Eddy Current Compensation in Magnetic Tracking

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Magnetic tracking systems are susceptible to performance degradation due to the presence of conductive objects, which induce eddy currents that lead to inaccurate position and orientation information.

Innovation Solution

A method for distortion compensation that involves determining undisturbed phases and amplitudes of position indication signals, calculating chi-squared values, and adjusting signals to account for eddy currents, using multiple frequencies and field generator coils to detect and compensate for conductive objects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If magnetic tracking systems operate in the presence of conductive objects, then the system can function in realistic environments, but eddy currents are induced that degrade position indication accuracy

Engineering Contradiction:

Improveenvironmental adaptabilityVSAvoidposition indication accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent measures the distorted signal characteristics (amplitude and phase at multiple frequencies) caused by eddy currents and uses these measurements to calculate compensation parameters. The harmful eddy current effects are converted into useful information for generating correction factors that restore measurement accuracy.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The system measures signal characteristics at multiple frequencies (fundamental and harmonic frequencies) and uses these frequency-dependent measurements to determine eddy current phase and amplitude. By analyzing parameter changes across different frequencies, the system can accurately characterize and compensate for conductive object interference.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If eddy current compensation is implemented, then position indication accuracy is improved, but system complexity increases due to multiple frequency measurements and calculations

Engineering Contradiction:

Improveposition indication accuracyVSAvoidsignal processing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system performs self-characterization by automatically measuring its own frequency response and eddy current effects in the actual operating environment. The compensation parameters are derived from the system's own measurements rather than requiring external calibration or complex pre-characterization procedures.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system uses measured signal characteristics (amplitude ratios and phase differences at multiple frequencies) as feedback to calculate compensation parameters. This feedback loop allows the system to adapt to varying conductive object configurations and maintain accuracy dynamically.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If multiple frequency measurements are performed for eddy current characterization, then compensation accuracy is improved, but measurement time increases

Engineering Contradiction:

Improveeddy current characterization accuracyVSAvoidcompensation calculation time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system uses periodic excitation signals at multiple frequencies (including fundamental and harmonic frequencies) to probe the system response. By using periodic actions at different frequencies, the system efficiently extracts eddy current characteristics without requiring lengthy measurement sequences.

Inventive Principle:

Principle #19Periodic action

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 real-time determination and compensation of eddy current phases and amplitudes, providing accurate position indications and increased sensitivity by monitoring changes in chi-squared values and signal ratios across different frequencies.

Implementation Method 1

The eddy currents induced within a conductive object can disturb the position indication of a sensor

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

The presence of conductive objects in the vicinity of the magnetic tracking system can degrade the performance of the system. The eddy currents induced within a conductive object

Methodology Applied

Scientific EffectEddy currents: Eddy Currents

Data Source

PatentUS7783441B2Eddy current detection and compensation

Publication Date: 2010.08.24 BANK OF MONTREAL

AI summary

A distortion compensation method includes determining an undisturbed phase for at least one of a first position indication signal and a second position indication signal. The method includes determining an undisturbed ratio that relates the amplitude of the first position indication signal at a first frequency to the amplitude of the second position indication signal at a second frequency. The method also includes determining a disturbed amplitude of the position indication signal and adjusting a position indication based on the disturbed amplitude and phase, the undisturbed amplitude ratio, and the undisturbed phase. The method further comprises determining a relationship between the eddy current phase of the first position indication signal and the second position indication signal.