5.14 Setting Unit Systems
5.14.1 Setting the Position Reference Unit
5-43
5
Basic Functions That Requir
e Setting befor
e Operation
•
Linear Servomotors
In this example, the following machine configuration is used to move the load 10 mm. We’ll
assume that the resolution of the Serial Converter Unit is 256 and that the linear encoder pitch
is 20
μ
m.
Calculating the Settings for the Electronic Gear Ratio
Rotary Servomotors
If the gear ratio between the Servomotor shaft and the load is given as n/m, where n is the
number of load rotations for m Servomotor shaft rotations, the settings for the electronic gear
ratio can be calculated as follows:
Encoder Resolution
You can check the encoder resolution in the Servomotor model number.
For a Rotary Servomotor with an encoder resolution of 24 bits (16,777,216), Pn20E (Elec-
tronic Gear Ratio (Numerator)) is automatically set to 16 and Pn210 (Electronic Gear Ratio
(Denominator)) is automatically set to 1. Therefore, the encoder resolution will be equivalent
to 20 bits (1,048,576). Consider this when you set the position reference unit in
position user
unit
(2701 hex).
When the Electronic Gear Is Not Used
When the Electronic Gear Is Used
To move a workpiece 10 mm:
Calculate the number of revolutions.
The motor will move 6 mm for each revolution,
so 10/6 revolutions are required to move 10
mm.
Calculate the required number of reference
pulses.
One revolution is 1,048,576 pulses, therefore
10/6 × 1,048,576 = 1,747,626.66 pulses.
Input 1,747,627 pulses as the reference.
If you use reference units to
move the workpiece when one
reference unit is set to 1
μ
m,
the travel distance is 1
μ
m per
pulse.
To move the workpiece 10 mm
(10,000
μ
m), 10,000
÷
1 =
10,000 pulses, so 10,000
pulses would be input.
Calculating the number of reference pulses for each
reference is troublesome.
Calculating the number of ref-
erence pulses for each refer-
ence is not necessary.
Linear encoder
When the Electronic Gear Is Not Used
When the Electronic Gear Is Used
To move the load 10 mm:
10 × 1000
÷
20 × 256 = 128,000
pulses, so 128,000 pulses are input
as the reference.
To use reference units to move the load 10 mm:
If we set the reference unit to 1
μ
m, the travel
distance is 1
μ
m per pulse. To move the load 10
mm (10,000
μ
m), 10,000/1 = 10,000 pulses, so
10,000 pulses would be input as the reference.
Calculating the number of reference
pulses for each reference is trouble-
some.
Calculating the number of reference pulses
for each reference is not necessary.
=
=
×
B
A
Numerator
Denominator
m
n
Electronic gear ratio
Encoder resolution
Travel distance per load shaft revolution (reference units)
Information
SGM7J, SGM7A,
or SGM7G -
7
16,777,216
F
16,777,216
Code
Specification
24-bit multiturn absolute encoder
24-bit incremental encoder
Encoder Resolution
