Controlling spot spraying of agrochemicals

Abstract

A method of operating a spot spray control system (100, Fig. 1) for spraying agrochemicals using spray assembly (200, Fig. 2A) having imaging system 202 and spray bar 112 with individually controllabl

Description

Technical Field

[001] The present invention relates to control of spray apparatus for spot spraying of plants with agrochemicals. Background

[002] Agrochemicals, whether to promote growth (e.g. fertilisers), inhibit growth (e.g. herbicides) or prevent diseases or plagues (fungicides, insecticides, etc.), are typically applied to plants in liquid form using spraying. The agrochemicals are sprayed through nozzles which may be mounted on a spray bar. The spray bar may be mounted on a vehicle (e.g. a tractor or robot) or mounted on a device that is towed by a vehicle. Continuous spraying involves spraying agrochemicals everywhere and the nozzles are in continuous operation. In contrast, spot spraying applies droplets of liquids on specific and predetermined locations through the use of valves (e.g. electromechanically controlled valves) which can switch the flow of the agrochemical on and off rapidly.

[003] Use of continuous spraying is often inefficient since the agrochemicals are sprayed where they are not needed (e.g. onto bare soil) and as well as increasing costs, this increases chemical residues in the soils which can have various impacts including damaging biodiversity and an increased likelihood of phytotoxicity for the sprayed crop plants leading to yield losses. Spot spraying can significantly reduce the amount of agrochemical that is applied. This increases efficiency (since the agrochemical is only applied where it is needed), reduces the environmental impact (e.g. less chemical residues in soils and water, reduced carbon emissions due to reduced fabrication and transport of liquid agrochemicals), reduces use of water, and improves yield. Summary

[004] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[005] Described herein is a method of operation of a spot spray control system for spraying agrochemicals on target objects using a moveable spray assembly. The method comprises receiving a three-dimensional map of a first spray window generated by an imaging system, the three-dimensional map defining positions of one or more target objects and the one or more target objects comprising portions of target objects at different distances from the spray bar. The portions of the one or more target objects are divided into a plurality of groups as a function of their distance from the spray bar, each group defining a target area. A pattern of spot sprays is determined for each target area, such that for a target area, a cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern for the target area satisfies pre-defined target dose parameters.

[006] A first aspect provides a method of operation of a spot spray control system for spraying agrochemicals on target objects using a moveable spray assembly, the spray assembly comprising an imaging system and a spray bar perpendicular to a travel direction of the spray assembly, wherein the spray bar comprises an array of nozzles positioned linearly along the spray bar, each nozzle configured to produce a divergent jet with a defined non-homogeneous two-dimensional liquid spatial distribution and wherein an opening instant and opening duration of each nozzle is individually controllable, the method comprising: receiving a three-dimensional map of a first spray window generated by the imaging system, the three-dimensional map defining positions of one or more target objects, the one or more target objects comprising portions of target objects at different distances from the spray bar; dividing the portions of the one or more target objects into a plurality of groups as a function of their distance from the spray bar, each group defining a target area; determining a pattern of spot sprays for each target area, such that for a target area, a cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern for the target area satisfies pre-defined target dose parameters, wherein each spot spray in the pattern is defined by the distance of the target area from the spray bar, the non-homogeneous two-dimensional liquid spatial distribution of a nozzle in the array of nozzles and a forward speed of the spray assembly; generating control signals corresponding to the defined patterns, wherein the control signals define, for each spot spray, an opening instant and opening duration of a nozzle in the array of nozzles; and outputting the control signals to the spray assembly.

[007] The pre-defined target dose parameters may define a minimum dose per unit area and / or a maximum dose per unit area.

[008] The pattern of spot sprays may be further defined to minimize a dose falling outside the target area.

[009] Determining a pattern of spot sprays for each target area may comprise: sequentially selecting each target area according to a distance of a leading edge of the target area from a front edge of the field of view of the imaging system; and determining, for the selected target area, a pattern of spot sprays for the target area, such that the cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern satisfies the pre-defined target dose parameters.

[0010] The method may further comprise repeating the method for a second spray window.

[0011] If the first target area in the second spray window has a same distance from the spray bar as a last target area in the first spray window, the method may further comprise determining the pattern of spot sprays for the first target area in the second spray window comprises continuing the pattern of spot sprays for the last target area in the first spray window to cover the first target area in the second spray window such that the cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern satisfies the predefined target dose parameters.

[0012] The pattern of spot sprays for a selected target area within a spray window may be determined independently of the pattern of spot sprays for any previously selected target area within a same spray window. Alternatively, the pattern of spot sprays for a selected target area within a spray window may be determined taking into consideration any overlap of the pattern of spot sprays for a previously selected adjacent target area within a same spray window with the selected target area.

[0013] Determining a pattern of spot sprays for each target area, such that for a target area, a cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern for the target area satisfies pre-defined target dose parameters may comprise: (i) defining a position of a first spot spray based on a position of a leading edge of a target area; (ii) defining an initial position in terms of a transverse offset and a longitudinal offset relative to the first spot spray, of at least one new adjacent spot spray such that the combined dose of the first and new spot sprays forms a continuous spray zone that covers a portion of the target area, wherein each of the first and new spot sprays is defined by a non-homogeneous two-dimensional liquid spatial distribution and the transverse offset is a multiple of an effective spacing of the nozzles in the array of nozzles; (iii) determining a two-dimensional dose map resulting from the first and new spot sprays; and (iv) in response to determining, from the two-dimensional dose map, that pre-defined dose criteria are not met, adjusting the offsets of the at least one new adjacent spot spray to optimise a received dose.

[0014] The method may further comprise, in response to determining, from the two-dimensional dose map, that the target area is not fully covered by the spray zone, repeating steps (ii)-(iv) until the target object is fully covered.

[0015] The at least one new adjacent spot spray may comprise three new adjacent spot sprays; and wherein adjusting the offsets of the at least one new adjacent spot spray to optimise a received dose comprises: adjusting the offsets of the three new adjacent spot sprays to optimise a received dose within a quadrilateral defined by the first spot spray and the three new adjacent spot sprays; and wherein the method further comprises: in response to determining that the target area is not fully covered, placing additional spot sprays at the same offsets to further cover the target area.

[0016] The three-dimensional map may define positions of one or more avoid objects and wherein determining a pattern of spot sprays for each target area, such that for a target area, a cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern for the target area satisfies pre-defined target dose parameters comprises: placing a first spot spray as close as possible to a proximate avoid object without exceeding a pre-defined maximum, non-zero, dose on the proximate avoid object; placing one or more additional spot sprays as close as possible to the proximate avoid object to form a continuous spray region of at least the minimum dose over a part of the target area whilst not exceeding the maximum, non-zero, dose on the proximate avoid object; and if the pre-defined target dose parameters for the target area are not satisfied, placing one or more further spot sprays.

[0017] The non-homogeneous two-dimensional liquid spatial distribution of a nozzle may be defined in a look-up table.

[0018] The non-homogeneous two-dimensional liquid spatial distribution of a nozzle as a function of the distance from nozzle to target, the forward speed and the nozzle opening duration, is defined in a look-up table.

[0019] The non-homogenous two-dimensional liquid spatial distribution of a nozzle may be defined using a Gaussian or normal distribution.

[0020] A second aspect provides a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method of any of the preceding claims.

[0021] A third aspect provides a computer-readable medium having stored thereon the computer program of the second aspect.

[0022] A fourth aspect provides a spot spray control system for spraying agrochemicals on target objects using a moveable spray assembly, the spray assembly comprising an imaging system and a spray bar perpendicular to a travel direction of the spray assembly, wherein the spray bar comprises an array of nozzles positioned linearly along the spray bar, each nozzle configured to produce a divergent jet with a defined non-homogeneous two-dimensional liquid spatial distribution and wherein an opening instant and opening duration of each nozzle is individually controllable, and the spot spray control system comprising: a processor; one or more interfaces configured to receive target object data and output control signals to the spray assembly; and memory arranged to store a computer program which, when executed by the processor, causes the control system to: receive a three-dimensional map of a first spray window generated by the imaging system, the three-dimensional map defining positions of one or more target objects, the one or more target objects comprising portions of target objects at different distances from the spray bar; divide the portions of the one or more target objects into a plurality of groups as a function of their distance from the spray bar, each group defining a target area; determine a pattern of spot sprays for each target area, such that for a target area, a cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern for the target area satisfies pre-defined target dose parameters, wherein each spot spray in the pattern is defined by the distance of the target area from the spray bar, the non-homogeneous two-dimensional liquid spatial distribution of a nozzle in the array of nozzles and a forward speed of the spray assembly; generate control signals corresponding to the defined patterns, wherein the control signals define, for each spot spray, an opening instant and opening duration of a nozzle in the array of nozzles; and output the control signals to the spray assembly.

[0023] The pre-defined target dose parameters may define a minimum dose per unit area and / or a maximum dose per unit area.

[0024] The pattern of spot sprays may be further defined to minimize a dose falling outside the target area.

[0025] The computer program, when executed by the processor, may cause the control system to determine a pattern of spot sprays for each target area by: sequentially selecting each target area according to a distance of a leading edge of the target area from a front edge of the field of view of the imaging system; and determining, for the selected target area, a pattern of spot sprays for the target area, such that the cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern satisfies the pre-defined target dose parameters.

[0026] The computer program, when executed by the processor, may cause the control system to determine a pattern of spot sprays for each target area by additionally: repeating the method for a second spray window, wherein, if the first target area in the second spray window has a same distance from the spray bar as a last target area in the first spray window, determining the pattern of spot sprays for the first target area in the second spray window comprises continuing the pattern of spot sprays for the last target area in the first spray window to cover the first target area in the second spray window such that the cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern satisfies the predefined target dose parameters.

[0027] The pattern of spot sprays for a selected target area within a spray window may be determined independently of the pattern of spot sprays for any previously selected target area within a same spray window. Alternatively, the pattern of spot sprays for a selected target area within a spray window may be determined taking into consideration any overlap of the pattern of spot sprays for a previously selected adjacent target area within a same spray window with the selected target area.

[0028] The methods described herein may be performed by software in machine readable form on a tangible storage medium e.g. in the form of a computer program comprising computer program code means adapted to perform all the steps of any of the methods described herein when the program is run on a computer and where the computer program may be embodied on a computer readable medium. Examples of tangible (or non-transitory) storage media include disks, thumb drives, memory cards etc. and do not include propagated signals. The software can be suitable for execution on a parallel processor or a serial processor such that the method steps may be carried out in any suitable order, or simultaneously.

[0029] This acknowledges that firmware and software can be valuable, separately tradable commodities. It is intended to encompass software, which runs on or controls “dumb” or standard hardware, to carry out the desired functions. It is also intended to encompass software which “describes” or defines the configuration of hardware, such as HDL (hardware description language) software, as is used for designing silicon chips, or for configuring universal programmable chips, to carry out desired functions.

[0030] The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known methods of controlling spraying of agrochemicals.

[0031] The preferred features may be combined as appropriate, as would be apparent to a skilled person, and may be combined with any of the aspects of the invention. Brief Description of the Drawings

[0032] Embodiments of the invention will be described, byway of example, with reference to the following drawings, in which:

[0033] Figure 1 is a schematic diagram of a first example spot spraying system;

[0034] Figure 2A is a schematic diagram of a second example spot spraying system;

[0035] Figure 2B is a schematic diagram showing a part of Figure 2A in more detail;

[0036] Figure 3 is a schematic diagram of a dual spray bar arrangement;

[0037] Figure 4 shows two different examples of one dimensional (1D) spot dose profiles;

[0038] Figure 5 shows an example shape of a spot spray;

[0039] Figure 6 shows an example representation of a 2D liquid spatial distribution of a nozzle in the form of a look-up table;

[0040] Figure 7 shows two examples of a resultant 2D liquid spatial distribution for a spot spray as a result of different opening durations and a forward movement;

[0041] Figures 8A-8C show three spot dose profiles for different combinations of distance and opening duration;

[0042] Figure 9 shows a first example method of operation of spot spray control system, such as the spot spray control system 102 shown in Figure 1;

[0043] Figures 10A-10F and 11A-11B show example implementations of the method of Figure 9;

[0044] Figure 12 shows a first example implementation of one of the steps in the method of Figure 9;

[0045] Figure 13 is a graphical representation that shows how adjusting the offsets can be used to optimise the received dose across the target object;

[0046] Figure 14 shows an example implementation of the method of Figure 12;

[0047] Figure 15 shows a second example implementation of one of the steps in the method of Figure 9;

[0048] Figures 16-19 show example implementations of the method of Figure 15;

[0049] Figure 20 shows a third example implementation of one of the steps in the method of Figure 9; and

[0050] Figure 21 illustrates various components of an example spot spray control system in the form of a computing-based device.

[0051] Common reference numerals are used throughout the figures to indicate similar features. Detailed Description

[0052] Embodiments of the present invention are described below by way of example only. These examples represent the best ways of putting the invention into practice that are currently known to the Applicant although they are not the only ways in which this could be achieved. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

[0053] As described above, spot spraying of agrochemicals can be significantly more efficient than continuous spraying. To be effective, however, spot spraying requires an efficient control system that can translate the target spray area into a set of control signals for the valves associated with the nozzles. Errors in this translation result in a mismatch between the target spray area and the actual spray area and this can reduce efficiency (e.g. where the actual spray area is larger than the target spray area) and effectiveness (e.g. by not spraying parts of the target spray area). In many applications, the target spray area is determined in real-time (e.g. using a camera system that scans an area of a field, or other cultivated surface, ahead of the spray bar passing over the area) and so the available time to perform the translation is very short (e.g. less than 500ms).

[0054] An important spray parameter in the application of agrochemicals is the control of the dose per unit area. The highest level of spatial dose homogeneity must be guaranteed. Indeed, if the dose is not sufficient, the efficiency of the chemistry is reduced and may compromise the operation. If too high, the dose can exceed legal limits and be harmful for the environment, and / or cause harm to the crop plants through phytotoxicity.

[0055] Known control methods for spraying systems for agrochemicals rely upon each nozzle providing a homogeneous application within the spray pattern shape of the nozzle. In the case of a continuous spraying done with an array of nozzles mounted orthogonally to the displacement direction of the application machine, as there is no need to avoid some part of the ground, a good dose homogeneity is obtained by using nozzles with homogeneous lateral distribution profiles, having a relatively large jet divergence angle in the lateral direction (common values are 80 to 110 degrees) , and separated laterally with a distance in general smaller than their vertical distance to the target (where the target, or target object, is a plant that is to be sprayed with the agrochemical), so that the jets of droplets produced by adjacent nozzles overlap largely together and combine into a dense lateral cloud of droplets distributed homogeneously when they hit the ground.

[0056] For the case of a spot spray application, a homogeneous application of droplets is much harder to obtain for the following reasons. First, as the area of a single spot spray must be as small as possible to be as spatially selective as possible (e.g. so that agrochemical is applied where it is needed and not on other neighbouring plants), the jet divergence angle of a nozzle must be much smaller than fora continuous spray (typically 15 to 25 degrees), which does not help in equalizing the dose over a large area. Second, the distance from nozzle to target must be as short as possible to guarantee the highest spot placement accuracy. Therefore, overlapping adjacent jets when both nozzle to target distance and jet divergence angle are small is a challenging task, as the resulting required nozzle to nozzle lateral distance becomes very small. Such a high density of nozzles leads to the need to use low flow nozzles to avoid applying too much product. Low flow nozzles are hard to fabricate and tend to get clogged easily. Third, as the movement of the application machine can be fast (e.g. several meters per second), the opening duration of the electromechanical valves associated with the nozzles must be very short to produce short spots in the forward direction. This sets challenges in the design of the valve. Fourth, the nozzle to target distance can vary during the application due to movement of the spray bar from ground, or ground irregular surface, or difference of heights between targets to be sprayed (e.g. where the plant height varies). Such a varying distance from nozzle to target renders the control of adjacent overlap ratio difficult. When the overlap ratio is not well controlled, it is difficult to base upon a specific nozzle lateral dose profile to get homogeneity through overlapping, as this overlapping can rapidly change from 2 jets overlapping to 3 jets overlapping, for instance, when the vertical distance increases.

[0057] All these elements render the application of a homogeneous dose difficult on spot spraying, both for single spot sprays (i.e. when a single nozzle is activated) or for larger spot sprays resulting in the cumulative action of several neighboring nozzles. Nevertheless, dose control remains a significant concern in spot spray devices. Therefore, there is a strong need to develop methods that enable control of the dose in spot spray equipment characterized by dense nozzle arrays with small jet divergence angles and small nozzle to target distances (typically 20 to 30 cm).

[0058] Described herein are improved methods of controlling spot spraying of agrochemicals that take into account the difference of heights within a single target to be sprayed (e.g. where a plant has some leaves which are further from the ground and others that are closer to the ground) and between targets to be sprayed (e.g. where the plant height varies, and / or the ground surface is not flat and the plants to be sprayed are at different vertical distances from the spray bar). The methods described herein also take into account the non-homogeneity of the two-dimensional (2D) liquid spatial distribution of a nozzle. An imaging system is used to map targets within its field of view (FOV) to a three-dimensional (3D) coordinate system and then to divide the targets, or parts thereof, within the FOV into a plurality of groups as a function of their distance (e.g. vertical distance) from the spray bar (or alternatively as a function of their vertical distance from a reference ground plane). Each group defines one or more target areas (or geometries) at a particular distance from the spray bar or within a particular distance range. A target area therefore corresponds to one or more targets and / or parts of one or more targets at a particular distance or within a particular distance range, where a target (or target object) is a plant that is to be sprayed with the agrochemical. Each target area is then considered in turn and using the distance from the spray bar of the target area, the 2D non-homogeneous liquid spatial distribution of a nozzle and the forward speed of the spray bar, a sequence of opening instants and durations fora plurality of the nozzles is determined so as to cover the target area with a plurality of spot sprays such that the cumulative 2D liquid spatial distribution of the spot sprays satisfies pre-defined target dose parameters such as a minimum, maximum or average required dose. Control signals are generated for an array of nozzles in a spray assembly based on the determined sequences of opening instants and durations for each of the target areas, taking also into consideration the forward horizontal speed of the spray assembly.

[0059] The spot sprays generated using the methods described herein may, for example, have a width (along their long axis) of between 2cm and 10cm, although it will be appreciated that this will be dependent upon the parameters of the system and the spot sprays may be smaller or larger than this.

[0060] The pre-defined target dose parameter may specify that the cumulative 2D liquid spatial distribution of the spot sprays must minimize the percentage of the target area that does not receive a pre-defined minimum dose per unit area. The control algorithm that is used to determine the sequence of opening instants and durations may additionally minimize the dose falling outside the target area and / or ensure that the cumulative 2D liquid spatial distribution of the spot sprays does not exceed a pre-defined maximum dose per unit area anywhere within target area.

[0061] The agrochemicals sprayed using the methods described herein may have any of the purposes found in plant protection or plant fertilization and so the plant that is the detected target object, or which may form part of the detected target object where the target object is a cluster of plants, may be a crop or a weed.

[0062] Examples of agrochemicals that may be sprayed using the methods described herein include fertilizers, herbicides, fungicides, insecticides or another other agrochemical that promotes or inhibits growth or prevents diseases or plagues. Further examples of agrochemicals that may be sprayed using the methods described herein include other liquids such as hot water or hot oil for thermal weeding, or any other liquid used for weeding or crop care operations.

[0063] The methods described herein may be implemented in real-time as the spray assembly traverses the field and sprays the detected target objects. As described in more detail below, the methods may be implemented within each spray window where the size of the spray window is defined based on the width of the spray assembly, the characteristics of the imaging system used to scan the field, the distance separating the field portion observed by the imaging system from the spray system, and the forward speed of the spray assembly.

[0064] By using the methods described herein, the efficiency and adaptability of the spot spraying is increased. By precise control of the agrochemicals delivered to the target object, the overall amount of agrochemicals sprayed can be reduced, thereby improving efficiency and effectiveness and reducing the environmental impact of both the use of the agrochemicals and their fabrication and transport. As described below, the method can adapt to changes in the spray assembly and the topology of the surface being sprayed in real-time and in particular the differing heights within and between target objects (e.g. in the time between detection of a target object and a nozzle passing over that target object), rather than requiring precise control of the spray height (i.e. the separation of nozzle and the target object).

[0065] Figure 1 shows a schematic diagram of a first example spot spraying system 100. The system 100 comprises a spot spray control system 102, a spray assembly 104 and an imaging system 106. The spot spraying system 100 may also comprise a distance detection unit 108 and this may be part of the imaging system 106, as shown in Figure 1. It will be appreciated that the spot spraying system 100 may comprise other elements not shown in Figure 1, such as one or more sensors (e.g. an accelerometer, a GPS receiver, a sensor, etc.).

[0066] The spray assembly 104 comprises a plurality of nozzles 110 mounted on a spray bar 112. The nozzles 110 are mounted at a regular spacing, s, along the spray bar 112. Each nozzle 110 has an associated electromechanical valve 114 that is positioned between the nozzle 110 and the spray bar 112. These electromechanical valves 114 can be switched on and off rapidly and precisely to control the flow of fluid from each nozzle 110 and generate each spot spray. A spot spray refers to the fluid output from a nozzle 110 in a single valve opening (i.e. between the valve opening and subsequently closing again). The time that the valve 114 is open and generating a single spot spray may be referred to as a spot duration or opening duration, t, and may be in the region of 3-20 ms. The spray bar 112 is in fluid communication with a tank and pressure system 116 via an optional inlet electromechanical valve 118. The tank and pressure system 116 comprises a tank for holding the agrochemical that is to be sprayed and a pressure system that generates and controls the pressure, p, at which the agrochemical is supplied from the tank to the spray bar 112 and ultimately to the nozzles 110. The volume of fluid output in a single spot spray is a function of the opening duration, the nozzle design (e.g. nozzle diameter) and the pressure and the area that the single spot spray covers (and hence the dose per unit area) is also dependent upon the distance between the nozzle and the surface (e.g. the ground). The inlet valve 118 enables the tank and pressure system 116 to be isolated from the spray bar 112, e.g. for maintenance purposes.

[0067] It will be appreciated that the spray assembly 104 may differ from that shown in Figure 1. For example, the valves 114 may be integrated into the spray bar 112, there may be more than one spray bar 112 and / or the inlet valve 118 may be omitted.

[0068] The imaging system 106 scans a portion of a field ahead of the spray bar 112 passing over the area and identifies target objects for spraying. This portion of the field that is scanned at any one time may be referred to as the spray window and its size is dependent on the width of the imaging system and spray system, on the distance separating the portion of the field observed by the imaging system and the spray system, and the forward speed of the spray assembly 104. The scanning may be performed continuously or periodically (e.g. every 100 ms). Where the scanning is performed periodically, the resulting spray windows may overlap (in the direction of the forward motion of the spray assembly) or be contiguous depending upon the time between scanning operations. The scanning operation is performed sufficiently frequently to avoid gaps between the spray windows. As described above, depending upon the type of agrochemical being sprayed, the target object may be a desired plant (i.e. a crop) or an undesired plant (i.e. a weed). The imaging system 106 may comprise one or more cameras and / or other sensors and a processing system arranged to process the data captured by the cameras and / or other sensors and output data defining a target object to be sprayed.

[0069] The imaging system 106 (e.g. the distance detection unit 108 within the imaging system 106) additionally, determines, for a fine grid of points over the spray window (e.g. each point of the ground), the distance that will be between the spray bar 112 and the target object at the point that the spray bar is directly over the target object. For many applications, the agrochemical is sprayed, by the nozzles 110, substantially vertically downwards and the distance determined by the imaging system 106 is a vertical height. In other spraying orientations (e.g. spraying a substantially vertical surface), the imaging system 106 still determines a distance between the spray bar 112 and the target object but this may, for example, be in a vertical plane. Any suitable technology may be used to perform distance detection (e.g. height detection) and in an example, the imaging system 106 may comprise 3D depth sensors or distance range sensors.

[0070] The spot spray control system 102 generates control signals for the valves 114 associated with the nozzles 110 in the spray assembly 104 based on input received from the imaging system 106. The spot spray control system 102 performs the improved methods of controlling spot spraying of agrochemicals described herein and these are described in more detail below.

[0071] Whilst the imaging system 106 and spot spray control system 102 are shown as separate elements in Figure 1, it will be appreciated that both of them may share common components (e.g. processing capabilities) or they may be combined.

[0072] Figure 2A shows a schematic diagram of a second example spot spraying system 200. The system 200, like that shown in Figure 1, comprises a spot spray control system, a spray assembly and an imaging system, although only some elements of these are visible in Figure 2A. In particular, Figure 2A shows the nozzles 110 and spray bar 112 as well as a camera 202 that is part of the imaging system 106. The tank and pressure system, the spot spray control system and other parts of the imaging system may be located within the body 204 of the spot spraying system 200. In this example, the spot spraying system 200 is towed behind a vehicle 206 (e.g. a tractor) and the direction of travel of the vehicle, when moving forwards, is marked by an arrow 208. As shown in Figure 2A, the imaging system scans a portion of a field 210 ahead of (i.e. before) the spray bar 112 passing over the area, i.e. the area being sprayed 212 is behind the area being scanned 210. The area being scanned 210 may be referred to as the field of view of the camera 202. As the distance between the scanned portion of the field 210 and the area being sprayed 212 is fixed, the time delay between the scanning of the field and the spray bar passing over the area can be calculated if the forward speed of the vehicle 206 is known. This is taken into consideration when generating control signals for the mechanical valves 114 in order to spatially synchronize the spot sprays and the target objects. The scanned portion of the field 210 is the spray window and whilst not visible in Figure 2A, the spray window has a width that corresponds to the width of the spray bar 112, this width requires generally several cameras 202 to be observed in its totality (although only one camera 202 is visible in Figure 2A).

[0073] Figure 2B is a schematic diagram showing a part of Figure 2A in more detail. In the perspective view of Figure 2B, the undulating nature of the ground, along with the varying distances of the target objects 220 from the spray bar 112 can be seen. The spray bar 112 is positioned substantially parallel to the ground (which may be a field or other cultivated surface). As shown in Figure 2B, some target objects may have one portion 222 that is closer to the spray bar 112 than another portion 224 of the same target object.

[0074] The spray assemblies shown in the systems 100, 200 in Figures 1,2A and 2B each comprise a single spray bar 112 with nozzles 110 mounted at a regular spacing, s, along the spray bar 112. In some example systems, the spray assemblies may comprise a plurality of spray bars with the nozzles on different spray bars offset from each other. In the example shown in Figure 3, each of the spray bars 302, 304 has nozzles mounted at a regular spacing, s, but the nozzles are offset between the spray bars giving an effective nozzle spacing of the overall spray assembly of s-s / 2. The effective nozzle spacing may be further reduced by having more than two spray bars, e.g. s / 3 for three spray bars, s / 4 for four spray bars, etc. The spray bars are oriented perpendicular to the direction of travel of the system so that where there are a plurality of spray bars in a spray assembly, these are spaced from each other in the direction of travel which is indicated by arrow 308 in Figure 3. The control methods described herein may be used with any arrangement of spray bars and nozzles. Of course, when valve control signals are directed to several bars in parallel, the control signals of the second or following bars must be delayed accordingly with the forward speed of the bars so that the spray spots of all bars are disposed on a same lateral line on the ground.

[0075] The static 2D liquid spatial distribution of a nozzle may be mathematically defined, e.g. in terms of parameters that define one or more equations, such as a Gaussian or normal distribution, that correspond to the distribution in 2D. Figure 4 shows two different examples of one dimensional (1D) spot dose profiles 402, 404. These 1D profiles 402, 404 may represent the dose profile taken along a line through an elliptical spot spray 502 as shown in Figure 5, e.g. along the line X-X’ or the line Y-Y’. In other examples, the static 2D liquid spatial distribution of a nozzle that is input to the method may be input in the form of a pre-calculated look-up table. For example, the look-up table may sub-divide the 2D spatial distribution into a 2D grid of cells and specify the dose received within each cell, as shown in the example 602 in Figure 6. As well as showing an example look-up table 602, Figure 6 also shows the equivalent 1D distributions 604, 606 along two perpendicular lines passing through the centre of the spot spray (e.g. along the equivalent of lines X-X’ and Y-Y’ shown in Figure 5). In some examples, the look-up table (or a set of look-up tables) may additionally or instead define 2D liquid spatial distributions for various combinations of distance, forward speed and nozzle opening duration.

[0076] The non-homogeneous 2D liquid spatial distribution shown in Figures 4-6 assumes that the nozzle is static and is dependent upon the nozzle design; however, as the spray assembly is moving, the resultant 2D liquid spatial distribution for any spot spray is a modified version of the static 2D liquid spatial distribution as a result of the motion during the period of time that the valve associated with the nozzle is open. As noted above, the opening duration for a valve may be in the range of 3-20 ms and the forward speed of the spray assembly may be around 2 m / s, resulting in the nozzle moving by around 1-4 cm during the time that the valve is open. Figure 7 shows two examples of a resultant 2D liquid spatial distribution 702, 704 for a spot spray as a result of different opening durations for a given forward speed of the nozzle. In the first example resultant 2D liquid spatial distribution 702, the opening duration is 5 ms and in the second example resultant 2D liquid spatial distribution 704, the opening duration is 15 ms. The arrow 706 shows the direction of motion of the spray assembly and both the increased dose and increased spreading as a consequence of the increased opening duration are clearly visible in the second example.

[0077] When the spray assembly is moving in a direction perpendicular to the spray bar (e.g. forwards) the speed of each nozzle is the same; however, if the motion of the spray assembly includes some rotation (e.g. because a corner is being turned), the speed of the nozzles will differ across a spray bar. Consequently, even if the same static 2D liquid spatial distribution is used for each nozzle, the resultant 2D liquid spatial distribution may differ between nozzles.

[0078] The improved methods of controlling spot spraying of agrochemicals described herein take into account the difference of heights within a single target to be sprayed (e.g. where a plant has some leaves which are further from the ground and others that are closer to the ground) and between targets to be sprayed (e.g. where the plant height varies). The static 2D liquid spatial distribution that is used to determine the cumulative 2D liquid spatial distribution of the spot sprays is therefore dependent upon the detected distance from the spray bar of the target area. This can be described with reference to Figures 8A and 8B.

[0079] Figure 8A shows an example 1D spot dose profile 802 for a first distance between the spray bar and the target area. This 1D profile 802 represents the dose profile taken along a line 804 through an elliptical spot spray 806. Also shown in Figure 8A is the line 808 which corresponds to the pre-defined minimum dose and the corresponding portion 810 of the spot spray that exceeds the pre-defined minimum dose (shown as the shaded ellipse in Figure 8A).

[0080] Figure 8B shows an example 1D spot dose profile 812 for a second distance between the spray bar and the target area, where the second distance is larger than the first distance that is reflected in Figure 8A. An increased distance results in a larger (i.e. upscaled) spot spray but in a lower dose per unit area, as the sprayed volume is unchanged but is spread over a wider area. As shown in Figure 8B, the width of the profile 812 (and hence the width of the elliptical spot spray 816) is larger because the spot spray has traveled further, and spread more, before it reaches the target area. As the overall dose (i.e. the area under the profile 812) in Figure 8B is the same as the dose in Figure 8A, the peak is lower and in the example shown, none of the elliptical spot spray 816 exceeds the pre-defined minimum dose.

[0081] Figure 8C shows an example 1D spot dose profile 822 for the second distance between the spray bar and the target area but where the opening duration of the nozzle is double that shown in Figure 8B. As described above with reference to Figure 7, as the spray assembly is moving during the period of time that the valve associated with the nozzle is open, there is spreading of the 2D liquid spatial distribution in the direction of travel (which is indicated by the arrow 824). This spreading is approximated in Figure 8C by the two offset ellipses 826, each of which is the same size as the ellipse 816 in Figure 8B (because the distance between the spray bar and the target area is the same). As a consequence of the longer opening duration of the nozzle, the overall dose is doubled and so the area under the profile 822 is double that under the profile 812 in Figure 8B. The peak in Figure 8C is double that in Figure 8C and there is a large portion of the spray area 828 which exceeds the predefined minimum dose.

[0082] As the spreading of the static 2D liquid spatial distribution is dependent upon the translational speed (e.g. forward speed) of the spray assembly, in some examples, the opening duration of the nozzles may be adjusted to compensate for changes in speed (e.g. as determined from the motion data that is input to the method). However, as changing the opening duration modifies the dose, even where this is used, the individual spray spots may have different maximum applied doses. This means that the combined dose of the spot sprays and their arrangement, will vary depending upon the local nozzle speed.

[0083] Figure 9 shows a first example method of operation of spot spray control system, such as the spot spray control system 102 shown in Figure 1. As shown in Figure 9, the method receives target object data as an input. The target object data, which may be in the form of a 3D map, includes data identifying one or more target objects and their vertical distance from the spray bar (e.g. the distance of a plurality of points on each target object from the spray bar). Using the target object data, the method divides the one or more target objects, or parts thereof, into a plurality of groups as a function of their vertical distance from the spray bar, each group defining a target area (block 902). A target area therefore corresponds to one or more targets and / or parts of one or more targets at a particular vertical distance or within a particular vertical distance range, where a target (or target object) is a plant (or group of plants) that is to be sprayed with the agrochemical.

[0084] Each target area is then considered in turn and using the vertical distance from the spray bar to the target area (as extracted from the target object data in block 902), the 2D non-homogeneous liquid spatial distribution of a nozzle, the nozzle spacing and the forward speed of the spray bar, a pattern of spot sprays is determined that covers the target area such that the cumulative 2D liquid spatial distribution of the spot sprays satisfies pre-defined target dose parameters such as a minimum, maximum and / or average required dose (block 904). Any one or more of the 2D non-homogeneous liquid spatial distribution of a nozzle, the nozzle spacing and the target dose parameters may be fixed or may be received as an input, as shown in Figure 9. The forward speed of the spray bar is provided as an input (e.g. in the form of motion data).

[0085] As described above with reference to Figures 8A and 8B, the size of each spot spray and the resultant 2D liquid spatial distribution for each spot spray (i.e. the 2D dose profile at the distance from the spray bar of the target area) that is used to build up the pattern of spot sprays to meet the pre-defined target dose parameters is dependent upon both the 2D non-homogeneous liquid spatial distribution of a nozzle (e.g. as defined fora static nozzle) and the distance from the spray bar of the target area. The spot spray will be larger for larger distances and smaller for smaller distances with the same 2D non-homogeneous liquid spatial distribution because of the divergent angle of the spray jet and hence the difference in spreading that can occur between the nozzle and the target area.

[0086] As described above with reference to Figure 8C, the size of each spot spray and the resultant 2D liquid spatial distribution for each spot spray (i.e. the 2D dose profile at the distance from the spray bar of the target area) that is used to build up the pattern of spot sprays to meet the pre-defined target dose parameters is also dependent upon the forward speed of the spray bar and nozzle opening duration (i.e. the time between the valve to the nozzle being opened and then subsequently being closed).

[0087] The 2D non-homogeneous liquid spatial distribution of a nozzle (which may also be referred to as the static 2D liquid spatial distribution) will be dependent upon the nozzle design (e.g. the shape and size of the opening) and may also be dependent upon the nozzle flow (i.e. the flow rate of the agrochemical through the nozzle, which may be dependent upon the pressure in the tank and pressure system 116). Alternatively the 2D non-homogeneous liquid spatial distribution of a nozzle may be defined for a reference nozzle flow and may be modified (in block 904) according to a difference between the reference nozzle flow and the actual (e.g. measured) or estimated nozzle flow (e.g. a specified nozzle flow in the operating parameters of the spray system).

[0088] The target areas may be considered in order of progression across the ground being sprayed, such that the target area within the field of view that has a leading edge that is furthest forward (as defined according to the direction of travel of the spray bar) is considered first and the target area within the field of view that has a leading edge that is furthest backwards (as defined according to the direction of travel of the spray bar) is considered last. The leading edge of a target area corresponds to the first point of the target area to enter within the area being scanned 210 and hence the first point of the target area to pass under the spray bar.

[0089] The pattern that is determined (in block 904) for a target area corresponds to a sequence of opening instants and opening durations fora plurality of the nozzles on the spray bar. Different nozzles on the spray bar will be opened and closed at different times to generate the required pattern of spot sprays. Control signals are then generated for an array of nozzles in a spray assembly based on the determined sequences of opening instants and durations for each of the target areas (block 906). The generated control signals may then be output to the spray control system.

[0090] The control signals that are generated (in block 906) may include a control signal for each nozzle in the spray assembly and define when the nozzle opens and when the nozzle closes (which in turn defines the opening instant, i.e. the time at which the nozzle opens, and the opening duration, i.e. the length of time that the nozzle is open for). These time values in turn specify the position of the spot spray (based on the forward speed of the spray assembly) and the size of the spot spray (as this is dependent upon the opening duration which is the interval between the opening and closing of the nozzle). These control signals cause the spray control system to deliver the defined patterns of spot sprays to each target area.

[0091] This method of Figure 9 can be described with reference to the example shown in Figures 10A-1 OF. Figure 10A shows three target areas 1001-1003 (as defined in block 902) and the trajectories of five nozzles, in a direction indicated by arrow 1004, are marked by dotted lines 1006. As described above, each target area corresponds to one or more targets and / or parts of one or more targets at a particular distance or within a particular distance range from the spray bar. In the example shown in Figure 10A, the first target area 1001 is furthest forward in order of progression across the area being sprayed (i.e. the first target area 1001 will be sprayed first), then the second target area 1002 and finally the third target area 1003 is the furthest backward of the target areas identified within the field of view of the imaging system (i.e. of the three target areas, the third target area 1003 will be sprayed last). In terms of vertical distance to the spray bar, the target area 1002 is at the nearest distance from the spray bar, then the target area 1003 is at a medium distance, and finally the target area 1001 is the most distant from the spray bar.

[0092] Figure 10B shows a pattern of spot sprays 1008 that has been determined (in block 904) to cover the first target area 1001 such that the cumulative 2D liquid spatial distribution of the spot sprays satisfies pre-defined target dose parameters. In the example shown, the pre-defined target dose parameters are to minimize the percentage of the target area that does not receive a pre-defined minimum dose per unit area. As in the examples shown in Figures 8A-8C, in Figure 10B the area of each spot spray 1008 where the dose exceeds the pre-defined minimum dose is shown by a shaded grey ellipse 1010. Whilst the entirety of the first target area 1001 is not covered by shaded ellipses 1010, the overlap of the spot sprays 1008 means that areas which are not covered by shaded ellipses 1010 may still receive the pre-defined minimum dose.

[0093] Figure 10C shows a pattern of spot sprays 1012 that has been determined (in block 904) to cover the second target area 1002 such that the cumulative 2D liquid spatial distribution of the spot sprays satisfies pre-defined target dose parameters. The spot sprays 1012 applied to the target area 1002 are smaller than the spot sprays 1008 applied to the target area 1001, indicating that the target area 1002 is at a shorter distance from the spray bar than the target area 1001. Figure 10D shows a pattern of spot sprays 1014 that has been determined (in block 904) to cover the third target area 1003 such that the cumulative 2D liquid spatial distribution of the spot sprays satisfies pre-defined target dose parameters. The spot sprays 1014 applied to this target area 1003 have a size corresponding to the distance of this target area 1003 to the spray bar. As in earlier examples, the area of each spot spray 1012, 1014 where the dose exceeds the pre-defined minimum dose is shown by a shaded grey ellipse.

[0094] It can be seen from comparing the spot sprays 1008, 1012 and 1014 in each of Figures 10B-10D, that the ellipse sizes are different. The spot sprays 1008 in Figure 10B are the largest, indicating that the first target area 1001 is further from the spray bar than either of the other two target areas 1002, 1003. The spot sprays 1012 in Figure 10C are the smallest, indicating that the second target area 1002 is closer to the spray bar than either of the other two target areas 1001, 1003.

[0095] In this example implementation of the method of Figure 9, each target area 1001-1003 is considered independently of any other target areas, irrespective of the proximity of the target areas to each other, i.e. when determining the pattern of spot sprays to cover the second target area 1002, the positioning of any spot sprays to cover the first target area 1001 but which overlap the second target area 1002 is not considered. This simplifies the determination of the patterns of spot sprays (in block 904) and may enable multiple target areas to be considered in parallel, rather than considering each target area sequentially.

[0096] Figure 10E shows the combined patterns for each of the three target areas 1001-1003 and Figure 10F shows the area 1016 which receives the pre-defined minimum dose as a result of the combined patterns shown in Figure 10E. In the example shown, it can be noted that some of the first and third target area surface has not received at least the pre-defined minimum dose. This is because, in this example, the pre-defined target dose parameters (as used in block 904) specify that a minimal percentage of a target area shall receive the predefined minimum dose.

[0097] Although Figure 9 does not show a feedback loop when determining the pattern, as described in more detail below with reference to Figures 12, 15 and 20, there may be feedback to adjust the pattern within each target area in order to meet the pre-defined dose parameters. Additionally, after determining the patterns for each of the target areas within a spray window (in block 904), the patterns may be adjusted to further optimize the patterns to satisfy the pre-defined target dose parameters (e.g. using the same principles as described below with reference to Figures 12, 15 and 20).

[0098] By using the method of Figure 9, the efficiency and adaptability of the spot spraying is increased. By more careful control of the agrochemicals delivered to the target object, including varying the amount sprayed on different parts of a single target object of varying height, so as to guarantee that a target dose per unit area is reached, but without leading to an excess of dosage (within the target area and / or outside the target area), the overall amount of agrochemicals sprayed can be reduced, thereby improving efficiency and effectiveness and reducing the environmental impact of both the use of the agrochemicals and their fabrication and transport. The method can adapt to changes in the spray assembly and the topology of the surface being sprayed in real-time (e.g. in the time between detection of a target object and a nozzle passing over that target object), rather than requiring precise control of the spray height (i.e. the separation of nozzle and the target object).

[0099] In a variation of the method of Figure 9 described above, when determining the pattern of spot sprays for a particular target area (in block 904), any spot sprays from previously determined patterns (for previously considered adjacent target areas) that overlap the particular target area being considered, are also included when determining whether the cumulative 2D liquid spatial distribution of the spot sprays satisfies the pre-defined target dose parameters. This reduces the opportunity to parallelize the generation of patterns for different target areas, but may further reduce the overall amount of agrochemicals sprayed, thereby improving efficiency and effectiveness and reducing the environmental impact of both the use of the agrochemicals and their fabrication and transport. Some parallelization of the generation of patterns can still be used, e.g. two target areas that are separated laterally (i.e. perpendicular to the direction of forward travel) by more than half of the lateral width of the largest spot size used for either area and in the direction of forward travel by more than half of the width of the largest spot size in that direction used for either area cannot have overlapping patterns and so can be considered independently (in block 904).

[00100] In the example shown in Figures 10A-10F and described above, all of the target areas 1001-1003 are fully visible within the field of view. The method of Figure 9 may also be used where one or more target areas extend beyond the field of view, as shown in Figures 11A and 11B. Figures 11A and 11B show two consecutive and contiguous spray windows 1101,1102.

[00101] Figure 11A shows three target areas 1104-1106 (as defined in block 902) and the trajectories of five nozzles, in a direction indicated by arrow 1108, are marked by dotted lines (in the same way as Figures 10A-10F). As described above, each target area corresponds to one or more targets and / or parts of one or more targets at a particular distance or within a particular distance range from the spray bar. Figure 11B shows a further three target areas 1110-1112.

[00102] In the example shown in Figure 11A, the first target area 1104 is furthest forward in order of progression across the area being sprayed, then the second target area 1105 and finally the third target area 1106 is the furthest backward of the target areas identified within the field of view of the imaging system. Unlike the example shown in Figure 10A, in Figure 11A, the third target area 1106 is not fully within the spray window 1101 but extends into the next spray window 1102. The first target area 1110 in Figure 11B is an extension of the third target area 1106 in the immediately previous spray window 1101 (as shown in Figure 11A).

[00103] The method of Figure 9 may be performed independently for each spray window 1101, 1102, such that the method does not take into consideration that the last target area 1106 in one spray window 1101 is contiguous with the first target area 1110 in the next spray window 1102. This means that target object data is input for the first spray window 1101 and used to define the three target areas 1104-1106 (in block 902). Patterns may then be determined for each of the three target areas 1104-1106 (in block 904) either independently, or taking into consideration previously generated patterns of spot sprays for preceding target areas within the same spray window (e.g. taking into consideration the pattern for the first target area 1104 when generating the pattern for the second target area 1105 and taking into consideration the patterns for the first and second target areas 1104, 1105 when generating the pattern for the third target area 1106). Control signals are then generated (in block 906) for the combination of the patterns generated for the entire spray window (i.e. the sum of the three generated patterns) and the control signals are output. Target object data is then input for the second spray window 1102 and used to define the three target areas 1110-1112 (in block 902). As before, patterns may then be determined for each of the three target areas 1110-1112 (in block 904) either independently, or taking into consideration previously generated patterns of spot sprays for preceding target areas within the same spray window. Control signals are then generated (in block 906) for the combination of the patterns generated for the entire spray window (i.e. the sum of the three generated patterns) and the control signals are output.

[00104] Alternatively, the method of Figure 9 may take into consideration that the last target area 1106 in one spray window 1101 is contiguous with the first target area 1110 in the next spray window 1102. The contiguous nature of two target areas may be determined where (i) the trailing edge of a target area in a first spray window 1101 is coincident with a back edge of the spray window (where the back edge is defined with reference to the direction of travel), (ii) a leading edge of a target area in a next spray window is coincident with the front edge of the next spray window (where the front edge is defined with reference to the direction of travel) and (iii) the distances of the two target areas to the spray bar are the same. When determining the pattern for the second of these target areas (e.g. first target area 1110 in the second spray window 1102 in the example of Figures 11A-11B), the method (in block 904) continues the pattern that was already generated for the first of these target areas (e.g. third target area 1106 in the first spray window 1101 in the example of Figures 11A-11B), rather than starting to generate a new pattern afresh. The control signals that are then generated for this particular target area (in block 906) only relate to the new parts of the pattern, and not the parts of the pattern for which control signals have already been generated (when considering the previous spray window).

[00105] When determining the pattern of spot sprays (in block 904), as well as ensuring that the cumulative 2D liquid spatial distribution of the spot sprays in the pattern satisfies predefined target dose parameters within the target area, the method may also seek to minimize the dose falling outside of the target area. This reduces wastage of the agrochemical and reduces chemical residues in soil which can have negative environmental consequences, as described above.

[00106] Figure 12 shows a first example method of determining a pattern of spot sprays that covers a target area such that the cumulative 2D liquid spatial distribution of the spot sprays satisfies pre-defined target dose parameters (i.e. block 904 of Figure 9). As shown in Figure 12, the method comprises defining a position of a first spot spray based on a position of a leading edge of a target area (block 1202). This uses the target area data (i.e. the geometry of the target area) and the target area distance data (i.e. the distance of the target area from the spray bar) that is generated by the preceding step in the method of Figure 9 (in block 902). The method of Figure 12 then comprises defining the initial position, relative to the first spot spray, of one or more new adjacent spot sprays such that the new and existing spot sprays form a continuous spray zone covering at least a portion of the target area (block 1204). The position of the first spot spray may be defined so that the leading edge of the target area receives at least a pre-defined minimum dose, where this pre-defined minimum dose is an example of the target dose parameters, and these target dose parameters may be fixed or variable and various examples it may be received as an input to the method. The leading edge of the target area corresponds to the forward most point of the target area as defined with respect to the direction of motion of the spray bar and hence the first point of the target object to pass under the spray bar.

[00107] The initial positions of the one or more new adjacent spot sprays are defined in terms of initial transverse and longitudinal offsets from the first spot spray. The transverse offsets (which may also be referred to as lateral offsets) are along an axis perpendicular to the direction of travel of the system (and hence parallel to the spray bar) and each transverse offset is a multiple of the nozzle spacing, or effective nozzle spacing where the spray system comprises a plurality of spray bars (e.g. as shown in Figure 3). The longitudinal offsets are along a direction parallel to the direction of travel of the system and each longitudinal offset corresponds to a duration of motion of the spray assembly at a known speed. This speed which corresponds to a speed over the surface on which the target object is located may be referred to as the displacement speed or forward speed to distinguish it from the speed at which a nozzle is turned on and off by controlling the corresponding electromechanical valve. A transverse offset defines which nozzle on a spray bar is used (and hence which electromechanical valve is switched on and off), whereas a longitudinal offset defines the temporal spacing of the spot sprays and hence the control signals. The transverse and longitudinal offsets of the first set of one or more new adjacent spot sprays (as placed in a first iteration of block 1204) are defined relative to the position of the first spot spray, whereas the transverse and longitudinal offsets of any subsequent sets of one or more new adjacent spot sprays (as added in subsequent iterations of the method of Figure 12) may be defined relative to the position of the first spot spray or to an immediately preceding adjacent spot spray.

[00108] As described above, the initial transverse and longitudinal offsets are defined (in block 1204) such that the first spot spray and the one or more new adjacent spot sprays overlap to form a continuous spray zone that covers at least a portion of the target area. For small target areas, the spray zone formed by the first spot spray and first set of one or more new adjacent spot sprays may cover the entire target area, but for larger target areas, the spray zone may not cover the entire target area and hence may only cover a portion of the target area.

[00109] Having determined the position of a first spot spray (in block 1202) and an initial placement for one or more new adjacent spot sprays (in block 1204), the method proceeds to determine (e.g. calculate) a 2D dose map from the combination of new and existing spot sprays and to use the dose may to determine whether to adjust the position of the one or more new adjacent spot sprays (in block 1207) and whether to add more new adjacent spot sprays (in block 1209). The determination of the 2D dose map (in block 1206) comprises calculating the combined dose of the spots.

[00110] The combined dose of the spot sprays is the dose of agrochemicals resulting from the first spot spray (the position of which is defined in block 1202) and the one or more additional spot sprays (the initial position of which are defined in block 1204). As described above, each individual spot spray (i.e. each of the first spot spray and the one or more additional spot sprays) is defined by a non-homogenous 2D liquid spatial distribution, such as shown in Figures 4-6, that assumes that the nozzle is static and is dependent upon the nozzle design; however, as the spray assembly is moving, the resultant 2D liquid spatial distribution for any spot spray is a modified version of the static 2D liquid spatial distribution as a result of the distance between the target area and the spray bar (as received as an input to the method) and the motion during the period of time that the valve associated with the nozzle is open. This described above with reference to Figures 8A-8C above. Figures 8A and 8B show how the distance changes the resultant spot profile. Figure 8C shows an example 1D spot dose profile 822 where the opening duration of the nozzle is double that shown in Figure 8B and where the distance between the spray bar and the target area is the same.

[00111] As the spreading of the static 2D liquid spatial distribution is dependent upon the translational speed (e.g. forward speed) of the spray assembly, in some examples, the opening duration of the nozzles may be adjusted to compensate for changes in speed (e.g. as determined from the motion data that is input to the method). However, as changing the opening duration modifies the dose, even where this is used, the individual spray spots may have different maximum applied doses. This means that the combined dose of the spot sprays and their arrangement, will vary depending upon the local nozzle speed.

[00112] The combined dose corresponds the sum of the resultant 2D liquid spatial distributions for each spot spray, taking into consideration the motion of the spray system. Therefore calculating the combined dose comprises determining the resultant 2D liquid spatial distribution for each spot spray (including taking into consideration characteristics of each nozzle, their speed and their opening duration, where there are differences) and summing the resultant 2D liquid spatial distributions.

[00113] As shown in Figure 12, the static 2D liquid spatial distribution of a nozzle, the nozzle spacing and motion data (e.g. which defines the forward speed of the spray assembly) may be provided as inputs to the method. Alternatively, some or all of them may be fixed (e.g. the method may use a fixed nozzle spacing and / or static 2D liquid spatial distribution, rather than receiving this as an input). Where all the nozzles in a spray assembly are identical, or at least of an identical design, the same static 2D liquid spatial distribution may be used for all nozzles in the spray assembly. Alternatively, where there is more than one type of nozzle within a spray assembly, the static 2D liquid spatial distribution for the nozzle corresponding to the transverse position of the spot spray is used to determine the initial position of the one or more adjacent spot sprays (in block 1204) and to calculate the dose map (in block 1206). The static 2D liquid spatial distribution may also be dependent upon one or more other parameters such as the particular agrochemical mixture being sprayed, its dilution and the pressure in the tank and pressure system. Different static 2D liquid spatial distributions may be used (e.g. selected and input to the method) dependent upon these parameters or their effects may be included in the calculation of the resultant 2D liquid spatial distribution (e.g. in block 1206).

[00114] As described above, the static 2D liquid spatial distribution of a nozzle that is input to the method may be mathematically defined (e.g. in terms of a Gaussian or normal distribution) or input in the form of a pre-calculated look-up table. By using a look-up table, the computational complexity of determining the combined dose and dose map is reduced and this may be advantageous since, as described above, the available time for performing this calculation is very short.

[00115] Having calculated the dose map (in block 1206), the method proceeds to determine whether the dose applied across the target area meets pre-defined criteria (block 1207). These pre-defined criteria may, for example, be that the dose applied at each point in the target area exceeds the pre-defined minimum or that the dose applied at each point in the target area is between the pre-defined minimum and a pre-defined maximum. If the predefined criteria are not met (‘No’ in block 1207), the offsets for the one or more new spot sprays are adjusted to optimise the received dose across the target area (block 1208). This optimisation may use the same pre-defined criteria as in block 1207 or may use additional or alternative criteria. Example optimization criteria may include one or more of the following: (i) the dose applied at each point in the target area exceeds the pre-defined minimum, (ii) the dose applied at each point in the target area is between the pre-defined minimum and a predefined maximum, (iii) the area of the target area that receives at least the pre-defined minimum dose is maximized, (iv) the difference in received dose across the target area is reduced, (v) the received dose across the target area is reduced whilst ensuring that it exceeds the pre-defined minimum at all points in the target area, (vi) the dose at any point of the target area does not exceed a pre-defined maximum dose, and (vii) the overall received dose outside the target area is reduced. As the transverse offset is always a multiple of the nozzle spacing, or effective nozzle spacing, this places a restriction on how the transverse offset can be adjusted whereas there is more flexibility to adjust the longitudinal offset.

[00116] The different optimization criteria (i)-(vii) described above provide different benefits. Criteria (i) and (iii) increase the effectivity of the spraying operation. Criteria (ii) and (vi) ensure that legally authorized levels are not exceeded, or that phytotoxicity does not become a concern in the case of applying agrochemicals such as fertilizers on the crop plants. Criteria (iv) provides a more uniform dose. Criteria (v) reduces the volume of agrochemicals used whilst maintaining effectiveness. Criteria (vii) reduces the wastage of agrochemicals and so increases the efficiency of the spot spray operation and reduces any adverse environmental impacts over over-use of agrochemicals. It also reduces the risk of phytotoxicity for a crop plant adjacent to a target object that was used to define the target area. Criteria (vii) may be important if the target object is a weed and the agrochemical is a herbicide that is not highly selective and hence may affect adjacent crop plants.

[00117] Figure 13 shows how adjusting the offsets can be used to optimise the received dose across the target area. Figure 13 shows three examples 1302, 1304, 1306 with different spacings of the same two spot sprays (with individual liquid spatial distributions 1308, 1310) and in each example the pre-defined minimum (labelled ‘min efficiency’), the maximum applied dose (labelled ‘max applied’) and a pre-defined maximum (labelled ‘max legal’) are shown. Where the two spot sprays overlap, the cumulative dose 1312, 1314, 1316 from the two spot sprays in the overlapping region are also shown as well as the extent 1318 of the target area.

[00118] The first example 1302 shows an initial placement of a first spot spray 1308 on the left and a new adjacent spot spray 1310 on the right. The two spot sprays are overlapping and so form a continuous spray zone and meet the criteria in block 1204; however, the combined dose 1312 does not exceed the pre-defined minimum over the entirety of the target area 1318. In the second example 1304, the offset of the new adjacent spot spray 1310 has been reduced so that the spot sprays 1308, 1310 are closer together. In this second example, the combined dose 1314 does exceed the pre-defined minimum over the entirety of the target area 1318. In the third example 1306, the offset of the new adjacent spot spray 1310 has been reduced further so that the spot sprays 1308, 1310 are closer together than in the second example. In this third example, the combined dose 1316 does exceed the pre-defined minimum over the entirety of the target area 1318. Whether the second or third example is considered more optimum will depend upon the criteria used. In the second example, the maximum applied is lower so the overall dose within the area of the target area is lower than in the third example; however, the overall dose outside of the target area is higher than in the third example.

[00119] Once the dose meets the pre-defined criteria (‘Yes’ in block 1207), the method determines whether the entirety of the target area is covered by the spray zone (block 1209) and if not (‘No’ in block 1209), the method is repeated to place another set of one or more new adjacent spot sprays (in block 1204) and this positions of these newly placed spot sprays may be adjusted, as described above.

[00120] Once the target area, as defined in the input target area data, is fully covered (‘Yes’ in block 1209), the method determines whether all target areas within the spray window have been considered (block 1210) and if patterns have not be generated for all target areas within the spray window (‘No’ in block 1210), the method is repeated for the next target area. Once spray patterns have been generated for all target areas within a spray window (‘Yes’ in block 1210), then the spray patterns are output (e.g. to enable generation of control signals for the valves associated with the nozzles in the spray assembly in block 906 of Figure 9).

[00121] The method of Figure 12 can be described with reference to the example shown in Figure 14. Figure 14 shows a target area 1402 and the trajectories of three nozzles are marked by straight lines 1404. The position of a first spot spray 1406 is determined (in block 1202) based on the position of the leading edge 1407 of the target area 1402. The area 1408 within the spot spray 1406 which receives at least a pre-defined minimum dose is also shown in Figure 14 and the first spot spray 1406 is positioned so that the leading edge 1407 of the target area 1402 receives at least the pre-defined minimum dose (i.e. the leading edge 1407 falls within area 1408).

[00122] The initial position of a new adjacent spot spray 1410 is then defined (in block 1204) such that the two spot sprays 1406, 1410 overlap and form a continuous spray zone that covers a portion of the target area 1402. This initial position of the new adjacent spot spray 1410 is defined in terms of offsets and in the example shown, the initial transverse offset, dx(1), is one nozzle spacing.

[00123] A dose map of the two spot sprays 1402, 1410 is calculated (in block 1206) and used to determine if the resultant dose from the two spot sprays meets pre-defined criteria (in block 1207). This criteria may, for example, be that the dose applied at each point in the target area 1402 exceeds the pre-defined minimum. In the example shown in Figure 14, the combination of the first spot spray 1406 and the initial placement of the second spot spray 1410 does not meet this criteria (‘No’ in block 1207) and so the placement of the second spot spray 1410 is then adjusted (in block 1208). As shown in Figure 14, the transverse offset, dx(1), which is constrained to be a multiple of the nozzle spacing, remains unchanged whereas the longitudinal offset, dy(1), is reduced so that there is a single area 1412 that receives at least the pre-defined minimum dose (instead of two separate areas, as was the case with the initial placement). The optimization of the offsets (in block 1208) increases the proportion of the target area 1402 that receives at least the pre-defined minimum dose.

[00124] The method then proceeds to determine that the entirety of the target area 1402 is not yet fully covered by the placed spot sprays (‘No’ in block 1209) and the initial position of a further spot spray 1414 is then defined (in a second iteration of block 1204) such that new spot spray overlaps with the spray zone of the existing spot sprays 1406, 1410 to form a continuous spray zone that covers the target area 1402. This initial position of the new adjacent spot spray 1414 is defined in terms of offsets and as with the first spot spray, the offsets of the second spot spray 1414 may be adjusted (in block 1208). The third diagram in Figure 14 shows the final position of the newly added second spot spray 1414. The final transverse offset, dx(2) is one nozzle spacing and the final longitudinal offset, dy(2), is less than the longitudinal spacing, dy(1), between the first and second spot sprays. As shown in Figure 14, the combined dose of the three spot sprays 1406, 1410, 1414, delivers at least the pre-defined minimum dose to the entire target area 1402 (i.e. the shaded area 1416 marking the area that receives at least the pre-defined minimum dose covers the entire target area 1402).

[00125] When subsequently generating control signals for this pattern of spot sprays (in block 906 of Figure 9), the final offsets used to generate the pattern in the method of Figure 12 and the known speed of the spray assembly (from the motion data that is input to the method of Figure 9) are used. The transverse offsets generated using the method of Figure 12 define which nozzle is used to create a spot spray, and hence which electromechanical valve receives the corresponding on signal followed by an off signal to create the particular spot spray. The longitudinal offsets are translated into temporal offsets between control signals (e.g. the time difference between a pair of on and off control signals for one spot spray and a pair of on and off control signals for a next spot spray).

[00126] Whilst in the example in Figure 14, three spot sprays are required to cover the target area fully, depending upon the size of the target object a different number of spot sprays may be required (e.g. two or more spot sprays), e.g. as shown in the examples in Figures 10A-10F.

[00127] In the method of Figure 12 described above, the adjusted offsets that are determined (in block 1208) are not determined according to any pattern but based on the dose map (as calculated in block 1208). Figure 15 shows a second example method of determining a pattern of spot sprays that covers a target area such that the cumulative 2D liquid spatial distribution of the spot sprays satisfies pre-defined target dose parameters (i.e. block 904 of Figure 9). The method shown in Figure 15 uses a repeating pattern for target areas that cannot be covered by four adjacent spot sprays. The method shown in Figure 15 is a variation of the methods described above and shown in Figure 12. The method of Figure 15 may be used for target areas of any size (e.g. including those that are smaller than the spray zone of four spot sprays) but is particularly suited to large target areas (e.g. that require more than five spot sprays to coverthem). The method of Figure 9 may use the same method (e.g. the method of Figure 12 or the method of Figure 15) for all target areas or may select a method to use according to the size of the target area. For example, for target areas which are below a threshold size, the method of Figure 12 may be used and for target areas which are above the threshold size, the method of Figure 15 may be used. For target areas which equal the threshold size, either method may be used depending upon the particular implementation.

[00128] As shown in Figure 15, the method starts in the same way as Figure 12; however, having defined the position of the first spot (in block 1202), the initial position of three new adjacent spot sprays is defined (block 1504). As will be described below, lines connecting the centres of the first spot spray and the three new spot sprays define a quadrilateral (e.g. a square, rectangle or rhombus).

[00129] The method continues in the same way as Figure 12 and if the dose from the initial placement of the four spots (the first spot and the additional three spots) does not meet predefined criteria (‘No’ in block 1207), the offsets of the additional three spots are adjusted to optimize the received dose within the quadrilateral defined by the centre points of the four spots (block 1508). The pre-defined criteria used in block 1207 may be the same as described above with reference to Figure 12 or may be modified to relate to the quadrilateral rather than the target area, for example, that the dose applied at each point on the quadrilateral exceeds the pre-defined minimum or that the dose applied at each point on the quadrilateral is between the pre-defined minimum and a pre-defined maximum. Example optimization criteria that may be used in block 1508 may include one or more of the following: (i) the dose applied at each point in the quadrilateral exceeds the pre-defined minimum, (ii) the dose applied at each point in the quadrilateral is between the pre-defined minimum and a pre-defined maximum, (iii) the difference in received dose across the quadrilateral is reduced, (iv) the received dose across the quadrilateral is reduced whilst ensuring that it exceeds the pre-defined minimum at all points on the quadrilateral and (v) the dose at any point of the quadrilateral does not exceed a pre-defined maximum dose. As before, the transverse offset is always a multiple of the nozzle spacing, or effective nozzle spacing, hence this places a restriction on how the transverse offset can be adjusted whereas there is more flexibility to adjust the longitudinal offset.

[00130] Once the dose from the initial placement of the four spots (the first spot and the additional three spots) does meets the pre-defined criteria (‘Yes’ in block 1207), it is determined whether the target area is fully covered (block 1209) and if it is not fully covered, additional spot sprays are placed at the same offsets as the initial three new adjacent spot sprays to further cover the target area (block 1512). The method may iterate around the loop, adding additional spot sprays (in block 1512) until the target area is fully covered (‘Yes’ in block 1209) and the method then proceeds as described above with reference to Figure 12.

[00131] The method of Figure 15 can be further described with reference to the examples shown in Figures 16 and 17. In the example shown in Figure 16, the initial four spots that are placed (in blocks 1202 and 1504) are labelled ‘1’ and the quadrilateral 1602 that is formed from lines that connect their centres is shown. In this example, the transverse spacing, dx, is equal to the nozzle spacing and as a result the quadrilateral is a rectangle or square. When adjusting the offsets (in block 1508) to optimise the received dose within the quadrilateral 1602 (e.g. to ensure that is falls between the pre-defined minimum and maximum at all points within the quadrilateral 1602), the only real freedom is in the longitudinal direction (i.e. adjusting dy) since the transverse spacing is restricted to being a multiple of the nozzle spacing. Having adjusted the offsets, the resultant offsets dx, dy, are used to place additional spot sprays (labelled ‘2’) so that the whole of the target area 1604 receives at least the predefined minimum dose (in block 1512).

[00132] In the example shown in Figure 17, the initial four spots that are placed (in blocks 1202 and 1504) are labelled ‘1’ and the quadrilateral 1702 that is formed from lines that connect their centres is shown. In this example, the transverse spacing, dx, is equal to twice the nozzle spacing and as a result the quadrilateral is a rhombus. When adjusting the offsets (in block 1508) to optimise the received dose within the quadrilateral 1702 (e.g. to ensure that is falls between the pre-defined minimum and maximum at all points within the quadrilateral 1702), the only real freedom is in the longitudinal direction (i.e. adjusting dy) since the transverse spacing is restricted to being a multiple of the nozzle spacing. As shown in Figure 17, the initial four spot sprays involve two longitudinal offsets, dy; however, these offsets are the same and when performing the adjustment (in block 1508), they remain the same. Having adjusted the offsets, the resultant offsets dx, dy, are used to place additional spot sprays (labelled ‘2’) so that the whole of the target area 1704 receives at least the pre-defined minimum dose (in block 1512).

[00133] By using a repeating pattern for larger target areas, as shown in Figures 15-17, the computational effort in calculating the control signals is reduced and, as described above, this is advantageous because the time available to generate the control signals is very limited.

[00134] Figures 18 and 19 show two variations on the arrangement shown in Figure 17. The spot sprays are placed in Figures 18 and 19 using the method of Figure 15; however, the rows of spot sprays are not aligned perpendicularly to the forward direction but are at a small angle off from perpendicular. This means that the opening of the nozzles happens at different times (i.e. as they are not aligned in the forward direction) and this results in less demanding pressure regulation within the spray system. In the example shown in Figure 18, the orientation of the nozzles is such that each individual spot spray has an elliptical shape with a minor axis that is aligned with the forward direction and this results in a non-symmetrical pattern of spot sprays. In contrast, in the example shown in Figure 19, the orientation of the spot sprays is also tilted by the same angle (e.g. rotated along the vertical axis by around 10°) so that the major axes of the spot sprays in a row are aligned. This results in a symmetrical pattern of spot sprays.

[00135] In a variation of the methods described above, in addition to adjusting the offsets (in blocks 1208 and 1508), the opening duration of the nozzles may be adjusted (e.g. to satisfy one or more of the criteria (i)-(vii) described above with reference to Figure 12 or one or more of the criteria (i)-(v) described above with reference to Figure 15). As described above with reference to Figure 13, adjusting the opening duration of a valve, and hence a nozzle, changes the static 2D liquid spatial distribution and results in both an increased dose and increased spreading in the longitudinal direction when calculating the resultant 2D liquid spatial distribution (that includes the effect of the motion of the spray assembly).

[00136] In the method of Figure 15 described above, the offsets are determined and adjusted dynamically during the spray operation (i.e. as the field is being scanned by the imaging system). In a variation of this, the offsets that are used (in block 1504) may be selected from a set of pre-calculated tables. These tables are generated in advance of the spray operation and may be used for many spray operations. Memory is required to store these tables, although this memory may be remote from the spot spray control system 102 (e.g. it may be stored in a remote data center) but the use of pre-calculated tables eliminates the computation required during the spray operation and enables the spot sprays to be positioned more quickly. The pre-calculated tables may define longitudinal offsets for a first spot spray and transverse and longitudinal offsets for new adjacent spot sprays along with the opening duration for each spot spray for different values of one or more of the following parameters: speed, dose requirements (e.g. minimum and / or maximum dose), pressure and distance between the nozzle and the target area.

[00137] In many of the examples described above, the pre-defined target dose parameter that is used involves ensuring that all parts of the target area receive at least a pre-defined minimum dose. In a variation of the methods described above, the criteria may be modified so that at least a minimum proportion of the target area (e.g. at least 90% of the target area) receives the pre-defined minimum dose. Where both a pre-defined minimum and pre-defined maximum are used, the pre-defined maximum must not be exceeded at any point within the spray zone, even if this has the effect that a small part of the target area receives less than the pre-defined minimum.

[00138] The above examples have only described actions and criteria relating to target objects and target areas, where the target object, is a plant that is to be sprayed with the agrochemical. In a variation on any of the methods described above, the pre-defined target dose parameters may also provide criteria relating to avoid objects, where an avoid object is a plant that does not require spraying or even shall not be sprayed (e.g. where the agrochemical is a pesticide and the avoid object is the crop that is being grown). For example, in addition to a pre-defined target dose parameter (such as a minimum dose) for a target area, a pre-defined target dose parameter (such as a predefined, non-zero, maximum dose of the agrochemical) is defined for a proximate avoid object. In such a variation, the inputs to the method of Figure 9 additionally comprise avoid object data which may be in the form of a 3D map (like that for target objects) or 2D map (since distance data is not required for avoid objects). In some examples, a 3D map may be input that comprises data for both target objects and avoid objects.

[00139] The maximum dose that is defined in relation to the proximate avoid object may be a local dose (i.e. a maximum dose that should be applied to any part of the target object) or a global dose (i.e. a maximum dose that should be applied to the target object as a whole). For a local maximum dose, it may be defined in terms of an amount of the agrochemical per unit area (e.g. in g / cm2 or ml / cm2). For a global maximum dose, it may be defined in terms of an absolute amount of the agrochemical for the avoid plant (e.g. in g or cm3). This absolute amount may be derived from an amount of the agrochemical per unit area (e.g. in g / cm2 or ml / cm2) by multiplying by the total area of the plant. The total area of the plant may be determined by the imaging system 106 (e.g. using image analysis).

[00140] As described above, the maximum dose is non-zero (i.e. it is more than zero) which means that some of the agrochemical will be sprayed onto the avoid object and the maximum dose may be defined to avoid negative effects such as death I damage of the avoid object or undesirable (or unsafe) levels of residues within the plant (e.g. where the avoid object is a crop plant) or improved growth (e.g. where the avoid object is a weed).

[00141] It will be appreciated that there may be more than one proximate avoid object that is identified. Where there is more than one avoid object, the patterns that are defined collectively satisfy the maximum dose criteria for each avoid object. The maximum dose may be the same for all avoid objects or it may depend on the type of the avoid object (e.g. as classified by the imaging system). For example, when several species of avoid plants are present in a same field, a maximum dose may be defined for each specie, for instance to take into account their sensitivity to the chemicals in use. If a species is less prone to damage than another one, it is preferable to adjust the level tolerated so as to facilitate the application of a minimum amount to target plants in a direct vicinity.

[00142] Figure 20 shows a first example method of determining a pattern of spot sprays that covers a target area such that the cumulative 2D liquid spatial distribution of the spot sprays satisfies pre-defined target dose parameters for both target areas and one or more proximate avoid objects (i.e. block 904 of Figure 9). As shown in Figure 20, the method comprises placing a first spot spray is placed as close as possible to the proximate avoid object without exceeding the maximum, non-zero, dose on the avoid object (block 2002). One or more additional spot sprays are then placed as close as possible to the proximate avoid object to form a continuous spray region of at least the minimum dose over a portion of the target area whilst not exceeding the maximum, non-zero dose on the avoid object from the combination of the first spot spray and these newly placed additional spot sprays (block 2004). Finally, one or more further spot sprays are placed, if and where necessary, further from the proximate avoid object to extend the continuous spray region so that it fully covers the target area (block 2006). Within the continuous spray region, the dose at any point is not less than the predefined minimum dose. The method is repeated until all target areas have been processed (‘Yes’ in block 2008). The term ‘processed’ is used in the context of Figure 20 to refer to placing spot sprays over the target area (i.e. performing blocks 2002-2006 in relation to that target area) to generate a spray pattern for the target area that satisfies the pre-defined target dose parameters.

[00143] As in the previous example methods described above, the positions of the spot sprays that are placed in the method of Figure 20 are constrained in the axis perpendicular to the direction of travel of the system (and hence parallel to the spray bar) by the nozzle spacing, or effective nozzle spacing where the spray system comprises a plurality of spray bars (e.g. as shown in Figure 3). This axis which is perpendicular to the direction of travel of the system may be referred to as the transverse axis and the position of the spot sprays along this axis may be referred to as transverse offsets (e.g. from an origin at one end of the spray bar). The longitudinal offsets are along a direction parallel to the direction of travel of the system (and perpendicular to the spray bar) and each longitudinal offset corresponds to a duration of motion of the spray assembly at a known speed. This speed which corresponds to a speed over the surface on which the target object is located may be referred to as the displacement speed or forward speed to distinguish it from the speed at which a nozzle is turned on and off by controlling the corresponding electromechanical valve. The transverse offset defines which nozzle on a spray bar is used (and hence which electromechanical valve is switched on and off), whereas a longitudinal offset defines the temporal spacing of the spot sprays and hence the control signals.

[00144] In addition to defining the position of each spot spray, the opening duration of the nozzle is also defined. As described above, the 2D liquid spatial distribution of a spot spray is dependent upon on its opening duration. In some examples, the same opening duration may be used for all spot sprays, and in other examples, the opening duration may differ between spot sprays.

[00145] The methods described above may be implemented by a spot spray control system, such as the spot spray control system 102 shown in Figure 1. The spot spray control system may be implemented by one or more processors. The one or more processors can be programmable (e.g., a central processing unit (CPU) or a microcontroller), a field programmable gate array (FPGA), DSP, ASICs, PLC and / or one or more ARM processors, etc. Figure 21 illustrates various components of an example spot spray control system in the form of a computing-based device 2100. As described above, this computing-based device may also perform some of the functionality of the imaging system 106 shown in Figure 1.

[00146] Computing-based device 2100 comprises one or more processors 2102 which may be microprocessors, controllers or any other suitable type of processors for processing computer executable instructions to control the operation of the device in order to perform the methods described herein (e.g. as shown in Figures 9, 12, 15 and 20). In some examples, for example where a system on a chip architecture is used, the processors 2102 may include one or more fixed function blocks (also referred to as accelerators) which implement a part of the method of controlling a spot spray system in hardware (rather than software or firmware). Platform software comprising an operating system 2104 or any other suitable platform software may be provided at the computing-based device to enable application software 2106, such as software that implements the methods described herein, to be executed on the device.

[00147] The computer executable instructions may be provided using any computer-readable media that is accessible by computing-based device 2100. Computer-readable media may include, for example, computer storage media such as memory 2108 and communications media. Computer storage media, such as memory 2108, includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EPROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information for access by a computing device. In contrast, communication media may embody computer readable instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave, or other transport mechanism. As defined herein, computer storage media does not include communication media. Although the computer storage media (memory 2108) is shown within the computing-based device 2100 it will be appreciated that the storage may be distributed or located remotely and accessed via a network or other communication link (e.g. using communication interface 2110).

[00148] The communication interface 2110 may be arranged to receive data used in the methods described herein such as motion data (e.g. from vehicle 206 shown in Figure 2A or from a sensor within the spot spray system) and target object data (e.g. from the imaging system 106). The communication interface 2110 may also be arranged out output the generated control signals (e.g. to the electromechanical valves 114 in the spray assembly 104).

[00149] The computing-based device 2100 may also comprises an input / output interface 2112 arranged to output display information to a display device 2114 which may be separate from or integral to the computing-based device 2100. For example, a display device 2114 may be attached to the body 204 of the spot spraying system 200 shown in Figure 2A or positioned in the vehicle 206. In addition, or instead, the display information may be output via the communication interface 2110 to a remote display device 2114 (in a monitoring location that is remote from the spot spray system). The display information may provide a graphical user interface. The input / output interface 2112 may also be arranged to receive and process input from one or more devices, such as a user input device 2116 (e.g. one or more buttons on the body 204 of the spot spraying system 200 shown in Figure 2A or positioned in the vehicle 206). This user input may be used to adjust parameters of the method or provide inputs, such as the pre-defined minimum dose. In an embodiment the display device 2114 may also act as the user input device 2116 if it is a touch sensitive display device. In some examples the input / output interface 2112 may be arranged to output the generated control signals (e.g. to the electromechanical valves 114 in the spray assembly 104) instead of, or in addition to, the communication interface 2110.

[00150] The memory 2108 may be arranged to store data used by the methods described herein, such as the static 2D liquid spatial distributions 2118 and configuration data for the spray assembly 2120 (e.g. nozzle spacing). Where the modified version of the method of Figure 15 is used, the memory 2108 may be arranged to store the pre-calculated tables.

[00151] Whilst Figure 21 shows a single computing device that may be implemented locally within the spot spray system 100, 200 shown in Figures 1 and 2A, in other examples some of the processing and / or data storage may be implemented remotely from the spray assembly, e.g. on a remote computing device that may be located in a data center or elsewhere. For example, the static 2D liquid spatial distributions 2118 and / or configuration data for the spray assembly 2120 may be stored remotely and accessed via the communication interface 2110. In addition or instead, the computation of the dose map (in block 706) and offset modification (in blocks 1208 and 1508) may be performed by a remote computing device and the resultant modified offsets received by the spray system via the communication interface 2110. In other examples, the processing and / or data storage may be split in a different way between a local computing device proximate to the spray assembly and a remote computing device (or plurality of local computing devices, e.g. where the data processing is performed on a different computing device to the data storage).

[00152] The term 'computer' is used herein to refer to any device with processing capability such that it can execute instructions. Those skilled in the art will realize that such processing capabilities are incorporated into many different devices and therefore the term 'computer' includes PCs, servers, mobile telephones, personal digital assistants and many other devices.

[00153] Those skilled in the art will realize that storage devices utilized to store program instructions can be distributed across a network. For example, a remote computer may store an example of the process described as software. A local or terminal computer may access the remote computer and download a part or all of the software to run the program. Alternatively, the local computer may download pieces of the software as needed, or execute some software instructions at the local terminal and some at the remote computer (or computer network). Those skilled in the art will also realize that by utilizing conventional techniques known to those skilled in the art that all, or a portion of the software instructions may be carried out by a dedicated circuit, such as a DSP, programmable logic array, or the like.

[00154] Any range or device value given herein may be extended or altered without losing the effect sought, as will be apparent to the skilled person.

[00155] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages.

[00156] Any reference to 'an' item refers to one or more of those items. The term 'comprising' is used herein to mean including the method blocks or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

[00157] The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the spirit and scope of the subject matter described herein. Aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples without losing the effect sought.

[00158] It will be understood that the above description of a preferred embodiment is given by way of example only and that various modifications may be made by those skilled in the art. 5 Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention.

Claims

1. A method of operation of a spot spray control system for spraying agrochemicals on target objects using a moveable spray assembly, the spray assembly comprising an imaging system and a spray bar perpendicular to a travel direction of the spray assembly, wherein the spray bar comprises an array of nozzles positioned linearly along the spray bar, each nozzle configured to produce a divergent jet with a defined non-homogeneous two-dimensional liquid spatial distribution and wherein an opening instant and opening duration of each nozzle is individually controllable, the method comprising:receiving a three-dimensional map of a first spray window generated by the imaging system, the three-dimensional map defining positions of one or more target objects, the one or more target objects comprising portions of target objects at different distances from the spray bar;dividing the portions of the one or more target objects into a plurality of groups as a function of their distance from the spray bar, each group defining a target area (902);determining a pattern of spot sprays for each target area, such that for a target area, a cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern for the target area satisfies pre-defined target dose parameters, wherein each spot spray in the pattern is defined by the distance of the target area from the spray bar, the non-homogeneous two-dimensional liquid spatial distribution of a nozzle in the array of nozzles and a forward speed of the spray assembly (904);generating control signals corresponding to the defined patterns, wherein the control signals define, for each spot spray, an opening instant and opening duration of a nozzle in the array of nozzles (906); andoutputting the control signals to the spray assembly.

2. The method according to claim 1, wherein the pre-defined target dose parameters define a minimum dose per unit area.

3. The method according to any of the preceding claims, wherein the pre-defined target dose parameters define a maximum dose per unit area.

4. The method according to any of the preceding claims, wherein the pattern of spot sprays is further defined to minimize a dose falling outside the target area.

5. The method according to any of the preceding claims, wherein determining a pattern of spot sprays for each target area comprises:sequentially selecting each target area according to a distance of a leading edge of the target area from a front edge of the field of view of the imaging system; anddetermining, for the selected target area, a pattern of spot sprays for the target area, such that the cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern satisfies the pre-defined target dose parameters.

6. The method according to claim 5, further comprising repeating the method for a second spray window.

7. The method according to claim 6, wherein, if the first target area in the second spray window has a same distance from the spray bar as a last target area in the first spray window, determining the pattern of spot sprays for the first target area in the second spray window comprises continuing the pattern of spot sprays for the last target area in the first spray window to cover the first target area in the second spray window such that the cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern satisfies the predefined target dose parameters.

8. The method according to any of claims 5-7, wherein the pattern of spot sprays for a selected target area within a spray window is determined independently of the pattern of spot sprays for any previously selected target area within a same spray window.

9. The method according to any of claims 5-7, wherein the pattern of spot sprays for a selected target area within a spray window is determined taking into consideration any overlap of the pattern of spot sprays for a previously selected adjacent target area within a same spray window with the selected target area.

10. The method according to any of the preceding claims, wherein determining a pattern of spot sprays for each target area, such that for a target area, a cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern for the target area satisfies predefined target dose parameters comprises:(i) defining a position of a first spot spray based on a position of a leading edge of a target area (1202);(ii) defining an initial position in terms of a transverse offset and a longitudinal offset relative to the first spot spray, of at least one new adjacent spot spray (1204, 1504) such that the combined dose of the first and new spot sprays forms a continuous spray zone thatcovers a portion of the target area, wherein each of the first and new spot sprays is defined by a non-homogeneous two-dimensional liquid spatial distribution and the transverse offset is a multiple of an effective spacing of the nozzles in the array of nozzles;(iii) determining a two-dimensional dose map resulting from the first and new spot sprays (1206); and(iv) in response to determining, from the two-dimensional dose map, that pre-defined dose criteria are not met (1207), adjusting the offsets of the at least one new adjacent spot spray to optimise a received dose (1208, 1508).

11. The method according to claim 10, further comprising:in response to determining, from the two-dimensional dose map, that the target area is not fully covered by the spray zone (1209), repeating steps (ii)-(iv) until the target object is fully covered.

12. The method according to claim 10, wherein the at least one new adjacent spot spray comprises three new adjacent spot sprays (1504); and whereinadjusting the offsets of the at least one new adjacent spot spray to optimise a received dose comprises:adjusting the offsets of the three new adjacent spot sprays to optimise a received dose within a quadrilateral defined by the first spot spray and the three new adjacent spot sprays (1508);and wherein the method further comprises:in response to determining that the target area is not fully covered (1209), placing additional spot sprays at the same offsets to further cover the target area (1512).

13. The method according to any of claims 1-9, wherein the three-dimensional map defines positions of one or more avoid objects and wherein determining a pattern of spot sprays for each target area, such that for a target area, a cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern for the target area satisfies pre-defined target dose parameters comprises:placing a first spot spray as close as possible to a proximate avoid object without exceeding a pre-defined maximum, non-zero, dose on the proximate avoid object (2002);placing one or more additional spot sprays as close as possible to the proximate avoid object to form a continuous spray region of at least the minimum dose over a part of the target area whilst not exceeding the maximum, non-zero, dose on the proximate avoid object (2004); andif the pre-defined target dose parameters for the target area are not satisfied, placing one or more further spot sprays (2006).

14. The method according to any of the preceding claims, wherein the non-homogeneous two-dimensional liquid spatial distribution of a nozzle is defined in a look-up table.

15. The method according to any of claims 1-13, wherein the non-homogeneous two-dimensional liquid spatial distribution of a nozzle as a function of the distance from nozzle to target, the forward speed and the nozzle opening duration, is defined in a look-up table.

16. The method according to any of claims 1-13, wherein the non-homogenous two-dimensional liquid spatial distribution of a nozzle is defined using a Gaussian or normal distribution.

17. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method of any of the preceding claims.

18. A computer-readable medium having stored thereon the computer program of claim 17.

19. A spot spray control system for spraying agrochemicals on target objects using a moveable spray assembly, the spray assembly comprising an imaging system and a spray bar perpendicular to a travel direction of the spray assembly, wherein the spray bar comprises an array of nozzles positioned linearly along the spray bar, each nozzle configured to produce a divergent jet with a defined non-homogeneous two-dimensional liquid spatial distribution and wherein an opening instant and opening duration of each nozzle is individually controllable, and the spot spray control system comprising:a processor (2102);one or more interfaces (2110, 2112) configured to receive target object data and output control signals to the spray assembly; andmemory (2108) arranged to store a computer program which, when executed by the processor, causes the control system to:receive a three-dimensional map of a first spray window generated by the imaging system, the three-dimensional map defining positions of one or more target objects, the one or more target objects comprising portions of target objects at different distances from the spray bar;divide the portions of the one or more target objects into a plurality of groups as a function of their distance from the spray bar, each group defining a target area (902);determine a pattern of spot sprays for each target area, such that for a target area, a cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern for the target area satisfies pre-defined target dose parameters, wherein each spot spray in the pattern is defined by the distance of the target area from the spray bar, the non-homogeneous two-dimensional liquid spatial distribution of a nozzle in the array of nozzles and a forward speed of the spray assembly (904);generate control signals corresponding to the defined patterns, wherein the control signals define, for each spot spray, an opening instant and opening duration of a nozzle in the array of nozzles (906); andoutput the control signals to the spray assembly.

20. The spot spray control system according to claim 19, wherein the pre-defined target dose parameters define a minimum dose per unit area and / or a maximum dose per unit area.

21. The spot spray control system according to claim 19 or 20, wherein the pattern of spot sprays is further defined to minimize a dose falling outside the target area.

22. The spot spray control system according to any of claims 19-21, wherein the computer program, when executed by the processor, causes the control system to determine a pattern of spot sprays for each target area by:sequentially selecting each target area according to a distance of a leading edge of the target area from a front edge of the field of view of the imaging system; anddetermining, for the selected target area, a pattern of spot sprays for the target area, such that the cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern satisfies the pre-defined target dose parameters.

23. The spot spray control system according to claim 22, wherein the computer program, when executed by the processor, causes the control system to determine a pattern of spot sprays for each target area by additionally:repeating the method for a second spray window, wherein, if the first target area in the second spray window has a same distance from the spray bar as a last target area in the first spray window, determining the pattern of spot sprays for the first target area in the second spray window comprises continuing the pattern of spot sprays for the last target area5 in the first spray window to cover the first target area in the second spray window such that the cumulative two-dimensional liquid spatial distribution of the spot sprays in the pattern satisfies the pre-defined target dose parameters.

24. The spot spray control system according to claim 22 or 23, wherein the pattern of spot sprays for a selected target area within a spray window is determined independently of10 the pattern of spot sprays for any previously selected target area within a same spray window.

25. The spot spray control system according to claim 22 or 23, wherein the pattern of spot sprays for a selected target area within a spray window is determined taking into consideration any overlap of the pattern of spot sprays for a previously selected adjacent target area within a same spray window with the selected target area.15Application No:     GB2416813.0               Examiner:      Liz Paramo-BritlandClaims searched: 1-25 Date of search: 17 April 2025Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance A A,E A A A - WO 2019 / 226869 Al (BLUE RIVER TECH INC) See figures 1A-14, noting spot spray system 100 comprising camera 110, treatment map 510, and treatment mechanism 120 GB 2630350 A (ECOROBOTIX SA) See figures 1-18, noting spot spray system 200 comprising camera 202 and an array of individually controllable nozzles 110 US 2015 / 0245565 Al (PILGRIM et al.) See figures 1-6, noting spot spray system 100 comprising camera 104 and individually controllable nozzles 144 US 2020 / 0045953 Al (SERRAT et al.) See figures 1-6, noting spot spray control system 40 comprising camera 42 and nozzles 34 US 2024 / 0306627 Al (TANNER) See figures 1-8B, noting spot spray system 200 comprising camera 270 and nozzles 220Categories: X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if combined with one or more other documents of same category. P Document published on or after the declared priority date but before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:Search of GB, EP, WO &US patent documents classified in the following areas of the UKCX :Worldwide search of patent documents classified in the following areas of the IPC_____________AO IB; AO IC; AO IM; B05B_________________________________________The following online and other databases have been used in the preparation of this search reportSEARCH-PATENT, INTERNETInternational Classification:Subclass Subgroup Valid From B05B 0012 / 12 01 / 01 / 2006 AO IB 0079 / 00 01 / 01 / 2006 A01C 0021 / 00 01 / 01 / 2006 A01C 0023 / 04 01 / 01 / 2006 AO IM 0007 / 00 01 / 01 / 2006

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