First fare 2011 overview of pneumatics-2012

Overview of Pneumatics 1425 Wilsonville Robotics Tim Bennington-Davis [email_address] (503) 449-9507

Why Use Pneumatics ?
To power Actuators
Powerful, reliable, durable
Good lifters, long extension, quick action for short throws

Typical Applications
Two-position linear applications
A “lifter” or “gate”
Transmission shifter
Arm extender
Means to impart energy
Load the spring of a kicking device
Limited-arc rotary applications
Gripper
Arm Elbow or Shoulder

What will it cost you?
Weight
Battery power
Space on the robot
Logistics to get the right parts

Pneumatic Schematic

Pneumatic System

Elements of the System
Compressor
Safety Release Valve
Air Tanks
Pressure Gauges
Pressure Regulator
Pressure Switch, vent valve
Tubing and fittings
Solenoids
Actuators

Pneumatic System Compressor Air Tanks Pressure Gauge (high press) Pressure Gauge (working press) Regulator Pressure switch and vent Solenoid Actuator Safety release valve

Compressor
New model in 2011 – lighter
Earlier model also legal (probably)
Mount with rubber mounts to solid surface
Power with Spike (replace fuse with 20A circuit interrupter)

Safety release valve
Releases at 120 psi – prevents over-pressure condition
Must be placed on high-pressure side (prior to regulator)
Recommend mounting at compressor

Air Tanks
Reservoirs for pressurized air
May use more than one
Typically used on high-pressure side

Gauges and Regulators
Norgren regulator mandatory, regulates high pressure side down to 60 psi
Relieving regulator to deal with pressure spikes from mechanical compression
Must have gauge on high pressure side, and on low-pressure side

Pressure switch and valve
Switch opens at 115 psi, closes at 95
Must be connected to digital input on digital sidecar – NOT in series with power
Valve is to release pressure from system

Tubing
Must have clear pressure marking
Typically 0.25” OD
Always cut with tubing cutter, square end

Solenoids
Driven by pneumatic bumper on cRIO
Available in single- and double-action
12v or 24v, compatible with pneumatic bumper

Actuators
Typical device is a linear ram
Available in many sizes
Length (throw)
Diameter (bore)
Mounting configurations
3 cylinders are available at no cost but you must order them

Useful Tricks – Flow control
Flow control valves
Mount at air inlet on actuators
Control speed of action, not force

Useful Tricks – Magnet Switch
Magnetic switch option
Mount switch to side of ram
Use digital input to cRIO to detect switch closure
Lets software know when piston is at certain position
Turn “2 position” ram into “multiple”
Requires double-action solenoid

More on Solenoids
Single Action
One electrical connection
Controls “two position” operation
Double Action
Two electrical connections
Enables multi-position operation

Helpful Hints

System tradeoffs
Big rams use more air (stroke and bore)
Frequent use of air during match can outrun your compressor
If your air use is limited enough, you can consider charging tanks in the pit, and not mounting compressor
Save weight, cost and battery power

Good Factoids
Order your actuators EARLY. There are lead times involved.
Cut tubing square, and don’t tolerate leaks.
Eats your battery life
If you count on a “pre-charge” lasting, and there is a delay in field play, your air leaks out.
Get on the Bimba website and get familiar with their parts
If you want magnetic switches, you must order magnetic rams.
Get your three actuators, even if you don’t use them this year

Summary
Well-suited for:
Fast movement
Two-position mechanisms
Creating substantial force
Sustained Holding
Not so good for
Precision position control
Sustained movement
Exercise safety

Great resources
FIRST website
Pneumatics Manual
Rules from 2011
Google “FIRST pneumatics”
You’ll get several hits from teams who have done tutorials, including calculations

First fare 2011 overview of pneumatics-2012

by Oregon FIRST Robotics on Oct 16, 2011

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