Instrument Insertion Transmission Assembly with Geared Capstans
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Solution Overview
Problem
Existing transmission assemblies for remotely-controlled instruments with relative translation between the instrument shaft and transmission assembly result in complex architectures, making it challenging to provide compact, efficient drive forces for insertion degree of freedom while supporting other functionalities, and are prone to slack and interference issues.
Innovation Solution
The use of a transmission assembly with a pushable actuation element coupled to a movable component, a first set of pullable actuation elements, and a configuration of capstans and pulleys that allow the pushable actuation element to translate relative to the instrument shaft while maintaining stability, along with geared capstans to provide mechanical advantage for large driving forces and long distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a transmission assembly with relative translation between instrument shaft and transmission assembly is used, then insertion degree of freedom is achieved, but device complexity increases
Solution Approach 1:
The pushable actuation element is nested within the instrument shaft, allowing it to translate along the longitudinal axis while remaining contained within the overall instrument structure. This nesting approach enables the insertion degree of freedom without requiring the entire transmission assembly to move externally, thereby reducing architectural complexity.
Solution Approach 2:
The transmission assembly is segmented into distinct functional components: the pushable actuation element for insertion motion, the movable component for additional degrees of freedom, and the fixed transmission mechanisms. This segmentation allows each component to perform its specific function independently, simplifying the overall architecture compared to a monolithic moving transmission assembly.
2Force
If geared capstans are used to provide mechanical advantage, then large driving forces and long distances are achieved, but device complexity increases
Solution Approach 1:
Geared capstans serve as intermediary mechanisms between the actuation elements and the movable component. These capstans provide the necessary mechanical advantage to amplify driving forces and extend actuation distances without requiring direct coupling between the actuation elements and the load, thereby managing complexity through functional intermediation.
Solution Approach 2:
The geared capstans change the parameters of force and distance by providing mechanical advantage. The gear mechanism transforms small input forces over long distances into large output forces over shorter distances, allowing the system to achieve both large driving forces and long actuation distances while keeping the transmission assembly size manageable.
3Adaptability or versatility
If multiple actuation elements are used to drive movable component, then functionality is enhanced, but slack and interference issues occur
Solution Approach 1:
Instead of allowing the actuation elements to pull the movable component directly (which creates slack), the system uses pushable actuation elements that push the movable component. This inversion of the actuation mechanism eliminates slack issues because push elements maintain continuous contact and force transmission without the looseness that occurs with pull-based cable systems.
Solution Approach 2:
The problematic slack-prone pullable actuation elements are extracted from the system and replaced with pushable actuation elements. This extraction removes the source of slack and interference problems while retaining the ability to drive the movable component, thereby enhancing reliability without sacrificing functionality.
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
This configuration enables a compact, efficient transmission assembly that supplies large driving forces and long distances to pushable actuation elements, reduces slack, and prevents interference, enhancing the functionality of instruments with relative translation.
Implementation Method 1
a configuration of capstans and pulleys that allow the pushable actuation element to translate relative to the instrument shaft
Implementation Method 2
a configuration of capstans and pulleys that allow the pushable actuation element to translate relative to the instrument shaft
Implementation Method 3
geared capstans to provide mechanical advantage for large driving forces and long distances
Data Source
AI summary
A medical instrument comprises an instrument shaft, a movable component coupled to the instrument shaft, a pushable actuation element coupled to the moveable component and translatable relative to the instrument shaft, a first set of pullable actuation elements coupled to the instrument shaft, a second set of pullable actuation elements coupled to the pushable actuation element, and a transmission assembly movably coupled to the instrument shaft. Translation of the pushable actuation element drives a degree of freedom of motion of the movable component. The transmission assembly comprises a first rotatable drive member configured to actuate the first set of pullable actuation elements to drive translation of the instrument shaft relative to the transmission assembly, and one or more capstans configured to actuate the second set of pullable actuation elements to drive translation of the pushable actuation element relative to the instrument shaft.