Five-Bar Spherical Linkage for Robotic Arm Precision
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Solution Overview
Problem
Traditional minimally invasive surgery requires high surgical skill due to the need for unnatural hand motions to control surgical instruments at a distance from the surgeon's hands, making it challenging to perform precise movements during robotic-assisted procedures.
Innovation Solution
The use of a parallel spherical five-bar linkage in robotic arms that supports surgical instruments, allowing the tool shaft to pivot about a remote center of spherical rotation, enabling precise and intuitive motion control by constraining the insertion axis to rotate about a center positioned in space along the cannula, thus reducing the need for unnatural hand movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional minimally invasive surgery is performed with direct manual control of surgical instruments, then the surgeon can directly manipulate the instruments, but the surgeon must perform unnatural hand motions to control instruments at a distance from the surgical site
Solution Approach 1:
A robotic arm system acts as an intermediary between the surgeon's natural hand motions and the surgical instrument at the distal site. The robotic arm includes a five-bar spherical linkage mechanism with multiple articulated segments that translate proximal actuator motions into distal instrument movements, eliminating the need for the surgeon to perform unnatural hand motions while maintaining direct control.
Solution Approach 2:
The robotic arm employs dynamic motion transformation through its five-bar spherical linkage, where the mechanism adapts its kinematic properties based on the position and orientation of the surgical instrument. The linkage dynamically adjusts the relationship between proximal actuator movements and distal instrument movements, providing intuitive control throughout the range of motion.
2Measurement precision
If the surgical instrument is positioned at a remote site through a long tool shaft, then the surgeon can access deep internal surgical sites, but the precision and accuracy of instrument manipulation deteriorates due to the distance from the surgeon's hands
Solution Approach 1:
The tool shaft is segmented into multiple articulated robotic arm segments connected by spherical joints. This segmentation allows each segment to be independently actuated and controlled, with the proximal segments providing stable support and the distal segments enabling precise instrument positioning. The five-bar spherical linkage provides redundant actuation paths that enhance positioning precision despite the long reach.
Solution Approach 2:
The robotic arm system incorporates compliance and damping elements in the linkage mechanism to cushion vibrations and positional uncertainties that would otherwise be amplified over the long tool shaft length. The five-bar linkage provides mechanical filtering of high-frequency vibrations, maintaining precision at the distal instrument tip.
3Reliability
If a five-bar spherical linkage is used in the robotic arm, then the insertion axis can be constrained to rotate about a remote center of spherical rotation, but the device complexity increases
Solution Approach 1:
The five-bar linkage is configured as a spherical mechanism where all rotation axes intersect at a common remote center point. This spherical geometry inherently constrains the insertion axis to rotate about the remote center of spherical rotation, providing stable and predictable motion constraints. The spherical joint design maintains constant distance relationships that enforce the rotational constraint while accommodating the full range of motion.
Data Source
AI summary
A robotic arm for a minimally invasive surgical system includes a parallel spherical five-bar linkage adapted to spherically rotationally move a robotic surgical tool coupled to the parallel five-bar spherical linkage about a remote center of spherical rotation. The five-bar spherical linkage is posed in only a range of compact poses. A constraint limits the parallel five-bar spherical linkage to only the range of compact poses.