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Official Q&A: VRC 2018-2019: Turning Point

Usage Guidelines All Questions

262: Roller Intakes and Entanglement

Jerry Palardy (Event Partner)
11-Mar-2019

Many of this year's robots have a ball intake like a paddle wheel wrapped in rubber bands or elastic (like the attached picture). The rubber bands often get entangled in other robots. How should a referee handle a match when the outcome is dependent on an entanglement? As reference the game manual defines entanglement as:

"Entanglement – A Robot status. A Robot is Entangled if it has grabbed, hooked, or attached to an opposing Robot or a Field Element."

That definition fits this scenario. In addition, rule R3c says:

"The following types of mechanisms and components are NOT allowed: ... c. Those that pose an unnecessary risk of entanglement."

"Unnecessary" is the key word here. There has been no precedent for robots with this type of intake failing inspection (that I know of), and I wouldn't expect that to change now, but I'll still ask. Is this type of intake legal?

Beyond that the rules don't provide much guidance for referees to handle situations where two robots become entangled for a long period of time affecting the outcome of a match. This seems like a question that would have been asked early in the season, and maybe I'm missed it, but I don't see anything in the official Q&A.

The answer might depend on how the entanglement occurred. So here are three scenarios. In each scenario the Red robot has the roller intake that becomes entangled in the blue robot. The entanglement occurs with 30 seconds left in the match and the robots are unable to separate. Neither robot can move or score after being entangled. The final score is 16-15.

  1. Red robot is playing defense and engages with blue when entanglement occurs.
  2. Blue robot is playing defense. Red robot is playing offense, but does not attempt to protect intake from blue.
  3. Red is offense, blue is playing defense aggressively. Red attempts to protect intake from blue, but still becomes entangled. Referee believes that blue purposefully become entangled.
  4. (OK one more). Referee didn't see it happen. Red and blue both claim the other is at fault. img
R3   Other  
Answered by Game Design Committee

Is this type of intake legal?

Yes, the intake in the attached photo appears to be legal, in the context of this question regarding Entanglement hazards (i.e. we can't see if there are any 3D printed parts, or check if the rubber bands are of legal width, etc). The intent of <R3c> is to prohibit mechanisms which serve no primary purpose other than Entangling opponents (e.g. a net).

Beyond that the rules don't provide much guidance for referees to handle situations where two robots become entangled for a long period of time affecting the outcome of a match.

There are a several key rules that apply in this interaction. First, <G12b>:

b. VEX Robotics Competition Turning Point is an interactive game. Some incidental tipping, Entanglement, and damage may occur as a part of normal gameplay without violation. It will be up to the head referee’s discretion whether the interaction was incidental or intentional.

And its related rule, <G13>:

<G13> Offensive Robots get the “benefit of the doubt”. In the case where referees are forced to make a judgment call regarding a destructive interaction between a defensive and offensive Robot, or an interaction which results in a questionable rules violation, the referees will err on the side of the offensive Robot.

And finally, <G12c>:

c. A Team is responsible for the actions of its Robot at all times, including the Autonomous Period. This applies both to Teams that are driving recklessly or potentially causing damage, and to Teams that drive around with a small wheel base. A Team should design its Robot such that it is not easily tipped over or damaged by minor contact.

These rules all combine to form the following overarching guideline regarding "rubber band intakes":

  • A Robot with this type of mechanism is assuming the potential risk of Entanglement.
  • Teams who build mechanisms with Entanglement hazards are responsible for minimizing this risk, or accepting the potential inevitability of becoming Entangled with an opponent.
  • A Robot with a "rubber band intake" who becomes Entangled with an opponent generally would not result in a <G12> violation on their opponent, because it is inherently the rubber band Robot's "fault" for assuming that risk, per <G12c>.
  • However, that "fault" does not immediately flip to a <G12> violation on the rubber band Robot, because this intake is generally being used for an inherently offensive maneuver, per <G13>.
  • In short, under normal gameplay (as judged by the Head Referee), there would be no violations on either Team.
  • Of course, all of the above is superceded by <G12> if the Head Referee determines that the Entanglement was intentionally or egregiously initiated by either Robot (e.g. the rubber band Robot is defending and "intakes" their opponent with no Balls nearby or other reason to have the intake; or, the non-rubber-band Robot is defending and puts out a "claw" which is immediately ensnared by the intake).