Motion Tracking Sensor Placement Detection Without Magnetometers

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Solution Overview

Problem

Existing motion tracking systems that rely on sensors attached to a person face inaccuracies due to measurement errors and incorrect sensor placement, particularly when magnetometers are used for calibration.

Innovation Solution

A method for adjusting the operation of a motion tracking system using a computing apparatus and sensors with gyroscopes and accelerometers, which aligns and places the sensors on a person based on predetermined sensor arrangements, determining correct placement without magnetometer measurements, and adjusting the system's operation accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If magnetometers are used for calibration and motion tracking, then the system can provide heading information, but magnetic disturbances and measurement variations over time result in erroneous motion tracking

Engineering Contradiction:

Improveheading measurement accuracyVSAvoidmotion tracking accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent removes magnetometers from the sensor suite entirely, extracting only the necessary sensing functions (acceleration and rotation) that can be performed without magnetic field measurements. This eliminates the source of magnetic disturbance errors while maintaining core motion tracking capabilities through alternative methods.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the magnetic field-based heading measurement system with a mechanical/inertial-based system using gyroscopes and accelerometers. By substituting the magnetic sensing mechanism with inertial sensing, the system achieves heading information without susceptibility to magnetic disturbances.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If sensors are attached to a person for motion tracking, then the system can capture body motion, but incorrect sensor placement and orientation lead to measurement errors

Engineering Contradiction:

Improvemotion tracking capabilityVSAvoidsensor measurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent implements preliminary calibration procedures where the system guides users through specific placement and orientation steps before actual motion tracking begins. By performing these preparatory actions (correct sensor attachment and initial calibration), the system ensures accurate measurements during subsequent use without requiring complex real-time corrections.

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If magnetometer measurements are used for calibration, then the system can establish initial orientations, but measurement variations over time result in calibration degradation

Engineering Contradiction:

Improvecalibration processVSAvoidcalibration validity period

Core Design Contradiction:

Ease of operationVSDuration of action of stationary object

Solution Approach 1:

The patent performs comprehensive calibration procedures in advance, establishing accurate initial orientations and sensor relationships before use. By investing time in thorough preliminary calibration without relying on magnetometers, the system achieves calibration that remains valid for longer periods without degradation from magnetic field variations.

Inventive Principle:

Principle #10Preliminary 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

This approach enables accurate motion tracking by ensuring correct sensor placement and reducing measurement errors, thereby improving the system's accuracy and reliability without relying on magnetometer measurements.

Implementation Method 1

each sensor comprising a gyroscope and an accelerometer

Methodology Applied

Scientific EffectGyroscope: Gyroscope

Implementation Method 2

each sensor comprising a gyroscope and an accelerometer

Methodology Applied

Scientific EffectAccelerometer: Accelerometer

Data Source

PatentUS12318190B2Magnetometerless detection of incorrect attachment and calibration of motion tracking system

Publication Date: 2025.06.03 SWORD HEALTH SA

AI summary

A method for adjusting operation of a motion tracking system includes a computing apparatus and sensors, each sensor having a gyroscope and an accelerometer. The method includes the steps of aligning the sensors; providing, each sensor to the computing apparatus, a first orientation when the sensors are aligned, the first orientation having a first heading; placing the sensors on a person; and providing, each sensor to the computing apparatus, a second orientation when the sensors are placed on the person, the second orientation having a second heading. The method further includes digitally determining, the computing apparatus, whether the sensors are placed on the person according to a predetermined sensor arrangement based on both the first and second headings of each sensor; and adjusting, the computing apparatus, the operation of the motion tracking system based on the determination. Also, a system for tracking motion of a person.