Single-Input Capstan Assembly for Multi-Cable Wrist Retroflex
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Solution Overview
Problem
Existing minimally invasive surgical instruments face challenges in efficiently incorporating additional cables for wrist mechanism motion, particularly retroflex motion, due to space and design constraints, leading to increased complexity and cost.
Innovation Solution
A medical instrument design that utilizes a capstan assembly with different radius cable drums to move multiple cables at varying speeds and directions via a single rotary input, reducing the need for additional space and drive inputs, and incorporating mechanisms for improved control of wrist mechanism motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple capstans are used to drive multiple cables for wrist mechanism motion, then the wrist mechanism can achieve full range of motion including retroflex motion, but the mechanical structure complexity and size increase
Solution Approach 1:
The patent combines multiple capstan functions into a single capstan assembly that can drive multiple cables simultaneously. The single capstan assembly integrates the functions of multiple separate capstans, reducing mechanical structure complexity while maintaining the ability to control wrist mechanism motion in multiple degrees of freedom including retroflex motion.
Solution Approach 2:
The single capstan assembly is designed to perform multiple functions that would traditionally require separate capstans. It can drive different cables with different radii to achieve various wrist motions (pitch, yaw, retroflex) from a single input mechanism, making the mechanical structure more versatile and less complex.
2Ease of operation
If additional cables are added to enable retroflex motion and enhanced wrist control, then the wrist mechanism achieves improved motion control, but the instrument size and space requirements increase
Solution Approach 1:
Multiple cable drive functions are merged into a single capstan assembly, reducing the overall space required in the instrument. By combining what would traditionally be separate capstan-cable assemblies into one integrated unit, the instrument size is minimized while still supporting multiple cables for enhanced wrist control and retroflex motion.
Solution Approach 2:
The patent utilizes different radii for the cable drum to achieve varying cable movement distances from a single rotational input. This dimensional variation in the cable drum radius allows different cables to be actuated at different speeds and distances, enabling complex wrist motions including retroflex without requiring additional spatial complexity.
3Device complexity
If a single capstan drives multiple cables with different radii, then the mechanical structure size is reduced, but the cable movement speeds and directions must be precisely controlled
Solution Approach 1:
The patent changes the parameter of cable drum radius to control cable movement characteristics. By using cable drums with different radii on the single capstan assembly, the system achieves precise control over cable movement speeds and directions. The radius parameter serves as a simple yet effective means of controlling the kinematic behavior of each cable without adding complex control mechanisms.
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 design allows for reduced mechanical structure complexity, cost, and size, while providing enhanced control over wrist mechanism movements, including retroflex motion, thus facilitating more efficient minimally invasive surgical procedures.
Implementation Method 1
the proximal end portion of the first cable is wrapped about the first cable drum and the proximal end portion of the second cable is wrapped about the second cable drum
Data Source
AI summary
A medical instrument includes a shaft, a wrist, a mechanical structure, a first cable, and a second cable. The wrist is coupled to the distal end portion of the shaft. The mechanical structure is coupled to a proximal end portion of the shaft and includes a capstan assembly. The capstan assembly includes a first cable drum having a first radius and a second cable drum having a second, different radius. The first cable is routed along the shaft. A distal end portion of the first cable is coupled to the wrist and a proximal end portion of the first cable is wrapped about the first cable drum. The second cable is routed along the shaft. A distal end portion of the second cable is coupled to the wrist and a proximal end portion of the second cable is wrapped about the second cable drum.