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  Coordinate and angle conventions for the RiSE climbing robot platform

         created by Uluc Saranli Wed Apr  7 15:20:18 EDT 2004
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$Id: CONVENTIONS.txt,v 1.1 2004/07/16 20:31:13 AMcClung Exp nobody $
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 This file describes all the conventions adopted in the RiSE platform,
as seen from the perspective of the behavioral programmer.

 RiSE climbing robot is a six legged platform with two degrees of
freedom per hip. For each hip, the "wing" degree of freedom controls
the sideways extension of the leg assembly, while the "crank" degree
of freedom controls the crank extension that drives the four bar leg
structure.

 Seen from the TOP, the coordinates of the robot body and the
numbering of the legs is illustrated by the following diagram:


                            nose
                        -----------
              leg 0 ---|           |--- leg 3
                       |           |
                       |   Y       |
                       |   ^       |
              leg 1 ---|   |       |--- leg 4
                       |   +--->X  |
                       |           |
                       |           |
              leg 2 ---|           |--- leg 5
                        -----------

        DIAGRAM 1 : Leg numbering and body coordinates

 The wing angle is measured from the vertical configuration of the
leg, increasing as the leg assembly lifts upwards. So, seen from the
FRONT of the robot, the following diagram illustrates our convention
for the wing degree of freedom.


                            -----------
  wing = pi/2  ---------   |   nose    |   --------- wing = pi/2
                  ^     |  |           |  |    ^
                   \    |  |           |  |   /
                     -  |   -----------   | -
                        |                 |
    
                     wing = 0          wing = 0


               DIAGRAM 2 : Wing angle conventions

 Finally, the crank angles are chosen such that they are 0 when the
crank is pointing upwards (the shortest configuration of the four bar
assembly) and rotates such that positive angle progression means
forward locomotion on flat ground. In other words, positive angle
progression is seen as counterclockwise rotation of the crank seen
from the right side of the robot. The following diagram illustrates
the conventions


                                crank = 0

                                    |
              ----------------------|------
             |                      |       \
             |  crank = pi/2  ------         | nose   -> forward (+Y)
             |                              /
              -----------------------------


               DIAGRAM 3 : Crank angle conventions