FLUID POWER

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FLUID POWER!
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TODAY

• Learn some fluid power basics
• Some possibilities for your FIRST robot
• Hands-on project with pneumatic components

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What is fluid power?

• Uses
• Heavy equipment
• Construction industry
• Off-road vehicles
• Manufacturing

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WHY FLUID POWER?
STRONG!
LIGHT!
EASY!
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Fluid Power is Unique Unparalleled torque,
power and bandwidth for the same weight or
volume. Example Power/Weight (kW/kg) Pneumatic
Motor 0.3-0.4 Hydraulic Motor 0.5-1.0 Electric
Motor 0.03-0.1 Fluid power weight advantage
101 Reference I. L. Krivts and G. V. Krejnin,
Pneumatic Actuating Systems for Automatic
Equipment, Taylor and Francis, 2006.

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CENTER FOR COMPACT AND EFFICIENT FLUID POWER

• 100 mpg automobile
• Efficient off-road equipment
• Compact and portable

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CCEFP testbeds
TB1 Excavator
TB2 Injection molding machine
Existing FP applications
TB3 small Urban Vehicle (sUV)
TB5 FP assisted hand tools
FP enabled breakthroughs in transportation
TB4 Compact Rescue Crawler
TB6 FP assisted orthoses prostheses
Reduced or delayed funding
New industries applications
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Pneumatics compared to hydraulics

• No problems of a spills
• Compressibility stores energy
• Available for your use
• Dangerous if excessivevolumes or pressures
• Difficult to control precisely
• Fluid is readily available
• Should be filtered, dry
• Usually lower forces

Safety Must Always Be Considered!
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Pressure of an ideal Gas

• Pressure of a gas is due to the force of gas
  molecules bouncing off the walls.
• Pressure increases when molecules are moving
  faster, heavier, or if there are more molecules.
• Molecules move faster when they are hot.
• mR depends on molecule.

Pressure P
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Getting Work out of Air

• Work is force acting over a distance, ft-lbs.
• Put air in a container under pressure
• Allow part of the container to expand
• The expanding part does work

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How much energy is in a tank filled with
compressed air?
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How much energy is in a small air tank?

• Tank Volume 150 ml or 9.154 in3
• Pressure 413,700 Pa or 60 psi (over Patm)
• Patm 101,325 Pa or 14.7 psi

Answer Energy PV ln(P/Patm) 0.15 x
515025 x ln(74.7/14.7) 125 kJ
Challenge question How high could the instructor
be lifted using the energy in one tank?
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How much energy in your tankcan you use?

• Line lossesPressure drop proportional to flow
• Throttling lossesPressure drop proportional to
  flow squared
• Cylinder frictionCoulomb plus viscous friction,
  depends on seals

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Force available

• Pressure x Area Force
• Area pi x Bore2 / 4
• For example cylinder
• Bore 10 mm .394 in. ? Area .122 in2
• Force PxA 60 psi x .122 in2 7 lbs

Pressure P
Area AP
Force F
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The Effect of Different Areas
Pressure P
Area AR
Area AP
Pressure P
Force F
How much force F is necessary to hold the rod
still?
Pressure Patmosphere
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Pneumatic components seen in the FIRST Robotics
competition
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LET'S BUILD!
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Full Circuit
CYLINDER
CYLINDER
RELIEFVALVE
PGAUGE
VALVE
PUMP
VALVE
TANK
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