Self-Describing Fiducials for GPS-Denied Navigation
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Solution Overview
Problem
Existing navigation systems face challenges in maintaining accurate position, velocity, and attitude (PVA) estimates in GPS-denied or limited environments, such as urban canyons, due to inaccuracies in GPS measurements and IMU sensor drift, leading to Kalman filter divergence and inadequate guidance performance.
Innovation Solution
The development of self-describing fiducials that broadcast their position or identity, allowing navigating objects to determine their location and orientation, combined with a vision system that extracts this information and uses line-of-sight measurements for navigation and guidance, providing unbiased PVA estimates independent of GPS signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If GPS-based navigation is used, then long-term position stability is improved, but measurement accuracy deteriorates in GPS-denied environments
Solution Approach 1:
The patent introduces fiducial markers as intermediary objects that mediate between the navigating object and the environment. These markers contain encoded position information that the vision system can detect, providing a reliable reference system in GPS-denied environments. The fiducial markers act as a bridge, allowing the navigation system to obtain accurate position information without relying on GPS signals.
2Measurement precision
If IMU measurements are used for short-term navigation, then measurement accuracy is improved, but long-term stability deteriorates due to sensor drift
Solution Approach 1:
The patent implements a feedback mechanism where the vision system periodically detects fiducial markers to obtain accurate position information. This information is fed back to correct the drift accumulated by IMU measurements over time. The feedback loop allows the system to maintain long-term stability by continuously correcting short-term integration errors without sacrificing short-term measurement accuracy.
3Productivity
If Kalman filter is used to blend GPS and IMU measurements, then navigation performance is improved, but reliability deteriorates in GPS-denied environments due to filter divergence
Solution Approach 1:
The fiducial markers serve as an intermediary reference system that allows the navigation algorithm to maintain reliability in GPS-denied environments. By detecting these markers, the system can establish an independent reference frame that does not depend on GPS signals, preventing Kalman filter divergence and maintaining navigation reliability throughout the flight.
4Device complexity
If passive fiducial markers are used, then device complexity is reduced, but information transmission capability deteriorates
Solution Approach 1:
The patent applies parameter changes by encoding position information directly into the visual appearance of the fiducial markers. Instead of using simple passive markers, the system varies parameters such as marker color, pattern, or arrangement to represent different position information. This allows the markers to transmit rich position data while maintaining relative simplicity in implementation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables robust and secure autonomous navigation with minimal uncertainty, allowing drones and other objects to accurately follow desired paths, even in GPS-denied areas, by using high-contrast fiducials that communicate their location and ancillary information, thereby enhancing navigation accuracy and efficiency.
Implementation Method 1
a light source that optically communicates navigation-aiding information
Data Source
AI summary
In one embodiment, a self-describing fiducial includes a communication element that optically communicates navigation-aiding information. The navigation-aiding information may include a position of the self-describing fiducial with respect to one or more coordinate systems and the communication element communicates the navigation-aiding information to one or more navigating objects in the vicinity of the self-describing fiducial.