Reconfigurable main-arm for assembly of all revolute-only kinematically simple branches

Within previous work by Podhorodeski and Pittens,(1) a class of kinematical ly simple (KS) joint layouts was defined for spatial serial joint-assemblie s consisting of revolute joints only. The identified KS class of layouts wa s comprised of main-arms with three successively parallel and/or perpendicu lar revolute joints and end located spherical joint groups. Arguments of de generacy and kinematic equivalency can be used to demonstrate that only fiv e unique main-arm layouts belong to the KS class. Within the current work, the design of a reconfigurable main-arm (RMA) allowing the construction of all of the KS branches is examined. Sufficient joints are included within t he RMA to allow, by the locking of certain joints and the freeing (actuatio n) of others, the kinematic attributes of each of the unique KS main-arm la youts to be acquired. It is concluded that five successively perpendicular revolute joints are required within the RMA to allow such reconfiguration. Inverse kinematic solutions are presented for each of the five layouts. Pot ential RMA applications, use of the RMA for kinematically redundant layouts , and an RMA prototype are discussed. (C) 2000 John Wiley & Sons, Inc.