Chief Delphi - 2015: Year of the Mecanum

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- - 2015: Year of the Mecanum (http://www.chiefdelphi.com/forums/showthread.php?t=131913)

AutodeskGeek

03-01-2015 14:30

Re: 2015: Year of the Mecanum

Quote:

Originally Posted by Ether (Post 1419696)

My guess is this won't be a major issue with a properly built and driven mecanum.

Amen to this. The only trouble we had with mecanum was the bridges in 2012. It wasn't impossible, we still balanced. Since it's only a 16 degree angle, it shouldn't be impossible to get over it.
Breakaway year, they had larger bumps. We went up them fine with mecanum also. Given, they were carpeted.

Some teams will struggle with the mecanum, some won't.

Bruceb

03-01-2015 14:32

Re: 2015: Year of the Mecanum

never used macanums before but really considering it this year. what is the prefered gearbox for these?

JosephC

03-01-2015 14:34

Re: 2015: Year of the Mecanum

Quote:

Originally Posted by Bruceb (Post 1419858)

never used macanums before but really considering it this year. what is the prefered gearbox for these?

If you have not prototyped mechanum or done it before, I would not recommend bringing it out this season. It doesn't seem difficult at first, but you will end up spending far too much time on your drive train instead of allocating proper time to your mechanisms.

Ben Wolsieffer

03-01-2015 14:41

Re: 2015: Year of the Mecanum

Our team has had a good amount of experience with mecanums, and we haven't any big problems with bumps. We used them in 2010 (w/o suspension) and were able to climb over the bump, and also in 2012, where we were able to easily climb the bridge.

Based on that experience I think driving over the scoring area won't be a problem at all.

Bruceb

03-01-2015 14:45

Re: 2015: Year of the Mecanum

the code is for the most part available if I am right so i believe if I give my programmers a macanum chassis early they will make it work. I dont see any serious mechanical issues as long as I get the best ideas from this forum.
Your thoughts on that?
again what is the prefered transmission?
Thanks

Brandon Zalinsky

03-01-2015 14:49

Re: 2015: Year of the Mecanum

The biggest hitch in developing a mecanum drivetrain is code. It requires lots of code testing. The hardware is much easier. The wheels are placed in standard configuration and require very minor differences in hardware required from a 4wd skid. The biggest hitch in the hardware is that you need four separate transmissions.

1058 has used 9:1 transmissions for a few years on our mecanum drives.

Peyton Yeung

03-01-2015 14:55

Re: 2015: Year of the Mecanum

461 used toughbox minis last year with a 12.75:1 ratio on 6" wheels. The biggest issue we had was due to a lack of suspension, one of the wheels did not contact the floor like the others.

AutodeskGeek

03-01-2015 15:08

Re: 2015: Year of the Mecanum

Quote:

Originally Posted by Brandon Zalinsky (Post 1419875)

The biggest hitch in developing a mecanum drivetrain is code. It requires lots of code testing.

For those teams that have used mecanum in the past, this is a non-issue. There's also plenty of help with algorithms online that teams trying it for the first time can use. Probably not too much testing unless you are implementing original drive styles with your mecanum wheels.

Ben Wolsieffer

03-01-2015 15:11

Re: 2015: Year of the Mecanum

Quote:

Originally Posted by AutodeskGeek (Post 1419887)

Yeah, the programming is not that difficult. WPILib for C++ and Java has a function for field oriented (or robot oriented) mecanum drive that works well. I don't know about Labview.

The Doctor

03-01-2015 15:22

Re: 2015: Year of the Mecanum

Quote:

Originally Posted by TheJoe (Post 1419636)

Could it be possible that mecanum drivetrains are the ideal way to go because of their maneuverability?

MY THOUGHTS EXACTLY!!

The Doctor

03-01-2015 15:23

Re: 2015: Year of the Mecanum

Quote:

Originally Posted by lopsided98 (Post 1419888)

WPILib for C++ and Java has a function for field oriented (or robot oriented) mecanum drive that works well. I don't know about Labview.

You do realize that the libraries will probably be very different since the introduction of the RoboRio.

Ether

03-01-2015 15:33

Re: 2015: Year of the Mecanum

Quote:

Originally Posted by The Doctor (Post 1419903)

You do realize that the libraries will probably be very different since the introduction of the RoboRio.

Not that different. 2015 WPILib Java:

Code:

    /**

     * Drive method for Mecanum wheeled robots.

     *

     * A method for driving with Mecanum wheeled robots. There are 4 wheels

     * on the robot, arranged so that the front and back wheels are toed in 45 degrees.

     * When looking at the wheels from the top, the roller axles should form an X across the robot.

     *

     * This is designed to be directly driven by joystick axes.

     *

     * @param x The speed that the robot should drive in the X direction. [-1.0..1.0]

     * @param y The speed that the robot should drive in the Y direction.

     * This input is inverted to match the forward == -1.0 that joysticks produce. [-1.0..1.0]

     * @param rotation The rate of rotation for the robot that is completely independent of

     * the translation. [-1.0..1.0]

     * @param gyroAngle The current angle reading from the gyro.  Use this to implement field-oriented controls.

     */

    public void mecanumDrive_Cartesian(double x, double y, double rotation, double gyroAngle) {

ratdude747

03-01-2015 15:55

Re: 2015: Year of the Mecanum

Quote:

Originally Posted by Kevin Sevcik (Post 1419725)

For the record, we tried mecanums in 2008 and 2009, and just the plywood under the carpet would make things go wonky if you were trying to do a precise alignment.

I'm not saying they'll be undriveable, I'm just saying they're going to make auto and certain precision tasks a wee bit more challenging and error prone than they need to be.

Unless you're talking offseason prototypes, I highly doubt that *cough *

Jalerre

03-01-2015 16:37

Re: 2015: Year of the Mecanum

For those talking about driving over the bumps, I do believe that is prohibited. Don't quote me on this but I think it says so somewhere in the manual. Their primary only purpose is as a scoring platform so you don't need to worry about how mecanums are going to get over the bumps.

In regards to programming mecanums, I can say from experience that it is really easy. Our team has used them for the past 3 years. Both Java and C++ (I can't speak for Labview) have methods for programming a mecanum drive (2 methods in fact, at least in the 2014 library). Just plug in your parameters and that's all there is to it.

Finally, though I didn't agree with my team in the past about a mecanum drive train, this year I can really see the advantages. Because there won't be too much robot-to-robot interaction you won't have to worry about pushing power or traction. Also strafing will be really useful when you need to line up to stack the totes and recycling bins.

nicholsjj

03-01-2015 16:56

Re: 2015: Year of the Mecanum

The code in labview is a canned VI. The only problem that I have had to help teams with is many younger teams make the rotation the throttle axis. Most of the time I have them switch to a button switch statement for turning and it works out fine, some still like other axis turning methods and it can be worked through with the Get axis. Our team has decided to use Mecanum since the no defense is in play and we might try to go for the stack in auto. Mecanum will work out nicely for strafing left or right and picking up as long as you use a gyro for drift. The only initial issues we are concerned with is the frame spacing for the totes and going over the scoring platforms. We think 8" HD's will be fine enough to prototype though.

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