Asymmetric Control Element Tension for Flexible Medical Device Torque Balance
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Solution Overview
Problem
Minimally invasive medical devices with articulable portions face challenges in controlling asymmetrical loads due to uneven distribution of components like cable bundles and illumination fibers, leading to torque imbalances at the distal tip, which can result in undesirable contact or force on patient anatomy during procedures.
Innovation Solution
The implementation of a control system that determines a correction factor to compensate for asymmetric conditions by adjusting the tension in control elements, allowing for unequal preloads to maintain net zero torque at the distal tip, and mechanical redesigns such as relocating control elements to counteract asymmetrical loads through increased lever arms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If control elements are positioned symmetrically around the flexible body, then the device structure is simple and easy to manufacture, but asymmetric loads from components like cable bundles and illumination fibers cause torque imbalances at the distal tip
Solution Approach 1:
The patent applies asymmetry by intentionally positioning control elements asymmetrically relative to the flexible body's longitudinal axis. Specifically, control elements are placed at different radial distances from the axis to create unequal lever arms that counterbalance the asymmetric loads generated by components such as cable bundles and illumination fibers. This asymmetric configuration resolves the torque imbalance problem while maintaining manufacturing feasibility.
2Reliability
If control elements are relocated to counteract asymmetric loads, then torque balance is improved, but the device complexity increases due to unequal lever arms and component distribution
Solution Approach 1:
The patent applies local quality by varying the properties of control element positioning along the flexible body's length. Different control elements are positioned at different radial distances from the longitudinal axis depending on their specific function and the local asymmetric loads they need to counteract. This allows each control element to be optimized for its specific location and load conditions, improving overall torque balance while managing device complexity through localized rather than global asymmetry.
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 approach enables precise control and minimization of torque imbalances, ensuring safe and effective navigation and manipulation of medical instruments within patient anatomy by maintaining symmetry and optimizing the distribution of components.
Implementation Method 1
a plurality of control elements, each control element coupling the distal end portion to a corresponding actuator of the plurality of actuators such that the plurality of actuators is operable to apply tension to the plurality of control elements to move the distal end portion
Implementation Method 2
determining a correction factor... The correction factor may provide for maintaining the plurality of tensions at unequal preloads... to maintain net zero torque at the distal tip
Data Source
AI summary
Approaches to addressing asymmetric loads at the distal end of a flexible elongate device are disclosed herein. In some embodiments, symmetry is recovered by mechanically redesigning the flexible elongate device to counter the asymmetric load. In other embodiments, symmetry is recovered by altering the controls scheme for managing the control elements in a flexible elongate device. Generally, a flexible elongate device includes a plurality of control elements able to actuate the distal section. The amount of force applied to each control element can be changed so that the plurality of control elements is able to collectively apply a bending moment that counters the asymmetric load.