View Full Version : pic: Off season teaser 1
Peyton Yeung
18-11-2011, 13:47
[cdm-description=photo]37120[/cdm-description]
If I had to guess, I'd say it's a for a drive train that's similar to what 1629 did in 2008. They had 2 wheel pods that could steer left right. When both turned opposite of each other, the effect was a very tight turn radius (front rotates left, rear rotates right, causing the robot to make a sharp left turn).
There may be other considerations that I'm not thinking of, but 3x1.5 C-channel (0.2" wall for the legs, 1/8-3/16" wall for the base) is rigid enough for what you're doing there and also fits the 2.5" super shifter into the channel very nicely. It would also provide extra aluminum to support the rest of an FRC frame.
Justin Montois
18-11-2011, 15:00
Swerve segway?
/Mind Blown
Aren Siekmeier
18-11-2011, 15:07
Ackermann steering, or at least simplified car steering. Are you planning to put a differential of some sort in the middle?
Cool idea. It would definitely change things since turning at high speeds is more straight forward, but turning on a dime would probably be harder (or at least different from what people are used to...)
Peyton Yeung
18-11-2011, 15:35
Swerve segway?
Sadly no but that would be legit.
The wheels will be able to rotate more than the traditional ackerman steering.
We do hope to make tight turns like 1629 did in 2008...maybe even tighter :yikes:
Ninja_Bait
18-11-2011, 15:39
Swerve segway?
That's total win right there. Well played, Mr. Blay.
However, I believe this is meant to be the first ever use of Necco Wafers (http://www.necco.com/ourbrands/default.asp) as a lightweight sprocket replacement.
Peyton Yeung
18-11-2011, 15:49
However, I believe this is meant to be the first ever use of Necco Wafers (http://www.necco.com/ourbrands/default.asp) as a lightweight sprocket replacement.
Yeah...we color every part a different color to help in figuring out what part is what.
Ninja_Bait
18-11-2011, 16:18
Hey, does that actually turn far enough for the robot to translate sideways? I just realized that it looks like it could - it would be an ackerman-crab.
Peyton Yeung
18-11-2011, 16:51
Hey, does that actually turn far enough for the robot to translate sideways? I just realized that it looks like it could - it would be an ackerman-crab.
Aww...I was hoping more people would guess before someone got it right. Yes it is an ackerman-crab prototype.
Andrew Lawrence
18-11-2011, 19:00
Swerve segway?
2012 game? :)
Drivers: "This'll be interesting!"
Builders: "Simple design, I love it!"
Programmers: "f*ck."
Peyton Yeung
18-11-2011, 19:54
Drivers: "This'll be interesting!"
Builders: "Simple design, I love it!"
Programmers: "f*ck."
This is actually similar to what happened when I purposed the idea. I (driver) told our lead mechanical mentor (builder) who was like sweet and when I told our software lead (programmer) he was like get it done soon so we can have the code done by next game.
That was like 4 months ago :)
thefro526
18-11-2011, 19:57
Does this use true Ackerman geometry or do the wheels turn in a parallelogram configuration?
There's a big difference between the two at high speeds.
Aren Siekmeier
18-11-2011, 20:30
One thing I just noticed. It looks like on each side there are 3 miter gears, with two on the same shaft but on opposite sides of the wheel side gear. It seems like this wouldn't work and just lock up and/or shred the gears.
And I guess I'm a bit confused. It sounds like this is basically just a swerve implementation with wheels powered in pairs and perhaps steered in pairs as well. How exactly are you adding Ackermann functionality in a way that isn't already there mechanically?
Ninja_Bait
18-11-2011, 22:54
Aww...I was hoping more people would guess before someone got it right. Yes it is an ackerman-crab prototype.
Heh, score. Now I will solve the game hints... *holds envelope to turban...*
But I agree with compwiztobe. This seems like an interesting way to handle both crab and ackermann, but it doesn't seem like it adds much to either.
Peyton Yeung
19-11-2011, 07:47
In all this project was initially started as a swerve project but to reduce weight and cost of a traditional swerve/crab drive it took some designs from a car (ackerman steering). It isn't a true swerve/crab drive nor is it a true ackerman steering drive but somewhat of a hybrid for the sake of using less funds and weight.
MichaelBick
19-11-2011, 12:27
There are a couple of problems with this design:
1) Compwiztobe is right; the miter gears will lock
2) If you try to turn this assembly, the wheels will try turn in opposite directions (think of a 2 wheel drive turning) and something will have to brake or slip.
3) (i'm assuming you are going to use two of these modules) When all the wheels are collinear, the robot will fall over. If you add casters though, you can fix this problem, but that defeats the point of make two wheel modules in the first place.
4) You won't be able to turn, because unlike regular swerve, you do not have the 4 modules to form a x with the "turn' chain. You could potentially add caster, but again, that defeats the point of making modules with two wheels.
Sorry for being so negative. On the bright side, this is the dedication that makes teams win. Nice job trying to reduce the price, weight, and complication of arguable the best drive train in first.
MichaelBick
19-11-2011, 12:41
Sorry, I didn't realize what the pink sprockets were there for, so you can disregard comments 2 and 3. Just another comment, you will be limited in your strafing, specifically in strafes exactly left and right, or near those angles. This is countered though, by your easily achieved Ackerman steering, that needs very little programming. After my little revelation, I have realized that this is actually a rather viable drive train, once comment 1 has been fixed, to allow teams with very little resources and time, to achieve a drive train that acts like 6 wheels swerve, without the ability to strafe perpendicular the the robot, and to turn on the spot, like swerve and 6 wheel. With improvements, this could become something a lot like octocanum, giveing close to the best of both worlds.
With the miter gears, I wouldn't be surprised in the least if the bottom one was free-spinning. It's set up so that that's all you'd need to do to keep the gears from locking up. Then you just have one gear acting as a spacer.
Peyton Yeung
19-11-2011, 22:29
There are a couple of problems with this design:
1) Compwiztobe is right; the miter gears will lock
2) If you try to turn this assembly, the wheels will try turn in opposite directions (think of a 2 wheel drive turning) and something will have to brake or slip.
3) (i'm assuming you are going to use two of these modules) When all the wheels are collinear, the robot will fall over. If you add casters though, you can fix this problem, but that defeats the point of make two wheel modules in the first place.
4) You won't be able to turn, because unlike regular swerve, you do not have the 4 modules to form a x with the "turn' chain. You could potentially add caster, but again, that defeats the point of making modules with two wheels.
Sorry for being so negative. On the bright side, this is the dedication that makes teams win. Nice job trying to reduce the price, weight, and complication of arguable the best drive train in first.
1. Like EricH said, the bottom one is a spacer.
2. The wheels turn together so they always face the same direction.
3. There is no possible way for all 4 wheels to be on the same line.
4. Isn't it possible to turn a four wheel drive bot by giving a positive value to 1 set of wheels and a negative value to the other set of wheels?
The fronts are linked together and the backs are linked together.
Awwwww I was looking for the new ball drive.
But it looks really good! I would also like to see how it interfaces with the frame and such.
MichaelBick
20-11-2011, 10:46
1. Like EricH said, the bottom one is a spacer.
2. The wheels turn together so they always face the same direction.
3. There is no possible way for all 4 wheels to be on the same line.
4. Isn't it possible to turn a four wheel drive bot by giving a positive value to 1 set of wheels and a negative value to the other set of wheels?
The fronts are linked together and the backs are linked together.
Like I said, disregard 2 and 3. For number 4, if you look at the CAD, the supershifter will be connected to both wheels. This means that you cannot power each side individually, so you cannot turn like a 6 wheel.
Like I said, disregard 2 and 3. For number 4, if you look at the CAD, the supershifter will be connected to both wheels. This means that you cannot power each side individually, so you cannot turn like a 6 wheel.
If you have 2 of these, each side is powered independently. If they're front and back, as stated, then it's a wide-oriented 4WD. Turns quite well, actually--maybe better than a 6WD.
There just haven't exactly been all that many wide-oriented robots the last few years--2009 had quite a few, though.
CNettles11
04-12-2011, 08:49
I hate to revive old threads but, this is a steering solution that will work, and this is how.
http://i.imgur.com/4GzOa.png
Ninja_Bait
04-12-2011, 08:55
On that last diagram, the bottom arrow is reversed, right? Or does this have mecanum wheels capable of that kind of translation? :)
CNettles11
04-12-2011, 08:57
That was definitely me slipping up, I should fix that.
MichaelBick
04-12-2011, 20:56
but you still cannot turn on a dime
Andrew Lawrence
04-12-2011, 21:52
but you still cannot turn on a dime
If you have your code set up so as that you can align all wheels straightly, you can turn with a skid-steer system. I wonder if that's even more possible with a 6 wheel drop center swerve...
MichaelBick
04-12-2011, 21:55
Not with this setup, as left and right wheels are driven together.
Not with this setup, as left and right wheels are driven together.
Per an earlier post:
If you have 2 of these, each side is powered independently. If they're front and back, as stated, then it's a wide-oriented 4WD. Turns quite well, actually--maybe better than a six wheel drive
If the pair of wheels in each of these assemblies is aligned (i.e. They're perpendicular to how the original picture shows them) it will allow the robot to function as a four wheel tank drive, which can turn just fine.
Dillon Carey
05-12-2011, 01:57
I wonder if that's even more possible with a 6 wheel drop center swerve...
Look at our (team 1625) robot from 2010.
It is described somewhat in this paper http://www.chiefdelphi.com/media/papers/2579
How well the robot will turn is also based on the placement of c.g., as described in this paper:
http://www.chiefdelphi.com/media/papers/1443
If anything, the zero-radius turn will be somewhat off-center because there is no symmetric place the center of gravity can exist while also maintaining stability for the other turning configurations AND being far enough offset from the center of area to reduce the torque/current needed. Off-centered-ness isn't a big deal, but it may muck with autonomous mode if zero-radius turns are heavily depended upon.
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