[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.