Hybrid Visual Inertial Odometry Attitude Drift Calibration
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Solution Overview
Problem
Advanced Driver Assistance Systems (ADAS) and navigation systems face accuracy challenges due to degradation of Global Navigation Satellite Systems (GNSS) in urban canyons, where multipath effects and limited satellite visibility lead to significant position errors, and inertial sensor drift hampers reliable positioning.
Innovation Solution
A method combining GNSS measurements with Visual Inertial Odometry (VIO) to determine absolute and relative positions, using non-GNSS sensors like LIDAR and RADAR to stitch together time-separated GNSS measurements, and resolve carrier phase ambiguities, even when GNSS signals are unavailable or unreliable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GNSS measurements are used for positioning, then absolute position accuracy can be achieved, but accuracy degrades significantly in urban canyons due to multipath effects and limited satellite visibility
Solution Approach 1:
The patent combines GNSS carrier phase measurements with Visual Inertial Odometry (VIO) to create a hybrid positioning system. The VIO component uses visual features and inertial sensors to estimate relative displacement, which is then integrated with GNSS measurements to maintain positioning accuracy in urban canyons where GNSS alone would fail due to multipath effects and limited satellite visibility.
Solution Approach 2:
The patent introduces VIO-based relative displacement as an intermediary to bridge GNSS measurement gaps. When GNSS signals are unavailable or unreliable, the VIO system continuously tracks visual features and integrates inertial data to provide accurate relative position estimates, which serve as a mediator to maintain positioning continuity and accuracy.
2Measurement precision
If carrier phase measurements are used to achieve higher accuracy, then positioning precision improves, but the system requires constant lock on at least four satellites which may not be possible due to environmental conditions
Solution Approach 1:
The patent implements a dynamic positioning system that adapts its measurement strategy based on environmental conditions. When satellite visibility is sufficient, the system uses carrier phase measurements for high precision. When environmental conditions prevent constant lock on four satellites, the system dynamically switches to VIO-based relative displacement estimation, maintaining positioning functionality across varying environmental conditions.
Solution Approach 2:
The patent changes the measurement parameters used for positioning based on environmental conditions. In open sky conditions, it uses GNSS carrier phase measurements with wavelength-level precision. In urban canyon conditions, it transitions to using visual feature tracking and inertial sensor integration, changing the fundamental measurement parameters to match the available environmental information.
3Reliability
If VIO is used for positioning, then positioning can function without GNSS, but attitude drift occurs over time
Solution Approach 1:
The patent implements a feedback mechanism where VIO-based relative displacement estimates are continuously compared with and corrected by GNSS carrier phase measurements when available. The GNSS measurements provide feedback to correct the accumulating attitude drift in the VIO system, maintaining long-term accuracy while preserving the ability to function without GNSS when needed.
Solution Approach 2:
The patent uses VIO to establish preliminary relative displacement estimates that serve as a foundation for positioning when GNSS is unavailable. These preliminary estimates are then refined and corrected when GNSS measurements become available, allowing the system to maintain continuous accurate positioning by preparing advance estimates that can be quickly adjusted.
Data Source
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AI summary
Disclosed embodiments pertain to a method on a UE may comprise determining a first absolute position of the UE at a first time based on GNSS measurements from a set of satellites. At a second time subsequent to the first time, the UE may determine a first estimate of displacement of the UE relative to the first absolute position using non-GNSS measurements. Further, at the second time, the UE may also determine a second estimate of displacement relative to the first absolute position and/or a second absolute position of the UE based, in part, on: the GNSS carrier phase measurements at the first time from the set of satellites, and GNSS carrier phase measurements at the second time from a subset comprising two or more satellites of the set of satellites, and the first estimate of displacement of the UE.