Dual-Friction Actuation Cable for Robotic Surgery
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Solution Overview
Problem
Robotically controlled surgical instruments face challenges with high friction at bends in flexible tubes, leading to stick-slip motion and difficulty in controlling small movements of end effectors, as existing systems either compromise on force or control due to friction requirements.
Innovation Solution
A surgical device with a cable system featuring two portions: a low-friction portion for end effector control and a high-friction portion for capstan engagement, utilizing different materials like Dyneema and Kevlar to manage friction effectively, ensuring smooth operation and significant force application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a low-friction cable is used, then the negative impacts of friction on end effector control are reduced, but the force that can be applied by the capstan is reduced due to cable slippage
Solution Approach 1:
The cable is designed with different friction characteristics in different sections: the first cable portion (distal section) has low friction for smooth end effector control, while the second cable portion (proximal section) has high friction for effective capstan engagement. This local differentiation allows each section to optimize for its specific function without compromising the other.
Solution Approach 2:
The cable is divided into two distinct portions with different material properties. The first portion uses low-friction material (e.g., PTFE, polyethylene) for the control section, while the second portion uses high-friction material (e.g., aramid, nylon) for the drive section. This segmentation enables the system to simultaneously achieve both low-friction control and high-friction force transmission.
2Force
If a high-friction cable is used, then the force that can be applied by the capstan is increased due to reduced cable slippage, but the control of the end effector is impeded
Solution Approach 1:
The cable is designed with different friction characteristics in different sections: the first cable portion (distal section) has low friction for smooth end effector control, while the second cable portion (proximal section) has high friction for effective capstan engagement. This local differentiation allows each section to optimize for its specific function without compromising the other.
Solution Approach 2:
The cable is divided into two distinct portions with different material properties. The first portion uses low-friction material (e.g., PTFE, polyethylene) for the control section, while the second portion uses high-friction material (e.g., aramid, nylon) for the drive section. This segmentation enables the system to simultaneously achieve both low-friction control and high-friction force transmission.
3Ease of operation
If friction is reduced to enable smooth control, then stick-slip motion is reduced, but the mechanical structures must be more robust to withstand forces, making small-diameter construction difficult
Solution Approach 1:
The cable is designed with different friction characteristics in different sections: the first cable portion (distal section) has low friction for smooth end effector control, while the second cable portion (proximal section) has high friction for effective capstan engagement. This local differentiation allows each section to optimize for its specific function without compromising the other.
Solution Approach 2:
The cable is divided into two distinct portions with different material properties. The first portion uses low-friction material (e.g., PTFE, polyethylene) for the control section, while the second portion uses high-friction material (e.g., aramid, nylon) for the drive section. This segmentation enables the system to simultaneously achieve both low-friction control and high-friction force transmission.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The dual-friction cable system reduces stick-slip motion and enhances control of end effectors while maintaining sufficient force transmission, facilitating precise robotic control and construction of small-diameter flexible surgical instruments.
Implementation Method 1
a first cable portion having low friction properties when engaging a surface of a drive mechanism
Implementation Method 2
a second cable portion having high friction properties when engaging a surface of a drive mechanism
Data Source
Figure 1~3
Figure 4~6
Figure 7A~7B
AI summary
A surgical device (100) includes a first cable portion (102) that engages a first component (116,118) such that a first friction exists between the first cable portion and the first component. The surgical device includes a second cable portion (104) having a first end operatively coupled to a first end of the first cable portion (102). The second cable portion (104) engages a second component (110) such that a second friction exists between the second cable portion and the second component, such that the second friction is greater than the first friction.