Dual Axle Robotic End Effector Mitigating Galling
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Solution Overview
Problem
Robotic surgical systems experience elevated friction and cable breakage due to galling issues in the axle of cable-driven end effectors, particularly when used with instruments having opposing jaws or blades that rotate independently, which reduces the lifespan of the drive cables.
Innovation Solution
The implementation of a dual axle construction where a sleeve axle interposes the primary axle and jaw holders, providing an increased bearing surface and mitigating galling, along with the use of wear-resistant coatings to reduce friction and wear, effectively addressing the galling problem.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single axle is used to govern articulation of the end effector, then the device complexity is low, but galling occurs between the axle and jaw holders which increases friction and reduces cable life
Solution Approach 1:
The single axle is segmented into two separate axles: a first axle that governs yaw motion and a second axle that governs pitch motion. This segmentation eliminates the galling problem between the single axle and jaw holders by distributing the articulation functions across two separate axles, thereby reducing friction and extending cable life while maintaining manageable device complexity through modular construction.
Solution Approach 2:
A second axle is introduced as an intermediary element between the first axle and the jaw holders. This intermediate axle acts as a mediator that transfers motion while preventing direct contact and galling between the primary axle and the jaw holders, thus reducing friction and wear on the cable system.
2Measurement precision
If drive cables are maintained at elevated tensile loads to ensure accurate end effector articulation, then articulation precision is improved, but the axle begins to gall which generates excess friction and contributes to cable breakage
Solution Approach 1:
By segmenting the articulation system into two separate axles with distinct functions (yaw and pitch), the system maintains accurate articulation control through precise cable tensioning while preventing galling that would lead to cable breakage. Each axle handles specific motion control, reducing overall friction and wear on the cable system.
3Ease of operation
If jaw holders rotate independently against the axle to enable articulated movement, then the end effector achieves natural hand-like articulation, but galling between the axle and jaw holders increases friction and reduces cable life
Solution Approach 1:
The independent rotation of jaw holders is achieved through segmented articulation where the first axle governs yaw motion and the second axle governs pitch motion. This segmentation allows natural hand-like articulation freedom while preventing galling by eliminating direct contact between a single axle and multiple jaw holders, thereby extending cable lifespan.
Solution Approach 2:
The second axle serves as an intermediary that enables articulated movement of jaw holders without direct contact between the primary axle and jaw holders. This intermediate element facilitates natural hand-like articulation while preventing galling and reducing friction, thus preserving cable integrity and extending service life.
Data Source
AI summary
An end effector includes a distal clevis, an axle mounted to the distal clevis, a first jaw holder and corresponding first jaw member rotatably mounted to the axle, and second jaw holder and corresponding second jaw member rotatably mounted to the axle. A cylindrical sleeve axle having opposing first and second ends and defining a central passageway extending between the opposing first and second ends, the sleeve axle providing a continuously straight and uninterrupted outer surface extending entirely between the opposing first and second ends. The axle is received within the central passageway and the sleeve axle is rotatable relative to the axle.