Remote Centre of Motion Mechanism for Surgical Tool Mounting
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Solution Overview
Problem
Remote centre of motion manipulators face challenges such as limited tool mounting space, potential patient injury due to proximity of motion components, and bulkiness, which complicates minimally invasive surgical procedures and collaboration with other devices.
Innovation Solution
The design incorporates a base link with a local centre of motion, a proximal link connected via a revolute and sliding joint, and a distal link with an inclined orientation to increase tool mounting space, a connecting link to further expand space, and a second motion mechanism to reduce bulkiness and prevent protruding linkages from causing injury or collision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the tool is mounted in proximity of the distal link to be coaxial with the remote centre of motion, then the tool mounting space is limited, but custom-made tools must be developed to cope with the space requirements
Solution Approach 1:
The distal link is oriented at an angle between 1° and 89° relative to the tool axis, creating a spatial arrangement that diverges the tool axis from the distal link in a direction away from the remote centre of motion. This angular orientation in a different dimensional direction increases the available mounting space without requiring custom tool development
2Object-affected harmful factors
If the distance between the local centre of motion and the remote centre of motion is increased to prevent patient injury, then the system stiffness is degraded leading to heavier linkages and manipulators
Solution Approach 1:
The motion mechanism is divided into a proximal link moving about a local centre of motion and a distal link moving about a remote centre of motion, connected through intermediate links. This segmentation allows the local centre to be positioned closer to the patient for safety while the distal link maintains system stiffness through its orientation and connection geometry
Solution Approach 2:
Intermediate links connect the proximal and distal links, acting as mediators that transmit motion while allowing the local and remote centres of motion to be positioned at appropriate distances. This intermediary structure enables patient safety without compromising system stiffness
3Volume of stationary object
If the manipulator system is made more compact to avoid collisions with other manipulators, then the space for tool mounting and surgeon access is reduced
Solution Approach 1:
The distal link is oriented at an angle relative to the tool axis, utilizing angular dimension to increase tool mounting space without increasing the overall footprint volume. This angular orientation allows tools to be mounted in a direction away from the remote centre of motion, providing adequate mounting area while maintaining a compact manipulator configuration
Data Source
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AI summary
Apparatus for generating motion around a remote centre of motion is described. The apparatus comprises a base link comprising a local centre of motion, a first motion mechanism comprising a proximal link, a distal link and a first intermediate link pivotally interconnecting the proximal link and the distal link. The proximal link is coupled to the local centre of motion through a revolute joint and a sliding joint allowing the proximal link to translate relative to the local centre of motion and to rotate about the local centre of motion, and the first motion mechanism is configured to copy motion of the proximal link relative to the local centre of motion to an identical motion of the distal link relative to the remote centre of motion. The apparatus further comprises a tool holder fixed to the distal link. The tool holder defines a tool axis intersecting the remote centre of motion. The apparatus is characterised in that the distal link defines a first orientation which is inclined relative to the tool axis.