Wearable Magnetometer Motion Estimation via Magnetic Field Distortion

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Solution Overview

Problem

Current image data analysis techniques struggle to predict object motion in real-time without using image data, especially when the object is outside the camera's field of view.

Innovation Solution

The use of a wearable device equipped with magnetometers and other sensors to detect changes in local magnetic fields, allowing for the estimation of user actions and motion characteristics, even when ferromagnetic objects are outside the camera's view.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If image data analysis techniques are used to predict object motion, then motion prediction capability is provided, but real-time prediction is not achieved and the system cannot detect objects outside camera field of view

Engineering Contradiction:
Improvemotion prediction capabilityVSAvoidreal-time prediction delay
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces image data analysis (optical/mechanical system) with magnetometer-based detection (magnetic field system). Magnetometers can detect ferromagnetic objects and their motion in real-time without requiring camera field of view, enabling simultaneous real-time prediction and extended detection range.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces magnetic field distortion as an intermediary between the ferromagnetic object and the detection system. The magnetometer detects changes in magnetic field caused by ferromagnetic objects, translating physical motion into detectable signal changes for real-time analysis.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Loss of time

If magnetometers are used to detect ferromagnetic objects, then real-time detection and extended field of view are achieved, but device complexity increases

Engineering Contradiction:
Improvereal-time detection capabilityVSAvoidsensor system complexity
Core Design Contradiction:
Loss of timeVSDevice complexity

Solution Approach 1:

The patent makes the magnetometer system multi-functional by combining it with machine learning models that can classify various motions (e.g., bicep curls, shoulder presses, rows). The same magnetometer hardware serves multiple detection purposes, reducing the need for separate specialized sensors for each motion type.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent creates a virtual model of motion patterns through machine learning training. Instead of using complex hardware for each motion type, the system copies motion characteristics into a computational model that can recognize patterns from magnetometer data, simplifying the physical device while maintaining detection capability.

Inventive Principle:
Principle #26Copying

3Use of energy by moving object

If wearable devices with magnetometers are used for motion estimation, then power consumption is reduced for long-term use, but measurement precision may be affected

Engineering Contradiction:
Improvepower consumptionVSAvoidmotion estimation accuracy
Core Design Contradiction:
Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The patent implements periodic sampling of magnetometer data rather than continuous processing. The system samples magnetic field changes at intervals during exercise routines, reducing computational load and power consumption while maintaining sufficient measurement precision through strategic sampling points in the motion cycle.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The system uses the ferromagnetic objects themselves as part of the sensing mechanism. The objects being exercised with (weights, dumbbells) inherently distort the magnetic field, providing the measurement signal without requiring separate active sensors on the objects. This self-service approach reduces system complexity and power requirements.

Inventive Principle:
Principle #25Self-service

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 and real-time estimation of user motion and activity repetitions with minimal power consumption, making it suitable for long-term wear and use in various environments.

Implementation Method 1

detect change in a local magnetic field... detect the distortion of a local magnetic field as a ferromagnetic object moves in the vicinity

Methodology Applied
Scientific EffectMagnetic field distortion: Magnetic Field

Data Source

PatentUS20250108258A1Estimation of Motion Repetition using Local Magnetic Field Distortion
Publication Date: 2025.04.03 APPLE INC
  • US20250108258A1 patent drawing
  • US20250108258A1 patent drawing
  • US20250108258A1 patent drawing

AI summary

Predicting and counting repetitions of a physical activity includes capturing first sensor data, by a first magnetometer on a wearable device, a change in a magnetic field indicative of a ferromagnetic object moving in relation to the wearable device. One or more characteristics of a user motion are determined based on the first sensor data. A count of repetitions of the user motion are determined based on the one or more characteristics of the user motion, and a notification of the count of repetitions is generated.