Growth condition estimation method and cultivation device

Abstract

To provide a growth state estimation method that can estimate the future growth state of plants, and a cultivation device.SOLUTION: A growth state estimation method comprises: a first step of obtaining a first state quantity corresponding to a light energy absorbed by a plant from the start of planting to a first time point based on the illuminance obtained by an illumination meter; a second step of estimating the mass of the plant at the first time point as a first mass from the first state quantity using a first model; a third step of estimating the mass of the plant at the first time point as a second mass from the elapsed time from the start of planting to the first time point using a second model; a fourth step of modifying the fitting parameters of the second model and creating a modified second model so that the difference between the second mass and the first mass is equal to or less than a predetermined first threshold; and a fifth step of estimating the mass of the plant at a second time point after the first time point using the modified second model.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a growth state estimation method for estimating the growth state of a plant in a cultivation device. [Background technology]

[0002] Patent Documents 1 and 2 disclose a device for optically measuring the growth state of a plant. This device includes a light source that irradiates light toward the plant, an illuminometer that measures the intensity of the light reflected by the plant, and a calculation unit that calculates the growth state of the plant based on the light intensity detected by the illuminometer. This device allows the growth state of the plant to be obtained quickly and without contact. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-076346 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-223101 Summary of the Invention [Problem to be solved by the invention]

[0004] However, while the devices disclosed in Patent Documents 1 and 2 can acquire the current growth state of a plant, they cannot estimate the growth state of the plant at any time in the future. If the future growth state of the plant could be acquired, it would be possible to predict the harvest time and adjust the cultivation conditions.

[0005] In view of the above background, an object of the present invention is to provide a growth state estimation method and a cultivation device that can estimate the future growth state of a plant. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, one aspect of the present invention is a growth state estimation method for estimating the growth state of a plant in a cultivation device (1), the cultivation device having a case (2), a planting plate (3) arranged in the case and on which the plant is planted, a light source (4) that irradiates light toward the planting plate, and an illuminance meter (5) arranged facing the planting plate, the method including: a first step (S1) of acquiring a first state quantity corresponding to light energy absorbed by the plant from the start of planting to a first time point based on the illuminance acquired by the illuminance meter; and a first model that defines the relationship between the first state quantity and the mass of the plant, and estimating the growth state of the plant from the first state quantity to the first time point. a second step (S2) of estimating the mass of the plant at the first time point as a first mass, using a second model that defines the relationship between the time elapsed from the start of planting and the mass of the plant; a third step (S3) of estimating the mass of the plant at the first time point as a second mass from the time elapsed from the start of planting to the first time point using a second model that defines the relationship between the time elapsed from the start of planting and the mass of the plant; a fourth step (S4) of creating a modified second model by modifying fitting parameters of the second model so that the difference between the second mass and the first mass is equal to or less than a predetermined first threshold; and a fifth step of estimating the mass of the plant at a second time point after the first time point using the modified second model.

[0007] According to this aspect, a growth state estimation method capable of estimating the future growth state of a plant can be provided. Because the mass of a plant is correlated with the amount of light energy absorbed, the mass of the plant at a first time point can be estimated as a first mass from a first state quantity using a first model. Furthermore, because the mass of a plant is correlated with the time elapsed since planting, i.e., the cumulative light irradiation time since planting, the mass of the plant at the first time point can be estimated as a second mass using a second model. By correcting the second model so that the difference between the second mass and the first mass is equal to or less than a first threshold, a corrected second model that takes into account the growth state of the plant at the first time point can be obtained. By using the corrected second model obtained in this manner, the mass of the plant at any time point in the future can be accurately estimated.

[0008] In the above aspect, the first model may be created based on state quantities corresponding to the mass of the plant and the light energy absorbed by the plant at each time point, obtained by preliminary cultivation of the plant using the cultivation device.

[0009] According to this aspect, a first model corresponding to the cultivation device can be obtained.

[0010] In the above aspect, the mass of the plant is the edible part mass, which is the mass of the edible part of the plant, and the edible part mass may be estimated from the total mass of the plant using a third model that defines the relationship between the total mass, which is the mass of the entire plant, and the edible part mass.

[0011] According to this aspect, the future edible mass of the plant can be estimated.

[0012] In the above aspect, the plants may be planted on the planting plate at a predetermined pitch, and the first model may be corrected in accordance with the pitch.

[0013] According to this embodiment, the first mass can be estimated with higher accuracy.

[0014] Another aspect of the present invention is a cultivation device (1) for a plant (C), comprising a case (2), a planting plate (3) arranged in the case and on which the plant is planted, a light source (4) that irradiates light toward the planting plate, an illuminance meter (5) arranged facing the planting plate, and a control device (6) connected to the light source and the illuminance meter, wherein the control device acquires a first state quantity corresponding to light energy absorbed by the plant from the start of planting to a first time point based on the light intensity acquired by the illuminance meter, and calculates the mass of the plant at the first time point from the first state quantity using a first model that defines the relationship between the first state quantity and the mass of the plant. The mass of the plant is estimated as a first mass, and using a second model that defines the relationship between the elapsed time from the start of planting and the mass of the plant, the mass of the plant at the first time point is estimated as a second mass based on the elapsed time from the start of planting to the first time point, and fitting parameters of the second model are modified to create a modified second model so that the difference between the second mass and the first mass is equal to or less than a predetermined first threshold.The modified second model is used to estimate the mass of the plant at a second time point after the first time point, and the light source is controlled based on the difference between the mass of the plant at the second time point and a target mass.

[0015] According to this aspect, it is possible to provide a cultivation device that estimates the future growth state of a plant and controls the light source based on the estimated growth state. [Effects of the Invention]

[0016] According to the above aspects, it is possible to provide a growth state estimation method and a cultivation device that can estimate the future growth state of a plant. [Brief explanation of the drawings]

[0017] [Figure 1] Schematic diagram of the cultivation device [Figure 2] Schematic diagram of the planting plate of the cultivation device seen from above [Figure 3] Schematic diagram of the planting plate of the cultivation device seen from above [Figure 4] Flow diagram showing the procedure for growth state estimation processing [Figure 5] Graph showing the relationship between the total mass of frill lettuce and the mass of the edible part [Figure 6] Graph showing the relationship between the total mass of the bok choy plant and the mass of the edible part [Figure 7] Graph showing the relationship between the total mass of wine dress and the mass of the edible portion [Figure 8] Graph showing the relationship between the total mass of Mizuna and the mass of the edible part [Figure 9] Graph showing actual measured values ​​of edible mass of plants measured in preliminary cultivation and an approximate curve based on the first model [Figure 10] Graph showing actual measured values ​​of edible mass of plants measured in preliminary cultivation and an approximate curve based on the second model [Figure 11] A graph showing the actual measured values ​​of the edible mass of plants measured in actual cultivation and the approximate curve (pitch: 200 mm) based on the first model. [Figure 12] A graph showing the actual measured values ​​of the edible mass of plants measured in actual cultivation and the approximate curve (pitch: 150 mm) based on the first model. [Figure 13] Graph showing the estimated mass of the edible part 20 days after planting and the actual measured value at each point in the cultivation (pitch: 200 mm) [Figure 14] Graph showing the estimated mass of the edible portion 20 days after planting and the actual measured value at each point in the cultivation (pitch: 150 mm) DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of a method for estimating a growth state of a plant and a plant cultivation device according to the present invention will be described.

[0019] As shown in Figures 1 and 2, the cultivation device 1 has a case 2, a planting plate 3 that is placed in the case 2 and on which a plant C is planted, a light source 4 that irradiates light toward the planting plate 3, a light meter 5 that is placed facing the planting plate 3, and a control device 6 that is connected to the light source 4 and the light meter 5.

[0020] The case 2 has a nutrient solution pool 11 forming the bottom, a ceiling panel 12 positioned above and spaced apart from the nutrient solution pool 11, and multiple sidewall panels 13 arranged around the nutrient solution pool 11 and ceiling panel 12. A planting plate 3 is placed on top of the nutrient solution pool 11. The planting plate 3 is formed in a flat plate shape with its surfaces facing up and down. Multiple beams may be installed above the nutrient solution pool 11, and the planting plate 3 may be supported by the multiple beams. The multiple sidewall panels 13 are arranged to close the gap between the nutrient solution pool 11 and the ceiling panel 12. The multiple sidewall panels 13 are detachably attached to the nutrient solution pool 11 and the ceiling panel 12. The ceiling panel 12, the sidewall panels 13, and the planting plate 3 define a cultivation chamber 14.

[0021] The surfaces of the ceiling panel 12, the side wall panel 13, and the planting plate 3 facing the cultivation room 14 are made of a material with high reflectivity. The surfaces of the ceiling panel 12, the side wall panel 13, and the planting plate 3 facing the cultivation room 14 are preferably white. The ceiling panel 12, the side wall panel 13, and the planting plate 3 are preferably made of a white material. The ceiling panel 12, the side wall panel 13, and the planting plate 3 may also be painted with white paint. Reflective panels may also be provided on the surfaces of the ceiling panel 12, the side wall panel 13, and the planting plate 3.

[0022] The planting plate 3 may be made of, for example, polystyrene foam. The planting plate 3 has a plurality of holes 16 formed therethrough in the thickness direction. Each hole 16 may be formed in a circular shape. The plurality of holes 16 are spaced apart from one another at a predetermined pitch P. The pitch P may be set to, for example, 50 mm to 300 mm. As shown in FIG. 2, the holes 16 may be arranged at the vertices of an equilateral triangle when viewed from above. Alternatively, as shown in FIG. 3, the holes 16 may be arranged at the vertices of a square when viewed from above.

[0023] A holding material 17 for holding the plants C may be attached to each hole 16. The holding material 17 may be made of a flexible and water-permeable material. The holding material 17 may be made of, for example, urethane foam or rock wool. The holding material 17 has through-holes for the plants C to pass through. The plants C may be held in the holes 16 via the holding material 17.

[0024] The light source 4 is provided on the underside of the ceiling panel 12. The light source 4 is preferably an LED. The LED preferably includes a wavelength range from far-infrared to blue. The LED preferably includes a red LED and a blue LED. The light source 4 may also be other artificial light sources such as an LD (laser diode), a CCFL (cold cathode fluorescent lamp), or a fluorescent lamp. The light source 4 irradiates light downward, i.e., toward the planting board 3.

[0025] The illuminance meter 5 measures the light intensity (photon flux density) [μmol / m 2 The illuminance meter 5 may be a photon sensor that measures [kJ / s]. Alternatively, the illuminance meter 5 may be a general illuminance meter, such as a lux meter, for which correlation with a photon sensor has been confirmed. The illuminance meter 5 includes a plurality of first illuminance meters 5A provided on the underside of the ceiling panel 12 and a plurality of second illuminance meters 5B provided on at least one of the ceiling panel 12 and the side wall panel 13. Each of the first illuminance meters 5A is arranged to face vertically downward. Each of the second illuminance meters 5B is arranged to face at an angle of 5 to 85 degrees relative to the vertically downward. The illuminance meters 5 measure light emitted from the light source 4 and reflected by the planting plate 3, the side wall panel 13, the ceiling panel 12, and the plants C planted on the planting plate 3.

[0026] The nutrient solution pool 11 is connected to a nutrient solution tank 21 via a circulation path 22. The nutrient solution tank 21 stores nutrient solution. The nutrient solution is a solution containing nutrients necessary for the growth of plants C. The circulation path 22 is provided with a pump 23 that transports the nutrient solution, and a nutrient solution adjustment device 24 that adjusts the nutrient solution. The nutrient solution adjustment device 24 adjusts the EC (electrical conductivity) value and pH value of the nutrient solution.

[0027] The cultivation apparatus 1 further includes a CO2 supplying device 26 and an air conditioning device 27. The CO2 supplying device 26 is connected to the case 2 and supplies carbon dioxide to the cultivation room 14. The air conditioning device 27 is connected to the case 2 and adjusts the temperature, humidity, and air volume (wind speed) of the cultivation room 14. The cultivation apparatus 1 may also include a camera 28 that takes pictures of the inside of the cultivation room 14. The camera 28 may be provided, for example, on the ceiling panel 12 and may take pictures of the plants C on the planting plate 3.

[0028] The control device 6 is a computing device having a microprocessor (MPU), non-volatile memory, volatile memory, and an interface. The control device 6 realizes various applications by having the microprocessor execute programs stored in the non-volatile memory. The control device 6 controls the power supply to the light source 4 and the light intensity of the light source 4. The control device 6 acquires the light intensity of the reflected light based on a signal from the illuminance meter 5. The control device 6 also controls the pump 23, the nutrient solution adjustment device 24, the CO2 supply device 26, and the air conditioner 27. The control device 6 may be connected to the light source 4, the illuminance meter 5, the pump 23, the nutrient solution adjustment device 24, the CO2 supply device 26, the air conditioner 27, and the camera 28 via a network such as the Internet. The control device 6 may acquire images captured by the camera 28 and control each device based on the images.

[0029] The plant C cultivated in the cultivation device 1 may be any plant that has leaves and can be grown hydroponically, such as a leafy vegetable. Leafy vegetables are vegetables whose leaves are edible. Examples of the plant C include lettuce, spinach, komatsuna, bok choy, nozawana, and mizuna. The plant C may be leaf lettuce such as frill lettuce, sunny lettuce, wine dress, and green leaf lettuce. The plant C may also be aromatic herbs such as herbs, medicinal herbs, tobacco, wasabi, and hemp. Furthermore, by understanding the correlation between leaf and root growth, it may also be applicable to herbal medicines such as ginseng.

[0030] Plants C, which have grown into seedlings through the sowing process, greening process, and seedling raising process, are planted in each hole 16 of the planting plate 3. Each plant C is held in each hole 16 so that its stems and leaves are located within the cultivation chamber 14 and its roots are located below the planting plate 3. The roots of each plant C extend into the nutrient solution in the pool.

[0031] The plant C grows by absorbing nutrients from the nutrient solution in the pool and light emitted from the light source 4. As the plant C grows, its leaves grow in the cultivation room 14, and its mass increases.

[0032] The control device 6 controls the light source 4, pump 23, nutrient solution adjusting device 24, CO2 supplying device 26, and air conditioning device 27 to maintain the light intensity, temperature, humidity, wind speed, air volume, and CO2 concentration of the cultivation room 14, the EC value and pH value of the nutrient solution, and the nutrient solution circulation flow rate at predetermined cultivation conditions. The plant C is preferably harvested a predetermined period after planting.

[0033] The conditions of the cultivation device 1 are, for example, as shown in the following table. [Table 1]

[0034] The control device 6 estimates the mass of the plant C at any future time point by executing a growth state estimation process for the plant C. The growth state estimation process for the plant C is based on a growth state estimation method for the plant C.

[0035] As shown in Figure 4, the process of estimating the growth state of plant C includes a first step (S1) of acquiring a first state quantity corresponding to the light energy absorbed by plant C from the start of planting to a first time point based on the light intensity acquired by the illuminance meter 5; a second step (S2) of estimating the mass of plant C at the first time point as a first mass from the first state quantity using a first model that defines the relationship between the first state quantity and the mass of plant C; a third step (S3) of estimating the mass of plant C at the first time point as a second mass from the time that has elapsed since the start of planting to the first time point using a second model that defines the relationship between the time that has elapsed since the start of planting and the mass of plant C; a fourth step (S4) of correcting the fitting parameters of the second model to create a corrected second model so that the difference between the second mass and the first mass is equal to or less than a predetermined first threshold; and a fifth step (S5) of estimating the mass of plant C at a second time point after the first time point using the corrected second model.

[0036] In the first step (S1), the control device 6 calculates a first state quantity S corresponding to the light energy absorbed by the plant C from the start of planting (t=0) to the first time point t1 based on the light intensity acquired by the first illuminance meter 5A and the second illuminance meter 5B. h1 , S y1 The first state quantity S h1 is a first state quantity calculated based on the first illuminance meter 5A, and the first state quantity S y1 is the first state quantity calculated based on the second illuminance meter 5B. In another embodiment, the first state quantity is S h1 and S y1 Only one of them may be used.

[0037] After planting, the control device 6 receives the light intensity measured by the first illuminometer 5A and the second illuminometer 5B at predetermined time intervals. The time intervals may be, for example, 1 hour, 12 hours, 24 hours, etc. The first state quantity S at an arbitrary time t after planting is ht is the light intensity P obtained by the first illuminance meter 5A at time t. h [μmol / m 2 / sec], it can be expressed as the following equation (1).

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[0038] Similarly, the first state quantity is the light intensity P obtained by the second illuminance meter 5B at an arbitrary time t after planting. y [μmol / m 2 / sec], it can be expressed as the following equation (2).

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[0039] The control device 6 substitutes the time point t1 for the time t in the formulas 1 and 2 to obtain a first state variable S corresponding to the light energy absorbed by the plant C from the start of planting to the first time point t1. h1 , S y1 Get.

[0040] The above numbers (1) and (2) are created based on the following concept. The plant C has a lower light reflectance than the ceiling panel 12, the side wall panel 13, and the planting plate 3 that define the cultivation room 14. Therefore, when the plant C is planted on the planting plate 3, the light intensity measured by the illuminance meter 5 decreases. Furthermore, as the plant C grows, the area of ​​the plant C covering the planting plate 3 increases, further decreasing the light intensity measured by the illuminance meter 5. Therefore, the difference between the light intensity in a blank state in which the plant C is not planted on the planting plate 3 and the light intensity at a certain point in time after the plant C is planted on the planting plate 3 is considered to correspond to the amount of light energy absorbed by the plant C. The value obtained by integrating this difference over the period from planting to the first time point is considered to correspond to the amount of light energy absorbed by the plant C during the period from planting to the first time point.

[0041] In a second step (S2), the control device 6 estimates the mass of the plant C at a first time point from the first state quantity as a first mass using a first model that defines the relationship between the first state quantity and the mass of the plant C. In this embodiment, the first model is expressed by the following equation (3). The first model is an empirical formula based on past cultivation results.

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[0042] Equation (3) shows that the mass W of a plant C per plant at time t is affected by the mass per plant C at the time of planting, the pitch P, and the first state corresponding to the amount of light energy absorbed by the plant C up to time t.

[0043] The mass W of plant C is the total mass W of plant C. T Or the mass of the edible part of plant C is the edible part mass W E The edible portion mass W E and the total mass W T and have the following relationship (4) (third model).

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[0044] The coefficients φ, μ, α, β, β1, and β2 in equations (3) and (4) may be set based on the results of preliminary cultivation of the same type of plant C using the cultivation device 1. The coefficients may be provided to each control device 6 from a database that aggregates past cultivation results.

[0045] By executing the process of the second step (S2), the control device 6 calculates the mass W of the edible part per plant C at the first time point t1 without directly weighing the plant C. E Based on the relationship of equation (4), the control device 6 calculates the mass W of the edible part per plant C at the first time point t1. E Instead, the total mass W per plant of the plant C at the first time point t1 T may be obtained.

[0046] In a third step (S3), the control device 6 uses a second model that defines the relationship between the time elapsed since the start of planting and the mass of the plant C to estimate the mass of the plant C at the first time point from the time elapsed from the start of planting to the first time point as a second mass. In this embodiment, the second model is expressed by the following equations (5) to (13). The second model is an empirical formula based on past cultivation results, and is created using the Runge-Kutta method.

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[0047] In a fourth step (S4), the control device 6 modifies the fitting parameters of the second model so that the difference between the second mass and the first mass is equal to or less than a predetermined first threshold, thereby creating a modified second model. The modified second model is created by modifying the fitting parameters α1 and α2 of equation (5). The fitting parameters α1 and α2 may be set so that the difference between the second mass and the first mass calculated by the modified second model is minimized. If the difference between the second mass and the first mass calculated by the second model before modification is equal to or less than a predetermined first threshold, changing the fitting parameters α1 and α2 may be omitted.

[0048] In a fifth step (S5), the control device 6 uses the modified second model to estimate the mass of the plant C at a second time point after the first time point. For example, if the planting period is 20 days, the control device 6 may execute the growth state estimation process every day and estimate the mass of the plant C for each day after the execution day, or the mass of the plant C on the 20th day. The mass estimated in the fifth step is the total mass W of the plant C. T or edible portion mass W E It would be good if that were the case.

[0049] The control device 6 may estimate the mass of the plants C on the last day of the planting period, i.e., the target harvest date, and control the light source 4 based on the estimated mass on the target harvest date. For example, if the mass of the plants C on the target harvest date is equal to or less than the target mass, the control device 6 may increase the light intensity of the light source 4 or extend the irradiation time thereafter. If the mass of the plants C on the target harvest date is heavier than the target mass, the control device 6 may advance the target harvest date. The control device 6 may display the estimated future mass of the plants C and the target harvest date on a display.

[0050] According to the above-described embodiment, a growth state estimation method capable of estimating the future growth state of plant C can be provided. Because the mass of plant C is correlated with the amount of light energy absorbed, the mass of plant C at a first time point can be estimated as a first mass from a first state quantity using a first model. Furthermore, because the mass of plant C is correlated with the time elapsed since planting, the mass of plant C at the first time point can be estimated as a second mass using a second model. By correcting the second model so that the difference between the second mass and the first mass is equal to or less than a first threshold, a corrected second model that takes into account the growth state of plant C at the first time point can be obtained. By using the corrected second model obtained in this manner, the mass of plant C at any time point in the future can be accurately estimated.

[0051] (Example) Below, an example of setting the coefficients and fitting parameters of the first, second, and third models will be described.

[0052] (Preliminary cultivation) Frill lettuce was cultivated using the cultivation apparatus 1. Frill lettuce seeds (commercially available: model number L-121 manufactured by Nakahara Seed Co., Ltd.) were used to carry out the sowing process, greening process, and seedling raising process. After the seedling raising process was completed, the seedlings were used as they were to carry out the transplanting process in the cultivation apparatus 1. The sowing process lasted for 2 days, the greening process for 6 days, the seedling raising process for 8 days, and the transplanting process for 20 days. The light source 4 of the cultivation apparatus 1 was an LED. The light source 4 was irradiated continuously for 18 hours a day and was turned off for the remaining 6 hours. Other conditions were as shown in the table below. [Table 2]

[0053] (Relationship between total plant mass and edible mass) Using a planting plate 3 with holes 16 spaced 200 mm apart, cultivation in the planting process of frill lettuce was carried out three times. Also, using a planting plate 3 with holes 16 spaced 150 mm apart as shown in Figure 2, cultivation in the planting process of frill lettuce was carried out once. During the planting process, the total mass W of frill lettuce randomly sampled every day was T and edible portion mass W E was measured using a weighing scale. The results are shown in Figure 5. Figure 5 confirms that for frill lettuce, there is a linear correlation between the total mass and the edible mass during the planting process. Furthermore, no change was observed in the relationship between the total mass and the edible mass when the pitch was 150 mm or when the pitch was 200 mm. During the planting process, the ratio of the edible mass to the total mass was approximately 0.86. For each cultivation result, the coefficient of determination (R 2 ) was 0.98 or more. In addition, when the results of four cultivation runs were combined, the coefficient of determination in the regression analysis between the total mass and the edible mass was 0.99 or more.

[0054] The same experiment as above was carried out for bok choy, wine dress (lettuce), and Mizuna instead of frill lettuce, and the total mass W T and edible portion mass W EThe results are shown in Figures 6 to 8. Figures 6 to 8 confirm that, similar to frill lettuce, there is a linear correlation between the total mass and the edible mass during the planting process for bok choy, wine dress, and mizuna. During the planting process, the ratio of edible mass to total mass was approximately 0.73 for bok choy, approximately 0.82 for wine dress, and approximately 0.81 for mizuna. The coefficient of determination (R 2 ) was 0.98 or higher.

[0055] A linear correlation between total mass and edible mass during the planting process was confirmed for frill lettuce, bok choy, wine dress, and mizuna. Based on the results for frill lettuce, bok choy, wine dress, and mizuna, it is believed that a linear correlation between total mass and edible mass during the planting process also exists for other plants with different leaf shapes or leaf colors. Based on the above, the linear correlation between total mass and edible mass during the planting process can be applied to leaf lettuce such as sunny lettuce and green leaf lettuce, as well as leafy vegetables other than leaf lettuce.

[0056] (Determining the parameters of the first model) Preliminary cultivation of frill lettuce in the planting process was carried out using a planting plate 3 with holes 16 spaced 200 mm apart. During the preliminary cultivation, the light intensities detected by the first illuminance meter 5A and the second illuminance meter 5B were obtained every day. In addition, the weight scale was used to measure the edible mass W of frill lettuce randomly sampled every day. E was measured.

[0057] The results are shown in Figure 9. Figure 9 shows the change in the edible mass W of frill lettuce over time since planting. E The measured values ​​in Figure 4 were approximated by the first model (Equation 3), and φ, μ, β, β1, and β2 in Equation 3 were determined. In this case, the pitch P was set to 200 mm, and the standard mass W of the edible part of the plant per plant at the time of planting (t = 0) was set to E0 is the mass of the edible part of the plant per plant at planting time (t = 0), w E0 (W E0=w E0 ) In this case, the values ​​of φ, μ, β, β1, and β2 in Equation 3 were set by the least squares method so that the difference between the actual data and the approximation curve based on Equation 3 would be minimized. The approximation curve based on the first model (Equation 3) is shown in Figure 9. It was confirmed from Figure 4 that the approximation curve based on Equation 3 roughly matches the actual data.

[0058] (Determining the parameters of the second model) The actual data in FIG. 9 is approximated by the second model (Equations 5 to 13), and each parameter α1, α2, g, n, α γ , Dx Pitch0 At this time, the pitch P was set to 200 mm, and the standard mass W of the edible part of the plant per plant at the time of planting (t = 0) was determined. E0 is the mass of the edible part of the plant per plant at planting time (t = 0), w E0 (W E0 =w E0 ) In addition, γ = 1. The approximation curve based on the second model is shown in Figure 10. From Figure 10, it can be confirmed that the approximation curve based on the second model generally matches the actual data.

[0059] (Actual cultivation) Below, we used the cultivation device 1 to conduct actual cultivation of frill lettuce and confirmed the effectiveness of the first, second, and modified second models. In the actual cultivation, the pitch was set to 200 mm or 150 mm, and other conditions were the same as those for the preliminary cultivation described above. In addition, the angle of the second illuminance meter 5B relative to the vertical downward direction was set to 5 degrees.

[0060] (Verification of the first model) After planting, several plants were randomly selected each day and the edible mass w was measured using a weighing scale. EThe light intensity of the reflected light was also measured every day using the first illuminance meter 5A and the second illuminance meter 5B. The results are shown in Figures 11 and 12. Figure 11 shows the estimated edible portion mass curve when the pitch is 200 mm and the actual measured edible portion mass. Figure 12 shows the estimated edible portion mass curve when the pitch is 150 mm and the actual measured edible portion mass. The results in Figures 11 and 12 confirmed that the estimated edible portion mass obtained from the first model showed a high degree of agreement with the actual measured value. It was also confirmed that the estimated edible portion mass could be obtained with high accuracy even when the pitch changed.

[0061] (Verification of the revised second model) Based on the results obtained from the actual cultivation, the growth status was estimated, and a modified second model was created for each day to estimate the edible mass W of frill lettuce 20 days after planting. E Figure 13 shows the estimated values ​​when the pitch is 200 mm, and Figure 14 shows the estimated values ​​when the pitch is 150 mm. Figures 13 and 14 confirm that the estimated values ​​based on the modified second model generally match the measured values.

[0062] Although the description of the specific embodiment has been completed above, the present invention is not limited to the above embodiment and can be widely modified and implemented. For example, the predicted mass W after a predetermined time has elapsed since the start of planting, which is obtained at any time by the growth state estimation process, can be calculated as follows: n and the predicted mass W obtained last time n-1 The difference ΔW between the calculated mass and the actual mass is calculated, and if the calculated difference ΔW is equal to or greater than the predetermined judgment value, the predicted mass is calculated as W n If the calculated difference ΔW is less than the predetermined judgment value, the predicted mass is calculated as W n-1 may be adopted. [Explanation of symbols]

[0063] 1:Cultivation equipment 2: Case 3: Planting board 4:Light source 5:Luminance meter 5A: 1st illumination meter 5B: 2nd illuminance meter 6: Control device 11: Nutrient solution pool 12: Ceiling panel 13: Side wall panel 14:Cultivation room 16: Hole 17: Retaining material 21: Nutrient solution tank 22: Circulation path 23: Pump 24: Nutrient solution adjusting device 26:CO2 supply device 27:Air conditioner

Claims

1. A growth state estimation method for estimating a growth state of a plant in a cultivation device, comprising: The cultivation device includes a case, a planting plate disposed in the case and on which the plants are planted, a light source that irradiates light toward the planting plate, and an illuminance meter disposed facing the planting plate, a first step of acquiring a first state quantity corresponding to light energy absorbed by the plant from the start of planting to a first time point based on the light intensity acquired by the illuminometer; a second step of estimating a mass of the plant at the first time point from the first state quantity as a first mass using a first model that defines a relationship between the first state quantity and a mass of the plant; a third step of estimating, as a second mass, the mass of the plant at the first time point based on the time elapsed from the start of planting to the first time point using a second model that defines the relationship between the time elapsed from the start of planting and the mass of the plant; a fourth step of correcting fitting parameters of the second model to create a corrected second model so that the difference between the second mass and the first mass is equal to or less than a predetermined first threshold; and a fifth step of estimating the mass of the plant at a second time point after the first time point using the modified second model.

2. The growth state estimation method according to claim 1, wherein the first model is created based on state quantities corresponding to the mass of the plant and the light energy absorbed by the plant at each point in time, which are obtained by preliminary cultivation of the plant using the cultivation device.

3. The mass of the plant is an edible part mass, which is the mass of the edible part of the plant; The growth condition estimation method according to claim 1 or 2, wherein the edible part mass is estimated from the total mass of the plant using a third model that defines the relationship between the total mass, which is the mass of the entire plant, and the edible part mass.

4. The plants are planted on the planting plate at a predetermined pitch, 4. The growth state estimation method according to claim 1, wherein the first model is corrected in accordance with the pitch.

5. A plant cultivation device, comprising: Case and a planting plate disposed in the case and on which the plants are planted; A light source that irradiates light toward the planting plate; A luminance meter arranged facing the planting plate; a control device connected to the light source and the illuminance meter; The control device acquiring a first state quantity corresponding to light energy absorbed by the plant from the start of planting to a first time point based on the light intensity acquired by the illuminometer; using a first model that defines a relationship between the first state quantity and a mass of the plant, estimating a mass of the plant at the first time point from the first state quantity as a first mass; using a second model that defines the relationship between the time elapsed from the start of planting and the mass of the plant, estimating the mass of the plant at the first time point from the time elapsed from the start of planting to the first time point as a second mass; modifying fitting parameters of the second model so that the difference between the second mass and the first mass is equal to or less than a predetermined first threshold, thereby creating a modified second model; using the modified second model to estimate the mass of the plant at a second time point that is later than the first time point; A cultivation device that controls the light source based on the difference between the mass of the plant at the second time point and a target mass.

6. The cultivation device according to claim 5, wherein the control device creates the first model and the second model based on state quantities corresponding to the mass of the plant and the light energy absorbed by the plant at each time point, which are obtained by preliminary cultivation of the plant using the cultivation device.

7. The mass of the plant is an edible part mass, which is the mass of the edible part of the plant; The cultivation device according to claim 5 or 6, wherein the control device estimates the edible portion mass from the total mass of the plant using a third model that defines the relationship between the total mass, which is the mass of the entire plant, and the edible portion mass.

8. The plants are planted on the planting plate at a predetermined pitch, The cultivation device according to any one of claims 5 to 7, wherein the control device corrects the first model according to the pitch.

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