Robotic Surgical Virtual Boundaries Using Volumetric Reactive Force
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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 penetration modeling that neglects cross-sectional area and displaced volume.
Innovation Solution
The robotic system computes reactive forces as a function of the volume of the penetrating portion of a virtual volume interacting with a mesh of polygonal elements, applying these forces to reduce penetration and command the manipulator to move the tool consistently, accounting for the geometry of both the virtual volume and polygonal elements, thereby providing a more accurate and natural response to surface interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional linear depth penetration modeling is used to compute reactive forces, then the computation is simple, but the tool movement becomes inconsistent and unexpected when penetrating complex virtual surfaces
Solution Approach 1:
The patent changes the parameter used for computing reactive forces from simple linear depth of penetration to a composite parameter that includes cross-sectional area and displaced volume of the virtual surface. This transformation of parameters resolves the contradiction by providing more comprehensive geometric information while maintaining computational feasibility through systematic calculation methods.
Solution Approach 2:
The patent transitions from one-dimensional linear depth measurement to three-dimensional volumetric measurement by incorporating cross-sectional area and displaced volume. This dimensional expansion provides a more complete characterization of penetration geometry, eliminating the inconsistencies that arise with simple linear depth modeling when tools penetrate complex virtual surfaces.
2Device complexity
If linear depth of penetration is used as the sole basis for counter force calculation, then the modeling is simple, but it fails to account for differences in cross sectional area and displaced volume
Solution Approach 1:
The patent introduces additional parameters (cross-sectional area and displaced volume) to the penetration measurement model. This multi-parameter approach replaces the insufficient single-parameter linear depth model, enabling accurate differentiation between penetrations of identical depth but different geometric significance.
Solution Approach 2:
The patent creates a composite measurement model that combines multiple geometric parameters (linear depth, cross-sectional area, and displaced volume) into a unified penetration characterization. This composite approach similarly integrates multiple aspects of penetration geometry to achieve comprehensive and accurate measurement.
3Ease of operation
If the same counter force is applied based on linear depth regardless of tool shape or pose, then the control is simple, but it produces inconsistent forces when the same linear depth corresponds to different cross sectional areas
Solution Approach 1:
The patent modifies the force calculation parameters to include cross-sectional area and displaced volume in addition to linear depth. This enhanced parameter set enables the control system to differentiate between various penetration scenarios and apply appropriate forces, resolving the inconsistency while maintaining systematic control procedures.
4Adaptability or versatility
If conventional surface modeling is used, then it handles simple surfaces well, but it produces cumulative force spikes when the tool rolls over outside corners defined by the virtual surface
Solution Approach 1:
The patent transitions from two-dimensional surface area measurement to three-dimensional volume measurement by incorporating displaced volume calculations. This dimensional enhancement provides a more accurate representation of tool-surface interaction, particularly at corners and edges where conventional surface modeling produces erroneous cumulative force spikes.
Data Source
AI summary
Robotic systems and methods employ a virtual simulation wherein a tool is represented as a virtual volume adapted to interact relative to a virtual boundary defined by a mesh of polygonal elements. A reactive force is computed in response to penetration of one of the polygonal elements by the virtual volume in the virtual simulation. The reactive force is computed as a function of a volume of a penetrating portion of the virtual volume that is penetrating a plane of the polygonal element. The reactive force is applied to the virtual volume in the virtual simulation for reducing penetration of the polygonal element by the virtual volume.