JP7597367B2 - Airflow measurement device, airflow measurement method, and airflow measurement program - Google Patents

Description

The present disclosure relates to an airflow measurement device, an airflow measurement method, and an airflow measurement program that are used, for example, to detect turbulence encountered by an aircraft.

Clear air turbulence, the strong turbulence that aircraft encounter on clear days, not only affects the comfort of the aircraft, but is often the cause of aircraft damage. Clear air turbulence occurs when the velocity gradient caused by the jet stream, mountain waves, etc., transitions into turbulence, primarily due to Kelvin-Helmholtz instability. As the scale of the turbulence becomes smaller over time, the energy of the turbulence decreases. Therefore, large-scale turbulence at the beginning of its development has a large impact on aircraft. It is desirable to detect turbulence of this scale and large energy and navigate by avoiding it.

When an aircraft enters turbulence, it shakes violently and repeatedly ascends and descends rapidly, placing a large load on the aircraft, which in the worst case scenario can lead to destruction. There are also several accidents each year in which passengers and crew suffer serious or minor injuries due to delayed seatbelt signs. In addition to reducing the burden on the aircraft, turbulence can also affect in-flight service, passenger comfort, and the physical and physical health and lives of passengers and crew, so when pilots notice turbulence ahead, they must avoid it as much as possible.

In Patent Document 1, laser light is emitted forward and the reflected light is received, and the distance and speed in the optical axis direction are determined from the time delay and Doppler shift. In order to obtain more detailed information about the road ahead, laser light is emitted in two directions, up and down, at an angle of about 10 degrees, and the reflected light is received. A plausible forward velocity field is estimated from the time series of the reflected light, etc.

JP 2017-67680 A

The vertical airflow speed obtained by the method of Patent Document 1 is calculated by multiplying the speed in the optical axis direction by the sine of an angle of about 10 degrees up and down, so there is a risk of low accuracy. In addition, the airflow speed calculated is not the airflow speed on the flight path that the aircraft is scheduled to pass through, but the airflow speed in the areas above and below the airspace that the aircraft is scheduled to pass through. For this reason, there is a risk that the airflow speed in the airspace necessary for the aircraft to avoid turbulence cannot be properly calculated.

In view of the above circumstances, the objective of the present disclosure is to provide an airflow measurement device, an airflow measurement method, and an airflow measurement program that can accurately and appropriately calculate the airflow speed in an airspace required for an aircraft to avoid turbulence.

An airflow measuring device according to an embodiment of the present disclosure includes:
Calculating a time delay from when an irradiating device irradiates light onto a virtual surface in the atmosphere that intersects with an optical axis of the light until when a light receiving device receives reflected light of the light;
A calculation device that extracts the reflected light reflected by the virtual surface based on the time delay;
creating a reflected light map showing a pattern of the intensity of the reflected light by plotting the intensity of the reflected light in each grid area of a map corresponding to the virtual surface and including a plurality of grid areas;
Calculating a change in the pattern between the reflected light map and a reflected light map created after a predetermined time has elapsed;
and a calculation device that measures the speed of the airflow on the virtual surface in a direction intersecting the optical axis based on the change in the pattern.

According to this embodiment, the airflow measurement device calculates the time delay of the reflected light from irradiation to reception, extracts the reflected light reflected on a virtual surface that intersects with the optical axis of the light based on the time delay, and creates a reflected light map that shows the intensity pattern of the reflected light reflected on the virtual surface. This makes it possible to create a reflected light map of the reflected light reflected on a virtual surface that has a surface direction that matches the direction of the flow whose speed is to be detected.

the virtual surfaces corresponding to the plurality of reflected light maps are at the same position in the atmosphere;
The calculation device may measure the speed of the airflow in a planar direction of the imaginary surface as a direction intersecting the optical axis.

According to this embodiment, by creating a reflected light map of light reflected from multiple virtual surfaces at the same position in the atmosphere at different times, it is possible to measure the airflow speed in the surface direction of the virtual surfaces.

The virtual plane may be perpendicular to the optical axis of the light irradiated to a point on the virtual plane.

According to this embodiment, it is possible to measure the speed of airflow in a plane direction perpendicular to the optical axis of the light.

The airflow measuring device may be mounted on an aircraft.

According to this embodiment, it is possible to measure the speed of airflow in a plane perpendicular to the optical axis of the light emitted from the aircraft.

The virtual surface may include a flight path along which the aircraft is scheduled to fly.

According to this embodiment, it is possible to measure the air current speed in a plane perpendicular to the flight path that the aircraft is scheduled to take. In particular, it is possible to measure the vertical speed of clear air turbulence. In addition, by appropriately setting the size of the virtual surface, it is possible to accurately and appropriately calculate the air current speed in the airspace required for the aircraft to avoid turbulence.

The virtual surface may include a flight path that the aircraft will fly to avoid turbulence if turbulence is present on the virtual surface.

According to this embodiment, when turbulence is present on a planned flight path on a virtual plane, the aircraft can avoid the turbulence and fly in a safe (i.e., turbulence-free) airspace on the virtual plane.

The calculation device may vary the time delay of the extracted reflected light each time the aircraft irradiates light from a different position on the flight path while in flight.

The length of the delay time varies depending on the distance from the aircraft to the virtual surface. In other words, the distance decreases as the aircraft approaches the virtual surface, and therefore the length of the delay time also decreases. By continuing to extract reflected light that returns in a shorter time, the calculation device can continue to extract reflected light that is reflected by the virtual surface at the same position in the atmosphere, regardless of the position of the aircraft.

The computing device includes:
Extracting inspection sections from the plurality of reflected light maps, each of which corresponds to a same area on the virtual surface;
Calculating changes in the patterns of the plurality of inspection sections extracted from the plurality of reflected light maps, respectively;
A change in the pattern of the plurality of reflected light maps may be calculated.

By appropriately setting the number of grid areas in which the reflected light intensity is plotted, the pattern changes in multiple inspection sections can be calculated more accurately.

The number of the grid areas included in the inspection section is variable;
The number of grid areas, in which the intensity of reflected light is plotted, included in the inspection section may be from several to several tens.

The number of grid areas can be fixed if the emphasis is on reducing the computational load and the pilot's physical burden, or it can be variable if the emphasis is on calculation accuracy.

The irradiation device includes:
a laser oscillation device that oscillates a laser beam having a cross-sectional shape identical to that of an area obtained by dividing the imaginary surface;
and a scanning device that controls an irradiation direction of the laser light and scans all areas of the virtual surface with the laser light.

This allows the laser light to irradiate the entire virtual surface evenly in a short period of time.

The calculation device or the arithmetic device may correct the time delay deviation according to the deviation in irradiation timing caused by scanning the virtual surface with the laser light.

The irradiation device does not irradiate the entire virtual surface at once, but irradiates the entire virtual surface with laser light by scanning the entire virtual surface in sequence. Therefore, strictly speaking, there is a time lag in the irradiation timing from the rectangular area scanned first to the rectangular area scanned last. Therefore, the position of the aircraft is strictly different from the timing of the first scan to the timing of the last scan. Therefore, depending on the time lag in the irradiation timing, the virtual surface may not be perpendicular to the traveling direction (i.e., the optical axis direction at the center of the virtual surface), but may be distorted in a direction that includes a component of the traveling direction (i.e., tilted with respect to the traveling direction). The calculation device or arithmetic device may correct the time delay deviation according to such a deviation in the irradiation timing, so that the virtual surface becomes a surface perpendicular to the traveling direction.

The calculation device further calculates a Doppler shift amount of a frequency between the irradiated light and the reflected light reflected by the virtual surface,
The calculation device may further measure a speed of airflow in a direction of the optical axis on the virtual surface based on the amount of Doppler shift.

The arithmetic device reads out the Doppler shift amount of the light reflected from the virtual surface and the position information from the storage device. The arithmetic device measures the airflow speed in the direction of the optical axis on the virtual surface (i.e., the direction of travel of the aircraft) based on the Doppler shift amount. According to this embodiment, the reflected light used to measure the airflow speed in the planar direction of the virtual surface can also be used to measure the airflow speed in the direction of travel of the aircraft.

The airflow measuring device may further include the irradiation device and the light receiving device.

In this embodiment, the aircraft only needs to be equipped with the minimum amount of hardware, a laser oscillator and a light receiving device, and the processing device uses software processing to measure the airflow speed in the surface direction of the virtual surface based on the reflected light received by the light receiving device. It is also possible to simultaneously detect the airflow speed in the direction of travel based on the amount of Doppler shift.

An airflow measuring method according to an embodiment of the present disclosure includes:
extracting light reflected by the virtual surface based on a time delay between when an irradiating device irradiates light onto a virtual surface in the atmosphere that intersects with an optical axis of the light and when a light receiving device receives reflected light of the light;
creating a reflected light map showing a pattern of the intensity of the reflected light by plotting the intensity of the reflected light in each grid area of a map corresponding to the virtual surface and including a plurality of grid areas;
Calculating changes in the pattern of a plurality of the reflected light maps;
Based on the change in the pattern, the speed of the airflow on the virtual surface in a direction intersecting the optical axis is measured.

An airflow measurement program according to an embodiment of the present disclosure,
A calculation unit of the airflow measuring device,
extracting light reflected by the virtual surface based on a time delay between when an irradiating device irradiates light onto a virtual surface in the atmosphere that intersects with an optical axis of the light and when a light receiving device receives reflected light of the light;
creating a reflected light map showing a pattern of the intensity of the reflected light by plotting the intensity of the reflected light in each grid area of a map corresponding to the virtual surface and including a plurality of grid areas;
Calculating changes in the pattern of a plurality of the reflected light maps;
The optical system is operated to measure the speed of airflow on the imaginary surface in a direction intersecting the optical axis based on the change in the pattern.

The present disclosure makes it possible to accurately and appropriately calculate the airflow speed in an airspace required for an aircraft to avoid turbulence.

Note that the effects described here are not necessarily limited to those described herein and may be any of the effects described in this disclosure.

1 shows an aircraft equipped with an airflow measuring device according to an embodiment of the present disclosure. The configuration of the airflow measuring device is shown. 4 shows the operation flow of the airflow measuring device. An example of the map is shown below. 13A and 13B show schematic diagrams of changes in patterns of a plurality of inspection sections extracted from a plurality of reflected light maps, respectively.

Embodiments of the present disclosure will be described below with reference to the drawings.

1. Overview of aircraft equipped with airflow measurement equipment

Figure 1 shows an aircraft equipped with an airflow measurement device according to one embodiment of the present disclosure.

The airflow measurement device 100 is mounted on an aircraft 1. The aircraft 1 may be, for example, an unmanned aircraft, a small aircraft, a large passenger aircraft, an electric aircraft, etc. The airflow measurement device 100 has an illumination and light receiving device 2. The illumination and light receiving device 2 is provided under the nose of the aircraft 1. The illumination and light receiving device 2 illuminates laser light and receives reflected light. The airflow measurement device 100 is a type of LiDAR (Light Detection and Ranging) device that uses light to remotely measure the speed of airflow.

2. Configuration of the airflow measurement device

Figure 2 shows the configuration of the airflow measurement device.

The airflow measurement device 100 has an irradiation and light receiving device 2, a processing device 130, a storage device 140, and a display device 150. The irradiation and light receiving device 2 has an irradiation device 110 and a light receiving device 120. The irradiation device 110 is an optical system having a laser oscillation device 111 and a scanning device 112. The processing device 130 operates as a calculation device 131 and an arithmetic device 132 by the processor loading an information processing program (including an airflow measurement program) stored in the ROM into the RAM and executing it. The storage device 140 is a large-capacity non-volatile storage medium, such as an HDD or SSD. The display device 150 is a display in the cockpit, and displays a speed display screen 151.

3. Airflow measurement device operation flow

Figure 3 shows the operational flow of the airflow measuring device.

Step S201: Set N=1 and delay time T

The calculation device 132 sets N=1 and a reference delay time T. N is the number of times that the irradiation device 110 irradiates the virtual surface in the atmosphere with light. N=1 means the first irradiation, and also means the first operation flow. The reference delay time T is the length of time delay from when the irradiation device 110 irradiates light for the N=1st time until the light receiving device 120 receives the reflected light. In other words, the delay time when N=1 (i.e., when the first irradiation is performed) is T.

The length of the delay time varies depending on the distance L from the aircraft 1 to the atmosphere, the object of speed measurement. The length of the delay time from illumination to reception is 2L/C, where C is the speed of light and L is the distance from the aircraft 1 to the atmosphere, the object of speed measurement. As the aircraft 1 continues to move forward, the distance L from the aircraft 1 to the atmosphere, the object of speed measurement, gradually becomes smaller, and accordingly, the length of the delay time gradually becomes shorter.

Step S202: Irradiate laser light

The irradiation device 110 irradiates light onto a virtual surface 6 in the atmosphere (see FIG. 1). The virtual surface 6 in the atmosphere contains the air, the object of which is to be measured for speed. Specifically, the laser oscillation device 111 of the irradiation device 110 includes a light source that oscillates laser light. The scanning device 112 of the irradiation device 110 controls the irradiation direction of the laser light oscillated by the laser oscillation device 111, and scans the virtual surface 6 with the laser light. The irradiation device 110 periodically scans the virtual surface 6 at a scan interval of dt time.

Specifically, the laser oscillator 111 optically shapes the laser light into a rectangle so that the virtual surface 6 can be irradiated without gaps, and the cross-sectional shape of the laser light matches the rectangular area of the angle of view. The scanning device 112 divides the pyramid in front of the aircraft 1 in the direction of travel into a grid of angles of view of 10 to several hundred horizontally and 10 to several hundred vertically, and scans the rectangular area of each angle of view with the laser light. The bottom of the pyramid corresponds to the virtual surface 6. The scanning device 112 swings the laser oscillator 111 left and right with a polygon mirror or the like, and changes the intensity of the laser light in a pulsed manner at the moment when the laser oscillator 111 is accurately directed toward the rectangular area of the angle of view. By repeating this, the scanning device 112 scans the entire rectangular area of the virtual surface 6 with the laser light. This allows the laser light to irradiate the entire area of the virtual surface 6 evenly in a short time.

The apex angles θ ₁ and θ ₂ of the quadrangular pyramid are, for example, 0.1 degrees or more and 5 degrees or less, more specifically, each is 1 degree. The scanning device 112 scans the laser light in the range of the left-right angle θ ₁ and the up-down angle θ _2. For example, the scanning device 112 scans the laser light from the top left vertex of the virtual surface 6 to the top right vertex in the range of the left-right angle θ _1. Next, the scanning device 112 lowers the up-down angle θ ₂ by one lattice step and scans the laser light from left to right in the range of the left-right angle θ _1. The scanning device 112 repeats this process to irradiate the light over the entire virtual surface 6. The distance from the aircraft 1 to the virtual surface 6 is L.

The virtual plane 6 intersects with the optical axes of all the irradiated light. In particular, the virtual plane 6 is perpendicular to the optical axis of the light irradiated to one point (e.g., the center point) on the virtual plane 6. The virtual plane 6 includes a flight path that the aircraft 1 is scheduled to pass through during flight. For example, the flight path that the aircraft 1 is scheduled to pass is perpendicular to the center point or near the center point on the virtual plane 6. The virtual plane 6 includes a flight path for the aircraft 1 to avoid turbulence when turbulence exists on the virtual plane 6. For example, the virtual plane 6 is a square with one side of 10 km. If the virtual plane 6 is a square with one side of 10 km, when turbulence exists at the center of the virtual plane 6 (i.e., the planned flight path), the aircraft 1 can avoid the turbulence and fly in a safe airspace (i.e., no turbulence exists) within the virtual plane 6.

Step S203: Receive laser light

The light receiving device 120 receives the light emitted by the irradiation device 110 that is reflected from aerosols (dust, fine particles) in the atmosphere.

Step S204: Calculate the time delay

The calculation device 131 calculates the time delay between when the irradiation device 110 irradiates light into the atmosphere and when the light receiving device 120 receives the reflected light. The time delay between when the light is irradiated and when the light is received varies depending on the distance from the aircraft 1 to the reflection source (dust, etc.).

The calculation device 131 further calculates the amount of Doppler shift in frequency between the light irradiated from the irradiation device 110 and the reflected light reflected on the virtual surface 6 and received by the light receiving device 120.

The calculation device 131 extracts only the reflected light reflected on the virtual surface 6 based on the calculated time delay (i.e., the reflected light with a time delay of 2L/C). If N=1st irradiation, the calculation device 131 extracts only the reflected light with a time delay of T. The calculation device 131 records the intensity of the extracted reflected light, the amount of Doppler shift, and the position information on the virtual surface 6 in the storage device 140. The position information indicates the grid of the angle of view on the virtual surface 6 where the reflected light is reflected. The intensity is, for example, luminance. Note that if the storage device 140 has a sufficient storage capacity, the calculation device 131 may further store the intensity, the amount of Doppler shift, and the position information of reflected light with other time delays, in addition to the reflected light reflected on the virtual surface 6.

In addition, in the Nth flow, the calculation device 131 extracts reflected light with a time delay of T-(N-1)dt. N is incremented (+1) each time the operation flow loops. Therefore, the calculation device 131 continues to extract reflected light that returns in a shorter time each time the operation flow loops. The length of the delay time is changed depending on the distance L from the aircraft 1 to the virtual surface 6. In other words, the distance L becomes smaller as the aircraft 1 approaches the virtual surface 6, and therefore the length of the delay time also becomes shorter. By continuing to extract reflected light that returns in a shorter time, the calculation device 131 can continue to extract reflected light reflected by the virtual surface 6 at the same position in the atmosphere, regardless of changes in the position of the aircraft 1. In this way, the calculation device 131 varies the time delay of the extracted reflected light each time the aircraft 1 irradiates light from a different position on the flight path during flight.

Step S205: Create a reflected light map

Figure 4 shows an example of a map.

The map corresponds to the virtual surface 6 and includes a plurality of grid areas. The grid areas refer to each area obtained by dividing the map into a lattice shape using vertical and horizontal grid lines. The map includes, for example, 18×18 (left and right division number N ₁ × top and bottom division number N ₂ ) grid areas. The entire map corresponds to the virtual surface 6. The size (horizontal × vertical) of one grid area is (Lθ ₁ /N ₁ ) × (Lθ ₂ /N ₂ ). The grid areas included in the map may or may not match one-to-one with the rectangle of the view angle of the virtual surface 6. As long as the rectangle of the view angle of the virtual surface 6 can be converted into a grid area included in the map, any correspondence relationship between the map and the virtual surface 6 is acceptable.

The arithmetic device 132 reads out the intensity of the reflected light reflected by the virtual surface 6 and the position information from the storage device 140. The arithmetic device 132 plots the intensity of the reflected light in a grid area corresponding to the position information of the virtual surface 6. Specifically, the arithmetic device 132 quantizes the intensity of the reflected light and plots the quantized intensity in the grid area. In the example of the same figure, a dark grid area indicates a high intensity of the reflected light, a light grid area indicates a low intensity of the reflected light, and a white grid area indicates that there is no reflected light with an intensity above the threshold. In this way, the arithmetic device 132 creates a reflected light map 3 that indicates the pattern of the intensity of the reflected light reflected by the virtual surface 6.

In the Nth flow, the calculation device 132 creates a reflected light map 3 of the intensity of reflected light with a time delay of T-(N-1)dt. Each time the operation flow loops, N is incremented (+1). Therefore, the calculation device 132 continues to create a reflected light map 3 of reflected light that returns in a shorter time each time the operation flow loops. The length of the delay time is changed depending on the distance L from the aircraft 1 to the virtual surface 6. In other words, the distance L becomes smaller as the aircraft 1 approaches the virtual surface 6, so the length of the delay time also becomes shorter. By continuing to create a reflected light map 3 of reflected light that returns in a shorter time, the calculation device 132 can continue to create a reflected light map 3 corresponding to the virtual surface 6 at the same position in the atmosphere, regardless of changes in the position of the aircraft 1. In this way, the calculation device 132 corrects the positions in the optical axis direction of the multiple reflected light maps 3 by varying the time delay of the reflected light for each of the multiple reflected light maps 3 corresponding to light irradiated from different positions on the flight path while the aircraft 1 is flying.

In step S204 or S205, the calculation device 131 or the arithmetic device 132 may correct the time delay deviation according to the deviation in the irradiation timing caused by scanning the virtual surface 6 with the laser light. As described above, the irradiation device 110 does not irradiate the entire virtual surface 6 at once, but irradiates the entire virtual surface 6 with the laser light by sequentially scanning the entire virtual surface 6. Therefore, strictly speaking, there is a time deviation in the irradiation timing from the rectangular area of the angle of view that is scanned first (e.g., including the upper left vertex) to the rectangular area of the angle of view that is scanned last (e.g., including the lower right vertex). Therefore, the position of the aircraft 1 is strictly different from the timing of the first scan to the timing of the last scan. Therefore, depending on the time deviation in the irradiation timing, the virtual surface 6 may become distorted in a direction including a component of the traveling direction (i.e., inclined with respect to the traveling direction) rather than perpendicular to the traveling direction (i.e., the optical axis direction of the center of the virtual surface 6). The calculation device 131 or the arithmetic device 132 may correct the time delay deviation according to such deviation in irradiation timing, so that the virtual surface 6 becomes a surface perpendicular to the direction of travel. However, depending on the scanning speed performance of the irradiation device 110, the distance to the virtual surface 6, the computation performance of the calculation device 131 or the arithmetic device 132, etc., it is not necessary to correct the time delay deviation according to the deviation in irradiation timing.

Step S206: Compare reflected light maps

The calculation device 132 chronologically compares the reflected light map 3 created last time with the reflected light map 3 created this time after dt time has passed. That is, it compares the reflected light map 3 created last time (i.e., the N-1th time) (time delay: T-Ndt) with the reflected light map 3 created this time (i.e., the Nth time) (time delay: T-(N-1)dt). Specifically, the calculation device 132 calculates the change in the pattern by comparing the pattern of the reflected light intensity of the reflected light map 3 created last time with the pattern of the reflected light intensity of the reflected light map 3 created this time after dt time has passed.

Specifically, the calculation device 132 divides each of the previous reflected light map 3 and the current reflected light map 3 into multiple inspection sections 4. The layout for dividing the previous reflected light map 3 and the current reflected light map 3 into multiple inspection sections 4 is the same.

The number of grid areas included in the inspection section 4 (in other words, the size of the inspection section 4) may be fixed or variable. If emphasis is placed on reducing the computational load and the pilot's human workload, the number may be fixed. If emphasis is placed on the accuracy of the computation, the number may be variable. In the case of a fixed number, the inspection section 4 may be, for example, a rectangle including 8 x 8 grid areas. In the case of a variable number, the inspection section 4 may be extracted so that the number of grid areas (i.e., non-white grid areas) in which the intensity of reflected light included in the inspection section 4 is plotted is, for example, several or more and several tens or less. The number of grid areas in which the intensity of reflected light included in the inspection section 4 is plotted may be, for example, five or more and several tens or less. By appropriately setting the number of grid areas in which the intensity of reflected light is plotted, the change in the pattern of the multiple inspection sections 4 can be calculated more accurately.

The calculation device 132 extracts inspection sections 4 corresponding to the same area on the virtual surface 6 from each of the multiple reflected light maps 3 (i.e., the previous reflected light map 3 and the current reflected light map 3). The calculation device 132 calculates the change in the pattern of the multiple reflected light maps 3 by calculating the change in the pattern of the multiple inspection sections 4 extracted from each of the multiple reflected light maps 3.

Figure 5 shows a schematic diagram of the changes in the patterns of multiple inspection sections extracted from multiple reflected light maps.

The left image shows one inspection section 4 divided from the previous reflected light map 3 (same as inspection section 4 in Figure 4). The right image shows one inspection section 4' divided from the reflected light map 3 after the passage of time dt. The positions (coordinates) of inspection section 4 and inspection section 4' in the reflected light map 3 are the same.

Step S207: Measure the direction and speed of airflow on the virtual surface

The arithmetic device 132 measures the direction and speed of the airflow on the virtual surface 6 based on the change from the pattern of reflected light of the previous inspection section 4 to the pattern of reflected light of the current inspection section 4'. The direction and speed of the airflow on the virtual surface 6 measured by the arithmetic device 132 are the direction and speed of the airflow in the surface direction of the virtual surface 6. As described above, the virtual surface 6 intersects with the optical axes of all the irradiated light, and is perpendicular to the optical axis of the light irradiated to one point (e.g., the center point) on the virtual surface 6. Also, for example, the flight path that the aircraft 1 is scheduled to pass through is perpendicular to the center point or near the center point on the virtual surface 6. In this case, the direction and speed of the airflow measured by the arithmetic device 132 are the speed of the airflow in a direction perpendicular to the planned flight path (i.e., a direction including vertical and horizontal components).

Specifically, the arithmetic device 132 calculates a cross-correlation function from the pattern of reflected light of the previous inspection section 4 and the pattern of reflected light of the current inspection section 4', calculates a movement vector that gives the maximum value, and calculates the speed. In the example of FIG. 5, the pattern of reflected light of the previous inspection section 4 is moved one to the right and two to the downward direction, and the cross-correlation with the pattern of reflected light of the inspection section 4' after dt time has elapsed is obtained to obtain the maximum value. Therefore, the arithmetic device 132 estimates that the air has moved by Lθ ₁ /N ₁ to the right on the virtual surface 6 and by 2Lθ ₂ /N ₂ to the downward direction on the virtual surface 6 during the time dt. Therefore, the arithmetic device 132 measures the speed of the airflow to be Lθ ₁ /N ₁ /dt to the right on the virtual surface 6 and 2Lθ ₂ /N ₂ /dt to the downward direction on the virtual surface 6. This allows the arithmetic device 132 to measure the direction and speed of the airflow.

Step S208: Measure the airflow speed in the direction of travel

The arithmetic device 132 reads the Doppler shift amount of the reflected light reflected by the virtual surface 6 and the position information from the storage device 140. The arithmetic device 132 measures the airflow speed in the direction of the optical axis on the virtual surface 6 (i.e., the traveling direction of the aircraft 1) based on the Doppler shift amount. According to this embodiment, the reflected light used to measure the airflow speed in the surface direction of the virtual surface 6 can also be used to measure the airflow speed in the traveling direction of the aircraft 1.

The computing device 132 displays a speed display screen 151 on the display device 150 (e.g., a display in the cockpit). The speed display screen 151 is a GUI that displays the measured airflow speed in the surface direction of the virtual surface 6 and the airflow speed in the traveling direction.

Step S209: Loop

If the number of scans N does not exceed the threshold (step S209, NO), the calculation device 132 increments the number of scans N by 1 and causes the irradiation device 110 to irradiate the laser light for the N+1th time (step S202). On the other hand, if the number of scans N exceeds the threshold (step S209, YES), the calculation device 132 sets a new N=1 and a reference delay time T (step S201), and then causes the irradiation device 110 to irradiate the laser light for the Nth time (step S202).

As described above, when turbulence exists on the virtual plane 6, it is desirable for the aircraft 1 to avoid the turbulence and fly in a safe airspace (i.e., no turbulence exists) within the virtual plane 6. Therefore, the distance from the aircraft 1 to the virtual plane 6 must be a distance that allows the aircraft 1 to avoid the turbulence on the virtual plane 6. For this reason, a threshold (upper limit) for the number of scans N is set. When the number of scans N exceeds the threshold, the computing device 132 sets a new reference delay time T. The distance L to the virtual plane 6 is newly defined depending on the delay time T. For this reason, by setting a new reference delay time T, it is possible to detect and measure turbulence on a new virtual plane 6. As a result, the airflow measuring device 100 can always continue to detect and measure turbulence on the virtual plane 6 that is a predetermined distance away (i.e., a distance that allows turbulence to be avoided).

4. Differences from particle image velocimetry (PIV)

Particle Image Velocimetry (PIV) is known as a method for measuring the flow direction and speed of a fluid. The method for measuring the direction and speed of the airflow on the virtual surface 6 (step S207) has many differences from PIV, but also has advantages over PIV. These differences will be explained below.

In PIV, tracer particles such as aluminum powder are seeded into a flow field (for example, a wind tunnel or circulating water tank in a laboratory). A laser light sheet (i.e., sheet-shaped laser light) is irradiated from above toward the flow field. The laser light sheet is irradiated so that the surface direction of the light sheet coincides with the direction of the fluid flow (i.e., the direction of the flow whose speed is to be detected). A CCD or CMOS camera is used to capture images of the tracer particles irradiated onto the laser light sheet multiple times over time from a direction perpendicular to the laser light sheet. The patterns of the tracer particles contained in the multiple particle images captured over time are analyzed to measure the movement speed of the tracer particles, i.e., the speed of the fluid. This is an overview of PIV.

PIV seeds tracer particles into a flow field and irradiates the flow field with a laser light sheet from above. In contrast, when measuring air currents that aircraft 1 may encounter, it is not possible to seed tracer particles into an airspace away from aircraft 1 and irradiate the airspace with a laser light sheet from above. This is a prerequisite for this embodiment.

PIV needs to capture good particle images suitable for image analysis. For this reason, it is necessary to appropriately control the particle size of the tracer particles and the particle density in the flow field. In contrast, when measuring airflows that aircraft 1 may encounter, it is not possible to control the particle size or particle density of atmospheric aerosols (dust, fine particles) that serve as substitutes for tracer particles. In addition, the distance from aircraft 1 to the atmosphere, whose speed is to be measured, is much greater than the distance from the camera to the light sheet in PIV. For this reason, it is extremely difficult to capture images of dust and other particles in the atmosphere in airspace away from aircraft 1 at a level suitable for image analysis from aircraft 1.

In view of the above circumstances, according to this embodiment, the airflow measurement device 100 calculates the time delay of the reflected light from irradiation to reception, extracts the reflected light reflected from the virtual surface 6 perpendicular to the planned flight path based on the time delay, and creates a reflected light map 3 showing the pattern of the intensity of the reflected light reflected from the virtual surface 6. This makes it possible to create a reflected light map 3 of the reflected light reflected from the virtual surface 6 having a surface direction that matches the direction of the flow whose speed is to be detected. In other words, it is possible to create a reflected light map 3 that can analyze the flow direction and speed in the same way as a particle image of PIV. In PIV, the distribution of tracer particles is analyzed based on particle density, but in this embodiment, the distribution of dust can be analyzed based on the intensity of the reflected light instead of particle density.

PIV shines a laser light sheet and captures only the tracer particles illuminated by the laser light sheet (i.e., distributed within the laser light sheet). Laser light sheets always have a physical thickness. For this reason, tracer particles distributed not only in the surface direction of the laser light sheet but also in the thickness direction of the laser light sheet are captured. In other words, tracer particles distributed not only in the surface direction of the laser light sheet but also in the thickness direction of the laser light sheet are included in the particle image. For this reason, PIV may not be able to accurately measure the airflow speed only in the surface direction of the laser light sheet.

In contrast, the airflow measurement device 100 of this embodiment extracts only the reflected light received with a specific delay time, making it possible to extract only the reflected light reflected by the virtual surface 6, which has no physical thickness. As a result, the airflow measurement device 100 of this embodiment can accurately measure the airflow speed only in the surface direction of the virtual surface 6.

When the size of the aerosol is 0, the probability that the aerosol exists on the virtual surface 6 is 0. If the aerosol has a size (characteristic length d), the probability of its existence increases in proportion to d. If the time delay T is given a time width dt', the aerosol will be detected within a rectangular parallelepiped whose area S of the virtual surface 6 is added to a thickness of dt'C, and even if the size d of the aerosol is 0, the probability of its existence will be finite. Since the density of aerosols at high altitudes is very low, a time width dt' can be set for detecting the aerosol.

5. Conclusion

According to this embodiment, the airflow measurement device 100 calculates the time delay of the reflected light from irradiation to reception, extracts the reflected light reflected from a virtual surface 6 perpendicular to the planned flight path based on the time delay, and creates a reflected light map 3 that shows the intensity pattern of the reflected light reflected from the virtual surface 6. This makes it possible to create a reflected light map 3 of the reflected light reflected from a virtual surface 6 having a surface direction that matches the direction of the flow whose speed is to be detected. By creating multiple reflected light maps 3 that are different in time, it is possible to measure the speed of the airflow in the surface direction of the virtual surface 6.

By orienting the surface direction of the virtual surface 6 perpendicular to the planned flight path, it is possible to measure the air current speed in a direction perpendicular to the planned flight path (i.e., a direction including vertical and horizontal components). In particular, it is possible to measure the vertical speed of clear air turbulence. Furthermore, by appropriately setting the size of the virtual surface 6, it is possible to accurately and appropriately calculate the air current speed in the airspace required for the aircraft 1 to avoid turbulence.

In addition, in this embodiment, the reflected light map 3 of the light reflected by the virtual surface 6 at the same position in the atmosphere is continuously created, regardless of the change in the position of the aircraft 1 (steps S204 and S205). As a modified example, if the reflected light map 3 of the light reflected by the virtual surface 6 at a different position relative to the traveling direction is created depending on the change in the position of the aircraft 1, it is also possible to measure the speed of the air current in a direction that includes a component in the traveling direction.

In this embodiment, it is only necessary to mount the minimum amount of hardware, the laser oscillator 111 and the light receiving device 120, on the aircraft 1, and the processing device 130 measures the airflow speed in the surface direction of the virtual surface 6 through software processing based on the reflected light received by the light receiving device 120. It is also possible to simultaneously detect the airflow speed in the direction of travel based on the amount of Doppler shift.

The airflow measuring device 100 can be applied not only to the aircraft 1 but also to ground equipment. The airflow measuring device 100 mounted on the aircraft 1 may transmit the airflow measured by the airflow measuring device 100 to ground equipment or other aircraft. The airflow measuring device 100 can also be mounted on ships and vehicles.

Although the embodiments and variations of the present technology have been described above, the present technology is not limited to the above-described embodiments, and various modifications can of course be made without departing from the spirit of the present technology.

REFERENCE SIGNS LIST 1 Aircraft 2 Illumination and light receiving device 3 Reflected light map 4 Inspection section 5 Grid area 6 Virtual surface 100 Airflow measurement device 110 Illumination device 111 Laser oscillation device 112 Scanning device 120 Light receiving device 130 Processing device 131 Calculation device 132 Arithmetic device 140 Storage device 150 Display device 151 Speed display screen

Claims (15)

Calculating a time delay from when an irradiating device irradiates light onto a virtual surface in the atmosphere that intersects with an optical axis of the light until when a light receiving device receives reflected light of the light;
A calculation device that extracts the reflected light reflected by the virtual surface based on the time delay;
creating a reflected light map showing a pattern of the intensity of the reflected light by plotting the intensity of the reflected light in each grid area of a map corresponding to the virtual surface and including a plurality of grid areas;
Calculating a change in the pattern between the reflected light map and a reflected light map created after a predetermined time has elapsed;
and a calculation device that measures the speed of the airflow on the virtual surface in a direction intersecting the optical axis based on the change in the pattern. The airflow measurement device according to claim 1,
the virtual surfaces corresponding to the plurality of reflected light maps are at the same position in the atmosphere;
The airflow measuring device, wherein the calculation device measures the speed of the airflow in a planar direction of the virtual surface as a direction intersecting the optical axis. The airflow measuring device according to claim 1 or 2,
The virtual plane is perpendicular to an optical axis of light irradiated to one point on the virtual plane. The airflow measuring device according to any one of claims 1 to 3,
The airflow measuring device is an airflow measuring device mounted on an aircraft. The airflow measuring device according to claim 4,
The virtual surface includes a flight path along which the aircraft is scheduled to fly. The airflow measuring device according to claim 4 or 5,
An airflow measurement device, wherein the virtual plane includes a flight path along which the aircraft will fly to avoid turbulence when turbulence exists on the virtual plane. The airflow measuring device according to any one of claims 4 to 6,
The calculation device varies the time delay of the extracted reflected light each time the light is irradiated from a different position on a flight path while the aircraft is flying. The airflow measuring device according to any one of claims 1 to 7,
The computing device includes:
Extracting inspection sections from the plurality of reflected light maps, each of which corresponds to a same area on the virtual surface;
Calculating changes in the patterns of the plurality of inspection sections extracted from the plurality of reflected light maps, respectively;
An airflow measurement device that calculates changes in the patterns of the plurality of reflected light maps. The airflow measurement device according to claim 8,
The number of the grid areas included in the inspection section is variable;
The number of grid areas in which the intensity of reflected light is plotted and included in the inspection section is between several and several tens. The airflow measuring device according to any one of claims 1 to 9,
The irradiation device includes:
a laser oscillation device that oscillates a laser beam having a cross-sectional shape identical to that of an area obtained by dividing the imaginary surface;
and a scanning device that controls an irradiation direction of the laser light and scans all areas of the virtual surface with the laser light. The airflow measurement device according to claim 10 ,
The calculation device or the arithmetic device corrects a time delay deviation in accordance with a deviation in irradiation timing caused by scanning the virtual surface with the laser light. The airflow measuring device according to any one of claims 1 to 11,
The calculation device further calculates a Doppler shift amount of a frequency between the irradiated light and the reflected light reflected by the virtual surface,
The calculation device further measures a speed of the airflow in the direction of the optical axis on the virtual plane based on the amount of Doppler shift. The airflow measuring device according to any one of claims 1 to 12,
The irradiation device;
The airflow measuring device further comprises the light receiving device. extracting light reflected by the virtual surface based on a time delay between when an irradiating device irradiates light onto a virtual surface in the atmosphere that intersects with an optical axis of the light and when a light receiving device receives reflected light of the light;
creating a reflected light map showing a pattern of the intensity of the reflected light by plotting the intensity of the reflected light in each grid area of a map corresponding to the virtual surface and including a plurality of grid areas;
Calculating a change in the pattern between the reflected light map and a reflected light map created after a predetermined time has elapsed;
based on the change in the pattern, measuring a speed of the airflow on the virtual surface in a direction intersecting the optical axis. A calculation unit of the airflow measuring device,
extracting light reflected by the virtual surface based on a time delay between when an irradiating device irradiates light onto a virtual surface in the atmosphere that intersects with an optical axis of the light and when a light receiving device receives reflected light of the light;
creating a reflected light map showing a pattern of the intensity of the reflected light by plotting the intensity of the reflected light in each grid area of a map corresponding to the virtual surface and including a plurality of grid areas;
Calculating a change in the pattern between the reflected light map and a reflected light map created after a predetermined time has elapsed;
an airflow measurement program that operates to measure the speed of airflow on the virtual surface in a direction intersecting the optical axis based on the change in the pattern.

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