Introduction to Electro-hydraulic Proportional and Servo Valves
1
Servo Valves
Proportional Valves Mobile bankable Style, Threaded Cartrdige Style
NFPA Mounting Without Spool Position Feedback
NFPA Mounting With Spool Position Feedback
Servo Performance, Closed Loop Valves with Spool Position Feedback
Servo Valves With either Mechanical or Electrical Feedback (spool position).
Parker Models
Pulsar VP, VPLs.
D*FWs, D*FTs’
D*FXs’
D*FP D*FHs D*1FH
BDs’ DYs’ SEs’
Mechanical Construction (spool shift)
Electro-Hydraulic Pilot, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Torque Motor Pilot Control Balance PSI spool Control
Hysteresis
3…..7%
3…7%
0.03…..1%
0.1….5%
0.1…..0.5%
Frequency Response
< 10 Hz
10…50 Hz
10….70 Hz
50...150 Hz
100…200 Hz
Center Lap Condition
Overlap 5…20%
Zero Overlap
Zero Overlap
Operating Pressures Limits (Drop across metering edge).
1000…2000 PSI
1000…3000 PSI
None
Closed Loop Position & Force
Closed Loop Position & Force
Applications
2
Open Loop Control
Low End Closed Loop Position
Meter Out Circuit
P to A B to T
T
Free flow into the “cap” end Metered Flow out the “head” end.
3
P
A
T
B
Meter Out Circuit
P to B A to T
T
Free flow into the “cap” end Metered Flow out the “head” end.
4
P
A
T
B
Electrohydraulic Valves
P to A B to T T
Shift Spool slightly to create metering Orifice
5
P
A
T
B
Servo Valves
Proportional Valves Mobile bankable Style, Threaded Cartridge Style
NFPA Mounting Without Spool Position Feedback
NFPA Mounting With Spool Position Feedback
Servo Performance, Closed Loop Valves with Spool Position Feedback
Servo Valves With either Mechanical or Electrical Feedback (spool position).
Parker Models
Pulsar VP, VPLs.
D*FWs, D*FTs’
D*FXs’
D*FP D*FHs D*1FH
BDs’ DYs’ SEs’
Mechanical Construction (spool shift)
Electro-Hydraulic Pilot, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Torque Motor Pilot Control Balance PSI spool Control
Hysteresis
3…..7%
3…7%
0.03…..1%
0.1….5%
0.1…..0.5%
Frequency Response
< 10 Hz
10…50 Hz
10….70 Hz
50...150 Hz
100…200 Hz
Center Lap Condition
Overlap 5…20%
Zero Overlap
Zero Overlap
Operating Pressures Limits (Drop across metering edge).
1000…2000 PSI
1000…3000 PSI
None
Closed Loop Position & Force
Closed Loop Position & Force
Applications
6
Open Loop Control
Low End Closed Loop Position
Sectional Valves VPL Series
C2
C1
Limiter
Compensator
P
7
T
Sectional Valves VPL Series Pulsar Solenoid
Cyl. Relief
Anti-Cav. Check
C1 Pressure Limiter
Manual Override
Flow Limiters Optional L.S. Port 8
Individual Compensator
C2 Pressure Limiter
Sectional Valves VPL Series (C1 Energized)
9
VPL Main Spool 8 Flow Rates (1.3, 2.5, 4, 7, 11, 17, 24, 30 GPM) OCM VOC CC
Spool
Meter-In Lands
Marking Ex. 524
Centering Spring 200 or 350 PSI
Meter-Out Lands
Detent & Friction-Lock also Available
10
Regenative Options
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
11
VPL Compensator Components
3 Sizes of Shims (.003” .008” .025”)
12
Servo Valves
Proportional Valves Mobile bankable Style, Threaded Cartridge Style
NFPA Mounting Without Spool Position Feedback
NFPA Mounting With Spool Position Feedback
Servo Performance, Closed Loop Valves with Spool Position Feedback
Servo Valves With either Mechanical or Electrical Feedback (spool position).
Parker Models
Pulsar VP, VPLs.
D*FWs, D*FTs’
D*FXs’
D*FP D*FHs D*1FH
BDs’ DYs’ SEs’
Mechanical Construction (spool shift)
Electro-Hydraulic Pilot, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Torque Motor Pilot Control Balance PSI spool Control
Hysteresis
3…..7%
3…7%
0.03…..1%
0.1….5%
0.1…..0.5%
Frequency Response
< 10 Hz
10…50 Hz
10….70 Hz
50...150 Hz
100…200 Hz
Center Lap Condition
Overlap 5…20%
Zero Overlap
Zero Overlap
Operating Pressures Limits (Drop across metering edge).
1000…2000 PSI
1000…3000 PSI
None
Closed Loop Position & Force
Closed Loop Position & Force
Applications
13
Open Loop Control
Low End Closed Loop Position
How does it Work?
(No Spool Feedback)
“Integrated Electronics” (PWD Amplifier) Solenoid “B”
Solenoid “A”
“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. 14
How does it Work? Proportional Solenoid Construction Frame Winding
Plunger (armature) Push pin
15
How does it Work? Solenoid Operation
.5 VDC 50% .
16
Proportional Valve Spool Designs
V-Notch Spool
C-Notch Spool
17
FLOW AREA %
Proportional Valve Spool Designs P-A-B-T = 145 PSI
100 90 80 70 60 50 40 30 20 10 0
FLOW AREA %
0
40 60 SPOOL SHIFT, %
8
100
8
100
P-A-B-T = 145 PSI
100 90 80 70 60 50 40 30 20 10 0 0
18
20
20
40 60 SPOOL SHIFT, %
V-Notch - Bleed Center
bleed notch
primary metering notch
19
Proportional Valve Deadband Ps
T
A 20
T
B
Positive Overlap + Spring Force + Q
+ I Mechanical Spool Overlap (Deadband)
21
Deadband Eliminator 100 KΩ 100 KΩ
100 KΩ
+
Vin
100 KΩ
+ +s
+ DBE 100 KΩ
−s
− DBE + VCC 22
− VCC
100 KΩ
+
Vout
Deadband Compensation + Q
+ I Deadband Compensation
23
Deadband Compensation + Q
+ I Deadband Over Compensated
24
Valve Drivers (Open Loop) On Board Integrated Electronics
25
Valve Drivers (Open Loop) On Board Integrated Electronics (Pot adjustments) Ramp Pots
Max Pots
MIN Pots 26
Valve Drivers (Open Loop) On Board Integrated Electronics (PC Adjustments) Digital Onboard Electronics
D1FB*0 OBE
27
Deadband Eliminator P to A flow Path Ps
T
A 28
T
B
Deadband Eliminator (P to B flow Path) Ps
T
A 29
T
B
Servo Valves
Proportional Valves Mobile bankable Style, Threaded Cartrdige Style
NFPA Mounting Without Spool Position Feedback
NFPA Mounting With Spool Position Feedback
Servo Performance, Closed Loop Valves with Spool Position Feedback
Servo Valves With either Mechanical or Electrical Feedback (spool position).
Parker Models
Pulsar VP, VPLs. DF**, ERVs
D*FWs, D*FTs’
D*FXs’
D*FH D*FMs D*1FH
BDs’ DYs’ SEs’
Mechanical Construction (spool shift)
Electro-Hydraulic Pilot, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Torque Motor Pilot Control Balance PSI spool Control
Hysteresis
3…..7%
3…7%
0.03…..1%
0.1….5%
0.1…..0.5%
Frequency Response
< 10 Hz
10…50 Hz
10….70 Hz
50...150 Hz
100…200 Hz
Center Lap Condition
Overlap 5…20%
Zero Overlap
Zero Overlap
Operating Pressures Limits (Drop across metering edge).
1000…2000 PSI
1000…3000 PSI
None
Closed Loop Position & Force
Closed Loop Position & Force
Applications
30
Open Loop Control
Low End Closed Loop Position
Spool Feedback, How does it Work? Spool Position LVDT
“Integrated Electronics” (PWD Amplifier)
Solenoid “B” Solenoid “A”
•Same basic operation as non-feedback valves, but “outcome” is measured and corrected to match desired result. •“Closing the Loop”.
31
Spool Feedback Device Linear Variable Differential Transformer Input V DC
Oscillator
Primary
Spool Core
Secondary
Output V DC
Demodulator 32
Secondary
L.V.D.T.s
33
Spool Feedback Devices (Electrical Schematic-Integrated Electronics) Disturbances adj CMD +
Error
I
F
A
FB LVDT
34
X
Internal Closed Loop Force
u s
Command Signal
Valve position feedback 35
Sample Application
36
Kv Sizing
37
Non-Symmetrical Spools
38
Sample Application, Number 2
39
Non-Symmetrical Spools (P-A-B-T = 145 PSI) 10 7.5
Flow Rate, GPM
5 2.5 0 -10
-7.5
-5
-2.5 0 -2.5
2.5
-5 -7.5 -10 Valve Command, Volts
40
5
7.5
10
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 6 2 notches instead of 6…
41
Non-symmetrical Spools
P
T
A 1.7 holes
A
.85holes
B
PS 1.7 holes
42
.85holes
T
B
Sample Application No. 2 with NonSymmetrical Spool
43
Flow Force Effects Proportional Valves Flow
∆X
44
Flow Force Performance Operating Limits Curves show Valve Performance over entire Pressure Range
45
Servo Valves
Proportional Valves Mobile bankable Style, Threaded Cartrdige Style
NFPA Mounting Without Spool Position Feedback
NFPA Mounting With Spool Position Feedback
Servo Performance, Closed Loop Valves with Spool Position Feedback
Servo Valves With either Mechanical or Electrical Feedback (spool position).
Parker Models
Pulsar VP, VPLs. DF**, ERVs
D*FWs, D*FTs’
D*FXs’
D*FH D*FMs D*1FH
BDs’ DYs’ SEs’
Mechanical Construction (spool shift)
Electro-Hydraulic Pilot, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Torque Motor Pilot Control Balance PSI spool Control
Hysteresis
3…..7%
3…7%
0.03…..1%
0.1….5%
0.1…..0.5%
Frequency Response
< 10 Hz
10…50 Hz
10….70 Hz
50...150 Hz
100…200 Hz
Center Lap Condition
Overlap 5…20%
Zero Overlap
Zero Overlap
Operating Pressures Limits (Drop across metering edge).
1000…2000 PSI
1000…3000 PSI
None
Closed Loop Position & Force
Closed Loop Position & Force
Applications
46
Open Loop Control
Low End Closed Loop Position
VCD®…Milestone for High Performance Valves D1FP (NG6) valve as pilot valve for D*1FP integrated drive electronics Voice Coil Drive VCD® valve body spool-sleeve assembly spring assembly fail-safe position 47
VCD®…Milestone for High Performance Valves Parker Voice Coil Drive (VCD®) technology for highest precision integrated feedback system
pushpin 48
carriage
coil
permanent magnet
housing
VCD®…Milestone for High Performance Valves VCD® principle, moved coil in magnetic field -Fo
Β
Fo
X
−Ι
Ι
Fo = B . I . l
N S
B = magnetic flux density I = electrical current l = wire length (winding)
49
permanent magnet
non-magnetic material
winding
iron (magnetic)
VCD®…Milestone for High Performance Valves Characteristics of force in comparison F[N]
F [N]
0
x [mm]
conventional solenoid force dependent of stroke
50
0
x [mm]
Voice Coil Drive force independent of stroke
Servo Solenoid/Voice Coil Valves “Line to Line” Lap Or “Axis Cut”
No Deadband
B
A Sleeve 51
T
Ps
T
Housing
Spool and Sleeve Arrangement
52
Spool Lap Conditions (Positive) Overlap
Zerolap
(Negative) Underlap
53
Spool Lap Conditions (Positive) Overlap
Zerolap
U = 40%
U = 40%
U = 20%
U = 20%
U = 0%
U = 0%
54
Flow windows •Standard Symmetrical Laps
•“Knick Servo Cuts”
55
Servo Valves
Proportional Valves Mobile bankable Style, Threaded Cartrdige Style
NFPA Mounting Without Spool Position Feedback
NFPA Mounting With Spool Position Feedback
Servo Performance, Closed Loop Valves with Spool Position Feedback
Servo Valves With either Mechanical or Electrical Feedback (spool position).
Parker Models
Pulsar VP, VPLs. DF**, ERVs
D*FWs, D*FTs’
D*FXs’
D*FH D*FMs D*1FH
BDs’ DYs’ SEs’
Mechanical Construction (spool shift)
Electro-Hydraulic Pilot, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Torque Motor Pilot Control Balance PSI spool Control
Hysteresis
3…..7%
3…7%
0.03…..1%
0.1….5%
0.1…..0.5%
Frequency Response
< 10 Hz
10…50 Hz
10….70 Hz
50...150 Hz
100…200 Hz
Center Lap Condition
Overlap 5…20%
Zero Overlap
Zero Overlap
Operating Pressures Limits (Drop across metering edge).
1000…2000 PSI
1000…3000 PSI
None
Closed Loop Position & Force
Closed Loop Position & Force
Applications
56
Open Loop Control
Low End Closed Loop Position
Servo Valve – Double Flapper Design Torque Motor
Spool & Sleeve Assembly
57
Feedback Spring
Servo Valve – Double Flapper Design Armature Frame
Coil
Coil
N
N
S
S
Flapper Flexure Tube
Nozzle
58
Feedback Spring and Ball/Ruby
Servo Valve - Principles of Operation Valve at “Null”
N
N
S
S
P
P R
P
A
59
R
P
B
Servo Valve - Principles of Operation Valve With Current Applied (+)
(-)
N
N
S
S
P
P R
P
A
60
R
P
B
Flow Forces Not an Issue with Servo Valves
61
Servo ‘s Performances
62
Symbology Proportional Valve with Spool Feedback
Proportional Directional Valve
u
Servo Performance Proportional Valve
u
63
s
s
Servo Valve
Terminologies
64
Pressure Gain 40% pressure change 1% command change
80% rise
2% command
65
Hysteresis Decreasing Flow from Valve
100% 90%
% of Full Open Flow
80% 70% 60%
Hysteresis
50% 40% Mechanical Spool Overlap: the Deadband
30% 20% 10%
Increasing Flow from Valve
0% 1
66
2
3
4
5
Input Signal
6
7
8
9
10
Repeatability 100% 90% Increasing Flow Only
% of Full Open Flow
80% 70% 60% 50%
Repeatability
40% 30% 20% 10% 0% 1
67
2
3
4
5
Input Signal
6
7
8
9
10
Valve Frequency Two methods: frequency response, step response (we’ll use frequency response) Thru center
Bias or one sided
Q
Q CMD
CMD offset bias
68
Valve Frequency Response 0° Phase Lag CMD
Valve
FB 90° Phase Lag
90° Phase Lag = ¼ cycle The input frequency which creates a phase lag of 90° is the defining characteristics of a valve and is referred to as bandwidth 69
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 70
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
71
Valve Frequency Frequency response (sine wave) to make catalog data
72
Servo Valves
Proportional Valves Mobile bankable Style, Threaded Cartrdige Style
NFPA Mounting Without Spool Position Feedback
NFPA Mounting With Spool Position Feedback
Servo Performance, Closed Loop Valves with Spool Position Feedback
Servo Valves With either Mechanical or Electrical Feedback (spool position).
Parker Models
Pulsar VP, VPLs. DF**, ERVs
D*FWs, D*FTs’
D*FXs’
D*FH D*FMs D*1FH
BDs’ DYs’ SEs’
Mechanical Construction (spool shift)
Electro-Hydraulic Pilot, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Electromagnetic Force, Mechanical (spring) Return
Torque Motor Pilot Control Balance PSI spool Control
Hysteresis
3…..7%
3…7%
0.03…..1%
0.1….5%
0.1…..0.5%
Frequency Response
< 10 Hz
10…50 Hz
10….70 Hz
50...150 Hz
100…200 Hz
Center Lap Condition
Overlap 5…20%
Zero Overlap
Zero Overlap
Operating Pressures Limits (Drop across metering edge).
1000…2000 PSI
1000…3000 PSI
None
Closed Loop Position & Force
Closed Loop Position & Force
Applications
73
Open Loop Control
Low End Closed Loop Position
Actuators Rotary Motion •Position Control (Angle) •Velocity •Torque
Linear Motion •Position Control •Velocity •Force
74
Actuators Linear Feedback Types 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”
75
Actuators Linear Feedback Types Magnetostrictive (M.D.T.s) Analog Outputs SSI Output
Digital Outputs
76
Valve Drivers and Motion Controllers
77
Valve Drivers (Open Loop) Off Board Elec Optional Set point card
• •
•
78
Converts “Command Signal” to PWM signal to drive Coil. Digital Versions (shown) incorporate a microprocessor with numeric settings. Analog Versions incorporate Trim pots for
Valve Drivers (Open Loop) Off Board Elec
79
Valve Drivers (Closed Loop)
80
Valve Drivers (Closed Loop)
81
Motion Controllers Actual Position
-
Position Error
Σ
Proportional G ain
+ Accumulator (Inte grator)
Targe t Position
∆ Error (Diffe re ntiator) ∆ Position (Ve locity)
Targe t G e ne rator
Command Proce ssor Ladde r Logic
∆ Ve locity (Acce le ration)
Inte gral G ain Diffe re ntial G ain Fe e d Forward Acce l Fe e d Forward
Position
De adband Eliminator
RmcWin PLC
“Generate A Target Profile” 82
Σ
Drive O utput
Velocity
Velocity and Accel Feed Forward Actual Position
-
Position Error
Σ
Proportional G ain
+ Accumulator (Inte grator)
Targe t Position
∆ Error
Target(Diffe Velocity re ntiator)
Target Position
∆ Position (Ve locity)
Targe t G e ne rator
∆ Ve locity (Acce le ration)
Command Proce ssor Ladde r Logic
Diffe re ntial Velocity G ain FFWD Drive Σ
Drive O utput
Fe e d Forward Acce l Fe e d Forward De adband Eliminator
RmcWin
Target Acceleration
83
Inte gral G ain
Accel FFWD Drive
DRIVE
Proportional Gain ONLY
0.625” Following Error
84
Feed Forward Adjust “F” Cmd Correct drive for constant velocity portion of move.
85
Position Error during Accel/Decel Brake Accel FFWD corrects for error during Accel/Decel
Boost
86
Proper Velocity and Accel Feed forwards.
87
Real Time Plot Data
Actual Velocity Actual Position
Voltage to Servo Valve
88
Closed Loop Position System Control Drive Signal from the Motion Control Module Metal Tubing
Valve Manifold
Magnet MDT
Position Transducers
Pump Reservoir
89
Principle of Operation Force Balance
90
Balanced Force
Fa=Pa*Area a
91
Fb=Pb*Area b
Principle of operation (cont)
Valve null = net forces across cylinder equal zero
92
Closed Loop Force Control Control Drive Signal from the Motion Control Module Metal Tubing
Valve Manifold
Magnet MDT
Differential Pressure Transducers Pump Reservoir
93
or
Load Cell
Balanced Force
Fa=Pa*Area a
94
Fb=Pb*Area b
Force Control Decompression Start Force Control
Increased Force With different Ramp Rate In Position Control
Maintained Force for X amount of Time
95
Back into Position Control
Thank you!
96
