Robotic Manipulator Null-Space Collision Avoidance
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Solution Overview
Problem
Robotic surgical manipulators face challenges in avoiding collisions with the patient's outer surface during minimally invasive procedures, particularly when pivoting over large angular ranges, which can lead to unintended contact with the patient or other surgical components, and existing systems may not adequately address these issues while maintaining dexterity and range of motion.
Innovation Solution
The implementation of highly configurable robotic manipulators with redundant degrees of freedom, allowing movement within a null-space to avoid collisions by calculating and driving joint movements within the null-space of the kinematic Jacobian, thereby maintaining the desired end effector state and remote center location, while also enabling increased range of motion without significant mechanical complexity or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If robotic manipulators pivot over large angular ranges to increase range of motion, then surgical accessibility is improved, but collision risk with patient surface increases
Solution Approach 1:
The patent introduces a null-space dimension for manipulator motion that is independent of the traditional task space. By utilizing redundant degrees of freedom, the system can move manipulators along null-space trajectories that avoid collisions with the patient surface while maintaining the same end effector position and orientation. This adds an extra dimension of freedom to the control problem, allowing collision avoidance without sacrificing range of motion.
Solution Approach 2:
The system dynamically changes the configuration parameters of the manipulator by adjusting joint angles within the null-space. By modifying the internal configuration parameters (joint angles) while keeping the end effector pose parameters constant, the system can alter the manipulator's physical path to avoid collisions while maintaining the same surgical task performance.
2Reliability
If redundant degrees of freedom are added to avoid collisions, then collision avoidance capability is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical collision avoidance mechanisms with a computational approach. Instead of adding physical constraints or mechanical stops to prevent collisions, the system uses software-based null-space calculations to dynamically adjust manipulator trajectories. This substitutes mechanical complexity with computational complexity, achieving collision avoidance through control algorithms rather than mechanical design.
Solution Approach 2:
The redundant degrees of freedom serve multiple functions: they enable collision avoidance, improve manipulator dexterity, and maintain end effector positioning accuracy. The same null-space mechanism that prevents collisions also allows for optimized motion paths and improved accessibility, making the added complexity serve multiple beneficial purposes rather than a single function.
3Reliability
If manipulator configuration is adjusted to avoid collisions, then safety is improved, but end effector precision may deteriorate
Solution Approach 1:
The patent extracts the collision avoidance function from the end effector positioning function by separating them into different control spaces. The task space controls end effector position and orientation with high precision, while the null-space handles collision avoidance independently. This separation ensures that safety adjustments in the null-space do not interfere with positioning precision in the task space.
Solution Approach 2:
The system continuously monitors manipulator configuration and patient surface proximity, using feedback to dynamically adjust null-space trajectories. When collision risk is detected, the feedback loop triggers null-space motion adjustments that maintain safe distances while preserving end effector positioning accuracy through continuous coordination between task space and null-space controllers.
Data Source
AI summary
Devices, systems, and methods for avoiding collisions between a manipulator arm and an outer patient surface by moving the manipulator within a null-space. In response to a determination that distance between an avoidance geometry and obstacle surface, corresponding to a manipulator-to-patient distance is less than desired, the system calculates movement of one or more joints or links of the manipulator within a null-space of the Jacobian to increase this distance. The joints are driven according to the reconfiguration command and calculated movement so as to maintain a desired state of the end effector. In one aspect, the joints are also driven according to a calculated end effector displacing movement within a null-perpendicular-space of the Jacobian to effect a desired movement of the end effector or remote center while concurrently avoiding arm-to-patient collisions by moving the joints within the null-space.