Electromagnetic Tracking Error Reduction via IMU Constraint Blending
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Solution Overview
Problem
Magnetic tracking systems face accuracy issues due to magnetic field distortion caused by distance attenuation, ferrous objects, and conducting surfaces that induce secondary magnetic fields, leading to errors in position and orientation determination.
Innovation Solution
A system and method that utilize a transmitter with source magnetic coils and a receiver with sensor magnetic coils, along with inertial measurement units, to detect errors in the magnetic field and apply correction factors to reduce distortion, blending signal matrices to determine an error-corrected position and orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic tracking systems are used to determine position and orientation, then tracking functionality is provided, but magnetic field distortion from ferrous objects and conducting surfaces causes errors in position and orientation determination
Solution Approach 1:
The system uses inertial measurement units to continuously monitor the position and orientation of the tracking device, providing feedback that is used to correct magnetic field distortion errors. The IMU data serves as a reference that is compared against magnetic field measurements, and correction factors are applied based on the detected discrepancies, creating a closed-loop feedback system that actively compensates for distortion.
Solution Approach 2:
The inertial measurement unit acts as an intermediary between the magnetic field sensors and the final position/orientation determination. The IMU provides an independent measurement channel that mediates the corrupted magnetic field data, allowing the system to separate true position changes from distortion-induced errors through sensor fusion algorithms.
2Measurement precision
If correction factors are applied multiple times to compensate for distortion, then tracking accuracy is improved, but system complexity increases
Solution Approach 1:
The system applies correction factors iteratively in multiple passes, performing more corrections than a single-step approach would provide. This partial action approach applies smaller, incremental corrections that accumulate to achieve higher accuracy without requiring a single complex correction algorithm, breaking down the correction process into manageable stages.
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
Significantly reduces magnetic tracking errors by up to 90% by using inertial measurement units to constrain and correct for distortion, improving the accuracy of position and orientation determination in electromagnetic tracking systems.
Implementation Method 1
a transmitter having a plurality of source magnetic coils configured to generate a magnetic field, and a receiver having a plurality of sensor magnetic coils configured to sense the magnetic field
Implementation Method 2
A processor is disclosed which utilizes data from the inertial measurement units to determine a constraint on the position and orientation of the receiver
Data Source
AI summary
A method and apparatus for reducing magnetic tracking error in the position and orientation determined in an electromagnetic tracking system is disclosed. In some embodiments, a corrected position and orientation is blended with an uncorrected position and orientation based upon the calculated probability of each. To determine a corrected position and orientation, data from an IMU in the receiver is used to obtain a constraint on the orientation. In other embodiments, the amount of detected error due to electromagnetic distortion is measured. Any error is first assumed to be from “floor distortion,” and a correction is applied. If the error is still deemed too great, a constraint is again obtained from IMU data. Using this constraint, another correction for the distortion is made. The solution from this correction may be blended with a standard solution and the solution from the floor distortion to arrive at a final solution.