A Mechanism for Dexterous End-Effector Placement During Minimally Invasive Surgery

Abstract

Presented here is the design of a mechanism for dexterous placement of an end-effector during minimally invasive surgery. A literature review is presented to show that capabilities of the mechanism are unavailable in current instrumentation. Apart from actuation of the end-effector, our mechanism provides 180° bi-directional articulation relative to the support tube and rotation of the end-effector about the articulated axis. These are accomplished via a compact multi-link structure comprised of gears and gear-links that provide excellent stiffness, load capacity and durability. The structure is optimized to have a large and dexterous workspace, low backlash, and small force magnification. Maximization of load capacity and durability of the complete mechanism is achieved by the use of high strength stainless steels, gears with 25° pressure angles to accommodate larger sized teeth, optimized gear pack thicknesses to distribute stresses evenly, and a compact forceps design to reduce tip length. Resistance to pitting is improved by alternating materials and/or hardness of materials between mating parts. The instrument is capable of supporting 4.5 N needle tip loads with infinite life expectancy and loads up to 8.7 N intermittently.