Doorway Detection Using Line Tracking and Vanishing Point Verification
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Solution Overview
Problem
Existing doorway detection methods for robots are limited in their ability to detect doorways from various angles and perspectives, particularly failing when top and bottom frames are not observed or when doors are unfamiliar, as they rely on shape and appearance information that is not generalizable to diverse door types and require extensive training data.
Innovation Solution
A system using line tracking and vanishing point-based verification, which extracts salient line segments from images, determines the existence of a vanishing point to switch between frontal and side doorway detection modules, and employs edge tracking and image intensity variance to validate door hypotheses, allowing for robust detection of doorways without the need for extensive offline training.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If training-based classification approaches are used for door detection, then detection accuracy improves for familiar door types, but the system fails to generalize to unseen door types and requires extensive training data
Solution Approach 1:
The patent changes the detection parameters from appearance-based features to geometry-based features (line orientations, vanishing points, relative positions). This allows the system to detect doors by their structural parameters rather than appearance, enabling generalization to unseen door types while maintaining detection accuracy
Solution Approach 2:
The patent extracts only the essential geometric features (line segments, vanishing points, orientation angles) from door images, discarding appearance information. This extraction of critical geometric parameters enables the system to work with diverse door types without requiring training data
2Reliability
If appearance and shape information are used for door validation, then detection performance improves on training data, but the learned features are not generalizable to diverse door types in real world
Solution Approach 1:
The patent validates doors by checking geometric parameters (line orientations within specific angle ranges, vanishing point distances, relative positions of door lines) rather than appearance features. This parameter-based validation ensures reliability across diverse door types without requiring learned features
Solution Approach 2:
The patent creates a universal door detection framework that works for all door types by using common geometric properties (parallel lines, vanishing points, orientation angles) that are invariant to door appearance, material, or style variations
3Measurement precision
If manual parameter tuning is used for door validation, then detection can be optimized for specific scenarios, but parameters cannot be adjusted online based on distance to vanishing point or other information
Solution Approach 1:
The patent makes the validation parameters dynamic by adjusting them based on the distance to the vanishing point. As the robot moves closer or farther from doors, the acceptable ranges for line orientations and positions are automatically adjusted, eliminating the need for manual retuning while maintaining precision
Solution Approach 2:
The system uses feedback from vanishing point detection and line tracking to continuously adjust validation parameters. The detected geometric features feed back into the validation process, allowing automatic adaptation to different distances and viewing conditions
4Measurement precision
If corner detection is required for frontal door detection, then door hypotheses can be validated, but the method cannot detect side doorways when top and bottom frames are not observed
Solution Approach 1:
The patent extracts only the essential vertical line segments that define door positions, removing the requirement to detect corners or horizontal frames. This simplification allows detection of side doorways where top and bottom frames may be occluded or not visible
Solution Approach 2:
The patent creates a universal detection approach that works for both frontal and side doorways by using only vertical line segments and vanishing point geometry, which are present in all door configurations regardless of viewing angle or frame visibility
Data Source
AI summary
Described is a system for frontal and side doorway detection. Salient line segments are extracted from an image frame captured of an indoor environment. Existence of a vanishing point in the image frame is determined. If a vanishing point is detected with a confidence score that meets or exceeds a predetermined confidence score, then the system performs side doorway detection via a side doorway detection module. If a vanishing point is detected with a confidence score below the predetermined confidence score, then the system performs frontal doorway detection via a frontal doorway detection module. A description of detected doorways is output and used by a mobile robot (Unmanned Aerial Vehicle) to autonomously navigate the indoor environment.