Control of windshield wiper by integration and differentiation of sensor signal

• US 5,140,233 A
• Filed: 11/30/1990
• Issued: 08/18/1992
• Est. Priority Date: 01/12/1990
• Status: Expired due to Fees

• Current Assignee: VDO Adolf Schindling AG (Vodafone Group PLC)
• Original Assignee: VDO Adolf Schindling AG (Vodafone Group PLC)
• Inventors: Wallrafen, Werner
• Primary Examiner(s): Wysocki, A. Jonathan
• Application Number:
  US07/621,042
• Time in Patent Office: 627 Days
• Field of Search: 318/443, 318/444, 318/DIG. 2, 318/483, 318/643, 15/250 C, 15/250.12, 15/250.13, 307/10.1
• US Class Current: 318/264
• 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: G01N 27/223 for determining moisture content, e.g. humidity rain detectors on vehicle windows B60S1/0825
• CPC Class Codes: Y10S 15/15 Moisture responsive
• CPC Class Codes: Y10S 318/02 Windshield wiper controls

Abstract

A method and a system for controlling a windshield wiper, particularly on a motor vehicle, provides that the windshield wiper is automatically activated as a function of the intensity of rain. A frequency-limited variation of the signal of a sensor serves as a measure of the intensity of the rain.

Claims

1. A method for controlling a windshield wiper, suitable for a motor vehicle, in which the windshield wiper is automatically turned on as a function of the intensity of the rain, the method comprising the steps of

sensing the presence of rain with an electrically activated sensor;

employing a frequency-limited variation of a signal of the sensor to serve as a measure of the rain; and

wherein said employing step includes;

integrating the value of the sensor signal;

differentiating a result obtained from the step of integrating, the differentiating being done with a large time constant in order to compensate for the evaporation of water; and

activating the windshield wiper when a result of the differentiating step exceeds a threshold value.

2. A method according to claim 1, further comprising the steps, prior to said integrating step, of

conducting the sensor signal via a bandpass filter to obtain a band-limited signal;

and

forming the effective value of the band-limited signal.

3. A method according to claim 1, further comprising the steps, prior to said integrating step, of

forming an average value of the sensor signal;

and

calculating the variance or standard deviation of the instantaneous signal from an average value of the sensor signal.

4. A method according to claim 1, further comprising

restarting the integration after each wiping process.

5. A method according to claim 4, further comprising

differentiating a result obtained from the step of integrating, the differentiating being done with a large time constant in order to compensate for the evaporation of water.

6. A method according to claim 3, further comprising

only values of the variance which exceed a threshold value are evaluated and integrated.

7. A method according to claim 3, wherein

a variation which is less than a predetermined threshold value is detected as a dry windshield and that the sensor signal present at this time serves as comparison value for activating the windshield wiper.

8. A method according to claim 7, further comprising

activating the windshield wiper when the sensor signal exceeds a comparison value.

9. A system for controlling a windshield wiper, suitable for a motor vehicle, in which the windshield wiper is automatically turned on as a function of the intensity of the rain, comprising

an analog-to-digital converter, and a microcomputer;

and

a rain sensor, the sensor being connected via the analog-to-digital converter to the microcomputer; and

the microcomputer is operated in accordance with a program to provide for integration of a signal of the sensor followed by differentiation of a result of the integration to provide said function of the rain intensity.

10. A system according to claim 9, wherein

the sensor is a capacitive wetness sensor.