Device and method for measuring fog drops under rotor wing airflow of plant protection unmanned aerial vehicle

Abstract

The invention relates to a device and method for measuring fog drops under rotor wing airflow of a plant protection unmanned aerial vehicle, and the device comprises a fog drop receiving mechanism, an image collection mechanism and a calculation and measurement mechanism, the fog drop receiving mechanism comprises a plurality of silicone oil culture dishes which are arranged at intervals in the horizontal direction, and is used for receiving the fog drops sprayed by the plant protection unmanned aerial vehicle; the image acquisition mechanism is used for acquiring a distribution image of fog drops deposited in the silicone oil culture dish, and the calculation and measurement mechanism is used for calculating and obtaining a fog drop particle size spectrum and / or fog drop distribution density according to the acquired fog drop distribution image. According to the invention, the hydrophobic property of the silicone oil is utilized, so that the silicone oil can wrap the fog drops, mutual dispersion of the fog drops is facilitated, and inaccurate acquisition of the number of the fog drops caused by gathering of the fog drops and even too high estimation of the particle size of the fog drops caused by adhesion of the fog drops are avoided; by utilizing the colorless characteristic of silicone oil, the background of the acquired image is transparent, the image processing quality is improved, and the fog drop distribution characteristic measurement accuracy is finally improved.

Description

Technical Field

[0001] The present invention relates to the technical field of unmanned aerial vehicle (UAV) plant protection operations, and particularly to a measuring device and method for droplets under the rotor airflow of a plant protection UAV. Background Art

[0002] The droplet size is an important factor affecting the effective deposition and drift of pesticide droplets in agricultural spraying. For ground machinery spraying and UAV spraying without rotor airflow, methods such as laser diffraction and phase Doppler imaging are usually used to measure the droplets floating in the air in real time to obtain the droplet size distribution characteristics. However, the optical systems equipped with these testing methods require a strictly controlled testing environment, and the measurement accuracy is significantly affected by factors such as rotor airflow, external natural wind, light, temperature, and humidity, making it difficult to complete the droplet size evaluation at multiple points when the UAV is performing spraying tasks. The existing methods for measuring droplets after deposition can collect droplets through artificial receiving materials (such as water-sensitive paper, photo paper, etc.) and provide references for the determination of droplet size distribution through image processing. However, the test results are easily affected by the collector material and the superposition of droplets on the collector, and their measurement accuracy still cannot meet the requirements. Summary of the Invention

[0003] The present invention provides a measuring device and method for droplets under the rotor airflow of a plant protection UAV.

[0004] Specifically, the present invention is implemented through the following technical solutions:

[0005] In a first aspect, the present invention provides a measuring device for droplets under the rotor airflow of a plant protection UAV, which is used to measure the droplet distribution characteristics sprayed from the nozzle of a plant protection UAV in a hovering or flying state. The nozzle is located below the rotor. The measuring device for droplets under the rotor airflow of the plant protection UAV includes a droplet receiving mechanism, an image acquisition mechanism, and a calculation and measurement mechanism. The droplet receiving mechanism includes a plurality of silicone oil culture dishes arranged at intervals in one direction, which are used to receive the droplets sprayed by the plant protection UAV. The image acquisition mechanism is used to acquire the droplet distribution image deposited in the silicone oil culture dish. The calculation and measurement mechanism is used to calculate and obtain the droplet size spectrum and / or droplet distribution density based on the acquired droplet distribution image.

[0006] In some embodiments, the droplet receiving mechanism includes a frame, and the silicone oil culture dish is arranged on the frame and has a height distance from the ground; and / or, the frame is telescopable in the height direction to be suitable for adjusting the height distance between the silicone oil culture dish and the ground.

[0007] In some embodiments, the image acquisition mechanism includes a backlight source, and the backlight source is arranged below the silicone oil culture dish to be suitable for the backlight source to penetrate the bottom of the silicone oil culture dish to illuminate the droplets deposited in the silicone oil culture dish.

[0008] In some embodiments, the image acquisition mechanism includes a base, a backlight source and a silicone oil culture dish are sequentially arranged in the base; and / or, the backlight sources corresponding to all the silicone oil culture dishes are divided into several groups, and the backlight sources in each group are connected in series, and the backlight sources in each group are connected in parallel.

[0009] In some embodiments, the image acquisition mechanism includes a light-shielding cover and a camera. The light-shielding cover is in a hollow cylindrical shape and is arranged on the outer periphery of the silicone oil culture dish, and the camera is arranged at the top opening of the hollow cylinder of the light-shielding cover, so as to be suitable for the camera to seal the top opening of the hollow cylinder of the light-shielding cover, thereby collecting the droplet distribution image deposited in the silicone oil culture dish through the camera.

[0010] In some embodiments, the light-shielding cover is in a hollow cylindrical shape, and the inner diameter of the hollow cylinder matches the outer diameter of the camera and the outer diameter of the silicone oil culture dish respectively.

[0011] In some embodiments, the calculation and measurement mechanism is used to perform image processing on the droplet distribution image collected on the silicone oil culture dish. In the image processing process, a ROI region of 1500 pixels × 1500 pixels is extracted from the RGB image. After calculating the average value of the three channels, binarization processing is performed using a threshold of 0.3 to 0.8.

[0012] In a second aspect, the present invention provides a method for measuring droplets under the rotor airflow of a plant protection unmanned aircraft, which is used to measure the droplet distribution characteristics sprayed from the nozzle of a plant protection unmanned aircraft in a hovering or flying state. The nozzle is located below the rotor. The method for measuring the droplets sprayed by the plant protection unmanned aircraft includes:

[0013] Install a measurement device, the measurement device includes a droplet receiving mechanism, an image acquisition mechanism and a calculation and measurement mechanism. The droplet receiving mechanism includes a plurality of silicone oil culture dishes arranged at intervals in one direction, and is used to receive the droplets sprayed by the plant protection unmanned aircraft;

[0014] Control the plant protection unmanned aircraft to spray droplets. When spraying droplets, fix the plant protection unmanned aircraft above one or both of the middle ones of the plurality of spaced silicone oil culture dishes, or make the plant protection unmanned aircraft fly in another direction perpendicular to the direction in which the plurality of spaced silicone oil culture dishes are arranged and fly over one or both of the middle ones of the plurality of spaced silicone oil culture dishes;

[0015] Image acquisition, use the image acquisition mechanism to collect the droplet distribution image deposited in the silicone oil culture dish;

[0016] Calculation of droplet distribution characteristics, use the calculation and measurement mechanism to calculate and obtain the droplet size spectrum and / or droplet distribution density according to the collected droplet distribution image.

[0017] In some embodiments, after the image acquisition and before the calculation of the droplet distribution situation, it further includes:

[0018] Image processing: Use a computational measurement mechanism to extract a ROI region of 1500 pixels × 1500 pixels in the center of an RGB image. After calculating the average value of the three channels, perform binarization processing with a threshold of 0.3 to 0.8.

[0019] In some embodiments, in the calculation of the droplet distribution characteristics, calculate the equivalent spherical volume according to the particle area of each deposited droplet, and then calculate DV 10 、DV 50 、DV 90 、RS value, so as to obtain the droplet size spectrum; and / or calculate the number of deposited droplets per unit area, so as to obtain the droplet distribution density.

[0020] According to the present invention, a silicone oil culture dish is used to receive the deposited droplets, and image processing technology is used to measure the distribution characteristics of the deposited droplets. Utilizing the hydrophobic property of silicone oil, the silicone oil can wrap the droplets, which is beneficial to the mutual dispersion of the droplets and avoids inaccurate acquisition of the droplet quantity caused by the aggregation of droplets, and even overestimation of the droplet size due to the adhesion between droplets; utilizing the colorless property of silicone oil, it ensures that the background of the collected image is transparent, improves the quality of image processing, and ultimately improves the measurement accuracy of the droplet distribution characteristics.

[0021] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. Brief Description of the Drawings

[0022] The drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with this application, and are used together with the specification to explain the principles of this application.

[0023] Figure 1 is a front view of the usage state of a measurement device for droplets under the rotor airflow of a plant protection unmanned aircraft in an embodiment of the present invention;

[0024] Figure 2 is a partial schematic view of a measurement device for droplets under the rotor airflow of a plant protection unmanned aircraft in an embodiment of the present invention;

[0025] Figure 3 is a top view of the usage state of a measurement device for droplets under the rotor airflow of a plant protection unmanned aircraft in an embodiment of the present invention;

[0026] Figure 4 is a schematic view of a collected image after a silicone oil culture dish receives droplet deposition in an embodiment of the present invention;

[0027] Figure 5 is a schematic view of the grayscale processing of an image after a silicone oil culture dish receives droplet deposition in an embodiment of the present invention;

[0028] Figure 6 It is a schematic diagram of the binary image processing of the silicone oil culture dish after receiving droplet deposition in an embodiment of the present invention.

[0029] Reference numerals:

[0030] 1: Frame; 2: Silicone oil culture dish; 31: Light-shielding cover; 32: Camera. Detailed implementation manners

[0031] Now, the present disclosure will be described with reference to several embodiments. It should be understood that these embodiments are described only to enable those of ordinary skill in the art to better understand and thus implement the present disclosure, rather than implying any limitation on the scope of the present disclosure.

[0032] As used herein, the term "including" and its variants are to be construed as open-ended terms meaning "including but not limited to"; the terms "embodiment" and "an embodiment" are to be construed as "at least one embodiment"; the term "another embodiment" is to be construed as "at least one other embodiment"; the terms "first", "second", etc. may refer to different or the same objects; the term "arranged" is not limited to direct connection or indirect connection, nor to a specific connection manner. There may also be other explicit and implicit definitions hereinafter.

[0033] In the following description, some specific numerical values or numerical ranges may be involved. It should be understood that these numerical values and numerical ranges are only exemplary and may be helpful for putting the idea of the present disclosure into practice. However, the description of these examples is not intended to limit the scope of the present disclosure in any way. These numerical values or numerical ranges can be set otherwise according to specific application scenarios and requirements.

[0034] As described above, in the prior art, under the state of having the influence of the rotor airflow, water-sensitive paper, photographic paper and other materials are used to receive droplet deposition, and the droplet distribution characteristics after deposition are measured by an image method. However, affected by factors such as the receiving material and droplet superposition, the measurement accuracy of the existing droplet distribution characteristics after deposition still cannot meet the requirements. The droplet measurement device and measurement method under the rotor airflow of the plant protection unmanned aircraft proposed by the embodiments of the present invention at least partially solve the above problems. As Figure 1 - Figure 2 shown, the droplet measurement device under the rotor airflow of the plant protection unmanned aircraft in the embodiment of the present invention generally includes a droplet receiving mechanism, an image acquisition mechanism and a calculation and measurement mechanism. Among them, the pesticide droplets sprayed by the plant protection unmanned aircraft are deposited in the droplet receiving mechanism under the action of the downdraft generated in the hovering or flying state, the image acquisition mechanism is used to acquire the deposited droplet distribution image in the droplet receiving mechanism, and the calculation and measurement mechanism is used to calculate and obtain the droplet distribution characteristics according to the acquired droplet distribution image.

[0035] The image acquisition mechanism of the embodiment of the present invention includes a silicone oil culture dish 2. Silicone oil has characteristics such as being colorless, odorless, non-toxic, and hydrophobic. Utilizing its colorless characteristic, it ensures that the background of the image obtained by image acquisition of the deposited droplets is bright, improving the quality of image processing and ultimately enhancing the measurement accuracy of droplet distribution characteristics. Utilizing its hydrophobic characteristic, silicone oil can wrap pesticide droplets mainly composed of water, facilitating the mutual dispersion of droplets and avoiding adhesion caused by the aggregation of droplets, which may cause two or more droplets to be misidentified as one droplet in the acquired image, resulting in the number of droplets obtained being less than the actual number and the particle size of some of the obtained droplets being larger than the actual particle size. Exemplarily, a culture dish with a wall thickness of 2 mm and a diameter of 45 mm is selected for the silicone oil culture dish 2, and 3 ml of silicone oil is placed therein.

[0036] Since the coverage width of the droplets sprayed by the plant protection unmanned aircraft is large, in order to measure the droplet distribution characteristics in the vertical flight path direction of the plant protection unmanned aircraft, in the embodiment of the present invention, a plurality of silicone oil culture dishes 2 are arranged at intervals in the vertical flight path direction, and there are differences in the droplet sedimentation distribution characteristics received by different silicone oil culture dishes 2 arranged in the vertical flight path direction. Exemplarily, 16 silicone oil culture dishes 2 are arranged in the vertical flight path direction, and the distance between adjacent silicone oil culture dishes 2 is 50 cm.

[0037] In one embodiment, the droplet receiving mechanism includes a frame 1, and the silicone oil culture dish 2 is arranged on the frame 1, so that there is a height distance between the silicone oil culture dish 2 and the ground that matches the height of the plant canopy, so that the reference height of the measured droplet distribution characteristics matches the height of the plant canopy. Exemplarily, the frame 1 is made of multiple 30×30 aluminum profiles, and 16 silicone oil culture dishes 2 are arranged at intervals in the vertical flight path direction on the aluminum profiles, so that the height between each silicone oil culture dish 2 and the ground is 1 m.

[0038] In one embodiment, the frame 1 is set to have a telescopic structure in the height direction, so that the height distance between the silicone oil culture dish 2 arranged on the frame 1 and the ground can be adjusted, so that the reference height of the measured droplet distribution characteristics can be flexibly adapted to different plant canopy heights.

[0039] In one embodiment, the image acquisition mechanism includes a backlight source, and the backlight source is arranged below the silicone oil culture dish 2. Since the silicone oil culture dish 2 is made of a transparent material, after the backlight source is connected to the power supply, it can penetrate the bottom of the silicone oil culture dish 2 and illuminate the deposited droplets, making the illumination structure simple and the illumination operation fast. Since the deposited droplets in the silicone oil culture dish 2 are distributed in layers, this setting method of the backlight source enables the light to penetrate all the deposited droplets in the silicone oil culture dish 2, avoiding the problem of reduced image acquisition effect caused by uneven illumination of each layer of droplet distribution. Exemplarily, the size of the backlight plate where the backlight source is located is set to 50×50 mm.

[0040] In one embodiment, the image acquisition mechanism includes a light shield 31 and a camera 32. The light shield 31 is in the shape of a hollow cylinder. The light shield 31 is arranged on the outer periphery of the silicone oil culture dish 2. The top of the hollow cylinder of the light shield 31 forms an opening. The camera 32 is arranged at the top opening of the hollow cylinder, thereby sealing the top opening and forming a closed dark area inside the hollow cylinder. The lens of the camera 32 extends into the dark area and collects the droplet deposition image with the help of a backlight. Such a setting can avoid the influence of external environmental light on the clarity of the droplet deposition image acquisition, and the structure is simple and the operation process is convenient. When it is necessary to acquire an image, only the light shield 31 and the camera 32 need to be placed at the silicone oil culture dish 2. Exemplarily, the light shield 31 is made of black PLA material to ensure complete shielding of external environmental light.

[0041] In one embodiment, the light shield 31 is in the shape of a hollow cylinder. The inner diameter of the hollow cylinder matches the outer diameter of the silicone oil culture dish 2, and the inner diameter of the hollow cylinder also matches the outer diameter of the lens of the camera 32. Thus, during the image acquisition process, the positioning between the camera 32 and the silicone oil culture dish 2 is ensured to be accurate, thereby ensuring the stability of the acquired image. Exemplarily, the inner diameter of the hollow cylinder of the light shield 31 is set to 48 mm, the outer diameter of the lens of the camera 32 is 48 mm, and the outer diameter of the silicone oil culture dish 2 is 47 mm. An error of 1 mm can meet the requirement that the cooperation between the light shield 31 and the silicone oil culture dish 2 is stable and does not loosen.

[0042] In one embodiment, the image acquisition mechanism includes a base. The backlight and the silicone oil culture dish 2 are sequentially arranged in the base. The base is directly fixed to the frame 1, making the installation process of the backlight and the silicone oil culture dish 2 simple.

[0043] In one embodiment, the backlights corresponding to all the silicone oil culture dishes 2 are divided into several groups. The backlights in each group are connected in series, and the groups of backlights are connected in parallel, so that the actual power of each backlight is as consistent as possible, ensuring that the illumination degree of each backlight on the deposited droplets is as consistent as possible, thereby avoiding the deviation of the image acquisition effect caused by different illumination degrees of the backlights of different silicone oil culture dishes 2. Exemplarily, the backlights corresponding to 16 silicone oil culture dishes 2 are divided into four groups. The four backlights in each group are connected in series, and the four groups of backlights are connected in parallel to a 12V power supply, and the voltage of each backlight is 3V.

[0044] Before the calculation and measurement mechanism calculates the droplet distribution characteristics based on the acquired droplet distribution image, image processing needs to be performed on the acquired image. In one embodiment, an RGB image as shown in Figure 4 is acquired by the camera 32. When the calculation and measurement mechanism performs image processing, as shown in Figure 4 first, a ROI area of 1500 pixels × 1500 pixels at the center of the culture dish is extracted; as shown in Figure 5As shown, the grayscale is calculated through the three-channel average Gray = (R + G + B) / 3; as Figure 6 shown, the grayscale image is binarized using a fixed threshold of 0.3 to 0.8, and finally the particle size spectrum and droplet distribution density of the deposited droplets in the silicone oil petri dish 2 are calculated. Exemplarily, the fixed threshold can be selected as 0.5.

[0045] In the embodiments of the present invention, a measuring device is used to measure the droplet size distribution under the rotor airflow of a plant protection UAV. The steps include installing the measuring device, controlling the plant protection UAV to spray droplets, image acquisition, image processing, and calculation of droplet distribution characteristics. Among them:

[0046] In the step of installing the measuring device, the measuring device of the embodiments of the present invention is installed at the measuring site, and a plurality of silicone oil petri dishes 2 are arranged at intervals in one direction. Among them, each silicone oil petri dish 2 is arranged on the frame 1 through a base, 3 ml of silicone oil is dropped into the silicone oil petri dish 2 and placed open.

[0047] In the step of controlling the plant protection UAV to spray droplets, the plant protection UAV can be hoisted above the silicone oil petri dish 2 through a bracket to simulate the hovering state of the UAV, or the plant protection UAV can be controlled to fly over the silicone oil petri dish 2 along a flight route perpendicular to the arrangement direction of the silicone oil petri dishes 2, as Figure 3 shown. Exemplarily, as Figure 1 shown, when the UAV is in the hovering and flying states, the height of the nozzle of the UAV from the ground is 3 m, approximating the real flight state during the operation of the plant protection UAV.

[0048] In one embodiment, the UAV is controlled to hover above the middle area of a plurality of silicone oil petri dishes 2, or the UAV is controlled to fly over the middle area of a plurality of silicone oil petri dishes 2. Exemplarily, as Figure 1 and Figure 3 shown, the middle area is the position between the 8th and 9th petri dishes among 16 silicone oil petri dishes 2, so as to ensure the symmetry of the spray deposition distribution characteristics received by the silicone oil petri dishes 2. Exemplarily, the arrangement width of 16 silicone oil petri dishes totals 7.5 m, and the UAV flies over from the middle position of 3.75 m.

[0049] In the step of image acquisition, the light shield 31 and the camera 32 are arranged on the silicone oil petri dish 2, the backlight is turned on, and the camera 32 is used to acquire images.

[0050] In the step of image processing, the computing and measuring mechanism extracts the ROI region of 1500 pixels × 1500 pixels in the center of the RGB image. After calculating the three-channel average value, binarization processing is performed using a threshold of 0.3 to 0.8.

[0051] In the calculation step of the droplet distribution characteristics, the equivalent spherical volume is calculated according to the particle area of each deposited droplet, and then DV is calculated. 10 、DV 50 、DV 90 、RS values are obtained to acquire the droplet size spectrum; and the number of deposited droplets per unit area is calculated to obtain the droplet distribution density. DV m represents the particle size corresponding to when the cumulative particle size distribution percentage of the sample reaches m%, where DV 50 is the volume median diameter of the droplets, and RS is the droplet distribution span, which is used to measure the uniformity of the droplet size distribution.

[0052] To verify the actual effect of the embodiments of the present invention, the droplet size of the droplets sprayed by the suspended and fixed unmanned aerial vehicle (UAV) is actually measured with a laser particle size analyzer (Table 1 below). The droplets sprayed by the suspended and fixed UAV are received with photographic paper, water-sensitive paper, and silicone oil respectively, and the droplet size after deposition is measured through image processing (Table 2 below).

[0053] Table 1 Measurement results of droplet size by DP-02 laser diffractometer

[0054]

[0055] Table 2 Measurement results of droplet size by three receiving materials

[0056]

[0057]

[0058] The plant protection UAV is suspended on a shelf. By setting masks, baffles, etc. around the laser particle size analyzer, the influence of the downwash airflow field of the UAV rotor on the test stability of the laser particle size analyzer is weakened, and relatively accurate droplet size data can be obtained. After comparison, taking DV 50 as an example, when the set particle size is greater than 150um, the droplet sizes obtained by the photographic paper and water-sensitive paper are significantly larger due to droplet coalescence. In the range of 50 - 300um, the measured results of the deposited droplets received by the silicone oil culture dish have a fixed coefficient relationship with the measurement results of the laser particle size analyzer, and relatively accurate droplet size values can be obtained through conversion. Thus, it can be seen that the measurement accuracy of the droplet size under the rotor airflow of the plant protection UAV by the silicone oil culture dish is higher than that of the receiving methods of photographic paper and water-sensitive paper.

[0059] Regarding any reference to directions and orientations in the description of the embodiments herein, it is only for the convenience of description and should not be construed as any limitation to the protection scope of the present invention. The description of the preferred embodiments involves combinations of features, and these features may exist independently or in combination. The present invention is not particularly limited to the preferred embodiments. The scope of the present invention is defined by the claims.

[0060] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A device for measuring droplets under the rotor airflow of a plant protection unmanned aircraft, used to measure the droplet distribution characteristics of the spray from the nozzle of the plant protection unmanned aircraft in a hovering or flying state, wherein the nozzle is located under the rotor, and is characterized in that: The device for measuring droplets sprayed by the plant protection unmanned aircraft comprises a droplet receiving mechanism, an image acquisition mechanism and a calculation and measurement mechanism. The droplet receiving mechanism comprises a plurality of silicone oil culture dishes arranged at intervals along a horizontal direction, and is used to receive droplets sprayed by the plant protection unmanned aircraft. The image acquisition mechanism is used to acquire a distribution image of droplets deposited in the silicone oil culture dishes. The calculation and measurement mechanism is used to calculate and obtain a droplet size spectrum and / or a droplet distribution density based on the acquired droplet distribution image.

2. The device for measuring droplets under the rotor airflow of a plant protection unmanned aircraft according to claim 1 is characterized in that: The droplet receiving mechanism comprises a frame, the silicone oil culture dish is arranged on the frame and has a height distance from the ground; and / or the frame is retractable in height direction so as to be suitable for adjusting the height distance between the silicone oil culture dish and the ground.

3. The device for measuring droplets under the rotor airflow of a plant protection unmanned aircraft according to claim 1, characterized in that: The image acquisition mechanism comprises a backlight source, which is arranged below the silicone oil culture dish so as to allow the backlight source to penetrate through the bottom of the silicone oil culture dish, thereby illuminating the mist droplets deposited in the silicone oil culture dish.

4. The device for measuring droplets under the rotor airflow of a plant protection unmanned aircraft according to claim 3 is characterized in that: The image acquisition mechanism includes a base, and the backlight source and the silicone oil culture dish are arranged in the base in sequence; and / or, the backlight sources corresponding to all the silicone oil culture dishes are divided into several groups, each group of backlight sources is connected in series, and each group of backlight sources is connected in parallel.

5. The device for measuring droplets under the rotor airflow of a plant protection unmanned aircraft according to claim 3, characterized in that: The image acquisition mechanism includes a light shield and a camera. The light shield is hollow cylindrical and is arranged on the outer periphery of the silicone oil culture dish. The camera is arranged at the hollow cylindrical top opening of the light shield so that the camera can seal the hollow cylindrical top opening of the light shield, thereby acquiring the distribution image of droplets deposited in the silicone oil culture dish through the camera.

6. The device for measuring droplets under the rotor airflow of a plant protection unmanned aircraft according to claim 5, characterized in that: The light shield is in the shape of a hollow cylinder, and the inner diameter of the hollow cylinder matches the outer diameter of the camera and the outer diameter of the silicone oil culture dish respectively.

7. The device for measuring droplets under the rotor airflow of a plant protection unmanned aircraft according to claim 1, characterized in that: The computing and measuring mechanism is used to process the image of the droplet distribution deposited in the silicone oil culture dish. The image processing process extracts the ROI area of ​​1500 pixels × 1500 pixels in the center of the RGB image, calculates the average value of the three channels, and then uses a threshold of 0.3 to 0.8 for binarization.

8. A method for measuring droplets under the rotor airflow of a plant protection unmanned aircraft, used to measure the droplet distribution characteristics of spray from the nozzle of a plant protection unmanned aircraft in a hovering or flying state, wherein the nozzle is located under the rotor, and is characterized in that: The method for measuring droplets under the rotor airflow of the plant protection unmanned aircraft includes: Install a measuring device, which includes a droplet receiving mechanism, an image acquisition mechanism and a calculation and measurement mechanism. The droplet receiving mechanism includes a plurality of silicone oil culture dishes arranged at intervals along one direction, and is used to receive droplets sprayed by the plant protection drone; Controlling the plant protection drone to spray droplets, when spraying droplets, fix the plant protection drone above one or two of the middle of the plurality of silicone oil culture dishes arranged at intervals, or make the plant protection drone fly in another direction perpendicular to the direction in which the plurality of silicone oil culture dishes are arranged at intervals and fly over one or two of the middle of the plurality of silicone oil culture dishes arranged at intervals; Image acquisition, using an image acquisition mechanism to acquire a distribution image of droplets deposited in a silicone oil culture dish; The droplet distribution characteristics are calculated by using a calculation and measurement mechanism to calculate the droplet size spectrum and / or droplet distribution density based on the collected droplet distribution image.

9. The method for measuring droplets under the rotor airflow of a plant protection unmanned aircraft according to claim 8, characterized in that: After the image is collected and before the droplet distribution is calculated, the method further includes: For image processing, a calculation and measurement mechanism was used to extract a ROI area of ​​1500 pixels × 1500 pixels in the center of the RGB image, and after calculating the average of the three channels, a binarization process was performed using a threshold of 0.3 to 0.

8.

10. The method for measuring droplets under the rotor airflow of a plant protection unmanned aircraft according to claim 8, characterized in that: In the calculation of the droplet distribution characteristics, the equivalent spherical volume is calculated according to the particle area of ​​each deposited droplet, and then DV is calculated. 10 、DV 50 、DV 90 , RS values, thereby obtaining the droplet size spectrum; and / or, calculating the number of deposited droplets per unit area, thereby obtaining the droplet distribution density.

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