Method Of Sensing An Amount Of Moisture On A Surface Of A Substrate With Temperature Compensation

• US 20080099042A1
• Filed: 10/30/2006
• Published: 05/01/2008
• Est. Priority Date: 10/30/2006
• Status: Active Grant

• Current Assignee: AGC Automotive Americas Co. (AGC, Inc.)
• Original Assignee: AGC Automotive Americas R&D, Inc (AGC, Inc.)
• Inventors: Grosh, Karl, Pankey, Brent W., Rohde, Mitchell Max, Byrne, Colin J.
• Granted Patent: US 7,696,710 B2
• Time in Patent Office: Days
• US Class Current: 134/6
• CPC Class Codes: B60S 1/0822 characterized by the arrangement or type of detection means
• CPC Class Codes: B60S 1/0837 with a particular arrangement of the optical elements
• CPC Class Codes: B60S 1/0859 Other types of detection of rain, e.g. by measuring friction or rain drop impact
• CPC Class Codes: B60S 1/0866 including a temperature sensor heating devices for windshield B60H
• CPC Class Codes: G01N 2291/012 Phase angle
• CPC Class Codes: G01N 2291/0253 Condensation
• CPC Class Codes: G01N 2291/02845 Humidity, wetness
• CPC Class Codes: G01N 2291/048 Transmission, i.e. analysed material between transmitter and receiver
• CPC Class Codes: G01N 29/02 Analysing fluids using acoustic emission techniques G01N29/14 ; constructional or flow details for analysing fluids G01N29/222; optoacoustic fluid cells G01N29/2425
• CPC Class Codes: G01N 29/326 compensating for temperature variations
• CPC Class Codes: G01N 29/4427 with stored values, e.g. threshold values

Abstract

A method for determining an amount of moisture on a surface of a substrate includes a step of transmitting a transmitter signal to generate a wave. The transmitter signal has a first phase. The wave is propagated to vibrate the surface. Vibrations in the surface are detected and converted into a receiver signal. The receiver signal has a second phase different than the first phase. The method includes the step of sensing the temperature of the substrate. The amount of moisture on the surface is computed based on a phase shift between the transmitter signal and the receiver signal that has been compensated to account for surface temperature.

Claims

1. A method of determining an amount of moisture on a surface of a substrate, said method comprising the steps of:

transmitting a transmitter signal to generate a vibrational wave;

propagating the vibrational wave to vibrate the substrate;

detecting the vibrations of the substrate;

converting the vibrations into a receiver signal;

sensing the temperature of the substrate; and

compensating for a phase shift between the transmitter signal and the receiver signal attributable to the temperature of the substrate to determine the amount of moisture on the surface.

2. A method as set forth in claim 1 wherein said step of compensating includes determining a measured phase shift corresponding to at least one of the amount of moisture on the surface and the temperature of the substrate.

3. A method as set forth in claim 2 wherein said step of determining the measured phase shift is further defined as calculating a difference between a first phase of the transmitter signal and a second phase of the receiver signal.

4. A method as set forth in claim 2 wherein said step of compensating includes determining a temperature phase shift attributable to the temperature of the substrate.

5. A method as set forth in claim 4 wherein said step of determining the temperature phase shift includes ascertaining the temperature phase shift as a function of the temperature of the substrate.

6. A method as set forth in claim 5 further including a table and wherein said step of determining the temperature phase shift includes storing the temperature phase shift as a function of the temperature of the substrate in the table.

7. A method as set forth in claim 5 wherein said step of determining the temperature phase shift includes retrieving the temperature phase shift from the table.

8. A method as set forth in claim 4 wherein said step of compensating includes determining a corrected phase shift attributable to the amount of moisture on the surface independent of the temperature of the substrate.

9. A method as set forth in claim 8 wherein said step of determining the corrected phase shift is further defined as calculating a difference between the temperature phase shift and the measured phase shift.

10. A method as set forth in claim 8 wherein said step of compensating includes establishing a phase baseline corresponding to the measured phase shift independent of the amount of moisture on the surface and the temperature of the substrate.

11. A method as set forth in claim 10 wherein said step of compensating includes determining a moisture phase shift attributable to the amount of moisture on the surface independent of the temperature of the substrate and the phase baseline.

12. A method as set forth in claim 11 wherein said step of determining the moisture phase shift is further defined as calculating a difference between the corrected phase shift and the phase baseline.

13. A method as set forth in claim 11 wherein said step of compensating includes setting a threshold value corresponding to a minimum measured phase shift independent of the amount of moisture on the surface and the temperature of the substrate.

14. A method as set forth in claim 13 wherein said step of compensating includes comparing the moisture phase shift to the threshold value.

15. A method as set forth in claim 14 further including a wiper system and wherein said method includes a step of actuating the wiper system if the moisture phase shift exceeds the threshold value.

16. A method as set forth in claim 14 wherein said step of compensating includes reestablishing the phase baseline if the moisture phase shift exceeds the threshold value.

17. A method as set forth in claim 14 further including a wiper system and wherein said method includes a step of disabling the wiper system if the moisture phase fails to exceed the threshold value.

18. A method as set forth in claim 1 further including a wiper system and said method includes a step of actuating the wiper system in response to the amount of moisture on the surface.

19. A method as set forth in claim 18 wherein the wiper system includes a plurality of operating levels corresponding to a speed of the wiper system and wherein said step of actuating includes varying the operating level of the wiper system in response to the amount of moisture on the surface.

20. A method as set forth in claim 19 wherein step of varying is further defined as increasing the operating level of the wiper system in response to the amount of moisture on the surface.

21. A method as set forth in claim 19 wherein said step of varying is further defined as decreasing the operating level of the wiper system in response to the amount of moisture on the surface.

22. A method as set forth in claim 1 further including a wiper system and said method includes a step of disabling the wiper system in response to the amount of moisture on the surface.

23. A method of detecting moisture on a surface of a substrate with a wiper system, said method comprising the steps of:

sensing an amount of moisture on the surface of the substrate with a transmitter signal and a receiver signal; and

compensating for a phase shift between the transmitter signal and the receiver signal attributable to the temperature of the substrate.

24. The method as set forth in claim 23 further including a step of actuating the wiper system in response to the phase shift to remove the moisture from the surface of the substrate.

25. A method as set forth in claim 24 wherein the wiper system includes a plurality of operating levels and wherein said step of actuating includes varying the operating level of the wiper system in response to the amount of moisture on the surface.

26. A method as set forth in claim 25 wherein step of varying is further defined as increasing the operating level of the wiper system in response to the amount of moisture on the surface.

27. A method as set forth in claim 25 wherein said step of varying is further defined as decreasing the operating level of the wiper system a in response to the amount of moisture on the surface.

28. A method as set forth in claim 23 further including a step of disabling the wiper system in response to the amount of moisture on the surface.