Adaptive Spectral Density Adjustment for Inertial Navigation Filters
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Solution Overview
Problem
Conventional inertial navigation systems face inefficiencies and inaccuracies due to static spectral noise density models that fail to adapt to varying environmental conditions, leading to mischaracterization of IMU errors in disturbed environments and increased reliance on noisy external aiding sensors during steady state conditions.
Innovation Solution
An adaptive spectral density module adjusts the spectral noise density based on real-time environmental conditions, using internal and external data to determine whether the system is in a steady or disturbed state, thereby dynamically switching between different error models to optimize navigation solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the spectral density is set to a lower static value for steady state conditions, then the navigation filter accuracy is improved in steady state environments, but the filter cannot efficiently and accurately assess increased IMU errors in disturbed environments
Solution Approach 1:
The patent implements a dynamic spectral density model that transitions from static to adaptive based on environmental conditions. The system uses a disturbance detector to monitor environmental parameters and dynamically adjusts the spectral density value accordingly - maintaining low values during steady state for accuracy, and increasing values during disturbed conditions to properly characterize IMU errors. This dynamic adaptation resolves the contradiction by making the spectral density flexible rather than fixed.
Solution Approach 2:
The system changes the spectral density parameter based on detected environmental conditions. When disturbances are detected (through temperature sensors, vibration sensors, or other environmental monitors), the spectral density value is increased to account for higher IMU error characteristics. This parameter change allows the filter to maintain accuracy in steady state while becoming robust in disturbed environments, directly resolving the measurement precision versus adaptability contradiction.
2Speed
If the spectral density is set to a higher static value for disturbed environments, then the IMU error corrections can respond to disturbances more quickly, but increased reliance on noisy external aiding sensor data negatively affects navigation filter accuracy during steady state conditions
Solution Approach 1:
The system dynamically adjusts spectral density based on real-time environmental monitoring rather than using a fixed high value. During steady state, the spectral density remains low to maintain accuracy and reduce reliance on noisy external sensors. When disturbances are detected, the spectral density increases to improve response speed and robustness. This dynamic behavior resolves the contradiction between response speed and accuracy by adapting the spectral density to current operating conditions.
Solution Approach 2:
The system periodically monitors environmental conditions (temperature, vibration, etc.) and adjusts the spectral density accordingly. This periodic detection and adjustment mechanism ensures that the spectral density is high only when needed (during disturbed conditions) and low during steady state, resolving the contradiction by applying high spectral density intermittently rather than continuously.
3Device complexity
If static steady state models are used in disturbed environments, then the model simplicity is maintained, but the navigation filter cannot efficiently and accurately determine the navigation solution
Solution Approach 1:
The patent implements a dynamic model selection mechanism that switches between simple steady state models and more complex disturbed environment models based on detected conditions. The disturbance detector monitors environmental parameters and triggers model switching when disturbances are detected. This dynamic model adaptation maintains simplicity during steady state while ensuring reliability during disturbed conditions, resolving the contradiction between model complexity and navigation solution accuracy.
Solution Approach 2:
The system creates a universal error model framework that can operate in both steady state and disturbed environments by incorporating conditional logic. The model uses environmental sensors to determine operating conditions and automatically adjusts its behavior - using simple steady state assumptions when appropriate and transitioning to disturbed environment characteristics when needed. This multi-functional approach resolves the contradiction by making a single model adaptable to multiple operating conditions.
Data Source
AI summary
Techniques are provided for adjusting a spectral density for computing a filtering solution. In an embodiment, a rolling history of correction data for a current epoch and previous epochs is created to compute a statistical value. The statistical value can be used to compute long-term and short-term averages for the current epoch. The long-term and short-term averages can be used to compute a ratio value that can be a scale factor for adjusting the spectral density. In an embodiment, sensor data for a current epoch can be obtained and compared to one or more threshold values and the spectral density can be adjusted when the threshold values are exceeded. In an embodiment, misclosure values from two different filters may be used to determine if a steady-state model of a first filter or a disturbed model of a second filter should be used to compute a filtering solution.


