Derivation of redundant wrist manipulators to avoid interior workspace singularities

Nonredundant manipulators with six joints have interior workspace singular configurations at which the manipulators lose one of their orienting degrees of freedom. Various types of workspaces, configuration space and boundary are defined in order to discuss the cause of manipulator degeneracies. The symbolic Jacobian is used to explore the singularities of a spherical wrist. The redundant spherical wrist, also examined through its symbolic Jacobian, is used to construct a redundant manipulator that can affectively avoid the interior workspace singular configurations