Method for selectively applying hot fluid on undesired plants on a cultivated field

Abstract

The invention relates to a method for selectively applying hot fluid on an area of a cultivated field (100) using a moving agricultural vehicle including a fluid delivery equipment (200). The method comprising the steps of: capturing images of the cultivated field (100) ahead of the fluid delivery equipment (200) while the agricultural vehicle is moving in the travel direction (202), wherein the images contain various kinds of plants such as plants to removed (114, 116), cultivated plants (112) and ground (110); processing said images to identify the position of each plant in the coordinate system of the fluid delivery equipment (200), and at least one plant parameter of each plant for determining a number of hot fluid applications, ranging from zero to N, to be applied on each plant to be eradicated based on said at least one plant parameter, and continuously tracking the position of each plant in said coordinate system while the agricultural vehicle moves over the cultivated field (100) and timely selectively controlling electro-valves (456) of N arrays (250, 252) of electromechanical nozzles to apply said number of hot fluid applications on the plants to be eradicated, wherein each fluid application is applied by an electromechanical nozzle of a different array (250, 252) when the number of applications exceeds one. The invention also relates to an agricultural vehicle comprising a fluid delivery equipment (200) adapted to implement the above method.

Description

Method for selectively applying hot fluid on undesired plants on a cultivated fieldField of the invention

[0001] The present invention concerns the field of agriculture plant treatment and more particularly a method for selectively applying hot fluid only on undesired plants for weeding purpose, with the ability to optimize the amount and usage of hot fluid in function of the parameters of the plant to target. The invention also concerns an agricultural vehicle comprising a fluid delivery equipment configured to implement such method and to optimize the amount of energy needed to produce the hot fluid.Description of related art

[0002] In some plant treatment applications, such as organic farming, the usage of the majority of chemicals is not allowed. Alternative approaches have been developed and used. For weeding (destroying undesired plants), thermal techniques, such as applying hot water or water steam on the plants to destroy them, have been used since decades.

[0003] Recent advances in agricultural systems include the so-called smart sprayers, using cameras and artificial vision and intelligence to detect and recognize targets ahead of the spray bar, for instance weeds, and electrically controlled nozzles mounted on the spray bar that are opened when the targets to spray pass under the nozzles. The resulting spraying operation is called spot spray. Contrary to full or broad or blanket spray operation, the spot spray is applied only on the targets to be sprayed, for example weeds. This results in important savings in chemicals being used.

[0004] Such selective application systems can also be used to apply thermal energy, for instance hot water, only on the plants to be destroyed. The principle is the same than for smart sprayers, except that instead of a jet of chemicals being applied, a jet of thermal energy, for instance hot wateror water steam, is selectively applied to plants having previously been detected and identified as undesirable.

[0005] In such systems, there is a need to get the highest possible spatial resolution and temporal precision of hot liquid application thanks to the smallest possible spot size with their position controlled with the utmost precision. This allows for instance to hit very small weeds with the minimal amount of hot liquid, or to hit a weed located very close to a crop plant without damaging it.

[0006] Small spot spray is achieved by a small spray divergent angle, and a small distance from nozzle to the target. The spray bar must therefore be positioned at a low height from ground.

[0007] High precision spot spray positioning depends on precise 3D position estimation (mapping) of the target to be sprayed, in the 3D coordinate system of the spray bar, and precise 3D tracking of the position of the target to be sprayed, from the time of the camera acquisition to the time of the spray application. Accurate target mapping is obtained by a combination of high-quality image acquisition by the camera, short camera exposure time to avoid movement blur, high pixel resolution, camera intrinsic calibration to compensate for errors between pixel and image place coordinates, and camera extrinsic calibration to accurately measure the camera position in the machine coordinate system.

[0008] Precise lateral spray positioning requires high spatial resolution nozzle array using high density of individually controlled nozzles by unit of spray bar width.

[0009] In systems applying hot fluids, such as hot water, the amount of energy needed to heat the fluid, and the amount of fluid itself, can be very important and usually limits the usage of such equipment to small areas to be processed. Reducing the amount of fluid can be obtained by the above-mentioned techniques of selectively applying liquid only on the plants to be destroyed, and not on the whole ground.

[0010] However, the sensitivity of plants to thermal energy strongly varies in function of their physical parameters, such as their size and species, but also in function of environmental parameters such as ambient air, soil temperature and moisture, properties of soil, etc. For instance, the quantity of water to destroy a small plant very sensitive to heat can be much smaller than for destroying a well-developed plant with resistant leaves and a well- established root system.

[0011] There is therefore a strong need to modulate the amount of hot fluid in function of the detected physical parameters of the plant and in function of ambient conditions.

[0012] Another aspect in optimizing the efficiency of thermal plant treatment is to keep the fluid as warm as possible until it gets into contact with the plant to be destroyed. The fluid temperature must be maximal when it leaves the dispensing devices, for instance nozzles, but it must also not cool down between the nozzle and the target plant.Brief summary of the invention

[0013] An aim of the present invention is therefore to propose a method for selectively applying hot fluid on undesired plants with the highest precision and the lowest amount of hot fluid.

[0014] Another aim of the present invention is to propose an agricultural vehicle comprising a fluid delivery equipment configured to implement such method.

[0015] These aims are achieved notably by a method for selectively applying hot fluid on an area of a cultivated field using an agriculturalvehicle including a fluid delivery equipment comprising a fluid storage tank for storing hot fluid, and N parallel arrays of electromechanical nozzles and a hot fluid distribution system. The electromechanical nozzles comprise each an electro-valve and a nozzle. The electromechanical nozzles of each array are spaced apart from each other along their respective array by a constant pitch distance. The positions of respective electromechanical nozzles along one array are either aligned with the positions of respective electromechanical nozzles along another array, or offset from the positions of respective electromechanical nozzles along another array by an offset distance whose value preferably equals said pitch distance divided by N.

[0016] The fluid delivery equipment further comprises a hot fluid distribution system configured to distribute hot fluid from the fluid storage tank to the electro-valves of the electromechanical nozzles of said N arrays.

[0017] The method comprises the steps of:- capturing images of the cultivated field ahead of the fluid delivery equipment while the agricultural vehicle is moving in the travel direction, wherein the images contain the ground, plants to be eradicated and cultivated plants;- processing said images to identify the position of each plant in the coordinate system of the fluid delivery equipment, and at least one plant parameter of each plant for determining a number of hot fluid applications, ranging from zero to N, to be applied on each plant to be eradicated based on said at least one plant parameter, and- continuously tracking the position of each plant in said coordinate system while the agricultural vehicle moves over the cultivated field and timely selectively controlling the electro-valves of said N arrays of electromechanical nozzles to apply said number of hot fluid applications on the plants to eradicated, wherein each fluid application is applied by anelectromechanical nozzle of a different array when the number of applications exceeds one.

[0018] In an embodiment, one or more plant parameters is / are selected among plant species, plant widths, plant height and distance of the plant to a cultivated plant.

[0019] In an embodiment, the determination of the number of hot fluid applications to be applied to a given identified plant to be removed is based on the distance between this plant and a cultivated plant such that the number of hot fluid applications is respectively zero, one, or two if said distance is respectively smaller than a first threshold, is comprised between said first threshold and a second threshold larger than said first threshold, and is comprised between said second threshold and a third threshold larger than said second threshold.

[0020] In an embodiment, the number of hot fluid applications is also determined based on at least one environmental parameter selected among ambient air temperature, ambient air moisture, sun irradiance, soil temperature and soil moisture.

[0021] In an embodiment, N equals two, three and four respectively and said said offset distance between two arrays equals respectively half, a third and a fourth of said pitch distance.

[0022] In an embodiment, the electromechanical nozzles of the arrays are controlled by the nozzle control unit to select electromechanical nozzles whose lateral positions are the most suited to deliver hot fluid only on the plant to be eradicated and not on adjacent cultivated plants. The number of selected nozzles corresponds to the number of successive hot fluid applications determined for the plant.

[0023] In an embodiment, the electro-valves of the electromechanical nozzles are further controlled to be opened and closed at a frequency between 30 and 100 Hz during the interval the electromechanical nozzles are dispensing fluid to provide a variable volume of hot fluid. The frequency is chosen within this interval according to one or more plant parameters of the plant to be eradicated.

[0024] In an embodiment, the height of electromechanical nozzles from the ground is controlled by a height control unit of the fluid delivery equipment based on the height of the plant to be eradicated to reduce the distance between the nozzle spout and the plant below a predetermined threshold so as to limit heat loss in the fluid in contact with the air.

[0025] In an embodiment, the hot fluid is water.

[0026] In an embodiment, the temperature of the water within the fluid storage tank is between 80°C and 100°C.

[0027] In an embodiment, the water contains at least one phase-change material (PCM) such as salt hydrates to heat the fluid circulating in the hot fluid distribution system.

[0028] In an embodiment, each nozzle of each array comprises a nozzle inlet, an elongated outlet surface having a plurality of nozzle outlets, and a branched fluidic network in fluid communication with the nozzle inlet and the nozzle outlets.

[0029] Another aspect of the invention relates to an agricultural vehicle for applying hot fluid on a cultivated field. The agricultural vehicle comprises a fluid delivery equipment having at least one array of electromechanical nozzles comprising each a nozzle and an electro-valve, a fluid storage tank for storing hot fluid, a hot fluid distribution system and a nozzle control unit.

[0030] The hot fluid distribution system is configured to distribute hot fluid from the fluid storage tank to inlet of the electro-valves of respective electromechanical nozzles of said at least one array. The nozzle control unit is arranged to control the electro-valve of said at least one array of electromechanical nozzles to deliver hot fluid on plants to be eradicated. The hot fluid distribution system comprises a closed circuit and a recirculating pump to recirculate the hot fluid in the closed circuit. A heating element is arranged to heat the fluid circulating along a heating zone of the closed circuit and a temperature sensor arranged to measure the temperature of the fluid flowing downstream said heating zone to control the heating element so as to maintain the fluid at a predetermined temperature.

[0031] In an embodiment, the agricultural vehicle further comprises another temperature sensor arranged upstream the heating zone to measure the temperature of the fluid dispensed by the fluid storage tank so as to control the heating element also according to said temperature.

[0032] In an embodiment, the hot fluid distribution system comprises a fluid buffer mounted downstream the heating zone and upstream the electrovalves of the at least one array of electromechanical nozzles.

[0033] In an embodiment, the heating element is in the form of an electric heater arranged inside a portion the closed circuit through which the hot fluid is intended to flow.

[0034] In an embodiment, the fluid storage tank comprises an air compressor mounted to pump air from outside into the fluid storage tank to pressurize the hot fluid within the tank. The storage tank further comprises a pressure sensor to measure the pressure inside the tank. The pressure sensor is in communication with the air compressor so that the latter may be driven so as to maintain a constant pressure within the storage tank independently of the fluid level in the tank.

[0035] In an embodiment, the fluid delivery equipment of the agricultural vehicle further comprises at least a first and a second array of electromechanical nozzles comprising each an electro-valve and a nozzle, a camera system, a processing unit and a tracking unit. The electromechanical nozzles of both the first and second arrays are spaced apart from each other along their respective array by a constant pitch distance. The positions of respective electromechanical nozzles along the first array are offset from the positions of respective electromechanical nozzles along the second array by an offset distance comprised between zero and half said constant pitch distance.

[0036] The camera system comprises one or more camera modules arranged to capture images of the cultivated field ahead of the fluid delivery equipment in the travel direction of the agricultural vehicle. The images contain the ground of the cultivated field and various kinds of plants such as plants to be eradicated and cultivated plants.

[0037] The processing unit is configured to run an image recognition software to identify and to classify the plants on the captured images according to their sizes and species, and to generate a mapping of these plants on the coordinate system of the fluid delivery equipment. The tracking unit is arranged for continuously tracking the position of each plant on the mapping of the plants. The nozzle control unit is arranged in communication with the processing unit and the tracking unit to timely selectively control the electro-valve of first and second arrays of electromechanical nozzles to apply hot fluid on the plants to be eradicated.

[0038] In an embodiment, each nozzle of the alt least one array of electromechanical nozzles comprises a nozzle inlet in fluid communication with the corresponding electro-valve, an elongated outlet surface provided with an array of nozzle outlets and a branched fluidic network in fluid communication with the nozzle inlet and the nozzle outlets. Each nozzlecomprises preferably from 4 up to 32 outlets distributed linearly along the elongated outlet surface.

[0039] In an embodiment, the branched fluidic network is configured such that the hot fluid flowing out of the nozzles outlets is not divergent.

[0040] In an embodiment, the branched fluidic network and the nozzle outlets are configured such that the fluid that may be delivered by each nozzle outlet has the same volumetric flow. The fluid pressure at the nozzle outlets is preferably ranging from zero to three bars.

[0041] In an embodiment, the branched fluidic network comprises multiple levels of flow divisions.

[0042] In an embodiment, the nozzle inlet comprises a calibrated hole upstream the branched fluidic network to regulate the flow.

[0043] In an embodiment, the elongated outlet surface of each nozzle has a length corresponding to the distance between two electromechanical nozzles. Each nozzle is arranged next to each other such that their respective elongated outlet surface form together a quasi-continuous outlet surface aligned along a direction perpendicular to the travel direction of the agriculture vehicle when operating.

[0044] Another aspect of the invention relates to a nozzle for an agricultural vehicle, comprising a nozzle inlet, an elongated outlet surface provided with nozzle outlets and a branched fluidic network in fluid communication with the nozzle inlet and the nozzle outlets.

[0045] In an embodiment, the number of the nozzle outlets is selected from 4 to 20.

[0046] In an embodiment, the nozzle outlets are aligned along the elongated outlet surface.

[0047] In an embodiment, the branched fluidic network and the nozzle outlets are configured such that the fluid that may be delivered by each outlet nozzle has the same volumetric flow.

[0048] In an embodiment, the branched fluidic network comprises at least three levels of flow divisions.

[0049] In an embodiment, the nozzle inlet comprises a calibrated hole upstream the branched fluidic network to regulate the flow.Brief Description of the Drawings

[0050] The invention will be better understood with the aid of the description of embodiments given by way of examples and illustrated by the figures, in which:Figure 1 shows a schematic perspective view of the fluid delivery equipment of the agricultural vehicle operating on the cultivated field;Figure 2 shows a schematic top view of two arrays of electromechanical nozzles of the fluid delivery equipment of Figure 1 with the resulting patterns of hot fluid application on plants with two modes of operation of the fluid delivery equipment;Figure 3 shows a perspective view of a nozzle used to dispense the hot fluid;Figure 4 shows a front view of Figure 3;Figure 5 shows a cross-section view of Figure 4 along A-A, andFigure 6 shows a schematic view of the hot fluid preparation system of the fluid delivery equipment of the agricultural vehicle.Detailed description of possible embodiment of the invention

[0051] With reference to Figure 1, the agricultural vehicle comprises a fluid delivery equipment 200 adapted to move over a cultivated field 100 comprising cultivated plants 112 and undesired plants 114, 116, such as weeds. As described in detail thereafter, the fluid delivery equipment 200 is configured to selectively apply hot fluid on the undesired plants 114, 116 to eradicate them by at least a first and a second array 250, 252 of electromechanical nozzles arranged in parallel. The hot fluid is preferably hot water. Each electromechanical nozzle comprises an electro-valve 456 and a nozzle 300 whose characteristics will be described subsequently in relation to Figures 3 to 5.

[0052] As best shown in Figure 2, the electromechanical nozzles of the first array 250 are spaced apart from each other by a constant pitch distance 264. The electromechanical nozzles of the second array 252 are spaced apart from each other by the same constant pitch distance 264. In addition, the positions of respective electromechanical nozzles along the first array 250 are laterally offset from the positions of respective electromechanical nozzles along the second array 252 by an offset distance 266 corresponding to half the pitch distance 264. This specific arrangement of electromechanical nozzles of the fluid delivery equipment 200 advantageously improves the lateral resolution of the spot of hot fluid delivered by the nozzles.

[0053] In a non-illustrated embodiment, the lateral resolution of the spots of hot fluid can further be improved with a fluid delivery equipment comprising three or even four arrays of electromechanical nozzles arranged parallelly from each other. For a fluid delivery equipment comprising three arrays of electromechanical nozzles, the offset distance between the positions of respective electromechanical nozzles of the first, second and third array corresponds to a third of the pitch distance between adjacent electromechanical nozzles of each array while said offset distancecorresponds to a fourth of said pitch distance for a fluid delivery equipment with four arrays of electromechanical nozzles.

[0054] A four-arrays fluid delivery equipment is therefore capable of applying spots of hot fluid with twice the lateral resolution of spots of hot fluid that can be applied with the fluid delivery equipment 200 of Figure 1.

[0055] More generally, in a fluid delivery equipment comprising N parallel arrays of electromechanical nozzles, the positions of the nozzles in each array are staggered relative to those in the other arrays by an offset distance equal to the pitch distance divided by N.

[0056] According to another embodiment, the offset distance between adjacent electromechanical nozzles within each array may be less than or greater than one-half, one-third, one-fourth, and so on, of the pitch distance between adjacent nozzles. This applies to fluid delivery equipment comprising two, three, four, or more arrays of electromechanical nozzles, respectively.

[0057] Referring to Figure 1, the fluid delivery equipment 200 further comprises a camera system 220, a processing unit 230 to process images acquired by the camera system to identify each plant 112, 114, 116 on the cultivated field 100, and a tracking unit 235 to track the position of the plants while the agricultural vehicle is moving on the cultivated field in the travel direction 202. The fluid delivery equipment 200 further comprises a height control unit 270 to control the height of the first and a second array 250, 252 of electromechanical nozzles and a nozzle control unit 280 to selectively control the electro-valve 456 of each electromechanical nozzle.

[0058] The camera system 220 comprises one or more camera modules 222 arranged to capture images of the cultivated field 100 in the field of view 224 of the camera module. The captures images contain the cultivated plants, i.e. crops 112, plants to be removed 114, 116 and ground 110. Thesecamera modules are typically equipped with 2D imaging sensors and with 3D range sensors that can map every point of the 2D image in the 3D coordinate system of the fluid delivery equipment 200. Alternatively, the camera module or each camera module may comprise at least two cameras arranged to acquire simultaneously respectively a first and a second set of images of the ground ahead of the fluid delivery equipment, and a stereovision computing unit configured to compute the depth map of the objects as a function of said first and second sets of images.

[0059] The processing unit 230 is adapted to run an image recognition software to identify and to classify the plants 112, 114, 116 on the captured images according to their sizes and species, and to generate a mapping of these plants on the coordinate system of the fluid delivery equipment 200. The image recognition software uses machine learning techniques trained to classify the plants into classes based on whether the plant must be eradicated with application of hot fluid. The image recognition software is also capable of identifying one or more parameters of the plants 114, 116 to be eradicated in order to compute the number of hot fluid applications which are needed. The plant parameters may be for example plant species, plant size, and the distance between the plant to be eradicated and a crop 112.

[0060] The nozzle control unit 280 is arranged in communication with the processing unit 230 and the tracking unit 235 to timely selectively control the electro-valve 456 of the first and second arrays 250, 252 of the electromechanical nozzles to apply hot fluid on the plants to be eradicated. The computing power of the processing unit 230 allows to run the image recognition software to identify the plants 114, 116 to be eradicated as well as one or more plant parameters to compute the number of hot fluid applications within a time interval shorter than the time needed for a zone of the cultivated field to move from the camera field of view to the position of the first array 250 of electromechanical nozzles.

[0061] In an embodiment, the fluid delivery equipment comprises or receives information from one or more sensors to measure environmental parameters such as ambient air temperature, ambient air moisture, sun irradiance, soil temperature and soil moisture. The processing unit is configured to compute the number of hot fluid applications based not only on one or more plant parameters but also on one or more of these environmental parameters.

[0062] The time interval separating two hot fluid applications on the same plant corresponds to the time needed for an object to move over the forward distance separating the first 250 from the second 252 array of electromechanical nozzles of the fluid delivery equipment 200. This short time maximizes the cumulative thermal effect of the two successive applications.

[0063] The speed of the agriculture vehicle should however be adapted to ensure enough time for generating the mapping of the plants 114, 116 to be eradicated on the coordinate system of the fluid delivery equipment 200. In an embodiment, the camera system 220 may be tilted to capture images of zones of the cultivated field 100 further away to increase the distance between the captured images and the fluid delivery equipment to be able to increase the speed of the agricultural vehicle for higher throughput. The quality of the capture images is however poorer when acquired from a further distance. This impacts the accuracy of the detected plants and therefore the precision of hot fluid applications. A compromise between the precision of hot fluid applications and the throughput of the fluid delivery equipment must therefore be found.

[0064] As shown in Figure 2, the species of the plant 116 has been identified as a plant to be eradicated by the image recognition software which has further determined its size. Based on the data of the tracking unit 235, the nozzle control unit 280 commands first the electro-valve of two adjacent electromechanical nozzles of the first array 250 to apply twoadjacent spots 260 of hot fluid on the plant 116 and subsequently the electro-valve of one electromechanical nozzle of the second array 252 to apply another spot 262 of hot fluid on the plant 116. The hot fluid spot 268 is the result of two applications of hot fluid which may be needed to eradicate completely the plant 116.

[0065] There is therefore a time lag between the application of hot fluid spots 260 and hot fluid spot 262 which depends on the speed of the agricultural vehicle, typically a few tenths of milliseconds. The effect of applying a doubled dose of hot fluids at a very short interval has a positive effect on plant destruction efficiency, due to the cumulative effect of heat transfer.

[0066] Accordingly, in the context of the present invention, multiple fluid applications, such as two, three or more, used to eradicate a plant are fluid applications that are overlapping on the plant. For instance, with reference to Figure 2, the hot fluid spot 268 which eradicates plant 116, results from the two non-overlapping fluid applications corresponding to the two adjacent spots 260 applied by two adjacent electromechanical nozzles of the first array 250 and from the subsequent application corresponding to the spot 262 applied by an electromechanical nozzle of the second array 252. The two non-overlapping fluid applications shall therefore be interpreted as a single application within the context of the invention. The hot fluid spot 268 is therefore the result of two successive fluid applications.

[0067] The small plant 114 closest to the crop 112 may receive only one application of hot fluid to avoid any spattering of hot fluid on the nearby crop 112. The processing unit 130 may therefore compute the number of hot fluid applications on the plant to be eradicated not only based on its species but also on its distance to a crop. For example, in case the plant 114 to be eradicated is too close to a crop 112, i.e. the distance between the plant 114 and the crop 112 is below a first threshold, the processing unit 130 would send to the nozzle control unit 280 instructions not to apply any dose of hotfluid to prevent any harm to the crop. The plant 114 is therefore left to avoid causing any harm to the crop.

[0068] In the situation where the distance between the plant 114 to be eradicated and the crop 112 is between the first threshold and a second larger threshold larger, the processing unit 130 would send to the nozzle control unit 280 instructions to apply only one dose of hot fluid. If the distance between the plant 114 to be eradicated and the crop 112 is between the second threshold and a third larger threshold, the processing unit 130 would send to the nozzle control unit 280 instructions to apply two doses of hot fluid. For larger distances, the processing unit may send to the nozzle control unit 280 instructions to apply three or more doses of hot fluids provided that the fluid delivery equipment comprises three or more arrays of electromechanical nozzles.

[0069] This specific arrangement of electromechanical nozzles of the fluid delivery equipment 200 as described previously allows to selectively control the electro-valve of electromechanical nozzles of either the first or second array 250, 252 depending on the position of the plants 114, 116 to precisely target the plants to be eradicated. For instance, starting from the left on Figure 2, the first and the fourth electromechanical nozzles of the first array 250 are activated to apply the hot fluid spot 260 on the plants 114a, 114b while the first and the third electromechanical nozzles of the second array 252 are activated to apply the hot fluid spot 264 on the plants 114c, 114d which are slightly laterally offset from the plants 114a, 114b.

[0070] The fluid delivery equipment 200 of Figure 1 may therefore operate in two different modes. In the first mode, the electromechanical nozzles of the first and second arrays 250, 252 are controlled as a single array, at the exception that the difference of nozzle position of the two arrays in the forward direction is taken into account by the nozzle control unit 280 in order to deliver hot fluid at the right moment independently of the speed of the agricultural vehicle.

[0071] In this first mode, each nozzle dispenses hot fluid on a width corresponding to the nozzle pitch of a single array, however the lateral spatial resolution of the nozzles, in other words their correct lateral placement, has a pitch two times smaller. This maximizes the resolution of the fluid delivery equipment to precisely target small plants or plants located laterally very near a crop.

[0072] The second mode of the fluid delivery equipment 200 uses the first and second arrays 250, 252 of the electromechanical nozzles as two independent arrays able to apply each the same hot fluid jet to a given plant, resulting in doubling the applied hot fluid dose per unit area, at the cost of a reduced lateral spatial resolution. Indeed, in this mode, the lateral resolution corresponds to the nozzle-to-nozzle distance of respective first and second arrays 250, 252.

[0073] Both modes can be mixed at any time depending on the kind of plant, and the choice of the mode will be done on a plant-by-plant basis according to one or more plant parameters of the plant to be eradicated. The first mode will be preferred for small plants to be destroyed, for which a single application of hot fluid is sufficient to destroy the plant. It will also be preferred for plants sensitive to heat that are known to be easily destroyed by heat even when they have grown bigger. The second mode will be preferred for larger plants, or for plants species recognized by the image recognition software as more resistant to heat to be destroyed.

[0074] In a non-illustrated embodiment, the fluid delivery equipment may comprise two or more parallel arrays of electromechanical nozzles whose positions along their respective arrays are aligned with the positions of the electromechanical nozzles on another array instead of being laterally offset.

[0075] In an advantageous embodiment, the nozzle control unit 280 may further control the electro-valves dispensing fluid on a specific plant to openand close at a frequency between 30 and 100 Hz during the interval they are dispensing fluid to provide variable volume of hot fluid. The frequency is computed by the processing unit 230 in function of one or more of the above-described plant parameters.

[0076] Referring to Figure 1, the height control unit 270 is adapted to control the height of electromechanical nozzles from the ground 110 based on the height of the plant 114, 116 to be eradicated to reduce the distance between the nozzle spout 306 (Figure 3) and top of the plant below a predetermined threshold so as to limit heat loss as the fluid travels in the air.

[0077] The electromechanical nozzles of the first and second arrays 250, 252 comprise each the nozzle 300 illustrated in Figures 3 to 5. The nozzle comprises diametrically opposed fitting caps 302 fixed to a structure of the first and second arrays 250, 252, a nozzle body 304 and the nozzle spout 306. A nozzle inlet 310 is located inside the nozzle body 304. The distal end of the nozzle spout 306 comprises an elongated outlet surface 322 provided with nozzle outlets 320. The length of the elongated surface 322 substantially correspond to the pitch distance 264 between two adjacent nozzle arrays of the same array as shown in Figure 2.

[0078] With reference to Figure 5, the nozzle 300 further comprises a branched fluidic network 311 in fluid communication with the nozzle inlet310 and the nozzle outlets 320. The outlet surface 322 may comprise between 4 to 32 nozzle outlets 320 aligned along the elongated outlet surface, preferably between 12 and 24 outlets.

[0079] The branched fluidic network 311 and the nozzle outlets 320 are configured such that the fluid that may be delivered by each outlet nozzle has the same volumetric flow. In this respect, the branched fluidic network311 comprises at least three levels of flow divisions, preferably four levels flow divisions 312, 314, 316, 318. The nozzle inlet 310 comprises a calibratedhole upstream the branched fluidic network 311 to regulate the flow at the outlets.

[0080] The elongated outlet surface 322 of each nozzle has a length corresponding to the distance between two electromechanical nozzles and are arranged next to each other to form a quasi-continuous outlet surface with the nozzle elongated outlet surface 322 aligned along a direction perpendicular to the travel direction 202 of the agriculture vehicle when operating.

[0081] Unlike nozzles of regular agricultural spraying systems applying agrochemicals with a divergent angle so as to obtain small droplets of water for maximal absorption by the plants without water run-off on the plant leaves, the jets of hot fluid delivered by respective nozzle outlet 320 of the proposed nozzles 300 do not have divergent angles. The outlet surface 322 of each nozzle 300 has a width smaller than the nozzle-to-nozzle pitch. As a result of the non-divergence and the nozzle outlet geometry, the multiple jets of one nozzle do not overlap with the multiple jets of the next nozzle, and there are no holes in the applied fluid between two adjacent nozzles. If all the nozzles of an array are activated, this results in a continuous vertical curtain of hot fluid applied, touching the ground in a homogeneous manner.

[0082] With reference to Figure 6, the fluid delivery equipment also comprises a hot fluid preparation system 400 capable of maintaining the fluid at high temperature, higher than 90°C, typically around 98°C for water, while using a small number of elements. The hot fluid preparation system 400 comprises a fluid storage tank 410.

[0083] The fluid storage tank 410 is arranged to contain hot fluid and comprises an air compressor 412 mounted to pump air from outside into the fluid storage tank 410 to pressurize the hot fluid within the tank 410. The storage tank 410 further comprises a pressure sensor 416 to measure the pressure inside the tank 410 and in communication with the air compressorto drive said air compressor so as to maintain a constant pressure within the storage tank 410 independently of the fluid level in the tank.

[0084] This specific configuration ensures delivery of the hot fluid to the first and second arrays of electromechanical nozzles at working pressure adequate for correct electro-valve and nozzle operation (typically 1 to 3 bars above atmospheric pressure) instead of using a pressure pump at the output of the tank which renders the design and reliability of such pumps more difficult and expensive due to the hight temperature of the fluid.

[0085] The fluid storage tank 410 may contain a large quantity of hot fluid that can be either heated in the tank itself with a heat exchange system or heated previously into another system and transferred to the tank before usage. The fluid storage tank 410 is usually well isolated to reduce heat losses.

[0086] The fluid delivery equipment further comprises a hot fluid distribution system 420 to distribute hot fluid from the fluid storage tank 410 to inlet of the electro-valve 456 of respective electromechanical nozzles of one or more arrays array 250, 252, and a nozzle control unit arranged to control the electro-valves of respective electromechanical nozzles to deliver hot fluid on plants.

[0087] The fluid distribution system 420 comprises a closed circuit 430 and a recirculating pump 460 to recirculate the hot fluid in the closed circuit 430. This circuit comprises a heating element 434 arranged to heat the fluid circulating along a heating zone 432 of the closed circuit 430. A temperature sensor 438 is arranged to measure the temperature of the fluid flowing downstream the heating zone 432 to control the heating element 434 so as to maintain the fluid at a predetermined temperature.

[0088] In an embodiment, the heating element is in the form of an electric heater 434 arranged inside a portion of the closed circuit 430 through which the hot fluid is intended to flow.

[0089] The fluid delivery equipment further comprises another temperature sensor 436 arranged upstream the heating zone 434 to measure the temperature of the fluid dispensed by the fluid storage tank 410 so as to control the heating element 434 also according to said temperature.

[0090] The hot fluid distribution system 420 may also comprise a fluid buffer 440 mounted downstream the heating zone 432 and upstream a fluid delivery conduit 450 running along one or more arrays of respective electromechanical nozzles and in fluid communication with the electrovalves 456 of respective electromechanical nozzles of one or more arrays array. The fluid buffer 440 is adapted to store hot fluid and is in fluid communication with the fluid delivery conduit 450 through its inlet 452 in case of sudden fluid need.

[0091] The hot fluid may therefore go through a fluid delivery conduit 450 and leaves it through its outlet 454, then it goes to the circulation pump 460, whose function is not to increase the pressure of the liquid, but to create a return flow to the heating zone 434. The conduit 450 extends inside a structure supporting the electromechanical nozzles and is in fluid communication with the electro-valves 456 as illustrated in Figures 1 and 6.

[0092] The operating mode of the hot fluid preparation system 400 of Figure 6 is independent of the number of arrays of electromechanical nozzle and can therefore be used with a fluid delivery equipment comprising just one array or more than two arrays of electromechanical nozzles.List of reference signsCultivated field 100Ground surface 110Cultivated plant 112Small plant 114Big plant 116Fluid delivery equipment 200Travel direction 202Camera system 220Camera module 222Camera module field of view 224Processing unit 230Tracking unit 235First array 250 of electromechanical nozzlesSecond array 252 of electromechanical nozzlesSpot of hot fluid 260 of first array of nozzlesSpot of hot fluid 262 of second array of nozzlesPitch distance 264Offset distance 266Superposition of spots 268Height control unit 270Nozzle control unit 280Nozzle 300Fitting cap 302Nozzle body 304Nozzle spout 306Nozzle inlet 310Branched fluidic network 311First flow division 312Second flow division 314Third flow division 316Fourth flow division 318Nozzle outlets 320Outlets surface 322Hot fluid preparation system 400Fluid storage tank 410Air compressor 412Pressure sensor 416Fluid distribution system 420Closed circuit 430Heating zone 432Heating element 434 Temperature sensors 436, 438Fluid buffer 440Fluid delivery conduit 450Inlet 452Outlet 454 Electro-valves 456Recirculation pump 460

Claims

Claims1. A method for selectively applying hot fluid on an area of a cultivated field (100) using an agricultural vehicle including a fluid delivery equipment (200) comprising:- a fluid storage tank (410) for storing hot fluid,- N parallel arrays (250, 252) of electromechanical nozzles comprising each an electro-valve (456) and a nozzle (300), wherein the electromechanical nozzles of each array (250, 252) are spaced apart from each other along their respective array by a constant pitch distance (264) and wherein the positions of respective electromechanical nozzles along one array (250) are either aligned with the positions of respective electromechanical nozzles along another array (252), or offset from the positions of respective electromechanical nozzles along another array (252) by an offset distance (266) whose value preferably equals said pitch distance divided by N,- a hot fluid distribution system (420) to distribute hot fluid from the fluid storage tank (410) to the electro-valves (456) of the electromechanical nozzles of said N arrays (250, 252), the method comprising the steps of:- capturing images of the cultivated field (100) ahead of the fluid delivery equipment (200) while the agricultural vehicle is moving in the travel direction (202), wherein the images contain the ground (110) of the cultivated field (100), plants to be eradicated (114, 116) and cultivated plants (112);- processing said images to identify the position of each plant in the coordinate system of the fluid delivery equipment (200), and at least one plant parameter of each plant for determining a number of hot fluid applications, ranging from zero to N, to be applied on each plant to be eradicated based on said at least one plant parameter, and- continuously tracking the position of each plant in said coordinate system while the agricultural vehicle moves over the cultivated field (100) and timely selectively controlling the electro-valves (456) of said N arrays (250, 252) of electromechanical nozzles to apply said number of hot fluid applications on the plants to be eradicated, wherein each fluid application is applied by an electromechanical nozzle of a different array (250, 252) when the number of applications exceeds one.

2. The method of claim 1, wherein said at least one plant parameter is selected among plant species, plant size, plant height and distance of the plant to a cultivated plant (112).

3. The method of the preceding claim, wherein the determination of the number of hot fluid applications to be applied to a given identified plant to be removed is based on the distance between this plant and said cultivated plant (112) such that the number of hot fluid applications is respectively zero, one, or two if said distance is respectively smaller than a first threshold, is comprised between said first threshold and a second threshold larger than said first threshold, and is comprised between said second threshold and a third threshold larger than said second threshold.

4. The method of any preceding claim, wherein said number of hot fluid applications is also determined based on at least one environmental parameter selected among ambient air temperature, ambient air moisture, sun irradiance, soil temperature and soil moisture.

5. The method of any of the preceding claims, wherein N equals two, three and four respectively and said said offset distance (266) between two arrays equals respectively half, a third and a fourth of said pitch distance (264).

6. The method of any preceding claim, wherein the electromechanical nozzles of the arrays (250, 252) are controlled by the nozzle control unit (280)to select electromechanical nozzles whose lateral positions are the most suited to deliver hot fluid only on the plant to be eradicated and not on adjacent plants, the number of selected nozzles corresponding to the number of successive hot fluid applications determined for the plant.

7. The method of any preceding claim, wherein the electro-valves (456) of the electromechanical nozzles are further controlled to be opened and closed at a frequency between 30 and 100 Hz during the interval the electromechanical nozzles are dispensing fluid to provide a variable volume of hot fluid, wherein the frequency is chosen according to said at least one plant parameter.

8. The method of any preceding claim, wherein the height of electromechanical nozzles from the ground (110) is controlled by a height control unit (270) of the fluid delivery equipment (200) based on the height of the plant to be eradicated to reduce the distance between the nozzle spout (306) and the plant below a predetermined threshold so as to limit heat loss in the fluid.

9. The method of any preceding claim, wherein the hot fluid is water.

10. The method of any preceding claim, wherein the temperature of the hot fluid within fluid storage tank (410) is between 80°C and 100°C.

11. The method of claim 9 or 10, wherein the water contains at least one phase-change material (PCM) such as salt hydrates to heat the fluid circulating in the hot fluid distribution system (420).

12. The method according any preceding claim, wherein each nozzle (300) of the arrays (250, 252) comprises a nozzle inlet (310), an elongated outlet surface (322) having a plurality of nozzle outlets (320), and a branched fluidic network (311) in fluid communication with the nozzle inlet (310) and the nozzle outlets (320).T113. An agricultural vehicle for applying hot fluid on a cultivated field (100), including a fluid delivery equipment (200) comprising- at least one array (250, 252) of electromechanical nozzles comprising each a nozzle (300) and an electro-valve (456),- a fluid storage tank (410) for storing hot fluid,- a hot fluid distribution system (420) to distribute hot fluid from the fluid storage tank (410) to inlet of the electro-valves (456) of respective electromechanical nozzles of said at least one array (250, 252), and- a nozzle control unit (280) arranged to control the electro-valve of said at least one array (250, 252) of electromechanical nozzles to deliver hot fluid on plants, wherein said hot fluid distribution system (420) comprises a closed circuit (430) and a recirculating pump (460) to recirculate the hot fluid in the closed circuit (430) and wherein a heating element (434) is arranged to heat the fluid circulating along a heating zone (432) of the closed circuit (430) and a temperature sensor (438) arranged to measure the temperature of the fluid flowing downstream said heating zone (434) to control the heating element (434) so as to maintain the fluid at a predetermined temperature.

14. The agricultural vehicle of the preceding claim, further comprising another temperature sensor (436) arranged upstream said heating zone (434) to measure the temperature of the fluid dispensed by the fluid storage tank (410) so as to control the heating element (434) also according to said temperature.

15. The agricultural vehicle of claim 13 or 14, wherein said hot fluid distribution system (420) comprises a fluid buffer (440) mounted downstream said heating zone (432) and upstream the electro-valves of said at least one array (250, 252) of electromechanical nozzles.

16. The agricultural vehicle of any of claims 13 to 15, wherein the heating element is in the form of an electric heater (434) arranged inside a portionsaid closed circuit (430) through which the hot fluid is intended to flow.

17. The agricultural vehicle of any of claims 13 to 16, wherein the fluid storage tank (410) is arranged to contain hot fluid and comprises an air compressor (412) mounted to pump air from outside into the fluid storage tank (410) to pressurize the hot fluid within the tank (410), the storage tank (410) further comprising a pressure sensor (416) to measure the pressure inside the tank (410) and in communication with the air compressor to drive said air compressor so as to maintain a constant pressure within the storage tank (410) independently of the fluid level in the tank.

18. The agricultural vehicle of any of claims 13 to 17, wherein the fluid delivery equipment (200) further comprises:- at least a first and a second array (250, 252) of electromechanical nozzles comprising each an electro-valve (456) and a nozzle (300), wherein the electromechanical nozzles of both the first and second arrays (250, 252) are spaced apart from each other along their respective array by a constant pitch distance and wherein the positions of respective electromechanical nozzles along the first array (250) are offset from the positions of respective electromechanical nozzles along the second array (252) by an offset distance comprised between zero and half said constant pitch distance (264),- a camera system (220) comprising one or more camera modules (222) arranged to capture images of the cultivated field (100) ahead of the fluid delivery equipment (200) in the travel direction (202) of the agricultural vehicle, wherein the images contain the ground (110) of the cultivated field (110), plants to eradicated (114, 116) and cultivated plants (112);- a processing unit (230) configured to run an image recognition software to identify and to classify the plants (114, 116) on the captured images according to their sizes and species, and to generate a mapping of said plants (114, 116) on the coordinate system of the fluid delivery equipment (200) - a tracking unit (235) for continuously tracking the position of each plant on said mapping, andwherein the nozzle control unit (280) is arranged in communication with the processing unit (230) and the tracking unit (235) to timely selectively control the electro-valve (456) of said first and second arrays of electromechanical nozzles to apply hot fluid on the plants to be eradicated.

19. The agricultural vehicle of any of claims 13 to 18, wherein each nozzle (300) of said at least one array (250, 252) of electromechanical nozzles comprises a nozzle inlet (310) in fluid communication with the corresponding electro-valve (456), an elongated outlet surface (322) provided with an array of nozzle outlets (320) with preferably 4 to 32 outlets distributed linearly along the elongated outlet surface and a branched fluidic network (311) in fluid communication with the nozzle inlet (310) and the nozzle outlets (320).

20. The agricultural vehicle of the preceding claim, wherein the branched fluidic network (311) is configured such that the hot fluid flowing out of the nozzles outlets is not divergent.

21. The agricultural vehicle of the preceding claim, wherein the branched fluidic network (311) and the nozzle outlets (320) are configured such that the fluid that may be delivered by each nozzle outlet has the same volumetric flow, the fluid pressure at the nozzle outlets (320) preferably ranging from zero to three bars.

22. The agricultural vehicle of any claims 19 to 21, wherein said branched fluidic network (311) comprises multiple levels of flow divisions (312, 314, 316, 318).

23. The agricultural vehicle of any of claims 19 to 22, wherein the nozzle inlet (310) comprises a calibrated hole upstream the branched fluidic network (311) to regulate the flow.

24. The agricultural vehicle of any of claims 19 to 23, wherein said elongated outlet surface (322) of each nozzle has a length corresponding tothe distance between two electromechanical nozzles (264) and are arranged next to each other to form a quasi-continuous outlet surface with the nozzle elongated outlet surface (322) aligned along a direction perpendicular to the travel direction (202) of the agriculture vehicle when operating.

25. A nozzle (300) for an agricultural vehicle, comprising a nozzle inlet (310), an elongated outlet surface (322) provided with nozzle outlets (320) and a branched fluidic network (311) in fluid communication with the nozzle inlet (310) and the nozzle outlets (322).

26. The nozzle (300) of the preceding claim, wherein the number of the nozzle outlets (320) is selected between 4 and 20.

27. The nozzle (300) of claim 25 or 26, wherein the nozzle outlets (320) are aligned along the elongated outlet surface (322).

28. The nozzle (300) of any of claims 25 to 27, wherein the branched fluidic network (311) and the nozzle outlets (320) are configured such that the fluid that may be delivered by each outlet nozzle has the same volumetric flow.

29. The nozzle (300) of any of claims 25 to 28, wherein the branched fluidic network (311) comprises at least three levels of flow divisions (312, 314, 316, 318).

30. The nozzle (300) of any of claims 25 to 29, wherein the nozzle inlet(310) comprises a calibrated hole upstream the branched fluidic network(311) to regulate the flow.

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