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Unread 05-01-2015, 10:37
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Question Picking Up Upside-down Totes?

For the past couple of days I have been hearing mutterings from my team (STEMpunk 4531), as well as from many here on Chief Delphi concerning the difficulty of picking up an upside-down tote as compared to one found rightside-up. So to put the speculation to rest I ran a few experiments 10-12 times each, and determined quite reliably that at a contact pressure of no less than 6 pounds, any arbitrary end-effector should be able to grip the sides of an upside-down tote so long as the friction coefficient between the surface of said end-effector and the plastic walls of the tote is made equal to or greater than the coefficient between plastic and a pair of sweaty boy hands.

I didn't even need a calculator for this one, but if anyone else has a spread sheet or a graph or something showing exactly what it takes to grip a plastic bin at varying distances and with different materials, I would certainly like to see it, even if I wouldn't necessarily make one myself.

Now, of course there are other problems involved with upside-down totes aside from simply picking them up. For example; How do we flip them right side up for stacking quickly and efficiently, why not stack them all upside down, and how do we get our robot to recognize and accept both orientations in auto or even tele-op are all tricky issues and I would love to hear what you guys have to say about them!

Last edited by Deucalion : 05-01-2015 at 11:38.
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Unread 05-01-2015, 11:30
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Re: Picking Up Upside-down Totes?

We figured that a tote-flipper would be more sensible, since a right-side-up tote is a lot easier to deal with in the robot. An arm that grabs the far top edge of the tote and pulls it towards the bot while driving backwards would achieve the job.

Actually, we figured that it's probably not necessary for playing the game pretty well. It might be needed to win CMP, though.
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Unread 05-01-2015, 11:34
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Re: Picking Up Upside-down Totes?

Thanks for testing and making your first post to Chief Delphi a good one

Could you describe how you measured the 6 pounds of force?
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Unread 05-01-2015, 11:36
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Re: Picking Up Upside-down Totes?

Do you really need to? There's enough that are right side up. Perhaps it would be easier to just move the upside down ones out of the way.
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Unread 05-01-2015, 11:40
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Re: Picking Up Upside-down Totes?

If there were only 2 possible orientations of the Tote, then only stacking like totes is an easy solution.

But, you still need to figure out what to do with totes laying on their side.
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Unread 05-01-2015, 13:16
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Re: Picking Up Upside-down Totes?

Quote:
Originally Posted by rich2202 View Post
But, you still need to figure out what to do with totes laying on their side.
You could just have a little arm with a spatula-like thingie on the end of it.

Here; I made a picture:
PICTURE
(yes, I am a bit bored. How did you know?)
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Unread 05-01-2015, 15:05
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Re: Picking Up Upside-down Totes?

Quote:
Originally Posted by nxtmonkeys View Post
You could just have a little arm with a spatula-like thingie on the end of it.

Here; I made a picture:
PICTURE
(yes, I am a bit bored. How did you know?)
Your pic is for flipping over an upside down tote. My question was for a tote laying on its side.

Also, your design assumes enough friction to keep the tote from sliding, and that there is room behind the tote.
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Unread 06-01-2015, 08:25
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Re: Picking Up Upside-down Totes?

Quote:
Originally Posted by Michael Hill View Post
Do you really need to? There's enough that are right side up. Perhaps it would be easier to just move the upside down ones out of the way.
Yeah, that's what my team was saying. One of the people on my team did the math and he said the max points you could make not including time is 408, and those upside totes only count for like 20 or something like that, so it probably won't be significant when you have more than enough right side up totes. They may become more relevant in Nationals, and by then you'd have more time to make changes so that you could deal with the upside down bins. I'd say they aren't very relevant unless you're with a team that can quickly and efficiently stack all totes and bins so that you'd actually need the upside down ones. 10 out of the 64 totes are upside down, I don't think they'll really need to come into play till nationals, or if you really need points on your average (since you don't win individual matches till eliminations) or wanna go try hard mode.
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Unread 19-01-2015, 22:30
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Thumbs up Re: Picking Up Upside-down Totes?

Ah! The gravity flip certainly is a fine idea, I must say. The only trick here is implementing it on the fly.
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Unread 05-01-2015, 11:56
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Re: Picking Up Upside-down Totes?

Quote:
Originally Posted by Steven Smith View Post
Thanks for testing and making your first post to Chief Delphi a good one

Could you describe how you measured the 6 pounds of force?
Honestly, it was a complete guess and the although I did actually run the "experiments" 3 different ways 10-12 times, the entire post was laden with dry humor and mild sarcasm. Really, that was just what it felt like to me as I picked them up and set them down, BUT I did go and check the friction coefficient between skin and plastic, and it looks to be ~0.98 as described here -> http://hypertextbook.com/facts/2005/skin.shtml for dry skin. Given this and the weight of the totes at 7.8 pounds you can deduce that to grip the sides with dry hands you would need about 7.9 pounds of contact pressure, maybe a bit less with sweaty hands, so I wasn't too far off the first time when I said "no less than 6 pounds"!

Last edited by Deucalion : 05-01-2015 at 12:06. Reason: grammar error
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Unread 05-01-2015, 11:56
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Re: Picking Up Upside-down Totes?

If only we could find a COTS source for human skin!

(looks like we'll have to settle for phone grippy things)
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Unread 05-01-2015, 12:02
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Re: Picking Up Upside-down Totes?

A tote flipper is not at all a complex or challenging thing to make. Look at Stack attack for ideas
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Unread 05-01-2015, 12:14
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Re: Picking Up Upside-down Totes?

Quote:
Originally Posted by stinglikeabee View Post
A tote flipper is not at all a complex or challenging thing to make. Look at Stack attack for ideas
Stack Attack was more about knocking totes down than stacking them up. The human players did most of the stacking.
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Unread 05-01-2015, 12:42
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Re: Picking Up Upside-down Totes?

Oh, and what about picking up the recycling bins, if you ask me, anything that can pick up one of those should also be able to deal with the totes pretty easily.
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Unread 05-01-2015, 13:10
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Re: Picking Up Upside-down Totes?

Quote:
Originally Posted by Koko Ed View Post
Stack Attack was more about knocking totes down than stacking them up. The human players did most of the stacking.
That's not true for all teams, but we'll focus on this game.
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