Arms

[Render]

Originally Posted by triggerhappy336

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.

90 pts!

[=Martin=Taylor=]

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.

[rachal]

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.

[fluffy]

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

[Evil Asian]

thank you all for your help

[Dominicano0519]

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

[meatmanek]

Originally Posted by Hachiban VIII

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.

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

[=Martin=Taylor=]

Originally Posted by meatmanek

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.
http://robotics.mcmaster.ca/Videos.htm#pneumatic

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.

[Lil' Lavery]

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.

[Qbranch]

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

[Jimbo5051]

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.)

[cziggy343]

this was done with motors.

[LightWaves1636]

We're motors all the way but we don't do straight motor, we add gears and belts to make the extension and lifts more efficent. Plus it helps to keep everything within size regulations.

[redbarron]

In 2005 we had a robot that was completely pnuematics (except the drive train).We had 4 motions in our manipulator and they were all done with minimal size pistons. The thing I havent noticed anybody mentioning is ratios. Cable & pulley systems paired with a piston can be very effective and in terms of weight compared to a motor with chain beneficial choice. We had an extension, which was moved up and down to get the tetras off the automated loading stations, and then an arm that was fixed on the side of our robot that picked them up off of the extension which was done with a "hooking" action also done with a piston. But unfortunately we overlooked the fact that swinging on a tetra from the side of your robot has disadvantage: lining up on the side of a triangle goal in the center from a distance creates one heck of an optical illusion.

I am not for or against either motors or pnuematics because like its been said you have to look at the advantages and disadvantages toward what you are trying to do in reference to what the capabilities are of each of these, but I just thought that I would point out the option of ratios to overcome the limit of how much extension you get from the piston.

[EricH]

Motors here. We've almost never used pneumatics for an arm. Fisher-Price motors are our motor of choice for lifting things, either by lift (put two on the same winch) or by arm (two on the same sprocket). The only things we use pneumatics for are shifting, the occaisional wedge/anti-tip device ('02-'04), and the occaisional arm extension. (This year, we have three cylinders. One is our grabber power and the other two shift.)