AUV CSEM Buried Object Detection
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Solution Overview
Problem
Existing underwater detection methods for buried conductive objects in seabed, such as passive magnetometers and active Controlled Source Electromagnetic (CSEM) technologies, face challenges in efficiency and effectiveness due to limitations in signal propagation and data processing requirements.
Innovation Solution
A system comprising an Autonomous Underwater Vehicle (AUV) or Unmanned Surface Vehicle (USV) equipped with a controlled electric dipole source, multiple receiver electrode pairs, and a 3-axes magnetometer assembly, which transmits electromagnetic energy and measures electric and magnetic fields to create a conductivity structure of buried objects using the Synthetic Aperture method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive magnetometer and gradiometer sensors are used to detect magnetized metal objects, then detection capability is provided, but the survey process is time consuming
Solution Approach 1:
The patent replaces passive magnetometer sensors with active CSEM electromagnetic sources that transmit electromagnetic signals through the seabed. This substitution enables faster survey speeds while maintaining detection capability for buried conductive objects, as the active EM method can detect objects at greater depths and covers larger areas more efficiently than passive magnetic sensing.
Solution Approach 2:
The patent changes the detection parameter from magnetic field measurements (passive) to electromagnetic field measurements (active). By using controlled source electromagnetic methods with adjustable frequency and amplitude, the system achieves both fast surveying and reliable detection of buried objects, resolving the contradiction between survey speed and detection reliability.
2Reliability
If CSEM method with horizontal electric dipole source and vertical electrode receiver pair is used, then detection of buried metal objects is achieved, but the system complexity increases
Solution Approach 1:
The patent makes the AUV platform multi-functional by integrating the CSEM electromagnetic source, vertical receiver electrode pairs, and 3-axes magnetometer assembly into a single autonomous vehicle. This universal platform can perform both electromagnetic detection and navigation functions, reducing overall system complexity while maintaining reliable buried object detection capability.
Solution Approach 2:
The patent combines multiple detection functions (electromagnetic sensing and magnetic sensing) into a single integrated AUV platform. By merging the horizontal electric dipole source, vertical receiver electrodes, and magnetometer assembly into one autonomous vehicle, the system reduces operational complexity compared to using separate dedicated systems for each detection method.
3Measurement precision
If three or more receiver antennas are provided to determine object location, then location accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent uses dynamic positioning of the AUV to achieve location accuracy without requiring multiple fixed receiver antennas. By moving the single receiver electrode pair through controlled trajectories and using the 3-axes magnetometer for orientation, the system achieves the location precision that would otherwise require complex multi-antenna arrays, thereby reducing device complexity.
Solution Approach 2:
The patent introduces the 3-axes magnetometer assembly as an intermediary that provides orientation and position information without being part of the electromagnetic detection array. This intermediary sensor enables the system to achieve location accuracy using a single receiver electrode pair, avoiding the complexity of multiple antennas while maintaining measurement precision.
4Measurement precision
If higher frequencies are used for electromagnetic signal transmission, then signal propagation distance is reduced, but detection resolution improves
Solution Approach 1:
The patent uses periodic electromagnetic signal transmission at optimized frequencies to achieve both good resolution and adequate propagation distance. By using pulsed or modulated electromagnetic signals rather than continuous high-frequency waves, the system can transmit signals over sufficient distances while maintaining the resolution benefits of higher frequencies through the periodic nature of the signal transmission.
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 detection sensitivity, allows for a sparser survey line configuration, and increases the height of the detection system above the seafloor while maintaining signal-to-noise ratio, thereby improving the efficiency and accuracy of buried object detection.
Implementation Method 1
A CSEM method for detecting and locating buried metal objects was developed in year 2000 at the Swedish Defence Research Agency (FOI). The method consisted in a horizontal electric dipole source in combination with a vertical electrode receiver pair in the middle of the source.
Implementation Method 2
The receiver pair is configured to measure electric field
Implementation Method 3
the 3-axes magnetometer assembly is configured to measure magnetic field
Implementation Method 4
The mainstream approach to the interpretation of towed streamer electromagnetic (EM) data is based on 2.5-D and/or 3-D inversions of the observed data into the resistivity models of the subsurface formations.
Data Source
AI summary
The disclosure relates to a system for detection and delineation of an object that is at least partly buried in seabed, the system comprising: a marine vehicle (1,10); a controlled electric dipole source (3) mounted on the marine vehicle; a first receiver electrode pair (4) comprising vertical receiver electrodes (4a, 4b) mounted on the marine vehicle, the vertical receiver electrodes (4a4b) separated from one another in the vertical direction of the AUV (1); a 3 axes magnetometer assembly; wherein the receiver pair (4) is configured to measure electric field and the 3-axes magnetometer assembly is configured to measure magnetic field. The disclosure further relates to a method of detection and delineation of an object that is at least partly buried in seabed.