Chapter 6 - Parallel Wrists: Limb Types, Singularities and New Perspectives

This chapter reviews the criteria to identify the limb architectures suitable for parallel wrists (PWs) and the instantaneous kinematics of PWs. Special attention will be given to the use of the screw theory and of the displacement groups. The relationship between the limb architecture and the resulting PW mobility will be discussed. The main results reported in the literature about the singularity analysis of PWs will be summarized and the problem of characterizing the kinetostatic performances of PWs will be addressed. Eventually, innovative wrist architectures, recently proposed, will be presented