View Full Version : pic: Omni Robot
bear24rw
18-05-2008, 20:31
[cdm-description=photo]31528[/cdm-description]
Andrew Bates
18-05-2008, 20:32
This is a really cool design nice work. It looks like the frame is made of Lexan or is that just a product of the rendering?
Also whats the green thing in the middle?
It is a cool design. It would be pretty darn expensive though. Victors are 150 dollars atleast and the omni's are not cheap. It would be pretty nifty to see this thing in action
-Vivek
looks like the green thing in the middle might be a battery cell pack.
bear24rw
18-05-2008, 21:49
It is made out of 3/16 lexan, the green thing is a 10 D-cell 12v 10AH battery pack.. ill give more details later i gotta go finish my term paper lol
robomaxx
18-05-2008, 21:55
It is a cool design. It would be pretty darn expensive though. Victors are 150 dollars atleast and the omni's are not cheap. It would be pretty nifty to see this thing in action
-Vivek
If this robot does not have to be FIRST legal, then why not use HB-25's instead of victors. They work just as well, but are only 50 dollars.
Akash Rastogi
18-05-2008, 22:01
HB-25 (http://www.lynxmotion.com/Product.aspx?productID=493&CategoryID=) Link provided for aforementioned speed controller. (We have enough Vic's)
Nice design. It looks like it'd be fun to drive. I think we have plenty of Victors in the shop.
lukevanoort
18-05-2008, 22:02
Depending on the motors used, using HB-25 speed controllers could be an expensive mistake, since HB-25s have about 37% less continuous current capacity than Victor 884s.
Kyle Love
18-05-2008, 22:10
Lexan can also allow for a good amount of "flex" in the frame, which can be good with this style of drive, along with mecanum also.
Mike Nawrot
18-05-2008, 22:39
Yes, victors are expensive, but when can get them for free because you have so many around the shop, they're the best way to go. That's why he has the blue 60 mm fans on there. The ones he found don't have fans. I'll leave the rest of the explaining up to Max. Haha.
Tim Baird
18-05-2008, 23:02
Lexan can also allow for a good amount of "flex" in the frame, which can be good with this style of drive, along with mecanum also.
Yeah, make sure to use a healthy supply of cross-bracing in between each layer to minimize that flex. A Lexan chassis is very feasible, you just have to make a good, sturdy design and then follow through in manufacturing. Goodluck!
bear24rw
18-05-2008, 23:02
Yes, victors are expensive, but when can get them for free because you have so many around the shop, they're the best way to go. That's why he has the blue 60 mm fans on there. The ones he found don't have fans. I'll leave the rest of the explaining up to Max. Haha.
also the fact that they wont fit in between the bottom two plates if they have the stock fans on there.. but yeah we already have the victors so thats no problem, the biggest problem is where to get the lexan water jetted lol
Nikhil Bajaj
19-05-2008, 00:11
Depending on the motors used, using HB-25 speed controllers could be an expensive mistake, since HB-25s have about 37% less continuous current capacity than Victor 884s.
This mostly depends on the gear ratio they're using. With omnis, you have less traction due to friction in general due to the rubber used typically being more slick than traction wheels, so it'll be easier to spin out rather than stall on carpet. If the robot is geared for 25 feet per second you could run into problems with this (that number is an example, I don't know the exact threshold off-hand but you could use JVN's drivetrain calculator and the coefficients of friction off of AndyMark's site to estimate it. Or do what I do and forget every time so I draw the same free body diagram each time and solve the same equation.)
Since it is an omni-directional drive system, it should be relatively easy to get out of a situation where you are stalling motors.
That said, lukevanoort has a good point, when using the HB-25s using some 30A breakers is a very good idea to protect your investment. Remember the breakers for the Victors, too, I'd say.
By the way, how fast is this thing supposed to go?
shock190
19-05-2008, 16:00
If you cant get waterjetting done easily, something like this could be done relatively well with a bandsaw and jigsaw and a wonder file. It would just take longer and not quite as smooth, but it would work.
Laaba 80
19-05-2008, 17:41
Yeah, make sure to use a healthy supply of cross-bracing in between each layer to minimize that flex. A Lexan chassis is very feasible, you just have to make a good, sturdy design and then follow through in manufacturing. Goodluck!
Our team builds our entire robot out of polycarbonate. It builds a good chassis, and it looks cool.
Also, make sure you have a way to stop the wheels from spinning. I was the driver this year and we had an omni bot like your design. Trust me, it is really hard to drive, especially if you have no way of stopping the wheels.
Joey
you have one too many wheels.......;)
but it definitely looks cool.
Team 857 Kiwi Bot (www.chiefdelphi.com/media/photos/16411)
That said, lukevanoort has a good point, when using the HB-25s using some 30A breakers is a very good idea to protect your investment. Remember the breakers for the Victors, too, I'd say.
Breakers are always good, but based on the picture the overall stall/current load should be pretty light. The weight of the proposed robot should be low.
Trust me, it is really hard to drive, especially if you have no way of stopping the wheels. I'd put the braking jumper switch on the Victors to the on position.
Alex.Norton
21-05-2008, 14:54
If your actually looking at this type of drive train for the season I would definitely suggest building this to do some software developments because while it may seem uncontrollable when you first build it they can be made very stable.
I was the driver this year and we had an omni bot like your design. Trust me, it is really hard to drive, especially if you have no way of stopping the wheels.
Joey
Don't take the first spin on it and dismiss it right away. They are hard to get to be easy to drive but the process is rewarding and you will get a fast, fun bot to drive. It takes more than the breaking jumper on the victor.
I use code written by Arthur Dutra that was posted here as the basis for an omni control system. It works well out of the box. Can you post your code, since it sounds like you've put lots of work into it?
Alex.Norton
23-05-2008, 18:43
If your interested in looking at our code, PM me with your email and i'll send it to you. Keep in mind that we used the 2007 gyro to stabilize the robot and our machine had a tractor style suspension to keep all four wheels in contact with the ground at all times.
In terms of the suspension I can't entirely say if it absolutely necessary but we included one in all three omni bots that we built. We also used a gyro in all three bots and I can guarantee that it will be uncontrollable if you don't use one of the two, and very possibly both. All of our machine were very easy to drive once the correct constants for the control loop had been found.
I'd put the braking jumper switch on the Victors to the on position.
You took the words right out of my mouth.... :rolleyes:
EEliteDefender
25-05-2008, 16:18
team 1714 used a omni drive and it worked its was a fun system to drive good luck
yeah it looks really cool!! make sure you don't get thrown off the first few times driving it! it is hard to drive at first, but it is the most fun drivetrain I have ever driven!!! I love the lexan frame too! Whats the thickness of the lexan?? (I may of missed it if it were said somewhere.. sorry)
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