Hybrid Inertial-Stellar Navigation for Harmonization Error Separation
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Solution Overview
Problem
Existing navigation systems face challenges in harmonizing the measurement reference frames of star tracking devices with inertial measurement units, leading to precision issues due to attitude and harmonization errors, which current error estimation methods fail to effectively address.
Innovation Solution
A navigation method that rigidly connects a star tracking device with a first inertial measurement device and a satellite positioning device, using a polar reference frame to calculate deviations and perform circular and linear regressions to separate and monitor attitude and harmonization errors, enabling precise error estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rigid connection of star tracking device with inertial measurement unit is implemented, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system uses the star tracking device itself to monitor and estimate its own attitude errors relative to the inertial measurement unit. By autonomously identifying celestial bodies and calculating position deviations, the star tracker performs self-diagnosis of harmonisation errors without requiring external calibration equipment or complex installation procedures.
Solution Approach 2:
The system continuously monitors the deviation between stellar position and hybrid inertial/GNSS position, feeds this error information back to estimate attitude and harmonisation errors, and uses these estimates to correct the measurement reference frame alignment. This closed-loop feedback mechanism maintains precision while simplifying installation.
2Ease of operation
If error estimation based on inertial measurement unit modelling is used, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The system introduces an intermediary measurement approach by using celestial body observations as a mediator to indirectly assess the attitude error of the inertial measurement unit. Instead of directly modelling complex inertial errors, the star tracking device observes celestial positions and uses these observations to infer harmonisation errors, providing a simpler and more accurate estimation method.
3Productivity
If hybrid inertial/GNSS navigation is implemented, then productivity is improved, but measurement precision deteriorates due to unmonitored attitude errors
Solution Approach 1:
The system continuously monitors attitude errors by comparing stellar position with hybrid inertial/GNSS position and feeds this error information back to correct the measurement reference frame. This feedback mechanism maintains high navigation productivity while ensuring position accuracy by actively compensating for attitude and harmonisation errors.
Solution Approach 2:
The system replaces complex mechanical alignment procedures with computational error estimation and correction. Instead of relying on precise physical mounting of the star tracker relative to the inertial unit, the system uses algorithmic processing of position deviations to estimate and correct attitude errors, maintaining precision while improving productivity.
Data Source
AI summary
A navigation method of a vehicle equipped with a star tracking device, a first inertial measurement device and a satellite positioning device, the star tracking device and the first inertial measurement device being connected to a single support. The method includes controlling movements of the support; simultaneously with these movements, calculating, in a horizontal plane, first positions of the vehicle, and second positions of the vehicle; calculating first deviations between the first positions and the second positions corresponding to each tracking heading and depicting them in a polar reference frame as a function of the corresponding heading and the values of the first deviations; carrying out a circular regression on said first deviations to determine, in this polar reference frame, a first circle; and determining a radius of the circle and a second deviation between a centre of the first circle and an origin of the polar reference frame.