Navigation Unit Pseudorange Correction Against Error Amplification
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Solution Overview
Problem
Existing navigation unit location methods using pseudorange corrections based on previous positions are not robust and can lead to error amplification, causing divergence over time.
Innovation Solution
A method that uses the navigation unit's position to correct raw pseudorange measurements, employing a fusion algorithm with closed-loop integration and Kalman filters to improve precision and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pseudorange corrections are made using the preceding position estimated by the navigation unit, then the precision of the location is improved, but the robustness deteriorates and errors are amplified over time
Solution Approach 1:
The patent introduces an external position (obtained from a reference source) as an intermediary to correct pseudorange measurements, rather than using the navigation unit's own position. This external reference acts as a mediator that breaks the feedback loop causing error amplification, while still enabling precision improvement through correction of the measurements.
2Measurement precision
If feedback is used to correct measurements based on preceding position estimates, then measurement precision is improved, but error amplification occurs leading to divergence
Solution Approach 1:
The patent inverts the conventional feedback approach by using external position information to correct measurements, rather than using the system's own position estimates. This inversion breaks the unstable feedback loop where errors are amplified, while still achieving the goal of measurement correction through the use of reliable external reference data.
Data Source
AI summary
A method includes establishing, for a given time, measurement biases allowing an error affecting raw measurements of pseudoranges separating a navigation unit from at least three beacons to be decreased, and estimating an external position of the navigation unit at the given time based on: beacon positions, corrected pseudorange measurements computed for the given time using established measurement biases, and a preceding external position of the navigation unit estimated for a time preceding the given time. The measurement biases are established without taking into account the external position of the navigation unit.