Inertial Reference System Aided-Alignment Mode
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Solution Overview
Problem
Inertial navigation systems struggle to align when the body they are attached to is in motion or when power interruptions occur, as they require stationary conditions for self-alignment, leading to delays and reduced navigational capabilities.
Innovation Solution
A system and method that utilize both unaided and aiding sources, such as inertial sensors and external GPS data, to perform an aided-alignment mode, allowing alignment during motion and after power cycling, using combinations of in-motion alignment, reversionary-attitude, warm-start, and hot-start initialization modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stationary-alignment mode is used to align the IRS, then alignment accuracy is improved, but alignment time increases significantly and the system cannot align when the body is in motion
Solution Approach 1:
The patent implements multiple alignment modes (stationary-alignment mode, reversionary-attitude mode, and aided-alignment mode) that allow the system to adapt dynamically to different operational conditions. The system transitions between these modes based on whether the body is stationary or in motion, enabling alignment functionality across the full range of motion states while maintaining appropriate accuracy levels for each mode.
Solution Approach 2:
The patent introduces an aided alignment mode that uses external aiding sources (such as GPS, visual references, or other navigation systems) as intermediaries to assist the inertial sensors during alignment. This intermediary approach enables the system to achieve alignment when the body is in motion by combining inertial measurements with external reference data, thereby reducing the alignment time constraint while maintaining acceptable accuracy.
2Reliability
If stationary-alignment mode is used, then complete navigation solution (attitude, position, velocity) is achieved, but the system requires the body to remain stationary for extended periods
Solution Approach 1:
The system dynamically selects among multiple alignment modes based on operational conditions. When the body is stationary, the system uses stationary-alignment mode to achieve complete navigation solutions. When the body is in motion or power interruptions occur, the system transitions to reversionary-attitude mode or aided-alignment mode, maintaining operational flexibility and adaptability across different flight scenarios while preserving navigation capability.
Solution Approach 2:
The patent segments the alignment process into distinct modes with different functional capabilities. The stationary-alignment mode provides complete navigation solutions when conditions permit, while reversionary-attitude mode and aided-alignment mode provide alternative solutions with varying degrees of navigation parameter availability. This segmentation allows the system to maintain reliability across different operational conditions by providing appropriate navigation solutions for each mode.
3Measurement precision
If power interruption occurs during stationary-alignment mode, then the alignment process is interrupted and navigation capability is lost, requiring system reset and re-alignment
Solution Approach 1:
The patent implements reversionary-attitude mode as a pre-prepared fallback mechanism that automatically activates when power interruptions or excessive movement occur during stationary-alignment mode. This beforehand cushioning ensures that the system maintains navigation capability and does not require a full reset, as the reversionary mode is already initialized and ready to provide attitude information using non-accelerating assumptions and second-order control loops.
Solution Approach 2:
The system continuously monitors operational conditions (power status, body movement) and provides feedback to determine whether to maintain stationary-alignment mode or transition to reversionary-attitude mode or aided-alignment mode. This feedback mechanism ensures that the system responds appropriately to power interruptions and maintains navigation capability by switching to modes that are resilient to the detected conditions.
4Speed
If reversionary-attitude mode is used for quick recovery, then system responsiveness is improved, but heading output is null and requires external heading input
Solution Approach 1:
The patent implements aided-alignment mode that performs preliminary actions to establish accurate heading information before transitioning to full navigation mode. The aided alignment mode uses external aiding sources (GPS, visual references) to determine heading during the alignment process, so that when the system transitions to navigation mode, accurate heading information is already available. This preliminary action eliminates the need for external heading inputs that would otherwise be required in reversionary-attitude mode.
Data Source
AI summary
A system and method for aligning an inertial reference system, which is coupled to a moveable body, is provided. The method includes obtaining unaided navigation state information from an unaided source, and obtaining aiding state information from an aiding source. The unaided navigation state information is generated by the unaided source using navigation information provided by an inertial reference, and the aiding state information is generated by the aiding source using navigation information provided by at least one external reference.The method also includes determining an unaided navigation solution using the unaided navigation state information, and determining an aided navigation solution using a combination of the unaided and aiding state information. As a default, the method provides the unaided navigation solution for navigating the movable body. When the aided navigation solution provides a better solution for navigating the movable body, the unaided navigation solution is replaced with the aided navigation solution.