| 摘要 |
Disclosed is an automatic windshield wiper control system which responds to sensed moisture in a manner which is responsive to changes in conditions, yet subjectively smooth. Moisture and noise sensitive signals from a sensor are digitized, and a functional block detects the reversals of the moisture sensing signal towards a quiescent level. These reversals are considered rain events and a method is disclosed for producing an ongoing measure of the frequency of these events. The resulting signal is representative of the flow rate of the raindrops impinging upon the moisture sensor. Another functional block with a logarithmic characteristic converts this quantity into an intensity value, in a manner which mimics human perception. A multiple time-constant averaging means maintains a value representative of the long-range prevailing conditions under which the device is operating. This long range average is combined with a medium range average to produce a rain-intensity signal which permits rapid but bounded response to sudden changes in conditions. A mode-determination block uses this signal to determine the appropriate wiper actuation rate. The disclosed control strategy features hysteresis, giving the system a propensity to continue operating in a given mode. |
