Set of manipulating forces in wire driven systems

The manipulability for wire suspended mechanisms is discussed. For kinematics of a wire driven mechanism, we need not only the geometrical constraints of wire lengths but also the force constraints, such as the wire tension which should be always greater than or equal to zero. First, the sufficient and necessary mechanical conditions corresponding to the force constraints are shown. Under these conditions, we can obtain the manipulability of a wire driven mechanism using almost the same methods as for a popular multilink manipulator. Second, a more practical evaluation index "set of manipulating forces" is introduced and the way of calculation of this index is explained. We also derive both manipulability indexes as for wire suspended mechanisms in the gravity field by modeling the gravitational force as a wire having tension corresponding to gravity. Numerical examples are given to explain the proposed indexes and to show their validity. The method is expected to be effective in designing and task planning of wire driven systems including wire suspended mechanisms. >