2nd Most Awaited Q and A Answer?

[DMetalKong]

Let me try my hand at this:

1) Two elements are contiguous if the degrees of freedom between them is zero (i.e. when power is not applied, given the orientation and position of one element it is possible to compute the exact orientation and position of the other element).

2) Any elements that are both inside and outside the frame boundary (i.e. reaching across the frame boundary) must be contiguous.

3) Any elements outside the frame boundary must not extend outside of the boundary formed by extending the frame boundary 14" perpendicularly outward and rounding any resulting vertices with radius 14"

4) Any element crossing the frame boundary must form an angle of no more than 90 degrees with any other element that crosses the frame (measured from the centroid of the frame boundary)

The language could be cleaned up (especially in points 3 and 4), but I think this covers all of the situations that have been discussed.

[Tristan Lall]

Originally Posted by DMetalKong

Let me try my hand at this:

The language could be cleaned up (especially in points 3 and 4), but I think this covers all of the situations that have been discussed.

That's a good start. Allow me to pick it apart a little.

• The degrees of freedom language is a good idea, but how do you account for component and assembly flexibility? If I join two things with a bar of aluminum, does that imply 0 DOF? What if the bar is really thin and flexible? (Basically, is there a threshold beyond which you consider something to be a DOF?)
• Maybe you want to describe "crossing" the frame boundary, and mention that "contiguous" refers to the parts on either side of that boundary? (Otherwise, it could be interpreted as meaning contiguous with respect to some other thing.)
• From what parts of the appendages is the relative angle determined?
• Using the centroid is good in principle. However, depending on whether your definition of frame boundary can vary due to robot configuration changes, you might have a uniqueness problem. (Was "frame boundary" meant to be the same as the "frame perimeter"?) Also, unfortunately the centroid is imaginary and hard to locate.
• I assume you understand that the 90° spec you outline is not equivalent to the existing constraint. Also, presumably you mean the smallest angle between them. (And incidentally, isn't 75° a lot like 105°? Why would one be illegal and the other not?)

This is actually the exercise the GDC needs to go through internally (who knows, maybe they do) to settle on verbiage that reflects their intent accurately, and exposes the potential for misinterpretation.

[DMetalKong]

Originally Posted by Tristan Lall

• The degrees of freedom language is a good idea, but how do you account for component and assembly flexibility? If I join two things with a bar of aluminum, does that imply 0 DOF? What if the bar is really thin and flexible? (Basically, is there a threshold beyond which you consider something to be a DOF?)

IMO an unconstrained flexible element fails the 0 DoF test because when power is not applied, given the position of any other element (taken pair-wise) that is part of the appendage it is not immediately apparent what position the element in question will occupy. As to whether or not an element is "flexible" (as all elements will have some degree of deflection to them), I feel that this is something to which the reasonable man test can be applied (i.e. an element is flexible if a reasonable man believes that the element was designed to take advantage of its deformation)

Originally Posted by Tristan Lall

• Using the centroid is good in principle. However, depending on whether your definition of frame boundary can vary due to robot configuration changes, you might have a uniqueness problem. (Was "frame boundary" meant to be the same as the "frame perimeter"?) Also, unfortunately the centroid is imaginary and hard to locate.

I did mean "frame perimeter" when I wrote "frame boundary"; since the frame perimeter must not articulate, I believe this covers your first point. As to the centroid being imaginary, I see no other precise solution that would offer a definite "center" to the robot; if there is a major disagreement between a inspector and a team the centroid can be (albeit with difficulty) be calculated.

Originally Posted by Tristan Lall

• Maybe you want to describe "crossing" the frame boundary, and mention that "contiguous" refers to the parts on either side of that boundary? (Otherwise, it could be interpreted as meaning contiguous with respect to some other thing.)

The idea was that any part that crosses the frame perimeter must be contiguous with any other part that crosses the frame perimeter, in a pair-wise fashion. A part that "crosses" the frame perimeter is one that is both inside and outside the frame perimeter simultaneously.

Originally Posted by Tristan Lall

• From what parts of the appendages is the relative angle determined?
• I assume you understand that the 90° spec you outline is not equivalent to the existing constraint. Also, presumably you mean the smallest angle between them. (And incidentally, isn't 75° a lot like 105°? Why would one be illegal and the other not?)

The 90° was chosen because barring requiring all robots to be rectangular in shape I see no reasonable way to define the "sides" of a robot in a way that allows for various geometric shapes, while retaining what I believe is the intent of the rule: to allow appendages to extend, but in a relatively narrow direction. Perhaps a better test would involve rotating a 90° cone around the centroid.

Given your feedback (much appreciated by the way), here is a revised list:

1) Two elements are contiguous if the degrees of freedom between them is zero (i.e. when power is not applied, given the orientation and position of one element it is possible to compute the exact orientation and position of the other element). Flexible elements will be considered to add to the degrees of freedom if a reasonable man believes that the element was designed in such a way as to take advantage of its deformation.

2) Any elements that are simultaneously both inside and outside the frame perimeter (i.e. reaching across the frame perimeter) must be contiguous in a pair-wise fashion (i.e. any element crossing the frame perimeter must be contiguous with any other element crossing the frame perimeter).

3) Any elements outside the frame perimeter must not extend outside of the boundary formed by extending the frame perimeter 14" perpendicularly outward and rounding any resulting vertices with radius 14".

4) Any elements outside of the frame perimeter must lie within the right isoceles triangular prism constructed with infinite height and infinite leg length and placed so that the vertical edge of the right angle must be coincident with a vertical axis placed through the centroid of the robot.

[Tuba4]

Originally Posted by Tuba4

In a prior answer it was stated that an appendage can fork outside the frame perimeter yielding a Y shaped appendage. Can an appendage be attached to the frame at 2 points and terminate in 2 points as long as they are joined by a cross member, yielding an H shaped appendage?

This question was just answered in the Q & A system.

"Yes but the contiguous part of the appendage must be outside the Frame Perimeter"

[MrForbes]

The conservative approach wins again....

[johnr]

...... and light saber test. I read this thread and still not sure about something. If you drew a tic-tac-toe game with center box being the robot and the center squares along the edges being were your app comes out, can the app enter into the corner boxes?

[Tuba4]

And here is another recent question and new answer which impacts our discussion here:

Q. Will you please either clarify the ‘appendage’ definition, or state the legality of an appendage design with two separate arms that extend beyond a single frame perimeter edge and driven by a single/common mechanism inside the frame perimeter? The related Q&A responses seem rather ambiguous. Thanks.

A. As the other responses indicate, there is no formal definition of "appendage". However, one appendage (as allowed in Rule [G21]) would be one contiguous assembly. The contiguous part of the appendage must be outside the Frame Perimeter.

[Dale]

This would seem to rule illegal all of the ball collection systems teams are making involving cylinders and discs with surgical tubing attached unless all of those pieces of tubing remain inside the framer perimeter at all times as the cylinder spins. Doesn't impact us but it will effect a lot of teams.

[Siri]

Originally Posted by Dale

This would seem to rule illegal all of the ball collection systems teams are making involving cylinders and discs with surgical tubing attached unless all of those pieces of tubing remain inside the framer perimeter at all times as the cylinder spins. Doesn't impact us but it will effect a lot of teams.

Unless the central pipe or part thereof also lies outside the frame perimeter. Right?

[Dale]

As that pipe moves out of the frame perimeter there's going to be a period of time where you have more than one appendage for a fraction of a second. Unless the GDC makes another ruling that would seem to be a violation. I suppose you could build one that only has tubing on one side and a way to stop it with that tubing facing inwards to park but it wouldn't be fun.

[Tuba4]

Originally Posted by Siri

Unless the central pipe or part thereof also lies outside the frame perimeter. Right?

I would agree with this assessment. But it would mean that whole assembly would need to be able to be retracted into the robot at the start of a match and then extended for use.

[Brandon Holley]

Originally Posted by Dale

As that pipe moves out of the frame perimeter there's going to be a period of time where you have more than one appendage for a fraction of a second. Unless the GDC makes another ruling that would seem to be a violation. I suppose you could build one that only has tubing on one side and a way to stop it with that tubing facing inwards to park but it wouldn't be fun.

This would be true for any "H" shaped manipulator as well. As you extend the entire appendage out side the perimeter there will inherently be a time period where just the prongs from the H stick out, even if when the H is fully extended it satisfies the contiguous criteria.

-Brando

[Dale]

I've submitted a Q&A on this.

[Squillo]

If they had just added three words, it would all be clear(er).
"The contiguous part of the appendage must be outside the Frame Perimeter at all times" (Italics were ADDED BY ME, NOT part of the actual GDC answer!)

If they'd just added those words. Not that I'd WANT those words, but it is STILL "clear as mud".

If you "extend" your "H" shaped appendage so that it is vertical (prongs of H sticking up) until fully outside the perimeter, then flip it down, it might satisfy the "at all times" requirement. Still a pain in the butt.

But maybe they didn't put "at all times" for a reason. Maybe it's OK to briefly have two prongs outside the perimeter. But what if your robot broke at exactly that point and you couldn't get it further out? Penalty! And who defines "briefly"? This is a quagmire and I think the GDC knows it.

Should have had a lawyer on the committee from the 'git go'... it's our job to avoid this kind of ambiguity! (Not that we always succeed.)

[Bob Steele]

Originally Posted by Squillo

If they had just added three words, it would all be clear(er).
"The contiguous part of the appendage must be outside the Frame Perimeter at all times" (Italics were ADDED BY ME, NOT part of the actual GDC answer!)

If they'd just added those words. Not that I'd WANT those words, but it is STILL "clear as mud".

If you "extend" your "H" shaped appendage so that it is vertical (prongs of H sticking up) until fully outside the perimeter, then flip it down, it might satisfy the "at all times" requirement. Still a pain in the butt.

But maybe they didn't put "at all times" for a reason. Maybe it's OK to briefly have two prongs outside the perimeter. But what if your robot broke at exactly that point and you couldn't get it further out? Penalty! And who defines "briefly"? This is a quagmire and I think the GDC knows it.

Should have had a lawyer on the committee from the 'git go'... it's our job to avoid this kind of ambiguity! (Not that we always succeed.)

By adding that the appendage has to pass the contiguity test outside the frame perimeter the rules are further muddied... as you mentioned..

My opinion would lead to a definition that would simply state that this outside the frame perimeter contiguous requirement should not read at all times but rather should read after deployment.

This would make the Y-shaped appendage legal (as was stated in an earlier Q and A) Presently, given the initial answer for the Y shaped appendage which was "OK" one could only assume that during deployment it was permissible to "lead" with the forks. If forks are ok... then the outside the frame contiguity "at all times" is not consistent... You would have to have a triangle leading rather than a fork. (I would imagine that triangle would not work like a fork...

I would hope that Q and A makes it clear that they really mean "After Deployment"

I know this does not help those teams that were designing a cylinder with little tubing arms sticking out side the frame perimeter... but it would at least clear up the situation...and make the earlier QA answer regarding the forked appendage consistent with the new revelation of "contiguous outside the frame perimeter"