Plant growth detection method, plant sensor, and fertilizer application device

Abstract

To provide a method for detecting plant growth amounts and a plant sensor capable of accurately detecting the growth conditions of a plant, and to provide a fertilizing apparatus capable of appropriately fertilizing according to the growth conditions.SOLUTION: The inventive method comprises: performing, with a laser scanner 4, a scan using a pulsed distance measuring light with two wavelengths having different reflectances relative to nitrogen contents; separating the two wavelengths and receiving the separated lights; detecting a distance measurement value and a light amount for each pulsed distance measuring light and for each of the two wavelengths; detecting height of a crop based on the distance measurement value; detecting a received light amount ratio for the two wavelengths; and detecting growth conditions of the crop based on the detected height and the received light amount ratio.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a plant growth detection method for detecting the growth state of a plant, a plant sensor for detecting the growth state of a plant, and a fertilizer application device for applying fertilizer suitable for the growth state of a plant. [Background technology]

[0002] Detecting the growth status of plants, particularly agricultural crops, is important in the production management of agricultural crops, and conventionally, as shown in Patent Document 1, detection light diffused in one direction is irradiated and the growth status is detected based on the reflected detection light from the leaves of the plant.

[0003] However, this reflected light also includes light reflected from the soil other than the leaves of the plants, and the reflected light from sources other than the leaves becomes a noise component. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-208859 A [Patent Document 2] JP 2019-146562 A [Patent Document 3] JP 2019-175246 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a plant growth detection method and a plant sensor capable of detecting the growth condition accurately, and further provides a fertilizer application device capable of applying fertilizer appropriately in response to the growth condition. [Means for solving the problem]

[0006] The present invention relates to a plant growth detection method in which a laser scanner scans pulsed ranging light consisting of two wavelengths with different reflectivities depending on the nitrogen content, the two wavelengths are separated and received, the ranging value and light amount are detected for each pulsed ranging light and for each of the two wavelengths, the height of the crop is detected based on the ranging values, the ratio of the received light amounts of the two wavelengths is detected, and the growth condition of the crop is detected based on the detected height and ratio of the received light amounts.

[0007] The present invention also relates to a plant growth detection method, wherein the two wavelengths of the pulsed distance measuring light are 735 nm and 809 nm.

[0008] The present invention also relates to a plant growth detection method in which, when detecting crop height based on the distance measurement values, a threshold is set and distance measurement data that deviates from the threshold for each pulse distance measurement light is deleted as noise data, and, when detecting crop growth status based on the ratio of received light amounts, a threshold is set for each pulse distance measurement light and received light amount ratio data that deviates from the threshold is deleted as noise data.

[0009] The present invention also relates to a plant sensor which comprises a laser scanner having an emitter which emits pulse distance measuring light consisting of two wavelengths, a scan mirror which scans the pulse distance measuring light, a light receiving unit which separates and receives the reflected pulse distance measuring light from the object to be measured for each pulse distance measuring light and for each two wavelengths, and a distance measuring unit which acquires distance measuring values ​​for each wavelength for each pulse distance measuring light, a light amount detection unit which detects the received light amount of the reflected pulse distance measuring light received by the light receiving unit for each pulse distance measuring light, and a growth amount / fertilizer amount calculation unit, wherein the growth amount / fertilizer amount calculation unit detects the distance measuring value and light amount for each pulse distance measuring light and for each two wavelengths, calculates the crop height based on the distance measuring value, detects the ratio of the received light amounts of the two wavelengths, calculates the crop growth state based on the detected height and received light amount ratio, and detects the plant growth amount based on the two calculation results.

[0010] The present invention also relates to a plant sensor, wherein the two wavelengths of the pulse distance measuring light are 735 nm and 809 nm.

[0011] The present invention also relates to a plant sensor in which the growth amount / fertilizer amount calculation unit has a threshold for judging whether the distance measurement data detecting the height of the crop is correct, and has a threshold for judging whether the received light amount ratio data is correct, and determines whether the distance measurement data and the received light amount ratio data are correct for each pulse of distance measurement light based on the respective thresholds, and eliminates the distance measurement data and the received light amount ratio data that fall outside the thresholds as noise data.

[0012] Furthermore, the present invention relates to a fertilizer application device which has the above-mentioned plant sensor provided on the front side of an agricultural machine, a fertilizer spreader provided on the rear side of the agricultural machine, and a control unit, the control unit determining the amount of fertilizer to be spread based on the amount of plant growth obtained from the plant sensor, and controlling the fertilizer spreader to apply fertilizer. Effect of the Invention

[0013] According to the present invention, a laser scanner scans pulse distance measuring light consisting of two wavelengths with different reflectivities depending on the nitrogen content, the two wavelengths are separated and received, the distance measuring value and light amount are detected for each pulse distance measuring light and for each of the two wavelengths, the height of the crop is detected based on the distance measuring value, the ratio of the received light amounts of the two wavelengths is detected, and the growth state of the crop is detected based on the detected height and ratio of the received light amounts.Since the growth state of the crop is detected using two detection elements, accuracy is improved, and further, since the growth state of the crop is detected for each pulse, a large amount of data can be obtained instantly, resulting in the excellent effect of improving measurement accuracy. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram of an agricultural machine equipped with a plant sensor and a fertilizer application device according to an embodiment of the present invention. [Diagram 2] FIG. 1A is an explanatory diagram showing the operation of detecting the amount of growth of a crop by a plant sensor, and FIG. 1B is an explanatory diagram showing the relationship between the leaves of the crop and a measurement point. [Diagram 3] FIG. 2 is a block diagram showing an outline of a plant sensor and an agricultural machine. [Figure 4] FIG. 1 is a schematic diagram illustrating the configuration of a laser scanner. [Diagram 5]10 is a flowchart showing growth amount detection and fertilizer spraying. [Figure 6] 13 is a flowchart showing a process for removing noise in detecting the amount of growth. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] FIG. 1 is a schematic diagram of an agricultural machine equipped with a plant sensor according to this embodiment.

[0017] In FIG. 1, 1 indicates an agricultural machine, 2 indicates a plant sensor, 3 indicates a fertilizer spreader, and A indicates a growth amount detection range A by the plant sensor 2.

[0018] A tractor is shown as an example of the agricultural machine 1. The plant sensor 2 is provided in the front of the agricultural machine 1, and the fertilizer spreader 3 is provided in the rear of the agricultural machine 1.

[0019] The positional relationship between the plant sensor 2 and the fertilizer application position of the fertilizer spreader 3 is known. The horizontal distance between the plant sensor 2 and the fertilizer spreader 3 in the traveling direction T of the agricultural machine 1 is also known.

[0020] The plant sensor 2 detects the growth state of the plant. The fertilizer spreader 3 spreads (applies) fertilizer, and the amount of fertilizer applied is controlled by a control device (described later) according to the growth state detected by the plant sensor 2.

[0021] In this embodiment, the plant sensor 2 includes a laser scanner 4 (see FIG. 4) that emits distance measuring light P1 and P2 of two wavelengths. The two wavelengths used have different reflectances depending on the nitrogen content of the crop.

[0022] As shown in Fig. 2(A), the laser scanner 4 has a configuration for line scanning distance measurement light P1, P2 in a direction perpendicular to the traveling direction T in front of the agricultural machine 1. Note that in Fig. 2, for ease of explanation, it is shown as if there is a width in the traveling direction, but in reality there is no width or almost no width. The laser scanner 4 only needs to be able to perform line scanning, and may be a line scanner that performs scanning on one axis.

[0023] The laser scanner 4 has a measurement reference position, and the horizontal distance between the measurement reference position and the fertilizer application position of the fertilizer spreader 3 is known. In addition, the vertical distance between the measurement reference position and the ground surface (the vertical distance between the measurement reference position and the running surface of the agricultural machine 1) is also known.

[0024] The laser scanner 4 executes one line scan at a predetermined time interval. One line scan is executed at least once, or multiple times. Two wavelengths of distance measuring light P1, P2 are irradiated on the same optical axis, and distance is measured for each of the two wavelengths of distance measuring light. As with a normal laser scanner, distance is measured by emitting a pulsed distance measuring light (hereinafter, pulsed light), reflecting it off the measurement target, and measuring the distance based on the round-trip time and light speed of the reflected pulsed distance measuring light (hereinafter, reflected pulsed light). Therefore, distance measurement data is obtained for each pulsed light along the scan line.

[0025] The reflected distance measurement light includes light reflected by the leaves of the crop (shown by the solid line in Figure 2) and light reflected by things other than leaves, such as the soil (shown by the dashed line in Figure 2).As data for determining the growth status of the crop, the light reflected by the soil is unnecessary data, i.e., noise.

[0026] In addition, since the distance is measured for each pulse of light, it is possible to determine whether the distance data obtained from the distance measurement results is reflected by leaves or by soil, and therefore noise can be removed based on the distance measurement results.

[0027] Next, two different wavelengths are used as the distance measurement lights P1 and P2, and examples of the two wavelengths include 735 nm and 809 nm.

[0028] When a laser beam with a wavelength of 735 nm is used as the distance measuring light, it is reflected by the object being measured if it contains nitrogen, but it is known that the amount of reflected light is not affected by the amount of nitrogen content.

[0029] Furthermore, when a laser beam with a wavelength of 809 nm is used as the distance measuring light, it is reflected by the object being measured if it contains nitrogen, and it is known that the reflectivity varies depending on the nitrogen content, with the amount of reflected light increasing as the nitrogen content increases.

[0030] It is also known that crop leaves contain nitrogen, and when the growing conditions are good, the nitrogen content is high, and when the growing conditions are poor, the nitrogen content is low.

[0031] Incidentally, soil may also contain nitrogen, but the reflectance of soil and leaves differs greatly (soil's reflectance is significantly lower), so by comparing only the amount of reflected light, regardless of wavelength, it is possible to determine whether the light is being reflected by soil or leaves. Incidentally, Figure 2(B) shows the state in which the distance measurement light is irradiated onto a leaf.

[0032] As described above, distance measurement light P1 with a wavelength of 735 nm and distance measurement light P2 with a wavelength of 809 nm are both irradiated on the same optical axis, so distance measurement light P1 and distance measurement light P2 are irradiated onto the same measurement point. The amount of reflected light is affected and varies depending on the condition of the reflecting surface, such as the properties of the reflecting surface and dirt. However, since distance measurement light P1 and distance measurement light P2 are irradiated onto the same point on the reflecting surface, the effect of the condition of the reflecting surface on distance measurement light P1 and distance measurement light P2 is the same.

[0033] Therefore, the magnitude of the reflected light amount of the measuring light P1 and the measuring light P2, i.e., the magnitude of the received light amount, is determined to be due to the magnitude of the nitrogen content. The nitrogen content ratio at the measurement point can be found by dividing the amount of measuring light P2 by the amount of measuring light P1. If the nitrogen content ratio of the leaves of the crop corresponding to the growth state is obtained in advance, the growth state of the crop at the measurement point can be determined.

[0034] Next, the nitrogen content of soil is significantly lower than that of crop leaves, so the amount of light reflected from the soil is significantly smaller. By detecting the amount of reflected light, it is possible to determine that the measurement point is a location other than a leaf. From the amount of reflected light, it is possible to determine whether the measurement data was reflected by a leaf or by soil. Therefore, it is possible to remove noise based on the light amount results.

[0035] In addition, because the distance measurement light is pulsed light, it is possible to detect the amount of reflected light when distance measurement is not being performed. The amount of reflected light when distance measurement is not being performed can be obtained as dark noise, and by subtracting this, it is also possible to remove external light noise.

[0036] As described above, it is possible to judge whether each pulse of light is noise or not based on the distance measurement result and the light amount detection result, and further to remove any that are judged to be noise.

[0037] The amount of received light of the distance measuring light P1 and the distance measuring light P2 is compared for the noise-removed pulsed light (distance measuring light P1, distance measuring light P2) to obtain the ratio of the amount of received light. The ratio of the amount of received light corresponds to the nitrogen content ratio of the crop leaf. Therefore, by obtaining the relationship between the ratio of received light and the nitrogen content ratio in advance, the accurate nitrogen content ratio of the crop leaf can be obtained from the ratio of received light.

[0038] Moreover, as data for determining the growth state, an average value for each scan line may be calculated, or an average value for each set of multiple scan lines may be calculated, and used as data for determining the growth state.

[0039] Data on the amount of fertilizer to be applied corresponding to the data on the determination of the growth state is acquired in advance. The amount of fertilizer to be applied is calculated based on the data on the determination of the growth state, and the amount of fertilizer to be spread by the fertilizer spreader 3 is controlled.

[0040] FIG. 3 shows a schematic block diagram of the plant sensor according to this embodiment and a fertilizer application device 10 equipped with the plant sensor, and FIG. 4 shows a schematic configuration diagram of the plant sensor 2.

[0041] In FIG. 3, 11 denotes a control unit. The control unit 11 includes a scanner control calculation unit 11a, a growth The amount / fertilizer amount calculation unit 11b is included. In FIG. 3, 12 is a memory unit, 13 is a distance measurement unit, 14 is a is a light emitting part, 15 is a light receiving part, 19 is the angle measuring part, 17 is the vertical angle detector, 18 is the horizontal angle detector, 2 1 is a horizontal rotation drive unit, 22 is a vertical rotation drive unit, 23 is an operation unit, 24 is a display unit, and 25 is a speed The detector, 26, indicates a GNSS receiver.

[0042] The control unit 11, the scanner control calculation unit 11a, and the growth amount / fertilizer amount calculation unit 11b may be a CPU specialized for this embodiment, or a general-purpose CPU, an embedded CPU, a microprocessor, or the like. The storage unit 12 may be a semiconductor memory such as RAM, ROM, Flash ROM, or DRAM, a magnetic recording memory such as HDD, or an optical recording memory such as CD-ROM. The scanner control calculation unit 11a and the growth amount / fertilizer amount calculation unit 11b may be assigned a part of the control unit 11.

[0043] The scanner control calculation unit 11a controls the distance measurement operation of the laser scanner described later, and the growth amount / fertilizer amount calculation unit 11b calculates and judges the growth amount and growth condition based on the detection results of the plant sensor described later, and also controls the amount of fertilizer applied by the fertilizer spreader 3.

[0044] The storage unit 12 stores a sequence program for operating the laser scanner, a distance measurement program for performing distance measurement, a program for judging the growth state from the received light data, a noise removal program for removing noise data from the distance measurement data and the received light data, a program for judging the growth state, and a fertilization control program for calculating the amount of fertilizer to be applied according to the growth state and applying the fertilizer. The storage unit 12 also stores measurement data and growth state judgment data, and various data such as table data setting the amount of fertilizer to be applied corresponding to the growth state. The noise removal program also sets thresholds necessary for noise judgment, such as a threshold for distance measurement and a threshold for light amount. The thresholds include a threshold for setting an upper limit and a lower limit, and a threshold for setting a range.

[0045] The distance measuring unit 13 causes the light emitting unit 14 to emit light, receives a light receiving signal from the light receiving unit 15, and calculates the measured distance based on the light emission timing from the light emitting unit 14, the light receiving timing from the light receiving unit 15, and the speed of light, and functions as an optical distance meter. The angle measuring unit 19 calculates the vertical angle and horizontal angle of the measurement point based on the detection results of the vertical angle detector 17 and the horizontal angle detector 18.

[0046] The horizontal rotation drive unit 21 drives and controls a horizontal rotation motor 42, which will be described later, and the vertical rotation drive unit 22 drives and controls a vertical motor 37, which will be described later.

[0047] The speed detector 25 detects the moving speed of the agricultural machine 1, and inputs the detection result to the control unit 11. The GNSS receiver 26 acquires the global coordinates of the laser scanner.

[0048] The laser scanner 4 mainly includes the scanner control calculation unit 11a, the memory unit 12, and the measurement unit 13. Distance unit 13, light emitting unit 14, light receiving unit 15, vertical angle detector 17, horizontal angle detector 18, the angle measuring unit 19, the horizontal rotation drive unit 21, the vertical rotation drive unit 2 2 to It is composed of:

[0049] Furthermore, the plant sensor 2 is mainly composed of the laser scanner 4, a light amount detection unit 16, and the growth amount / fertilization amount calculation unit 11b.

[0050] First, the laser scanner 4 will be described with reference to FIG.

[0051] A stand 36 is supported on the platform 34 via a vertical rotation shaft 35 having a horizontal axis. A vertical motor 37 is connected to the vertical rotation shaft 35, and the vertical motor 37 rotates the stand 36 in the vertical direction around the vertical rotation shaft 35.

[0052] The stand 36 has a recess 38 in which a scan mirror 39 is provided, and the scan mirror 39 is supported by a horizontal rotation shaft 41. The axis of the horizontal rotation shaft 41 is perpendicular to the axis of the vertical rotation shaft 35, and a horizontal rotation motor 42 is connected to the horizontal rotation shaft 41. The horizontal rotation motor 42 rotates the scan mirror 39 in the horizontal direction around the horizontal rotation shaft 41.

[0053] The platform 34 is attached to the agricultural machine 1 so that the axis of the horizontal rotation shaft 41 is parallel to the traveling direction T of the agricultural machine 1 and inclined downward at a predetermined angle with respect to the vertical.

[0054] A distance measuring optical system 43 is housed within the mount 36 .

[0055] The distance measuring optical system 43 has, as the light emitting unit 14, a first light source 45 that emits a first laser beam of pulsed light with a wavelength of 735 nm, a second light source 46 that emits a second laser beam of pulsed light with a wavelength of 809 nm, and a first wavelength selection mirror 47. The first laser beam and the second laser beam are emitted at the same timing.

[0056] A first wavelength selection mirror 47 is provided on the optical axis of the first light source 45. The first wavelength selection mirror 47 has a wavelength selection characteristic of transmitting a wavelength of 735 nm and reflecting a wavelength of 809 nm. The first laser beam 45a transmits through the first wavelength selection mirror 47, and the second laser beam 46a is reflected by the first wavelength selection mirror 47 onto the optical axis of the first light source 45.

[0057] The first laser beam transmitted through the first wavelength selection mirror 47 and the second laser beam reflected by the first wavelength selection mirror 47 are deflected by the first deflection mirror 48 to be incident on the scan mirror 39, and are further reflected by the scan mirror 39 in a direction perpendicular to the axis of the horizontal rotation shaft 41.

[0058] The first laser beam and the second laser beam reflected by the scan mirror 39 are rotary irradiated (scanned) by the rotation of the scan mirror 39. Note that since the scanning is performed by uniaxial rotation of the horizontal rotation shaft 41, it is a one-dimensional scan, and the area in front of the agricultural machine 1 is scanned.

[0059] The first laser beam and the second laser beam reflected by the object to be measured are incident on the scan mirror 39, reflected by the scan mirror 39, pass through the focusing lens 49, are reflected by the second deflection mirror 51, and are incident on the light receiving unit 15.

[0060] The light receiving section 15 has a second wavelength selection mirror 52, a first light receiver 53, and a second light receiver 54. The second wavelength selection mirror 52 has wavelength selection characteristics of transmitting a wavelength of 735 nm and reflecting a wavelength of 809 nm.

[0061] The first laser beam having a wavelength of 735 nm that is incident on the light receiving unit 15 passes through the second wavelength selection mirror 52 and is received by the first light receiver 53. The second laser beam having a wavelength of 809 nm that is incident on the light receiving unit 15 is reflected by the second wavelength selection mirror 52 and is received by the second light receiver 54. The condenser lens 49 forms an image of the first laser beam and the second laser beam on the first light receiver 53 and the second light receiver 54, respectively, by its optical action.

[0062] The distance measuring unit 13 controls the emission of the first laser beam and the second laser beam from the first light source 45 and the second light source 46, and measures the distance for each pulse of the first laser beam and the second laser beam based on the time difference and the light speed between the emission timing from the first light source 45 and the second light source 46 and the reception timing from the first light receiver 53 and the second light receiver 54. Therefore, point cloud data is acquired along the scan line.

[0063] Since the first laser beam and the second laser beam are irradiated at the same timing along the same optical axis, each pulse of light is irradiated onto the same point, and the same distance measurement result is obtained.

[0064] Next, the horizontal angle and vertical angle at the time of emitting the pulsed light are detected by the vertical angle detector 17 and the horizontal angle detector 18, and data having three-dimensional data coordinates for each irradiation point of each pulsed light (hereinafter referred to as three-dimensional data) is obtained by correlating the angle measurement result with the distance measurement result by the distance measurement unit 13. Therefore, the point cloud data has three-dimensional data.

[0065] The scanner control calculation unit 11a controls the rotation speed of the horizontal rotation motor 42 according to a distance measurement program, and also controls the emission interval of each of the pulsed lights via the distance measurement unit 13. Furthermore, the point cloud data density is controlled by controlling the rotation speed of the horizontal rotation motor 42 and the emission interval of each of the pulsed lights.

[0066] Furthermore, the GNSS receiver 26 acquires the global coordinates at the time of emitting the pulsed light, and the scanner control calculation unit 11a can associate the distance measurement data acquired by the laser scanner with the global coordinates.

[0067] Next, the plant sensor 2 will be described.

[0068] As described above, the plant sensor 2 detects the growth state, and the plant sensor 2 according to this embodiment uses the distance measurement value and the amount of reflected light as parameters for detecting the growth state.

[0069] In this embodiment, the laser scanner acquires distance measurement data for each pulse of the first and second laser beams. Therefore, there is a clear difference in the distance measurement value between when the pulse of the beam is irradiated on a crop leaf and when the pulse of the beam is irradiated on soil and when the pulse of the beam is irradiated on soil (see FIG. 2). Furthermore, the accuracy of the distance measurement can be achieved to within a few centimeters. For this reason, the distance measurement value is compared for each pulse of the beam, and if the distance measurement value is large, for example, the difference between the distance measurement values ​​is equal to or greater than a threshold value, it is determined that the soil has been measured, and the distance measurement data is removed as noise. The threshold value is set, for example, to 2 cm, taking into consideration the distance measurement accuracy and the object to be measured.

[0070] The height of the crop is measured based on the distance measurement data after noise has been removed, and the state of growth is judged. When judging the height of the crop, the measurement reference position may be used as a reference, or the distance measurement data of the soil from which noise has been removed may be used as a reference.

[0071] In this embodiment, laser scanning is performed using two color laser beams.

[0072] Moreover, the first light receiver 53 and the second light receiver 54 are configured to emit light receiving signals according to the light amounts of the pulsed light received. The light receiving signals output from the first light receiver 53 and the second light receiver 54 are input to the light amount detection unit 16. The light amount detection unit 16 calculates the amount of received light from the light receiving signal, and further inputs the calculation result to the growth amount / fertilization amount calculation unit 11b.

[0073] The pulsed light incident on the light receiving unit 15 is separated by the second wavelength selection mirror 52 into a first laser beam of 735 nm and a second laser beam of 809 nm, and the first laser beam transmitted through the second wavelength selection mirror 52 is received by the first light receiver 53, and the second laser beam reflected by the second wavelength selection mirror 52 is received by the second light receiver 54.

[0074] As described above, the first laser beam with a wavelength of 735 nm is reflected by the measurement object if the measurement object contains nitrogen, but the amount of reflected light is not affected by the amount of nitrogen contained. Furthermore, the second laser beam with a wavelength of 809 nm is reflected by the measurement object if the measurement object contains nitrogen, and the reflectance differs depending on the nitrogen content, and the amount of reflected light increases as the nitrogen content increases.

[0075] Since the irradiation point of the first laser beam and the irradiation point of the second laser beam are the same, it can be determined that the difference in the amount of reflected light is due to the nitrogen content of the leaves of the crop. Therefore, by calculating the ratio of the amount of received light of the second laser beam to the amount of received light of the first laser beam, the state of the nitrogen content of the leaf being measured, i.e., the crop, can be detected, and further the growth state of the crop can be detected.

[0076] Next, soil contains almost no nitrogen, or even if it does, it contains much less nitrogen than crops. Therefore, the first and second laser beams are hardly reflected from the soil, or even if they are, the amount of light is very small. Therefore, the light receiving signal with a small amount of light can be judged as noise.

[0077] Whether a signal is unnecessary (noise) can be determined based on both the distance measurement result and the light amount detection result.

[0078] Thus, the height of the crop and the nitrogen content of the crop can be obtained as detection signals of the growth state.

[0079] Furthermore, the number of signals obtained for each pulse of light by laser scanning is very large, and noise can be removed from the signals. By calculating the average value of the obtained signals, it is possible to obtain highly accurate and reliable detection of plant growth.

[0080] Furthermore, the growth amount / fertilizer amount calculation unit 11b judges the growth state based on the detection results by the plant sensor 2, i.e., the crop height and the nitrogen content of the crop, and judges whether the crop growth state at the time of detection is good or poor.

[0081] Next, in this embodiment, the amount of fertilizer to be spread is calculated based on the detected growth state, and the fertilizer spreader 3 is controlled to spread the fertilizer.

[0082] The growth amount / fertilizer amount calculation unit 11b receives an input of the growth condition detection result from the plant sensor 2, and further receives an input of the traveling speed of the agricultural machine 1 from the speed detector 25.

[0083] In addition, a fertilizer control program and fertilizer amount comparison data regarding the amount of fertilizer to be applied according to the growth condition are input into the memory unit 12, and the growth amount / fertilizer amount calculation unit 11b calculates the amount of fertilizer to be spread per unit time by the fertilizer spreader 3 based on the detected growth condition, fertilizer amount comparison data, and the traveling speed of the agricultural machine 1, and controls the fertilizer spreader 3 so that fertilizer is spread at this amount.

[0084] In addition, there is a horizontal distance between the growth condition detection position and the fertilization position by the fertilizer spreader 3, and fertilization is performed taking into account the delay time until the fertilization position of the fertilizer spreader 3 reaches the growth condition detection position.

[0085] As described above, the growth condition detection position, i.e., the horizontal distance between the scanning position of the laser scanner 4 and the measurement reference position of the laser scanner 4, can be obtained from the distance (slant distance) measured by the laser scanner 4 and the vertical angle of the distance measurement light. Since the horizontal distance between the measurement reference position of the laser scanner 4 and the fertilization position of the fertilizer spreader 3 is also known, it is possible to obtain the horizontal distance between the growth condition detection position and the fertilization position by the fertilizer spreader 3. In addition, the delay time until the fertilization position of the fertilizer spreader 3 reaches the growth condition detection position can be obtained based on this horizontal distance and the traveling speed of the agricultural machine 1.

[0086] Thus, the growth amount / fertilizer amount calculation unit 11b can scatter an appropriate amount of fertilizer at an appropriate position.

[0087] The GNSS receiver 26 can measure the growth status detection position, and the growth status of the entire field can be grasped and mapped. By mapping the growth status, the growth trend of the entire field can be understood, and this can be used for agricultural planning, such as improving crop planning or soil improvement.

[0088] In the above embodiment, a line scanner is shown as the laser scanner 4 mounted on the plant sensor 2, but the plant sensor 2 may be mounted on, for example, a UAV rather than on the agricultural machine 1. In this case, a laser scanner 4 that scans two-dimensionally may be used to detect the growth state for each predetermined area.

[0089] The flow from growth state detection to fertilization will be explained using Figure 5.

[0090] STEP: 01 When starting fertilization, the conditions required for fertilization are set. For example, the scanning range (length of the scan line: scanning length perpendicular to the traveling direction) by the laser scanner 4 is set. The scanning range is set by setting the reciprocating rotation angle of the scan mirror 39.

[0091] The setting items include the travel speed of the agricultural machine 1, the scanning speed, the interval between pulsed light emissions, the number of scans per detection, etc., and are set appropriately according to the work situation and work environment.

[0092] STEP: 02 The agricultural machine 1 is started to travel, scanning by the laser scanner 4 is started, and fertilization is started.

[0093] STEP:03 A scan is performed in the set range under the set conditions, and scan data is obtained for each scan operation. Note that the scan is performed on one axis of the horizontal rotation axis 41, so the scan is a line scan. If multiple scans are set in the setting for one scan operation, scan data is obtained for each scan.

[0094] STEP:04 The acquired scan data is judged to be correct or incorrect based on the distance measurement value and light quantity value for each pulse of light based on a predetermined threshold, and noise data is deleted from data that is judged to be incorrect. The growth amount is calculated based on the scan data from which the noise has been deleted, and the amount of fertilizer is further calculated based on the growth amount.

[0095] STEP: 05 The calculated amount of fertilizer to be applied is transmitted to the fertilizer spreader 3.

[0096] STEP: 06 The fertilizer spreader 3 spreads fertilizer.

[0097] STEP: 07 The fertilizer spreader 3 spreads fertilizer based on the received fertilizer application amount.

[0098] STEP:08 When the amount of fertilizer to be applied is transmitted to the fertilizer spreader 3, a determination is made as to whether or not the fertilizer application work should be continued. If it is determined that the fertilizer application work should be continued, the process returns to STEP:03, a scan is performed, the scan data is obtained, and the work continues.

[0099] Next, the noise data removal in STEP:04 will be further described with reference to FIG.

[0100] As described above, the validity of the data is judged for each light pulse.

[0101] STEP 11 When the reflected light is received, the amount of reflected light and the distance measurement value are obtained for each wavelength (735 nm, 809 nm).

[0102] STEP 12: The reflected light amount is compared with a threshold value to determine whether it is within the threshold value, i.e., whether the reflected light amount is greater than or less than the threshold value. If it is less than the lower threshold value, it is reflected by soil, and if it is greater than the upper threshold value, it is reflected by, for example, a piece of glass. Either of these is unsuitable as data, so it is determined to be no and is deleted as noise data.

[0103] The reflected light amount may be determined based on the amount of light at each wavelength individually or based on the total amount of light at all wavelengths.

[0104] STEP 13: The measured distance values ​​for each wavelength (735 nm, 809 nm) are compared with the threshold to determine whether they are within the threshold.

[0105] The distance measurement value of each pulse of light varies from leaf to leaf, and also varies when reflected by soil. The distance measurement value is largest when reflected by soil, so it can be determined that a distance measurement value smaller than a predetermined threshold value was obtained by reflection by leaves. Distance measurement data within the threshold is adopted as proper data, and distance measurement data outside the threshold is deleted as noise data.

[0106] STEP 14: The growth amount is calculated, and it is judged whether the calculated growth amount is appropriate. For example, when judging the growth amount by the distance measurement value, the height of the crop is calculated from the distance measurement value, and it is judged whether the height of the crop is within a predetermined threshold value with respect to the average value at the time of growth inspection, or within a threshold value with respect to the height assumed in the growth plan.

[0107] In addition, when judging the growth rate from distance measurements based on the amount of nitrogen contained in the leaves of crops, the nitrogen content is calculated from the ratio of the light intensity at the two wavelengths of 735 nm and 809 nm, and it is determined whether the nitrogen content is within a specified threshold value compared to the average value at the time of growth inspection, or whether it is within the threshold value for the nitrogen content assumed in the growth plan.

[0108] The nitrogen content with respect to the ratio of the amount of light having wavelengths of 735 nm and 809 nm is previously obtained and stored in the storage unit 12 as table data.

[0109] Moreover, if the growth amount obtained from the distance measurement data and the light amount data is significantly outside the threshold range, the measurement data is deemed to be abnormal and is deleted.

[0110] Furthermore, the noise data deletion in STEP: 14 may be omitted depending on the state of the noise data deletion in STEP: 12 and STEP: 13.

[0111] STEP 15: Detect the amount of light when the pulsed light is off to detect dark noise. The dark noise is treated as external light noise and is removed from the amount of light during distance measurement. This improves the S / N ratio.

[0112] STEP:16 By deleting the noise data in STEP:12, STEP:13, and STEP:14, the remaining data becomes only correct data, and by further removing external light noise in STEP:15, the data is stored in the memory unit 12 as high-quality growth data detected by the plant sensor 2.

[0113] STEP 17: The above noise removal is performed for each pulse light, and it is determined whether it has been performed for all the pulse lights of one scan line. If it is determined that noise removal has been performed for all the pulse lights, noise removal for one scan line is completed, and if the fertilization work is to be completed, the detection operation of the plant sensor 2 is stopped. If the fertilization work is to be continued, the acquisition of growth amount data by the plant sensor 2 and noise removal are continued for the next scan operation. [Explanation of symbols]

[0114] 1. Agricultural machinery 2. Plant Sensor 3 Fertilizer spreader 4. Laser scanner 11 Control section 11a Scanner control calculation unit 11b Growth amount / fertilization amount calculation section 12 Storage section 13 Ranging section 14 Light emitting part 15 Light receiving part 16 Light quantity detection section 25 Speed ​​detector 26 GNSS receiver 39 Scan Mirror 45 1st light source 46 Second light source 47 First Wavelength Selective Mirror 52 Second Wavelength Selective Mirror 53 1st receiver 54 2nd receiver

Claims

1. A plant growth detection method in which a laser scanner scans pulsed ranging light consisting of two wavelengths with different reflectivities depending on the nitrogen content, the two wavelengths are separated and received, the ranging value and light amount are detected for each pulsed ranging light and for each of the two wavelengths, the height of the crop is detected based on the ranging values, the ratio of the received light amounts of the two wavelengths is detected, and the growth condition of the crop is detected based on the detected height and ratio of the received light amounts.

2. 2. The method for detecting plant growth according to claim 1, wherein the two wavelengths of the pulsed distance measuring light are 735 nm and 809 nm.

3. A plant growth detection method as described in claim 1 or claim 2, wherein, when detecting the height of a crop based on the distance measurement value, a threshold is set and distance measurement data that falls outside the threshold for each pulse distance measurement light is deleted as noise data, and when detecting the growth state of a crop based on the ratio of received light amounts, a threshold is set for each pulse distance measurement light and received light amount ratio data that falls outside the threshold is deleted as noise data.

4. a light-emitting unit that emits pulse distance measuring light of two wavelengths, a scan mirror that scans the pulse distance measuring light, a light-receiving unit that separates and receives the reflected pulse distance measuring light from the object to be measured for each pulse distance measuring light and for each two wavelengths, and a distance measuring unit that acquires a distance measuring value for each wavelength for each pulse distance measuring light, and a light amount detection unit that detects the received light amount of the reflected pulse distance measuring light received by the light-receiving unit for each pulse distance measuring light, and a growth amount / fertilizer amount calculation unit, wherein the growth amount / fertilizer amount calculation unit detects the distance measuring value and light amount for each pulse distance measuring light and for each two wavelengths, calculates the crop height based on the distance measuring value, detects the ratio of the received light amounts of the two wavelengths, calculates the crop growth state based on the detected height and received light amount ratio, and detects the plant growth amount based on the two calculation results.

5. The plant sensor according to claim 4 , wherein the two wavelengths of the pulsed distance measuring light are 735 nm and 809 nm.

6. The plant sensor described in claim 4 or claim 5, wherein the growth amount / fertilizer amount calculation unit has a threshold value for judging whether the distance measurement data detecting the height of the crop is correct or not, and has a threshold value for judging whether the received light amount ratio data is correct or not, and determines whether the distance measurement data and the received light amount ratio data are correct or not for each pulse of distance measurement light based on the respective threshold values, and eliminates the distance measurement data and the received light amount ratio data that fall outside the threshold values ​​as noise data.

7. A fertilization device comprising the plant sensor of claim 4 provided at the front of an agricultural machine, a fertilizer spreader provided at the rear of the agricultural machine, and a control unit, wherein the control unit determines the amount of fertilizer to be spread based on the amount of plant growth obtained from the plant sensor, and controls the fertilizer spreader to apply fertilizer.

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