Leg-Mounted Angular Velocity Sensors for Direction Change Motion Detection
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Solution Overview
Problem
Conventional techniques fail to accurately extract feature amounts of direction change motion using sensors only on both legs, as sensors placed on the hands cannot detect individual step actions with high accuracy, especially when direction changes are made with small steps.
Innovation Solution
An information processing system employing angular velocity sensors on both legs to extract direction change features by identifying motion candidates, determining direction change sections, and extracting features such as rotation speed, duration, and asymmetry between legs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensors are placed on both legs only, then device complexity is reduced, but measurement precision of direction change motion features deteriorates
Solution Approach 1:
The patent segments the measurement task by placing sensors on both legs separately, then processing the data from each leg independently to extract motion candidates. This segmentation allows the system to maintain low device complexity while achieving accurate direction change detection through coordinated analysis of both legs' motion data.
Solution Approach 2:
The patent transitions from analyzing single-leg motion to analyzing the relationship between both legs' motion in a multi-dimensional space. By comparing motion candidates from both legs and identifying their temporal and spatial relationships, the system extracts direction change features that would be invisible to single-leg analysis, thereby improving measurement precision without adding upper body sensors.
2Ease of operation
If sensors are placed on the hand-held mobile terminal, then direction change detection is simplified, but measurement precision of individual step actions deteriorates
Solution Approach 1:
Instead of placing sensors on the hand-held terminal to detect direction changes, the patent inverts the approach by placing sensors on the legs and using leg motion data to infer direction changes. This inversion allows the system to capture individual step actions with high precision while still achieving direction change detection, effectively solving both requirements simultaneously.
3Measurement precision
If sensors on both legs are used with combined gait initiation technique, then measurement precision of direction change improves, but device complexity increases
Solution Approach 1:
The patent makes the leg-mounted sensors universal by designing them to perform multiple functions: detecting gait initiation, identifying motion candidates, and extracting direction change features. This multi-functionality allows the system to achieve high measurement precision for direction changes using only the leg sensors, eliminating the need for additional upper body sensors and thereby preventing device complexity from increasing.
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
Enables accurate extraction of direction change motion features using sensors on both legs, improving detection accuracy and identifying gait sections and transition gait phases.
Implementation Method 1
an angular velocity sensor that detects a rotation amount of the leg about an axis in a direction of gravity
Data Source
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AI summary
An information processing system (9) includes a sensor device (2) that is used for a left leg, a sensor device (3) that is used for a right leg, and an information processing apparatus (1) that processes data acquired by the sensor devices. The information processing apparatus includes a motion-candidate extracting unit (12) that extracts a point at which a motion of rotation of a leg about an axis in a direction of gravity occurs in the data acquired by the sensor devices, as a motion candidate of a direction change; a direction-change-motion determining unit (16) that determines a plurality of extracted motion candidates as a direction change motion when directions of the rotation are identical, and a motion candidate of the left leg and a motion candidate of the right leg alternately appear chronically successively, as a direction change motion; and a direction-change-feature extracting unit (17) that extracts a feature of the direction change motion that is determined by the direction-change-motion determining unit, by using the data acquired by the sensor devices, thereby enabled to extract a feature amount of a direction change motion highly accurately by using only sensors on both legs.