Helical Constraint Members for Precise Articulatable 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 constraint members that extend along a helical path between the proximal and distal ends of articulatable members, passively constraining motion without the need for active actuation, thereby reducing the number of actuation members and simplifying the force transmission mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanisms are added to constrain the motion of joints to achieve precise positioning, then positioning accuracy is improved, but device complexity increases
Solution Approach 1:
The constraint member is passively constrained by the helical path geometry itself rather than active actuators. The fixed length and helical configuration automatically enforce the directional constraint on articulation, eliminating the need for additional active constraint mechanisms
Solution Approach 2:
The constraint member follows a helical (curved) path between joints rather than a straight line. This curved geometry inherently guides the articulation motion along the desired trajectory, providing passive constraint through the geometric path itself
2Volume of moving object
If the number of force transmission elements is reduced to decrease instrument size, then instrument size is reduced, but control precision deteriorates
Solution Approach 1:
The single constraint member serves multiple functions simultaneously: it transmits actuation force from the proximal joint to the distal joint, constrains the articulation motion to the helical path, and provides passive stabilization. This multi-functionality eliminates the need for separate constraint mechanisms
Solution Approach 2:
The constraint member is routed through a helical path that adds a dimensional component to the force transmission. This helical routing allows the single member to control articulation in multiple directions while maintaining a compact instrument profile
3Device complexity
If underconstrained structures are used to reduce component count, then device complexity is reduced, but movement controllability deteriorates
Solution Approach 1:
The helical path geometry provides inherent guidance for the constraint member, ensuring that articulation follows the desired trajectory. The curved path acts as a geometric constraint that passively controls movement without requiring additional active control mechanisms
Solution Approach 2:
The constraint member's fixed length and helical routing automatically enforce the articulation constraint. The geometry itself provides the control function, eliminating the need for external control systems or additional actuators
Data Source
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.