In-Vehicle CO2 Detection for Parked Occupant Abnormality Sensing
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Solution Overview
Problem
Existing methods for detecting the presence of an organism in a vehicle using CO2 concentration require presetting threshold values, which is time-consuming due to individual differences and the need for long-term measurements, especially for children or babies. Additionally, CO2 concentration changes are influenced by vehicle airtightness, making accurate detection challenging.
Innovation Solution
An in-vehicle abnormality detection device that includes a CO2 concentration sensor, a parked state detection unit, a time constant storage unit, a change rate estimation unit, a carbon dioxide concentration estimation unit, and an abnormality determination unit. This device estimates the CO2 concentration change rate and carbon dioxide concentration at specific times based on sensor readings and stored time constants, allowing for accurate detection of organisms by comparing these values with predetermined threshold values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CO2 concentration threshold values are preset by actual measurement to account for individual differences, then detection accuracy is improved, but the time required for measurement and threshold setting increases significantly
Solution Approach 1:
The patent performs preliminary measurements of CO2 concentration at multiple time points when the vehicle is parked and no one is inside, before actual use. These preliminary measurements are used to calculate the baseline change rate and establish threshold values in advance, so that when someone enters the vehicle, detection can immediately use pre-established criteria rather than requiring lengthy new measurements
Solution Approach 2:
The patent changes the parameter being measured from absolute CO2 concentration to the rate of change of CO2 concentration over time. By measuring how quickly CO2 concentration increases rather than just the absolute value, the system can detect presence more rapidly and establish thresholds based on change rates observed during preliminary parked-state measurements, reducing the time needed for accurate detection
2Measurement precision
If CO2 concentration measurements are conducted over long hours to account for vehicle airtightness deterioration, then detection accuracy is improved, but the complexity and difficulty of measurement increases
Solution Approach 1:
The system performs preliminary measurements during the parked state (when no one is in the vehicle) to establish baseline CO2 concentration levels and change rates. These preliminary measurements capture the effects of vehicle airtightness and environmental factors without requiring long-term continuous monitoring during actual use, simplifying the measurement process while maintaining accuracy
Solution Approach 2:
The system uses feedback from preliminary parked-state measurements to adjust and establish appropriate threshold values for the change rate of CO2 concentration. By continuously monitoring and comparing actual CO2 change rates against these established thresholds, the system adapts to variations in vehicle airtightness without requiring complex reconfiguration or long-term measurement protocols
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 device enables more accurate and efficient detection of organisms in vehicles, reducing the need for lengthy measurements and accounting for individual differences and changes in vehicle airtightness.
Implementation Method 1
a CO2 concentration sensor configured to detect in-vehicle carbon dioxide concentration of the vehicle
Data Source
AI summary
A change rate of in-vehicle carbon dioxide concentration at an optional time point when the vehicle is in a parked state is estimated on the basis of detection signals of a CO2 concentration sensor at two different time points when in the parked state; and on the basis of a detection signal of the CO2 concentration sensor at the optional time point, a preset time constant of concentration change of the in-vehicle carbon dioxide concentration, and the estimated change rate, the in-vehicle carbon dioxide concentration at a time point when a predetermined time according to the time constant has elapsed since the optional time point is estimated (steps S4 to S7). A detection target organism is determined to be present in the vehicle when the estimated in-vehicle carbon dioxide concentration is equal to or more than a threshold value set according to the detection target organism (steps S8 and S9).