08-12-2008 09:01

JesseK

Re: pic: OH GOD! WHAT HAVE I DONE???

It really depends on where you have to pick up the game piece from, but I have an idea. For easier driver control, you could make the first arm coming off the large bottom sprocket a 4-bar linkage. Adds a bit of weight and slight complexity for mounting the next joint. Yet you essentially add another option in control the driver without having to add sensors, button, or more programming. This wouldn't work if you had to pick something up off the ground, unless you telescoped the arm out (tradeoff in complexity I guess).

At 70 inches long, we really couldn't make a suggest for the reduction until we see a game piece. For instance, this would be perfect for a 2007 tube using dual-FP's on the base, but for the 2008 trackball you'd want a high-torque CIM with some sort of braking mechanism.

08-12-2008 10:43

Aren_Hill

Re: pic: OH GOD! WHAT HAVE I DONE???

you've made quite a nifty arrangement of manipulation.

As a driver id be a little intimidated to operate that with any dexterity unless i just had a miniature of it on the OI then it would work fairly well.

idk if you'll be able to pull off 1 fp down at the bottom to move that thing it looks like its getting fairly hefty up top. Im probably wrong though FP's are beasts (our shooter this past year is proof).

this thing would be very impressive to see on a bot

08-12-2008 11:10

Andrew Schreiber

Re: pic: OH GOD! WHAT HAVE I DONE???

I second the feeling that it is nifty.

As it stands right now I would write a series of equations that will give you the position in a 2d plane (aligned along the face of the large sprocket) and then work them backwards. These equations would be pretty scary to figure out but once you do them and solve them for x and y you can just use a series of buttons to control it. If you added on a turret you just have to know that that plane will rotate. In all honesty it actually isn't that hard to control. If your driver wanted to be able to control it he could just have a stick to tell it to increase the distance in the y direction or the x direction.

On an unrelated side note, roboticWanderor, your cads are impressive and an inspiration.

08-12-2008 11:27

Aren_Hill

Re: pic: OH GOD! WHAT HAVE I DONE???

I'm just usually a stickler for the controls being very very intuitive
hence why in 2007 i built this
http://www.chiefdelphi.com/media/photos/29147
and i wasn't even the arm operator

I usually wanna know exactly what the robot is going to do when i give it an input, as any delays or mistakes can easily lose you a match

plus im a mechanical guy and a mechanical thinker so simple links between control movement and robot movement are a must for me.

08-12-2008 11:36

Andrew Schreiber

Re: pic: OH GOD! WHAT HAVE I DONE???

Yeah, I am a programmer and as such have a genetic predisposition to distrust mechanical systems.

A physical model would be simpler to do. Perhaps a compromise would work best, a mechanical model which could be used to train some buttons, yet would allow you to fine tune on the fly. Might be an interesting way of controlling a system.

08-12-2008 13:09

spc295

Re: pic: OH GOD! WHAT HAVE I DONE???

how are you driving the second joint? what is the gearbox on the end of the arm for? is it to drive the second joint or to extend the telescope? if not what drives the telescope?

08-12-2008 13:42

Kevin Sevcik

Re: pic: OH GOD! WHAT HAVE I DONE???

Loading depends on the center of mass of your arm, and how heavy an object you're trying to pick up. Gearing depends on the motor you're using, how fast you want it to go, and how often it will be moving.

If all 24 lbs of your arm is centered 40in off that pivot, you're talking about 960 in-lbs of torque. One CIM puts out about 25 in-lbs of torque at 40A. So you'd need at least 1:150 or so gear ratio, probably more, given the efficiencies you'd be getting at that ratio. Just for lifting the arm by itself. Four AndyMark StackerBoxes would get you to 1:160 or so, and you could reduce from there as necessary.

Also, this is for lifting the arm from dead flat, if it won't ever get there or you counter balance it, you could improve things.

08-12-2008 13:44

JesseK

Re: pic: OH GOD! WHAT HAVE I DONE???

What is the bearing/hole plate on the end of the telescope for? It looks like a great place for a sensor, or for the wiring/tubing to come out of, but I could be wrong.

08-12-2008 14:50

JVN

Re: pic: OH GOD! WHAT HAVE I DONE???

When the game is unveiled... ask yourself how many degrees of freedom you actually NEED. Beachbots, FTW.

-John

08-12-2008 15:48

EricH

Re: pic: OH GOD! WHAT HAVE I DONE???

Are you sure about that one, John? (OK, OK, that one has three. One to go up, one to go over, and one to lengthen.)

Since then, one degree of freedom plus any extras on the base.

08-12-2008 15:50

roboticWanderor

Re: pic: OH GOD! WHAT HAVE I DONE???

Thanks a lot Kevin Sevcik, that is relly helpfull. what is funy, is that we just learned this stuff in phsiscs class!
Hopefully, an arm like this could be controlled with a phisical model, similar to the controller I built my sophmore year (it won the innovation in control award by the way).
The gearbox that is on there right now is for the extension, as that math was easy enough to figure out.
the upper arm's articulation technically will operate like a 4-bar linkage, but still be moveable (similar to team 60's arm design)

08-12-2008 15:56

JVN

Re: pic: OH GOD! WHAT HAVE I DONE???

Eric,
As noted by the "FTW" I was referring to their WINNING robot, not it's ancestors.

I've been a huge fan of the super-elegant 2005, 2007, 2008 Beachbot robots. In 2005 & 2007 in particular I loved the 4-bar designs my teams utilized, but then saw that 330 could score as well or better with just a single joint. Simplicity yields elegance.

-John

08-12-2008 15:59

ducttapedude

Re: pic: OH GOD! WHAT HAVE I DONE???

If I am not mistaken that would be the tensioner plate, and if it is, you could also attach a sensor at the point, or you could place it inside the gearbox extension which might be safer

08-12-2008 16:46

Jonathan Norris

Re: pic: OH GOD! WHAT HAVE I DONE???

I would have to say this looks like a fun CAD project to work on, but very unpractical to combine those two systems in real life. By adding a telescoping section to a poof style 2-jointed arm you are basically adding a redundant system to achieve the same goal. The whole point of the lower joint on the 'poof' style arm is to extend the arm to reach farther, higher ect. which can also be achieved by a 'pink' style telescoping arm with a lower joint. So unless you really can't achieve your goal with a 'poof' or 'pink' style arm, I guess this system could work... but that's very unlikely and makes this kind of system unnecessary.

08-12-2008 16:50

EricH

Re: pic: OH GOD! WHAT HAVE I DONE???

Actually, I can only think of 2 330 robots with more than 1 degree of freedom. It's just that 1999-2002 had lifts. 1998 had 2 degrees; 2004 was as shown. (2003 was a 4-bar.)

08-12-2008 19:31

FoleyEngineer

Re: pic: OH GOD! WHAT HAVE I DONE???

Hi Kevin,

Where do you get this figure from? I'm looking at the performance curve for the CIM and it looks like at 40A it's generating about .8Nm of torque which works out to .59 ft-lbs, or about 7 in-lbs - not 25 in-lbs as you suggest.

Maybe I'm mistaken. Wouldn't be the first time! Anybody?

Thanks!

08-12-2008 20:04

AdamHeard

Re: pic: OH GOD! WHAT HAVE I DONE???

The one advantage I can think of is having to reach up, and far over a large object. However, can't remember too many times this would be beneficial.

08-12-2008 20:11

Jonathan Norris

Re: pic: OH GOD! WHAT HAVE I DONE???

Looks like he is taking about stall torque, which is a bit less then 25 in-lbs. Yes we run 40A breakers, but the amperage will spike a lot higher then 40A before the breaker trips. From my rough understanding with 40A breakers on a CIM we can get all the torque out of the motors. The only time I can remember hearing the breakers trip is stalling our drive against a wall...

08-12-2008 20:48

joshy1323

Re: pic: OH GOD! WHAT HAVE I DONE???

congrats im very impressed with your cad work. do u have any other completed designs? and how long did this take to draw this up? im sure u included all the measurements and materials in your design or you wouldnt have been able to calculate the weight and also to do that i am sure u were able to calculate the load it can take in different directions. if so what type of aluminum do u intend to use? is this design just an after thought that u wanted to get opinions about or is this something u want to use? if you are planning to use it idk if u should show the needy eyes all us competitors ur plans like this. again i wanna stress that i am very impressed with ur cad.

08-12-2008 20:52

EricH

Re: pic: OH GOD! WHAT HAVE I DONE???

He does. He's actually one of the three most shown Solidworks designers on these forums. One of your teammates and another Northern California member are the other two. Search CD-Media by the uploader using these three members' names and you'll find plenty.

08-12-2008 21:18

roboticWanderor

Re: pic: OH GOD! WHAT HAVE I DONE???

I DO THIS STUFF FOR FUN.
Really, I do. I ran into a snag trying to figure out the gear ratio it needed for the design, so I decided to post it up here looking for help. I do most of my calculations using the JVN calc to make it easier, then optimize the ratios for part availability, machining complexity etc.

And yes, I have many other designs posted up here, and yes I put in all of my materials as I CAD my parts, this one in particular is made of 6010 (correct?) alum, and steel axles, sprockets, gears etc. what you saw is what SolidWorks did it's mass calculations from.

Also, i realize this design is completely, and utterly complex. I would not really even consider building something like this. But CAD allows us to dream right?

09-12-2008 10:13

techtiger1

Re: pic: OH GOD! WHAT HAVE I DONE???

I agree with John V Neun simplicity is elegance and it works. This is me comming from a team thats made an award winning 8 wd 6 motor 2 speed drive system and a 5 axis arm. I like the fact that its CAD work practice and your asking really vaild questions instead of arguing why or why not this is needed. This is what should be happening on Chief Delphi people. Good work keep it up.

-Drew

09-12-2008 16:47

AdamHeard

Re: pic: OH GOD! WHAT HAVE I DONE???

I think you mean 6061 Aluminum . Most hollow extrusion is most commonly available in 6061 alloy.

09-12-2008 16:54

Re: pic: OH GOD! WHAT HAVE I DONE???

However flattering that may be, I don't deserve any credit for Solidworks. I know how to use it, but I'm much more adept in Inventor right now. If you want to see some really nice CAD in solidworks, check out Madison's stuff; she's quite skilled in that department.

-Craig

09-12-2008 17:45

Kevin Sevcik

Re: pic: OH GOD! WHAT HAVE I DONE???

You're correct, that was a typo on my part, or some such. I intended to use the 100 oz-in at 40A figure you can get from the CIM dimension sheet, which puts it at 6.25 in-lbs. I used that figure in the rest of the math, however, so the ratio still stands.
You can't get anywhere near stall torque out of the CIMs. The circuit breakers, Victor/Jaguar, and motor will all eventually prevent you from doing so. In the past, FIRST has arranged things so it's the circuit breaker that keeps you from using stall torque for any length of time, to protect your investment in your motors and speed controllers. Rest assured, that circuit breaker trips somewhat before your Victor would melt, and that your Victor would melt before your motor did. But the motor would most certainly do so if you stalled it for too long.

The 40A breakers we use will trip in at most 0.6 seconds at the 133A that stall torque would draw, so it's not really available for a useful amount of time, beyond stating up.

09-12-2008 20:55

Triple B

Re: pic: OH GOD! WHAT HAVE I DONE???

pink uses alot of 6063 AL tubing also.
nice cad work wanderer.
mike d

09-12-2008 21:26

joshy1323

Re: pic: OH GOD! WHAT HAVE I DONE???

thank u erich i am relatively new to CD and im very good friends with RC. i see his designs before this site does usually and he is training me on how to use solidworks right not but im already used to his work im more interested in what others have to show. i did not kno that he was so well known on here btw i guess it adds up though since im often making fun of him for always being on here. btw i see ur kind uf well known on CD and im curious as to how to make a name for myself. RC says just start posting but i feel like i have no voice as a new member. any advice?

09-12-2008 21:32

EricH

Re: pic: OH GOD! WHAT HAVE I DONE???

Follow RC's advice. We all start from the same place. If you aren't comfortable, try the Chit-Chat forum until you get a feel for the site. Also, if there's a forum that interests you, that can also be a good place. (For me, it was Rules/Strategy.)

09-12-2008 21:32

Akash Rastogi

Re: pic: OH GOD! WHAT HAVE I DONE???

As a good friend of RC's, welcome to CD
Post if you have a valid question that hasn't been found through the "search" feature up top. Seems like we share a common teacher.

09-12-2008 21:37

Re: pic: OH GOD! WHAT HAVE I DONE???

I would start by reading every single stickied thread. They're usually up there for a reason. Next, clean spelling and grammar helps a lot. After that, don't be afraid to ask questions (assuming you already searched)!.

09-12-2008 21:44

joshy1323

Re: pic: OH GOD! WHAT HAVE I DONE???

why wouldnt u want to try to build this? it does not look too complex at all. it looks more like a few simple parts that are organized to form a complex arm. im new to this site so sorry if im asking too many questions but i am confident that if i had all the materials needed the task of making that arm would be easily done in a week. does your team have all the tools needed to make those parts or is that y u say it is too complex?

09-12-2008 21:53

joshy1323

Re: pic: OH GOD! WHAT HAVE I DONE???

thanks erich u sound just like RC haha. im still getting used to using the site. i have not really explored far out of the list of recent activity and i didnt even know that there was a chit chat part on here. ill check that out though thanks.

09-12-2008 22:00

joshy1323

Re: pic: OH GOD! WHAT HAVE I DONE???

thanks for the advice. sorry if this is a stupid question but what is a stickied thread? is that what this is? and ya RC said that my texting talk has got to go when im on here or i would not be taken seriously. btw do u guys only know him as RC? i keep writing his real name and then i have to go back and write RC instead because i dont know if anyone will know who i am talking about or not. and i apologize for clogging up this topic room can someone tell me how to reply to someone without putting it up here for everyone to read? im not anything close to a computer wiz.

09-12-2008 22:04

joshy1323

Re: pic: OH GOD! WHAT HAVE I DONE???

wow believe it or not he is just a regular student at my highschool. i was not aware that he had such an influence. and thank you i appreciate it. i hope that i am not hurting his reputation with my presence on CD.

09-12-2008 22:06

EricH

Re: pic: OH GOD! WHAT HAVE I DONE???

Here's some advice:
Stickied thread: If you go into a forum here, near the top there will be a thread or several that say "Sticky: [thread name here]". Those are the Sticky thread.
Real names: Look at someone's profile (what you see with their username when they post) to find out if they have/use nicknames or real names. I don't remember RC putting one, but I haven't looked recently.
Replying privately: click a person's username. A list will show up that says something to the effect of "View public profile" "Send Private Message" and some other things. Select the Private Message (PM) and type what you need to.
One other thing: Editing posts. There's an "Edit" button on each of your posts for a short time. Saves you the trouble of posting again to correct a post. Can also be used to delete a post.

09-12-2008 22:36

roboticWanderor

Re: pic: OH GOD! WHAT HAVE I DONE???

Many of the crucial parts of this design rely an a lot of mill work, something my team has very little access to, and the tid-bit that we do is very limited capacity. Piece by piece, yes this arm is relatively simple, but when put together, you need some very important parts (such as a nice big gearbox) to make the rest of it work correctly. As with any design, the more complex it is, the more specific its function, but the higher likelihood that your not going to get it to work. There are teams with access to lots of tools, and build impressive machines, with lots of complex systems that work together perfectly. Then there are the teams with less resources, yet create amazingly functional robots from the resources at hand, sticking with simple "why didn't I think of that??" solutions to problems. Each can create wonderful robots, and be very successful in the games. My team has to try and be the latter, but I dream of the former.

Thanks for all your help guys, I'm currently switching to SolidWorks 2009 SDK so I will return from finals next week in full swing. This should be completed and attached to a robot before kickoff.