Analysis and Modeling of Wire-actuated Wrist with a Universal Joint

Abstract

The thesis presents the work on developing wire-actuated wrist for Minimally Invasive Surgery (MIS). The benefits of MIS is to minimize surgical trauma, reduce rate of complications, shorten execution time and accelerate patients’ recovery. But the motions of surgical tools are constrained to a pivot during MIS. The application of surgical wrist can help restore the degrees of freedom (DOF) and provide distal dexterity for the tools. The project includes modeling of kinematics, statics and wrench closure workspace for the wire actuated parallel robots with a universal joint. The topic of kinematics and statics presents analysis of direct/inverse kinematics as well as their validation by simulation, and of instantaneous kinematics/statics using virtual work principle and loop closure constraint method. The wrench closure workspace part defines the workspace while considering uni-sense wrench limitations and accounting for maximal deflections subject to a norm-bounded load on the wrist. The analysis also compared the effect of using three or four actuation wires on the kinematics, statics, wrench closure workspace and stiffness. The results can help guide the design of wire actuated parallel robots and surgical parallel wrists.