Wind measurement apparatus and lidar apparatus

Patent metadata

Field	Value
Publication number	US-10557929-B2
Application number	US-201616099517-A
Country	US
Kind code	B2
Filing date	Jun 27, 2016
Priority date	Jun 27, 2016
Publication date	Feb 11, 2020
Grant date	Feb 11, 2020

Abstract

A lidar apparatus includes a foreign matter detector detecting foreign matter hindering laser light and reflected light from passing through the light transmission window, based on at least one of the measurement success or failure result and the signal-to-noise ratio; a precipitation determiner determining whether precipitation, included in the foreign matter, exists on the external surface of the light transmission window based on a time elapsed since the latest wiper operation, when the foreign matter detector detects the foreign matter, and that the precipitation does not exist, when the foreign matter detector does not detect the foreign matter. When the precipitation determiner determines that precipitation exists, the wiper operation controller causes the wiper to operate and the washer fluid supplier not to operate. When the precipitation determiner does not determine that precipitation exists while the foreign matter detector detects that foreign matter exists, the wiper operation controller causes the washer fluid supplier and the wiper to operate.

First claim

The invention claimed is:

1. A wind measurement apparatus comprising:
an optical device to emit a laser light into a space and to process a reflected light being the laser light reflected from the space;
a casing to house the optical device;
a light transmission window, provided in the casing, to transmit the laser light and the reflected light;
a wiper to remove foreign matter existing on an external surface of the light transmission window;
a washer fluid supplier to supply a washer fluid to the external surface of the light transmission window;
a wind velocity measurer to measure a wind velocity vector in the space, from a received signal obtained by photoelectric conversion of the reflected light;
a wind velocity storage to store a measurement success or failure result being an indicator representing whether or not the wind velocity vector is measured by the wind velocity measurer and the measured wind velocity vector;
a signal-to-noise ratio calculator to calculate a signal-to-noise ratio of the received signal;
a foreign matter detector to detect, based on at least one of the measurement success or failure result and the signal-to-noise ratio, the foreign matter existing on the external surface of the light transmission window, the foreign matter hindering the laser light and the reflected light from passing through the light transmission window;
a precipitation determiner to determine
whether precipitation, included in the foreign matter, exists on the external surface of the light transmission window based on a time elapsed since the latest wiper operation, when the foreign matter detector detects the foreign matter, and
that the precipitation does not exist, when the foreign matter detector does not detect the foreign matter; and

a wiper operation controller to cause
the wiper to operate and the washer fluid supplier not to operate, when the precipitation determiner determines that the precipitation exists, and
the washer fluid supplier and the wiper to operate, when the precipitation determiner does not determine that the precipitation exists and the foreign matter detector detects that the foreign matter exists.

2. The wind measurement apparatus according to claim 1 , wherein
when the wiper operation controller causes the wiper to operate and the washer fluid supplier not to operate and thereafter at least one of the measurement success or failure result and the signal-to-noise ratio does not become equal to or higher than a predetermined improvement determining threshold, the wiper operation controller causes the washer fluid supplier and the wiper to operate.

3. The wind measurement apparatus according to claim 2 , wherein
when a wiper operation interval condition is satisfied, the precipitation determiner determines that the precipitation exists on the external surface of the light transmission window, and
the wiper operation interval condition is a condition that detection within a predetermined second period is repeated a predetermined number of times or more, the detection being detection of decrease, to less than a predetermined decrease threshold after being improved by the wiper operation, of at least one of the measurement success or failure result and the signal-to-noise ratio.

4. The wind measurement apparatus according to claim 3 , wherein
when the wiper operation interval condition is satisfied and a signal-to-noise ratio decrease condition is satisfied, the precipitation determiner determines that the precipitation exists on the external surface of the light transmission window,
the signal-to-noise ratio decrease condition is a condition that a decrease of the signal-to-noise ratio by more than a prescribed decay after being improved by a latest wiper operation is detected within a predetermined third period from a latest operation of the wiper, and
the decrease is a decrease of at least a predetermined number of the received signals out of a plurality of the received signals derived from a plurality of the reflected lights passing through a plurality of respective different portions of the light transmission window.

5. The wind measurement apparatus according to claim 4 , wherein when the signal-to-noise ratio decrease condition is satisfied for a predetermined divided received signal out of divided received signals into which the received signal is divided to correspond to a plurality of divided spaces into which the space is divided by distance from the optical device, the precipitation determiner determines that the precipitation exists on the external surface of the light transmission window.

6. The wind measurement apparatus according to claim 4 , wherein
when the wiper operation interval condition is satisfied and a wind direction condition is satisfied, the precipitation determiner determines that the precipitation exists on the external surface of the light transmission window, and
the wind direction condition is a condition that a vertical component of the wind velocity vector measured by the wind velocity measurer in a fourth period from a latest operation of the wiper is equal to or less than a predetermined threshold for a wind speed measured in such a way that a wind blowing downward has a negative value.

7. The wind measurement apparatus according to claim 3 , wherein
when the wiper operation interval condition is satisfied and a wind direction condition is satisfied, the precipitation determiner determines that the precipitation exists on the external surface of the light transmission window, and
the wind direction condition is a condition that a vertical component of the wind velocity vector measured by the wind velocity measurer in a fourth period from a latest operation of the wiper is equal to or less than a predetermined threshold for a wind speed measured in such a way that a wind blowing downward has a negative value.

8. The wind measurement apparatus according to claim 2 , wherein
for each of a plurality of divided spaces into which the space is divided by distance from the optical device, the wind velocity measurer calculates the wind velocity vector, and
a wind velocity acquisition ratio is used as at least a part of the measurement success or failure result, and the wind velocity acquisition ratio is a ratio of the number of wind velocity vectors measured in predetermined divided spaces in a predetermined latest fifth period, with respect to a total number of wind velocity vectors measured in predetermined divided spaces in the predetermined latest fifth period.

9. The wind measurement apparatus according to claim 1 , wherein
when a wiper operation interval condition is satisfied, the precipitation determiner determines that the precipitation exists on the external surface of the light transmission window,
the wiper operation interval condition is a condition that detection within a predetermined second period is repeated a predetermined number of times or more, the detection being detection of decrease, to less than a predetermined decrease threshold after being improved by the wiper operation, of at least one of the measurement success or failure result and the signal-to-noise ratio.

10. The wind measurement apparatus according to claim 9 , wherein
when the wiper operation interval condition is satisfied and a signal-to-noise ratio decrease condition is satisfied, the precipitation determiner determines that the precipitation exists on the external surface of the light transmission window,
the signal-to-noise ratio decrease condition is a condition that a decrease of the signal-to-noise ratio by more than a prescribed decay after being improved by a latest wiper operation is detected within a predetermined third period from a

Assignees

• Mitsubishi Electric Corp

Inventors

• Kajiyama Yutaka
• Yabugaki Yoshiyuki
• Enjo Masayuki

Classifications

• G01S17/58

  Velocity or trajectory determination systems; Sense-of-movement determination systems · CPC title

• G01S7/4813

  Housing arrangements · CPC title

• G01S7/497 Primary

  Means for monitoring or calibrating · CPC title

• G01P5/26

  by measuring the direct influence of the streaming fluid on the properties of a detecting optical wave · CPC title

• G01S2007/4977

  including means to prevent or remove the obstruction · CPC title