AUV Magnetometer Compensation for Vehicle Magnetic Interference
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Solution Overview
Problem
Magnetic data collection during autonomous underwater vehicle (AUV) mapping surveys is hindered by vehicle-related magnetic fields, which obscure geological information and require complex compensation methods, often necessitating additional specialists and increased operational risks.
Innovation Solution
A system and method for magnetic data compensation involving a physical calibration maneuver and mathematical treatment of data, allowing for the calculation of correction terms to remove vehicle-induced magnetic effects, enabling the production of useful magnetic maps without requiring data to be placed in a geographic frame of reference prior to correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the magnetometer is mounted inside the AUV body, then the magnetic data can be collected during regular operations, but the vehicle-related magnetic fields obscure the geological information
Solution Approach 1:
The magnetic field measurement is segmented into two components: the total magnetic field measured by the magnetometer and the vehicle-induced magnetic field measured by the compensation magnetometer. By separating these measurements and processing them independently, the system can extract the geological signal by subtracting the vehicle's magnetic contribution from the total measurement.
Solution Approach 2:
A compensation magnetometer is introduced as an intermediary device to measure the vehicle-induced magnetic field. This additional sensor acts as a mediator that captures the interference signal, allowing the system to compensate for and remove the vehicle's magnetic signature from the geological data.
2Loss of information
If the magnetometer is mounted away from the AUV using towed body or long poles, then the vehicle magnetic fields are reduced, but the operational complexity and safety risks increase
Solution Approach 1:
The magnetometer and compensation magnetometer are merged into a single integrated measurement system mounted on the AUV. This combination allows both the geological magnetic field and the vehicle-induced field to be measured simultaneously at the same location, eliminating the need for separate mounting apparatus while maintaining data quality through computational separation of the signals.
3Loss of information
If degaussing of the AUV is performed to remove static magnetic vehicle fields, then the magnetic data quality improves, but the process is difficult and the effects wear off over time
Solution Approach 1:
The compensation magnetometer is calibrated before deployment to establish a baseline of the vehicle's magnetic signature. This preliminary calibration allows the system to pre-compute compensation values that can be applied during data processing, eliminating the need for difficult degaussing procedures while maintaining data quality.
4Measurement precision
If additional specialists are added to the survey crew to process magnetic data, then the data processing capability improves, but the operational cost and complexity increase
Solution Approach 1:
The system performs automatic compensation for vehicle-induced magnetic fields through real-time processing of data from both the magnetometer and compensation magnetometer. This self-service capability allows the survey team to process magnetic data without requiring specialized geophysical expertise, as the system automatically removes the vehicle's magnetic signature and produces corrected geological data.
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 effectively compensates for vehicle-related magnetic fields, producing accurate magnetic maps for subsurface geology interpretation without the need for additional specialists or increased operational complexity, as demonstrated in experimental results from seafloor hydrothermal venting areas.
Implementation Method 1
raw magnetic data output from a magnetometer
Implementation Method 2
applying magnetic compensation coefficients to the raw magnetic data to produce compensated magnetic survey data
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
In the field of magnetic surveying for underwater mineral exploration a subsea vehicle with a mounted magnetometer is maneuvered while a microprocessor produces magnetic compensation coefficients from raw magnetometer data and vehicle state and performance data. The coefficients can then be used to compensate the magnetic fields from the vehicle while performing the same maneuvers during an actual subsea mapping.