Surgical Robot Arm Null-Space Control for Collision Priorities
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Solution Overview
Problem
Current surgical robotic systems face challenges in minimizing unnecessary movement of manipulator arms outside the patient and maintaining dexterity, especially when performing minimally invasive surgeries, due to the complexity and redundancy of joints, which can lead to collisions and inefficient motion.
Innovation Solution
The implementation of a medical system with a manipulator arm that includes a processor configured to calculate movements in the null-space of a Jacobian to prioritize arm-to-patient and arm-to-arm collision avoidance, allowing for combined movements that optimize collision avoidance while maintaining dexterity and range of motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the manipulator arm uses multiple joints with redundant degrees of freedom to increase dexterity and range of motion, then the ability to perform intricate surgical tasks is improved, but unnecessary movement outside the patient and collision risk increase
Solution Approach 1:
The control of manipulator joints is segmented into two independent components: primary movements that achieve the desired distal portion position, and null-space movements that optimize collision avoidance. This segmentation allows independent optimization of each control aspect without interfering with the other.
Solution Approach 2:
The invention introduces null-space movement, an additional dimension in the control space that is independent of the primary position control. This extra degree of freedom in the control algorithm allows the system to optimize collision avoidance without compromising the accuracy of distal portion positioning.
2Adaptability or versatility
If the manipulator arm uses multiple joints with redundant degrees of freedom to increase range of motion within the patient, then the ability to access difficult surgical sites is improved, but unnecessary movement outside the patient increases
Solution Approach 1:
The system pre-calculates null-space movements that will minimize unnecessary motion of proximal joints before executing the primary movement command. This preliminary optimization ensures that the manipulator arm takes the most efficient path through its range of motion.
Solution Approach 2:
The invention replaces mechanical constraints with computational optimization. Instead of using physical limiters or mechanical guides to prevent unnecessary movement, the system uses software-based null-space optimization to achieve the same effect, maintaining full mechanical range of motion while eliminating wasteful movements.
3Reliability
If the system prioritizes collision avoidance through null-space calculation, then safety is improved, but the complexity of the control system increases
Solution Approach 1:
The null-space calculation acts as an intermediary layer between the surgeon's input commands and the actual joint movements. This intermediate computational step translates simple position commands into optimized joint trajectories that automatically account for collision avoidance, encapsulating the complexity within a unified control framework.
Solution Approach 2:
The null-space optimization framework serves multiple functions simultaneously: it minimizes unnecessary movement, reduces collision risk, and maintains dexterity. This multi-functionality is achieved through a single unified mathematical approach that handles all these objectives through the same computational mechanism.
Data Source
AI summary
A medical system includes a manipulator arm including a movable distal portion, a proximal portion coupled to a base, and joints between the distal portion and the base. A processor coupled to the manipulator arm performs operations including calculating a first movement of the joints in a null-space of a Jacobian of the manipulator arm, the first movement being calculated in accordance with a first objective for arm-to-patient collision avoidance. The operations further include calculating a second movement of the joints in the null-space, the second movement being calculated in accordance with a second objective for arm-to-arm collision avoidance, and combining at least the first and second movements into a combined movement in a manner allowing the first objective to overpower the second objective, and driving the joints to effect the combined movement.