Crab Steering on Regolith

[megaman_22201]

i believe that crab drive would be allowed because rule R06 reffers to the "normal" orriantation as the wheels being flat on the ground. this only means that the wheels cant be angled to the floor, it has no constraints on how the wheels can be in oriantiation to the robot.

in short, rule R06 states that the wheels have to be perpendiculer with the floor, therefore crab drive would be possible.

[Laaba 80]

Just a little advice for everyone....

Saying "I Think" doesnt mean anything. Right now the only form to find what is allowed and not allowed is the manual. Once the Q&A and the update system is started you should get things cleared up. If you get to competition and the inspectors say something is not allowed and you say you thought it was ok they arent going to care. If you think of ANY possible controversy over a strategy you want to use, look it up in the manual and be positive it is in compliance with all the rules.

Also, rules from past years games, or other sports dont apply. Dont assume things are the same as last year.

Joey

[BRAVESaj25bd8]

<R06>
...The ROVER WHEELS must be used in a “normal” orientation (i.e. with the tread of the wheel in contact with the ground, with the axis of rotation parallel to the ground and penetrating the wheel hub)...

The floor is a plane. The axis is a line. A plane is parallel to a line if they will never touch if their length was extended to infinity. This means the axis which the wheel is driven about must always be in a horizontal orientation. The purpose of this is to disallow tilting of the wheel. Therefore, R06 does not identify crab steering as an illegal system.

On another note, I also thought that crab steering would work, but for a different reason. In a car, drivers are told to turn with a skid when driving in slippery conditions. This way, the tire can grab and begin rotating with the direction of travel. I do not think that any type of steering will prevent sliding but I think rotating the wheels in the direction of the slide will allow the robot to regain traction faster. But this paragraph was just my thoughts, nothing which is absolute fact. As was mentioned earlier, no statement starting with "I think" should be considered as true without further investigation.

[yoshibrock]

Originally Posted by Laaba 80

Just a little advice for everyone....

Saying "I Think" doesnt mean anything. Right now the only form to find what is allowed and not allowed is the manual. Once the Q&A and the update system is started you should get things cleared up. If you get to competition and the inspectors say something is not allowed and you say you thought it was ok they arent going to care. If you think of ANY possible controversy over a strategy you want to use, look it up in the manual and be positive it is in compliance with all the rules.

Also, rules from past years games, or other sports dont apply. Dont assume things are the same as last year.

Joey

That's all fine and dandy except for the fact that different people interpret rules differently. Finding out other peoples' interpretations can help people to make more informed design decisions before the Q&A starts. Reading the rule book can only get you so far.

And on a note pertaining to the actual thread....

I think (haha) that a crab drive has its advantages and disadvantages in any situation. In this years game, however, I think that the difficulty in controlling is already going to be such that it discourages a crab or swerve drive. Granted, we haven't leaned towards crab drive in the past, but this year while brainstorming we didn't even consider it. I'm sure some team out there will pull it off, but it'll take a pretty skilled drive team. I do encourage you to try however; that team might be yours.

[Laaba 80]

Originally Posted by yoshibrock

That's all fine and dandy except for the fact that different people interpret rules differently. Finding out other peoples' interpretations can help people to make more informed design decisions before the Q&A starts. Reading the rule book can only get you so far.

Thats exactly my point. Interpruitations dont matter. The only thing that matters is what is stated in the rule book. I am bringing this up because I was a ref at our state lego tournament. We had a problem with the INTERPRUITATION of a rule that was allowed at various regionals. We looked in the manual, and there was a clear rule stating what was previously allowed is not allowed. I'm just saying dont guess on this type of stuff. Take the initiative to look rules up your selves, and if a rule is not clear, submit a Q&A, or keep up with the updates. If you get questioned on a rule at a competition and you say "well I heard on CD......." thats not going to cut it.

Originally Posted by yoshibrock

And on a note pertaining to the actual thread....

I think (haha) that a crab drive has its advantages and disadvantages in any situation. In this years game, however, I think that the difficulty in controlling is already going to be such that it discourages a crab or swerve drive. Granted, we haven't leaned towards crab drive in the past, but this year while brainstorming we didn't even consider it. I'm sure some team out there will pull it off, but it'll take a pretty skilled drive team. I do encourage you to try however; that team might be yours.

I was only talking about saying I think when questioning the legality of something. Offering opinions about strategies is fine.

Joey

[yoshibrock]

But before the Q&A starts during the first two critical days of strategy and design, a team needs to have guidance on wishy-washy rules. Knowing others' interpretations of those rules helps them get a general idea of the general consensus of the rule. I'm not saying they should stick with this interpretation of the rule throughout build season (they should certainly confirm it with updates and such), but an unofficial interpretation of a rule that prevents a standpoint in design is better than an official rule that causes many conditions to be built into designs and strategies.

In any case, this isn't the thread for this discussion. I apologize for taking up space.

[Dan2081]

You are forgiven

[Redo91]

My team was actually looking to use a crab/swerve drive for the first time this year. Upon seeing that we would be pulling a trailer, I began wondering how that would affect changing direction. Going forward was obvious, you are just pulling. But if you go left or right to avoid a robot or get where ou want to be, would the trailer cause the robot to do kind of an awkward rotation while it moved? And the trailer would jack-knife when trying to go backwards, would that cause the robot to want to follow it somewhat?

[JagWire]

I'm also very interested in some sort of crab drive for several reasons.

First of all, using a style of steering such as a tank drive, requires skidding to turn, automatically meaning you lose something like 20% of your traction. By utilizing a crab-drive style steering it could allow you to turn without skidding more easily.

It would also allow for a lot of flexibility, since just because you have the capability of turning each wheel, it doesn't mean you have to. I can see where multiple drive setups could be tested by modifying the way the controls operate. Three main ideas that have crossed my mind so far are a conventional car steering, a simulated tank-drive, and also a monster-truck type steering. All things that could be played around with.

I think that flexibility could be a very useful this year, as it may aid drivers to a great extent in being able to attain good control.

[Racer26]

I don't know, so here's my $0.02.

In years past, and I can already see it this year, people read too much into, and "lawyer" the rules. The rules are all there for a reason, and for the most part, the intent of each rule should be more or less obvious. The Q&A typically responds in line with the INTENT of the rule, and thusly, thats the basis we should be going on.

To me, the INTENT of <R06> is to prevent teams from utilizing the spokes of the wheel as a traction surface. It is NOT (IMO) intended to stop teams from creatively USING these wheels, in, for instance, a big omniwheel made with these as the rollers, or other creative uses. My interpretation is that the "normal" way to use a wheel is with the tread in contact with the floor. However, I'm by no means on the GDC, and thats for the Q&A to make the final call.

The fact that an omniwheel with these as the rollers would be enormous is somewhat irrelevant to the point.

[Mike Schreiber]

Originally Posted by 1075guy

To me, the INTENT of <R06> is to prevent teams from utilizing the spokes of the wheel as a traction surface. It is NOT (IMO) intended to stop teams from creatively USING these wheels, in, for instance, a big omniwheel made with these as the rollers, or other creative uses.

A big omniwheel would be redundant as they are already basically omniwheels. A mecanum (spelling?) wheel however...

Also I'm not sure a giant omni wheel made of these would work because then technically your wheels don't always have their axles parallel to the ground, but they do when they are in contact with the ground...Still questionable.

[Lesman]

Actually, these wheels are anti-onmi wheels. The idea behind omnis is that they have a negligible transverse coefficient of friction (CoF) (due to the rollers) and a much higher inline CoF (usually due to the rubber material of the rollers). These wheels are the exact opposite, with an inline CoF on less than half of the transverse CoF. In fact, I doubt a standard configuration of omni wheels would move at all, with the exception of turning in place.

[omgapirate]

I am not sure if this has been said but I believe that somewhere in the rules it states that the coefficient of friction doubles if the wheels are turned sideways

[gpetilli]

I totally agree. they just want you to use the "flat" part of the wheel.

Originally Posted by megaman_22201

i believe that crab drive would be allowed because rule R06 reffers to the "normal" orriantation as the wheels being flat on the ground. this only means that the wheels cant be angled to the floor, it has no constraints on how the wheels can be in oriantiation to the robot.

in short, rule R06 states that the wheels have to be perpendiculer with the floor, therefore crab drive would be possible.