Bone-Cutting Robot Tool Paths Based on Local Density Feedback
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Solution Overview
Problem
Robotic systems for removing material from workpieces, particularly non-homogeneous materials like bone, face inefficiencies due to constant feed rates and tool paths, which can lead to inaccurate cuts and increased operating times, as these methods do not account for varying density distributions within the workpiece.
Innovation Solution
A surgical robotic system with a manipulator and controllers that generate and adjust tool paths based on real-time interaction with the bone, using density values to optimize feed rates and tool paths for precise material removal, allowing for adaptive control of the surgical tool's movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a constant feed rate is used for material removal, then the system is simple to operate, but cutting accuracy deteriorates when encountering varying density materials like bone
Solution Approach 1:
The system dynamically adjusts the feed rate based on real-time sensing of bone density and tool interaction forces. The controller modifies the feed rate parameter on-the-fly rather than maintaining a constant value, allowing the system to adapt to varying material properties while preserving cutting accuracy.
Solution Approach 2:
The system incorporates sensors that continuously monitor tool-bone interaction forces and feed this information back to the controller. The controller processes this feedback and adjusts the feed rate accordingly, creating a closed-loop control system that maintains cutting accuracy despite variations in bone density.
2Temperature
If a constant rotational speed is used for the cutting tool, then the system is simple to control, but heat generation increases in denser materials
Solution Approach 1:
The rotational speed of the cutting tool is dynamically adjusted based on the sensed bone density and real-time interaction forces. When encountering denser bone material, the system automatically reduces rotational speed to minimize heat generation, while maintaining higher speeds in less dense areas.
Solution Approach 2:
The system changes the rotational speed parameter in response to varying material conditions. By monitoring bone density and tool interaction forces, the controller modifies the rotational speed parameter to optimize heat management while maintaining cutting efficiency.
3Productivity
If a uniform tool path is used, then the programming is simple, but operating time increases when removing material from non-homogeneous bone
Solution Approach 1:
The tool path is generated and adjusted dynamically based on pre-acquired bone density maps and real-time sensing data. The system creates variable depth and variable feed rate segments along the tool path, optimizing material removal efficiency for different bone density regions while maintaining a structured approach to path generation.
Solution Approach 2:
The system performs preliminary scanning or imaging of the bone to create a density map before generating the tool path. This advance knowledge allows the controller to pre-plan optimized feed rates and tool path segments for different bone density regions, reducing operating time without requiring complex real-time adjustments.
4Manufacturing precision
If a slower feed rate is used for denser bone material, then cutting accuracy is maintained, but operating time increases
Solution Approach 1:
The feed rate is dynamically adjusted to match the local bone density at each position along the tool path. In dense bone regions, the system uses slower feed rates to maintain cutting accuracy, while in less dense regions, it automatically increases the feed rate to reduce operating time, optimizing both precision and efficiency.
Solution Approach 2:
The system applies different feed rate parameters to different local regions of the bone based on their density characteristics. Rather than using a single feed rate for the entire operation, the controller tailors the feed rate to the specific material properties encountered at each location, achieving accuracy where needed and speed where possible.
Data Source
AI summary
A surgical robotic system and method involve a manipulator including a plurality of links and joints and a tool coupled to the manipulator. Controller(s) generate a first tool path to remove a first portion of material from the bone and control the manipulator to position the tool for movement along the first tool path to remove the first portion. The controller(s) sense interaction between the tool and the bone during movement of the tool along the first tool path and generate a second tool path to remove a second portion of material from the bone. Generation of the second tool path is based, at least in part, on the sensed interaction between the tool and the bone during movement along the first tool path. The controller(s) control the manipulator to position the tool for movement along the second tool path to remove the second portion.