arm design
 

for your arms do you plan on using pneumatics or motors or other?
i ask just to see some of the other ideas out there, we have already designed our arm and i am just curious...

Re: arm design
 

Team 647 will be using a motor powered arm. Also you may want to make this into a poll to be able to view the results easier.

Re: arm design
 

We're using motors, pneumatics are a maybe...

Re: arm design
 

We will be using pneumatics for our arms

Re: arm design
 

ok the poll is in, happy voting everyone!

Re: arm design
 

We are using pneumatics and motors for our arm.

Re: arm design
 

i knew i forgot an option...does anyone know how to edit a poll to add another option? if not select other in this case, also if you select other please state the specifics.

Re: arm design
 

we, team 118, are going with a mix between motors and pnuematics. with a few peices of sugical tubing and zipties to help along the way.

Re: arm design
 

My team, 399, is using motors and possibly pneumatic assist if we see it is necessary.

Re: arm design
 

Motors with pnumatic grabber. I think our robot will surprise some people this year or at least turn heads, both in terms of capability, and in terms of improvement from last year. Overkill would be a nice way of summing it up. =p

Re: arm design
 

The main lifting force is a fischer price motor. Pneumatics though are involved in grabbing of tetras and the on field assembly of our arm(it folds up first.)

~Ian

Re: arm design
 

our team is thinking of using a mix of pneumatics and motors this year

Re: arm design
 

i think pneumatics is simply better, if you are able to make it stop where you wanted. becasue motors may fry or brake down, and pneumatics are simpler to intsall, but if you are building a arm that move only by pneumatics, you will run out of air quickly.

Motor+Pneumatics

Re: arm design
 

we're by passing pneumatics all together............too heavy for simple single use applications.

motors and ingenuity for us!

Re: arm design
 

pneumatics are more powerful but its an all or nothing solution. you can't stop them halfway through, so if a tetra is just out of place then it may be difficult to pick it up

Re: arm design
 

I agree with Zippiot. While pneumatics are easy to do and install, its all or nothing with them. In or out, not halfway. Motors allow that option. And they don't just randomly burn up or catch fire. Only if they are overworked/ overstressed. You just need to check the loads on them. Plus, pneumatic tubes can get pinched. In addition, what happens when your air tank runs out? You have to wait for it to reload. And in a game where defense is key, that could cause you capping points. Just some words for thought...

Re: arm design
 

Whatever happened to the method in which you could stop a pneumatic cylinder anywhere you want to. Can you still do that?

Re: arm design
 

Team 637 is going with a motor driven arm. yet no articulation.

Re: arm design
 

We have a single jointed arm with a second joint controlled by a four errr... three link. The whole thing is mounted on a stationary tower and folds up nicely inside it. On the end of the arm we have a pneumatic gripper somewhat akin to a stuffed teddybear grabber from hell. The arm will probably be powered by two fp motors if anyone ever takes the initiative to design a gearbox for them.

Re: arm design
 

keke, we are goin all the way with ours, pnumatics, ball screw, and gears. every section and pivot uses a diffrent one.

Re: arm design
 

we're usin pneumatics and motors for our arm

Re: arm design
 

our arm is made out of carpet

Re: arm design
 

We are using pneumatics and something else but it is a secret, lol

Re: arm design
 

This is our last area of design need. A multiposition pneumatic would do the job just perfectly. Barring the use of a second solenoid to meter the exhaust, it is not possible. To be able to use the metered exhaust will likely require a human touch that an auto program cannot handle consistantly.

I did have an idea to gang two cylinders in series. Have something like an 8 inch throw connected to a 12 inch throw gives you four positions. All in, 8 out only, 12 out only, all out....


Anybody considering something like that? Our engineering crew is meeting with the students on Thursday and then we have a Saturday build session planned where I hope to put the wraps on this last design item. :ahh:

Re: arm design
 

its actually quite simple to make a pneumatic cylinder that can stop at any point. all you need to do is attach another solenoid to the exhaust of the cylinder's solenoid. it's very hard to describe, and i may draw up a pic in the next few days, but essentially u make it so that at any point in time you can cut off the exhaust of the cylinder, so both sides will fill with air, effectively stopping the piston in its place (or very close to it). but the purge can be very violent, otherwise all you need is enough buttons to manage it. if this was too complicated i can try to make it more clear just ask.

Re: arm design
 

another way to make multiple points of stop for pneumatics is to use many tiny stroke pistons. this is expensive and complicated but it is just as strong, can be much faster (instead of slowly filling 1 large piston you can slowly fill 2 small ones, tripling or doubling the speed depending...). the only issue is keeping stability constant, to do this i recommend a sliding arm action, and i haven't seen a design of that yet that doesn't compromise the integrity. a good part about pneumatics is that, for what i know, there is no limit to how many pistons that you can use, the only issue is how quickly it takes to charge them all. problem is that generally speaking pneumatics are much heavier, considering the pistons tanks compressor tubing and connections.

Re: arm design
 

and i urge you to share your arm designs, but if you wish to keep them a secret to prevent others from copying them post them later into the build, i don't want to have to see them in the competition (j/k i just am interested to see what everyone came up with)

Re: arm design
 

i just don't understand how you all are going to get the necessary travel out of a pneumatic? Does anybody have any examples how they are accomplishing raising a tetra a pretty large distance using a pneumatic?

Re: arm design
 

How did they do it last year with pneumatics.....? ;)

Re: arm design
 

pneumatics are simple, its all about levers. the closer to the pivot point the piston is mounted the more travel u get, but the more power it takes. one thing that can be used to combat this is to link multiple pistons to the same point, 1 2" piston can lift 80lbs, image 2 of them. 1 tetra on the end of a 3-5 foot arm doesn't weight more than 160 lbs (with the lever exchanges in weight and all). i am a huge fan of pneumatics but for something that needs to be able to move as versatilely as would be required this year motors seems to be the way to go (a gear ratio can be your best friends when a 4 foot arm can be swung All the way around holding an 8.5 pound piece of pipe in less than 2 seconds seems about right). but i am sure that people will make it work. the best of both worlds would be a mix of motors and pneumatics but weight comes into issue there (our bot should be 7-23 lbs underweight, but i am sure that we will be right around 130 when completed)

Re: arm design
 

I agree with you generally. But it also depends greatly on a the complexity of your movements. In most cases using pneumatics that stop midstroke are similiar to dead reckoning programming. With adjustments and fine tuning you can get good results for simple, broad movements. But for complex, precise movement you are generally out of luck.

An example of this was my teams 2003 robot. We had two cyclinder lifting our stacker. As part of our autonomous we would lift our stacker part way up. It came to the same position almost everytime. But it wouldn't work well it if had to be precise.

This is where some design comes in. IF you design a robot that is able to pick up tetras with broad movements, you would likely be able to tune a program to do it in automounous (thinking about things like air pressure, piston speed, what the tetra weight will do). If it must be precise in it's movements (move two inches, then one inche, and so on) it will likely be hard for autonomous and equally so for the driver's and any programming in user mode.

Re: arm design
 

an interesting thing that i designed and tested was a joystick controlled regulator with psi relief valve. the more forward i moved the joystick the more pressure was allowed in, and if i back out the joystick pressure would be relieved. this made it so that with a load on the piston you can precisely position it where you wish, but it takes some practise.

Re: arm design
 

Ok, Here's My $0.02:
Alright, First off, Our Team is Using Pneumatics All the way. ONE Piston for our uber-cool arm. :p
To give you an idea of the range we can accomplish:
-The Arm Fits within starting size (duh)
-The Arm will utilize Mid-Stroke Positioning (This is "Stopping the piston in between fully out and in") The Mid-Stroke Positioning allows us to stop our arm at any point between retracted and extended. We developed a system in 2003 which also allowed us to do this with our staged forklift, and for those who shun mid-stroke positioning to be "inaccurate", I will try to have some pics or video for you to see how "inaccurate" it is ;)
But anyway, for those interested, the "basic" way to stop the piston mid-way is to block the Exhaust output from the solenoid controlling your piston.
Do a search and you'll quickly find more info on the subject.
Back to our Arm!
-It's capable of "grabbing" a tetra on the ground and capping it onto the center goal, up to 2-3 tetras on Center
-It stacks one at a time (Which I know many of you out there are stacking before hand ;) )
-It can stack 5-6 Tetras on the "Standard" goals
-Our arm will weigh approx. < 20lbs, Including the Four ~4.5 - 5' Counter-Support beams spreading across the chassis.
-The "grabber" section of the arm extends from 8" to 10'4" from ground level.

Now, to be fair, here are a few issues we may see developing with our arm:
-Lack of Air (I'm not too Worried about this one, by the looks of our Pneumatics Board, but always something to look out for! Especially with our Pistons...)
-Tipping (Once again, we've put alot of work into maintaining our CG in our Design, plus its simple and small (surprisingly, yes), so I'm not at worried about this yet either. We also do not extend our arm out very far outside of our robots x,z axis size (38x28)

I hope to have more Info up soon, but for those interested, here's a GIF of a (much) older model of the arm in motion:
http://www.raptar.net/ArmAnim.gif
(This was made a while back, much changes since then ;) )

Hope the info helps!