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16. FULLY CLOSED LOOP SYSTEM
16. FULLY CLOSED LOOP SYSTEM
16.1 Functions and configuration
16.1.1 Function block diagram
A fully closed loop control block diagram is shown below. The fully closed loop system is controlled in the
load-side encoder unit.
Controller
(Servo motor side)
Droop pulses
(Servo motor side)
Cumulative
feedback pulses
Load-side
droop pulses
Cumulative load-side
feedback pulses
Note 1. Switching between semi closed loop control and fully closed loop control can be performed by changing the setting of [Pr.
PE01].
When semi closed loop control is selected, a control is always performed on the bases of the position data of the servo
motor encoder independently of whether the servo motor is at a stop or running.
2. When the fully closed loop system is enabled in [Pr. PE01], dual feedback control in which the servo motor feedback signal
and load-side encoder feedback signal are combined by the dual feedback filter in [Pr. PE08] is performed.
In this case, fully closed loop control is performed when the servo motor is at a stop, and semi closed loop control is
performed when the servo motor is operating to improve control performance. When "4500" is set as the filter value of [Pr.
PE08 Dual feedback filter], fully closed loop control is always performed.
The following table shows the functions of each control mode.
Control
Semi closed loop control
Dual feedback control
Fully closed loop control
POINT
When fully closed loop control system is used with this servo amplifier, "Linear
Encoder Instruction Manual" is needed.
Fully closed loop control system is available with position mode.
+
-
Servo motor-side cumulative
+
feedback pulses
+
(load-side encoder resolution unit)
-
+
Fully closed loop
dual feedback
filter
+
([Pr. PE08])
(Note 2)
-
(Note 1, 2)
Fully closed loop selection
([Pr. PE01] and [Pr. PE08])
Control
Monitor
Feature
Position is controlled according to the servo motor-side data.
Since this control is insusceptible to machine influence (such as machine resonance),
Advantage
the gains of the servo amplifier can be raised and the settling time shortened.
If the servo motor side is at a stop, the side may be vibrating or the load-side accuracy
Disadvantage
not obtained.
Feature
Position is controlled according to the servo motor-side data and load-side data.
Control is performed according to the servo motor-side data during operation, and
Advantage
according to the load side-data at a stop in sequence to raise the gains during
operation and shorten the settling time. A stop is made with the load-side accuracy.
Feature
Position is controlled according to the load-side data.
Advantage
The load-side accuracy is obtained not only at a stop but also during operation.
Since this control is susceptible to machine resonance or other influences, the gains
Disadvantage
of the servo amplifier may not rise.
+
-
S
FBN
FBD
-
+
Load-side feedback pulses
Description
16 - 1
Servo motor
Linear encoder
Encoder pulse setting
([Pr. PA15], [Pr. PA16]
and [Pr. PC03])
Fully closed loop control
error detection function
selection ([Pr. PE03])
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