Omnidirectional strategeries

[hixofthehood]

Our team opted not to go with a crab robot, but we noted the maneuverability advantage of a robot with such steering capabilites.

Has anyone decided to go with a crab-walking design (I know some teams have)? And if your team has, why did you choose that design over another option?

(There has been a lot of talk about crab-walking in the technical discussions, but I wanted to look at it strategically)

[Duke 13370]

A good idea with the crab steering would be for king of the hill bots, they could strafe back and forth to block a robot from coming over (well, they could always just have wings, but if you didn't)

[GregT]

Crab? OMNI DRIVE!

I beleive patrick posted something about how to pull it off, its really not that hard and allows you to go any direction instantly.

Greg

[Bduggan04]

Originally posted by Duke 13370
A good idea with the crab steering would be for king of the hill bots, they could strafe back and forth to block a robot from coming over (well, they could always just have wings, but if you didn't)

The only problem is that most crab drives have high centers of gravity. A robot pushing up on an angle from below might be able to lift you up slightly and push you, or they'd tip you over altogether.

[Duke 13370]

The only problem is that most crab drives have high centers of gravity. A robot pushing up on an angle from below might be able to lift you up slightly and push you, or they'd tip you over altogether.

I didn't even think about that, but depending on how you design the rest of the robot, it could have a very low center of gravity. placing all the rest of the weight low (battery, frame, etc) could lower it drastically, or a complete redesign of the drive may solve the problem.

[Adam Y.]

Well if your using omnidirectional wheels your robot won't have much pushing power due to their design but with crab steering you should have an cool advantage because youll be able to move back and forth.

[Yan Wang]

Why in the world would having an omnidirectional wheel affect torque? Yes, you'd be more easily pushed from the side if you had a pair of omni wheels, but your forwards movement is uninhibited... our strategy last year was to grab to goals and hold them their very well. We used omniwheels and could rarely be pushed in high gear. If we dropped down our second set of wheels (not omni), we could lift the goal which added more weight to the robot and more strength, thereby stopping us from getting moved. I think the only team that did so was 188 in Canada though we got them back in the finals

[GregT]

An ideal omni-drive will cost you around 33% of your torque, but our robots are friction - not torque - limited.

Greg

[Adam Y.]

Why in the world would having an omnidirectional wheel affect torque?

I didn't say that did I. Omnidirectional wheels do allow you to get pushed from the side very easily due to the fact that you have put castors onto the side of it and not to mention omniwheels usually are made up of metal. This usually affects traction.

[Madison]

Originally posted by monsieurcoffee
If we dropped down our second set of wheels (not omni), we could lift the goal which added more weight to the robot and more strength, thereby stopping us from getting moved. I think the only team that did so was 188 in Canada though we got them back in the finals

Well, we pushed you, 340, and two goals across the field in NYC

But, no matter that, I really liked your method for changing wheels. It's something we looked into this year, but ultimately decided against.

[Yan Wang]

Our robot's programming wasn't quite working in NYC... lol. Stuff like the second set of wheels didn't come down till about 3/4 of the way through the regional... stuff finally came together in Canada and also in the nationals.

[ahecht]

190s wheels aren't onmidirectional or crab steering, but we still won't need to turn in most matches.

[GregT]

Originally posted by wysiswyg
I didn't say that did I. Omnidirectional wheels do allow you to get pushed from the side very easily due to the fact that you have put castors onto the side of it and not to mention omniwheels usually are made up of metal. This usually affects traction.

I dont think you understand omni-drive


I'm talking about a robot with a 360 degree freedom of movement, instantly - no turning. From standing still it can go any direction it feels like.

And Ian:
I don't rememebr this, and this is something I would remember
Sure, you pushed us accross the field, but we didn't have 2 goals at the time.

Also, our method of switching gears was not weight efficent at all- the only reason we chose it was because it would let us lift up on the goal at the same time.

Greg

[Joe Ross]

Originally posted by GregT

Sure, you pushed us accross the field, but we didn't have 2 goals at the time.

Yes you did. 639 had grabbed both goals, and 340 was latched onto one of them also. [/nitpick]

[Alex Forest]

warning of omniwheels: we had them last year and when we used last years bot on the ramp, we had to go up it backwards (omnis in back) because it would slide around...jsut a helpful tidbit