Distortion-Immune Magnetic Position Tracking
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Solution Overview
Problem
Magnetic position tracking systems face inaccuracies due to distortions caused by metallic, paramagnetic, or ferromagnetic objects, which induce eddy currents and alter magnetic fields, leading to erroneous measurements.
Innovation Solution
The system employs multiple field generators and sensors to perform redundant field strength measurements, using a rotation-invariant coordinate correcting function to adjust measured field strengths and reduce distortion, and identifies and disregards distortion-contributing elements to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If magnetic field measurements are performed in the presence of metallic, paramagnetic or ferromagnetic objects, then position tracking can be performed in real-world environments, but measurement accuracy deteriorates due to field distortions and eddy currents
Solution Approach 1:
The system performs baseline measurements in the absence of field-distorting objects before actual tracking begins. These preliminary baseline phases are stored and later used to detect and correct distortions caused by metallic, paramagnetic or ferromagnetic objects during position tracking
Solution Approach 2:
The system continuously monitors phase shifts in magnetic field signals and uses this feedback to detect the presence of field-distorting objects. The detected phase shifts are fed back into the position calculation algorithm to compensate for measurement errors and maintain accuracy
2Measurement precision
If phase shift detection is used to identify field-distorting objects, then measurement accuracy can be maintained, but system complexity increases due to additional signal processing requirements
Solution Approach 1:
The system uses phase shift as an intermediary parameter to indirectly detect the presence of field-distorting objects. Instead of directly detecting the objects, the system measures the phase shift of magnetic field signals, which serves as a mediator that indicates distortion without requiring direct object detection
Solution Approach 2:
The system monitors changes in signal phase parameters to detect field distortions. By tracking phase shifts rather than absolute field strengths, the system can identify the presence of distorting objects and adjust measurements accordingly, maintaining accuracy through parameter-based detection
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 significantly enhances the accuracy of position and orientation calculations of tracked objects by exploiting redundant information and compensating for distortions, ensuring precise tracking even in the presence of field-distorting objects.
Implementation Method 1
magnetic fields generated by two or more field generators and sensed by a position sensor
Implementation Method 2
The distortion is sometimes caused by eddy currents that are induced in such objects by the system's magnetic field
Implementation Method 3
The magnetic fields are sensed by a position sensor associated with the object and converted to position signals
Data Source
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AI summary
A method for tracking a position of an object includes using a field sensor associated with the object to measure field strengths of magnetic fields generated by two or more field generators, wherein a measurement of at least one of the field strengths is subject to a distortion. Rotation-invariant location coordinates of the object are calculated responsively to the measured field strengths. Corrected location coordinates of the object are determined by applying to the rotation-invariant location coordinates a coordinate correcting function so as to adjust a relative contribution of each of the measured field strengths to the corrected location coordinates responsively to the distortion in the measured field strengths.