Wearable Audio Device Magnetometer Nulling Magnet Interference

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Solution Overview

Problem

Wearable audio devices, such as earbuds, face interference from strong magnetic fields generated by their own magnets, which overwhelm the magnetometer and prevent it from accurately detecting the Earth's magnetic field, essential for orientation tracking.

Innovation Solution

Incorporating a nulling magnet that produces a magnetic field aligned with the transducer magnet and magnetometer axes to reduce the influence of the transducer magnetic field on the magnetometer, ensuring it operates within its linear range by partially or fully canceling the stray magnetic fields.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the magnetometer is positioned close to the transducer magnet to reduce device size, then the wearable audio device can be made smaller, but the strong magnetic field from the transducer magnet overwhelms the magnetometer and prevents it from detecting the Earth's magnetic field

Engineering Contradiction:

Improvedevice sizeVSAvoidmagnetic field detection accuracy

Core Design Contradiction:

Volume of moving objectVSMeasurement precision

Solution Approach 1:

A nulling magnet is introduced as an intermediary component between the transducer magnet and the magnetometer. This nulling magnet generates a magnetic field that opposes and cancels the stray magnetic field from the transducer magnet at the magnetometer's location, creating a null point where the Earth's magnetic field can be detected without interference. The nulling magnet thus mediates the interaction between the transducer magnet and magnetometer, enabling both close positioning and accurate detection.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the magnetometer is positioned close to the transducer magnet, then device size is reduced, but the strong magnetic field from the transducer magnet overwhelms the magnetometer

Engineering Contradiction:

Improvedevice structureVSAvoidmagnetic field interference

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The strong magnetic field from the transducer magnet, which initially appears as a harmful interference, is converted into a beneficial effect. By positioning the nulling magnet to generate an opposing magnetic field, the system creates a controlled null point where the transducer's magnetic field is canceled. This allows the magnetometer to detect the Earth's magnetic field even in close proximity to the transducer magnet, transforming the harmful strong field into a useful tool for achieving field cancellation.

Inventive Principle:

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

3Measurement precision

If a nulling magnet is added to cancel the transducer magnetic field, then magnetic field detection accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvemagnetic field detection accuracyVSAvoiddevice structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The nulling magnet is integrated into the existing device structure, merging its function with the housing or mounting structure of the transducer magnet. This consolidation approach allows the nulling magnet to be positioned precisely where needed without adding separate mounting mechanisms or complex assembly procedures. The merging of functions reduces the overall device complexity despite adding the nulling capability.

Inventive Principle:

Principle #5Merging (Combining)

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 configuration allows the magnetometer to accurately detect the Earth's magnetic field, enhancing the device's ability to track head orientation without being overwhelmed by stray magnetic fields, thereby improving the device's operational accuracy.

Implementation Method 1

a magnetic field sensor that is constructed and arranged to sense the Earth's magnetic field, a first magnet that produces a first magnetic field, and a nulling magnet that produces a nulling magnetic field

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Implementation Method 2

the nulling magnet is configured to reduce an influence of the first magnetic field on the magnetic field sensor

Methodology Applied

Scientific EffectMagnetic field cancellation: Magnetic Field

Data Source

PatentUS11061081B2Wearable audio device

Publication Date: 2021.07.13 BOSE CORP

AI summary

A wearable audio device with a magnetic field sensor that is constructed and arranged to sense the Earth's magnetic field. A magnet in the earphone, for example the magnet of the electro-acoustic transducer, produces a first magnetic field having a first magnetic field strength. A nulling magnet produces a nulling magnetic field along at least a first nulling magnet axis. The nulling magnet is configured to reduce an influence of the first magnetic field on the magnetic field sensor. The first nulling magnet axis, the first magnet axis, and the first sense axis are aligned.