Tendon-Driven Surgical Joint Design for Low-Friction Miniaturization
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Solution Overview
Problem
Existing robotic surgical assemblies face challenges in miniaturization, kinematic accuracy, and control complexity, particularly in microsurgery, due to friction, mechanical constraints, and cumbersome joint mechanisms, which hinder precise instrument movement and require extensive training.
Innovation Solution
A tendon-driven jointed medical instrument with convex contact surfaces and parallel tendons minimizes friction and encumbrance, allowing for precise, intuitive control and versatile surgical procedures, featuring a simplified manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional multi-joint robotic arms with serial kinematic chains are used, then the surgical instrument can reach the operating field through surgical ports, but the coordination of multiple degrees of freedom creates encumbrance in the operating work-field and makes kinematic accuracy control difficult
Solution Approach 1:
The robotic system is divided into two independent functional modules: a macro-positioning arm for coarse positioning and a micro-positioning device for fine adjustments. This segmentation allows each module to specialize in its function, reducing the complexity of coordinating multiple degrees of freedom while maintaining access to the operating field.
Solution Approach 2:
The micro-positioning device acts as an intermediary between the macro-positioning arm and the surgical instrument. It receives the instrument from the macro arm and provides the fine positional adjustments needed for precise surgical operations, thereby simplifying the overall control architecture.
2Adaptability or versatility
If joints are positioned further away from the instrument tip to enable reorientation, then the instrument can be oriented in a large spatial cone of directions, but the encumbrance in the operating field increases
Solution Approach 1:
The micro-positioning device is designed to be mounted on or integrated with the macro-positioning arm, creating a nested configuration. This allows the orientation mechanisms to be positioned away from the instrument tip while keeping the overall structure compact and minimizing encumbrance in the operating field.
3Ease of manufacture
If conventional tendon routing with grooves and channels is used, then the tendons can be guided through the instrument, but friction increases and miniaturization becomes difficult
Solution Approach 1:
The tendon routing system extracts the harmful friction-causing elements (grooves and channels) and replaces them with a smooth-bore tube configuration. The tendons pass through simple cylindrical openings without contact with guiding surfaces, eliminating friction while maintaining ease of manufacture.
4Adaptability or versatility
If robotic assemblies with multiple independent movements are used, then the instrument can perform complex surgical maneuvers, but the control of kinematic accuracy becomes difficult
Solution Approach 1:
The system transitions from a static, fully coordinated multi-joint mechanism to a dynamic, two-stage positioning system. The macro arm provides coarse positioning with fewer coordination requirements, while the micro-positioning device dynamically adjusts the instrument position with high precision, thereby improving kinematic accuracy control.
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 solution enables extreme miniaturization, improved kinematic control, and reduced training time for surgeons, ensuring high precision and reliability in various surgical procedures while maintaining sterility and durability.
Implementation Method 1
at least one tendon (90), suitable to move said joint member (72) with respect to said frame (57)
Data Source
AI summary
A medical instrument for surgery includes at least one frame and at least one jointed device. The jointed device includes at least one first joint member, or first link, adapted to connect to at least one portion of the frame and at least one second joint member, or second link. The first joint member is connected by a rotational joint to the second joint member. The medical instrument includes at least a pair of tendons, adapted to move the second joint member with respect to the first joint member. Each of the first joint member and the second joint member includes a main structural body made in a single piece with one or more convex contact surfaces. Each of the convex contact surfaces is a ruled surface formed by straight line portions all parallel to each other and substantially parallel to a joint movement axis.