Sensor Fusion of Gravimeters and Accelerometers for Low-Bias Navigation
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Solution Overview
Problem
Inertial navigation systems suffer from increasing errors over time due to integration, and GPS/GNSS systems are susceptible to interference, making them unreliable for navigation. Gravity anomaly-referenced navigation systems offer resistance to jamming but face challenges with noise levels in gravimeters.
Innovation Solution
A sensor data fusion system combining low-noise, high-bias accelerometers with high-noise, low-bias gravimeters to achieve reduced noise and bias, using subtracters, filters, and fault detectors to produce a synthetic sensor with improved accuracy and fault protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a gravimeter is used to measure specific force, then noise levels are high (25 micro-g/sqrt(Hz)), but bias levels are acceptable (1 micro-g)
Solution Approach 1:
The patent combines a gravimeter (high-noise, low-bias sensor) with a traditional accelerometer (low-noise, high-bias sensor) into a sensor fusion system. The system processes signals from both sensors through subtraction and filtering operations to produce a fused output that achieves both low noise and low bias characteristics, effectively merging the complementary strengths of the two sensors to resolve the individual performance limitations of each sensor type
2Productivity
If inertial measurement units are used for navigation, then navigation solution can be obtained, but errors increase over time due to integration
Solution Approach 1:
The patent implements a feedback mechanism where the gravimeter measurements are continuously used to correct and update the inertial navigation solution. The sensor fusion system processes the difference between gravimeter and accelerometer signals to estimate bias, which is then fed back to correct the inertial navigation accumulations, creating a closed-loop system that maintains accuracy over time by continuously correcting drift errors
3Productivity
If GPS and GNSS systems are used for navigation, then positioning is available, but signals are susceptible to interference and jamming
Solution Approach 1:
The patent uses a sensor fusion system as an intermediary between the physical environment and the navigation solution. By fusing gravimeter and accelerometer data through signal processing operations (subtraction, filtering), the system creates a navigation solution that is independent of external electromagnetic signals, thereby protecting against GPS jamming and interference while maintaining positioning capability
Data Source
AI summary
Sensor data fusion systems that provide noise reduction and fault protection. The sensor data fusion system fuses data acquired by respective accelerometers having different attributes. For example, one accelerometer has low noise and high bias, while another accelerometer has high noise and low bias when measuring specific force. The high-noise, low-bias accelerometer may be a gravimeter. Gravimeters and traditional accelerometers measure the same physical variable, i.e., specific force. By combining an expensive gravimeter and low-cost accelerometers, a synthetic sensor having both low noise and low bias may be achieved. Such synthetic sensors may be utilized in a gravity anomaly-referenced navigation system to achieve improved navigation performance.