Vehicle occupant detection system and method using radar motion sensor

• US 20030201894A1
• Filed: 03/15/2002
• Published: 10/30/2003
• Est. Priority Date: 03/15/2002
• Status: Active Grant

• Current Assignee: Aptiv Technologies Limited (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Li, Songnian
• Granted Patent: US 6,753,780 B2
• Time in Patent Office: Days
• US Class Current: 340/573.1
• 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

Abstract

A motion sensing system and method for detecting an occupant in a vehicle with enhanced sensitivity to detect small movement, such as movement caused by heartbeat and breathing of an occupant. The system includes a radar motion sensor located in a compartment of the vehicle. The radar sensor transmits and receives signals within the compartment and generates sensed signals. The system has a controller for converting the sensed signals to a frequency domain. The controller further processes the frequency domain of sensed signals and determines the presence of movement of an occupant due to one of heartbeat and breathing of the occupant.

Claims

1. A motion detection system for detecting the presence of an occupant in a vehicle, said detection system comprising:

a radar motion sensor located in a compartment of a vehicle, said radar sensor transmitting and receiving radar signals within the compartment and generating sensed signals; and

a controller converting the sensed signals to a frequency domain, said controller further processing the frequency domain of sensed signals within a frequency range and determining the presence of movement of an occupant due to one of heartbeat and breathing.

2. The detection system as defined in claim 1, wherein the controller determines an average value of the sensed signals within the frequency range, said controller further comparing the average value to a threshold value to determine the presence of movement of an occupant due to one of heartbeat and breathing.

3. The detection system as defined in claim 2, wherein the average signal is computed based on a plurality of sensed sets of radar signals.

4. The detection system as defined in claim 1, wherein said controller compares the frequency domain of sensed signals within the frequency range to a predetermined frequency characteristic, and further identifies a frequency of the sensed signals indicative of movement of an occupant due to one of heartbeat and breathing.

5. The detection system as defined in claim 4, wherein the frequency domain of sensed signals comprises an average signal waveform computed from a plurality of sets of sensed signals.

6. The detection system as defined in claim 1, wherein said radar motion sensor comprises a Differential Pulse Doppler radar motion sensor.

7. The detection system as defined in claim 1, further comprising a signal classifier for classifying the sensed signals into pulse type signals and continuous type signals, wherein the continuous type signals are processed by the controller to determine the presence of movement of an occupant due to one of heartbeat and breathing.

8. The detection system as defined in claim 7, wherein the pulse type signals are ignored by the controller in determining the presence of movement of an occupant due to one of heartbeat and breathing.

9. The detection system as defined in claim 7, wherein the continuous type signals are further classified into low power signals and high power signals, wherein the low power signals are processed to determine the presence of movement of an occupant due to one of heartbeat and breathing.

10. The detection system as defined in claim 1, wherein the controller generates one of an output signal of a high confidence level and a low confidence level.

11. The detection system as defined in claim 10, wherein the controller generates one of a high confidence level, a low confidence level, and an intermediate confidence level.

12. A method of detecting the presence of an occupant in a vehicle, said method comprising the steps of:

transmitting radar signals within a compartment in a vehicle;

receiving the transmit radar signals;

generating radar sensor output signals;

transforming the radar sensor output signals to a frequency domain;

processing the frequency domain of radar sensor output signals within a frequency range; and

determining movement due to one of breathing and heartbeat of an occupant based on the processing.

13. The method as defined in claim 12, wherein said step of processing the frequency domain of radar sensor output signals comprises determining an average value of the radar sensor output signals within the frequency range, and comparing the average value to a threshold value, wherein the movement is determined as a function of the comparison.

14. The method as defined in claim 12, wherein said step of processing the frequency domain of radar sensor output signals comprises comparing the frequency domain of radar sensor output signals within the frequency range to a predetermined frequency characteristic indicative of movement due to one of heartbeat and breathing of an occupant.

15. The method as defined in claim 14, wherein said step of comparing comprises recognizing a pattern having the predetermined frequency characteristic.

16. The method as defined in claim 12, wherein said method further comprises the step of converting the radar sensor output signals from analog to digital signals.

17. The method as defined in claim 12 further comprising the step of averaging the radar sensor output signals.

18. The method as defined in claim 12 further comprising the step of comparing an amplitude of the radar sensor output signals to an upper threshold and determining movement of an occupant if the radar sensor output signal exceeds the upper threshold.

19. The method as defined in claim 12 further comprising the steps of:

comparing the received radar sensor output signals with an upper threshold;

determining movement of an occupant in the vehicle if the radar sensor output signals exceed the upper threshold;

comparing the radar sensor output signals with a lower threshold less than the upper threshold;

determining the presence of no movement due to an occupant in the vehicle when the received radar sensor output signals are less than the lower threshold; and

comparing the frequency response of the radar sensor output signals to a predetermined frequency of movement due to one of heartbeat and breathing of an occupant when the radar sensor output signals are between the upper and lower thresholds.

20. The method as defined in claim 12 further comprising the step of classifying the radar sensor output signals into pulse type signals and continuous type signals, wherein the continuous type signals are processed to determine movement due to one of breathing and heartbeat of an occupant.

21. The method as defined in claim 20 further comprising the step of ignoring the pulse type signals during the processing step.

22. The method as defined in claim 20 further comprising the step of classifying the continuous type signals into low power signals and high power signals, wherein the low power signals are processed to determine the movement due to one of breathing and heartbeat of an occupant.

23. The method as defined in claim 12 further comprising the step of generating one of an output signal of a high confidence level and a low confidence level.

24. The method as defined in claim 12 further comprising the step of generating one of an output signal of a high confidence level, a low confidence level, and an intermediate level.