Method and apparatus for detecting ice and packed snow
First Claim
1. An apparatus for detecting the presence of ice or smooth packed snow on a road surface, the apparatus comprising:
- a source of electromagnetic radiation for illuminating an area of the road surface;
a modulating circuit connected to the source for modulating the radiation provided by the source, the modulating circuit including means for generating a constant frequency drive signal at a frequency of at least 2 kHz, whereby the source is driven by the constant frequency drive signal to provide pulses at said constant frequency;
a detector for receiving radiation reflected back from the area of the road surface, to generate a detector signal; and
a detection circuit connected to the detector for demodulating the detector signal, to generate an intermediate signal indicative of the reflectivity of the illuminated area, thereby indicating the presence of ice or smooth packed snow, the detection circuit comprising a filtering circuit for filtering out frequencies above and below the constant frequency, an intermediate amplifier connected to the output of the filtering circuit, a rectifying network means connected to the output of the intermediate amplifier, for generating a DC signal as an intermediate signal, and a comparator connected to the output of the rectifying network and having an input for a fixed level, the output of the comparator being an output signal indicative of the detected reflectivity.
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Accused Products
Abstract
An apparatus for detecting the presence of ice or smooth packed snow on a road surface has a source of electromagnetic radiation, for example, a light emitting diode. This is mounted to illuminate an area of the road surface. It is driven by a modulating circuit at a known frequency. A detector is mounted adjacent the light source to receive radiation reflected back from the road surface, to generate a detector signal. This signal is demodulated by a demodulator to generate an intermediate signal. This is preferably compared with a fixed value, to determine whether the reflectivity of the road surface exceeds a set value, indicative of the presence of ice.
66 Citations
21 Claims
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1. An apparatus for detecting the presence of ice or smooth packed snow on a road surface, the apparatus comprising:
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a source of electromagnetic radiation for illuminating an area of the road surface; a modulating circuit connected to the source for modulating the radiation provided by the source, the modulating circuit including means for generating a constant frequency drive signal at a frequency of at least 2 kHz, whereby the source is driven by the constant frequency drive signal to provide pulses at said constant frequency; a detector for receiving radiation reflected back from the area of the road surface, to generate a detector signal; and a detection circuit connected to the detector for demodulating the detector signal, to generate an intermediate signal indicative of the reflectivity of the illuminated area, thereby indicating the presence of ice or smooth packed snow, the detection circuit comprising a filtering circuit for filtering out frequencies above and below the constant frequency, an intermediate amplifier connected to the output of the filtering circuit, a rectifying network means connected to the output of the intermediate amplifier, for generating a DC signal as an intermediate signal, and a comparator connected to the output of the rectifying network and having an input for a fixed level, the output of the comparator being an output signal indicative of the detected reflectivity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An apparatus for detecting the presence of ice or smooth packed snow on a road surface, the apparatus comprising:
- a source of electromagnetic radiation for illuminating an area of the road surface;
a modulating circuit connected to the source for modulating the radiation provided by the source, whereby the source is driven to provide pulses at a known frequency;
a detector for receiving radiation reflected back from the area of the road surface, to generate a detector signal; and
a detection circuit connected to the detector for demodulating the detector signal, to generate an intermediate signal indicative of the reflectivity of the illuminated area, thereby indicating the presence of ice or smooth packed snow, and at least one warning device connected to the detection circuit, wherein the apparatus comprises a sensor assembly, including said source and said detector, adapted for mounting to a chassis of a vehicle, underneath the vehicle and directed at the ground, at a location in front of the wheels of the vehicle so as to be capable of examining a surface before it is disturbed by passage of the vehicle wheels, an indicator assembly adapted for mounting within an occupant compartment of the vehicle, the indicator assembly including the warning device, and connection means providing a connection between the indicator assembly and sensor assembly. - View Dependent Claims (13, 14, 15, 16)
- a source of electromagnetic radiation for illuminating an area of the road surface;
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17. A method of detecting the presence of ice or smooth packed snow on a road surface, the method comprising the steps of:
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(1) providing a sensor assembly, including illumination and detection means mounted on a wheeled vehicle ahead of the wheels thereof so as to examine a surface before disturbance by the wheels, and an indicator assembly within an occupant compartment of the vehicle including indicating means for indicating the condition of a surface on which the vehicle is travelling; (2) illuminating an area of a road surface with electromagnetic radiation from the illumination means which is pulsed at a frequency of at least 2 kHz; (3) detecting radiation reflecting back from the illuminated area of the road surface with the detection means, to generate a detection signal; and (4) demodulating the detected signal, to filter out unwanted signals, to generate an intermediate signal indicative of the reflectivity of the road surface, thereby indicating the presence of ice or smooth packed snow. - View Dependent Claims (18, 19, 20, 21)
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Specification