FLUID POWER!

SEE SPLASH 2008

FOLDER

TODAY

• Learn some fluid power basics

• Hands-on project with pneumatic components

• Some possibilities for your FIRST robot

What is fluid power?

• Uses:• Heavy equipment

• Construction industry

• Off-road vehicles

• Manufacturing

WHY FLUID POWER?

STRONG!

LIGHT!

EASY!

CCEFP

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 = 10:1

Reference: I. L. Krivts and G. V. Krejnin, Pneumatic Actuating Systems for Automatic Equipment, Taylor and Francis, 2006.

CCEFP

CENTER FOR COMPACT AND EFFICIENT FLUID POWER

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

CCEFP

CCEFP testbeds

Existing FP applications

FP enabledbreakthroughs

in transportation

New industries & applications

TB1: Excavator TB2*: Injection molding machine

TB3: small UrbanVehicle (sUV)

TB4: Compact Rescue Crawler

TB5*: FP assistedhand tools

TB6: FP assistedorthoses & prostheses

* Reduced or delayed funding

                                        

                                                                                                                    

HIGH COUNTRY TEK

Member of the Schaeffler Group

National Tube Supply Company

Ralph Rivera

Master Pneumatic

Pneumatics compared to hydraulics

• No problems of a spills• Compressibility stores energy

– Available for your use– Dangerous if excessive

volumes or pressures

• Difficult to control precisely• Fluid is readily available

– Should be filtered, dry

• Usually lower forces

Safety Must AlwaysBe Considered!

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

P V mR T

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

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

Assume constant temperature:

P = pressure in tank (absolute)

V = volume of tank

Patm= atmospheric pressure = 101,325 Pa or 14.7 psi

constant mRTPV

)/ln( E atmPPPV

Energy:

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?

How much energy in your tankcan you use?

• Line losses:Pressure drop proportional to flow

• Throttling losses:Pressure drop proportional to flow squared

• Cylinder friction:Coulomb plus viscous friction, depends on seals

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

CYLINDER FORCE AT 60 PSI

0

100

200

300

400

500

600

700

800

0 1 2 3 4 5

BORE (IN.)

fOR

CE

(L

BS

)

The Effect of Different Areas

Pressure P

Pressure P

Area APArea AR

Force FHow much force F is necessary to hold the rod still?

Pressure Patmosphere

Pneumatic components seen in the FIRST Robotics competition

LET'S BUILD!