Introduction to Pneumatics

1. Introduction to Pneumatics MN Splash Dec 7, 2013 Presented by: Logan Mildenberger FRC Team 2052 – KnightKrawler www.team2052.com

2. Acknowledgements • Slides by Raul Oliverafrom FRC 111 – WildStang • Presentation from the FIRST Championships in 2008 • http://first.wpi.edu/Images/CMS/First/2008CON_Pneumatic_Power_Olivera.ppt • FRC 358 • Lots of great resources! • http://team358.org/files/pneumatic/ • FIRST Pneumatics Manual • http://www.usfirst.org/roboticsprograms/frc/2012-kit-of-parts-pneumatics

3. What is Pneumatics? • Pneumatics: • “The study of the mechanical properties of air and other gases” • The system on an FRC robot which uses pressurized air to transfer force • Pressure = matter pushing against matter • Object pushing against another object • Absolute (psia): true matter-based pressure • 0 psia -no matter present to press against objects • Not too important in our designs • Gauge (psig): Relative to Atmosphere • 0 psig - pressure in equilibrium with atmosphere • All regulators and gauges based on this • At sea level: 0 psig = ~14.7 psia

4. Calculating Applied Force • Pressure = Force / Area • Force = Pressure X Area • Example: 30 psig in 2” diameter cylinder Area = pr2 = p(1”)2 = 3.14 in2 30 psig 94.2 lbs Force = 30 psi X 3.14 in2= 94.2 lbs

5. Using Pneumatics in FRC • Low to high force applications • Up to 188 lbs (plus any mechanical advantage in design) • Can vary force by changing pressure • Linear and rotational motion • Linear is much more common • Two positions • Great for applications where a motor would stall • Open/close or on/off applications • Claws, lifters, pushers, pokers, levers • Shifters and clutches • Flexible design options • Excess cylinder length can be accommodated in design • Move mounting point • Push against rigid object • Can start match with force applied, and keep it applied at end of match

6. Using Pneumatics in FRC • Relatively straightforward rules and implementation • Mounting hardware included • Easy interface to robot • Can test manually without code • FIRST provides instructions! • Economy of scale – easy to add more later • Easy to transfer energy from robot “base” to manipulator • Flexible tubes • Don’t need chain, belt, or perfectly aligned shafts • All components except for cylinder can be mounted anywhere

7. Pneumatic System Components High Pressure (120 psi) Working Pressure (60 psi) Optional Lower Working Pressure (30 psi)

8. Pneumatic System Components • Compressor • Mount with rubber vibration isolation mounts • Must power with Spike relay with 20 amp breaker (not fuse) • Gets hot! • Pressure Relief Valve (Norgren) • Must be installed on output of compressor • Vents at 120 psi for safety (in case your code to shut off compressor doesn’t work right …) • Must check that this is calibrated properly

9. Pneumatic System Components • Pressure switch (Nason) • Normally closed (compressor runs) • Opens at ~115 psi (code to turn compressor off when switch is open) • Wire to digital input and ground on digital sidecar • Accumulator (Air Tank) • Check rules regarding # allowed • Make sure to mount on high pressure side to take advantage of higher pressure storage!

10. Pneumatic System Components • Primary Regulator (Norgren) • Restricts working pressure to 60 psi max on output side of regulator • Can adjust to less than 60 psi if desired • Make sure arrow points in direction of air flow! • Secondary Regulator (Monnier) • Yellow ring • Allows additional lower pressure circuit if desired

11. Pneumatic System Components • Gauges • Provide readout of pressure in line • Place one on high pressure side and one on working pressure side (can attach directly to regulator) • Plug Valve (manual release valve) • Install on high pressure side • Must be able to release all pressure in system • Must be easily accessed and labeled on your robot

12. Pneumatic System Components • Cylinders (aka “Pistons”) • Donated by Bimba • Order to team specifications from FIRST-specific options • Single or double acting • Single = spring-based return when vented • Double = air pressure drives both directions • Magnetic position sensing option • Solenoid valves (Festo/SMC) • Switches direction of air flow to drive cylinder motion • Connect to solenoid breakout on CRIO • Need a double solenoid to drive double acting cylinder • Can activate manually with blue buttons

13. Solenoid – Cylinder Action

14. Solenoid – Cylinder Action

15. Things to watch out for • Safety • Pressurized air has a lot of potential energy • Follow rules EXACTLY and be careful • Rotation • Difficult to control orientation of the end of a round shaft • Leaks • Can be hard to find – so prevent them with good assembly technique! • Cut tubing straight and clean • Tighten fittings with proper tools • Use methodical approach to narrow in on one area

16. Things to watch out for • Pipe thread wrap • Too much is not a good thing • Leave last 2 threads clear • Avoid getting into valves and hoses • Extra components • Bring spec sheets for non-KOP items to inspection • Cylinders are sensitive to side loads • “Pulling” force is slightly reduced due to area of rod • Large cylinders use a lot of air – make sure your compressor and storage can keep up with expected use • Plug valve must be closed before you start the match!

17. Common Myths • MYTH: Using pneumatics is complicated • FACT: • Simple system with detailed instructions, and it’s the same every time! • Robust system with fewer parts to fail • MYTH: Pneumatics is heavy • FACT: • 2013 compressor is only 2.5 lbs • Could be left off robot to save weight (check rules in 2014!) • Cylinders have high force/weight ratio (compare to CIM+gearbox+chain+speedcontroller…) • Adding a second, third, etc. cylinder is trivial • Plastic air tanks are available • Solenoid and tubing weights are negligible

18. Common Myths • MYTH: Pneumatic cylinders are uncontrollable • FACT: • Flow control valves can slow down motion • Can choose piston length based on geometry • Magnetic reed switches can be used to sense piston position • MYTH: Pneumatics is difficult to program • FACT: • Program compressor to run when pressure switch is closed – connected directly to digital sidecar • Double solenoid consists of two on/off switches – when one is on, other is off!

19. Tips • Use all 24v or 12v solenoids – don’t mix! • Even if you aren’t using pneumatics on your robot, take advantage of the Bimba donation – play with them in the off-season or have on hand for next year! • Solenoids need a minimum pressure (~30 psi) to work. Test your code with pressure in the system! • Clevis pins can be replaced with bolts for more mounting options