Warlocks 8/5/05 TMU

Pneumatics on Robots

Simplified model

CompressedAir

Tank

Geek

SafetyGlasses

60 lbs

Pneumatic Cylinder

Whoa! That’s a lot

of force

PlungerDiaphragm

FORCE= Area of Diaphragm (inches)X Pressure (PSI) in tank.

Force = 1.5 X 60 lbf/in2 = 90 lbs of Force

For a 1.5” cylinder bore area r2 = (1.5/2)2 = 1.76 in2

Warlocks 8/5/05 TMU

Pneumatic Parts

Compressor, 125 PSI, 20 Amps Max, Weight 2.4 lbs– Provides source of pneumatic power

Pressure Switch & gages, 115 PSI high pressure circuit– Pressure switch turns compressor on and off

» On at approx. 100 PSI, Off at 115 PSI

Air Tanks – Reservoir so robot functions are not diminished due to loss of pressure - Stores pneumatic power – like a battery– Compressor output will not always keep up with usage

» How many on last year’s robot?

Warlocks 8/5/05 TMU

Pneumatic Parts

Regulator to regulate pressure to components:

Single & Double Solenoid Valves: electrical control from cRio

Flow Control Valves Change speed of extending and retracting:

Single=> On=Extend, Off=RetractDouble=> Side 1 On Pulse Extend Side 1 Off Same Position Side 2 On Pulse Retract Side 2 Off Same Position

Usually it is 60 PSI or Less; 2 Regulators are provided for regulating High Pressure System 115 PSI and Low pressure system 60 PSI simultaneously.

Too Fast, Slow it down with Flow control.

Warlocks 8/5/05 TMU

Pneumatic Parts

Valve to Release or Fill with Air

Fittings

Cylinder (Various Sizes)

Diameter Range: ½” to 2”

Stroke Range: ½” to 24”

Teflon tape helps prevent leaks at connections – don’t use too much

Warlocks 8/5/05 TMU

Application Information

Force Range @ 100 PSI

Rod diameter – ¼” to ½” – ¼” may bend when robots crash into each other

Mounting options

Warlocks 8/5/05 TMU

Rotary Actuator

Rotary Actuator

Rotational Force =Torque

(0.075/2)2 * PI X 60 PSI = 0.26 ft-lbs(0.875/2)2 * PI X 60 PSI = 36 ft-lbs(1.06/2)2 * PI X 60 PSI= 52 ft-lbs

Warlocks 8/5/05 TMU

Pneumatic diagram

High pressure 115 PSILow pressure 60 PSI

Warlocks 8/5/05 TMU

Pros and Cons of Pneumatics

Reasons for using Pneumatics– Weight: May be less total weight than using Gears and Pulleys & multiple electrical

motors while keeping the same Force – Simple to Design/Easy to Build: A closed loop pneumatic system is easier to design

than gears and pulleys.– Reliable: Pneumatics perform the same over and over again– Force is adjustable and the Force cylinders produce can be significant.– A variety of pneumatic cylinders are offered– We will probably have cylinders already for shifting 2 speed gearbox

Potential Issues with Pneumatics– Pneumatic support system weight – compressor, tanks, regulator, gages

» Need all of these components whether we use 1 or 10 cylinders– Stroke Length is limited to 2 ft max. (There are limits).– Fixed increments of travel – full stroke in or out limited variable positions– Need to make sure system is charged before every match – Leaks are possible and can be annoying to find – always plan on putting

compressor on robot to avoid complete robot system shut-down

Warlocks 8/5/05 TMU

Questions?