You guys steering your wheels??

[freaky_dork88]

What kind of steering are y'all using on 4wd??

[DonRotolo]

Skid steer. We may move to active steering in the future, depending on how well (or poorly) skid steer works, but for now we are hesitant to add something we've never done before to the design, considering we only have 4 weeks to go...

[dtengineering]

Skid steering, but in the wide set up. We actually have 6wd, but have raised the front wheels 1/8" and set our centre of gravity as far back as possible. That gives us, essentially, a 4wd skid steer set up but with a width of about 34 inches between the wheels and a length of just 13. (The middle axles are just slightly forward of the centre line.)

As the width gets greater and the length less, the robot begins to approximate a 2 wheel drive robot (like a segway) and should be very close to having the absolute maximum possible turning force.

That's how we see the theory, at least. We'll let you know how it works in practice once we get it all together and give it a try, perhaps late next week or early the following week.

Jason

Crab. Basically 4 wheel steering, with the front wheels linked, as well as the back linked separately. Each wheel is independently powered, and we'll have both traction control as well as multiple steering modes:
-Front wheel steer with rear wheel Yaw control
-All wheel steer
-Standard crab with gyro corrected heading to allow standard crabbing regardless of the trailer.

Should be fun.

[Ian Curtis]

Originally Posted by CraigHickman

-Standard crab with gyro corrected heading to allow standard crabbing regardless of the trailer.

Hmm? So, does the crab drive just do it's think, and you let the trailer do what it will, or does it correct for the effect of the trailer on the robot? If it auto-corrects for standard crabbing, SERIOUS props to your programmer(s), and does the robot base maintain it's orientation?

Originally Posted by iCurtis

Hmm? So, does the crab drive just do it's think, and you let the trailer do what it will, or does it correct for the effect of the trailer on the robot? If it auto-corrects for standard crabbing, SERIOUS props to your programmer(s), and does the robot base maintain it's orientation?

That part is still in theory, so here's hoping we can pull it off. We're pretty sure we've figured out a way to have the robot be able to crab as if the trailer wasn't there, but our speed will be pretty slow while we're doing it.

Hint for teams wanting to do a simple traction control: Put some encoders on each wheel and compare wheel speed to a gyro/accelerometer combo to tell robot heading/speed. Then play with different methods of "adjusting" how it drives, and you should enjoy the results.

[ZakuAce]

Originally Posted by dtengineering

Skid steering, but in the wide set up. We actually have 6wd, but have raised the front wheels 1/8" and set our centre of gravity as far back as possible. That gives us, essentially, a 4wd skid steer set up but with a width of about 34 inches between the wheels and a length of just 13. (The middle axles are just slightly forward of the centre line.)

As the width gets greater and the length less, the robot begins to approximate a 2 wheel drive robot (like a segway) and should be very close to having the absolute maximum possible turning force.

That's how we see the theory, at least. We'll let you know how it works in practice once we get it all together and give it a try, perhaps late next week or early the following week.

Jason

Exactly the same thing we are doing. It was the easiest thing to do, but prototyping this was really annoying and took me forever. But maybe I'm just dysfunctional.

Once we have the CAD/Inventor drawings done and machine the parts, it should be a simple yet effective design.

[germanystudent]

skid steer. we thought of having an independent steering system where both sets acted kind of like trucks on a skateboard but powered by pneumatics. we decided to scratch that because of space...

[gorrilla]

tank, cause we dident have enough time for crab.....