OCCUPANCY DETECTING METHOD AND SYSTEM

• US 20090121854A1
• Filed: 11/09/2007
• Published: 05/14/2009
• Est. Priority Date: 11/09/2007
• Status: Active Grant

• Current Assignee: Emfit Oy
• Original Assignee: Emfit Oy
• Inventors: Virtanen, Tomi, Raisanen, Heikki
• Granted Patent: US 7,808,395 B2
• Time in Patent Office: Days
• US Class Current: 340/438
• CPC Class Codes: B60N 2/002 Seats provided with an occupancy detection means mounted therein or thereon detection means responsive to presence or absence of children B60N2/266
• CPC Class Codes: B60R 21/01516 using force or pressure sensing means
• CPC Class Codes: B60R 21/01526 using piezoelectric elements
• CPC Class Codes: B60R 21/01532 using electric or capacitive field sensors

Abstract

A method of and a system for detecting a person occupying a vehicle seat or a corresponding underlay whereby the underlay is provided with a single dynamic sensor and whereby the measurement signal is compared with a reference signal in comparing means, wherein the system comprises first measuring means for measuring a first measurement signal in a first frequency band representing a signal for human presence, and second measuring means for measuring the reference signal as a second measurement signal in a second frequency band representing a signal for background noise, comparing means for indicating an occupancy, wherein the signal strength in the first measurement signal in the first frequency band of human presence signal domination is compared to the signal strength in the reference signal in the second frequency band where essentially only background noise exists.

Claims

1. A method of detecting a person occupying a vehicle seat or a corresponding underlay whereby the underlay is provided with a single dynamic sensor and whereby the measurement signal is compared with a reference signal in comparing means,

characterized in that

in the method

the measurement signal is a first measurement signal measured in a first frequency band representing a signal for human presence, and

the reference signal is a second measurement signal measured in a second frequency band representing a signal for background noise, and

in order to get an indication of an occupancy the signal strength in the first measurement signal in the first frequency band of human presence signal domination is compared to the signal strength in the reference signal in the second frequency band where essentially only background noise exists.

2. The method as defined in claim 1,

characterized in that

the signal strength in the frequency band of human presence signal domination is compared ratiometrically to another frequency band signal.

3. The method as defined in claim 1,

characterized in that

the signal strength in the frequency band of human presence signal domination is compared to another frequency band signal strength by means of spectral content analysis.

4. The method as defined in claim 1,

characterized in that

the frequency range where human presence signal is at strongest is 2 to 20 Hz, preferably 2 to 18 Hz, and

the frequency range where the background noise dominates is 30 to 100 Hz, preferably 30 to 80 Hz.

5. A system for detecting a person occupying a vehicle seat or a corresponding underlay whereby the underlay is provided with a single dynamic sensor and whereby the measurement signal is compared with a reference signal in comparing means,

characterized in that

the system comprises

first measuring means for measuring a first measurement signal in a first frequency band representing a signal for human presence, and

second measuring means for measuring the reference signal as a second measurement signal in a second frequency band representing a signal for background noise,

comparing means for indicating an occupancy, wherein the signal strength in the first measurement signal in the first frequency band of human presence signal domination is compared to the signal strength in the reference signal in the second frequency band where essentially only background noise exists.

6. The system as defined in claim 5,

characterized in that

the system comprises amplifying and coupling means whereby sensor signal from the sensor is first amplified and this amplified signal is divided into two paths both being passed to the input (11) of the signal detection analysis.

7. The system as defined in claim 5,

characterized in that

the system comprises spectral analysis means whereby the signal strength in the frequency band of human presence signal domination is compared to another frequency band signal strength by means of spectral content analysis.

8. The system as defined in claim 5,

characterized in that the system comprises two band-pass filters arranged to the two signal paths, the two band-pass filters having

the frequency range where human presence signal is at strongest is 2 to 20 Hz, preferably 2 to 18 Hz, and

the frequency range where the background noise dominates is 30 to 100 Hz, preferably 30 to 80 Hz.

9. The system as defined in claim 8,

characterized in that it comprises power meter means so that each path is metered for RMS power individually.

10. The system as defined in claim 5,

characterized in that the relative power is generated by dividing these two power levels measurements, whereby this relative power value indicates a person'"'"'s presence/absence.