Design and synthesis of wire-actuated universal-joint wrists for surgical applications

This paper presents synthesis methods and performance measures for wire-actuated wrists using a universal-joint constraining linkage. Performance measures based on the isotropy of the wrench-closure workspace are derived and used in generating design atlases as a function of non-dimensional design parameters. The performance indices that are optimized include wrench-closure workspace, isotropy of the wrench-closure workspace, and kinematic conditioning index. Stiffness is used to define a safety margin from singularities of wrench closure. A design example of a wire-actuated surgical wrist is presented and validated through simulation. The methods presented in this paper are useful for quick dimensional synthesis of wire-actuated wrists with predefined wrench-closure workspaces.