Magnetic Sensor Navigation Feedback for GNSS-Denied Position Drift
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Solution Overview
Problem
Existing navigation systems face challenges in environments with limited or unreliable GNSS signals, and other navigation information sources like inertial sensors and aiding sensors are prone to errors that cause drift and inaccuracies in position and velocity estimation.
Innovation Solution
A navigation system utilizing magnetometers and magnetic gradient sensors to measure magnetic gradients and fields, combined with inertial sensor data, to estimate local magnetic fields and update navigation solutions using statistical filters like the Extended Kalman Filter, reducing position drift and bounding velocity errors without relying on magnetic anomaly maps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inertial sensors and aiding sensors are used for navigation when GNSS is unavailable, then navigation capability is maintained, but position drift and velocity errors increase over time
Solution Approach 1:
The patent implements feedback by continuously measuring the magnetic field with a magnetometer and comparing it to the predicted magnetic field based on inertial navigation estimates. The difference (residual) is fed back to correct the velocity and position estimates, preventing drift accumulation. This closed-loop feedback mechanism maintains measurement precision while preserving navigation capability in GNSS-denied environments.
Solution Approach 2:
The magnetometer serves as an intermediary sensor that provides magnetic field measurements to mediate between inertial navigation and the environment. Instead of directly measuring position or velocity like GNSS does, the magnetometer measures the magnetic field, which indirectly constrains the navigation solution and reduces errors through the measurement model that relates magnetic field changes to vehicle motion.
2Measurement precision
If magnetic anomaly maps are used for magnetic anomaly-aided navigation, then position estimation can be improved, but system complexity and dependency on pre-existing maps increase
Solution Approach 1:
The patent extracts the magnetic field measurement function from the complex magnetic anomaly-aided navigation system that requires pre-existing maps. By using only the magnetometer to measure the local magnetic field and comparing it to predictions from inertial navigation, the system removes the dependency on magnetic anomaly maps while still achieving position and velocity estimation improvement.
Solution Approach 2:
The system performs self-service by using its own inertial navigation estimates to predict the magnetic field, then using the actual magnetic field measurement to correct those same estimates. This self-contained approach eliminates the need for external magnetic anomaly maps or additional infrastructure, reducing system complexity while maintaining improved measurement precision.
3Measurement precision
If multiple magnetometers are used to measure magnetic gradients, then navigation accuracy improves, but device complexity and cost increase
Solution Approach 1:
The magnetometer is designed to perform multiple functions: it measures the magnetic field for navigation correction, provides data for computing magnetic gradients, and contributes to both position and velocity estimation. This multi-functionality allows the system to achieve improved navigation accuracy without adding separate dedicated sensors for each function, thereby limiting the increase in device complexity.
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 approach enhances navigation accuracy by reducing position drift and bounding velocity errors, even in GNSS-denied or contested environments, using magnetic field measurements to correct and refine navigation estimates.
Implementation Method 1
a magnetometer located at a location on the moving object to measure a magnetic field at the location
Implementation Method 2
a magnetic gradient sensor to measure magnetic gradients over an area
Data Source
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AI summary
Systems and methods for navigation with magnetic field sensors are provided. For example, a system includes a magnetic gradient sensor that measures a magnetic gradient. The system also includes one or more inertial sensors that provide inertial measurements. Additionally, the system includes a magnetic field sensor that measures magnetic fields. Further, the system includes one or more processors that execute computer-readable instructions th400 2484at direct the one or more processors to estimate a magnetic field based on the measured magnetic gradient and a velocity estimate from the inertial measurements. The computer-readable instructions also direct the one or more processors to calculate an error for the magnetic field and other navigation parameters using an additional magnetic field measurement from the magnetic field sensor.