Auto-Hemisphere Detection in Magnetic Tracking

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Solution Overview

Problem

Electromagnetic tracking systems face challenges in determining the correct hemisphere of a sensor relative to a magnetic source, leading to ambiguity and potential operational failures if incorrect hemisphere information is input, making it inconvenient and impractical for users.

Innovation Solution

A system and method that combines magnetic and non-magnetic tracking to automatically determine the correct hemisphere by seeding candidate position and orientation solutions in both hemispheres, using the magnetic tracker and non-magnetic device to track changes and identify divergence, thereby determining the correct hemisphere based on the lesser divergence.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If magnetic tracking is used to determine sensor position and orientation, then measurement rate and accuracy are improved, but hemisphere ambiguity causes operational reliability to deteriorate

Engineering Contradiction:

Improveposition and orientation measurement accuracyVSAvoidtracking system operational reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

A non-magnetic tracking device is introduced as an intermediary system to resolve the hemisphere ambiguity problem. The non-magnetic tracker provides independent position and orientation data that serves as a reference to determine which of the two magnetic hemisphere solutions is correct, thereby eliminating the reliability issue without compromising the magnetic tracking accuracy

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent combines magnetic tracking and non-magnetic tracking systems into a unified hybrid tracking system. By merging the high-accuracy magnetic field-based position and orientation measurements with the unambiguous non-magnetic tracking data, the system achieves both measurement precision and operational reliability

Inventive Principle:

Principle #5Merging (Combining)

2Device complexity

If manual hemisphere input is required, then system complexity is reduced, but ease of operation deteriorates

Engineering Contradiction:

Improvehemisphere determination system complexityVSAvoiduser convenience in hemisphere specification

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

The system performs automatic hemisphere determination through self-service mechanisms. The non-magnetic tracking device autonomously provides reference data, and the processor automatically compares magnetic and non-magnetic solutions to identify the correct hemisphere, eliminating the need for manual user input while maintaining system simplicity

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The non-magnetic tracking device is used in advance to establish reference position and orientation data before the magnetic tracking measurement is finalized. This preliminary action allows the system to pre-determine the correct hemisphere before processing the magnetic tracking results, improving ease of operation without adding complex post-processing steps

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If automatic hemisphere detection is implemented, then ease of operation is improved, but device complexity increases

Engineering Contradiction:

Improveautomated hemisphere determinationVSAvoiddual tracking system complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The non-magnetic tracking device serves multiple functions: it provides primary position and orientation tracking data, serves as a reference for resolving magnetic hemisphere ambiguity, and validates the magnetic tracking solutions. This multi-functionality reduces the need for separate dedicated hemisphere-detection hardware, thereby limiting the increase in overall system complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 eliminates the need for manual hemisphere input, reduces operational errors, and ensures accurate tracking by automatically selecting the correct hemisphere, enhancing the reliability and usability of electromagnetic tracking systems.

Implementation Method 1

an electromagnetic tracking system determines position and orientation (PnO) of a tracked object using measurements of a multi-dimensional magnetic field generated by the system

Methodology Applied

Scientific EffectElectromagnetic field generation and detection: Electromagnetic Induction

Implementation Method 2

a non-magnetic tracking device that is not subject to hemisphere ambiguity

Methodology Applied

Scientific EffectNon-magnetic tracking:

Data Source

PatentUS11675030B2Auto-hemisphere detection in a magnetic tracker

Publication Date: 2023.06.13 ALKEN INC DBA POLHEMUS

AI summary

An apparatus and method for determining position and orientation (PnO) of an object within an environment and for automatically determining a hemisphere of the object relative to a source location using an electromagnetic tracking system and a non-magnetic tracking device. The method involves seeding two candidate PnO solutions, one in each hemisphere, based on initial data from the magnetic tracker. Then, as the sensor moves within the tracking volume, both the magnetic tracker and the non-magnetic tracking device are used to track changes in each of the candidate PnO solutions and to determine a correct one of the candidate PnO solutions.