System and method for detecting an object at a location

• US 20090267622A1
• Filed: 04/28/2008
• Published: 10/29/2009
• Est. Priority Date: 04/28/2008
• Status: Active Grant

• Current Assignee: Aptiv Technologies AG (Aptiv PLC)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Griffin, Dennis P., Hansen, Mark C., Jaraki, Mohamed R., Kincaid, Kevin D.
• Granted Patent: US 7,876,106 B2
• Time in Patent Office: Days
• US Class Current: 324/684
• CPC Class Codes: B60R 2022/4858 for sensing pressure on seat
• CPC Class Codes: B60R 21/01532 using electric or capacitive field sensors

Abstract

An occupancy detection system includes a signal generator coupled to an electrode, the signal generator configured to output a first signal at a first frequency and a second signal at a second frequency. The system further includes a voltage detection circuit connected to an output terminal of the signal generator and to an input terminal of the electrode, wherein the voltage detection circuit is configured to measure a first voltage responsive to the first signal at the first frequency and a second voltage responsive to the second signal at the second frequency. A control module in communication with the voltage detection circuit is configured to detect a state of occupancy based on the first voltage and the second voltage.

Claims

1. An occupancy detection system, comprising:

a signal generator coupled to an electrode, the signal generator configured to output a first signal at a first frequency and a second signal at a second frequency;

a voltage detection circuit connected to an output terminal of the signal generator and to an input terminal of the electrode, the voltage detection circuit configured to measure a first voltage responsive to the first signal at the first frequency and a second voltage responsive to the second signal at the second frequency; and

a control module in communication with the voltage detection circuit, the control module being configured to detect a state of occupancy based on the first voltage and the second voltage.

2. The detection system of claim 1, wherein the state of occupancy includes an environmental condition.

3. The detection system of claim 1, wherein the state of occupancy includes the presence of an object at a location.

4. The detection system of claim 1, wherein the voltage detection circuit includes a capacitor having a first terminal connected to the output terminal of the signal generator and a second terminal connected to the input terminal of the electrode.

5. The detection system of claim 4, wherein the voltage detection circuit further includes a means for measuring the first and second voltages at the second terminal of the capacitor.

6. The detection system of claim 5, wherein the control module is configured to determine a compensation factor based on a comparison of the first and second voltages.

7. The detection system of claim 5, wherein a difference between the first and second voltages at the second terminal of the capacitor indicates an environmental condition.

8. The detection system of claim 7, wherein the environmental condition is humidity.

9. The detection system of claim 1, wherein one or both of the first and second voltages is responsive to an impedance of a load.

10. The detection system of claim 4, further including an airbag system in communication with the control module.

11. The detection system of claim 10, wherein the control module is configured to compensate for the presence of an environmental condition independently from the presence of an object at a location.

12. The detection system of claim 1, wherein the voltage detection circuit includes a resistor connected to a means for measuring voltage at the input terminal of the electrode.

13. The detection system of claim 1, wherein the first frequency is distinct from the second frequency.

14. A method of detecting an object at a location, said method comprising the steps of:

applying a first signal at a first frequency to an input terminal of an electrode;

measuring a first voltage at the input terminal of the electrode, said first voltage being responsive to the first signal at the first frequency;

applying a second signal at a second frequency to the input terminal of the electrode;

measuring a second voltage at the input terminal of the electrode, said second voltage being responsive to the second signal at the second frequency;

comparing the first voltage to the second voltage to determine a state of occupancy at the location.

15. The method of claim 14, further including converting the first and second voltages to digital amplitudes.

16. The method of claim 15, further including determining the presence of an environmental condition based on a comparison of the digital amplitudes for the first and second voltages.

17. The method of claim 14, further including generating a control signal to an airbag control system based on the state of occupancy.

18. The method of claim 17, further including applying a compensation factor to the control signal to compensate for the presence of an environmental condition.

19. The method of claim 17, further including adjusting the control signal to compensate for an environmental condition if there is a difference between the first voltage and the second voltage.

20. The method of claim 18, further including determining the compensation factor based on a look-up table.