Articulatable Member with Helical Constraint for Predictable Motion
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Solution Overview
Problem
Existing minimally invasive surgical instruments face challenges in controlling the movement and positioning of articulatable members due to underconstrained jointed link structures, leading to unpredictable and uncontrollable movement, increased mechanical complexity, and difficulty in manufacturing.
Innovation Solution
The use of passive constraint members, such as constraint tendons following a helical path along the articulatable member, which are fixed at opposite ends and do not require actuation, to constrain the motion of the articulatable member, thereby reducing mechanical complexity and conserving space within the instrument.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive constraint members following a helical path are used to constrain motion, then device complexity is reduced and manufacturing becomes easier, but control precision over articulatable member movement may be compromised
Solution Approach 1:
The constraint member follows a helical (curved) path along the articulatable member instead of a straight linear path. This curved configuration allows the single constraint member to effectively constrain motion across multiple joints while maintaining mechanical simplicity and reducing the number of components required.
Solution Approach 2:
The single constraint member serves multiple functions by constraining motion across multiple joints along its helical path. This multi-functional approach replaces what would traditionally require multiple separate constraint members or complex actuation systems for each joint, thereby reducing overall device complexity while maintaining control precision.
2Volume of moving object
If fewer force transmission elements are used to reduce overall instrument size, then the instrument can fit within narrow lumens, but the articulatable member becomes underconstrained leading to unpredictable movement
Solution Approach 1:
The helical path of the constraint member allows it to efficiently span multiple joints within a compact volume. The curved geometry enables the constraint member to maintain effective leverage and control authority across all joints it passes through, ensuring predictable movement despite the reduced number of force transmission elements.
Solution Approach 2:
The constraint member transitions from a traditional linear arrangement to a three-dimensional helical path along the articulatable member. This dimensional change allows a single force transmission element to effectively control multiple joints that would otherwise require separate actuators, maintaining movement predictability while reducing overall instrument size.
3Measurement precision
If constraint members are actively actuated to control movement, then positioning precision is improved, but mechanical complexity and operational difficulty increase
Solution Approach 1:
The constraint member operates passively without requiring active actuation or external control systems. The helical geometry of the constraint member automatically converts the actuation force applied at one end into coordinated motion across multiple joints, eliminating the need for complex control mechanisms while maintaining positioning precision.
Solution Approach 2:
The helical constraint member acts as an intermediary mechanical element that translates a single actuation input into coordinated motion across multiple joints. This passive intermediary mechanism simplifies the overall system by eliminating the need for active sensors, controllers, and multiple actuators while maintaining precise positioning capability.
Data Source
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AI summary
An articulatable member includes a distal end, a proximal end, an actuation member, and a constraint member. The actuation member extends from the proximal end to the distal end. The actuation member transmits force to bend the articulatable member from a neutral position. The constraint member extends from the proximal end to the distal end. The constraint member may have opposite ends that are fixed to the distal end and the proximal end. In one embodiment, the constraint member follows a helical path along at least a portion of the articulatable member from the proximal end to the distal end. In another embodiment, the actuation member follows a helical path along at least a portion of the articulatable member.