Wrist Accelerometer Elbow Angle Calculation via 2D Plane Projection
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Solution Overview
Problem
Conventional methods require multiple sensors to measure and analyze the elbow bending angle during running or walking, which increases cost, weight, and processing complexity, and are inefficient in accurately evaluating arm swing and posture.
Innovation Solution
An electronic device with a processor that identifies cyclic changes in three-dimensional acceleration at the wrist, defines a two-dimensional plane for arm swing, detects motion centered at the shoulder, and calculates the elbow bending angle based on the line segment connecting the wrist and shoulder using a single acceleration sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors are used to measure elbow bending angle, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The single acceleration sensor mounted on the wrist performs multiple functions: detecting arm swing cyclic changes, determining elbow bending angle, and analyzing running/walking posture. This multi-functional approach eliminates the need for multiple dedicated sensors while maintaining comprehensive measurement capabilities.
Solution Approach 2:
The patent replaces direct mechanical angle measurement (which would require multiple sensors positioned at the elbow) with indirect mechanical inference. By measuring acceleration at the wrist and using kinematic relationships to calculate elbow angle, the system substitutes a simple single-point acceleration measurement for a complex multi-sensor angular measurement system.
2Measurement precision
If multiple sensors are deployed, then measurement precision is improved, but weight increases
Solution Approach 1:
A single acceleration sensor is designed to perform multiple measurement functions (arm swing detection, elbow angle calculation, posture analysis) that would traditionally require multiple specialized sensors, thereby significantly reducing the total weight of the wearable device.
3Measurement precision
If multiple sensors are used, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The system uses a single acceleration sensor to achieve multiple measurement objectives, reducing component count and assembly complexity. This approach lowers manufacturing costs while maintaining the precision needed for elbow angle detection and arm swing analysis through sophisticated signal processing algorithms.
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
Simplifies the measurement of elbow bending angle, allowing for more accurate evaluation of arm swing and posture with reduced device complexity and cost, enabling effective analysis of arm swing state during walking or running.
Implementation Method 1
measuring three-dimensional acceleration in which a cyclic change related to an arm swing of a user appears
Data Source
AI summary
An electronic device includes at least one processor that identifies a cyclic change related to an arm swing of a user from a three-dimensional acceleration measured by a measurer. The at least one processor defines a two-dimensional plane containing a plane of the arm swing of the user from the three-dimensional acceleration measured at a wrist of the user, detects the cyclic change as a motion on an arc centered at a shoulder of the user in the two-dimensional plane, obtains, from the three-dimensional acceleration, a direction of a line segment connecting the wrist and the shoulder, and obtains a bending angle of an elbow of the user based on the line segment.