So I was looking at 971’s season highlights for 2019 and was interested in their vacuum system.
What kind of suction pump was used and how did they eject game pieces?
How were the suction pads made and what materials were used to make them?
What would you change in your vacuum system?
My team used a vacuum last year for suctioning onto the hatch panel. What we did was bought a mini portable air compressor replaced the motor for an FRC legal one and then just reversed the polarities.
971 used iirc 4 (5?) of this style of pump all inline and driven by a 775pro. Most other teams also used either that or a vane pump. If you search around a bit on here you’ll fine out more about the suction cups, which were slightly modified COTS products.
This pump is the first result on amazon, and it looks similar to the photo in their Spartan Series video about their robot.
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Near as I can tell 5826 is the only team that went with two vacuum systems. One for disc and one for ball. For the flat, even surface of a disc a high volume, low suction system works. Basically a shop vac motor but Armabot sells a nice kit. For the ball, well that’s harder. We ended up finding an old Gast model vane pump. Some kind of laboratory suction iirc. We had to jump through hoops to get it cleared. No reversing the vanes, limited the rpms, made a custom polycarb trap in case the vanes blew up. It was a most excellent learning experience. But practical? Eh. Any voltage drop, like when running too many systems at once, made for drops. Also, there was some transient glitch when the field control system went from sandstorm to normal play that sometimes glitched and made for a drop. So, mondo cool but not, with the time we had to build it, reliable. A nice video of the two systems in ver 1.0 mode if it interests you.
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Nice drivetrain (I know its not the point of your video but I was really good)!
SgtSpork
Thank you. Nice of you to comment on it. 5826 is an unusual team. They decided to build that H-drive on day two of Build Season…having never actually examined one before much less done one in the off season, and not having the needed parts. Similarly with the two vacuum systems, I understand they got the idea when somebody brought a new shop vac on day one to be used for cleanup. They just got to tinkering with it and things got out of hand.
For us the build season was not six weeks, but more like 5 due to weather. Oh, and our entire programming team skipped week five and went on a band trip to New Orleans. Pretty much a text book case of how not to do things in a FIRST build season!
I’m reminded of the famous Samuel Johnson quote regarding a dog walking on its hind legs:
“It is not done well, but you are surprised to find it done at all”.
Although to be fair it actually did work well other than the glitches mentioned above. But cycle speed? Uh…maybe consider a wheeled intake?
They said that was too boring.
I’d mention them for up and coming teams in Wisconsin but frankly even as lead mentor I have no idea what they are going to do. Perhaps the team decision to only attend one regional this year so we have more resources for off season work should be a clue.
TW
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Now that’s what I call an adventure!
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This would be the 1 second of Disabled between Autonomous and TeleOp. Sandstorm was still Autonomous as far as the FMS was concerned, but joystick entry was allowed through during that time.
And, to be clear, for at least the past few years, this is the expected behavior of the field.
Robots must be designed to account for the brief disable between auto/teleop.
Yes. If you have a game element gripped in a wheeled intake this is a non issue. If it is held on by suction…well, yet another reason why suction devices are seldom used in FRC. Whereas in industry they are pretty common in material handling. By saying it was a glitch I did not imply that it was anything new and/or wrong.
And so we learn…
TW
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We had that very concern last year, we thought that we would drop the hatch between sandstorm and teleop.
During the practice match setup on the driver station at home, we would put in a 1 second delay in between periods. It would result in dropping the hatch. On the FMS field we were able to hold the hatch between periods. Not sure the exact reason why, but it held on.
125 went super deep on suction for game piece holding/manipulation this past season. We carried it as an option all the way up to bag day. We were attracted to it for a few options, first and foremost meaning a very light manipulator. The PC Hatches were just asking to be suction cup’d…
Deep in our back pockets we’ve had the ‘turn a pneumatic cylinder into a vacuum pump’ trick ready to go. When we strongly considered trying it for game pieces, we decided to fab one quickly so we could get to prototyping. We used a NEO/Spark (because of the USB interface allowing easy speed control), a 1-1/16" x 3" stroke bimba cylinder and some printed parts.
It was pretty amazing! We calculated the rough CFM to be about 4, which is a large amount of air to move for a vac pump. With a vac gauge we measured 25-28 in-Hg of vacuum which was pretty promising. To make the system work we needed to use a series of check valves to stop flow, and it pretty quickly started to get confusing, so we made a little block diagram for ourselves to document what was working.
The thing that really kept us going on it for most the build season was how damn good it was at Hatches. It was extremely forgiving on off axis alignment. Our little proto wood bot was off and running with very little work, which tends to be a good sign for a mechanism.
With some tweaks, we modified the suction arm to have 2 positions with a pneumatic cylinder. Flat for hatches, and an angled option to grab Cargo with two suction cups. With some tweaks to the suction cup (foam on the lip) we were able to grab cargo quite quickly - a big help from the large flow rate the cylinder was generating.
One thing we knew we had to solve was “releasing” the game pieces cleanly. The easy way to do this was with a short timed burst of air into the suction line - however we found ourselves in an internal debate…was a suction cup a ‘pneumatic device’.
Essentially, there was an argument to be made that you were putting ‘compressed air’ into an unrated mechanism (the suction cup). The counter argument to this was that as the cup reached atmospheric pressure, it would just ‘release’ and you wouldn’t be able to pressurize air. The counter counter argument to this was that if the Hatch was up against a rocket or scoring area, you could pressurize the cup only to the point of the suction cups lip deflecting and then bleeding the compressed air. It was all very silly, but then again, these are the rules and choices all teams have to contemplate when making design decisions.
The solution to this were “AQR” valves made by Piab. https://www.piab.com/en-US/products/suction-cups/suction-cup-accessories/suction-cup-valves/aqr---atmospheric-quick-release/
They’re pretty awesome little devices. Essentially you apply compressed air to the valve, and as long as you do its shut and vac can generate. If you remove compressed air, it ‘pops open’ at a rate of 7CFM to atm and lets the cup release what its holding. Ideal for our application (demo below).
Below is an image of the ‘Suction End’ of the system. You plug in 1 line from the vac pump, 1 line from a solenoid (for the AQR release) and 2 suction cups. This was hidden up inside the little prototype suction grabber.
Overall, we moved away from this system for 2 reasons. First being we were unable to hold a Cargo well enough for us to feel comfortable under heavy defense. We could manipulate and score Cargo without an issue by ourselves, but if other robots were colliding with us, we would lose grip and drop the Cargo. 971 solved this problem very well by making their suction cup extra floppy. By holding onto the Cargo in 2 places, we were awesome in one axis, but poorly performing in other axes.
The second reason was the handoff to the suction cups for Cargo from our floor loader. Again, it was something we had working well in our own lab, but felt like one of those issues that would be a bear to deal with in real play. We ultimately went for the more widespread wheel grabber, and I think it was absolutely the right call for us.
That being said, we learned a ton about suction systems and would be happy to deploy our research onto new stuff in the future. I leave you with one of only images I have of the full bot with the prototype suction grabber on it.
-Brando
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Brandon
That is seriously cool.
TW
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I’ll take “things that weird out robot inspectors” for $100, Alex.
You’ve clearly taken pains to think through the rules compliance, but I would love to be a fly on the wall during the LRI discussion that would be sure to ensue!
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I think we got the legality side nailed - but it would definitely take a bit to explain the system to an inspector unfamiliar with the system, or vacuum/pneumatics beyond just a general awareness understanding.
It was actually one of our students who went off and started the block diagram with the idea of having to explain this to an inspector in mind.
I made 100% sure the students that would inevitably explain the suction system an an inspector never used certain words, as 971 didn’t have a pneumatics system on the robot, and the solenoids used were <10 watt electrical solenoids, not pneumatic solenoids, to enable larger fitting sizes, etc.
Suction was fun,
-Aren
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Looking at this diagram I have a couple questions. Do the check valve arrows mean the direction air can go or the direction air can’t go? Since if it’s the direction air can go, then I don’t see how the cylinder would vent to the atmosphere.
What do you mean by “do its shut and vac can generate”? I don’t see any compressed air entering the system in the video which is how you said these valves work. All I see is someone turning an exhaust valve.
As for this setup, I can understand that the two tee-fittings on the right are where the suction cup attaches to. On the left is a tee-fitting and a y-fitting. To which one does the vacuum pump attach and to which does the solenoid. What exactly does the solenoid do and how is it setup?
As far as the suction cups go, where did you purchase them from and how did you install fittings onto them. I was on SMC’s website and was confused how fittings would be attached to them. How did you choose what type of suction cup you needed?
I know these are a lot of questions but suction is so cool. It is also very confusing.
This is the confusing part, because ‘you’re creating vacuum’ I think your mind tends to think that the ‘thing you’re creating’ is what you’re trying to quantify. So when you start quantifying it with a diagram that depicts the actual flow of air, its all backwards for vac. I suppose this is probably NOT the smartest way to draw this out - the arrows with cross out marks represent direction air cannot flow. It was labeled like this because it tended to be the easiest way to think about it when someone was trying to build the system with physical parts in hand (which way to assemble each check valve).
Wow terrible grammar on my part. I was trying to say “…and as long as you do, it is shut, and vac can generate.” Essentially meaning it will hold the valve shut (vacuum will generate) as long as 60psi is applied.
The demo was quick and dirty - the release valve was T’d into a regulator/compressor and quickly charged before the video started. The video just depicts what happens when you remove the 60psi from the valve. Saying more clearly - there is no vac pump in the video, the suction cup is just manually pressed AND 60psi is applied to the system - then the 60psi is removed and the suction cup lets go.
The T fitting on the left goes to the vacuum pump. The Y fitting on the left goes to the pneumatic solenoid. The solenoid just applies the 60psi to the AQR so that the valve is shut. You leave the solenoid ‘on’ through game pieces acquisition and the entire time you hold it. When you’re ready to let go of the game piece, you fire the solenoid and release the 60psi.
The blue suction cups were from Mcmaster, because we could get them fast, and because Mcmaster is the best. The science applied to selecting them was essentially to choose some with multiple bellows, would fit on a disc surface (in the places we wanted to use them). We ordered 2 sizes figuring we would try both, and then ended up just using 1 of each size in the final gripper (with the larger for the main Cargo grab because it gave more holding force).
The red suction cup in the AQR video is from Piab. We talked to their application engineer and ended up getting a recommendation from them on material for the cup. Piab has a billion options and their engineers were really excited to help us out, so I have to give them a big recommendation if you decide to look at suction cups in the future.
For fittings, the cups all NPT style threads, so we just chose the right size, added some teflon tape and screwed them together.
Happy to share our insights, feel free to ask more questions now or in the future if you think of anything.
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Pneumatic on my wrist