Arms
 

in the passed year is there some thype of arm you use????????? and is it better to use air Lines to run the arm???? or motors in the kit?????

Re: Arms
 

This year our team used a 2-segmented arm where the 1st part "tower" is attached to the chassis and the 2nd piece is rotated using the globe motor.

Now by air lines i'm guessing u mean pneumatics? well, we didnt use pneumatics this year but on our '05 robot we did. Then, we had a 3-segmented arm where the second piece was elevated by a large pneumatic piston, then the third section was rotated using the van-door motor (we didn't get that this year :( ). The thing with pneumatics is that they can only go fully open or fully closed, there is no middle ground like with hydrolics. So if u only want your arm to go to a certain position then pneumatics would work but otherwise i'd go with motors. Also pneumatics are heavy (u got the compressor, all of the regulators, hose, at least 1 tank, and then the pistons) so you'll need keep that in mind as well.

Re: Arms
 

We used pneumatic's. We used pneumatic's for allot of stuff. Once we threw the compressor on we figured we might as well get the most use out of it. Which is pretty cool cause I like pneumatics.

So I'm pretty biased, I say it's better to use pneu than motors.


If they would let me, I would have our bot be a hover craft off that compressor. That would be wicked

EDIT: Well for our arm extention we used motors, that's a good way to go. As the above poster said you need middle ground for the extention. Plus I don't think they're are pistons big enough to go to the top leg.

Re: Arms
 

90 pts! :p

Re: Arms
 

Over the years we've done both pneumatics and motors.

We haven't had much luck with the pneumatics. The compressor barely squeeks out enough air to run an arm an entire match. To get enough air you have to add more cylinders, which adds more weight. The Kop pneumatic conectors are also unrelaible, which leads to leaks and the loss of more air.

Motors have their own problems: backdrive, breaker blow-outs, and (in the case of the Keyangs and windows) cracking plastic gears. However, electons don't tend to leak out, and the battery isn't part of the wight ;) So you don't have to worry about losing power.

Another major problem with pneumatics is that they are not linear. The actuators have only two positions -extended and contracted. Pnemuatics are not good at raising an arm precise amounts.

Re: Arms
 

We had a lot of success with pneumatics on our grabber in 2005 (which was extremely heavy and coupled with a fairly robust elevator). Admittedly, we had to cheesehole off about 10 pounds because of the extra weight from the pneumatics, but it worked really nicely.

We were originally going to use pneumatics on this year's grabber as well, but our jointed arm couldn't handle the torque caused by the piston on the end so we switched to a globe motor.

Re: Arms
 

we have two pistons for the grabber
and a globe for raising the arm
giving us the best of both worlds:)

http://www.chiefdelphi.com/forums/sh...threadid=55336

Re: Arms
 

thank you all for your help

Re: Arms
 

we used motors and a very elaborate pulley system or the arm

Re: Arms
 

Yeah, I've been thinking about that. I think with creative use of solenoids, valves that restrict airflow, good sensors, and nice code, a team could manage to make a pneumatic servo that used minimal air. The more I think about it, the more possible it seems.

Here's someone who's done it:
http://robotics.mcmaster.ca/Videos.htm#pneumatic

Re: Arms
 

I too have heard about people pressurizing both ends of an actuator to operate it linearly. But getting this to work would be a lot harder then using a motor.

Re: Arms
 

It all depends on the precise tasks you're trying to accomplish. I'll cover some of 116s arms I'm familiar with.
2001- pneumatic shoulder joint raised arm from folded position into scoring position. Motor controlled elbow and wrist joints. The gripper was also actuated by pneumatics. Placed large balls on goals, as well as folded up to fit under the bar.


2004- Globe motor powered shoulder. Pneumatic extension. Pneumatic gripper. Could place large doubler balls as well as hang on bar at end of match.


2005-Window motor powered winch. Pneumatic extension created lever for winch. Pneumatic gripper prevented tetras from flying off of arm. Arm could manually load tetras and score on any goal.


2007- 2x Globe motors power shoulder. Pneumatic wrist actuation, and pneumatic gripper. Surgical tubing powered single-time extension (fires when disengaged from locking mechanism at beginning of each match, then locks in extended position). Picks up tubes from ground and scores on all 3 levels of the rack.

Re: Arms
 

Just as a rule of thumb... motors, because of the small compressor, tend to be faster at actuating manipulators n such, just because of the low cfm of the thompson compressor. We had a pneumatic actuator on our tetra bot... and it did slow us down some.

This year... motor drives on the elevator.... bottom to top (top row score) about 1.5 seconds give or take :ahh:

Re: Arms
 

We used little BaneBot motors with a planetary gearbox, it seemed to work fine except when we tried to use them with the up/down part of the arm (we burned up 2 Banebots.)

Re: Arms
 

this was done with motors.