Surgical Tool Shaft Decoupling for Accurate Clinical Force Feedback
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Solution Overview
Problem
In teleoperated surgical systems, the forces imparted by control cables within the shaft are significantly larger than the clinical forces from contact between the end effector and patient tissue, necessitating a method to isolate clinical forces from cable forces.
Innovation Solution
A four-bar linkage mechanism is employed to decouple vertical clinical forces from lateral cable actuation forces, using a flexure beam and pulley system to maintain cable alignment parallel to the side links, isolating clinical forces perpendicular to the shaft axis from larger cable forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If control cables are used to actuate the end effector in teleoperated surgery, then the end effector can be precisely controlled, but the large cable forces interfere with and mask the small clinical forces from tissue contact
Solution Approach 1:
The system segments the force transmission paths by separating cable forces from clinical forces through a four-bar linkage mechanism. The linkage divides the force transmission into distinct pathways: cable forces act on the linkage mechanism while clinical forces are transmitted separately to the sensor, preventing interference between the two force types.
Solution Approach 2:
The four-bar linkage acts as an intermediary mechanism between the cable drive system and the end effector. It mediates the interaction between large cable forces and small clinical forces, allowing precise control while maintaining accurate force feedback through the sensor that measures only clinical forces.
2Ease of operation
If a long shaft is used to transmit surgeon's tactile cues in manual surgery, then the surgeon can feel tissue interaction forces, but the shaft length eliminates tactile cues and masks force cues
Solution Approach 1:
The system replaces the direct mechanical connection of manual surgery with a teleoperated system that uses a sensor to measure clinical forces and provides feedback to the surgeon. The four-bar linkage mechanism substitutes for the direct shaft transmission, allowing force measurement without requiring the surgeon to feel forces through a long shaft.
3Adaptability or versatility
If control cables extend within the shaft to actuate the end effector, then remote actuation is achieved, but cable forces are significantly larger than clinical forces requiring isolation
Solution Approach 1:
The four-bar linkage mechanism segments the force transmission paths, creating separate pathways for cable forces and clinical forces. This segmentation allows remote actuation through cables while isolating the sensor from cable forces, maintaining adaptability without excessive complexity.
Solution Approach 2:
The four-bar linkage mechanism serves multiple functions: it transmits cable forces to actuate the end effector, maintains cable alignment parallel to the shaft axis, and isolates clinical forces from cable forces. This multi-functionality reduces overall system complexity while achieving remote actuation and force isolation.
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 effectively isolates clinical forces from cable forces, ensuring accurate force feedback to the surgeon and reducing interference, thereby enhancing the precision and safety of teleoperated surgical procedures.
Implementation Method 1
A four-bar linkage mechanism is employed to decouple vertical clinical forces from lateral cable actuation forces, using a flexure beam and pulley system to maintain cable alignment parallel to the side links
Implementation Method 2
A four-bar linkage mechanism is employed to decouple vertical clinical forces from lateral cable actuation forces, using a flexure beam and pulley system
Data Source
AI summary
A surgical tool is provided that includes a hollow shaft and a cable extending within the shaft such that the cable is isolated from external forces imparted to the shaft; the shaft and a carriage are included as links of a 4-bar linkage that also includes first and second side links that are rotatably mounted to the carriage at respective first and second distal pivot axes and that are rotatably mounted to the shaft at respective first and second proximal pivot axes; the segment of the cable extends between a distal pulley rotatably at the carriage and a proximal pulley rotatably mounted at the shaft and a segment of the cable extends within the shaft; a distance between the first distal and first proximal pivot axes matches a distance between an axis of the distal pulley axis and an axis of the proximal pulley such that a rocking motion of the 4-bar linkage due to external force upon the shaft exerts no force upon the cable.