Pressure Sensor Orientation for Fall Detection
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Solution Overview
Problem
Current air pressure sensors used for fall detection have limitations in accurately measuring small height changes due to orientation-dependent measurement errors, which can result in errors comparable to the height change being detected, making it difficult to reliably detect falls, especially from sitting or chair-related falls.
Innovation Solution
The method involves determining the preferred orientation of the pressure sensor relative to gravity to maximize the measurement error, which is then utilized to enhance the detectability of height changes by adjusting the sensor's orientation before and after a fall, thereby increasing the measurement value of height changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pressure sensor is used to measure height changes, then the sensitivity enables detection of height differences less than 1 meter, but the orientation-dependent measurement error of about 0.5 meter makes it difficult to reliably detect small height changes such as falls from a chair
Solution Approach 1:
The patent converts the harmful orientation-dependent measurement error into a beneficial signal by detecting changes in sensor orientation during a fall. When a fall occurs, the sensor orientation changes relative to gravity, causing a characteristic error pattern that distinguishes falls from normal movements. This transforms the previously problematic error source into a reliable fall detection mechanism.
Solution Approach 2:
The patent changes the measurement parameter from absolute height to height change combined with orientation change. By monitoring how the measurement error changes as the sensor orientation changes during a fall, the system can reliably detect falls even when the absolute height measurement precision is limited by orientation errors.
2Measurement precision
If the pressure sensor orientation is optimized for maximum height measurement, then the preferred orientation provides the largest height measurement value, but this creates maximum measurement error that obscures small height changes
Solution Approach 1:
The patent applies dynamics by not fixing the sensor orientation but rather exploiting the dynamic change in orientation that occurs during a fall. The system monitors how the measurement error dynamically changes as the sensor rotates during a fall event, using this temporal evolution of the error to detect falls rather than relying on static measurement precision.
Solution Approach 2:
The patent performs preliminary characterization of the sensor's orientation-dependent error behavior during normal use. By understanding the error patterns at different orientations beforehand, the system can distinguish normal orientation variations from the characteristic error patterns that occur during falls, enabling reliable fall detection despite the inherent measurement errors.
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 approach improves the reliability of fall detection by increasing the measurement value of height changes, allowing for the accurate detection of small changes, such as falls from a chair, by leveraging the orientation-dependent error in air pressure sensor measurements.
Implementation Method 1
Pressure sensors have been developed that can resolve pressure differences in the surrounding environment of around 1.5 Pascal (Pa). These sensors have a sensitivity enabling applications for determining differences in altitude of less than 1 meter from measurements of the air pressure.
Implementation Method 2
The orientation of the pressure sensor relative to the direction of gravity can cause a measurement error
Data Source
AI summary
A sensor unit (2) comprising a pressure sensor (9) is worn by a person. A fall of the person causes a height change as well an orientation change of the pressure sensor. To enlarge the detectability of the fall the air pressure is positioned such that in a pre-fall condition the contribution of an error to the sensor's measurement is maximal. This error is caused by gravity acting on the membrane of the sensor.