Road surface condition detection device and road surface condition detection method

Patent metadata

Field	Value
Publication number	US-9341708-B2
Application number	US-201314419758-A
Country	US
Kind code	B2
Filing date	Aug 1, 2013
Priority date	Aug 8, 2012
Publication date	May 17, 2016
Grant date	May 17, 2016

Abstract

A radio waves receiving unit receives horizontally polarized waves and vertically polarized waves of radio waves radiated from an object at a radiation angle. An image generation unit generates a horizontally polarized waves image and a vertically polarized waves image based on the horizontally polarized waves and the vertically polarized waves, respectively. A polarization ratio calculation unit calculates, for each radiation angle, a polarization ratio which is a ratio of intensity of the horizontally polarized waves to the vertically polarized waves based on the horizontally polarized waves image and the vertically polarized waves image. A refractive index calculation unit calculates a refractive index of the object based on a change between polarization ratios of two different radiation angles. A road surface condition recognition unit recognizes a condition of a road surface based on the refractive index.

First claim

The invention claimed is:

1. A road surface condition detection device comprising:
a radio waves receiving unit configured to receive intensity of horizontally polarized waves and intensity of vertically polarized waves of radio waves radiated from a road surface region at a radiation angle;
a polarization ratio calculation unit configured to calculate, for each radiation angle, a polarization ratio which is a ratio of the intensity of the horizontally polarized waves and the intensity of the vertically polarized waves;
a refractive index calculation unit configured to calculate a refractive index of the road surface region according to a change between polarization ratios of two different radiation angles calculated by the polarization ratio calculation unit; and
a road surface condition recognition unit configured to recognize a condition of a road surface based on the refractive index calculated by the refractive index calculation unit.

2. The road surface condition detection device according to claim 1 , wherein:
the road surface condition detection device is installed in a vehicle; and
the polarization ratio calculation unit calculates the polarization ratios of the two different radiation angles according to a change in travel distance.

3. The road surface condition detection device according to claim 1 , comprising a first radio waves receiving unit and a second radio waves receiving unit aligned in a vertical direction, each of the first radio waves receiving unit and the second radio waves receiving unit corresponding to the radio waves receiving unit,
wherein the polarization ratio calculation unit calculates the polarization ratios of the two different radiation angles by use of a difference of elevation of the first radio waves receiving unit and the 4 second radio waves receiving unit.

4. The road surface condition detection device according to claim 1 , wherein the refractive index calculation unit calculates the refractive index at prescribed timing after the polarization ratio calculation unit calculates the polarization ratios.

5. The road surface condition detection device according to claim 1 , further comprising a refractive index storage unit configured to store refractive index information including items of road surface conditions in relation to refractive indexes,
wherein the road surface condition recognition unit recognizes the condition of the road surface based on the refractive index calculated by the refractive index calculation unit with reference to the refractive index information stored in the refractive index storage unit.

6. The road surface condition detection device according to claim 5 , wherein the road surface condition recognition unit recognizes the condition of the road surface in such a manner as to exclude a prescribed item of the road surface conditions in the refractive index information depending on an ambient temperature.

7. The road surface condition detection device according to claim 1 , wherein the road surface condition recognition unit determines a boundary corresponding to the refractive index calculated by the refractive index calculation unit in the images generated by the image generation unit so as to calculate a distance to an actual position corresponding to the boundary.

8. A road surface condition detection method comprising:
receiving intensity of horizontally polarized waves and intensity of vertically polarized waves of radio waves radiated from a road surface region at a radiation angle by a receiver;
calculating, for each radiation angle, a polarization ratio which is a ratio of the intensity of the horizontally polarized waves to the intensity of the vertically polarized waves based on the generated horizontally polarized waves image and vertically polarized waves image by a processor;
calculating a refractive index of the road surface region according to a change between calculated polarization ratios of two different radiation angles by the processor; and
recognizing, with the processor, a condition of a road surface based on the calculated refractive index.

9. A road surface condition detection device comprising:
a radio waves receiving unit configured to receive intensity of horizontally polarized waves and intensity of vertically polarized waves of radio waves radiated from a road surface region at a radiation angle;
a polarization ratio calculation unit configured to calculate, for each radiation angle, a polarization ratio which is a ratio of the intensity of the horizontally polarized waves and the intensity of the vertically polarized waves;
a refractive index calculation unit configured to calculate a refractive index of the road surface region according to a change between polarization ratios of two different radiation angles calculated by the polarization ratio calculation unit; and
a road surface condition recognition unit installed in a vehicle and configured to recognize a condition of a road surface based on the refractive index calculated by the refractive index calculation unit, wherein the polarization ratio calculation unit calculates the polarization ratios of the two different radiation angles according to a change in travel distance of the vehicle.

Assignees

• Nissan Motor

Inventors

• Nakamura Mitsunori
• Satoh Hiroshi

Classifications

• G01S7/024

  using polarisation effects (in waveguides H01P1/165; for aerials H01Q, e.g. H01Q15/22, H01Q15/24, H01Q19/195) · CPC title

• G01W1/00 Primary

  Meteorology · CPC title

• G01S2013/932

  using own vehicle data, e.g. ground speed, steering wheel direction · CPC title

• G01S13/89

  for mapping or imaging · CPC title

• G01S7/411 Primary

  Identification of targets based on measurements of radar reflectivity (G01S7/415 takes precedence) · CPC title