Compact 2-DOF Surgical Wrist for Stable Torque Transmission
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Solution Overview
Problem
Existing minimally invasive surgical tools lack the ability to effectively transmit desired torques and forces through compact articulated wrists, limiting their effectiveness in telesurgical tasks due to inadequate wrist mechanisms that mimic the natural action of a surgeon's wrist.
Innovation Solution
A surgical tool with a two-degree-of-freedom wrist mechanism, featuring an intermediate member pivotally coupled to an instrument shaft and an end effector body, allowing for angular orientation via linked tension members and internal passages to guide control cables, which inhibits changes in tension and enhances the transmission of torque through angled movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a compact articulated wrist mechanism is used in surgical tools, then the tool length is reduced and maneuverability is improved, but the ability to transmit desired torques and forces through the wrist is insufficient
Solution Approach 1:
The wrist mechanism is divided into multiple segments including a proximal link, distal link, and intermediate link, each capable of independent rotation about specific axes. This segmentation allows the compact structure to achieve complex articulation while maintaining torque transmission pathways through each segment, resolving the contradiction between compactness and force transmission capability.
Solution Approach 2:
The wrist mechanism incorporates rotation about two different axes (first axis and second axis) rather than a single axis, adding a dimensional aspect to the articulation. This multi-axis rotation enables the compact wrist to achieve greater operational freedom and maintain effective torque transmission in multiple directions, addressing both the length reduction and force transmission requirements.
2Ease of operation
If a two-degree-of-freedom wrist mechanism is implemented, then maneuverability and natural wrist action are enhanced, but the complexity of the device increases
Solution Approach 1:
The intermediate link serves multiple functions: it connects the proximal and distal links, provides rotation about the second axis, and acts as a pivot point for the end effector. This multi-functionality reduces the need for separate components, achieving enhanced maneuverability while controlling overall device complexity.
Solution Approach 2:
The wrist mechanism employs a nested arrangement where the intermediate link is positioned between the proximal and distal links, and the end effector is mounted on the distal link. This nesting allows the compact two-degree-of-freedom mechanism to achieve complex articulation without proportionally increasing device complexity, as components are efficiently space-utilized.
3Ease of operation
If control cables are routed through the wrist mechanism, then articulation is enabled, but changes in cable tension occur during angular movements
Solution Approach 1:
The control cables are routed along paths that maintain constant tension during wrist articulation, creating an equipotential condition where the cable length and tension remain stable despite angular movements. This is achieved through careful cable routing geometry that compensates for the changing positions of the links, ensuring stable cable tension while enabling full articulation capability.
Data Source
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AI summary
Surgical tools having a two degree-of-freedom wrist (70), wrist articulation by linked tension members (218, 220, 222, 224), mechanisms (372, 390) for transmitting torque through an angle, and minimally invasive surgical tools incorporating these features are disclosed. An elongate intermediate wrist member (80) is pivotally coupled with a distal end of an instrument shaft (74) so as to rotate about a first axis transverse to the shaft, and an end effector body (72) is pivotally coupled with the intermediate member so as to rotate about a second axis that is transverse to the first axis. Linked tension members (218, 220, 222, 224) interact with attachment features (180, 182, 184, 186) to articulate the wrist. A torque-transmitting mechanism (372, 390) includes a coupling member (384, 394), coupling pins (398, 400), a drive shaft (392), and a driven shaft (396). The drive shaft is coupled with the driven shaft so as to control the relative orientations of the drive shaft, the coupling member, and the driven shaft.