Fully-Closed Control; Outline Of Operation - Omron OMNUC G5 Series User Manual

6-6 Fully-closed Control

An externally provided encoder is used to directly detect the position of the control target and
feedback the detected machine position to perform position control. This way, controls can be
performed without being affected by ball screw error, temperature changes, etc. You can
achieve highly accurate positioning by configuring a fully-closed control system.

Outline of Operation

Host Controller with
EtherCAT Communications
Position Control Unit
CJ1W-NC@81
[command units]
Position actual value
Reference
If the Gear ratio (6091-01 and 6091-02 hex) is 1:1, 1 command unit from the Target position (607A
hex) is equivalent to a movement of 1 external encoder pulse.
Example for an External Encoder with a Resolution of 0.1 µm
Gear ratio (6091-01 and 6091-02 hex) of 1:1:
Gear ratio (6091-01 and 6091-02 hex) of 1:2:
Set the External Feedback Pulse Dividing Ratio (3324 and 3325 hex) according to External
Feedback Pulse Dividing Ratio Setting (3324 Hex, 3325 Hex) on page 6-16.
Set the Hybrid Following Error Counter Overflow Level (3328 hex) and Hybrid Following Error
Counter Reset (3329 hex) according to Hybrid Error Setting (3328 Hex, 3329 Hex) on page 6-17
OMNUC G5-series AC Servomotors and Servo Drives User's Manual (with Built-in EtherCAT Communications)
R88D-KN@-ECT-R
Target position
Electronic gear
(607A hex)
forward conversion
6091h-01h
------
6091h-02h
External feedback
pulse dividing ratio
Internal
circuits
Electronic gear
(6064 hex)
reverse conversion
[command units]
6091h-02h
------
6091h-01h
The external encoder executes positioning for 10 µm when 100 command units are
applied as the Target position (607A hex).
100 command units × 1:1 (Gear ratio) × 0.1 µm = 10 µm
Here, 100 command units are returned to the host controller as the Position actual value
(6064 hex).
The external encoder executes positioning for 10 µm when 200 command units are
applied as the Target position (607A hex).
200 command units × 1:2 (Gear ratio) × 0.1 µm = 10 µm
Here, 200 command units are returned to the host controller as the Position actual value
(6064 hex).

6-6 Fully-closed Control

Servo Drive
Motor
current
3324h
------
3325h
Position actual internal
value (6063 hex)
[external encoder units]
Motor Load
Encoder
External
encoder
6-12
6