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Chris is me 10-06-2010 20:00

Re: Crazy Drive Train Ideas
 
Quote:

Originally Posted by CENTURION (Post 966201)
For now my favorite solution is off-road swerve/crab drive, using two wheels on each pod (ok, I'll admit, the two-wheels part is mostly to make it look cooler, but it would have it's benefits: traction, weight distribution on soft material, etc)
Each pod would be individually rotated via an FP or Window motor, and would raise and lower via a pneumatic piston and some guide bars. (the pistons could be pressurized somewhat to create a passive suspension system).

You may be interested in this whitepaper. 1114 made a swerve drive somewhat similar to this in 2004.

jamie_1930 10-06-2010 22:12

Re: Crazy Drive Train Ideas
 
Quote:

Originally Posted by 548swimmer (Post 966205)

That is actually infuriating that is exactly how I wanted to go about it, minus the webcam although it is a nice addition.

NickE 10-06-2010 22:26

Re: Crazy Drive Train Ideas
 
Quote:

Originally Posted by Hawiian Cadder (Post 966081)
i just came up with another one, make a robot that is entirely encased in a hollow sphere with omni wheels on every corner facing outward, to drive the main part of the robot drives the inside of the sphere, if we ever get a water competition this would be highly helpful i think.

Have fun putting bumpers on that robot. ;)

daltore 11-06-2010 02:16

Re: Crazy Drive Train Ideas
 
Quote:

Originally Posted by 548swimmer (Post 966205)

First let me say that I dearly love XKCD and Randal Munroe. But he got it wrong. Just take a good look at those "omni wheels". They're mecanum...

I've been looking into making a drive train I recently read about in Servo magazine: Melty Brain. Basically, it's an effectively holonomic robot (overall it is, but instantaneous moments it isn't) that can be driven with only one wheel and one motor, but you can technically use as many wheels and motors as you want if you've got a fast enough processor. This site has a good explanation:

http://www.spambutcher.com/meltyb.html

I want to preface this description with the note that this drive train is absolutely terrifying, but if it's crowds you want, then crowds you'll have. The robot spins up really fast in a circle (no gear reduction on the wheels, in fact depending on wheel diameter, the CIM's might be a little slow) using the motor[s], and very precise timing allows you to vary the motor speed at specific points in the circle to effect a net vector that allows the robot to move around. If you think of it in terms of a polar graph, to go forward, you'e have a base speed, at 0, the motor would be going faster than that base speed, at PI/2 and 3PI/2, the motor would be spinning at the base speed, and at PI, the motor would be slower than base speed.

This is a fairly easy drive train to build (although it's harder with the size of robot you're building, you have to make sure the center of mass is relatively stable and all of your frame connections are very solid, otherwise the robot might try to rip itself apart). The hard part of this type of drive train is the code. You have to have either one accelerometer and know its radius away from the center of mass (the axis of rotation), or two accelerometers inline and know the distance apart (I like that one because it means you can change batteries without necessarily recalibrating). You measure the centripetal acceleration with the accelerometers, and with the radius information, you can figure out angular velocity. You effectively integrate that (multiply the calculated angular velocity in one loop by the amount of time between loops, then do it again next time and keep a running sum), and you'll end up with your angle. The angle is used to calculate wheel speed. The motor control is very simple, and can in fact be done with a PWM-capable pin and a large Darlington transistor or power transistor and a gate driver (the Darlington transistor is usually used because you can pick one up at Fry's for under $5).

I'd suggest making a small one (at least at first, probably a good size to keep it though) out of a small piece of 1/4" Lexan or plywood and a Fisher-Price motor and a Lite-Flite or equivalent high-traction wheel, and seeing how it goes before you think about moving up to anything bigger and more dangerous. It's been done before, but all for antweight (and one beetleweight) combat robots, so it would be cool to see what you guys come up with to do with it. An idea I had was to use a line of LED's and write messages in the air while it's spinning, but there are probably lots of other things you could do with it.

Chris is me 11-06-2010 07:32

Re: Crazy Drive Train Ideas
 
Quote:

Originally Posted by jamie_1930 (Post 966224)
That is actually infuriating that is exactly how I wanted to go about it, minus the webcam although it is a nice addition.

Why is it infuriating?

Anyway, if you want a crazy drivetrain idea... Figure out a 4wd drivetrain that is not vulnerable to pushing that goes over the bumps that can turn. I wish I figured that one out...

JamesCH95 11-06-2010 08:53

Re: Crazy Drive Train Ideas
 
Quote:

Originally Posted by Chris is me (Post 966248)
Figure out a 4wd drivetrain that is not vulnerable to pushing that goes over the bumps that can turn. I wish I figured that one out...

One that uses ackerman steering with zero mechanical trail :)

Chris is me 11-06-2010 08:54

Re: Crazy Drive Train Ideas
 
Quote:

Originally Posted by JamesCH95 (Post 966253)
One that uses ackerman steering with zero mechanical trail :)

It also has to zero point turn, sorry. :P

I saw one solution this year. Very forehead-slap moment for me. (Edit: I think with some adaptations, that same drivetrain could outperform a Nonadrive. Wait... I think I just inspired myself. CAD time!)

JamesCH95 11-06-2010 08:58

Re: Crazy Drive Train Ideas
 
Pictures of the solution? Or Nonadrive for us un-initiated?

Chris is me 11-06-2010 09:18

Re: Crazy Drive Train Ideas
 
Quote:

Originally Posted by JamesCH95 (Post 966255)
Pictures of the solution? Or Nonadrive for us un-initiated?

*spoiler alert for teams that want to guess :)*

The pictures available don't show it, but 195 had a drivetrain with 4 high traction wheels. To turn, they had drop down omni wheels in line with the back wheel axles. It was an extremely clever solution that I feel stupid for not thinking of when I wanted a 4wd this year.

As for the adaptation, let me work on that one for a bit.

Andrew Remmers 11-06-2010 09:38

Re: Crazy Drive Train Ideas
 
I would like to make an adaptable drive train that is easily suited for most kinds of game play or game types

JesseK 11-06-2010 11:00

Re: Crazy Drive Train Ideas
 
What do you mean by "outperform" the nonadrive? Considering that the nonadrive effectively addresses a multitude of issues with both omni and 4wd while combining their strengths (and even manipulating a perceived weakness of 4wd), saying a drive train will outperform the nonadrive is a very broad, boastful statment...

Additionally, until you've driven a drive train with "modes" (linkage in 2008/09, nonadrive as implemented in '10), you really don't get a feel for the true power of a manipulatable center of rotation.

Chris is me 11-06-2010 20:32

Re: Crazy Drive Train Ideas
 
Quote:

Originally Posted by JesseK (Post 966268)
What do you mean by "outperform" the nonadrive? Considering that the nonadrive effectively addresses a multitude of issues with both omni and 4wd while combining their strengths (and even manipulating a perceived weakness of 4wd), saying a drive train will outperform the nonadrive is a very broad, boastful statment...

Additionally, until you've driven a drive train with "modes" (linkage in 2008/09, nonadrive as implemented in '10), you really don't get a feel for the true power of a manipulatable center of rotation.

The random idea I thought of when I made the post had the capability of doing particular features better than a Nonadrive base. It was rashly typed, yes, but also an example of the kind of thinking that could get you to think up your next "creative" drivetrain. Start looking at drives that arent 6-drop and what advantages they have, and how to work around their drawbacks. Evolution is innovation.

CENTURION 14-06-2010 00:17

Re: Crazy Drive Train Ideas
 
ok, here's a few sketches if you care to take a look:

This is 8-wheel swerve drive, with modules that can be raised and lowered (you can ignore pretty much all of the math and notes on there, that was me doing figuring on amounts of material for the whole bot)

(I will hopefully have Sketchup models done soon)

http://s226.photobucket.com/albums/d...rent=001-3.jpg

This is a triangular(ish) robot, with a single swerve module in the middle, and basically a kiwi drive around it (three omni's, each powered by a FP/Window Motor). The only reason the omni's are powered is to keep the robot from spinning wildly when you try to rotate the swerve module.

http://s226.photobucket.com/albums/d...rent=002-1.jpg

548swimmer 23-06-2010 01:12

Re: Crazy Drive Train Ideas
 
Quote:

Originally Posted by Chris is me (Post 966257)
*spoiler alert for teams that want to guess :)*

The pictures available don't show it, but 195 had a drivetrain with 4 high traction wheels. To turn, they had drop down omni wheels in line with the back wheel axles. It was an extremely clever solution that I feel stupid for not thinking of when I wanted a 4wd this year.

As for the adaptation, let me work on that one for a bit.

We used that method as well, and it made so much sense once someone said it that everyone else was amazed they didn't figure it out themselves. Though, if you want to be picky, it is technically a 6 wheel drivetrain.

Bjenks548 23-06-2010 14:24

Re: Crazy Drive Train Ideas
 
So I have another drive train running through my head. I was wondering what gear ratio would be used to power an individual wheel using a ban bot moter and what it would be for a fisher price moter. Also I thought i remebered that we only get 2 bb and 2 fp moters, is that right?


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