Manipulator Arm Null-Space Control for Collision-Limited Motion
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Solution Overview
Problem
Current surgical robotic systems face challenges in limiting unnecessary movement of manipulator arms and achieving desired configurations during minimally invasive procedures, which can lead to collisions and reduced dexterity due to excessive degrees of freedom and mechanical complexity.
Innovation Solution
The system calculates and combines joint movements within the null-space of a manipulator arm's Jacobian to achieve specific objectives, such as collision avoidance and desired end effector motion, using a null-space manager to consolidate multiple objectives and limit movement magnitude while maintaining direction, thereby enhancing the range of motion and reducing unwanted arm movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the manipulator arm uses multiple degrees of freedom to achieve desired configurations, then the range of motion and dexterity are improved, but unnecessary movements and collisions increase
Solution Approach 1:
The patent extracts and separates the null-space movements from the primary task movements by using the null-space of the Jacobian matrix. This allows independent control of manipulator configurations without affecting the end effector position, thereby eliminating unnecessary movements that cause collisions while preserving the full range of motion for task execution.
Solution Approach 2:
The patent changes the control parameters by working in the null-space of the Jacobian matrix rather than directly controlling joint angles. This parameter transformation enables the system to achieve desired manipulator configurations and avoid collisions simultaneously, as the null-space movements do not affect the end effector position but can optimize the arm's configuration.
2Ease of operation
If the manipulator arm uses redundant degrees of freedom to achieve desired configurations, then the dexterity is improved, but the mechanical complexity increases
Solution Approach 1:
The patent substitutes complex mechanical constraint mechanisms with a mathematical approach using the null-space of the Jacobian matrix. Instead of adding mechanical constraints to limit movements, the system uses computational methods to calculate and enforce movement limitations, thereby maintaining dexterity while reducing mechanical complexity.
Solution Approach 2:
The patent transforms the control problem from direct joint space control to null-space control, changing the parameters from joint angles to null-space movement vectors. This parameter change simplifies the control of redundant degrees of freedom by decoupling the primary task from the configuration optimization, reducing the apparent mechanical complexity.
3Object-affected harmful factors
If the system limits the movement magnitude of manipulator arms, then collisions are reduced, but the range of motion is restricted
Solution Approach 1:
The patent segments the movement control into two independent components: primary task movements (in the range space of the Jacobian) and configuration optimizations (in the null-space). This segmentation allows the system to limit movement magnitude for collision avoidance in the null-space while maintaining full range of motion for task execution in the range space.
Solution Approach 2:
The patent moves the collision avoidance control to another dimension by using the null-space of the Jacobian matrix. Instead of limiting movements in the primary task space, the system exploits the additional dimension provided by the null-space to achieve collision avoidance without restricting the essential range of motion needed for surgical tasks.
Data Source
AI summary
A method for moving a manipulator arm. The manipulator arm includes a movable distal portion, a proximal portion coupled to a base, and joints between the distal portion and the base. The method involves calculating a first movement of the joints in accordance with a first objective. The method further involves calculating a second movement of the joints in accordance with a second objective. The first and the second movements are in a null-space of a Jacobian of the manipulator arm. The method also involves determining a combined movement of the joints by combining the first and second movements while limiting an overall magnitude of the combined movement without changing a direction of the combined movement, and/or combining the first and second movements while limiting a magnitude of the combined movement degree-of-freedom by degree-of-freedom. The method further involves driving the joints to effect the combined movement of the joints.