Just wondering how may teams out there are awaiting a “helpful” reply to this question relating to the legality of (what many consider) one appendage that has two parallel arms attached mechanically and structurally so that they act as a singular appendage as they pivot to extend outside the robot…
Game - The Game » Robot Actions » G21
Q. If two members of a mechanism crosses one edge of a robot in two locations but the two members are connected via one axle and are controlled by one motor is this still considered one appendage?
Answer is in pending state
FRC1221 2012-01-14
So do you go ahead and build this “appendage” knowing that sometime down the road you may or may not find out your time and effort was worth it?
Honestly I think this has more reason to be the most anticipated Q&A response.
It may even be considered allowable to have two separate mechanical extensions, but that are otherwise linked to always operate in tandem and in a repeatable fashion (via code), count as a single appendage. But it would be really nice to know for sure. I’m hoping for an answer in the update tomorrow, or at the very least soon in the Q&A.
As for what to do in the meantime: have contingency plans; come up with and test ideas that work in multiple scenarios. Since we are not in a rush to build anything final until about a week from now, we can wait a short while to know what’s right, but we don’t have all the time in the world. If you are running out of time, go with what’s safe, an appendage which is undeniably a single appendage.
That’s the one thing I don’t understand. The Q&A has probably half a dozen questions on appendages alone, and a number of them are “does this scenario count as an appendage?” type questions. I would think that the GDC would see that this is an issue that needs answering. So why hasn’t it been answered?
My guess is, whichever GDC member is the “appendage rules expert” hasn’t seen the Q&A yet. (It seems that certain question types are answered in groups, both last year and this year; this leads one to speculate that various GDC members are experts in various parts of the Manual. I don’t know if this is actually the case, however.) If that is the case, then hopefully another GDC member nudges him/her to answer… some of these questions have been kicking around for a week now.
I seriously hope they realize that defining an appendage based on its construction is a losing game.
Thought experiment: I have a plastic toy trident which can be installed on my robot in several possible orientations, and which can be actuated in several ways during a match. (Imagine the craziest possible positions for this thing, with varying degrees of overhang, flexibility, etc…) If I poll 5 trained, experienced referees about the legality of all of these configurations, can I expect to get 5 identical, correct sets of answers? What if I repeat the test with 5 GDC members?
Almost certainly, the answer is no. Nobody knows what an appendage is, or where it begins, because that definition is not in the rules, and does not obviously follow from an ordinary person’s understanding of any given robot design.
Mechanisms can do all sorts of weird stuff, and can take all sorts of forms. You don’t want to end up with a definition that makes something an appendage in some positions, and two or more appendages in others. It’s also a bad idea because it’s non-obvious, and will be full of nuanced interpretations. Good luck getting every referee to call that the same way every time.*
The real way forward is to fix the definitions of frame perimeter and side (so that they properly account for curvilinear figures, and elegantly handle projections into the corners adjacent to two sides), and then allow only one side to be overhung at a time. No mention of what’s overhanging, or how many—just a clear test that be applied by a referee with no knowledge of how various mechanisms are actuated.
*That’s most assuredly not a slight against referees. The fact is, all officials will struggle with complicated definitions applied to complicated robots. Referees have the additional problem that their struggle takes place in real time, in front of an audience. The stakes are high for them, and they’ll be expected to get this right. That’s not easy.
They are probably just waiting on wording. Look at the simulator, they have the type of appendage you’re talking about. The intent of the rule is not to spread out multiple sides like wings, etc., is my guess.
A. There is no explicit width limit for a Robot appendage. Per Rule [R21], “Robots may extend one appendage up to 14 in. beyond a single edge of their Frame Perimeter at any time.”
A. There is no formal definition of appendage, however a colloquial definition is “a subordinate part attached to something; an auxiliary part; addition” (courtesy of disctionary.com). To elaborate, an Appendage is a contiguous assembly that may extend beyond the Frame Perimeter per Rule [G21].
Contiguous - From Websters
1: being in actual contact : touching along a boundary or at a point of angles
2: adjacent 2
3: next or near in time or sequence
4: touching or connected throughout in an unbroken sequence <contiguous row houses>
So it appears according to today’s answers that a mechanical linkage, e.g. a mechanically contiguous assembly in any way, will be considered a single appendage. No mention of whether this connection is inside or outside the frame means that it doesn’t matter. Good to know this is the way they are thinking, and beyond that I think we can safely use common sense.
This now opens up the question that if its two mechanically independent systems operating in unison (and assumedly being used for the same/similar task), does this still satisfy the requirement?
I would think not, and probably call it out as ref/inspector, because of how they appeal to a colloquial definition of appendage, regardless of function. I would want to see a mechanical connection.
Then of course you could tie a string between them to make them “contiguous,” but I think that’s why they don’t want us lawyering the rules.
I suspect the given answer is a relief for many teams who have spent many days developing flip out, push out linked arm appendages… the GDC got this one conceptually right.
The key issue as I see it is whether or not multiple mechanisms that have either an interrelated/coordinated functional purpose or completely independent functional purposes, can be “contiguously” combined on a single arm that extends beyond the robot’s “single edge” (this term is totally vague too - what happens if you deploy off a corner: can you go out 14" X 1.414?).
As long as various mechanisms & their components are purposed for one one function and are contigouosly attached to a single extension arm, this would seem to be within the “spirit” of the rule.
However, what happens if your appendage can extend to grab balls off the floor and then swing up, allowing ball transfer to a separate, but still arm-attached, shooter assembly, that proceeds to fire a scoring shot? Does this violate the “spirit” of the rule. Does the “spirit” of the rule imply only a single functional purpose per each appendage?
Anyone else notice that this has changed (in the Q&A)?
Q: What is the Definition of “Appendage”?
NEW answer:
A. There is no formal definition of appendage, however a colloquial definition is “a subordinate part attached to something; an auxiliary part; addition” (courtesy of disctionary.com). To elaborate,*** an appendage, when extended beyond the Frame Perimeter, is a contiguous assembly***.
OLD answer:
A. There is no formal definition of appendage, however a colloquial definition is “a subordinate part attached to something; an auxiliary part; addition” (courtesy of disctionary.com). To elaborate, an Appendage is a contiguous assembly that may extend beyond the Frame Perimeter per Rule [G21].
I have to assume that this change was intentional, and has meaning. I interpreted the OLD answer to mean that as long as it was contiguous, it could extend past the perimeter. The NEW answer seems to mean that it must be “continguous” past the perimeter. So if the connection is within the perimeter, and it’s two separate things outside the perimeter, then it’s two appendages, even though they are connected?
Help?!!! This is so confusing (and critical to our team - we thought we were OK but now I’m not so sure). I have a feeling the GDC will just keep repeating this (new) answer, but what do you all think it means?
To me that seems to be a good point. Additionally, I’d say that they wanted to say that appendage rules don’t apply within the vertical perimeter (remembering the vertical cylinder from last year.
Additionally, I’d imagine that your point would be handled very leniently. Imagine one of the hands from last year with two prongs that grab the tube (this year the ball) and are 4 inches long, but the mechanism holding them takes up your other 10 inches. Withdrawn into the robot and facing out, you then have to extend them. At some time only 2 inches are protruding. By rule they are seperate appendages, but not in practice and therefore I think that they will not be ruled as such.
I’d play it safe and have something that connects the two arms at the outer ends. It’s a pain, but it’ll save having to deal with the issue later when they finally come out and say that’s what they meant all along.
edit: and a bonus, it’s less likely to poke into other robots
My totally unofficial, but unambiguous interpretation of the writings of the GDC.
An appendage is considered a single appendage if, during its normal extension for usage outside the frame perimeter, all appendage components which intersect the frame perimeter projection are contiguously connected entirely outside the frame perimeter projection.
This would allow a ‘fork’ like appendage to not break the rule when only the tines of the fork are intersecting the frame perimeter during its deployment, but the normal usage of the fork appendage would need to be such that the portion connecting the tines must also be out of the perimeter projection as it is used.
And I don’t think it matters if one tine of the fork is used to manipulate balls, and the other tine is used for moving the bridge – multipurpose appendages are fine.
I would have to respectfully disagree with this line of reasoning. Other than the fact that it is redundant (“contiguously connected”) a
contiguous assembly must mean that it is simply connected… the new answer does not say that it has to be contiguous OUTSIDE the frame perimeter. I quote directly from Q&A:
" To elaborate, an Appendage is a contiguous assembly that may extend beyond the Frame Perimeter per Rule [G21]."
I looked at the old wording “an appendage, when extended beyond the Frame Perimeter, is a contiguous assembly” and this simply doesn’t make sense…you can’t define a contiguous assembly as one that extends beyond the frame perimeter…you define it by the definition of contiguous (ie connected). They were simply cleaning up the answer.
If it looks like an appendage, quacks like an appendage and moves like an appendage…it is an appendage… contiguous means connected…connected could possibly mean moving all at once… but wouldn’t have to …
I think that Q and A is sufficiently clear on this topic. I also think it is unambiguous.
But how could you possibly EVER have two appendages exiting from the same edge then? If they can be connected inside the perimeter, then any thing you want to call two appendages on the same edge will be one by your definition — unless one is totally disconnected from the bot, which of course violates a different rule. By your line of thinking, I can have any configuration whatsoever for appendage(s) as long as they all exit the perimeter along the same edge-- they are always connected to each other somehow via the bot parts.