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Originally Posted by DMetalKong
Let me try my hand at this:
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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)
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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.