pic: Team 148 - Robowranglers 2010 - Armadillo

[JVN]

Someone asked earlier,
When the traction wheels are down, ALL the omni wheels are lifted off the ground. We further lift the center one to allow for traversing the bumps. On the fall prototype, this wheel didn't need to be lifted so it was just spring-loaded downwards.

Curious about how a drivetrain performs with (4X) 2"-wide high traction wheels located on the outer corners in a "narrow body" configuration?
Check out this whitepaper: http://www.chiefdelphi.com/media/papers/1443
You should be able to tell me how it handles...
This was not an accident, but a desired feature of the Nonadrive.

Also note... we have the front and rear pneumatic cylinders on different solenoids. This allows us to independently drop the front/rear traction wheels. We call this "2+2 Mode." When you're in 2+2 mode, the drivetrain turns about a point directly in between the two lowered traction wheels. This allows the driver some cool handling options.

Our primary drive mode is on 5-omnis.
We only use 2+2 Mode and Traction Mode for specialized operations and circumstances.

-John

[JesseK]

Hmm. I wouldn't have thought of it as a desired effect ... interesting.

[AdamHeard]

Originally Posted by JVN

Someone asked earlier,
When the traction wheels are down, ALL the omni wheels are lifted off the ground. We further lift the center one to allow for traversing the bumps. On the fall prototype, this wheel didn't need to be lifted so it was just spring-loaded downwards.

Curious about how a drivetrain performs with (4X) 2"-wide high traction wheels located on the outer corners in a "narrow body" configuration?
Check out this whitepaper: http://www.chiefdelphi.com/media/papers/1443
You should be able to tell me how it handles...
This was not an accident, but a desired feature of the Nonadrive.

Also note... we have the front and rear pneumatic cylinders on different solenoids. This allows us to independently drop the front/rear traction wheels. We call this "2+2 Mode." When you're in 2+2 mode, the drivetrain turns about a point directly in between the two lowered traction wheels. This allows the driver some cool handling options.

Our primary drive mode is on 5-omnis.
We only use 2+2 Mode and Traction Mode for specialized operations and circumstances.

-John

Do you have any programming that gives you a psuedo-omnidirectional drive when in the 5-wheel setup, or is setup as tank with strafing?

[JVN]

Originally Posted by AdamHeard

Do you have any programming that gives you a psuedo-omnidirectional drive when in the 5-wheel setup, or is setup as tank with strafing?

It cannot translate straight while rotating automatically (if that is what you're asking about...)

Seriously... to get an understanding of how it works, think of playing Halo. Any move you can make (X-Y direction only ) the robot can do with default code. It doesn't take a good driver to arc about a fixed point outside the robot.

[roboticWanderor]

Originally Posted by JVN

It cannot translate straight while rotating automatically (if that is what you're asking about...)

Seriously... to get an understanding of how it works, think of playing Halo. Any move you can make (X-Y direction only ) the robot can do with default code. It doesn't take a good driver to arc about a fixed point outside the robot.

he means circle-strafing. keep in mind this is also using the two analog sticks on the x-box controller, this maneuver would be harder using KOP joysticks. i cant wait to see their operator interface this year, they are always so elegant, and portable!

also, a really talented driver could "translate straight while rotating automatically", if you can do it in halo, you can do it with nonadrive. theoretically. this would involve making the drive vector point in the same direction relative to the field, i.e. spinning the movement stick while keeping the rotation constant. easier said than done, but i have seen it in halo.

[Lil' Lavery]

Originally Posted by JVN

We refer to the 5-omni setup as something called a "Slide Drive". When you combine a slide drive with 4 drop down traction wheels you get what we're calling "Nonadrive" (not Nano Drive as Mike Copioli seems to think...)

Why do we use a slide drive?

Here is the quantitative part:
1. This drive allows for the front and rear wheels to be "linked" without needing a ball differential or anything like that. If one wheel comes off the ground, you still have the full power available on the other wheel.

2. We have 4 motors worth of power pointing forward/backward at all times. With a Mecanum drive, you only get part of this. (The mecanum drive has better side-side power than our 1-CIM, but we don't care.

3. The "slide drive" part of the Nonadrive is 100% intuitive to control, with ZERO programming. This is not meant to discount the efforts of our incredible programmers (148 and 217 have some GREAT ones), but the slide drive can be fully utilized with default code, and its control would be identical to Halo, Call of Duty or any other FPS videogame.

Here is the "not so quantitative" part:

This will be a controversial statement...
In all of my competition robotics experience I have never encountered any drivetrain (swerve, mecanum, or omni) that drives as well as our slide drives. Maybe it has something to do with a lack of programming. Maybe it has something to do with a driver's mental block. I don't know. What I do know is that you put a slide drive in the hands of a good FRC driver, and they'll be almost immediately doing maneuvers that make your head spin.

Before you knee-jerk and reply, remember who you're talking to. We understand design tradeoffs. We understand your value propositions may be different than ours.

Honestly, I expected more people to ask us "Why the heck did you do THAT instead of just doing a swerve or mecanum drive?" My answer is... "If you built one and drove it, you'd understand."

I think you may have misunderstood what I was asking, though the more I read your response the more it seems like you might have gotten it.

Many, including you, have seen my personal feelings about [pure] mecanum drives (you even commented on my facebook rant). I wasn't suggesting comparing the nonadrive to a simple mecanum.

But rather I was comparing the "slide drive" portion of it to a mecanum drive. You could replace the four omni-wheels with mecanums and still be able to accomplish any strafing with equal results.
You are also correct about a mecanum drive losing power when wheels lose contact with the ground (barring, as you mentioned, differentials of some sort). This isn't a major issue with chain/gear-linked "sides" of drive trains.
Granted, I was operating under the (apparently incorrect) assumption that you would be operating in the traction wheels drive configuration for most forward/reverse driving (though even a "2+2" also applies to my assumption). The "slide drive" does, in fact, move in forward/reverse more efficiently than a mecanum drive.
Operating under that assumption, I was basically considering the two drives in terms of strafing and rotational ability, in both of which the mecanum drive is advantageous compared to the slide drive.

Knowing the characteristics of the traction wheel set-up, it really comes up to how you want to drive the machine in order to justify any engineering trade-offs. Given the way you stated you wanted to drive it, I absolutely understand the reasoning behind your design choices.

Also note, I never was attempting to call into question your design choices, but rather just seeking more information about why you made the ones you did. And there were indeed some factors I didn't take into consideration, and learned more about your design philosophy and your strategy for playing the game.

Originally Posted by JVN

Nope. The slide wheel is positioned near enough to the CG that she moves sideways almost straight as an arrow. The same can be said for forward and reverse, even without the traction wheels down. No complicated control needed. For testing (before we had any of the other electronics wired up) I took a VEX PIC Microcontroller from inventory, hooked the Victors up and we drove it with default code. Really.

I was more wondering about diagonal motion. With different total torques in either cardinal direction, an input of a "45 degree motion" isn't going to immediately produce a 45 degree motion from the robot because the acceleration in each cardinal direction will be different. Granted, this could be accomplished by using different gearing on the wheels, but then the total speeds would have to be reduced (on the faster geared wheels only, obviously) in order to produce a 45 degree motion.
This really isn't a big concern at all, I was just curious if you felt it was an issue. It's easily adaptable by a skilled driver (though we all know that kid down there can't drive his way out of a paper bag, so maybe he might need programming help ).

As a side note, how is she going to be controlled? Given the amount of options available, I'd assume you're using some sort of game controller in order to have enough buttons readily available to the driver.

[Jamie Kalb]

Originally Posted by JVN

Also note... we have the front and rear pneumatic cylinders on different solenoids. This allows us to independently drop the front/rear traction wheels. We call this "2+2 Mode." When you're in 2+2 mode, the drivetrain turns about a point directly in between the two lowered traction wheels. This allows the driver some cool handling options.

Ah. I was going to ask about that. Makes a whole lot of sense! This isn't the only robot you'll see in 2+2 mode...

But in 2+2 mode, doesn't the CG placement affect the pivot point? I thought you pivot about a point that's a sort of an "average" of 1.) the point between the traction wheels and 2.) the CG. Is that not right?

[R1ffSurf3r]

Is the top roller the only one that is powered, or does the bottom one spin also?

[Akash Rastogi]

I find myself watching this video over and over just because I don't know the name of the song. Anyone know the name?

[Travis Hoffman]

Originally Posted by Akash Rastogi

I find myself watching this video over and over just because I don't know the name of the song. Anyone know the name?

I endured the torture of straining to discern English utterances in between all the screaming and ultimately happened upon...

Refused - New Noise

http://www.youtube.com/watch?v=K8MkVIe9xGc

I vote for Dean Simmons to cover this at IRI. Bring back the mosh pit from '04!

[Racer26]

I just love the "death spin". Did I hear JVN or Paul allude to the magnet being able to hold a ball while deathspinning? I'm DYING to see that.

[Salbert]

In 2008, your Tumbleweed robot had me befuddled on how it could possibly win ANY matches at all, and produced a laughing response from our team captain. And it won at the Championship.

This robot has me asking myself how it the world could it NOT win.

Your robot is amazing. I love your drive train. Good luck, not that you'll need it.

[JaneYoung]

Originally Posted by Salbert

In 2008, your Tumbleweed robot had me befuddled on how it could possibly win ANY matches at all, and produced a laughing response from our team captain. And it won at the Championship.

It won because of the amazing ability of 148 to work with their alliance partners in ways that were a combination of dance, art, and tough competitive brilliance, even when Tumbleweed struggled at times. I thought it was visionary. If you ever get a chance to talk to members of 148 about Tumbleweed, do it.

I hope to hear a lot about Armadillo in that same (but different) amazing way. She's got the moves.

Jane

[Salbert]

Originally Posted by JaneYoung

It won because of the amazing ability of 148 to work with their alliance partners in ways that were a combination of dance, art, and tough competitive brilliance, even when Tumbleweed struggled at times. I thought it was visionary. If you ever get a chance to talk to members of 148 about Tumbleweed, do it.

I hope to hear a lot about Armadillo in that same (but different) amazing way. She's got the moves.

Jane

When I say I was befuddled, it was before I actually saw them in any matches. Once I saw a few matches, I thought they were interesting, but I still didn't think they'd win.

This year, MARS is emphasizing the value of teamwork, like they did with Tumbleweed, with a ramp robot.

We indeed learned the importance of alliance support from them in 2008.

[drtysteve384]

Holy #$@%!!! that is insane...nice work like the kicker design...I wish our team thought of that...and i like lifter, that thing is beaslty, what regionals are yall going to by chance?