Body Motion Sensor Position Shift Detection
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Solution Overview
Problem
Existing methods for detecting the positional shift of a sensor attached to a human body during walking motions are inaccurate due to imbalances and muscle weakening associated with aging, making it difficult to reproducibly detect sensor position changes.
Innovation Solution
A detecting method that uses a computer to obtain body motion signals while a person walks with a predetermined stride, compares these signals to a reference-walk-waveform generated from an initially attached position, and determines if the sensor position has shifted by analyzing differences in waveforms related to stride, walk cycle, and maximum acceleration values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensor is attached to human body for motor function estimation, then motor function assessment can be performed, but sensor shifts from initially attached position due to belt loosening from body motion
Solution Approach 1:
The system performs preliminary calibration by storing the relationship between sensor output and body motion at the initial attached position before actual use. This preliminary action creates a reference baseline that enables later detection of any position shifts without requiring the sensor to remain perfectly fixed during subsequent operations.
Solution Approach 2:
The system continuously monitors sensor output during body motion and compares it against the stored reference waveform. When deviations exceed a threshold, the system detects position shift and can trigger re-calibration or correction, forming a closed-loop feedback mechanism that maintains measurement accuracy despite sensor movement.
2Measurement precision
If existing methods are used to detect sensor positional shift from walking motion, then position detection can be performed, but detection accuracy is insufficient due to aging-related imbalances and muscle weakening
Solution Approach 1:
The system changes the detection parameter from simple position coordinates to waveform pattern analysis. By comparing the temporal pattern of sensor output during walking against a reference waveform, the system can detect position shifts even when walking motion characteristics vary due to aging, thereby improving both precision and reliability.
Solution Approach 2:
The system creates a copy of the reference waveform pattern stored during calibration and compares it with subsequent sensor output patterns. This copying approach allows for robust comparison that is insensitive to variations in walking speed or gait characteristics, focusing instead on the characteristic pattern shape that indicates sensor position.
Data Source
AI summary
A detecting device obtains a first body motion signal from a body motion sensor while a person walks with a predetermined stride, the body motion sensor being attached to a body of the person and configured to detect a body motion of the person, obtains a reference-walk-waveform from a memory, the reference-walk-waveform being generated from a second body motion signal obtained from the body motion sensor while the person walks with the predetermined stride with the body motion sensor attached to an initially attached position, compares the obtained reference-walk-waveform with a waveform of the obtained first body motion signal to determine whether an attached position of the body motion sensor is shifted from the initially attached position, and outputs a determination result.