Asymmetric Drive Cable Layout for Equivalent Compliance
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Solution Overview
Problem
Cable driven motion systems in robotic surgical systems often face control complications due to differing compliances in drive cables, resulting from varying pathway lengths and materials, which can lead to inaccurate wrist motion and jaw actuation.
Innovation Solution
The implementation of a cable driven drive system with an asymmetric layout of drive inputs, where each drive cable is composed of multiple sections with separate stiffness achieved through different materials, cross-sections, and braid constructions, allowing for adjustment to create equivalent compliance between drive inputs, thereby simplifying control schemes and enhancing performance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cable driven motion systems use multiple drive inputs with different pathway lengths, then the system can achieve complex wrist articulation and end effector positioning, but the different cable pathway lengths result in different compliances for each drive input causing control complications
Solution Approach 1:
The patent modifies the physical parameters of the drive cables by introducing compliance adjustment mechanisms that allow the compliance of each cable to be tuned independently. This enables the system to maintain equivalent compliance across all drive inputs despite having different pathway lengths, thereby resolving the control complications while preserving the versatile wrist articulation capability
Solution Approach 2:
The patent introduces compliance adjustment mechanisms as intermediary elements between the drive inputs and the cable driven motion system. These intermediaries act as compliance matching devices that equalize the compliance characteristics of cables with different pathway lengths, simplifying the control system by eliminating the need to compensate for compliance differences
2Volume of moving object
If drive cables have different pathway lengths and materials, then the system can accommodate asymmetric drive input layouts for compact design, but this results in different compliances that complicate control
Solution Approach 1:
The patent adjusts the compliance parameters of individual drive cables through modification of cable characteristics such as material composition, cross-sectional area, or introduction of compliance adjustment mechanisms. This allows the system to maintain equivalent compliance across all drive inputs despite asymmetric pathway lengths, thereby preserving the compact design while improving control simplicity
Solution Approach 2:
The patent embraces the asymmetric layout of drive inputs rather than attempting to symmetrize the system. By introducing compliance adjustment mechanisms, the system can accommodate the asymmetric geometry and achieve equivalent compliance, thereby maintaining the compact design benefits while eliminating control complications
Data Source
AI summary
A surgical tool includes a drive housing having opposing distal and proximal ends, first and second drive cable capstans arranged within the drive housing and asymmetrically aligned between the distal and proximal ends, a first drive cable extending distally from the drive housing and actuatable by operation of the first drive cable capstan, and a second drive cable extending distally from the drive housing and actuatable by operation of the second drive cable capstan. A stiffness of the first and second drive cables is equalized by adjusting one or more characteristics of one or both of the first and second drive cables.