Echelon form solution of direct kinematics for the general fully-parallel spherical wrist

This paper presents the echelon form direct position analysis of a class of fully in-parallel actuated mechanisms for the orientation of a rigid body with a fixed point. The mechanisms have a structure which is the most general one for manipulator spherical wrists with three degrees of freedom and fully-parallel arrangement. The analysis results in a two-equation system in echelon form; the first equation is of 8th order and the remaining is linear. As a consequence, when a set of actuator displacements is given, eight configurations of the mechanism are possible. A numerical example confirms the new theoretical result. © 1993.