METHOD FOR DETERMINING A RATE OF RAIN

• US 20050016275A1
• Filed: 07/21/2003
• Published: 01/27/2005
• Est. Priority Date: 07/21/2003
• Status: Active Grant

• Current Assignee: AGC Automotive Americas Co. (AGC, Inc.)
• Original Assignee: AGC America Incorporated (AGC, Inc.)
• Inventors: Rohde, Mitchell M., Pankey, Brent W., Ackerman, Mark S., Williams, William J., Byrne, Colin John
• Granted Patent: US 6,892,580 B2
• Time in Patent Office: Days
• US Class Current: 73/579
• CPC Class Codes: B60S 1/0818 including control systems responsive to external conditions, e.g. by detection of moisture, dirt or the like
• CPC Class Codes: B60S 1/0859 Other types of detection of rain, e.g. by measuring friction or rain drop impact
• CPC Class Codes: G01W 1/14 Rainfall or precipitation gauges measuring volume in general G01F
• CPC Class Codes: Y10S 318/02 Windshield wiper controls

Abstract

A method for determining a rate of rain falling on a surface. As rain falls and strikes the surface, vibrations are generated on the surface. The vibrations are sensed and a vibration signal is generated, the vibration signal being proportional to the vibrations of the surface. The vibration signal includes peaks. The peaks of the vibration signal are determined. The time intervals between the peaks are then determined. Using the time intervals, a number n₁ of timer intervals that occur between a first time and a second time are counted. A number n₂ of time intervals that occur between the second time and a third time are also counted. The rain rate λ is then determined using an equation that is derived from a point process equation and utilizes n₁ and n₂.

Claims

1. A method for determining a rate of rain falling on a surface wherein the rain causes vibrations of the surface, said method comprising the steps of:

sensing the vibrations of the surface;

generating a vibration signal proportional to the vibrations of the surface, wherein the vibration signal includes peaks;

determining the peaks of the vibration signal;

determining intervals of time between the peaks;

counting a number n₁ of intervals of time that occur between a first time and a second time and that fall in a first range of the intervals of time;

counting a number n₂ of intervals of time that occur between the second time and a third time and that fall in a second range of the intervals of time; and

determining the rain rate λ

with an equation derived from a point process equation utilizing n₁ and n₂.

2. A method as set forth in claim 1 further comprising the step of maintaining the first range and the second range of intervals of time equal in a time span w.

3. A method as set forth in claim 2 wherein the step of determining the rain rate λ

with an equation derived from a point process equation utilizing n₁ and n₂ is further defined as determining an intermediate rain rate λ

_int with an equation λ

_int=−

2·

(n₂−

n₁)/w·

(n₂+n₁).

4. A method as set forth in claim 3 further comprising the step of successively determining the intermediate rain rate λ

_int to produce a plurality of intermediate rain rates λ

_int.

5. A method as set forth in claim 4 further comprising the step of averaging the plurality of intermediate rain rates λ

_int to determine the rain rate λ

.

6. A method as set forth in claim 1 wherein the first range of the intervals of time is further defined as all intervals of time less than or equal to the second time, the second range of the intervals of time is further defined as all intervals of time greater than the second time, and the step of determining a rain rate λ

with an equation derived from a point process equation utilizing n₁ and n₂ is further defined as determining the rain rate λ

with an equation λ

=n₁/n₂.

7. A method as set forth in claim 1 wherein the first range of the intervals of time is further defined as all intervals of time less than or equal to the second time, the second range of the intervals of time is further defined as all intervals of time greater than the second time, and the step of determining a rain rate λ

with an equation derived from a point process equation utilizing n₁ and n₂ is further defined as determining the rain rate λ

with an equation λ

=n₁/(T·

n₂), wherein T represents the second time.

8. A method as set forth in claim 1 further comprising the step of generating a series of digital values that are representative of the vibration signal, each digital value having a magnitude component and a time component.

9. A method as set forth in claim 8 further comprising the step of modifying the magnitude components of the digital values to enhance the peaks of the vibration signal.

10. A method as set forth in claim 9 wherein the step of modifying the magnitude components comprises the step of detecting a first magnitude v(n−

1), a second magnitude v(n), and a third magnitude v(n+1).

11. A method as set forth in claim 10 wherein the step of modifying the magnitude components further comprises the step of computing an enhanced magnitude v_e(n) with an equation v_e(n)=v²(n)−

A·

v(n−

1)·

v(n+1), wherein A is a scaling number selected to maximize the enhancement of peaks.

12. A method as set forth in claim 11 wherein the step of modifying the magnitude components further comprises the step of successively determining enhanced magnitudes v_e(n) to provide an enhanced series of digital values, each enhanced digital value having an enhanced magnitude component and the time component.

13. A method as set forth in claim 12 wherein the step of determining the peaks of the vibration signal comprises the step of sorting the enhanced series of digital values by the magnitude component of each enhanced digital value.

14. A method as set forth in claim 13 wherein the step of determining the peaks of the vibration signal further comprises the step of discarding all digital values with magnitude components that are not greater than a certain threshold from the enhanced series of digital values.

15. A method as set forth in claim 14 further comprising the step of varying the certain threshold based on a size of droplets of rain.

16. A method as set forth in claim 14 wherein the step of determining the peaks of the vibration signal further comprises the step of determining a largest enhanced magnitude in the enhanced series of digital values to identify a valid peak.

17. A method as set forth in claim 16 wherein the step of determining the peaks of the vibration signal further comprises the step of determining a next largest enhanced magnitude component in the enhanced series of digital values that is a set time apart from the largest enhanced magnitude component to identify another valid peak.

18. A method as set forth in claim 17 wherein the step of determining the peaks of the vibration signal further comprises the step of successively determining the next largest enhanced magnitude component in the enhanced series of digital values that is a set time apart from any of the valid peaks to identify additional valid peaks.

19. A method as set forth in claim 8 wherein the step of determining the peaks of the vibration signal further comprises the step of analyzing each digital value as the digital value is generated from the vibration signal to determine if the magnitude component of the digital value exceeds a certain threshold.

20. A method as set forth in claim 19 wherein the step of determining the peaks of the vibration signal further comprises the step of identifying a valid peak when the magnitude component of the digital value first exceeds the certain threshold.

21. A method as set forth in claim 20 wherein the step of determining the peaks of the vibration signal further comprises the step of starting a timer to run for a certain time when the magnitude component of the digital value exceeds the certain threshold for preventing the identification of valid peaks while the timer is running.

22. A method as set forth in claim 21 further comprising the step of varying the certain threshold based on a size of droplets of rain.

23. A method as set forth in claim 12 wherein the step of determining the peaks of the vibration signal further comprises the step of analyzing each enhanced digital value as the enhanced digital value is generated to determine if the magnitude component of the enhanced digital value exceeds a certain threshold.

24. A method as set forth in claim 23 wherein the step of determining the peaks of the vibration signal further comprises the step of identifying a valid peak when the magnitude component of the enhanced digital value first exceeds the certain threshold.

25. A method as set forth in claim 24 wherein the step of determining the peaks of the vibration signal further comprises the step of starting a timer to run for a certain time when the magnitude component of the enhanced digital value exceeds the certain threshold for preventing the identification of valid peaks while the timer is running.

26. A method as set forth in claim 25 further comprising the step of varying the certain threshold based on a size of droplets of rain.

27. A method as set forth in claim 1 further comprising the step of producing a rain signal in response to the determined rain rate λ

.

28. A method as set forth in claim 27 further comprising the step of actuating at least one wiper in response to the rain signal to remove rain from the surface.

29. A method as set forth in claim 28 wherein the wiper actuates, at a frequency and the method further comprising the step of modifying the rain signal based on the frequency and the rain rate.

30. A method for determining a rate of rain falling on a surface wherein the rain causes vibrations of the surface, said method comprising the steps of:

sensing the vibrations of the surface;

generating a vibration signal proportional to the vibrations of the surface, wherein the vibration signal includes peaks;

determining the peaks of the vibration signal;

determining intervals of time between the peaks; and

determining the rain rate λ

by utilizing a count of the intervals of time with an equation derived from principles of a point process.