pic: Jester Drive:Mecanum Wheel Drive Train

[ahecht]

Because of the orientation of the rollers, a mecanum wheelbase is never in a position where it can be pushed without skidding. In the worst case scenerio, where the robot is pushed on a diagonal, there are still two wheels with rollers whose axes are aligned parallel to the pushing force. I can't speak for the Jesters, but if their rollers are anything like ours, they have pretty good traction and pushing resistance.

On 190, we have our controls set up with a one stick to translate the robot and a second stick to control rotation. I know that they were having trouble getting everything working at BAE, but the system worked pretty well in the shop.

[Jeffmudhs]

We use one controller. If I remember correctly, mind you i'm not on the drive team and have not driven the robot, i believe we use the trigger + direction for translational drive, and the button to spin. As stated above, We are not easily pushed because of the orientation of the wheels. they form to make a shape such as:

\ /
/ \

It is noticable on the drawing above. The wheels allow for slip so we can be pushed with enough force and so that it does not damage parts for the drive train (easily, all things break).

I hope this answers your question.

[Nitroxextreme]

those wheels look so awesome
all they all custom made by your team

has anyone been able to find a place to buy them
i know that my team wanted to use them what was unable to find them for purchase

and without a decent shop we have almost no choice but to not use them

[Jeffmudhs]

As stated previously, yes they were all created by the team. Hand mixed, and hand poured. That includes the molds we have used to pour them into.

[CyberWolf_22]

My team and I have had a design using these wheels for the past two years now but have not found a way to produce them. It is great to see that a couple teams have done it successfully. Good Luck at your regionals. I will be sure to stop by your pit at championship.

[Greg Needel]

team 211 has a very similar drive aswell

[SizzelChest330]

Do you guys know how much actual Pushing power you have? I know with Mecanum wheels you need alot of traction or else you wont get very far in a pushing match...
And do you know your speed with them?
I'm guessing with 4 wheel CIM Motor drive your getting about 6-8 Fps or am I wrong?

[Alex357]

Just to clear a few things up...
This is a mecanum wheel hybrid completely manufactured by our team. The rollers are configured on 45 degree angles on our custom hubs. In order for the wheels to achieve their designed motion, each roller's bearings are actually molded into their urethane rubber material. The angles make an "X" pattern.

\\\ ///

/// \\\

Forward motion is achieved by driving all four wheels forward, the same concept applies for backward. Though there is a specific way to do it with these wheels, spinning can also be done in the traditional tank steering manner.

The translational movements are achieved on a screw principle. Diagonal wheels move in the same direction while the other diagonals move in the opposite. For example, the front right and back left move forward, while the others move backward. The roller configuration causes the robot to "slide" left and right.

These wheels can also achieve omni-directional movement: for example, spinning about its own axis while driving in an arc.

The mecanum wheel's rollers prevent the robot from being pushed freely like traditional onmi-wheels.

[The Lucas]

Originally Posted by Alex357

The mecanum wheel's rollers prevent the robot from being pushed freely like traditional onmi-wheels.

No one get at Pitt was able to push on you for an extended period of time anyway. You just strafed and sidestepped them.

How is the 3 degrees of freedom (spinning while translating) development coming? I would love to see that at Philly.

[Evan Austin]

Hey, I see it now!
Great job, this is an idea I would never have thought of. I like this design a lot. In this game, maneuverability is important and you should definitely have that under control. What is it like to drive? I have never driven an omni directional robot and I am curious. It looks excellent
Good Luck!

[Alex357]

Originally Posted by The Lucas

No one get at Pitt was able to push on you for an extended period of time anyway. You just strafed and sidestepped them.

How is the 3 degrees of freedom (spinning while translating) development coming? I would love to see that at Philly.

We have an early code for the three degrees of motion. However, being able to use it is a completely different question. It's not so much a code issue as it is a driver issue. We would have to use a "flight stick" and training a driver to control a truly omni-directional robot would take time. We are definately planning on doing demos with it, but i'm pretty sure it won't show up in this year's competition. Maybe you'll see it at a post-season event.

[Ellery]

Way to go guys - That's an awesome setup.... We've done most of every drive system so far and this maybe one we'll try next just because it's so cool.

Ellery

[Tom Bottiglieri]

Originally Posted by Alex357

We have an early code for the three degrees of motion. However, being able to use it is a completely different question. It's not so much a code issue as it is a driver issue. We would have to use a "flight stick" and training a driver to control a truly omni-directional robot would take time. We are definately planning on doing demos with it, but i'm pretty sure it won't show up in this year's competition. Maybe you'll see it at a post-season event.

The method I have thought about using is having on regular 2 axis joystick for controlling the translation (robot moves in direction of joystick and at a speed relative to the magnitude of the distance from the stick from its "home position"). Then, you can the x axis on another joystick to control turning. So now you are able to control the robot in 3 ways. You can use the one stick to translate and then turn, you can drive in a "wheel and throttle" method, using the Y axis on the translate stick to control speed and the turn stick to control turns, like normal tank drive.

Or...

You can incorporate a gyro into your control algorithm, and keep the translate stick absolute to the field. This means if you push the stick forward you will move away from your drivers station at 0 degrees, no matter which way the robot is facing. This could help in controlling the "3rd dimension of motion"

Wow.. I need to play around with one of these drive bases.

[Robomaniac928]

hello guys i was wondering were you guys got those wheels because next year if i can get my team to go along with it i would like to try something similiar ty

[EricH]

Originally Posted by Robomaniac928

hello guys i was wondering were you guys got those wheels because next year if i can get my team to go along with it i would like to try something similiar ty

BEFORE you commit to doing the mechanum drive, be sure you know what will happen and have a backup plan. We almost did it, but we decided that our design, which is closer to 190's than 357's, did not meet our requirements, so we are currently getting ready (very slowly) to try the next stage of design. The problems observed both on ours and 357's: a) lack of pushing power, and b) slow sideways motion. Both problems may be fixed in later editions and/or by other teams. So, test now, and if you decide to do it, good luck!