Metal Object Detection via Orthogonal Magnetic Field Gradients
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Solution Overview
Problem
Conventional metal detectors struggle to accurately locate, classify, and identify metal objects in three dimensions within a surveillance volume, especially when objects are not in favorable positions or are non-ferromagnetic, and they cannot simultaneously detect multiple objects effectively.
Innovation Solution
A metal object detecting apparatus that generates a time-varying primary magnetic field with orthogonal components throughout the surveillance volume, allowing for the measurement of secondary magnetic fields and the application of a minimization algorithm to determine the object's track and magnetic moment, which are then used to derive a unique magnetic signature independent of orientation and position, enabling classification and identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional metal detectors use simple threshold comparison to detect metal objects, then the device complexity is low, but the measurement precision and ability to classify/identify objects is insufficient
Solution Approach 1:
The patent transitions from simple threshold-based detection to three-dimensional localization by measuring magnetic field gradients in multiple spatial dimensions. The system uses an array of sensors to capture gradient components (dBx/dx, dBx/dy, dBx/dz, dBv/dy, dBv/dz) and applies inversion algorithms to compute precise object position (x, y, z) and orientation, adding spatial dimensionality to the detection process.
Solution Approach 2:
The patent changes the detection parameter from simple magnetic field magnitude comparison to measurement of magnetic field gradients. By detecting spatial derivatives of the magnetic field (gradients) rather than just field strength, the system gains the ability to determine object position, orientation, and magnetic signature, significantly improving measurement precision.
2Loss of information
If conventional metal detectors provide only presence/absence indication, then the ease of operation is high, but the loss of information about object location and classification is significant
Solution Approach 1:
The patent introduces an inversion algorithm as an intermediary processing step that transforms measured magnetic field gradients into meaningful object parameters (position, orientation, magnetic signature). This computational intermediary bridges the gap between raw sensor data and actionable intelligence, providing comprehensive object information while maintaining automated operation.
Solution Approach 2:
The patent replaces manual search procedures with an automated computational system. Instead of requiring operators to physically search for objects after detection, the system uses inversion algorithms to automatically compute object location and characteristics from magnetic field measurements, substituting mechanical search operations with computational analysis.
3Productivity
If security metal detectors require thorough manual search upon detection, then the measurement precision of object location can be improved, but the loss of time and productivity decreases
Solution Approach 1:
The patent performs preliminary localization and characterization of metal objects during the initial detection phase. By computing object position, orientation, and magnetic signature from magnetic field gradient measurements before any manual intervention, the system prepares complete object information in advance, enabling rapid response without subsequent manual search.
Solution Approach 2:
The system provides immediate feedback about object location and characteristics through the inversion algorithm, which processes magnetic field gradient measurements to generate real-time information about object position (x, y, z) and magnetic signature. This feedback mechanism eliminates the need for manual search by providing operators with precise location data instantly.
4Reliability
If conventional detectors cannot discriminate between threat and non-threat items, then the device complexity is low, but the reliability of security detection is insufficient
Solution Approach 1:
The patent makes the detection system multi-functional by enabling it to not only detect the presence of metal objects but also to classify and identify them. The same magnetic field gradient measurement system that locates objects also determines their magnetic signatures, which serve as identifiers for distinguishing threat items from non-threat items, adding classification functionality to the detection system.
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 allows for precise three-dimensional location and classification/identification of metal objects, including non-ferromagnetic ones, and the ability to detect multiple objects simultaneously, reducing nuisance alarms and enhancing security screening efficiency.
Implementation Method 1
transmitter means for generating a time varying primary magnetic field within a surveillance volume
Implementation Method 2
measure secondary magnetic fields arising from eddy currents induced in any metal object within a zone of influence of the primary magnetic field
Data Source
AI summary
A metal object detecting apparatus comprising, a transmitter for generating a primary magnetic field having a resultant magnetic field direction which varies along any substantially linear path through a surveillance volume such that at three locations along said path the resultant magnetic field points in three mutually substantially orthogonal directions; a detector for measuring a secondary magnetic field at a plurality of positions as a function of time due to the presence of a metal object within the surveillance volume as it passes a plurality of measurement points there-through; and a processor for determining from the measured secondary magnetic fields a track through the surveillance volume comprising a plurality of locations of the metal object and a magnetic moment thereof at each location, the processor being adapted in use to derive there-from a magnetic signature that is characteristic of the metal object and independent of the orientation and track of the metal object.