Design of a tether‐driven minimally invasive robotic surgical tool with decoupled degree‐of‐freedom wrist

Abstract

Background: Dexterous surgical tool wrists used in tele-operated robotic surgery typically have mechanically coupled pitch and yaw degree of freedom (DoF). This leads to complex control requirements. Materials and Methods:The design of a robotic surgical tool with a mechanically decoupled dexterous wrist which uses stationary tether guides to guide drive tethers is presented. The tethers are routed through the plane of symmetry of the tool and follow law of belting to mechanically decouple the wrist. An optimization procedure for the placement of the stationary tether guides to minimize the change in tether length is presented.Results: Experimental and analytical results confirm the decoupled motion capability of the wrist. Also, the change in length of tether segments over the operating range of motion was found to be very small. Conclusion:A prototype has been fabricated through metal 3D printing and integrated to a tele-operated robotic setup to demonstrate its utility in surgical application. K E Y W O R D S additive manufacturing, articulated wrist, decoupled wrist, law of belting, minimally invasive surgery, rapid prototyping, robotic surgical tool, tether drive 1 | INTRODUCTION Robotic-assisted laparoscopic surgery has revolutionized minimally invasive surgical procedures by reducing patient recovery time and providing increased dexterity of movement to perform complicated procedures. 1,2 The da Vinci surgical system from Intuitive Surgical Inc is currently the predominant tele-operated robot indicated for urological and various other general laparoscopic surgical procedures. 3 The robotic surgical tool of da Vinci, known as EndoWrist has an articulated wrist with four controllable degree of freedom (DoF) for increased dexterity. These DoF are wristed pitch, wristed yaw, roll, and grasp, in contrast to only two DoF (roll and grasp) of a standard laparoscopic tool. These additional DoF help restore some of the lost dexterity associated with a manual laparoscopic tool and provides the surgeon a much more intuitive feel for performing a surgical procedure. 3 The dexterity offered by robotic surgical tools comes at the cost of increased mechanical complexity of the tool wrist since they have more DoF than conventional laparoscopic tools. Typical surgical tool designs with rigid shaft have the drive actuators placed at the distal end of the tool and an articulated wrist with graspers at the end effector of the tool. The power transmission system for such robotic surgical tools with multiple DoF is typically tether driven, 4-8 although designs based on concentric tube drive 9 and rigid link-based power transmission 10 are also reported in literature. Tether drive is a preferred mode of power transmission since it has a minimum number of components and simplifies mechanical construction without compromising the range of motion of the wrist. By design, EndoWrist has coupled yaw and pitch DoF, which means actuating only pitch DoF causes movement of yaw DoF as well. This movement of the graspers (about yaw DoF) is u...

Microrobotic laser steering for minimally invasive surgery

“…Common to many of these procedures is the need for wristed articulation at the distal ends of tools for manipulating tissue and visualizing the surgical site (1). This was an important motivation for introducing robotics into minimally invasive surgery (2) and remains a vibrant area of research and development today (3)(4)(5).…”

OpenRST: An Open Platform for Customizable 3D Printed Cable-Driven Robotic Surgical Tools

“…As the distances between the entry/exit holes in the base link are different for the cables C 1 and C 2 , the diameter of the jaw pulleys also differs, with the diameter of jaw pulley 2 being larger than the diameter of jaw pulley 1. This helps prevent cables from sliding off the pulleys and increases the useful life of the tool [27]. Additional guide rods placed on the pitch link align the center of the incoming cable with the jaw pulleys' midplane.…”

“…Podolsky et al [25] proposed the use of stationary guide arcs for the design of the wrist of tools. This idea was further explored in [26] and [27]. Jinno [26] proposed a non-interference mechanism to decouple pitch and yaw joints consisting of optimized arc-shaped guides.…”

“…Jinno [26] proposed a non-interference mechanism to decouple pitch and yaw joints consisting of optimized arc-shaped guides. Chandrasekaran and Thondiyath [27] followed a similar approach but considered a guide rod and the principle of the law of belting in their arc-shaped optimization.…”