Integrated Inertial Gravimeter Navigation for GPS-Denied Drift Correction
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Solution Overview
Problem
Current navigation systems face challenges in GPS-denied environments, with inertial navigation systems experiencing drift, vision-based solutions requiring visibility, celestial solutions needing specific conditions, magnetic sensors being susceptible to interference, and gravitational anomaly navigation systems being hindered by the size, cost, and complexity of required sensors.
Innovation Solution
An integrated inertial and gravitational anomaly navigation system using a strapdown or gimballed IMU with a vertical accelerometer functioning as a gravimeter, along with a navigation algorithm that estimates errors and incorporates a map of gravitational anomalies, allowing for error correction and improved navigation performance without relying on external aids or high-performance gradiometers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gravitational anomaly navigation systems use high performance gravimeters, then navigation accuracy is improved, but system size, complexity, and cost increase
Solution Approach 1:
The patent combines the gravimeter and inertial measurement unit (IMU) into a single integrated sensor assembly. The gravimeter measures vertical acceleration while the IMU measures horizontal accelerations and rotational rates. By merging these sensors and processing their outputs together through a unified navigation algorithm, the system achieves gravitational anomaly navigation without requiring a separate complex gravimeter system, thus reducing overall system complexity while maintaining navigation accuracy
Solution Approach 2:
The vertical accelerometer in the integrated sensor assembly serves dual functions: it acts as both an inertial sensor for measuring vertical motion and as a gravimeter for detecting gravitational anomalies. This multi-functionality eliminates the need for dedicated high-performance gravimeters, reducing system complexity, size, and cost while maintaining the capability to measure gravitational anomalies for navigation
2Measurement precision
If gravitational gradient navigation uses gradiometers, then gravitational field measurement capability is improved, but device size, weight, and power requirements increase
Solution Approach 1:
The patent merges the gravimeter with the IMU into a single integrated sensor package, eliminating the need for separate gradiometer assemblies. The vertical accelerometer in the integrated unit provides gravitational field measurement capability while sharing mechanical support, power, and processing resources with the inertial sensors, thereby significantly reducing device weight compared to traditional gradiometer-based systems
Solution Approach 2:
Instead of using complex gradiometers that directly measure gravitational gradients, the system uses a single vertical accelerometer to measure vertical acceleration and derives gravitational anomaly information through navigation algorithms that process this data along with position and velocity information. This computational approach replaces heavy physical instrumentation with lighter sensing and processing
3Adaptability or versatility
If inertial navigation systems operate without external aids, then autonomy is improved, but navigation drift increases over time
Solution Approach 1:
The system uses gravitational anomaly measurements as feedback to correct inertial navigation drift. The navigation algorithm continuously compares the measured vertical acceleration with the expected gravitational acceleration at the current position (obtained from Earth gravity models) and uses any discrepancies to update position, velocity, and attitude estimates. This feedback mechanism bounds navigation errors over time while maintaining complete autonomy without requiring external GPS or other external aids
Solution Approach 2:
The integrated sensor system performs self-calibration and self-correction by using its own vertical accelerometer measurements to detect and correct drift in the inertial navigation solution. The system serves its own navigation needs by generating and processing its own gravitational anomaly data, eliminating dependence on external correction sources while maintaining long-term accuracy
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 solution enables robust navigation in GPS-denied environments by accurately estimating navigation and sensor errors, potentially offering higher performance than traditional systems and reducing the need for costly and complex sensors, while not requiring terrain or magnetic aiding sources.
Implementation Method 1
a map of gravitational anomalies and at least one navigation algorithm... The measured gravitational anomaly is used as an input to the algorithm
Implementation Method 2
an integrated inertial measurement unit (IMU) and a gravimeter... inertial navigation systems (INS) solutions drift over time
Data Source
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AI summary
A system implementing a method for generating a navigation output is provided. The method includes determining a gravitational anomaly estimate based at least in part on inertial sensor data and navigation output; generating navigation and sensor corrections that are due at least in part on inherent sensor errors that include vertical accelerometer/gravimeter corrections from at least a navigation output estimate, the gravitational anomaly estimate, and the gravity map data; and generating the navigation output based on the inertial sensor data, gravity map data and the navigation and sensor corrections.