Inertial Measurement Unit Parasitic Movement Detection
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Solution Overview
Problem
Current inertial sensors are ineffective in detecting low-frequency oscillatory movements and uniform rectilinear displacements during static alignment of inertial units, leading to accuracy issues in navigation initialization.
Innovation Solution
A method utilizing radio navigation measurements from multiple satellites to estimate displacement, comparing it with a predetermined threshold, and signaling parasitic movements, which provides more accurate detection of low-frequency oscillatory and uniform rectilinear movements by calculating phase variations and deviations between initial and subsequent signal receptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inertial sensors are used to detect parasitic movements during static alignment, then the detection method is simple and based on available onboard sensors, but the detection accuracy is insufficient for low-frequency oscillatory movements and uniform rectilinear displacements
Solution Approach 1:
The patent introduces radio navigation satellite signals as an intermediary measurement source to detect carrier movements during static alignment. By using signal phase measurements from multiple satellites, the system can detect low-frequency oscillatory movements and uniform rectilinear displacements that inertial sensors miss, while the processing unit acts as a mediator to compute displacement from these signals
Solution Approach 2:
The patent replaces the mechanical/inertial sensing approach with a radio navigation signal-based approach. Instead of relying on inertial sensors that measure acceleration, the system uses phase measurements of radio signals from navigation satellites to directly determine displacement, substituting the mechanical measurement principle with an electromagnetic signal processing approach
2Measurement precision
If GPS autonomous ground speed is used to detect parasitic movements, then the method provides additional measurement capability, but the precision is not sufficient for highly particular movements such as uniform rectilinear displacement and low-frequency oscillations
Solution Approach 1:
The patent changes the measurement parameter from velocity (GPS ground speed) to displacement derived from signal phase differences. By measuring the phase of radio navigation signals at different times and computing the difference, the system directly obtains displacement information with higher precision, enabling detection of subtle movements that velocity-based methods miss
Solution Approach 2:
The patent uses measurements from multiple satellites (excessive action) rather than a single satellite, and processes phase measurements from multiple time points. This provides redundant measurements that improve accuracy through statistical processing, allowing precise detection of delicate movements while maintaining robustness against individual measurement errors
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 method achieves higher accuracy in detecting parasitic movements, improving the discrimination between parasitic and non-parasitic movements, and allows for precise detection of delicate movements, enhancing the accuracy of inertial unit alignment.
Implementation Method 1
calculation of a position variation from: a phase of a first radio navigation signal transmitted by the satellite and received by the receiver at an initial reception time, and a phase of a second radio navigation signal transmitted by the satellite and received by the receiver at a subsequent reception time
Data Source
AI summary
The present invention concerns a method for detecting parasitic movements during static alignment of an inertial measurement unit (3), the method being characterised by steps of: receiving radio navigation measurements acquired (100) by a receiver (1) from signals previously transmitted by a set of radio navigation satellites (S), estimating (260) a movement of the inertial measurement unit from the acquired measurements, comparing (280) the estimated movement with a predefined threshold, indicating (290) a parasitic movement of the inertial measurement unit when the movement crosses the predefined threshold, in which the estimation (260) of the movement of the inertial measurement unit (3) from the acquired measurements comprises the following steps, implemented by the data processing unit for each satellite: calculating (262) a position variation from a phase of a first radio navigation signal transmitted by the satellite and received by the receiver at an initial reception time, and from a phase of a second radio navigation signal emitted by the satellite and received by the receiver at a subsequent reception time, estimating (264) a movement of the receiver relative to the satellite between the initial reception time and the subsequent reception time, calculating (266) a deviation between the calculated position variation and the estimated movement of the receiver relative to the satellite, the estimated movement of the inertial measurement unit depending on this deviation.