Object 3324 hex
=
100000
1048576
Encoder resolution per motor rotation [pulses]
External encoder resolution per motor rotation [pulses]
=