[Justin Ridley]

FIRST Community, we, the Robonauts, went out on a ledge this year by designing a feature on Endeavour that some thought might not be doable and even more thought might not be legal. As for the engineering of the problem, for us, it has been very exciting and VERY challenging ... the students and mentors have all become better designers by creating the "Robot On The Ledge". As for the legality, we posed many of the same questions as you have concerning whether hanging is covered under G10 and waited for weeks for clarification. Although it would take volumes to document our discussions, please allow us to explain why we feel this design, and others like it, falls within the intent of the rules.

The FIRST manual opens asking something of the teams; " When reading these rules, please use technical common sense (engineering thinking) rather than “lawyering” the interpretation and splitting hairs over the precise wording in an attempt to find loopholes." We have used this as a guideline, and to the best of our ability followed this model. We feel FIRST could have been more clear with their intentions, but alas we have happily worked with what we've been given. We began this season striving to find an innovative solution that fit within the realm of options presented within this year's game challenge. The intent of the challenge is for a robot to be fully supported by a balanced bridge in a way that does not damage the field components.

From the manual there are two game rules and a dictation in the arena section that govern a successful balance.

[G10]
Robots may not grab, grasp, grapple, or attach to any Arena structure. Robots may not push or react against the top of the Fender. (Robots may push or react against any element of the Arena that is not protected by another rule.)

[G12]
Robots may not damage any part of the Arena, including Basketballs.
Violation: Potential Disablement if the Head Referee determines that further damage is likely to occur.

A Bridge will count as Balanced if it is within 5° of horizontal and all Robots touching it are fully supported by it.

Our design uses a fixed downward facing C-shaped appendage on the end of an arm. The appendage is driven down with the gap of the C-shape coming to rest over the angled rail of the bridge. When the arm continues to travel down the robot angles slightly as it is lifted to become supported by the bridge. When slightly angled, the two inner walls of the C-shaped appendage merely react the load of the robot against the inside of the angled bridge rail and the outside features of the bridge. We believe this two point reaction of a fixed mechanism to support our robot weight falls within the intent of the rules because it is clearly written that robots may push or react against any element of the Arena. This simple reaction of forces is demonstrated by the robot being removed from the bridge simply by lifting it straight up. Our intention was actually to drive along the rail while maintaining this two point reaction... an engineering challenge we have not yet been successful at achieving with a fully weighted robot.

We would venture to say that the rule prohibiting the actions of grab, grasp, and grapple are of peoples primary concern, so let us elaborate on how our team understands the rules. To grab, grasp, or grapple you need actuation. Any reasonably astute thinker would agree that to grab or grasp a pencil off of a desk you would need to actuate or squeeze your fingers together. Grapple is a less commonly used verb and we believe inherently brings in some discrepancies because of this. When we use grapple, we often describing someone grabbing another person with their arms in a fight. We tried to look up grapple in the engineering bible (AKA the Machinist Handbook) but it was a dead end. So we turned to our home dictionary where grapple as a verb is defined with phrases "to hold", "to seize in a firm grip", "to clinch", "to engage in a struggle", and "to try to overcome". Like grab and grasp, these phrases bring to mind thoughts of actuation to accomplish the action. Our design is fixed and does not allow us to take "firm grip" of the bridge. We would venture to say that a fair amount of confusion arises from trying to relate the verb "grapple" to the mechanism known as a "grappling hook". We believe these are different parts of language used to describe different things and the latter should remain irrelevant and out of the discussion when attempting to clarify the verb grapple.

Briefly we will mention that adequate measures have been taken to prevent any damage to the field, including hang calculations for bending, analysis for localized deformation, and extensive testing on our bridge for scarring. There is a zip tie near the center of the bridge that to the best of our testing knowledge, we do not cut when a loaded weight crosses it. There are LEDs within the bridge c-channel structure that we do not interact with.

Questions have been raised throughout the season to FIRST alluding to this strategy. With each question we eagerly awaited an answer that would give us better direction one way or another. The opportunities were presented in the Q&A system for FIRST to make a clear and concise ruling on what they intended to be illegal actions and what they didn’t. They did not take this opportunity, which we feel is a move (albeit a frustrating one) to leave the challenge open and create opportunities for innovation.

We have no intention of cheating the system, gaining an unfair advantage, or exploiting the rules (we're not even sure how well our strategy will work in this game). We also understand others may disagree with our interpretations. Regardless of the ruling, the Robonauts will be better because of our efforts.

Thanks for your input,
The Robonauts