Chief Delphi - Minibot Falling Solutions

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- - Minibot Falling Solutions (http://www.chiefdelphi.com/forums/showthread.php?t=90353)

artdutra04

31-01-2011 04:27

Re: Minibot Falling Solutions

Quote:

Originally Posted by JB987 (Post 1012265)

We have considered using a DPDT (4 way?) switch but were concerned about the downward velocity...the question is, could a limit switch (perhaps on a flexible extension) on the bottom end fit within the size limit and be far enough extended to provide a timely stop of the robot likely traveling faster than it did upward? An idea to be tested for sure. Thanks again, Arthur, for your efforts to help your fellow FRC mates!

If you are using two motors, what if you use a two DPDT switches: one reverses one motor to drive it downwards, and the other switch shorts the leads of the second motor to provide drag. We 're probably going to experiment with either partial reverse/motor short or full motor short this week on our Minibot prototype.

JB987

31-01-2011 10:32

Re: Minibot Falling Solutions

Quote:

Originally Posted by artdutra04 (Post 1012280)

Let us know how things work out...we will be trying several methods and will share our trial results also. In the meantime, it would be nice if others would do the same thing;)

buildmaster5000

31-01-2011 12:26

Re: Minibot Falling Solutions

Quote:

Originally Posted by Kevin Sevcik (Post 1011044)

I was actually working this off general body proportions and some fudging for stretching up and standing on your toes. My mostly guesswork formula comes out as Reach = Height * 11 / 8. I'm 70" and I can reach my 96" ceiling standing on my toes, so all of my data points agree well with my formula....

I am 78" tall, but with no shoes I can only reach around 102" while standing on my toes. While the tall person idea is viable, I would want to test it before it was my job to pull down the minibot. Also take into account that you are not right under the minibot, but 12" away from the pole.

JesseK

31-01-2011 12:46

Re: Minibot Falling Solutions

Don't mean to self-quote here, but I had a thought earlier today and put it in the wrong thread.

Quote:

Originally Posted by JesseK (Post 1012355)

Hmm.

What if little lexan slip pads were designed into the MINIBOTs such that when the bots hit the top, the impact forced the slip pads underneath the wheels -- thereby reducing friction with the pole and thus allowing the MINIBOT to slide down the pole? This assumes a cutoff switch is designed into the MINIBOT as well.

...

Quote:

Originally Posted by JesseK (Post 1012422)

Quote:

Originally Posted by pfreivald (Post 1012412)

"Then, it won't so much fly as plummet!"

That's why it reduces friction rather than creating full separation: just how much friction it reduces is completely customizable if you think it through. There's no magic to it; the best way to figure out the balance for a given MINIBOT is to prototype on a specific design. It's better (IMO) than relying on backdriving the motors (though it'd take away the 'innovation' of regenerative MINIBOT falling :rolleyes: ) while also removing the need for other (heavier) concepts (like the NXT + sensors).

J.Warsoff

31-01-2011 12:50

Re: Minibot Falling Solutions

well if you cannot get the minibot to slide down slower, than i would suggest putting some kind of cushioning at the bottom of your bot. As for slowing down the fall, maybe tightening the minibot's grip on the pole enough to create more friction but still being able to move up smoothly or some kind of braking mechanism. Hope this helps guys!

DryLander

31-01-2011 14:14

Re: Minibot Falling Solutions

We are using 2 three-way switches (SPDT) to create an H motor control. We are also using 2 TETRIX on/off switches to start/stop the motors. On our MINIBOT the motors need to turn in the opposite direction but the H motor control reverses both motors. Finally, we are planning on using stainless steel axles to flip the switches and surgical tube to absorb the shock of contact. We are using a latch so the axle does not bounce back and flip the switch again.

Mike Norton

31-01-2011 18:43

Re: Minibot Falling Solutions

G59> TEAMS must retrieve MINIBOTS from the TOWER quickly and safely without special equipment and while standing on the floor after each MATCH. Violation: The FIELD crew will retrieve the MINIBO

what is special equpiment? If you made a second minbibot that you would release after the match to retrieve the mini bot at the top. no need to use a long pole if you have a robot to get a robot.

herrplotnick

05-02-2011 11:38

Re: Minibot Falling Solutions

What is acceptable for a MINIBOT limit switch?

Do you think a DPST plunger type push button switch like:
Digikey Part Number: 679-1048-ND
would be legal?

Would it be legal to activate the MINIBOT with this switch as it is deployed onto the pole?

Dad1279

05-02-2011 11:46

Re: Minibot Falling Solutions

Quote:

Originally Posted by herrplotnick (Post 1016128)

That is a panel mount switch. Doesn't look like, nor is it marketed as a limit switch. Also note the current rating is at '125 v A/C'

herrplotnick

05-02-2011 11:56

Re: Minibot Falling Solutions

The current Rating is 6 AMPs for this pb switch but I assume that is somewhat comparable to a household light switch. The rules specify max a 20 amp fuse so I would think that would be sufficient for current limiting.

Is there anyway I can get a First judge to respond to this?

Also, Is there a detailed list of the Tetrix components on-line? I have failed to find it and I wonder if there is a switch from that list we could use instead.

GaryVoshol

05-02-2011 13:28

Re: Minibot Falling Solutions

Quote:

Originally Posted by herrplotnick (Post 1016149)

Is there anyway I can get a First judge to respond to this?

As with anything else, the only way to get an official opinion is to use the Q&A on the FIRST website. You have to log in with your team ID found in TIMS.

Big Ideas

05-02-2011 13:56

Re: Minibot Falling Solutions

If you are running 2 motors. It is possible to run them at 1/2 voltage (potentially 1/2 speed) by switching them into series connection instead of parallel connection. This cuts the current thru the motors in 1/2.

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