Alertness Device Using RrMSSD for Accurate Respiratory Monitoring
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Solution Overview
Problem
Existing alertness determination technologies face challenges such as noise interference affecting respiration signal accuracy, the need for multiple sensors increasing costs, and reliance on standard deviation of respiratory intervals which are sensitive to average values, leading to decreased accuracy in determining alertness.
Innovation Solution
An alertness device using a resistive pressure-sensitive sensor in a vehicle seat to measure respiratory intervals and calculate the Respiration root Mean Square Successive Difference (RrMSSD) with a constant β, determining low alertness based on increased values, and incorporating an alarm system to maintain occupant alertness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the standard deviation of respiratory interval is used as the alertness determination indicator, then the alertness state can be determined based on respiratory variations, but the determination accuracy decreases because the standard deviation largely depends on the average value area and cannot obtain instantaneous variations
Solution Approach 1:
The patent changes the determination indicator from standard deviation of respiratory interval to RrMSSD (Respiration root Mean Square Successive Difference). This parameter change enables accurate capture of instantaneous variations in respiratory rhythm while determining alertness state, resolving the contradiction between using respiratory variations for alertness determination and maintaining determination accuracy.
2Reliability
If multiple sensors (heartbeat sensor and respiration sensor) are used to detect alertness, then comprehensive physiological parameters can be obtained, but manufacturing costs increase
Solution Approach 1:
The patent makes the respiration sensor perform multiple functions: it detects both respiratory parameters and heartbeat parameters. By analyzing respiratory intervals, the system can determine both respiration rate and heartbeat rate, eliminating the need for separate heartbeat and respiration sensors while maintaining comprehensive physiological monitoring for reliable alertness determination.
Solution Approach 2:
The respiration sensor serves itself by extracting multiple types of physiological information (respiratory rate, heartbeat rate) from a single measurement source. The respiratory signal contains embedded information about both respiration and heartbeat, allowing the sensor to provide multiple functions without additional hardware.
3Measurement precision
If respiration signal is used for alertness determination in a vehicle environment, then respiratory variations can be detected, but the detection accuracy decreases due to vibrational noises of vehicle body disturbing the respiration signal
Solution Approach 1:
The patent converts the harmful effect of vehicle vibrations into a beneficial filtering mechanism. By analyzing the temporal patterns and characteristics of respiratory intervals, the system distinguishes between genuine respiratory variations (which occur at physiological timescales) and vibration-induced noise (which occurs at mechanical frequencies). The RrMSSD calculation method inherently filters out high-frequency vibration noise while preserving low-frequency respiratory variations, turning the noisy environment into a condition where physiological signals can be reliably extracted.
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
The solution provides accurate and reliable alertness determination by enhancing instantaneous variation calculation and reducing manufacturing costs, effectively maintaining occupant alertness through precise monitoring and alerting mechanisms.
Implementation Method 1
a respiration sensor 20 for obtaining a respiration signal
Data Source
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AI summary
An alertness device with a high accuracy for determining alertness, a seat equipped with the alertness device, and a method for determining alertness are provided. The alertness device includes: a respiration sensor obtaining respiratory data of a person; a calculation unit calculating the respiratory data, a waveform generation unit generating an RI waveform which is transition in a predetermined time period of a respiratory interval (RI) which is an interval for one respiration; and a determination unit determining a state of alertness of the person on the basis of the respiratory data. The calculation unit calculates an average value of the RI and RrMSSDn in a predetermined time period. In a case where an average value of the subsequent RI is greater than an average value of the RI directly previous to the subsequent RI and in a case where the RrMSSDn of the subsequent RI is greater than a value which is obtained by multiplying the RrMSSDn of the previous RI by a constant β, the determination unit determines on the basis of values calculated by the calculation unit that the person is in a state of low alertness.