Operation of a Servovalve in a Hydraulic Actuator - PowerPoint PPT Presentation

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Operation of a Servovalve in a Hydraulic Actuator

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Operation of a Servovalve in a Hydraulic Actuator December R. Cowen University of Illinois - UC March 6, 2002 Outline General Uses of Hydraulic Actuators Basic ... – PowerPoint PPT presentation

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Title: Operation of a Servovalve in a Hydraulic Actuator


1
Operation of a Servovalve in a Hydraulic Actuator
December R. Cowen
University of Illinois - UC
March 6, 2002
2
Outline
  • General Uses of Hydraulic Actuators
  • Basic Hydraulic System Operation
  • Servovalve Location and Components
  • Servovalve Operation

3
General Uses of Hydraulic Actuators
  • Static, Psuedodynamic, and Dynamic Testing
  • Load or Position Control

4
Basic Hydraulic System Operation
5
Servovalve Location
6
Role of Servovalve in System
Servovalve reacts to an input signal from a valve
driver or valve controller by porting hydraulic
fluid in a direction and amount determined.
7
Servovalve Components
8
Servovalve Components
  • Torque Motor
  • Two Stages of Hydraulic Regulation

9
Servovalve Components
  • Torque Motor
  • Coils
  • Upper and Lower Pole Pieces
  • Armature
  • Two Magnets

Converts input signal from a valve driver or
valve controller into a physical movement for the
armature
10
Servovalve Components
  • First Stage of Regulation
  • Two Fixed Nozzles
  • Two Variable Orifices formed by the nozzle
    openings and flapper
  • Flapper is attached to the armature and moves
    from side to side as the armature rotates. This
    controls the flow through the nozzles.
  • Armature/Flapper Assembly is supported by a
    flexure tube

Regulates the flow from the hydraulic fluid supply
11
Servovalve Components
  • Second Stage of Regulation
  • A spool that controls the hydraulic fluid flow
    to and from actuator
  • A feedback wire which provides the closed loop
    control between the armature and spool

12
Servovalve Operation
  • The control signal energizes the coils causing
    the armature to rotate.
  • The armature rotates clockwise or counter
    clockwise depending upon the polarity of the
    signal. The rate at which the armature rotates
    is dependent upon the magnitude of the signal.
  • As the armature/flapper assembly rotates it
    controls the flow of hydraulic fluid from the two
    nozzles.
  • This is an inversely proportional manner as the
    flow from one nozzle increases, the flow from the
    other decreases.

13
Servovalve Operation
  • This resultant change in flow of hydraulic fluid
    creates a differential pressure which is used to
    position the second stage spool.
  • As the spool moves in response to the
    differences in pressure, the feedback wire exerts
    an opposite torque on the armature/flapper
    assembly trying to re-center the flapper.
  • The spool will continue to move until the
    feedback wire torque equals the control signal
    torque and re-centers the flapper.
  • Now both nozzle openings are equal.

14
Servovalve Operation
  • This causes the pressure at the ends of the
    spool to equalize and then the spool will stop.
  • For any level of input control signal there will
    be a corresponding spool position dependent upon
    the magnitude and polarity of the control signal.
  • Therefore, the position of the spool controls
    the amount, rate, and duration of flow to the
    actuator.

15
Servovalve Operation
  • When the control signal decreases to zero, the
    flapper creates a pressure imbalance to the
    opposite end of the spool.
  • In response to the pressure imbalance, the spool
    moves until the pressure is equalized. The spool
    moves to a position that stops the flow of the
    hydraulic fluid to the actuator.

16
Acknowledgements
  • Greg Banas, Lab Director for NCEL
  • MTS Training Manual
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