View Full Version : When are pnuematics warrented?
02-26-2005, 05:43 PM
Being as our team has very rarely decided to use pneumatics, citing weight, I haven't been able to see the point in FIRST competition where enough pneumatics are used to make the weight of the compressor and such worthwhile. For spontaneous action, pneumatics can't be beat, but for use on an arm or other fine adjustment device, I just can't see the benefit of pneumatics. Does anyone have any thoughts on this, or perhaps an example of when it's worked? I would like to learn how to do variable control pneumatics.
02-26-2005, 05:57 PM
In our first three years in FIRST we did not even touch pnmeumatics because we never found a need for them. Last year though, many teams including ours used pneumatics to lift themselves off the ground and hang from the bar. This year we are using them for shifting our HexaMax R2 transmissions. (http://www.chiefdelphi.com/forums/showthread.php?t=35272) Last year we used a compressor because of the large volume of air needed, but this year we can shift on only one tank of air.
Pneumatics are a good easy way to get linear actuation as opposed to motors which give rotational actuation.
02-26-2005, 06:52 PM
We are using pneumatics a lot this year. Our tetra grabber uses 2, we raise our elevator with 2, we have a brake that uses 1 and an outrigger that uses 1. If we have weight left after official weigh in then we might add 1 or 2 more. They are quick and precise. They can be controlled. They are basically 2 position. Why use motors to go from point A to point B when I can do it faster and exactly correct every time using pneumatics. As for weight, I believe that the gearboxes and motors needed to do the same jobs would be equal to or greater than the pneumatics weight.
02-26-2005, 07:16 PM
Pneumatics are nice for two position action, but for variable control they don't seem to be very capable. I'm thinking however that variable control can be achieved by using two cylinders in parallel, such as with a bicep and tricep. however, when applying pressure to your "bicep" the second cylinder would be applying some back pressure, so that the cylinder would not contract all the way. I don't know if this is what you're using, but it makes sense that it could work.
02-26-2005, 08:14 PM
Pneumatics are usually faster than a motor.
If you need to make some action at the end of an arm or extension, usually a small pneumatic cylinder will be lighter than a motor and gearbox.
With the limitations on the types and number of otors in the kit, sometimes the best option is a pneumatic, so that a motor can be used in another location.
Especially if you just use a charged tank and leave the compressor off, pneumatics do not use much power.
Small pneumatics are great for most shifting transmissions.
Pneumatics are usually the best option for linear motion, because of their speed.
Pneumatics can be controlled for multi-positioning - see several threads on the topic.
02-26-2005, 09:11 PM
We are using our pneumatics as our arm lifter, instead of a motor. They are fast and precise. We can control each and every position and plus they make a cool sound while going up or down :p . And they are very strong.
02-26-2005, 09:15 PM
Once you decide to use pneumatics, you find ways to use them. We used three pneumatic actuators in our TMS (Tetra Management System). It was a lot lighter than putting motors several feet off the ground. They also work fast (tetra grabbers) and have a good power-to-weight ratio.
Most importantly, we have a 3-person pneumatics team that got to design, install, and test them. We had a drivetrain team, electronics team, pneumatic team, game systems (arm) team, software team, and a pneumatics team. More systems on the robot mean more student involvement. It's not just about winning the game.
02-27-2005, 12:35 AM
I love pneumatics, i was kinda bummed i didn't get to work with the pneumatics kit this year with 461 as i was out voted on the idea of using them for something. They are so versatile as already stated and they have alot of great advantages, and now that FIRST has been giving us such a great pneumatics kit for the last couple of years (anyone remember those old compressor the comicly heavy ones...) they are a great addition to many bots.
02-27-2005, 01:37 PM
ever since ive joined our team weve ONLY used pneumatics for our non drive components. just the reliability of having it impossible to burn a cylinder. as with a motor you can is worth it. and how you can have pneumatics stalled with no problems whatsoever is a major plus. and i think direct linear motion is 'simpler' than rotational. espescially since most motors require gearing down, where for pneumatics you only need a triangle with a side being the cylinder. or even just a straight linear motion as seen in many hanging robots last year. and on a personal opinion i think pneumatics are more 'smooth' (after all it is, air 'flowing'). because of the stallable nature of them, most of the time the robot components/frame/etc have less strain on them. well most of the time.
02-27-2005, 04:37 PM
Pneumatics works best when you need two-position linear motion with no stopping between the extremes (extending or retracting an arm, for example). You can vary the actuation speed using the regulator valves provided in the kit of part. When you need multiple random steps within the range of motion, motors and pulleys work best, although (as has already been said) there are ways to achieve this using pneumatics, but they use a LOT of air. Check out this discussion: http://www.chiefdelphi.com/forums/showthread.php?t=23934
and this white paper: http://www.chiefdelphi.com/forums/p...ion=DESC&page=3
This is only our second year, so we are still not comfortable with pneumatics. Also, our primary sponsor is Intel, so our mentors are primarily electrical engineers; they like motors.
02-27-2005, 05:01 PM
My team and i have been going for 4 years now and every year we use pneumatics. The first year we relied more than ever on them when we lifted the whole chassis of the robot off the floor to extend giant treds onto the ground. I reccomend pneumatics to alll starting teams. They are great for all the reasons already mention but also because of durability.
there is ALOT less that can go wrong with a piston than a motor. Electric motors can burn out, breakers and fuses aren;t fun to break but also wearing gears, misaligned sprockets break chains, tensioning chains, proper gear reductions for loads..... there is so much more involved. a piston is easy, in and out... just keep the pressure on and you'll get the MAXIMUM force (if there is anywhere in FIRST that you will find BruteForce, it is in pneumatics!)
Making statements about one system over another with out considering what you need to get done is not helpfull. Attached is a basic spread sheet of air system componets weights are in oz's. Our teams first evalulation is if we need three devices, otherwise the mass requirements don't for us trade off. If you are using two or three speed transmissons that shift with air you at min need storage tanks to precharge. Storage tanks are almost 1 lb each, All things add up. Look at what you need to do and use a scale and a spread sheet to select the best and lightest way to do it.
03-18-2005, 07:14 PM
Pneumatics are nice for two position action, but for variable control they don't seem to be very capable. I'm thinking however that variable control can be achieved by using two cylinders in parallel, such as with a bicep and tricep. however, when applying pressure to your "bicep" the second cylinder would be applying some back pressure, so that the cylinder would not contract all the way. I don't know if this is what you're using, but it makes sense that it could work. Team 614 uses a single piston w/ variable control... the advantage here is much greater reliability and less chances of stripped gears, stuff broken, etc. We have not had any issue with the arm breaking, except for the claws being slightly bent.
The problem is that the weight of the tetras necessitates a large cylinder which consumes a lot of air. Because of this we are somewhat limited on how many tetras we can lift before we run out of pressure (roughly 4-5, though w/ proper consideration of time needed to charge cylinders, this may be extended to 6- once the tetra is above 45 degrees, the pressure required drops dramatically though). Those who have seen us today at the Annapolis regional have probably noticed the slow lifting of the last tetra....
It would have been nice to attach a potentiometer for dialing the angle of the arm for autonomous, but that was deemed unnecessary (which it was, due to having a broken autonomous (now fixed, but unused since not many other robots can do autonomous either, and the benefits are questionable compared to the risks of getting something stuck, since we do not have time for testing).
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