Manipulator Null-Space Control for Collision-Aware Joint Reconfiguration
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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, especially when performing tasks that require a wide range of motion within a limited space.
Innovation Solution
The development of a tele-operation system with highly configurable robotic manipulators that incorporate redundant degrees of freedom and a null-space manager system to manage multiple objectives, allowing for coordinated joint movements and avoiding collisions by calculating joint velocities within the null-perpendicular-space of the Jacobian, enabling efficient and precise manipulation of surgical instruments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If redundant degrees of freedom are added to manipulator arms to increase range of motion and dexterity, then the ability to perform complex surgical tasks is improved, but the complexity of the control system and mechanical structure increases
Solution Approach 1:
The control system is segmented into multiple independent objective functions, each handling a specific task (e.g., collision avoidance, singularity avoidance, dexterity optimization). The null-space manager divides the redundant degree of freedom control into separate manageable objectives that can be processed independently and combined, reducing overall control complexity while maintaining full range of motion capability.
Solution Approach 2:
The system transitions from controlling only the essential motion dimensions to utilizing the null-space dimension provided by redundant degrees of freedom. By calculating joint velocities within the null-perpendicular-space of the Jacobian, the system exploits the additional dimensional space created by redundant joints to achieve multiple objectives simultaneously without increasing the physical structure complexity.
2Manufacturing precision
If manipulator arms are configured to achieve precise end effector positioning, then surgical precision is improved, but unnecessary arm movement occurs that can lead to collisions
Solution Approach 1:
The system performs preliminary collision avoidance actions by calculating desired joint movements that proactively steer manipulator arms away from potential collision zones before collisions occur. The null-space objective functions preemptively adjust joint configurations to maintain safe distances from obstacles while still achieving the required end effector positioning precision.
Solution Approach 2:
The null-space manager acts as an intermediary between the end effector positioning commands and the actual joint actuation. It processes the positioning requirement and translates it into joint velocity commands that incorporate collision avoidance constraints, mediating between precision positioning and safety requirements without compromising either objective.
3Productivity
If multiple null-space objectives are managed simultaneously to achieve collision avoidance and dexterity optimization, then overall system performance is improved, but the computational complexity increases
Solution Approach 1:
Multiple null-space objectives are segmented into separate objective functions, each responsible for a specific aspect (collision avoidance, singularity avoidance, dexterity). This segmentation allows each objective to be calculated and optimized independently, reducing the computational burden compared to optimizing all objectives simultaneously in a single complex calculation.
Solution Approach 2:
After segmenting and independently processing multiple null-space objectives, the system merges the resulting joint velocity commands into a unified control signal. The null-space manager combines the individual objective outcomes through vector addition or weighted summation, achieving integrated multi-objective optimization with computational efficiency that scales better than exhaustive simultaneous optimization methods.
Data Source
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Figure 1B
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AI summary
Devices, systems, and methods for providing commanded movement of an end effector of a manipulator concurrent with a desired movement of one or more joints of the manipulator according to one or more consolidated null-space objectives. The null-space objectives may include a joint state combination, relative joint states, range of joint states, joint state profile, kinetic energy, clutching movements, collision avoidance movements, singularity avoidance movements, pose or pitch preference, desired manipulator configurations, commanded reconfiguration of the manipulator, and anisotropic emphasis of the joints. Methods include calculating multiple null-space movements according to different null-space objectives, determining an attribute for each and consolidating the null-space movements with a null-space manager using various approaches. The approaches may include applying weighting, scaling, saturation levels, priority, master velocity limiting, saturated limited integration and various combinations thereof.