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Introduction to Electro-hydraulic Proportional and Servo Valves
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Servo ValvesWith either Mechanical or Electrical Feedback (spool position).
Servo Performance, Closed Loop Valves with Spool Position Feedback
NFPA MountingWith Spool Position Feedback
NFPA MountingWithout Spool Position Feedback
Mobile bankable Style, Threaded Cartrdige Style
BDs’DYs’SEs’
D*FPD*FHsD*1FH
D*FXs’D*FWs, D*FTs’Pulsar VP, VPLs.
Parker Models
Closed Loop Position & Force
Closed Loop Position & Force
Low End Closed Loop Position
Open Loop ControlApplications
None1000…3000 PSI1000…2000 PSIOperating Pressures Limits (Drop across metering edge).
Zero OverlapZero OverlapOverlap 5…20%Center Lap Condition
100…200 Hz50...150 Hz10….70 Hz10…50 Hz< 10 HzFrequency Response
0.1…..0.5%0.1….5%0.03…..1%3…7%3…..7%Hysteresis
Torque Motor Pilot ControlBalance PSI spool Control
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electro-Hydraulic Pilot, Mechanical (spring) Return
Mechanical Construction (spool shift)
ServoValves
Proportional Valves
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Meter Out Circuit
Free flow into the “cap” endMetered Flow out the “head”end.
PT T
A B
P to A B to T
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Meter Out Circuit
Free flow into the “cap” endMetered Flow out the “head”end.
PT T
A B
P to BA to T
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Electrohydraulic Valves
PT T
Shift Spool slightly to create metering Orifice
P to A B to T
A B
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Servo ValvesWith either Mechanical or Electrical Feedback (spool position).
Servo Performance, Closed Loop Valves with Spool Position Feedback
NFPA MountingWith Spool Position Feedback
NFPA MountingWithout Spool Position Feedback
Mobile bankable Style, Threaded Cartridge Style
BDs’DYs’SEs’
D*FPD*FHsD*1FH
D*FXs’D*FWs, D*FTs’Pulsar VP, VPLs.
Parker Models
Closed Loop Position & Force
Closed Loop Position & Force
Low End Closed Loop Position
Open Loop ControlApplications
None1000…3000 PSI1000…2000 PSIOperating Pressures Limits (Drop across metering edge).
Zero OverlapZero OverlapOverlap 5…20%Center Lap Condition
100…200 Hz50...150 Hz10….70 Hz10…50 Hz< 10 HzFrequency Response
0.1…..0.5%0.1….5%0.03…..1%3…7%3…..7%Hysteresis
Torque Motor Pilot ControlBalance PSI spool Control
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electro-Hydraulic Pilot, Mechanical (spring) Return
Mechanical Construction (spool shift)
ServoValves
Proportional Valves
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1C2C
PT
Limiter
Compensator
Sectional Valves Sectional Valves VPL Series VPL Series
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Optional L.S. Port
C2 Pressure Limiter
Flow Limiters
Anti-Cav. CheckCyl. ReliefPulsar Solenoid
Manual Override
Individual Compensator
C1 Pressure Limiter
Sectional Valves Sectional Valves VPL Series VPL Series
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Sectional Valves Sectional Valves VPL Series VPL Series (C1 Energized)
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VPL Main Spool
8 Flow Rates (1.3, 2.5, 4, 7, 11, 17, 24, 30 GPM)
Centering Spring
Meter-In Lands
Meter-Out Lands
OCM
VOC
CC
200 or 350 PSI
Detent & Friction-Lock also Available
SpoolMarking
Ex. 524
RegenativeOptions
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Compensation, VPL Series
• Pressure compensation maintains a constant flow regardless of pump pressure, load pressure, or any other load in the system
• This means when running multiple sections at the same time, there will be no change in speed
Standard Spool / Springs for complete flow range
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VPL Compensator Components
3 Sizes of Shims
(.003” .008” .025”)
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Servo ValvesWith either Mechanical or Electrical Feedback (spool position).
Servo Performance, Closed Loop Valves with Spool Position Feedback
NFPA MountingWith Spool Position Feedback
NFPA MountingWithout Spool Position Feedback
Mobile bankable Style, Threaded Cartridge Style
BDs’DYs’SEs’
D*FPD*FHsD*1FH
D*FXs’D*FWs, D*FTs’Pulsar VP, VPLs.
Parker Models
Closed Loop Position & Force
Closed Loop Position & Force
Low End Closed Loop Position
Open Loop ControlApplications
None1000…3000 PSI1000…2000 PSIOperating Pressures Limits (Drop across metering edge).
Zero OverlapZero OverlapOverlap 5…20%Center Lap Condition
100…200 Hz50...150 Hz10….70 Hz10…50 Hz< 10 HzFrequency Response
0.1…..0.5%0.1….5%0.03…..1%3…7%3…..7%Hysteresis
Torque Motor Pilot ControlBalance PSI spool Control
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electro-Hydraulic Pilot, Mechanical (spring) Return
Mechanical Construction (spool shift)
ServoValves
Proportional Valves
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How does it Work? (No Spool Feedback)
“Command Signal” based upon a % of Maximum. Typically 0 to +/- 10 VDC. Amplifier converts Voltage (Command) into proportional Current (Typically
0..2.1 Amps). Variable DC current into solenoid assembly produces Electromagnetic Force, proportional to current applied. By matching Opposition Spring Force to Solenoid Force, Proportional Spool Movement is obtained.
Solenoid “A”
Solenoid “B”
“Integrated Electronics”
(PWD Amplifier)
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WindingWinding
Plunger Plunger (armature)(armature)
Push pinPush pin
FrameFrame
How does it Work? Proportional Solenoid Construction
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How does it Work? Solenoid Operation
.
.5 VDC 50%
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C-Notch Spool
V-Notch Spool
Proportional Valve Spool Designs
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0102030405060708090
100
0 20 40 60 8 100SPOOL SHIFT, %
FLO
W A
RE
A%
0102030405060708090
100
0 20 40 60 8 100SPOOL SHIFT, %
FLO
W A
RE
A%
P-A-B-T = 145 PSI
P-A-B-T = 145 PSI
Proportional Valve Spool Designs
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V-Notch - Bleed Center
bleed notch
primary metering
notch
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Proportional Valve DeadbandPs
A B
T T
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Mechanical Spool Overlap (Deadband)
+ Q
I+-
Positive Overlap + Spring Force
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Deadband Eliminator
-+
ΩK100
Vout
inV -+
ΩK100
ΩK100
-+
ΩK100
DBE+
ΩK100
DBE−
ΩK100
CCV+ CCV−
s−s+
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DeadbandCompensation
+ Q
I+-
Deadband Compensation
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Deadband Over Compensated
+ Q
I+-
Deadband Compensation
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Valve Drivers (Open Loop) On BoardIntegrated Electronics
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Ramp Pots
Max Pots
MIN Pots
Valve Drivers (Open Loop) On BoardIntegrated Electronics (Pot adjustments)
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Digital Onboard Electronics
D1FB*0 OBE
Valve Drivers (Open Loop) On BoardIntegrated Electronics (PC Adjustments)
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Deadband Eliminator P to A flow PathPs
A B
T T
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Deadband Eliminator (P to B flow Path)Ps
A B
T T
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Servo ValvesWith either Mechanical or Electrical Feedback (spool position).
Servo Performance, Closed Loop Valves with Spool Position Feedback
NFPA MountingWith Spool Position Feedback
NFPA MountingWithout Spool Position Feedback
Mobile bankable Style, Threaded Cartrdige Style
BDs’DYs’SEs’
D*FHD*FMsD*1FH
D*FXs’D*FWs, D*FTs’Pulsar VP, VPLs. DF**, ERVs
Parker Models
Closed Loop Position & Force
Closed Loop Position & Force
Low End Closed Loop Position
Open Loop ControlApplications
None1000…3000 PSI1000…2000 PSIOperating Pressures Limits (Drop across metering edge).
Zero OverlapZero OverlapOverlap 5…20%Center Lap Condition
100…200 Hz50...150 Hz10….70 Hz10…50 Hz< 10 HzFrequency Response
0.1…..0.5%0.1….5%0.03…..1%3…7%3…..7%Hysteresis
Torque Motor Pilot ControlBalance PSI spool Control
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electro-Hydraulic Pilot, Mechanical (spring) Return
Mechanical Construction (spool shift)
ServoValvesProportional Valves
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Spool Feedback, How does it Work?
Solenoid “A”Solenoid “B”
Spool Position LVDT “Integrated Electronics”
(PWD Amplifier)
•Same basic operation as non-feedback valves, but “outcome” is measured and corrected to match desired result. •“Closing the Loop”.
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Spool Feedback DeviceLinear Variable Differential Transformer
Primary
Secondary Secondary
Oscillator
Demodulator
Input
Output
Core
V DC
V DC
Spool
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L.V.D.T.s
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LVDT
CMD + Error I F
XFB -
A
Disturbances
adj
Spool Feedback Devices(Electrical Schematic-Integrated
Electronics)
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CommandSignal
u s
Valve position feedback
Force
Internal Closed Loop
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Sample Application
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Kv Sizing
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Non-Symmetrical Spools
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Sample Application, Number 2
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(P-A-B-T = 145 PSI)
-10
-7.5
-5
-2.5
0
2.5
5
7.5
10
-10 -7.5 -5 -2.5 0 2.5 5 7.5 10
Valve Command, Volts
Flow
Rat
e, G
PM
Non-Symmetrical Spools
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Common Procedure
The manufacturer can choose to take a standard 10gpm valve with normally 4 notches on each land and only cut two notches in the land that will be connected to the small area of the cylinder.
3 notches instead of 44 notches instead of 62 notches instead of 6…
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Non-symmetrical Spools
holes7.1
holes85.holes7.1
holes85.
SPA B
P T
A B
T
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Sample Application No. 2 with Non-Symmetrical Spool
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Flow
X∆
Flow Force Effects Proportional Valves
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Flow Force Performance
Operating Limits Curves show ValvePerformance over entire Pressure Range
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Servo ValvesWith either Mechanical or Electrical Feedback (spool position).
Servo Performance, Closed Loop Valves with Spool Position Feedback
NFPA MountingWith Spool Position Feedback
NFPA MountingWithout Spool Position Feedback
Mobile bankable Style, Threaded Cartrdige Style
BDs’DYs’SEs’
D*FHD*FMsD*1FH
D*FXs’D*FWs, D*FTs’Pulsar VP, VPLs. DF**, ERVs
Parker Models
Closed Loop Position & Force
Closed Loop Position & Force
Low End Closed Loop Position
Open Loop ControlApplications
None1000…3000 PSI1000…2000 PSIOperating Pressures Limits (Drop across metering edge).
Zero OverlapZero OverlapOverlap 5…20%Center Lap Condition
100…200 Hz50...150 Hz10….70 Hz10…50 Hz< 10 HzFrequency Response
0.1…..0.5%0.1….5%0.03…..1%3…7%3…..7%Hysteresis
Torque Motor Pilot ControlBalance PSI spool Control
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electro-Hydraulic Pilot, Mechanical (spring) Return
Mechanical Construction (spool shift)
ServoValvesProportional Valves
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D1FP (NG6) valve as pilot valve for D*1FP integrated driveelectronics
Voice Coil Drive VCD®
valve body
spool-sleeve assembly
spring assemblyfail-safe position
VCD®…Milestone for High Performance Valves
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Parker Voice Coil Drive (VCD®) technology for highest precision
permanentmagnet
coil
carriage housing
integrated feedback system
pushpin
VCD®…Milestone for High Performance Valves
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VCD® principle, moved coil in magnetic field
Fo = B . I . l−Ι
-Fo ΒX
ΙΙ
Fo
B = magnetic flux densityI = electrical currentl = wire length (winding)
N S
winding
permanent magnet
iron (magnetic)
non-magnetic material
X
VCD®…Milestone for High Performance Valves
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Characteristics of force in comparison
F[N]
x [mm]
F [N]
x [mm]0 0conventional solenoidforce dependent of stroke
VCD®…Milestone for High Performance Valves
Voice Coil Driveforce independent of stroke
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Ps
A B
T T
HousingSleeve
Servo Solenoid/Voice Coil Valves
No Deadband“Line to Line” LapOr “Axis Cut”
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Spool and Sleeve Arrangement
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Spool Lap Conditions
(Positive) Overlap
Zerolap
(Negative) Underlap
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Spool Lap Conditions(Positive) Overlap Zerolap
U = 40% U = 40%
U = 20% U = 20%
U = 0% U = 0%
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Flow windows•Standard Symmetrical Laps
•“Knick Servo Cuts”
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Servo ValvesWith either Mechanical or Electrical Feedback (spool position).
Servo Performance, Closed Loop Valves with Spool Position Feedback
NFPA MountingWith Spool Position Feedback
NFPA MountingWithout Spool Position Feedback
Mobile bankable Style, Threaded Cartrdige Style
BDs’DYs’SEs’
D*FHD*FMsD*1FH
D*FXs’D*FWs, D*FTs’Pulsar VP, VPLs. DF**, ERVs
Parker Models
Closed Loop Position & Force
Closed Loop Position & Force
Low End Closed Loop Position
Open Loop ControlApplications
None1000…3000 PSI1000…2000 PSIOperating Pressures Limits (Drop across metering edge).
Zero OverlapZero OverlapOverlap 5…20%Center Lap Condition
100…200 Hz50...150 Hz10….70 Hz10…50 Hz< 10 HzFrequency Response
0.1…..0.5%0.1….5%0.03…..1%3…7%3…..7%Hysteresis
Torque Motor Pilot ControlBalance PSI spool Control
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electro-Hydraulic Pilot, Mechanical (spring) Return
Mechanical Construction (spool shift)
ServoValves
Proportional Valves
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Servo Valve – Double Flapper Design
Torque Motor
Spool & SleeveAssembly
Feedback Spring
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Servo Valve – Double Flapper Design
Flexure Tube
N
S
N
S
FrameCoil Coil
Flapper
Armature
Feedback Springand Ball/Ruby
Nozzle
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N
S
N
S
PPP P
RR
A B
Servo Valve - Principles of OperationValve at “Null”
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N
S
N
S
PP P
R
A B
P R
(-)
(+)
Servo Valve - Principles of OperationValve With Current Applied
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Flow Forces Not an Issue with Servo Valves
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Servo ‘s Performances
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Proportional Directional Valve
u s
Proportional Valve with Spool Feedback
u s
Servo Performance Proportional Valve
Symbology
Servo Valve
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Terminologies
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80% rise
2% command
40% pressure change1% command change
Pressure Gain
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Hysteresis%
of F
ull O
pen
Flow
Input Signal
Mechanical Spool Overlap: the Deadband Increasing Flow
from Valve
Decreasing Flowfrom Valve
Hysteresis
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1 2 3 4 5 6 7 8 9 10
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Repeatability%
of F
ull O
pen
Flow
Input Signal
Increasing Flow Only
Repeatability
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1 2 3 4 5 6 7 8 9 10
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Valve Frequency
Two methods: frequency response, step response (we’ll use frequency response)
offsetbias
CMD
Q
Bias or one sided
CMD
Q
Thru center
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CMD
FB
0° Phase Lag
Valve
90° Phase Lag
The input frequency which creates a phase lag of 90° is the defining characteristics of a valve and is referred to as bandwidth
90° Phase Lag = ¼ cycle
Valve Frequency Response
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Frequency Response
• To measure the response of a control valve, a sinusoidal varying input signal is applied, effectively switching the valve from one working position to the other
• At a very low frequency the valve is able to follow the demand signal closely
• As the frequency increases the valve becomes less able to follow the input signal precisely
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Frequency Response
• The output starts to lag behind the input, then the valve is not able to reach the maximum output position before the input signal reverses
• The lag between the input and output is known as phase lag
• The reduced output apparent at higher frequencies is known as attenuation
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Valve Frequency
Frequency response (sine wave) to make catalog data
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Servo ValvesWith either Mechanical or Electrical Feedback (spool position).
Servo Performance, Closed Loop Valves with Spool Position Feedback
NFPA MountingWith Spool Position Feedback
NFPA MountingWithout Spool Position Feedback
Mobile bankable Style, Threaded Cartrdige Style
BDs’DYs’SEs’
D*FHD*FMsD*1FH
D*FXs’D*FWs, D*FTs’Pulsar VP, VPLs. DF**, ERVs
Parker Models
Closed Loop Position & Force
Closed Loop Position & Force
Low End Closed Loop Position
Open Loop ControlApplications
None1000…3000 PSI1000…2000 PSIOperating Pressures Limits (Drop across metering edge).
Zero OverlapZero OverlapOverlap 5…20%Center Lap Condition
100…200 Hz50...150 Hz10….70 Hz10…50 Hz< 10 HzFrequency Response
0.1…..0.5%0.1….5%0.03…..1%3…7%3…..7%Hysteresis
Torque Motor Pilot ControlBalance PSI spool Control
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electro-Hydraulic Pilot, Mechanical (spring) Return
Mechanical Construction (spool shift)
ServoValves
Proportional Valves
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Actuators
Linear Motion•Position Control
•Velocity
•Force
Rotary Motion•Position Control (Angle)
•Velocity
•Torque
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Actuators Linear Feedback TypesMagnetostrictive (M.D.T.s)
Pulse is sent down waveguide, when hits magnet, “twist” is sensed. Time between pulse sent to twist measured dictates distance. Approximately 9 microseconds = 1”
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Actuators Linear Feedback TypesMagnetostrictive (M.D.T.s)
Analog Outputs
Digital Outputs
SSI Output
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Valve Drivers and Motion Controllers
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Valve Drivers (Open Loop) Off Board Elec
• Converts “Command Signal” to PWM signal to drive Coil.
• Digital Versions (shown) incorporate a microprocessor with numeric settings.
• Analog Versions incorporate Trim pots for
Optional Set point card
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Valve Drivers (Open Loop) Off Board Elec
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Valve Drivers (Closed Loop)
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Valve Drivers (Closed Loop)
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Motion Controllers
Actual Position
Position Error Proportional
G ain
Accumulator (Inte grator)
∆ Error (Diffe re ntiator)
Integral G ain
Diffe re ntial G ain
Fee d Forward
Forward
Position ∆ (Ve locity)
Σ
Σ
+ -
DriveO utput
Targe t G e nerator
Targe t Position
Command Proce ssor
Ladde r Logic RmcWin
Acce l Fe ed Velocity ∆ (Acce leration)
De adband Eliminator
Velocity
Position
“Generate A Target Profile”
PLC
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Velocity and Accel Feed ForwardActual
Position
Position Error Proportional
G ain
Accumulator (Inte grator)
∆ Error (Diffe re ntiator)
Integral G ain
Diffe re ntial G ain
Fee d Forward
Forward
Position ∆ (Ve locity)
Σ
Σ
+ -
DriveO utput
Targe t G e nerator
Targe t Position
Command Proce ssor
Ladde r Logic RmcWin
Acce l Fe ed Velocity ∆ (Acce leration)
De adband Eliminator
Target Position Target Velocity Velocity FFWD Drive
Target Acceleration Accel FFWD Drive
DRIVE
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Proportional Gain ONLY
0.625” Following Error
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Feed Forward Adjust “F” Cmd
Correct drive for constant velocity portion of move.
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Position Error during Accel/Decel
Accel FFWD corrects for error during Accel/Decel
Boost
Brake
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Proper Velocity and Accel Feed forwards.
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Real Time Plot Data
ActualPosition
ActualVelocity
Voltage toServo Valve
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Closed Loop Position System
Reservoir
Metal Tubing
MDT
Magnet
Pump
Valve
Control DriveSignal from theMotion Control
Module
Manifold
Position Transducers
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Principle of Operation Force Balance
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FbFb==PbPb*Area b*Area bFaFa=Pa*Area a=Pa*Area a
Balanced Force
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Principle of operation (cont)
Valve null = net forces across cylinder equal
zero
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Closed Loop Force Control
Reservoir
Metal Tubing
MDT
Magnet
Pump
Valve
Control DriveSignal from theMotion Control
Module
Manifold
Differential Pressure Transducers
Load Cellor
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FbFb==PbPb*Area b*Area bFaFa=Pa*Area a=Pa*Area a
Balanced Force
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Force Control
In Position Control
Start Force Control
MaintainedForce for Xamount of Time
Increased ForceWith differentRamp Rate
Decompression
Back into Position Control
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Thank you!
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