Tank Drive vs. Omni Directional Drive

[jamie_1930]

It seems like a lot of teams are using mecanum, and some even omni, wheels this year so my question is with all these teams using these wheels, how many of those teams are using just normal tank drive and how many are using an omni directional drive to control their robot?

Please only vote on the poll if your using mecanum or omni wheels for your drive train. Also there have been some discussions between or mentors on the true implementations of whether or not using on omni directional drive to control a 4wd mecanum robot will truly be effective or will it mostly a waste of time. So I'm looking for some opinions on what you guys think. do the benefits of a omni directional drive outway the hassle of making one that works well?

Currently our programmers have a basic omni directional drive set up, and three methods of re calibrating the gyro during competition.

[ratdude747]

tank with omni's in the back. the thought was to increase traction and be able to turn around the ball.

[jamie_1930]

Originally Posted by ratdude747

tank with omni's in the back. the thought was to increase traction and be able to turn around the ball.

We thought of this for a second, but in 2008 we used a caster bot with single supports in the front and back for the drive configuration and with this drive system it was common to overturn because of the ease of turning, and when examining this, 4w omni, configuration we began to fear spinning out of control.

[Edoc'sil]

looks like a straight up west coast for us, it looks like the game could get a bit rough this year, so we decided traction was king, not maneuverability.

[MrForbes]

I don't understand the question....I don't understand how/why you'd use mecanum wheels with tank drive control?

[jamie_1930]

Originally Posted by squirrel

I don't understand the question....I don't understand how/why you'd use mecanum wheels with tank drive control?

It would be the same controls as a normal 4wd tank drive where you spin the right side forward and left backward to turn in left in place, and vice versa. The thought is that by switching out normal wheels with mecanum, coupled with the tank drive control method, you can increase your maneuverability.

[Alan Anderson]

Jamie is right. You get amazing turning performance by using mecanum wheels on an otherwise plain vanilla four-wheel tank drive robot. You sacrifice almost 30 percent of your theoretical maximum power in the process, though playing with the friction on the roller axles can get a lot of it back while still retaining the ability to turn in place without hopping or overloading the motors.

[MrForbes]

Interesting, thanks for pointing that out!

[FRC4ME]

Originally Posted by ratdude747

tank with omni's in the back. the thought was to increase traction and be able to turn around the ball.

This is what we're doing. It will be difficult to drive but easy to aim, IMO.

[SteveJanesch]

We're using the kit chassis (tank drive) with sticky wheels in the front and whatever works best in the back - slick, omni, or mecanum (we have a set of each). We're going to test each type and let the driving decide. We had to cut the opening of the kit wheel bracket (leg) wider to accommodate the extra width of the dual omni. We'll have to make our own wheel brackets to use the mecanum wheels.

We've tested the slick and the omni wheels so far, and the omnis do an interesting thing - if they're in the back when going slowly over the bump, the chassis will self-align. Since they give much better forward traction than they resist the sideways movement, the trailing omni wheel in the back just pushes that side of the chassis right up to the bump. It's the coolest thing I've seen so far during build season (within our team).

I expect that the mecanum wheels will give similar or better pivoting than the omni wheels, less forward traction but a bit more resistance to being pushed sideways. It'll probably be about a week until we get them tested, though.

- Steve