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Design Innovation

FlexDex™ : A Minimally Invasive Surgical Tool With Enhanced Dexterity and Intuitive Control

[+] Author and Article Information
Shorya Awtar

Precision Systems Design Laboratory, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109awtar@umich.edu

Tristan T. Trutna

Precision Systems Design Laboratory, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109ttrutna@umich.edu

Jens M. Nielsen

Precision Systems Design Laboratory, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109jensmn@gmail.com

Rosa Abani

Precision Systems Design Laboratory, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109rabani@umich.edu

James Geiger

C. S. Mott Children's Hospital, University of Michigan, Ann Arbor, MI 48109jgeiger@med.umich.edu

J. Med. Devices 4(3), 035003 (Sep 10, 2010) (8 pages) doi:10.1115/1.4002234 History: Received January 02, 2010; Revised July 16, 2010; Published September 10, 2010; Online September 10, 2010

This paper presents a new minimally invasive surgical (MIS) tool design paradigm that enables enhanced dexterity, intuitive control, and natural force feedback in a low-cost compact package. The paradigm is based on creating a tool frame that is attached to the surgeon’s forearm, making the tool shaft an extension of the latter. Two additional wristlike rotational degrees of freedom (DoF) provided at an end-effector that is located at the end of the tool shaft are manually actuated via a novel parallel-kinematic virtual center mechanism at the tool input. The virtual center mechanism, made possible by the forearm-attached tool frame, creates a virtual two-DoF input joint that is coincident with the surgeon’s wrist, allowing the surgeon to rotate his/her hand with respect to his/her forearm freely and naturally. A cable transmission associated with the virtual center mechanism captures the surgeon’s wrist rotations and transmits them to the two corresponding end-effector rotations. This physical configuration allows an intuitive and ergonomic one-to-one mapping of the surgeon’s forearm and hand motions at the tool input to the end-effector motions at the tool output inside the patient’s body. Moreover, a purely mechanical construction ensures low-cost, simple design, and natural force feedback. A functional decomposition of the proposed physical configuration is carried out to identify and design key modules in the system—virtual center mechanism, tool handle and grasping actuation, end-effector and output joint, transmission system, tool frame and shaft, and forearm brace. Development and integration of these modules leads to a proof-of-concept prototype of the new MIS tool, referred to as FlexDex™ , which is then tested by a focused end-user group to evaluate its performance and obtain feedback for the next stage of technology development.

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Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 10

Nested ring output joint and end-effector

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Figure 11

Existing enhanced-dexterity MIS tool (left) versus FlexDex™ (right)

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Figure 1

Minimally invasive versus traditional surgery (5)

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Figure 2

Traditional hand-held tool (11)

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Figure 3

Enhanced dexterity hand-held tool (20)

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Figure 4

Da Vinci surgical system (25)

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Figure 5

One-to-one DoF mapping between the surgeon’s input motions and tool output motions

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Figure 6

Proposed hand-held MIS tool configuration

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Figure 7

FlexDex™ : proof-of-concept prototype

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Figure 8

Surgeon wrist versus tool input joint: (a) collocation not possible due to physical interference and (b) collocation made possible by a VC mechanism

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Figure 9

Tool handle and gripper actuation

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