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Introduction to Electro-hydraulic
Proportional and Servo Valves
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Servo Valves
With either
Mechanical or
Electrical
Feedback (spool
position).
Servo
Performance,
Closed Loop
Valves with Spool
Position Feedback
NFPA Mounting
With Spool
Position
Feedback
NFPA Mounting
Without Spool
Position
Feedback
Mobile bankable
Style, Threaded
Cartrdige Style
BDsDYs
SEs
D*FPD*FHs
D*1FH
D*FXsD*FWs, D*FTsPulsar VP,VPLs.
Parker Models
Closed Loop
Position & Force
Closed Loop
Position & Force
Low End Closed
Loop Position
Open Loop ControlApplications
None10003000 PSI10002000 PSIOperating
Pressures Limits
(Drop across
metering edge).
Zero OverlapZero OverlapOverlap 520%Center Lap
Condition
100200 Hz50...150 Hz10.70 Hz1050 Hz< 10 HzFrequency
Response
0.1..0.5%0.1.5%0.03..1%37%3..7%Hysteresis
Torque Motor Pilot
Control
Balance 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)
Servo
ValvesProportional 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 B
A to T
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Electrohydraulic Valves
PT T
Shift Spool slightly to createmetering Orifice
P to A
B to T
A B
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Servo Valves
With either
Mechanical or
Electrical
Feedback (spool
position).
Servo
Performance,
Closed Loop
Valves with Spool
Position Feedback
NFPA Mounting
With Spool
Position
Feedback
NFPA Mounting
Without Spool
Position
Feedback
Mobile bankable
Style, Threaded
Cartridge Style
BDsDYs
SEs
D*FPD*FHs
D*1FH
D*FXsD*FWs, D*FTsPulsar VP,VPLs.
Parker Models
Closed Loop
Position & Force
Closed Loop
Position & Force
Low End Closed
Loop Position
Open Loop ControlApplications
None10003000 PSI10002000 PSIOperating
Pressures Limits
(Drop across
metering edge).
Zero OverlapZero OverlapOverlap 520%Center Lap
Condition
100200 Hz50...150 Hz10.70 Hz1050 Hz< 10 HzFrequency
Response
0.1..0.5%0.1.5%0.03..1%37%3..7%Hysteresis
Torque Motor Pilot
Control
Balance 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)
Servo
ValvesProportional Valves
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1C2C
PT
Limiter
Compensator
Sectional ValvesSectional Valves
VPL SeriesVPL 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 ValvesSectional Valves
VPL SeriesVPL Series
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Sectional ValvesSectional Valves
VPL SeriesVPL Series (C1 Energized)
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VPL Main Spool8 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
Regenative
Options
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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 Valves
With either
Mechanical or
Electrical
Feedback (spool
position).
Servo
Performance,
Closed Loop
Valves with Spool
Position Feedback
NFPA Mounting
With Spool
Position
Feedback
NFPA Mounting
Without Spool
Position
Feedback
Mobile bankable
Style, Threaded
Cartridge Style
BDsDYs
SEs
D*FPD*FHs
D*1FH
D*FXsD*FWs, D*FTsPulsar VP,VPLs.
Parker Models
Closed Loop
Position & Force
Closed Loop
Position & Force
Low End Closed
Loop Position
Open Loop ControlApplications
None10003000 PSI10002000 PSIOperating
Pressures Limits
(Drop across
metering edge).
Zero OverlapZero OverlapOverlap 520%Center Lap
Condition
100200 Hz50...150 Hz10.70 Hz1050 Hz< 10 HzFrequency
Response
0.1..0.5%0.1.5%0.03..1%37%3..7%Hysteresis
Torque Motor Pilot
Control
Balance 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)
Servo
ValvesProportional 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
PlungerPlunger
(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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0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 8 100
SPOOL SHIFT, %
FLOWAR
EA%
0
10
20
3040
50
60
70
80
90
100
0 20 40 60 8 100SPOOL SHIFT, %
FLOW
AREA%
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
meteringnotch
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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
-
+
K100
Vout
inV-+
K100
K100
-
+
K100
DBE+
K100
DBE
K100
CCV+
CCV
ss+
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Deadband
Compensation
+ Q
I+
-
Deadband Compensation
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Deadband Over
Compensated
+ Q
I+
-
Deadband Compensation
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Valve Drivers (Open Loop) On Board
Integrated 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 Board
Integrated 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).
ServoPerformance,
Closed Loop
Valves with Spool
Position Feedback
NFPA MountingWith Spool
Position
Feedback
NFPA MountingWithout Spool
Position
Feedback
Mobile bankableStyle, Threaded
Cartrdige Style
BDs
DYs
SEs
D*FH
D*FMs
D*1FH
D*FXsD*FWs, D*FTsPulsar VP,
VPLs.DF**, ERVs
Parker Models
Closed Loop
Position & Force
Closed Loop
Position & Force
Low End Closed
Loop Position
Open Loop ControlApplications
None10003000 PSI10002000 PSIOperating
Pressures Limits
(Drop across
metering edge).
Zero OverlapZero OverlapOverlap 520%Center Lap
Condition
100200 Hz50...150 Hz10.70 Hz1050 Hz< 10 HzFrequency
Response
0.1..0.5%0.1.5%0.03..1%37%3..7%Hysteresis
Torque Motor Pilot
Control
Balance 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)
Servo
ValvesProportional Valves
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Spool Feedback, How does it Work?
Solenoid ASolenoid B
Spool Position LVDT Integrated Electronics
(PWD Amplifier)
Same basic operation as non-feedback valves, but
outcome is measured and corrected to match desiredresult.
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
X
FB-
A
Disturbances
adj
Spool Feedback Devices(Electrical Schematic-IntegratedElectronics)
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Command
Signal
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
FlowR
ate,
GPM
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 4
4 notches instead of 62 notches instead of 6
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Non-symmetrical Spools
holes7.1
holes85.holes7.1
holes85.
SP
A 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 Valve
Performance over
entire Pressure
Range
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ServoP ti l V l
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Servo ValvesWith either
Mechanical or
Electrical
Feedback (spool
position).
ServoPerformance,
Closed Loop
Valves with Spool
Position Feedback
NFPA MountingWith Spool
Position
Feedback
NFPA MountingWithout Spool
Position
Feedback
Mobile bankableStyle, Threaded
Cartrdige Style
BDs
DYsSEs
D*FH
D*FMsD*1FH
D*FXsD*FWs, D*FTsPulsar VP,
VPLs.DF**, ERVs
Parker Models
Closed Loop
Position & Force
Closed Loop
Position & Force
Low End Closed
Loop Position
Open Loop ControlApplications
None10003000 PSI10002000 PSIOperating
Pressures Limits
(Drop across
metering edge).
Zero OverlapZero OverlapOverlap 520%Center Lap
Condition
100200 Hz50...150 Hz10.70 Hz1050 Hz< 10 HzFrequency
Response
0.1..0.5%0.1.5%0.03..1%37%3..7%Hysteresis
Torque Motor Pilot
Control
Balance 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)
ValvesProportional 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 assembly
fail-safe position
VCDMilestone for High
Performance Valves
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Parker Voice Coil Drive (VCD) technology for
highest precisionpermanent
magnet
coil
carriage housing
integrated feedback
system
pushpin
VCDMilestone for
High Performance Valves
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VCD Mil f Hi h
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VCD principle, moved coil in magnetic field
Fo= B. I . l
-Fo X
Fo
B = magnetic flux density
I = electrical current
l = wire length (winding)
N S
winding
permanent magnet
iron (magnetic)
non-magnetic material
X
VCDMilestone for High
Performance Valves
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VCD Mil t f Hi h
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Characteristics of force in comparison
F[N]
x [mm]
F [N]
x [mm]0 0conventional solenoid
force dependent of stroke
VCDMilestone for High
Performance Valves
Voice Coil Drive
force independent of stroke
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S S l id/V i C il V l
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Ps
A B
T T
HousingSleeve
Servo Solenoid/Voice Coil Valves
No DeadbandLine to Line LapOr Axis Cut
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S l d Sl A t
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Spool and Sleeve Arrangement
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Spool Lap Conditions
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Spool Lap Conditions
(Positive) Overlap
Zerolap
(Negative) Underlap
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Spool Lap Conditions
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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
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Flow windows
Standard Symmetrical Laps
Knick Servo Cuts
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Servo
ValvesProportional Valves
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Servo ValvesWith either
Mechanical or
Electrical
Feedback (spool
position).
ServoPerformance,
Closed Loop
Valves with Spool
Position Feedback
NFPA MountingWith Spool
Position
Feedback
NFPA MountingWithout Spool
Position
Feedback
Mobile bankableStyle, Threaded
Cartrdige Style
BDs
DYs
SEs
D*FH
D*FMs
D*1FH
D*FXsD*FWs, D*FTsPulsar VP,
VPLs.DF**, ERVs
Parker Models
Closed Loop
Position & Force
Closed Loop
Position & Force
Low End Closed
Loop Position
Open Loop ControlApplications
None10003000 PSI10002000 PSIOperating
Pressures Limits
(Drop across
metering edge).
Zero OverlapZero OverlapOverlap 520%Center Lap
Condition
100200 Hz50...150 Hz10.70 Hz1050 Hz< 10 HzFrequency
Response
0.1..0.5%0.1.5%0.03..1%37%3..7%Hysteresis
Torque Motor Pilot
Control
Balance 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)
Valves
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Servo Valve Double Flapper Design
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Servo Valve Double Flapper Design
Torque Motor
Spool & Sleeve
Assembly
Feedback Spring
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S V l
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Servo Valve Double Flapper Design
Flexure Tube
N
S
N
S
FrameCoil Coil
Flapper
Armature
Feedback Spring
and Ball/Ruby
Nozzle
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Servo Valve Principles of Operation
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N
S
N
S
PP
P P
RR
A B
Servo Valve - Principles of Operation
Valve at Null
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Servo Valve - Principles of Operation
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N
S
N
S
P
P P
R
A B
P R
(-)
(+)
Servo Valve - Principles of Operation
Valve With Current Applied
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Flow Forces Not an Issue with Servo
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Flow Forces Not an Issue with Servo
Valves
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Servo s Performances
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Servo s Performances
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Symbology
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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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Pressure Gain
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80% rise
2% command
40% pressure change
1% command change
Pressure Gain
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Hysteresis
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y
%ofFullOpenFlow
Input Signal
Mechanical
Spool
Overlap: the
DeadbandIncreasing Flow
from Valve
Decreasing Flow
from 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
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p y
%ofFullOpenFlow
Input Signal
IncreasingFlow
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
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q y
Two methods: frequency response, step
response (well use frequency response)
offset
bias
CMD
Q
Bias or one sided
CMD
Q
Thru center
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Valve Frequency Response
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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 = cycle
Valve Frequency Response
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Frequency Response
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q y p
To measure the response of a control
valve, a sinusoidal varying input signal isapplied, 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 valvebecomes less able to follow the input
signal precisely
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Frequency Response
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The output starts to lag behind the input,
then the valve is not able to reach themaximum output position before the input
signal reverses
The lag between the input and output isknown as phase lag
The reduced output apparent at higherfrequencies is known as attenuation
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Valve Frequency
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Frequency response (sine wave) to make catalog data
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Servo
ValvesProportional Valves
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Servo Valves
With either
Mechanical or
Electrical
Feedback (spool
position).
Servo
Performance,
Closed Loop
Valves with Spool
Position Feedback
NFPA Mounting
With Spool
Position
Feedback
NFPA Mounting
Without Spool
Position
Feedback
Mobile bankable
Style, Threaded
Cartrdige Style
BDs
DYsSEs
D*FH
D*FMsD*1FH
D*FXsD*FWs, D*FTsPulsar VP,
VPLs.DF**, ERVs
Parker Models
Closed Loop
Position & Force
Closed Loop
Position & Force
Low End Closed
Loop Position
Open Loop ControlApplications
None10003000 PSI10002000 PSIOperating
Pressures Limits
(Drop across
metering edge).
Zero OverlapZero OverlapOverlap 520%Center Lap
Condition
100200 Hz50...150 Hz10.70 Hz1050 Hz< 10 HzFrequency
Response
0.1..0.5%0.1.5%0.03..1%37%3..7%Hysteresis
Torque Motor Pilot
Control
Balance 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)
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Actuators
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Linear Motion
Position Control
Velocity
Force
Rotary Motion
Position Control (Angle)Velocity
Torque
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Actuators Linear Feedback Types
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Magnetostrictive (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 Types
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Magnetostrictive (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
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Elec
Converts Command Signal to
PWM signal to drive Coil.
Digital Versions (shown)
incorporate a microprocessorwith numeric settings.
Analog Versions incorporate
Trim pots for
Optional
Set point card
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Valve Drivers (Open Loop) Off Board
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Elec
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Valve Drivers (Closed Loop)
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Valve Drivers (Closed Loop)
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Motion Controllers
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ActualPosition
PositionError Proportional
Gain
Accumulator(Integrator)
Error(Differentiator)
IntegralGain
DifferentialGain
FeedForward
Forward
Position(Velocity)
+
-
DriveOutput
Target
Generator
Target
Position
CommandProcessor
LadderLogic RmcWin
Accel Fee dVelocity(Acceleration)
DeadbandEliminator
Velocity
Position
Generate A Target Profile
PLC
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Velocity and Accel Feed ForwardPosition
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ActualPosition
Error ProportionalGain
Accumulator(Integrator)
Error(Differentiator)
IntegralGain
Differential
Gain
FeedForward
Forward
Position(Velocity)
+
-
DriveOutput
Target
Generator
TargetPosition
CommandProcessor
LadderLogic RmcWin
Accel Fee dVelocity (Acceleration)
DeadbandEliminator
Target Position Target VelocityVelocity FFWD Drive
Target Acceleration Accel FFWD Drive
DRIVE
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Proportional Gain ONLY
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0.625 Following Error
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Feed Forward Adjust F Cmd
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Correct drive for
constant velocityportion of move.
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Position Error during
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Accel/Decel
Accel FFWD corrects for
error during Accel/Decel
Boost
Brake
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Proper Velocity and Accel Feed
f d
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forwards.
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R l Ti Pl t D t
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Real Time Plot Data
Actual
Position
Actual
Velocity
Voltage to
Servo Valve
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Closed Loop Position SystemControl Drive
Signal from the
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Reservoir
Metal Tubing
MDT
Magnet
Pump
Valve
Signal from theMotion Control
Module
Manifold
Position
Transducers
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Principle of Operation Force Balance
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Balanced Force
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FbFb==PbPb*Area b*Area bFaFa=Pa*Area a=Pa*Area a
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Principle of operation (cont)
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Valve null = net
forces across
cylinder equal
zero
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Closed Loop Force ControlControl Drive
Signal from theMotion Control
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Reservoir
Metal Tubing
MDT
Magnet
Pump
Valve
Signal from theMotion Control
Module
Manifold
Differential
Pressure
Transducers
Load Cellor
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Balanced Force
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FbFb==PbPb*Area b*Area bFaFa=Pa*Area a=Pa*Area a
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Force Control
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In Position Control
Start Force Control
Maintained
Force for X
amount of Time
Increased Force
With different
Ramp Rate
Decompression
Back into
Position Control
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Thank you!
96