Aerodynamics as well as aesthetics trends in automotive windshield design are starting to influence the future design of rain sensors. In this work, we present a novel sensor based on electrical flux sensing using an array of fractal-shaped transceiver electrodes for the detection of various modes of rain interaction on the windshield. The flexible smart-card thin sensor can be embedded onto or sandwiched into the glass during lamination. The fringe field extends out from the transmitting electrode through the glass and back to the receiver electrodes and is capable of millimeter resolution. Rain drops interacting with this field projects an electrical image onto the receivers array plane, producing a signal that fingerprints the dynamics of rain onto the glass surface Changes in field strength as low as 10 nV/cm can be detected at the receiving electrodes using a multi-channel on-chip 24 bit resolution sigma-delta converter. Sensing areas up to (1500 mm2) three times larger than current glass based optical sensors is achieved. A robust algorithm based on the spatio-temporal correlation of the rain induced signals at the receiver electrodes within the array captures the various nuances of water interaction on glass while simultaneously improving the selectivity of the sensor to water based events and thus rejecting artifacts and spurious signals such as electromagnetic interference all with a view to decreasing the probability of false wipes significantly. The sensor consumes low power (milliwatts), high resolution (millimeter), has low latency (millisecond), high update rate (up to 100 Hz per channel), high immunity to noise (>70 dB), are not affected by dirt, surface texture or reflectivity of coatings on the glass, and can operate with minimal deletion of the infrared reflective coating on high end windshields. The modular electronics also integrates a compact temperature/ humidity sensor and an ambient light intensity sensor capable of multiplexing outputs from three distinct bands of solar spectrum namely UV, Visible and IR.
Flexibler Dünnschicht-Sensor zur Regenerkennung auf Basis elektrischer Felder
2009
14 Seiten, 6 Bilder, 7 Quellen
Aufsatz (Konferenz)
Englisch
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