27.a bo anderson lectures on mobilehydraulics_part1_tmms10_2011
TRANSCRIPT
©2009 Bo R Andersson
Hydraulic systems for Mobile
Applications• 1st Lecture
– Types of directional valves
– Steady State behaviour
Sid 1
• 2nd Lecture
– System Dynamics
TMMS10 Fluida system och transmissioner
2011-05-16
Bo R Andersson
©2009 Bo R Andersson 2
Content
- Introduction to mobile systems
- Hydraulic operation of a load
- Directional valves for mobile applications
- Closed centre valve
- Open centre valve
- LS
- Computer operated valve
1st Lecture
May 16, 2011
Bo R Andersson
Comparison of properties:
-Operateability
-Power effectiveness
-Complexity
©2009 Bo R Andersson 3
Control of position by control of velocity(change of velocity, acceleration, deceleration)
Introduction to Mobile Systems
©2009 Bo R Andersson Linköpings universitetSid 4
Control of working hydraulics
Typical for mobile machines:
-Control of load or implement
-Controlled by an operator
-Load conditions change continuously
-Simultaneous operation of several functions
-One pump to several functions
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Mobile Hydraulics”Continously operated by a human being”
Difficulties and challenges:• Wide operating range
• No consistency between flow and speed
• Simultanous operation of several functions
• Saturation of pump flow
• Low efficiency and heat generation
• Safety and stability
• Low natural frequency and low damping
• Cost
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Closed Centre Open Centre Load Sensing
Types of mobile valves:
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Types of pumps:
Constant Pressure
Variable Flow
Constant Flow
Variable Pressure
Variable Pressure
Variable Flow
Closed Centre Open Centre Load Sensing
Types of mobile valves:
©2009 Bo R Andersson Sid 8
Types of mobile valves:
Closed Centre Open Centre Load Sensing
Types of pumps:
Constant Pressure
Variable Flow
Constant Flow
Variable Pressure
Variable Pressure
Variable Flow
©2009 Bo R Andersson
Hydraulic operation of a Load
©2009 Bo R Andersson Sid 10
©2009 Bo R Andersson Sid 11
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Closed Center Valve
©2009 Bo R Andersson
Velocity Gain (Angular speed of Arm/Speed of cylinder)
0
1
2
3
4
5
6
7
8
0 20 40 60 80 100 120 140 160 180
Angle of Arm
Vel
oci
ty G
ain
No direct relation between flow and velocity!
©2009 Bo R Andersson Sid 14
Closed Center Valve
Qp-Diagram for Closed-Center Valve
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100
Q Load %
p L
oad % dQ
dp
20% 30% 40%
50%
60%
70%
80%
100%
Constant Pressure System
©2009 Bo R Andersson
Open-Centre Valve
Öppningsareor
0
5
10
15
20
25
30
0 1 2 3 4 5 6
Slidläge [mm]
Öp
pn
ing
[m
m^
2]
P - A
B - T
Aoc
Load drop check valves
Constant Flow System
©2009 Bo R Andersson
Example of Open-Centre Valve
Open-Centre valve with a Q-Inlet.
©2009 Bo R Andersson
Open Centre valves
Most common valve type
Advantages:
- Simple and cost effective
- Control of both flow and pressure
- High damping, good dynamic performance
Disadvantages:
- Low efficiency with fixed depl. pump
- Difficult to limit port flow
- Flow control is load dependent
- Interaction between loads (load interference)
©2009 Bo R Andersson
LS-system
Load Drop Check Valve
00
20
40
60
l/min
3 4 52 61 mm345 26 1
Valve Characteristic
©2009 Bo R Andersson
LS-system
Load Drop Check ValvesPressure compensators
©2009 Bo R Andersson
LS-system
Load Drop Check ValvesPressure compensators
Power Usage Dual OperationPower Usage Single Operation
©2009 Bo R Andersson
Flow Control Valves
p
q
Post- and pre-pressure compensation
)(2 21 ppACQ q
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Post-Pressure Compensation
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Post-Pressure Compensation,
Rexroth type
German: LUDV – Lastunabhängige Durchfluss Verteiligung
Flow Sharing
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Rexroth LUDV
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Rexroth M6-15, LUDV
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EFM -Electrohydraulic Flow Matching
©2009 Bo R Andersson Sid 27
EFM -Electrohydraulic Flow Matching
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Energy Efficient Systems
©2009 Bo R Andersson
Utan laståtervinning
Conventional
LS-system
Average hydraulic power during a working cycle
Energy Efficient Systems
©2009 Bo R Andersson
Reduction of Power Losses
Energy Effective Systems
Low Pressure
Regeneration
High Pressure
Regeneration
Energy
Recuperation
©2009 Bo R Andersson
Reduction of Power Losses
Energy Effective Systems
3-port Valves 2-port Valves
©2009 Bo R Andersson
Computer Controlled Valves
©2009 Bo R Andersson
Eaton: Ultronics
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4. High Power
Force Motor
6. Pilot slid
5. Centreringsfjäder
8. Pressure
transducers
2. Independent
spolls
1. Valve of Mono-
block type
3. Pilot ventil
9. Inbäddad ASIC signalprocessor
7. Position
transducer,
LVDT
Ultronics System Översikt: … TS16 Elektro-Hydraulisk Ventil
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Ultronics
©2009 Bo R Andersson
Husco: Incova
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-Pressure sensitive (unbalanced pilot)
-Low bandwidth
-Long-stroke solenoid
-Poor accuracy
Design issues:
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Decoupling of pressure and flow
- Use of sophisticated control theory
- Requires good knowledge of the application
©2009 Bo R Andersson
Computer Operated Valves
• The beauty with computer control and with all sensors is that the control possibilities are endless
• At the same time, the computer control has the following disadvantages and difficulties:– Safety
– Reliability
– Development time and cost
– Production cost
– Must meet ISO 15998 and EN 61508
– …