1. Landstown High School Governors STEM & Technology Academy
Advanced Robotics
Chapter 6- Fluid Power Systems
Dr. Barger

2. Fluid Power Systems
Fluid power systems use air or liquid, or a combination of both, to transfer power.
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3. Fluid Power Systems Transfer Methods
Electrical energy is often used to drive a fluid pump.
Electrical energy and mechanical motion are converted into the energy of a flowing liquid.
Hydraulic systems use oil, or other liquids, while pneumatic systems use air.
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4. Fluid Power Systems All fluid power systems consist of: Controls,
An energy source,
A transmission path,
A load,
Indicators,
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5. Hydraulic System Model
Hydraulic Systems are used for many applications in Robotics:
Operates motors,
Actuators,
Cylinders (load devices)
Usally electrical energy drives a pump which provides hydraulic pressure,
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6. Hydraulic System Model
Prime Mover system
A prime mover is a component of a power system that provides the initial power for movement in the system,,
The motor receives electrical energy from the source and converts it to rotary energy or movement.
The pump converts the rotary energy into fluid energy.
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7. Basic Hydraulic System
LS 6-1
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8. Hydraulic System Model
Control Systems
A typical hydraulic fluid power system includes a number of control devices,
Directional control valve (DCV) (cylinders),
Pressure relief valves,
A pressure relief valve is a control device that protects the system from stress and damage caused by over pressurizing the system.
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9. Hydraulic Control Devices
LS 6-2
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10. Pneumatic System Model
In a typical pneumatic system, the energy source powers a compressor which forces air into a pressurized storage tank.
The compressor is most often driven by an electric motor, or internal combustion engine.
The storage tank hold the pressurized air and acts as a reservoir for the system.
Typical uses are for:
Power tools, and
Lifting and clamping during machining operations.
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11. Pneumatic System
LS 6-3
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12. Characteristics of Fluid Flow
Fluid power systems do not achieve 100 percent power transfer,
Due to friction from the cylinder walls,
This friction is known as “resistance” or power loss,
Power loss materializes primarily as heat,
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13. Pneumatic Systems Turbulence
Refers to how the fluid moves through the fluid power system.
Conditions of the system, such as:
size and smoothness of the tubing walls,
Location and number of valves and fittings,
may cause irregular flow characteristics.
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14. Pneumatic Systems Pressure drops Energy Loss
Restrictions within the system are also a source of pressure drops.
These can be caused by:
Control valves, tubing length, or small tubing size
Energy Loss
As fluid pressure enters the system, it has the ability to perform a specific amount of work.
Fluid energy is lost because it is changed into heat due to friction and resistance.
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15. Pressure Drops in a Fluid System
LS 6-4
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16. Pneumatic Systems Compression of Fluids
A notable difference between hydraulic and pneumatic systems is the compressibility of the fluids,
All gases and liquids are compressible under certain conditions for each,
Hydraulic fluid is considered incompressible,
Air in pneumatic systems is readily compressible.
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17. Principles of Fluid Power
Pascal’s Law
Pressure applied to a confined fluid is transmitted, undiminished, throughout the fluid.
This pressure acts on all surfaces of the container, at right angles to those surfaces,
For this reason, the walls of the cylinder must be strong enough to withstand the pressure.
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18. Pascal’s Law
LS 6-5
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19. Principles of Fluid Power
Terminology
Force
Is any factor that tends to produce or modify the motion of an object.
Inertia- the amount of force needed to produce motion (or resistance to change) of the body to be moved.
Pressure
Is the amount of force applied to a specific area. Usally in pounds per square inch (psi).
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20. Principles of Fluid Power
Fluid Power System Components
Fluid Pumps
The heart of a fluid system. It provides an appropriate flow to develop pressure.
Two general classifications:
Positive displacement pump,
Has a close clearance between the moving member and stationary pump components,
Non-Positive displacement pump
The fluid is moved by the impeller blades during each revolution.
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21. Fluid Pumps
LS 6-6
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22. Principles of Fluid Power
Examples
Reciprocating pumps- Positive displacement,
Rotary Gear Pumps- positive displacement,
Rotary Vane Pumps- positive displacement,
Centrifugal pumps- non-positive displacement,
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23. Operation of a Reciprocating Pump
LS 6-7
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24. Rotary Gear Pumps
LS 6-8
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25. Rotary Vane Pump
LS 6-9
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26. Centrifugal Pumps
LS 6-10
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27. Pressure Regulator Valve Operation
LS 6-11
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28. Principles of Fluid Power
Fluid Conditioning Devices
Both hydraulic fluid and air must be conditioned before being processed through a fluid power system.
Conditioning devices prolong the life of fluid power systems by removing foreign particles and moisture.
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29. Principles of Fluid Power
Hydraulic Conditioning
The number of components, types of control devices and operating environment are major considerations in hydraulic fluid conditioning.
Types used:
Strainers- Inline devices,
Filters- Inline device,
Heat exchangers-
Forced-air fans,
Water-jacket coolers,
Gas coolers.
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30. Principles of Fluid Power
Pneumatic Conditioning
Several types of devices are used but the most often is a filtering device,
Filters
Filtering must remove moisture and foreign particles, so they contain “desiccant”, which is a very dry material designed to attract moisture,
Lubricators
Lubricators are devices that add a small quantity of oil to the air after it leaves the regulator. The lubrication helps the valves and cylinders operate more efficiently.
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31. FRL Unit
LS 6-12
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32. Fluid Power Systems Control Devices
Control is achieved by devices that alter the pressure, direction and volume of fluid flow.
Pressure Control
Flow Control
Direction Control
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33. Fluid Check Valve (Pressure Control)
LS 6-13
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34. Four-way Valve (Flow Control)
LS 6-15
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35. Flow Control Valve Operation (Direction Control)
LS 6-16
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36. Principles of Fluid Power
Load Devices
The term actuator is often used to identify the load device.
Linear Actuators
Rotary Actuators
Fluid Motors
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37. Linear Actuator
LS 6-17
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38. Rotary Actuators
LS 6-20
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39. Principles of Fluid Power
Hybrid Systems
A number of industrial systems produce mechanical energy by combining fluid power and electrical power systems.
Example:
Hoists use in car repair operations,
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