pic: 2826 Halonomic Drive Prototype

[Jared Russell]

Originally Posted by EricH

Clockwise, O contact pattern on the ground, lines are vectors in a clockwise turn, arrows are vertical component of the vector:

\../ (^v)
/..\ (^v)

Clockwise, X contact pattern on the ground, lines are vectors in a clockwise turn, arrows are vertical component of the vector:

/..\ (^v)
\../ (^v)

Eric,

The problem is not with the vertical components of the vectors but rather with the horizontal. Also, I think that what I call "X" and what you call "X" are different.

So, using your notation:

Orientation of torque vectors - Vertical components - Horizontal Components

What I called "O":
/..\ (^v)(>>)
\../ (^v)(<<)

No problem here. The vertical components want the robot to turn CW, and so do the horizontal.

What I called "X":
\../ (^v) (<<)
/..\ (^v) (>>)

Problem! The vertical components want to turn CW, while the horizontal components want to turn CCW. The two cancel each other out as long as the roller friction is negligible.

[AJ R]

That looks sweet! The wheels look nice, did you make them your self? From our experience with an omni drive, the building was the easy part, and the programming is the hard part. Ours was drivable, but difficult to control. Hope yours turns out better than ours.

[Tyler Olds]

Thank you for all the nice compliments, I will try to answer what I can, but this is a prototype and we have not gotten to test it on anything but a concrete floor. We are still making adjustments to the drive since we determined that we need to have an additional gear reduction so the motors do not kick out.

Originally Posted by Greg Needel

I like the concept alot, I sketched something similar for a project I had an idea for. Can you tell me how this works on grass? Also can you control the height of the main body by adjusting your struts on the fly or is it just a fixed suspension driven by a shock?

We have not tested it off road yet, but the hopes of the suspension that we have is to take it in different terrains. It is a fixed suspension, however we have holes drilled to adjust each leg.

Originally Posted by Chris is me

WOW that thing looks beastly! Are those 14 inch wheels? Got any video? That seems like it wond be really cool to see run and swerve. How much movement do the shocks have? Could they go, say, upside down? There's some small paralells to be drawn here; 1714 did holonomic in 2008 build, 2826 did crab in 2009, now those are reversed in the offseason... I guess I just find it funny.

It is a beast both in size and weight. I do not know the exact diameter of the wheels off hand. The shocks have a fully range of movement to the point that the frame will bottom out before the shocks give. The robot is not designed to drive upside down if it flipped over but it would be cool.

Originally Posted by big1boom

Nice mechanum drive. Looks awesome, with some pretty cool machining.
Are those custom made wheels?

They are custom made out of polyurethane that we made in a custom mold.

Originally Posted by Andy Baker

This is very, very cool. As with everyone else, I have a few questions:
What is the purpose of the scissor-like suspension? Is it to provide active suspension for the wheels, or does your wheelbase footprint need to change during your application?
What is the diameter of those wheels?
This is a very inspirational mechanism. I would love to see what all is going on within each of those suspension members.
Sincerely,
Andy Baker

Thanks Andy! The footprint does not need to change during usage, just to provide an active suspension. I should be able to post a couple pictures or video next week.

[Tyler Olds]

Got a short video uploaded on youtube. I took this at midnight on the spur of the moment so this is nothing professional. Look for a longer video in a couple weeks. There are still many more tweeks that will be done, hopefully sooner than later.

*Oh and the 2x4 was just randomly laying there*

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

[EricH]

Originally Posted by Jared341

Eric,

The problem is not with the vertical components of the vectors but rather with the horizontal. Also, I think that what I call "X" and what you call "X" are different.

So, using your notation:

Orientation of torque vectors - Vertical components - Horizontal Components

What I called "O":
/..\ (^v)(>>)
\../ (^v)(<<)

No problem here. The vertical components want the robot to turn CW, and so do the horizontal.

What I called "X":
\../ (^v) (<<)
/..\ (^v) (>>)

Problem! The vertical components want to turn CW, while the horizontal components want to turn CCW. The two cancel each other out as long as the roller friction is negligible.

I see now.

I also think that X and O should be "standardized" at a certain view for future reference. I'll let wiser heads than mine figure out whether you do it from the top or bottom, though.

[David Brinza]

Can this robot flip over and still drive? That would be awesome!!