Can we stand one more thread on entanglement?

[Joe Johnson]

I posted the following message to FIRST.

What do folks think?

Joe J.

Regarding Tethers: 114 Seemed Clear, 321 muddied the waters...

From Msg #114:
...When designing your robot, please consider the
environment on the playing field during a match and use your common
wisdom to evaluate the likelihood of your mechanism getting wrapped
around an axle, caught on a bolt or arm or other robot feature, or
even hung up on part of a goal....

...The ultimate determination of
what presents a risk of entanglement is subjective and will be made by inspectors at each competition event, and by the referees in each
match (in the event that something passes inspection but later becomes a problem during a match).

From Msg #321:

...if you have a tether that you try to make non-entangling (small,
flat, whatever), will the judges automatically disallow it if it is
flat on the playing field? ...

...Yes. See posts 114, 115 and 158 on tethers...

************************************************** *******************

#114 seemed pretty clear. As long as the "tether" was not something that common sense indicated that at a robot could easily get entangled in, it was okay.

#321 makes things less easy to understand. First of all, I cannot find message #158. Second of all message #115 only refers to rule DQ3 & M16 -- little help there. Message #114 I seemed to understand but then the ruling of an "automatic disallow" for tethers on the ground seems to be in conflict with message #114, which stressed common sense and actual entanglement issues like getting caught inside another robot's mechanism.

So... ...I am sure that without further clarification nearly everyone is going to be unhappy when they get to a competition. Either you will disallow a feature on a robot that teams counted on being legal OR you will allow a feature that many other teams will say to themselves, "If only I knew that THAT would be allowed, I would have built that feature too!"

I am begging you, please clarify this issue once and for all.

Suppose a robot divides and has only a thing I will call a "leash" connecting the pieces (I use the word leash because tether is already has a lot of baggage with associated with it, not the least of which is that many questions have been asked about tethering a projectile which has nothing to do with the current situation).

So, by means of this leash, the robots meet the "robots must be designed to stay in one piece rule" but...

... the sixty four thousand dollar question everyone wants to know is: What is(are) the standard(s) by which this leash will be ruled legal or illegal?

If I am asked for a vote, I would say that the text of message #114 defined a very clear standard. But, given that standard, the answer given in message #321 would have to be changed to read something like "See message #114. The judges and inspectors will apply that standard when deciding if your leash is legal"

Please respond quickly as I know of several teams that are basing there entire machine concept on the answer to this question. Strangely enough, some are certain that leashes are illegal while others are equally certain that they are not.

Joe J.

[patrickrd]

Joe,

Thanks for making that post. Our team is another team that has looked at the rules, made design desicions, and then read updates that are inconsistant with previous rules and updates (although with respect to a different rule). Now we are left looking back and forth between the rulebook, our design, and the FIRST updates and posts, and scratching our heads... Let's hope they start clearing things up.

Patrick

[Nate Smith]

One thing to keep in mind during all of this is that the rules do not state "if something causes entanglement, it will be disallowed." Rather, they refer to a RISK of entanglement, meaning "if something MAY cause entanglement, it will be disallowed." While I have seen some confusion in various Q&A regarding the tether/leash/entanglement issue, I think the easiest way to handle this for all the teams is to look at a definition of entanglement and then decide:
Entanglement: To twist together or entwine into a confusing mass; snarl.

So, my "common sense" test for this would be as follows:
-Take the part of your machine that you are concerned about
-Try wrapping it around a 1/2" piece of rod using reasonable force(anything which could break a piece of glass is NOT reasonable force)
-If you are successful, then this part could get entangled in another machine as easily as you wrapped it around that rod, so don't use that design.

[Mike Gray]

The contradictory answers posted in FIRSTtech2002 are causing no small amount of consternation.

They need an objective test for determining whether a leash or proxy device presents a risk of entaglement.

How can a long, flat, folding arm be dis-allowed, if other robots can pass over it? On the other side of the coin, if you have a robot
that can expand to block the entire playing field and push everything into the other side - how can that be illegal.


While flexible tether may be out - I can't see how big arms can be.
Smart, no - legal yes.

[Jason Rudolph]

FIRST clarified it on the yahoo board....
> > And if you have a tether that you try to make non-entangling
(small,
> > flat, whatever), will the judges automatically disallow it if it
is
> > flat on the playing field?

We wrote:
> A: Yes, See posts 114, 115 and 158 on tethers.

We apologize, but this answer was incorrect. Devices will not be
automatically disallowed. They will be evaluated as described in
message 114.

[Joe Johnson]

FIRST seems to be very clear now. Not only because of taking back their answer to #321, but because of #335 shown below.

Joe J.

> I would really like clear answers to the following questions:
>
> Setup:
>
> Suppose there is a robot that can split down the middle.
>
> Suppose that at the start of the match, the robot splits with only a
> 30 ft bundle of wires connecting them.
>
> Assume that it is a bundle of four 10 gauge wires and four 16 gauge
> wires. Also assume that they are strain relieved and bundled
> appropriately.
>
> Question A:
> Is it legal for such a robot to drive around the entire match in
this
> fashion?

No, because the wires would present a risk of entanglement.

> Question B:
> Would the answer change if the tether was longer or shorter?

If the tether was short enough that it did not present a risk of
becoming entangled in a robot or a goal, then it would be allowed.

> Question C:
> Would the answer change if the robots did not split until the last
> few seconds of a match?

No. Timing is not considered.

> Question D:
> Would the answer change if the bundle of wires was made of more
> bigger wires, more wires, smaller wires or fewer wires?

The bundle will be evaluated by the robot inspectors at each event,
and by the referees on the field during each match. If at any point
it is deemed to present a risk of entanglement, then it will be
disallowed.

> Question E1:
> If there is some situation that such a case would be legal, would
> such a robot be found in violation of rule that prohibits going
under
> the goal (GM20) if the goal was pushed up over the tether by another
> robot?

This would not be a violation of GM20, because the robot did not
intentionally put the tether under the goal. However, the alliance
pushing the goal over the robot could be penalized if damage to
the goal was deemed likely to occur as a result of passing the goal
over a robot.

> Question E2:
> If there is some situation that such a case would be legal, would
> such a robot be found in violation of rule that prohibits going
under
> the goal (GM20) if one half of robot went around a goal one way and
> the other half went around the robot the other way and the bundle
> went under the lower plywood base?

Intentionally passing a part of the robot under the goal would be
considered a violation of Rule GM20.

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