Robotic Surgical Inverse Kinematics for Singularity Avoidance
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Solution Overview
Problem
Robotic surgical systems face challenges in controlling tools as they approach or pass through singularities, which can lead to unpredictable tool operation and reduced degrees of freedom.
Innovation Solution
The method involves correcting the pose of the arm and tool by moving the remote center of motion to a boundary distance while maintaining the jaw axis position, and rotating it according to rigid body kinematics, to avoid singularities and maintain degrees of freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tool is allowed to reach a singularity, then the system can maintain continuous operation, but the tool operation becomes unpredictable and degrees of freedom are reduced
Solution Approach 1:
The system applies preliminary anti-action by detecting when the remote center of motion approaches the boundary distance and actively correcting the pose before the singularity is reached. This prevents the harmful effect of unpredictable tool operation and loss of degrees of freedom by counteracting the approach to singularity in advance, rather than allowing it to occur and then recovering.
2Reliability
If hard stops are employed to prevent the tool from reaching a singularity, then predictable operation is maintained, but the device complexity increases
Solution Approach 1:
The patent replaces the mechanical hard stop approach with a computational solution. Instead of physical constraints that would add mechanical complexity, the system uses inverse kinematics calculations and software-based pose correction algorithms to prevent the tool from reaching singularities, thereby maintaining predictable operation without increasing mechanical device complexity.
Solution Approach 2:
The system implements continuous feedback by monitoring the position of the remote center of motion relative to the boundary distance and dynamically adjusting the tool pose when the boundary is approached. This feedback loop enables the system to maintain predictable operation through intelligent control rather than complex mechanical structures.
3Ease of operation
If the remote center of motion is moved to boundary distance to avoid singularity, then degrees of freedom are maintained, but the position of the remote center of motion changes
Solution Approach 1:
The system applies dynamics by making the remote center of motion position adaptive rather than fixed. When the tool approaches a singularity, the boundary distance calculation dynamically adjusts the remote center position to maintain a safe margin, allowing the system to preserve degrees of freedom while managing the trade-off in position accuracy through intelligent, context-dependent adjustments.
Data Source
AI summary
A method of using inverse kinematics to control a robotic system includes receiving an input pose from a user interface to move an arm of the robotic system, calculating a remote center of motion for a desired pose from the input pose in a tool center-point frame, checking when the desire pose needs correction, correcting the desired pose of the arm, and moving the am to the desired pose in response to the input pose. The am of the robotic system including a tool having a jaw disposed at an end of the arm. Checking when the desired pose needs correction includes verifying that the remote center of motion is at or beyond a boundary distance in the desired pose. Correcting the desired pose of the arm occurs when the remote center of motion is within the boundary distance.