Magnetic Target Positioning Using Compass Vector Intersection
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Solution Overview
Problem
Magnetic target positioning systems face errors due to weak magnetic fields or distant sensor placements, leading to inaccurate positioning of hidden features behind non-magnetic walls, as the difference in sensed field strength is not always proportional to the distance.
Innovation Solution
A system comprising a magnetic target and an array of three-axis digital magnetic compasses that computes direction vectors and determines the position of the magnetic target by finding intersection points in the global X-Y plane, using these vectors to derive an offset vector without relying on absolute magnetic strength, thereby improving positioning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If absolute field strength is used as measurement, then positioning can be performed, but positioning accuracy deteriorates when magnetic field is weak or sensors are distant
Solution Approach 1:
The patent changes the measurement parameter from absolute magnetic field strength to magnetic field direction (azimuth and elevation angles). This transformation allows the system to maintain reliable measurements even when the magnetic field is weak or sensors are distant, as directional information remains detectable while absolute strength becomes unreliable.
Solution Approach 2:
The patent introduces direction vectors as an intermediary between the magnetic target and the positioning calculation. Instead of directly using field strength differences, the system computes azimuth and elevation angles to define direction vectors, which then intersect to determine target position. This intermediary approach decouples positioning accuracy from field strength magnitude.
2Measurement precision
If difference in field strength is used for triangulation, then position can be inferred, but positioning accuracy deteriorates due to weak field differences
Solution Approach 1:
The patent transforms the measurement parameter from field strength (magnitude) to field direction (angular orientation). By measuring azimuth and elevation angles instead of field strength differences, the system preserves critical positional information while avoiding the loss of information that occurs when field differences become too weak to measure accurately.
3Area of stationary object
If sensors are placed distant from magnetic target, then scanning coverage increases, but positioning accuracy deteriorates
Solution Approach 1:
The patent changes what is being measured from field strength (which diminishes with distance) to field direction (which remains detectable at distance). This allows sensors to be positioned farther from the magnetic target, expanding scanning coverage while maintaining positioning accuracy through angular measurements rather than magnitude measurements.
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 method enhances the accuracy of magnetic target positioning by eliminating reliance on absolute field strength, reducing errors caused by weak fields or distant sensors, and allows for precise determination of the magnetic target's position and depth, facilitating accurate robotic operations like drilling through non-magnetic walls.
Implementation Method 1
A magnetic target and sensor array may be used to locate a hidden feature behind a non-magnetic wall. The magnetic target is placed at the feature behind the wall, and the sensor array is scanned over a front surface of the wall. Flux lines from the magnetic target are sensed by the sensor array.
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
An apparatus (110) comprises a magnetic target (120) for generating a magnetic field that is uniform and concentric about a central axis of the target (120); an array (130) of three-axis digital magnetic compasses for sensing the magnetic field; and a processor (140) for finding intersection points of vectors from the compasses (210) to the target (120). The vectors lie in a global X-Y plane that is normal to the central axis. Each vector indicates a direction of sensed magnetic field from one of the compasses (210) to the magnetic target (120).