Remote Center of Motion Robotic Linkage Design
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Solution Overview
Problem
Current robotic manipulators for minimal invasive surgery (MIS) face challenges with limited access and precision due to the constraints of small incisions, leading to reduced degrees of freedom and stability of the remote center of motion (RCM), which complicates accurate instrument positioning and safety, especially with the need for compact and sterilizable designs.
Innovation Solution
A robotic apparatus with a distal link, proximal link, and base link that revolves and translates around a remote center of motion, utilizing a single parallelogram mechanism connected by a single bar for end-effector actuation, allowing for improved stability and precision in instrument positioning with reduced space occupancy and enhanced safety features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional RCM mechanisms with multiple linkages and parallelograms are used to achieve mechanical RCM, then positioning precision is improved, but device complexity and space occupancy increase
Solution Approach 1:
The mechanism is divided into distinct functional modules: a base link with mounting fixture, a proximal link with two-degree-of-freedom joint, and a distal link with the instrument. This segmentation allows each module to be optimized independently while maintaining overall RCM functionality, reducing the complexity of the entire system.
Solution Approach 2:
The invention extracts and eliminates redundant linkages and parallelograms from traditional RCM mechanisms. By using a single proximal link connected to a single distal link through a two-degree-of-freedom joint, the mechanism achieves RCM with fewer components, directly reducing device complexity while maintaining positioning precision.
2Adaptability or versatility
If translation stages and additional rotation stages are mounted at the end-effector to provide linear translation and rotation, then degrees of freedom are improved, but space occupancy and mass increase
Solution Approach 1:
The invention merges the translation and rotation functions into a single integrated two-degree-of-freedom joint. This joint simultaneously provides both the linear translation along the instrument axis and the rotation about the instrument axis, eliminating the need for separate translation stages and rotation stages, thereby reducing space occupancy at the end-effector.
Solution Approach 2:
The two-degree-of-freedom joint serves multiple functions: it acts as both the translation mechanism and the rotation mechanism, and also serves as the mounting point for the instrument. This multi-functionality reduces the number of components needed at the end-effector, decreasing space occupancy while maintaining full degrees of freedom.
3Manufacturing precision
If telescopic arms and parallelograms are used to provide translational degree of freedom, then positioning capability is improved, but mass and dynamic range are reduced
Solution Approach 1:
The invention extracts and removes the heavy telescopic arms and parallelogram mechanisms from the system. Instead, it uses a lightweight proximal link that translates and rotates about the proximal center of motion, significantly reducing the mass at the end-effector while maintaining positioning capability through the two-degree-of-freedom joint.
Solution Approach 2:
Instead of providing translation through telescopic arms that extend and retract, the invention inverts the approach by having the proximal link translate through the proximal center of motion in the opposite direction. This inversion allows for a more compact, lighter design that maintains the same positioning capability.
4Measurement precision
If actuators are placed in close vicinity to the patient to provide local actuation, then control precision is improved, but safety and sterilisability are compromised
Solution Approach 1:
The invention introduces the two-degree-of-freedom joint as an intermediary mechanism between the actuators and the instrument. The actuators can be positioned remotely, and the two-degree-of-freedom joint translates their motion into precise local actuation at the instrument, maintaining control precision while improving safety by keeping actuators away from the patient.
Solution Approach 2:
The invention extracts the actuators from the immediate vicinity of the patient and positions them remotely. The two-degree-of-freedom joint and linkage system transmit the actuator motion to the instrument with sufficient precision, thereby improving safety and sterilisability while maintaining control precision.
Data Source
AI summary
Apparatus (10) for generating motion around a remote center of motion (RCM), comprising a distal link (L12) arranged to revolve about the remote center of motion and to translate through the remote center of motion, a proximal link (L10) arranged to revolve about a proximal center of motion (LCM), coupled to a base link (L1), through a rotational joint (150) and a sliding joint (181), a first mechanism comprising a first link (L9) pivotally coupled to the proximal link (L10) and to the distal link (L12) and operable to transfer motion of the proximal link relative to the proximal center of motion to a motion of the distal link relative to the remote center of motion by maintaining a parallelogram (PAR1), and a second mechanism operable to move the first link with two degrees of freedom in a plane parallel to the plane of motion of the proximal link, characterized in that the second mechanism comprises one link or a serial connection of links (L4, L8, L3, L7, L2, L6) connecting the base link to the first link, configured to have an orientation of instant motion which is different from an orientation of instant motion of the proximal link (L10), relative to the base link.