sh030106u.pdf - 第527页
16. FULLY CLOSE D L OOP SYS TEM 16 - 2 The foll owing tabl e shows t he functio ns of each con trol mod e. Control Desc ription Semi cl osed loop control Feature Pos ition is controlled according to the servo motor-si d …
16. FULLY CLOSED LOOP SYSTEM
16 - 1
16. FULLY CLOSED LOOP SYSTEM
POINT
The fully closed loop system is available for the servo amplifiers of which
software version is A3 or later.
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 control mode.
When fully closed loop control system is configured with MR-J4-_B_ servo
amplifier, the following restrictions apply. However, these restrictions will not be
applied for MR-J4-_B_-RJ servo amplifiers.
A/B/Z-phase differential output type encoder cannot be used.
The load-side encoder and servo motor encoder is compatible with only the
two-wire type. The four-wire type load-side encoder and servo motor encoder
cannot be used.
When you use the KG-KR and HG-MR series for driving and load-side
encoder, the optional four-wire type encoder cables (MR-EKCBL30M-L, MR-
EKCBL30M-H, MR-EKCBL40M-H, and MR-EKCBL50M-H) cannot be used.
When an encoder cable of 30 m to 50 m is needed, fabricate a two-wire type
encoder cable according to app. 8.
The synchronous encoder Q171ENC-W8 can be used with servo amplifiers with
software version A8 or later.
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.
Servo motor-side cumulative
feedback pulses
(load-side encoder resolution unit)
(Servo motor side)
Droop pulses
(Servo motor side)
Cumulative
feedback pulses
Load-side
droop pulses
Cumulative load-side
feedback pulses
Fully closed loop
dual feedback
filter
([Pr. PE08])
(Note 2)
FBD
Servo motor
Linear encoder
Controller
(Note 1, 2)
Fully closed loop selection
([Pr. PE01] and [Pr. PE08])
+
-
FBN
S
+
-
Encoder pulse setting
([Pr. PA15], [Pr. PA16]
and [Pr. PC03])
Fully closed loop control
error detection function
selection ([Pr. PE03])
+
-
+
+
-
+
-
+
Control
Monitor
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], full
y
closed loop control is alwa
y
s performed.
16. FULLY CLOSED LOOP SYSTEM
16 - 2
The following table shows the functions of each control mode.
Control Description
Semi closed loop control
Feature Position is controlled according to the servo motor-side data.
Advantage
Since this control is insusceptible to machine influence (such as machine resonance),
the gains of the servo amplifier can be raised and the settling time shortened.
Disadvantage
If the servo motor side is at a stop, the side may be vibrating or the load-side accuracy
not obtained.
Dual feedback control
Feature Position is controlled according to the servo motor-side data and load-side data.
Advantage
Control is performed according to the servo motor-side data during operation, and
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.
Fully closed loop control
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.
Disadvantage
Since this control is susceptible to machine resonance or other influences, the gains
of the servo amplifier may not rise.
16. FULLY CLOSED LOOP SYSTEM
16 - 3
16.1.2 Selecting procedure of control mode
(1) Control mode configuration
In this servo, a semi closed loop system or fully closed loop system can be selected as a control system.
In addition, on the fully closed loop system, the semi closed loop control, fully closed loop control and
dual feedback control can be selected by the [Pr. PE08] settings.
"4500"
"1 to 4499"
"0"
Fully closed loop
function selection 1
([Pr. PE01])
Operation mode selection
([Pr. PA01])
"_ _ _ 1"
"_ _ _ 0"
Fully closed
loop control
Semi closed
loop control
(Note 1)
"_ _ 0 _"
Servo amplifier
"_ _ 1 _"
(Refer to section 16.3.1 (2) (a))
Semi closed/fully closed switching command
(Refer to the controller user's manual.)
OFF
ON
(Refer to section 16.3.1 (2) (b))
Dual feedback
control
Semi closed
loop control
(Note 2)
Fully closed loop system
Fully closed loop
dual feedback filter
([Pr. PE08])
Semi closed loop system
Note 1. Use the servo motor encoder unit for the command unit. Use the servo motor-side information for the alarm determination.
2.
Use the load-side encoder information for the command unit. When [Pr. PE08 Fully closed loop dual feedback filter] is set to
"0", the load-side information is used for determining alarms such as error excessive.
When the semi closed/fully closed
switching command is turned off, the servo motor-side information is used for determining alarms such as error excessive.
(2) Dual feedback filter equivalent block diagram
A dual feedback filter equivalent block diagram on the dual feedback control is shown below.
Servo motor during a stop
(0 to ω)
Fully closed loop
control
In operation (ω or more)
Semi closed loop
control
Semi closed
loop control
Fully closed
loop control
+
+
+
-
Dual feedback filter
Servo motor
Linear encoder
Position
control unit
High-pass
filter
Low-pass
filter
ω (Note)
Frequency [rad/s]
Operation status
Control status
Note. "ω" (a dual feedback filter band) is set by [Pr. PE08].