Accelerometer Orientation Detection Using Step Frequency Analysis

Solution Overview

Problem

Existing techniques for determining the lateral component of acceleration using a three-axis accelerometer are ineffective at lower walking speeds, as they rely on distinguishing between forward and lateral components based on energy levels, which become similar at slower speeds, making it difficult to accurately identify the lateral component without additional sensors like gyroscopes or magnetometers.

Innovation Solution

A method that processes acceleration measurements to determine the step frequency and identifies the lateral component as the component with a high response at half the step frequency, using techniques such as transforming to the frequency domain or minimizing autocorrelation to accurately determine the lateral component without the need for additional sensors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If additional sensors like gyroscopes or magnetometers are used to determine accelerometer orientation, then measurement precision of lateral component is improved, but use of energy increases and device complexity increases

Engineering Contradiction:

Improvelateral component identification accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The accelerometer determines its own orientation by analyzing its measurement data, specifically identifying the lateral component through frequency analysis of the acceleration signal. The system uses the constant gravity acceleration to establish a reference frame and processes the acceleration measurements to identify the lateral component without requiring additional sensors, thereby serving itself rather than requiring external assistance

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces the mechanical sensor-based orientation determination system (gyroscopes and magnetometers) with a signal processing approach that uses frequency domain analysis of the accelerometer data. By transforming the acceleration measurements to the frequency domain and identifying the lateral component through its characteristic frequency response at half the step frequency, the system substitutes physical sensors with computational methods

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If additional sensors like gyroscopes or magnetometers are used to determine accelerometer orientation, then measurement precision of lateral component is improved, but device complexity increases

Engineering Contradiction:

Improvelateral component identification accuracyVSAvoidsensor system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The accelerometer determines its own orientation by analyzing its measurement data, specifically identifying the lateral component through frequency analysis of the acceleration signal. The system uses the constant gravity acceleration to establish a reference frame and processes the acceleration measurements to identify the lateral component without requiring additional sensors, thereby serving itself rather than requiring external assistance

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces the mechanical sensor-based orientation determination system (gyroscopes and magnetometers) with a signal processing approach that uses frequency domain analysis of the accelerometer data. By transforming the acceleration measurements to the frequency domain and identifying the lateral component through its characteristic frequency response at half the step frequency, the system substitutes physical sensors with computational methods

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If energy-based distinction between forward and lateral components is used, then ease of operation is improved, but measurement precision deteriorates at lower walking speeds

Engineering Contradiction:

Improvecomponent identification simplicityVSAvoidlateral component identification accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent changes the parameter used for component identification from energy magnitude to frequency characteristics. By analyzing the frequency domain representation of the acceleration signal and identifying the lateral component through its distinctive frequency response at half the step frequency, the system overcomes the limitation of energy-based methods that fail at lower walking speeds where forward and lateral component energies become similar

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10188322B2Method and apparatus for determining the orientation of an accelerometer

Publication Date: 2019.01.29 KONINKLIJKE PHILIPS NV

AI summary

There is provided a method of determining the orientation of an accelerometer that is being carried or worn by a user, the method comprising measuring acceleration using the accelerometer as the user moves; processing the measured acceleration to determine a step frequency of the movements by the user; and processing the measured acceleration to identify a lateral component of acceleration as a component of acceleration having a high response at a frequency corresponding to half the step frequency.