Optimal design of redundant parallel mechanism for endoscopic surgery

A kinematic concept of a redundant wrist with parallel structure is presented. This new device transforms the movement of four actuators acting along parallel directions of space, in a motion with three rotations around a fixed point. The properties of this new device are very interesting because they allow the direct mechanical coupling between a master system and a slave device. This mode of coupling allows us to realize teleoperation; moreover its thread-like morphology makes it well suited to the applications in the surgical field. This new redundant morphology is presented as well as a complete kinematic analysis which has shown that actuator redundancy not only removes singularities but also increases workspace while improving dexterity. Finally a dexterity measure and the optimal design of the mechanism are presented.