Robotic Surgical Tool Virtual Boundary Force Modeling
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Solution Overview
Problem
Conventional robotic systems face challenges in modeling and computing reactive forces for virtual boundaries, leading to inconsistent tool movement when penetrating complex virtual surfaces, especially when engaging multiple triangles or rolling over non-planar surfaces, due to simplistic linear depth-based modeling that neglects cross-sectional area and displaced volume considerations.
Innovation Solution
A robotic system and method where a controller computes reactive forces based on a penetration factor that accounts for the geometry of a virtual volume relative to a polygonal element, using projected area, projected arc, or displaced volume to simulate dynamic interactions and constrain tool movement, providing consistent and smooth responses to virtual boundary interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional linear depth-based modeling is used to compute reactive forces, then the computation is simple, but the tool movement becomes inconsistent when penetrating multiple triangles or rolling over non-planar surfaces
Solution Approach 1:
The patent changes the parameters used for computing reactive forces from simple linear depth to a combination of linear depth, cross-sectional area, and displaced volume. This allows the system to account for the geometry of both the tool and the virtual surface, providing consistent tool movement responses when penetrating multiple triangles or rolling over non-planar surfaces while maintaining computational feasibility through efficient geometric calculations.
2Ease of operation
If the same counter force is applied based on linear depth regardless of cross-sectional area or displaced volume, then the computation is straightforward, but the response does not account for different penetration scenarios
Solution Approach 1:
The patent applies local quality by computing reactive forces differently based on the local geometric characteristics of the penetration scenario. Instead of using a uniform counter force model, the system calculates cross-sectional area and displaced volume specific to each penetration event, allowing the reactive force to adapt to different penetration scenarios such as penetrating flat surfaces, rolling over corners, or engaging multiple triangles with varying geometric properties.
3Reliability
If conventional surface modeling is used, then the virtual boundary can be defined, but unexpected kick-back occurs when the tool simultaneously penetrates multiple triangles or engages vertices
Solution Approach 1:
The patent applies preliminary action by pre-defining the geometric properties of the tool (cross-sectional area, volume) and using these to compute the reactive force before the actual penetration occurs. The system calculates the displaced volume and cross-sectional area of the virtual volume at the penetration depth, then applies the reactive force based on these pre-computed geometric factors. This prevents unexpected kick-back by ensuring the reactive force accurately reflects the actual penetration scenario, whether engaging single triangles, multiple triangles, or vertices.
Data Source
AI summary
A robotic system and methods are provided. The robotic system includes a tool and a manipulator with links for moving the tool. A controller implements a virtual simulation wherein the tool is represented as a virtual volume interacting with a virtual boundary defined by a mesh of polygonal elements. The controller computes a reactive force responsive to penetration of polygonal elements by the virtual volume. The reactive force is computed based on a penetration factor being a function of a geometry of the virtual volume bound relative to a geometry of the polygonal element. The controller applies the reactive force to the virtual volume to reduce penetration of the polygonal element by the virtual volume. The controller commands the manipulator to move the tool in accordance with application of the reactive force to the virtual volume to constrain movement of the tool relative to the virtual boundary.