Robot Arm C

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harryk
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Re: Robot Arm C

Post by harryk » November 17th, 2012, 5:00 am

We just started doing this in my Physics C class, and it can become fairly complex. Also, when you're setting up counterweights you also need to remember that as soon as you pick an object up, it will change the balance of the whole system. And if you have more joints further out from the one you're adding weights too, such as a shoulder and elbow, then you should also realize that the balance will change as you change the position of other parts of the arm.
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Re: Robot Arm C

Post by illusionist » November 17th, 2012, 11:56 am

harryk wrote:We just started doing this in my Physics C class, and it can become fairly complex. Also, when you're setting up counterweights you also need to remember that as soon as you pick an object up, it will change the balance of the whole system. And if you have more joints further out from the one you're adding weights too, such as a shoulder and elbow, then you should also realize that the balance will change as you change the position of other parts of the arm.
Yup, I understand that. I brought it up earlier this year as well that the balance changes with rotation of the elbow. Luckily, we don't have extremely heavy objects like D batteries to deal with this year
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Re: Robot Arm C

Post by ohiostar » November 26th, 2012, 7:55 am

Question for anyone running this event at an upcoming invitational, How do you plan to ensure that the ping pong balls will remain in position before the timed run begins? It has been difficult to keep them in place, if someone is walking or just breathing nearby it can cause the balls to roll.

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Re: Robot Arm C

Post by mrsteven » November 26th, 2012, 7:59 am

ohiostar wrote:Question for anyone running this event at an upcoming invitational, How do you plan to ensure that the ping pong balls will remain in position before the timed run begins? It has been difficult to keep them in place, if someone is walking or just breathing nearby it can cause the balls to roll.
The board i made and used to run an IL invites uses electrical tape to mark the north zone and the robots 30x30 square (as the rules say) the thickness of the tapes mades a little 'channel' that the balls seems to stay well in as long as there isnt a fan directly over head.
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Re: Robot Arm C

Post by chalker » November 26th, 2012, 8:09 pm

ohiostar wrote:Question for anyone running this event at an upcoming invitational, How do you plan to ensure that the ping pong balls will remain in position before the timed run begins? It has been difficult to keep them in place, if someone is walking or just breathing nearby it can cause the balls to roll.
Note the rules don't specify anything about the actual surface of the competition area. If you want, you could use a couple pieces of double sided tape to provide a little bit of stickiness for the balls.

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Re: Robot Arm C

Post by jander14indoor » November 27th, 2012, 5:02 am

ohiostar wrote:Question for anyone running this event at an upcoming invitational, How do you plan to ensure that the ping pong balls will remain in position before the timed run begins? It has been difficult to keep them in place, if someone is walking or just breathing nearby it can cause the balls to roll.
Couple of good suggestions already. A comment though, any method used to stabilize the balls in their starting position should be fair (or equally unfair) to all, minimal in overall impact and controlled soley by the event supervisor.

Minimal in impact. Whatever is done should only act at the starting location. So double sided tape should be very small pieces, say 1/2 inch square or less. To maintain fairness for all teams, you may have to replace the tape regularly throughout the day. If you are using a portable board for the competition area, a small dimple at the starting location would be effective and local.

Controlled soley by the event supervisor. Should be self evident, but I don't think teams should be allowed to modify the playing surface prior to the start of the comptetition. Note, this does not prevent them from doing something like dropping a cage over the balls to control location until delivered to the goal boxes as their first action.

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Re: Robot Arm C

Post by mrsteven » November 29th, 2012, 8:38 am

I would think the little dimples would be a good choice to keep the balls in place, but for the double stick tape I feel that that might interfere for some peoples mechanisms to actually retrieve the balls. Since its not in the rules that the ping pong balls are held down by anything other than the force of gravity I wouldnt think it would be fair to those who wouldn't be able to pick up the balls because of it. And its unpredictable whether a supervisor will use tape or not since there is no specifications what so ever on the matter.
If a supervisor taped down the balls on my run I would submit the form to get another opinion
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Re: Robot Arm C

Post by jander14indoor » November 29th, 2012, 10:16 am

Your concern about too sticky tape goes back to my 'minimal impact' comment. An event supervisor could address your concern by having data on how sticky the tape is, and showing it was not the strongest available. Something like how much force was needed to pickup the ball from the tape. And was why I said a small piece of tape to have impact in only a very localized area of the field.

Here's another idea, instead of double stick tape, use a small piece of masking tape (say 1/2 inch square), possibly several layers, with a small hole (1/4 inch or less) in the center. Same effect as the dimple, localized, no 'stickiness' to deal with.

And these are things an event supervisor should try BEFORE a big tournament begins, not implement halfway through a tournament when a problem is noticed. So a good thing to discuss.

And a general comment. Students should be preparred to deal with variability, its part of SO. Most of you are probably thinking of a hard, smooth surface. No guarantee it will be, I've seen this run on a short nap rug, sanded plywood, unsanded plywood, tile, cement, wood gym (some not so smooth!). The smart teams will have tried these variations and be preparred to deal with them.

Thanks,

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Re: Robot Arm C

Post by eox » December 5th, 2012, 3:36 pm

I'm looking to do this event next year, and get a head start.
What should i be studying off of, physics B/C, or other books / websites / tutorials / kits?
Thanks in advance :D

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Re: Robot Arm C

Post by JTMess » December 5th, 2012, 4:24 pm

eox wrote:I'm looking to do this event next year, and get a head start.
What should i be studying off of, physics B/C, or other books / websites / tutorials / kits?
Thanks in advance :D
There's not really a lot of studying to be done for this event. Physics may help you a bit (we ran a lot of calculations before physically building our arm), though the best approach is to design, build, and test your arm. Also, I'm not sure if robot is going to be an event next year since this is its second year of the cycle (if you're referring to the 2014 competitions, that is.

To anyone who has had experience competing in robot in the past, what kind of variation is typical to see at competitions as far as how far away the objects are from where the rules specify their locations to be?
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