I|\/|age |)iscuss: Team 694 Stuypulse!

FIRST Robot Showcase
1

)Got some pictures of my teams robot posted up here at chiefdelphi, here are some links:

The chassis: http://www.chiefdelphi.com/forums/pictures.php?s=&action=single&picid=3861&direction=DESC&sort=date&perrow=20&trows=10&quiet=verbose

The arm: http://www.chiefdelphi.com/forums/pictures.php?s=&action=single&picid=3862&direction=DESC&sort=date&perrow=20&trows=10&quiet=verbose
The arm from the other end: http://www.chiefdelphi.com/forums/pictures.php?s=&action=single&picid=3863&direction=DESC&sort=date&perrow=20&trows=10&quiet=verbose

And the great people who made it happen, or not ;): http://www.chiefdelphi.com/forums/pictures.php?s=&action=single&picid=3864&direction=DESC&sort=date&perrow=20&trows=10&quiet=verbose

I think i said i would post exact specson the arm, so here it goes ^_^.

Joint 0(at the robot base):
Driven by: A fischer price, geared down twice for an 8 to 1 ratio i believe. 12.5 or around that rpm a minute
90 degree rotation: 1.2 seconds at full blast(theoretically, we’ve never actually driven it full speed.) In otherwords VERY FAST.
strength: 9 feet: about 15 pounds, so thats the arm and a box
7 feet: about 30 pounds, a small stack of boxes.
5 feet: 60-70 pounds, the biggest stack you can get.
2 feet or less: 100-200 pounds, or a robot. :slight_smile:

Joint 1(in the middle):
Driven by: a fischer price, geared down once for a 6 to 1 ratio i believe.
90 degree rotation: 0.9 seconds. Its hard to test the actuall speed of this joint becasue we’re afraid of it ripping itself apart. The programming still needs some work. Also the ceiling has been causing us some problems. :slight_smile:
Strength:
5 feet: 50-55 pounds, a 8-9 high stack
1 foot: way too much, or your robot :slight_smile:

Joint 2(the grabber):
driven by: A globe geared down 5 to 1.
90 degree rotation: is around 0.8 seconds Its faster than the other two, and just as they were really fast, this one is too.
Strength
1 foot: 40-50 pounds. This motor has to hold the whole weight of a stack. If it fails to hold it then it will backdrive so it limits the height of our stacks to 8 high.

The grabber is penumatic controlled and can grab boxes in any orientation. We can really only deal with ones that are rightside up, upside down, or on one of the two smaller ends. Then we can grab them and stack them upright pretty quickly.

I mentioned it autolevels and so forth. All i have to say is, RAGE watch out ^_^!

The rest of the robot isn’t bad either. We’re pretty nimble with our two speed vector drive. It only has two powered wheels unfortunatly but those are powered by the bosch. Also we can throw most of our weight onto them by positioning the arm so we should have pretty good traction to push other bots around. We can of course drive in any direction or do neat little arcs to maneuver around boxes to get them in the correct orientation quickly for our arm. I don’t think traction will be a problem. We’re using the pneumatic wheels from skyway. Absolute beasts on the mesh, the carpet and the HDPE.

We’ve got that cavity in the middle to protect boxes. We just drive around a stack to protect it. I bet we’re the only team to stack, limbo and have room for boxes inside us. Its been suuuuuuch a pain to fit everything in. (we’ve used all but 3 motors, and two of those will probably make it if weight allows, and pneumatics :))

Lastly we can limbo by laying the arm down although its pretty tight ;). Hopefully it really will be the hieght they said it would be and not the height they said it could be. (if not i guess the tires could lose a bit of air :D)

I can’t think of anything else you might want to know, but i’ll tell you if you ask.

2

There is some really cool stuff in that arm if you look at it closely. Output shafts for some functions are also being used as idler shafts for others. This leads to nice packaging, but requires a lot of forethought so that the chain lengths work out properly (I don’t see any hardware for adjusting chain tension, is there any?). Nice job!

We have always used a sliding middle joint on the Bobcat because it is easier to control, but the rotating middle joint does give you more flexibility. Your drivers (and programmers) will just have to be careful with the CG.

As for the specs - they seem to rely on the stall torque of the motors. In order to actually move stuff and avoid tripping breakers, the loads will have to be somewhat less than the ones quoted. Still looks like there is enough torque to get a lot of stuff accomplished though!

Great Job! Hope to see it up close at one of the competitions.

Good Luck,

P.J.

3

Yeah those strengths are based off the stall torques but i’m pretty sure it can lift a robot because it lifted itself. The first time we turned on the arm two people were holding onto the arm and since the programming was screwy some bad things happened. Basically it just thrashed and practicacally pulled out one of our mentors arms. Of course they held onto the arm so the rest of the robot rotated around the main joint throwing the robot off the ground AND FAST! It all happened in under half a second so i’m pretty sure strength won’t be a problem ^_^!

As for those driveshafts, i planned it all out to be mounted on seperate shafts to make it easier to work with. One of the builders did that against our planning :wink:

Tensioning is a slight problem. We do have a tensioner that slips in but its sort of an add-on not a well thought out thing. It sort of works. Otherwise we just made the chains as close as possible to the needed lengths using offset chains where required. the chains running up the arm have some really cheesy tensioners that i made in about 5 minutes. Velcro on then zip tie lexan forks! :slight_smile: (no bolting, drilling or shedding of aluminum was used in their creation ;))

4

Those torque values may be right, which they aren’t, but they certainly aren’t practical.

Another bot will never be on the 2ft section of your arm because then your entire arm would have to be under their robot. That’s not gonna fit under most robots…

Not to mention, even if you get it under a robot, as soon as you lift, that arm is so wide it will lift their entire robot off the ground, which is a violation of the rules. You can only lift part of a robot up, and not the entire thing.

In the end: Your arm can only lift 15lbs.