Airflow measurement device, airflow measurement method, and airflow measurement program

Abstract

To precisely and appropriately calculate an airflow speed in airspace required for an aircraft to avoid air turbulence.SOLUTION: An airflow measuring device includes: a calculation device for calculating time delay after an irradiation device applies the light to a virtual surface in the atmosphere crossing a light axis of the light until a light receiving device receives reflection light of the light, and for extracting reflection light reflected by the virtual surface on the basis of the time delay; and an arithmetic unit for creating a reflection light map for showing an intensity pattern of the reflection light by plotting intensity of the reflection light in each grid area of a map including a plurality of grid areas in accordance with the virtual surface, for computing a change in the pattern between the reflection light map, and a reflection light map created after a lapse of predetermined time, and for measuring speed of an airflow in a direction crossing the light axis on the virtual surface on the basis of a change in the pattern.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an airflow measuring device, an airflow measuring method, and an airflow measuring program used to detect turbulence encountered by, for example, an aircraft. [Background technology]

[0002] Clear air turbulence, which is a 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, mainly 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 the aircraft. It is desirable to detect turbulence of this scale and large energy and navigate by avoiding it.

[0003] When an aircraft enters turbulence, it shakes violently and repeatedly ascends and descends rapidly, which places a large load on the aircraft and, in the worst case, can cause destruction. In addition, there are several accidents every year in which passengers and crew are injured, some seriously, because the seatbelt sign was not issued sooner. In addition to reducing the burden on the aircraft, turbulence can affect the comfort of the aircraft, such as in-flight service and passenger comfort, and can also affect the bodies and lives of passengers and crew, so when pilots notice turbulence ahead, they must avoid it as much as possible.

[0004] In Patent Document 1, a laser beam is projected 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, a laser beam is projected 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. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-67680 A Summary of the Invention [Problem to be solved by the invention]

[0006] The vertical air current 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 air current speed calculated is not the air current speed on the flight path that the aircraft is scheduled to pass through, but the air current speed in the area above and below the airspace that the aircraft is scheduled to pass through. For this reason, there is a risk that the air current speed in the airspace required for the aircraft to avoid turbulence cannot be calculated appropriately.

[0007] In consideration of the above circumstances, an object of the present disclosure is to provide an airflow measuring device, an airflow measuring method, and an airflow measuring program that are capable of accurately and appropriately calculating the airflow speed in an airspace required for an aircraft to avoid turbulence. [Means for solving the problem]

[0008] 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; Based on the time delay, the reflected light reflected by the virtual surface is extracted. A calculation device; 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, the speed of the airflow on the virtual surface in a direction intersecting the optical axis is measured. A computing device Equipped with:

[0009] 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 by a virtual surface intersecting the optical axis of the light based on the time delay, and creates a reflected light map showing the intensity pattern of the reflected light reflected by the virtual surface. This makes it possible to create a reflected light map of the reflected light reflected by the virtual surface having a surface direction that coincides with the direction of the flow whose speed is to be detected.

[0010] 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.

[0011] 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 surface.

[0012] The imaginary plane may be perpendicular to an optical axis of light that is irradiated to a point on the imaginary plane.

[0013] According to this embodiment, it is possible to measure the speed of airflow in a planar direction perpendicular to the optical axis of light.

[0014] The airflow measurement device may be installed on an aircraft.

[0015] According to this embodiment, it is possible to measure the speed of air currents in a plane direction perpendicular to the optical axis of light emitted from the aircraft.

[0016] The virtual surface may include a flight path along which the aircraft is intended to fly.

[0017] 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 pass. 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.

[0018] The virtual surface may include a flight path that the aircraft will fly to avoid turbulence if turbulence is present on the virtual surface.

[0019] According to this embodiment, if turbulence is present on a planned flight path on a virtual surface, the aircraft is able to avoid the turbulence and fly in safe (i.e., turbulence-free) airspace within the virtual surface.

[0020] The calculation device may vary the time delay of the extracted reflected light each time the aircraft irradiates light from a different position on a flight path while in flight.

[0021] The length of the delay time is changed depending on the distance from the aircraft to the virtual surface. In other words, the distance becomes smaller as the aircraft approaches the virtual surface, and therefore the length of the delay time becomes shorter. By continuing to extract the reflected light that returns in a shorter time, the calculation device can continue to extract the reflected light that is reflected by the virtual surface at the same position in the atmosphere, regardless of the position of the aircraft.

[0022] 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.

[0023] By appropriately setting the number of grid areas in which the intensity of reflected light is plotted, the change in the pattern of a plurality of inspection sections can be calculated more accurately.

[0024] 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.

[0025] The number of grid areas may be fixed if emphasis is placed on reducing the computational load and the pilot's physical load, or may be variable if emphasis is placed on accuracy of computation.

[0026] 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; a scanning device that controls an irradiation direction of the laser light to scan all areas of the virtual surface with the laser light; may have the following structure:

[0027] This allows the laser light to be irradiated evenly over the entire virtual surface in a short period of time.

[0028] The calculation device or the arithmetic device may correct a time delay deviation in accordance with a deviation in irradiation timing caused by scanning the virtual surface with the laser light.

[0029] The irradiation device does not irradiate the entire area of ​​the virtual surface at once, but irradiates the entire area of ​​the virtual surface with laser light by scanning the entire area of ​​the 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 become distorted in a direction including a component of the traveling direction (i.e., inclined with respect to the traveling direction) instead of being perpendicular to the traveling direction (i.e., the optical axis direction of the center of the virtual surface). The calculation device or the 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.

[0030] 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.

[0031] 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 speed of the airflow in the direction of the optical axis on the virtual surface (i.e., the traveling direction of the aircraft) based on the Doppler shift amount. According to this embodiment, the reflected light used to measure the speed of the airflow in the planar direction of the virtual surface can also be used to measure the speed of the airflow in the traveling direction of the aircraft.

[0032] The airflow measuring device may further include the irradiation device and the light receiving device.

[0033] In this embodiment, the aircraft is equipped with only the minimum hardware, that is, a laser oscillator and a light receiving device, and the processing device measures the airflow speed in the surface direction of the virtual surface by software processing based on the reflected light received by the light receiving device. At the same time, it is also possible to detect the airflow speed in the direction of travel based on the amount of Doppler shift.

[0034] 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.

[0035] 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; 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. Make it work like this. Effect of the Invention

[0036] According to the present disclosure, it is possible to accurately and appropriately calculate the airflow speed in an airspace required for an aircraft to avoid turbulence.

[0037] Note that the effects described herein are not necessarily limited to those described herein, and may be any of the effects described in this disclosure. [Brief description of the drawings]

[0038] [Figure 1] 1 shows an aircraft equipped with an airflow measuring device according to an embodiment of the present disclosure. [Diagram 2] The configuration of the airflow measuring device is shown. [Diagram 3] 4 shows the operation flow of the airflow measuring device. [Figure 4] An example of a map is shown. [Diagram 5] 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0040] 1. Overview of the aircraft equipped with the airflow measurement device

[0041] FIG. 1 shows an aircraft equipped with an airflow measuring device according to an embodiment of the present disclosure.

[0042] The airflow measuring device 100 is mounted on an aircraft 1. The aircraft 1 is, for example, an unmanned aircraft, a small aircraft, a large passenger aircraft, an electric aircraft, etc. The airflow measuring 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 measuring device 100 is a type of LiDAR (Light Detection And Ranging) device that uses light to remotely measure the speed of airflow.

[0043] 2. Configuration of the airflow measurement device

[0044] FIG. 2 shows the configuration of the airflow measuring device.

[0045] The airflow measurement device 100 includes 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 includes an irradiation device 110 and a light receiving device 120. The irradiation device 110 is an optical system including 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.

[0046] 3. Operation flow of the airflow measurement device

[0047] FIG. 3 shows the operation flow of the airflow measuring device.

[0048] Step S201: Set N=1 and delay time T

[0049] The arithmetic device 132 sets N=1 and a reference delay time T. N is the number of times that the irradiation device 110 irradiates a 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 of delay from when the irradiation device 110 irradiates light for the first time (N=1) 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.

[0050] 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.

[0051] Step S202: Irradiate laser light

[0052] 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 speed of which is to be measured. Specifically, a laser oscillation device 111 of the irradiation device 110 includes a light source that oscillates laser light. A scanning device 112 of the irradiation device 110 controls the irradiation direction of the laser light oscillated by the laser oscillation device 111 to scan 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.

[0053] Specifically, the laser oscillation device 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 is made to match the rectangular area of ​​the angle of view. The scanning device 112 divides the quadrangular pyramid in front of the direction of travel of the aircraft 1 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 surface of the quadrangular pyramid corresponds to the virtual surface 6. The scanning device 112 swings the laser oscillation device 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 oscillation device 111 is accurately directed toward the rectangular area of ​​the angle of view. By repeating this, the scanning device 112 scans all the rectangular areas 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.

[0054] The apex angles θ1 and θ2 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 θ1 and the up-down angle θ2. 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 θ1. Next, the scanning device 112 lowers the up-down angle θ2 by one lattice step and scans the laser light from left to right in the range of the left-right angle θ1. The scanning device 112 repeats this to irradiate the light over the entire virtual surface 6. The distance from the aircraft 1 to the virtual surface 6 is L.

[0055] The virtual plane 6 intersects with the optical axes of all the irradiated lights. In particular, the virtual plane 6 is perpendicular to the optical axis of the light irradiated to one point (e.g., a 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 through is perpendicular to a center point or a vicinity of a 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 being 10 km long. If the virtual plane 6 is a square with one side being 10 km long, 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.

[0056] Step S203: Receive laser light

[0057] The light receiving device 120 receives the light emitted by the irradiating device 110 and reflected from aerosols (dust, fine particles) in the atmosphere.

[0058] Step S204: Calculate the time delay

[0059] The calculation device 131 calculates the time delay from when the irradiation device 110 irradiates light into the atmosphere to when the reflected light is received by the light receiving device 120. The time delay from irradiation to reception of light varies depending on the distance from the aircraft 1 to the reflection source (dust, etc.).

[0060] The calculation device 131 further calculates the amount of Doppler shift in frequency between the light emitted from the irradiation device 110 and the reflected light reflected on the virtual surface 6 and received by the light receiving device 120 .

[0061] 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 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. 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 position information of reflected light with other time delays, in addition to the reflected light reflected on the virtual surface 6.

[0062] In the Nth flow, the calculation device 131 extracts reflected light with a time delay of T-(N-1)dt. Every time the operation flow loops, N is incremented (+1). Therefore, the calculation device 131 continues to extract reflected light that returns in a shorter time every 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 every time the aircraft 1 irradiates light from a different position on the flight path during flight.

[0063] Step S205: Create a reflection map

[0064] FIG. 4 shows an example of the map.

[0065] 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-right division number N1×up-down division number N2) grid areas. The entire map corresponds to the virtual surface 6. The size (horizontal×vertical) of one grid area is (Lθ1 / N1)×(Lθ2 / N2). 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.

[0066] 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 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 equal to or greater than a threshold. In this way, the arithmetic device 132 creates a reflected light map 3 that indicates a pattern of the intensity of the reflected light reflected by the virtual surface 6.

[0067] In the Nth flow, the arithmetic 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 arithmetic device 132 continues to create a reflected light map 3 of reflected light that has returned 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 create a reflected light map 3 of reflected light that has returned in a shorter time, the arithmetic device 132 can continue to create a reflected light map 3 corresponding to the virtual surface 6 at the same position in the atmosphere, independent of changes in the position of the aircraft 1. In this way, the arithmetic 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.

[0068] In step S204 or S205, the calculation device 131 or the arithmetic device 132 may correct the time delay deviation according to the deviation of 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 area of ​​the virtual surface 6 at once, but irradiates the entire area of ​​the virtual surface 6 with the laser light by sequentially scanning the entire area of ​​the 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 (for example, including the upper left vertex) to the rectangular area of ​​the angle of view that is scanned last (for example, 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 of 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 a deviation in the irradiation timing so that the virtual plane 6 becomes a plane perpendicular to the traveling direction. However, depending on the scanning speed performance of the irradiation device 110, the distance to the virtual plane 6, the arithmetic 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 the irradiation timing.

[0069] Step S206: Compare the reflected light maps

[0070] The arithmetic device 132 chronologically compares the reflected light map 3 created last time with the reflected light map 3 created this time after the lapse of dt time. That is, it compares the reflected light map 3 (time lag: T-Ndt) created last time (i.e., the N-1th time) with the reflected light map 3 (time lag: T-(N-1)dt) created this time (i.e., the Nth time). Specifically, the arithmetic device 132 compares 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 the lapse of dt time, to calculate the change in the pattern.

[0071] Specifically, the arithmetic device 132 divides each of the previous reflected light map 3 and the current reflected light map 3 into a plurality of inspection sections 4. The layout for dividing the previous reflected light map 3 and the current reflected light map 3 into a plurality of inspection sections 4 is the same.

[0072] 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 computation load and the pilot's human workload, the number may be fixed, and 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 8×8 grid areas. In the case of a variable number, the inspection section 4 may be extracted such that the number of grid areas (i.e., non-white grid areas) included in the inspection section 4 on which the intensity of reflected light is plotted is, for example, several or more and several tens or less. The number of grid areas included in the inspection section 4 on which the intensity of reflected light is plotted may be, for example, five or more and several tens or less. By appropriately setting the number of grid areas on which the intensity of reflected light is plotted, the change in the pattern of the multiple inspection sections 4 can be calculated more accurately.

[0073] The arithmetic 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 arithmetic device 132 calculates changes in the patterns of the multiple reflected light maps 3 by calculating changes in the patterns of the multiple inspection sections 4 extracted from the multiple reflected light maps 3, respectively.

[0074] FIG. 5 shows a schematic diagram of changes in the patterns of a plurality of inspection sections extracted from a plurality of reflected light maps, respectively.

[0075] The left diagram shows one inspection section 4 divided from the previous reflected light map 3 (same as the inspection section 4 in FIG. 4). The right diagram shows one inspection section 4' divided from the reflected light map 3 after the lapse of time dt. The positions (coordinates) of the inspection section 4 and the inspection section 4' in the reflected light map 3 are the same.

[0076] Step S207: Measure the direction and speed of airflow on the virtual surface

[0077] 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 lights, and is orthogonal 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 along which the aircraft 1 is scheduled to pass is orthogonal 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 orthogonal to the planned flight path (i.e., a direction including vertical and horizontal components).

[0078] 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 Lθ1 / N1 to the right on the virtual surface 6 and by 2Lθ2 / N2 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 Lθ1 / N1 / dt to the right on the virtual surface 6 and by 2Lθ2 / N2 / 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.

[0079] Step S208: Measure the airflow speed in the direction of travel

[0080] The arithmetic device 132 reads out the position information and the amount of Doppler shift of the light reflected by the virtual plane 6 from the storage device 140. The arithmetic device 132 measures the speed of the airflow in the direction of the optical axis on the virtual plane 6 (i.e., the traveling direction of the aircraft 1) based on the amount of Doppler shift. According to this embodiment, the reflected light used to measure the speed of the airflow in the planar direction of the virtual plane 6 can also be used to measure the speed of the airflow in the traveling direction of the aircraft 1.

[0081] The arithmetic device 132 displays a speed display screen 151 on a display device 150 (for example, a display in a 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.

[0082] Step S209: Loop

[0083] If the number of scans N does not exceed the threshold (step S209, NO), the calculation device 132 increments (+1) the number of scans N 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 newly sets 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).

[0084] As described above, when turbulence exists on the virtual plane 6, it is desired that the aircraft 1 avoids the turbulence and flies 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 delay time T as a reference. A new distance L to the virtual plane 6 is defined depending on the delay time T. For this reason, by setting a new delay time T as a reference, it is possible to detect and measure turbulence on a new virtual plane 6. This allows the airflow measuring device 100 to constantly 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).

[0085] 4. Differences from Particle Image Velocimetry (PIV)

[0086] 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, and also has advantages over PIV. These differences will be explained.

[0087] 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 by 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.

[0088] 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.

[0089] 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 far from aircraft 1 at a level suitable for image analysis from aircraft 1.

[0090] 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 on 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 on the virtual surface 6. This makes it possible to create a reflected light map 3 of the reflected light reflected on the virtual surface 6 having a surface direction that coincides with 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 direction and speed of the flow in the same way as the particle image of PIV. In PIV, the distribution of tracer particles is analyzed based on the particle density, but in this embodiment, the distribution of dust can be analyzed based on the intensity of the reflected light instead of the particle density.

[0091] 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.

[0092] In contrast, airflow measuring device 100 of this embodiment can extract only the reflected light that is received with a specific delay time, and thereby extract only the reflected light that is reflected by virtual surface 6, which has no physical thickness. Therefore, airflow measuring device 100 of this embodiment can accurately measure the airflow speed only in the surface direction of virtual surface 6.

[0093] Incidentally, if the size of the aerosol is 0, the probability that the aerosol exists on the imaginary 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', then the aerosol will be detected within a rectangular parallelepiped whose area S of the imaginary 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. Because the density of aerosols at high altitudes is extremely low, a time width dt' for detecting the aerosol may be set.

[0094] 5. Conclusion

[0095] 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 that indicates 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 the 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 differ in time, it is possible to measure the speed of the airflow in the surface direction of the virtual surface 6.

[0096] 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 the direction perpendicular to the planned flight path (i.e., the direction including vertical and horizontal components). 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 6, it is possible to accurately and appropriately calculate the air current speed in the airspace required for the aircraft 1 to avoid turbulence.

[0097] Furthermore, 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 (steps S204 and S205) regardless of the change in the position of the aircraft 1. As a modified example, if the reflected light map 3 of the light reflected by the virtual surface 6 at a different position with respect 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.

[0098] In this embodiment, it is only necessary to mount the laser oscillator 111 and the light receiving device 120, which are the minimum hardware, on the aircraft 1, and the processing device 130 measures the airflow speed in the surface direction of the virtual surface 6 by software processing based on the reflected light received by the light receiving device 120. At the same time, it is also possible to detect the airflow speed in the traveling direction based on the amount of Doppler shift.

[0099] The airflow measuring device 100 can be applied not only to an 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 to another aircraft. The airflow measuring device 100 can also be mounted on a ship or a vehicle.

[0100] Although the embodiments and modified examples of the present technology have been described above, the present technology is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the gist of the present technology. [Explanation of symbols]

[0101] 1 aircraft 2. Irradiation and receiving device 3 Reflection Map 4 Inspection Area 5. Grid Area 6 Virtual Surface 100 Airflow measuring device 110 Irradiation device 111 Laser Oscillation Device 112 Scanning Device 120 Photodetector 130 Processing equipment 131 Calculation Device 132 Arithmetic equipment 140 Storage device 150 Display device 151 Speed ​​display screen

Claims

1. 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; Based on the time delay, the reflected light reflected by the virtual surface is extracted. A calculation device; 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, the speed of the airflow on the virtual surface in a direction intersecting the optical axis is measured. A computing device An airflow measuring device comprising:

2. 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 calculation device measures the speed of the airflow in a surface direction of the virtual surface as a direction intersecting the optical axis. Airflow measuring device.

3. The airflow measuring device according to claim 1 or 2, The imaginary plane is perpendicular to the optical axis of light irradiated to one point on the imaginary plane. Airflow measuring device.

4. The airflow measuring device according to any one of claims 1 to 3, The airflow measuring device is mounted on an aircraft. Airflow measuring device.

5. The airflow measuring device according to claim 4, The virtual surface includes a flight path along which the aircraft is intended to fly. Airflow measuring device.

6. The airflow measuring device according to claim 4 or 5, The virtual surface includes a flight path that the aircraft will fly to avoid turbulence when turbulence exists on the virtual surface. Airflow measuring device.

7. 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 aircraft irradiates light from a different position on the flight path during flight. Airflow measuring device.

8. 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; Calculating changes in the patterns of the plurality of reflected light maps. Airflow measuring device.

9. 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, included in the inspection section, is from several to several tens. Airflow measuring device.

10. 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; a scanning device that controls an irradiation direction of the laser light to scan all areas of the virtual surface with the laser light; have Airflow measuring device.

11. An airflow measuring device as claimed in claim 10, The calculation device or the arithmetic device corrects a time delay deviation according to a deviation in irradiation timing caused by scanning the virtual surface with the laser light. Airflow measuring device.

12. 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 computing device further measures the speed of the airflow in the direction of the optical axis on the virtual surface based on the amount of Doppler shift. Airflow measuring device.

13. The airflow measuring device according to any one of claims 1 to 12, The irradiation device; The light receiving device; The airflow measuring device further comprises:

14. 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, the speed of the airflow on the virtual surface in a direction intersecting the optical axis is measured. Airflow measurement methods.

15. 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; 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. This is an airflow measurement program that runs like this.

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