Closing the Servo Loop
Closed loop analog control of an actuator requires:
• An 'Electronic FeedBack Controller’ (EFB) is used for closing a ServoLoop.
The Br-EFB will simultaneously close four ServoLoops.
• An analog ServoValve must be used for pneumatic or hydraulic actuators.
For electronic actuators, a Brushless DC (BLDC) driver (for small three
phase DC motors) or Variable Frequency Drive (VFD) (for larger 3 phase AC
motors) is used in place of the ServoValve. In either case, it must be
capable of bidirectional control of the actuator/motor. The most common
command signal for these is +/-10 VDC. The positive or negative polarity
controls the direction or the movement, and the further away from zero, the
more the ServoValve/Motor Controller opens.
• A Position Feedback sensor. This can be a simple potentiometer or a more
complex electronic device like
(the unfortunately named) 'Sick' sensors
. The
position sensor can be built into the actuator, or mounted on its outside.
The EFB controller’s main job is to compare the requested actuator position (from
an external show control
s y s t e m , o r f r o m t h e
AutoDownload file on the
Br-EFB's µSd flash card)
with the actual position of the
actuator (as measured by
the position sensor). The
EFB Controller will then
o p e n o r c l o s e t h e
ServoValve/Motor Controller
a little or a lot (as needed) to
send the actuator towards
the requested position.
One of the unique features
of the Br-EFB is that it can
a d j u s t i t s e l f i n m a n y
applications. Once it has
done the initial adjustments
for an actuator, the Br-EFB
can divide the stroke of the
actuator into many small segments, and then continuously adjust the settings for each
ServoValve
(+/- 10
vdc Input)
Actuator
(Pneumatic or Hydraulic Cylinder)
Electronic
FeedBack
Controller
(EFB)
Position Sensor
'Position'
Command
+/- 10vdc
Command to
ServoValve
'Current'
Position
Pressure
In
Exhaust
Out
Retract
Extend
Gilderfluke & Co.• 205 South Flower Street • Burbank, California 91502 • 818/840-9484 • 800/776-5972 • fax 818/840-9485
Br-EFB Manual / May 22, 2018 3:28 PM / page 16 of 142
