Magnetic Tracking System with Geomagnetic Reference
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Solution Overview
Problem
Existing magnetic tracking systems can only track objects with respect to a reference system fixed to the sensors, not a motionless reference system, and have limitations in sampling speed, making them inadequate for tracking movable body parts like the head and eyes, especially in applications requiring high precision and speed.
Innovation Solution
A system using an array of magnetic field sensors and a data processing unit that calculates the position and orientation of a magnetic dipole source with respect to both the sensors and the geomagnetic field, allowing tracking relative to a fixed, independent reference system, and achieving sampling speeds of hundreds of samples per second without compromising precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic field sensors are used to track objects, then position and orientation can be detected, but the tracking is limited to a reference system fixed to the sensors and cannot reference a motionless external system
Solution Approach 1:
The patent introduces the geomagnetic field as an intermediary reference that is independent of both the tracked object and the sensor array. By detecting the orientation of the geomagnetic field vector at multiple sensor positions, the system establishes a motionless external reference frame, enabling tracking relative to the environment rather than just relative to the sensors themselves.
2Measurement precision
If iterative calculation procedures are used to determine dipole position, then measurement precision can be improved, but sampling speed decreases
Solution Approach 1:
The patent performs preliminary determination of the geomagnetic field orientation using a subset of sensors or initial measurements before the main tracking operation. This pre-established reference information is then reused in subsequent tracking calculations, reducing the computational burden of each sampling cycle while maintaining precision through the use of optimized algorithms for the remaining calculations.
3Ease of manufacture
If the geomagnetic field is present in the measurement environment, then tracking can be performed without costly shielding, but the geomagnetic field interferes with the local magnetic field measurements
Solution Approach 1:
The patent converts the harmful geomagnetic field interference into a beneficial reference signal. By deliberately measuring the geomagnetic field orientation at multiple positions and using it as an external reference frame, the system transforms what was previously considered noise or interference into a useful tool for establishing an absolute reference system, eliminating the need for expensive magnetic shielding while improving tracking capability.
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
Enables precise tracking of quickly moving body parts like eyeballs and tongue movements, overcoming previous limitations by accurately discriminating between local and geomagnetic field contributions, and eliminating the need for costly shielding from the geomagnetic field, while maintaining low power consumption and cost-effectiveness.
Implementation Method 1
an array of magnetic field sensors fixed at respective predetermined sensor positions on a support and configured to measure magnetic field data
Data Source
AI summary
A system (50) for tracking an object (1) comprises a magnetic field source (10) configured to be fixed to this object (1); a magnetometric data collection unit (20) that uses magnetic field sensors (22) fixed at predetermined positions on a support (23) to form an array (21), and that includes a sensor control unit (25) for controlling the magnetic field sensors (22); a data processing unit (30) configured to receive the magnetic field data from the sensor control unit (25) and to calculate from these data position coordinates of the magnetic field source (10) with respect to the array (21) forming a vector of such position coordinates which minimizes the distance between magnetic field values expected at the sensor positions (22) and magnetic field values collected by the collection unit (20), wherein the magnetic field source (10) is arranged to generate a local magnetic field (4), at the magnetic field sensors (22), of intensity set between 5 and 500 microtesla, so that the magnetic field sensors (22) detect both the local magnetic field (4) and the geomagnetic field (5), and wherein the data processing unit (30) is configured to recognize contributes of the local magnetic field (4) and of the geomagnetic field (5) in the magnetic field data, and is configured to determine location and of orientation coordinates of the magnetic field source (10) with respect to the array (21), as well as orientation coordinates of the array (21) with respect to the geomagnetic field (5). This way, an accurate tracking can be obtained of the displacements of the object (1) even if the array (21) is connected to a support that is movable with respect to an absolute reference system integral to the geomagnetic by fixing array to the subject's head.