Method and control unit for controlling a spray unit of an agricultural spraying system

Abstract

Processing circuitry for controlling an agricultural spraying system 102 with a fluid delivery rail 108 for supplying a spray unit. There is a rail pressure sensor 404 and one or more auxiliary sensors 414, such as a camera, laser, or GPS, each configured to output a auxiliary sensor signal corresponding to a target vegetative item to be sprayed. The spray unit comprises a fluid ejector with a heater and a flow control valve. The method comprises receiving a current delivery pressure signal output by the pressure sensor and receiving the auxiliary sensor signal(s) and using these signals and one or more predetermined transformation to derive drive signals for the heater and flow control valve to actuate the ejector. A control unit 406 and an agricultural spraying system incorporating this method and processing circuitry are also disclosed. There may be pressure control device. A signal indicative of vehicle speed may be also used to determined a heater timing control signal.

Description

Technical field

[0001] The present invention generally relates to fluid spraying techniques for agricultural applications. The invention more particularly relates to an improved method, control unit and agricultural spraying system, for controlling a spray unit of the agricultural spraying system. Background Art

[0002] Crop spraying in agriculture requires control over spray droplet size in order to control the retention of the fluid on the plant, avoid excessive pollution and minimize cost. The type of pest to be eliminated, the weather conditions or even the location on the field require different spray droplet sizes. Larger droplet sizes for example are required during spraying in more windy conditions or warm conditions to ensure the fluid arrives in the correct location on the crop. Also, bug type pest elimination benefits from larger droplet sizes. Other diseases require smaller droplet sizes for highest effectiveness. Finally, larger droplets for drift reduction may be required on headlands to minimize impact on open water quality, whereas in the middle of the field more drift is permissible.

[0003] As discussed in further detail below, it is known to use agricultural spraying equipment comprising a vehicle having a rail mounted to it and upon which multiple spray units are mounted, for spraying crops, including individual vegetative items (e.g., plants or weeds), as the vehicle traverses an area such as a field of crops. Technical problem

[0004] A problem is that, with known techniques, the control of spray droplet size, amount of fluid sprayed and spray form / profile cannot be optimized for a given spray operation by a spray unit (or for all or a subset of spray units), and / or that complex mechanical I hydraulic parts are required in order to have a spray operation by a spray unit performed with desired or ideal spray properties.

[0005] It is an object of the present invention to avoid the foregoing issue and to provide a method, control unit and agricultural spraying system that take into 19 07 24 account the characteristics (e.g., type, size and / or location) associated with a target vegetative item so as to enhance or optimize spray droplet size, amount of fluid sprayed and / or spray profile for that vegetative item. General Description of the Invention

[0006] In order to overcome the above-mentioned issue, there is provided a method carried out by processing circuitry, for controlling a spray unit of an agricultural spraying system, the agricultural spraying system including a fluid delivery rail for supplying the spray unit, a pressure sensor being configured to output a delivery pressure signal indicative of the current pressure of the fluid in the fluid delivery rail, the agricultural spraying system further including one or more auxiliary sensors each configured to output a respective auxiliary sensor signal corresponding to a target vegetative item to be sprayed, the spray unit comprising an ejector and being configured to perform one or more ejection operations in which a quantity of fluid is ejected by the ejector, the ejector having a heater configured to heat fluid passing through the ejector in response to a heater drive signal and a flow control valve configured to prevent or allow the flow of fluid passing through the ejector in response to an actuator drive signal, the method comprising: receiving the current delivery pressure signal output by the pressure sensor; receiving the auxiliary sensor signal(s) from the or each auxiliary sensor, wherein (i) the one or more auxiliary sensors comprise an imaging device and the auxiliary sensor signal(s) comprise a captured image of the target vegetative item or (ii) the one or more auxiliary sensors comprise a positioning device and the auxiliary sensor signal(s) comprise a current position corresponding to the target vegetative item; deriving (determining), based on the current delivery pressure signal and one or more of the auxiliary sensor signals, and using one or more predetermined transformations, (i) a current heater drive signal defining a heating amount for a current ejection operation and (ii) a current actuator drive signal defining an actuation duration during which fluid flow is allowed in the current ejection operation; operating the heater of the ejector based on the current heater drive signal; and operating the flow control valve of the ejector based on the current actuator drive signal.

[0007] Particular embodiments are set out in claims 2 to 24 of the appended claims.

[0008] As used herein, the term ejector typically designates a device that is selectively operable to carry out an ejector event, by which a controlled amount of fluid is discharged or sprayed into the environment, towards a predetermined item such as a plant or crop. Advantageously, the ejector includes a nozzle portion with 19 07 24 an outlet orifice controlled by a valve member that can be electromagnetically actuated. Preferably, the ejector can be designed as a fuel injector. In embodiments, the ejector can be a fuel injector with the outlet orifice at its tip, referred to as tip fuel injector.

[0009] According to another aspect of the present invention, there is provided a control unit, for controlling a spray unit of an agricultural spraying system, the control unit comprising the processing circuitry configured to carry out the method of any of claims 1 to 24 of the appended claims.

[0010] According to another aspect of the present invention, there is provided an agricultural spraying system comprising: a vehicle and, mounted thereto, a fluid delivery rail for supplying a spray unit, a delivery rail pressure sensor being configured to output a delivery pressure signal indicative of the current pressure of the fluid in the fluid delivery rail, one or more spray unit being mounted to and supplied by the fluid delivery rail; one or more auxiliary sensors each configured to output a respective auxiliary sensor signal corresponding to a target vegetative item to be sprayed, wherein the or each spray unit comprises an ejector having a heater configured to heat fluid passing through the ejector in response to a heater drive signal and a flow control valve configured to control the flow of fluid passing through the ejector in response to an actuator drive signal; and, the agricultural spraying system further comprises the control unit of the previous paragraph.

[0011] According to another aspect of the present invention, there is provided a computer program product comprising instructions which, when executed by processing circuitry, cause the method of any of claims 1 to 24 of the appended claims to be performed.

[0012] An advantage of the invention is to enhance or optimize spray droplet size, amount of fluid sprayed and / or spray profile for a target vegetative item when sprayed with a spray unit of an agricultural spraying system. Brief Description of the Drawings

[0013] Further details and advantages of the present invention will be apparent from the following detailed description of a non-limiting embodiment with reference to the attached drawings, wherein: Figure 1 (PRIOR ART) shows an agricultural spraying system, as used in known techniques for crop spraying in agriculture; Figure 2 (PRIOR ART) illustrates a known form of activated spray unit, as used in known techniques for crop spraying in the system of Fig. 1; Figure 3 shows a fluid ejector for use in techniques according to inventive embodiments disclosed herein; Figure 4 is a schematic illustration of a control system for use in techniques according to inventive embodiments disclosed herein; Figure 5 is a flowchart of a process for controlling a spray unit of an agricultural spraying system using techniques according to inventive embodiments disclosed herein; and Figure 6 is a schematic diagram of a control unit according to inventive embodiments disclosed herein, for use in the control system of Fig. 4. Description of Preferred Embodiments

[0014] In the following, like reference numerals denote like parts, and any element, design feature or method step of any embodiment may be used in combination with an element, design feature or method step of any other embodiment unless stated otherwise herein. As used herein, “fluid” means liquid (e.g., in a reservoir, flowing through a pump and / or in a fluid delivery rail) ora mixture of liquid and gas (e.g., within or ejected by an ejector / tip injector), as appropriate and depending on location within the system, as discussed in more detail hereinafter.

[0015] Initially, reference is made to Fig. 1 (PRIOR ART), which shows an agricultural spraying system, as used in known techniques for crop spraying in agriculture. Figure 2 (PRIOR ART) illustrates a known form of activated spray unit, as used in known techniques for crop spraying in the system of Fig. 1.

[0016] Figure 1 (PRIOR ART) shows a self-propelled agricultural spray machine 102 comprising a vehicle 104 having mounted thereto a boom 106 carrying a spraying fluid (e.g., liquid) delivery rail 108 on which the spray units 110 are mounted. Fluid flow through the spray units 110 may be controlled for the rail 106 as a whole, per rail section 112, 112’, 112” or per spray unit 110 using solenoid operated valves (not shown). As seen in Fig. 2 (PRIOR ART), each spray unit 110 consists of a plurality (e.g., up to 5) nozzles 202A, 202B, 202C, 202D and 202E for directing the fluid flow onto the crop (not shown). The nozzles 202A-202E have individual (i.e., different, preconfigured) spray characteristics and are selected based on the spray droplet requirement for the given fluid application. A particular nozzle 202A-202E can be selected at any given time (i.e., by rotation of the nozzle set around an axis until a desired nozzle is aligned with a fluid input that is in fluid communication with the fluid delivery rail 108), and such nozzle selection may be manual or pneumatic.

[0017] Activation of the spray unit(s) 110 with a rail section 112, 112’, 112”, or activation of an individual spray unit 110 may be based on pre-defined GPS based maps or using a camera-based input. Camera-based inputs enable spot spraying, further enabling optimization of spraying fluid consumption and reduction of environmental impact.

[0018] However, with the known techniques of Figs 1 (PRIOR ART) and 2 (PRIOR ART), a number of mechanical devices and control systems are required to adequately control the treatment of agricultural crops in a suitable fashion.

[0019] The techniques according to embodiments disclosed herein for controlling a spray unit of an agricultural spraying system 102, may be as described hereinabove with respect to Fig. 1 (PRIOR ART), except as indicated otherwise hereinafter.

[0020] Figure 3 shows a fluid ejector 302 for use in techniques according to embodiments of the invention disclosed herein, where a) is a cross-section through the ejector 302 with over-molded housing 303 and b) is a perspective view of the ejector without over-molded housing 303. The ejector 302 may take the form of a tip injector and be part of a spray unit (not shown) that may include the housing 303, one or more attachment members (not shown) for fixedly attaching the ejector 302 to the rail 108 (Fig. 1 (PRIOR ART)) and / or one or more connectors (not shown) for connecting fluid conduits (e.g., on the fluid delivery rail 108) to the ejector 302. Spray units with ejectors 302 may be substituted for the spray units 110 in Fig. 1 (PRIOR ART).

[0021] The ejector 302 has a heater 304 configured to heat fluid (not shown) passing through the ejector 302 in response to a heater drive signal and a flow control valve configured to prevent or allow the flow of fluid (not shown) passing through the ejector 302 in response to an actuator drive signal, as discussed in further detail below. The actuator drive signal may be received at upper (e.g., solenoid) terminals 306 and the heater drive signal may be received at lower terminals 308.

[0022] As an example to implement the (flow) control valve, the ejector 302 preferably comprises a nozzle needle (or pintle) 310 reciprocally arranged within a body 301. The nozzle needle 310 has a tip 312 urged into a seat 314 at nozzle exit orifice 316 by nozzle spring 318. An accumulation volume 320 may be defined between the nozzle needle 310 and the body 301 of the ejector 302. The accumulation volume 320 may be filled, in use, via a top inlet 322 that is connected to the fluid delivery rail 108, that is in turn connected to receive pressurized fluid under the action of a pump (not shown). The nozzle needle 310 may form a solenoid operated valve under the action of coil 324; and when the latter is excited / energized by an actuator drive signal defining an actuation duration during which fluid flow is allowed in a current ejection operation, the nozzle needle 310 is moved, against spring bias, away from the seat 314 so as to eject a quantity of fluid. The configuration of ejector 302 is typically that of a gasoline fuel injector (namely concerning the nozzle configuration), except that it includes the addition heater 304.

[0023] Figure 4 is a schematic illustration of a control system 402 (or fluid delivery system) for use in techniques according to inventive embodiments disclosed herein.

[0024] According to the disclosed techniques, an agricultural spraying system 102 may comprise a vehicle (not shown in Fig. 4; see 104 in Fig. 1 PRIOR ART)) and, mounted thereto, the control system 402. The control system 402 comprises the fluid delivery rail 108 for supplying (e.g., multiple) ejectors 302, which may be as described with respect to Fig. 3 and may be incorporated in a spray unit (not shown in Fig. 4; see 110 in Fig. 1 - PRIOR ART). A delivery rail pressure sensor 404 is configured to output a delivery pressure signal indicative of the current pressure of the fluid in the fluid delivery rail 108.

[0025] The control system 402 further comprises a control unit 406 for controlling the spray unit(s), including the respective ejectors 302. The control unit 406 typically comprises processing circuitry (i.e. having a processor, a memory, and possibly controllers) configured to carry out the method herein disclosed. The control unit 406 may be coupled to the delivery rail pressure sensor 404. On the vehicle 104 (see Fig. 1) may be a reservoir 408 for the fluid (e.g., liquid such as a pesticide or growth-promoting agent) to be sprayed, and the fluid may be pumped to the fluid delivery rail 108 by the pump 410. In an embodiment, the control unit 406 outputs a pump drive signal to the pump 410 in order to pump the fluid at a flowrate corresponding to a magnitude of the pump drive signal, as discussed further below.

[0026] On the vehicle 104 and / or on the boom 106 (Fig. 1 (PRIOR ART)) may be provided a (vehicle) speed sensor 412 configured to output a speed signal indicative of the current speed of the vehicle 104, and the control unit 406 may be coupled to the speed sensor 412. In embodiment, a pressure control device (such as pressure control valve 420) is coupled to the control unit 406 and disposed so as to be in fluid communication with the interior of the fluid delivery rail 108, and the pressure control device is configured to set the pressure of fluid within the fluid delivery rail 108 in dependence upon a rail pressure control signal on line 422, as discussed further hereinbelow. The pressure control valve 420 may take the form of a pressure relief valve having a return line 424 to the reservoir 408. In other embodiments, a variable / selectable pressure control valve 420, or other means to vary the pressure of fluid within the fluid delivery rail 108, may be employed.

[0027] In addition, one or more auxiliary sensors 414 may be provided, each configured to output a respective auxiliary sensor signal corresponding to a target vegetative item (not shown) to be sprayed. As discussed below, in embodiments, the auxiliary sensors 414 may include one or more of a camera, a laser scanner, a GPS device, etc.

[0028] Figure 5 is a flowchart of a method for controlling a spray unit of an agricultural spraying system 102 using techniques according to embodiments disclosed herein. Figure 6 is a schematic diagram of a control unit 406 according to embodiments disclosed herein, for use in the control system of Fig. 4.

[0029] It will be appreciated that the techniques of Figs 5 and 6 may be implemented by hardware, software, or a combination thereof. It will further be appreciated that such techniques may be implemented on a remote server to which the control unit 406 is coupled via cellular or other wireless communications means. In Fig. 6, the components (e.g., of software) are presented as functional blocks. Where appropriate herein, reference to a “signal” may be a reference to an input or output line of a functional block, unit or sensor in Fig. 6. In embodiments, where appropriate, transformations, models and / or equations are stored in memory (not shown) of the control unit 406.

[0030] Referring to Fig. 5, the method (e.g., implemented on control unit 406) commences with receiving (step s502) the current delivery pressure signal output by the pressure sensor 404 (Fig. 4). Next, the auxiliary sensor signal(s) from the auxiliary sensor(s) are received (step s504). It will be appreciated that steps s502 and s504 may be performed concurrently I simultaneously, or in the reverse order.

[0031] Then, the method comprises deriving / determining (step s506), based on the current delivery pressure signal and one or more of the auxiliary sensor signals, and using one or more predetermined transformations, (i) a current heater drive signal (H1-Hx; see Fig. 6) defining a heating amount for a current ejection operation and (ii) a current actuator drive signal (S1-Sx; see Fig. 6) defining an actuation duration during which fluid flow is allowed in the current ejection operation.

[0032] The spray droplet size and spray temperature of the ejected fluid (fluid) are controlled by varying fluid temperature, and optionally by ejection pressure (i.e., the pressure of the fluid supplied to the ejector 302 for ejection). The quantity of fluid sprayed onto the crop is controlled through the opening time (actuation duration) of the ejector 302.

[0033] Increasing the inlet pressure leads to an increase in hydraulic atomization of the fluid upon exiting the nozzle orifice 316 of the ejector 302 (Fig. 3), reducing spray droplet size and reducing spray travel (penetration). The normal pressure variation for this type of ejector 302 is 2 to 8 bar. Spraying plants at 10 - 20 cm distance does not lead to damage at these pressure levels.

[0034] Increasing the temperature of the fluid leads to a reduction in viscosity of the fluid, improving the break-up of the fluid upon exiting the nozzle orifice 316 of the ejector 302 (Fig. 3), which also has the effect of reducing spray droplet size. The fluid temperature should not exceed a certain value, e.g. lying in the range 40-50°C, when impacting the plant. Above this temperature, plant cells may be damaged. There may be conditions (for example during morning frost) in which the heating of the fluid is used to transfer heat to the crop.

[0035] In an embodiment, the control unit 406 is configured to receive a vehicle speed signal 602 (e.g., from speed sensor 412; see Fig. 4) indicative of the current speed to the agricultural spraying system 102. Referring to Fig. 6, in this embodiment, deriving / determining the current heater drive signal (H1-Hx) and the current actuator drive signal (S1-Sx) comprises: (i) receiving a heater state target signal 604 and an actuator control state target signal 606 each dependent upon a first subset (608,610) of the one or more of the transformations, (ii) receiving the vehicle speed signal, (iii) deriving, using a timer unit 612, a heater timing control signal 614 and an actuator timing control signal 614, and sending (applying) the heater timing control signal 614 and the actuator timing control signal 614 to one or more drivers 616, for generating the current heater drive signal (H1-Hx) and the current actuator drive signal (S1-Sx). The timing and duration of the ejection operation(s) may thus be precisely controlled. In particular, the system is configured to cause an ejection operation at the target vegetative item (having an associated exact physical location) with the desired properties (such as spray shape, fluid temperature at a pressure, and / or fluid quantity). As the spraying vehicle 104 is moving and as the target vegetative item is at a particular location, the heating must start at or ahead of the ejection operation. The ejection operation must start before or as the spray unit 110 is closest or appropriate distance to the target vegetative item. The timer unit 612 is configured to ensure that the various operations (heating operation and ejection operation) are timed optimally to deliver the desired properties at the target vegetative item’s location.

[0036] As used herein, “target” in “target signal”, in respect of a variable such as fluid temperature or fluid quantity, means a signal indicative required or desired amount according to a respective transformation, such as a model or set of equations. As used herein, “fluid characteristics” are for example the density, viscosity and specific heat of the fluid. These properties influence the heating duration and / or actuation duration.

[0037] In an embodiment, the first subset of the one or more of the transformations comprises a combined injection control model (608,610). In this embodiment, deriving the current heater drive signal (H1-Hx) and the current actuator drive signal (S1-Sx) further comprises: (i) receiving a fluid temperature target signal 618 and a fluid quantity target signal 620 each dependent upon a second subset 622 of the one or more of the transformations, (ii) receiving the current delivery pressure signal 624, (iii) receiving a fluid characteristics signal 626 defining one or more physical characteristics of the fluid in the fluid delivery rail (e.g. from storage / interface 627), (iv) generating, based upon the fluid temperature target signal 618, the fluid quantity target signal 620, the current delivery pressure signal 624 and the fluid characteristics signal 626, and using the combined injection control model (608,610), the heater state target signal 604 and the actuator control state target signal 606, and (v) sending the heater state target signal 604 and an actuator control state target signal 606 to the timer unit 612.

[0038] In an embodiment, the combined injection control model (608,610) comprises (a) a pre-stored first plurality of tables, the first plurality of tables providing a mapping, based upon calibrated data, between (i) fluid temperature target signal 618, fluid quantity target signal 620, current delivery pressure signal 624 and the fluid characteristics signal 626 and (ii) heater state target signal 604 and actuator control state target signal 606, or (b) a predetermined first plurality of equations, the first plurality of equations taking as variables fluid temperature target, fluid quantity target, current delivery pressure and fluid characteristics, and having as outputs the values of the heater state target signal 604 and the actuator control state target signal 606.

[0039] In another embodiment, the first subset of the one or more of the transformations comprises an injector / heater thermal model 608 and an injector flow model 610. In this embodiment, deriving the current heater drive signal (H1-Hx) and the current actuator drive signal (S1-Sx) further comprises: (i) receiving a fluid temperature target signal 618 and a fluid quantity target signal 620 each dependent upon a second subset 622 of the one or more of the transformations, (ii) receiving the current delivery pressure signal 624 and a fluid characteristics signal 626 defining one or more physical characteristics of the fluid in the supply rail 108, (iii) generating, based upon the fluid temperature target signal 618, the fluid quantity target signal 620, the current delivery pressure signal 624 and the fluid characteristics signal 626, and using the injector / heater thermal model 608, the heater state target signal 604, (iv) generating, based upon fluid quantity target signal 620, the current delivery pressure signal 624 and the fluid characteristics signal 626, and using the injector flow model 610, the actuator control state target signal 606, and (v) sending the heater state target signal 604 and the actuator control state target signal 606 to the timer unit 612.

[0040] In an embodiment, the injector / heater thermal model 608 comprises (a) a pre-stored second plurality of tables, the second plurality of tables providing a mapping, based upon empirical / calibrate data, between (i) fluid temperature target signal 618, fluid quantity target signal 620, current delivery pressure signal 624 and the fluid characteristics signal 626 and (ii) the heater state target signal 604, or (b) a predetermined second plurality of equations, the second plurality of equations taking as variables fluid temperature target, fluid quantity target, current delivery pressure and fluid characteristics, and having as outputs the value of the heater state target signal 604.

[0041] In an embodiment, the injector flow model 610 comprises (a) a pre-stored third plurality of tables, the third plurality of tables providing a mapping, based upon empirical / calibrate data, between (i) fluid temperature target signal 618, fluid quantity target signal 620, current delivery pressure signal 624 and the fluid characteristics signal 626 and (ii) the actuator control state target signal 606, or (b) a predetermined third plurality of equations, the third plurality of equations taking as variables fluid temperature target, fluid quantity target, current delivery pressure and fluid characteristics, and having as outputs the value of the actuator control state target signal 606.

[0042] In embodiments involving the second subset of the one or more of the transformations, the second subset comprises a quantity I spray model 622. In this embodiment, deriving the current heater drive signal (H1-Hx) and the current actuator drive signal (S1-Sx) further comprises: (i) in response to receiving the auxiliary sensor signal 628, 630 from the auxiliary sensor(s) 414 and the current delivery pressure signal 624, deriving the fluid temperature target signal 618 and the fluid quantity target signal 620 using the quantity I spray model 622.

[0043] In an embodiment, the auxiliary sensors 414 comprises an imaging device 632 configured to output a captured image of the target vegetative item (not shown) to be sprayed and the quantity I spray model 622 comprises an image recognition module (not shown). In this embodiment, in a case where the captured image is matched to first predetermined target data using the image recognition module, the fluid temperature target signal 618 and the fluid quantity target signal 620 may be derived based upon the first predetermined target data. For example, the first predetermined target data may comprise an image template, and a fluid temperature target signal and a fluid quantity target signal may be associated with the image template in a memory (e.g. in a lookup table) of the control unit 406.

[0044] In an embodiment, the imaging device 632 comprises a camera configured to be mounted on the fluid delivery rail 108 (Fig. 1 (PRIOR ART)) or on a vehicle (104) of the agricultural spraying system (102) to which the spray unit is mounted. In this embodiment, the method may include (i) capturing one or more successive ones of the images using the camera and (ii) optionally storing each captured image in association with first identifying data and / or storing key features of each captured image. The first identifying data may be a position associated with a respective captured image. The key features may be numerical values, obtained through image processing of the captured images, and indicative of, e.g., amount of disease.

[0045] In an embodiment, the auxiliary sensors 414 comprise a positioning device 634 configured to output a current position 630 corresponding to the target vegetative item (not shown) to be sprayed. In this embodiment, the quantity I spray model 622 comprises a target position mapping module (not shown) and, in a case where the current position 630 is matched to second predetermined target data using the target position mapping module, the fluid temperature signal 618 and the fluid quantity signal 620 are derived based upon the second predetermined target data. (For example, the second predetermined target data may comprise a predetermined position, and a fluid temperature target and a fluid quantity target signal may be associated with the predetermined position in a memory (e.g. in a lookup table) of the control unit 406.) In this embodiment, the positioning device 634 may comprise a GNSS-based positioning device, preferably a GPS device, configured to be mounted on the fluid delivery rail 108 or on a vehicle 104 (Fig. 1) of the agricultural spraying system 102 to which the spray unit is mounted. In this embodiment, the method may comprise (i) capturing one or more successive ones of the current position 630 corresponding to the target vegetative item to be sprayed and (ii) optionally storing each current position 630 in association with second identifying data, such as date, operation number, type of fluid sprayed, type of vegetative item sprayed and / or spray parameters. In this embodiment, method may comprise storing each captured image, and the first identifying data includes the current position 630 output by the positioning device 634 at the time that the respective image of the target vegetative item (not shown) was captured.

[0046] Returning to Fig. 5, after step s506, the ejector is operated to perform an ejection operation, based on the derived / determined signals. Accordingly, operating the ejector based on the current heater drive signal may comprise sending / applying the current heater drive signal to the heater; and operating the flow control valve of the ejector based on the current actuator drive signal may comprise sending / applying the current actuator drive signal to the flow control valve. For example, the method proceeds with sending (step s508) the current heater drive signal (H1-Hx; see Fig. 6) to the heater 304 of the ejector 302 (see Fig. 3). As seen in Fig. 5, after step s508, the method proceeds with sending (step s510) the current actuator drive signal (S1-Sx; see Fig. 6) to the control valve of the ejector 302 (see Fig. 3). It will be appreciated that steps s508 and s510 may be performed simultaneously or in a different order.

[0047] The ejector opening time (actuation duration) may be controlled dependent on the ejection pressure, measured with the pressure sensor 404 installed upstream of the ejector 302 and connected to the control unit 406 (see Fig. 4). One or more ejectors 302 may be fed through the rail 108 in which the pressure is measured with the pressure sensor 404. The ejector 302 and rail 108 may be fed with the pump 410 which may be connected to the control unit 406. The inlet of the pump 410 is connected to a reservoir 408 containing the fluid to be applied to the crop. This reservoir may also be connected to the control unit 406.

[0048] As seen in Fig. 6, in an embodiment, the control unit 406 includes a pump driver 640 configured to output a pump drive signal 642 to the pump 410 configured to pump the fluid at a flowrate corresponding to a magnitude of the pump drive signal 642. In this embodiment, the method further comprises deriving the pump drive signal 642 by (i) determining a pump control signal 644 dependent upon a third subset (646,652) of the one or more of the transformations and (ii) sending the pump control signal 644 to the pump driver 640, for generating the pump drive signal 642. In this embodiment, the third subset of the one or more of the transformations may comprise a pump flow model 646, and determining the pump control signal 644 may comprise (i) receiving a fluid quantity target signal 620 dependent upon the second subset of the one or more of the transformations, (ii) receiving a pressure demand signal 648, the pressure demand signal 648 being dependent upon (i) a fluid characteristics signal 626 defining one or more physical characteristics of the fluid in the supply rail 108 and (ii) a user input 650 (e.g. from user interface 660, for example defining a type and / or age or base date of the target vegetative item, and (iii) generating, based upon the fluid quantity target signal 620 and the pressure demand signal 648, and using the pump flow model 646, the pump control signal 644.

[0049] In an embodiment, the pump flow model 646 comprises (a) a pre-stored fourth plurality of tables, the fourth plurality of tables providing a mapping, based upon empirical / calibrated data, between (i) fluid quantity target signal 620 and pressure demand signal 648 and (ii) the pump control signal 644, or (b) a predetermined fourth plurality of equations, the fourth plurality of equations taking as variables fluid target quantity and pressure demand, and having as outputs the value of the pump control signal 644.

[0050] In an embodiment, the third subset (646, 652) of the one or more of the transformations comprises a pressure demand model 652. In this embodiment, determining the pump control signal 644 comprises (i) receiving a fluid characteristics signal 626 defining one or more physical characteristics of the fluid in the supply rail, (ii) receiving a user input 650 defining a type and / or age or base date of the target vegetative item (not shown), and (iii) generating the pressure demand signal 648 based upon the fluid characteristics signal 626 and the user input 650 defining the type and / or age or base date and using the pressure demand model 652. (The base date may be a planting date of the target vegetative item.) In an embodiment, the pressure demand model 652 comprises (a) a pre-stored fifth plurality of tables, the fifth plurality of tables providing a mapping, based upon empirical / calibrated data, between (i) fluid characteristics signal 626 and type and / or age or base date of the target vegetative item (not shown) and (ii) the pressure demand signal 648 or (b) a predetermined fifth plurality of equations, the fifth plurality of equations taking as variables fluid characteristics and type and / or age or base date of the target vegetative item, and having as outputs the value of the pressure demand signal 648.

[0051] As noted above, the agricultural spraying system may further comprise a pressure control device (see 420 in Fig. 4), coupled to the control unit 406 and disposed so as to be in fluid communication with the interior of the fluid delivery rail 108, wherein the pressure control device is configured to set the pressure of fluid within the fluid delivery rail 108 in dependence upon a rail pressure control signal (see Fig. 6).

[0052] More particularly, the ejection pressure may be set through the pressure control valve 420 (Fig. 4) which is controlled by the control unit 406. Alternatively, the injection pressure may be controlled through a control valve in the supply pump 410 which is controlled by the control unit 406. The inclusion of the pressure control device (valve 420), in addition to the pump flow model 646 (Fig. 6), provides closed loop pressure control using pressure measurement 404 and pressure demand 648. The fluid temperature is controlled through a heating system which may also be controlled by the control unit 406 or a dedicated heater control unit (not shown) which is linked to the control unit 406.

[0053] In the embodiment including the pressure control device, and referring to Fig. 6, the method further comprises (i) deriving, based on the current delivery pressure signal 624 and a fluid characteristics signal 626 indicative of characteristics of the fluid within the fluid delivery rail, and using one or more of the predetermined transformations, a current rail pressure control signal 662; and (ii) sending the current rail pressure control signal 662 to the pressure control device 420. In this embodiment, the current rail pressure control signal 662 may be derived dependent upon a fourth subset of the one or more of the transformations, the fourth subset of the one or more of the transformations comprising a pressure control model 661. In this embodiment, deriving the current rail pressure control signal 662 may comprise: (i) receiving the current delivery pressure signal 624; (ii) receiving the pressure demand signal 648, the pressure demand signal being dependent upon (i) the fluid characteristics signal 626 defining one or more physical characteristics of the fluid in the supply rail and optionally (ii) a user input 650 defining a type and / or age or base date of the target vegetative item; and (iii) generating, based upon at least the current delivery pressure signal 624 and the pressure demand signal 648, and using the pressure control model 661, the current rail pressure control signal 662.

[0054] In an embodiment, the pressure control model 661 comprises (a) a prestored sixth plurality of tables, the sixth plurality of tables providing a mapping, based upon empirical / calibrated data, between (i) current delivery pressure signal 624 and pressure demand signal 648 (not marked in fig 6) and (ii) the rail pressure control signal 662, or (b) a predetermined sixth plurality of equations, the sixth plurality of equations taking as variables delivery pressure and pressure demand, and having as outputs the value of the rail pressure control signal 662. In an embodiment, the pressure demand signal 648 is received as the output of the pressure demand model 652 described hereinabove.

[0055] Referring to Figs 1 and 4, the agricultural spraying system 102 may comprise a plurality of spray units mounted to the rail 108. In this embodiment, the method may comprise (i) deriving the current heater drive signal (H1-Hx; see Fig. 6) and current actuator drive signal (S1 -Sx; see Fig. 6) for each of the plurality of spray units and, for each of the plurality of spray units, (ii) sending the current heater drive signal (H1-Hx) to the heater 304 of the ejector 302 (see Fig. 3) of a respective spray unit and (iii) sending the current actuator drive signal (S1-Sx) to the control valve of the ejector 302 of a respective spray unit. In an embodiment, the current heater drive signal (H1-Hx) and the current actuator drive signal (S1-Sx) is different for different spray units. In another embodiment, the current heater drive signal (H1-Hx) and the current actuator drive signal (S1-Sx) is different for different subsets of the plurality of spray units. Each subset may comprise a plurality of spray units.

[0056] Thus, in accordance with the techniques disclosed herein, electronic control (e.g., using solenoid operated ejectors) enables critical spray parameters (spray droplet size, spray temperature and fluid quantity) to be controlled. These parameters may be controlled, with or without variation in time, independently per injector, independently for one or more groups of injectors or uniformly for all injectors.

[0057] Returning to Fig. 4, lower part, this illustrates how the disclosed techniques may be employed - for producing different spray patterns and ejection amounts with different spray parameters (spray droplet size, spray temperature and fluid quantity). The left part shows a spray pattern (highly directed) with heater drive signal H1 (no heating) and the actuator drive signal S1. The middle part shows a spray pattern (somewhat directed, somewhat atomized) with heater drive signal H2 (medium heating) and the actuator drive signal S2. The right part shows a spray pattern (significantly atomized) with heater drive signal H3 (high heating) and the actuator drive signal S3.

[0058] While embodiments have been described by reference to embodiments of survey devices having various components in their respective implementations, it will be appreciated that other embodiments make use of other combinations and permutations of these and other components. 19 07 24

Claims

1. A method carried out by processing circuitry, for controlling a spray unit of an agricultural spraying system, the agricultural spraying system including a fluid delivery rail for supplying the spray unit, a pressure sensor being configured to output a delivery pressure signal indicative of the current pressure of the fluid in the fluid delivery rail, the agricultural spraying system further including one or more auxiliary sensors each configured to output a respective auxiliary sensor signal corresponding to a target vegetative item to be sprayed, the spray unit comprising an ejector and being configured to perform one or more ejection operations in which a quantity of fluid is ejected by the ejector, the ejector having a heater configured to heat fluid passing through the ejector in response to a heater drive signal and a flow control valve configured to prevent or allow the flow of fluid passing through the ejector in response to an actuator drive signal, the method comprising:receiving the current delivery pressure signal output by the pressure sensor;receiving the auxiliary sensor signal(s) from the or each auxiliary sensor, wherein (i) the one or more auxiliary sensors comprise an imaging device and the auxiliary sensor signal(s) comprise a captured image of the target vegetative item or (ii) the one or more auxiliary sensors comprise a positioning device and the auxiliary sensor signal(s) comprise a current position corresponding to the target vegetative item;deriving, based on the current delivery pressure signal and one or more of the auxiliary sensor signals, and using one or more predetermined transformations, (i) a current heater drive signal defining a heating amount for a current ejection operation and (ii) a current actuator drive signal defining an actuation duration during which fluid flow is allowed in the current ejection operation; andoperating the heater of the ejector based on the current heater drive signal; andoperating the flow control valve of the ejector based on the current actuator drive signal.19 07 242. The method of claim 1, wherein the agricultural spraying system further comprises a pressure control device, coupled to the processing circuitry and disposed so as to be in fluid communication with the interior of the fluid delivery rail, wherein the pressure control device is configured to set the pressure of fluid within the fluid delivery rail in dependence upon a rail pressure control signal; wherein the method further comprisesderiving, based on the current delivery pressure signal and a fluid characteristics signal indicative of characteristics of the fluid within the fluid delivery rail, and using one or more of the predetermined transformations, a current rail pressure control signal; andsending the current rail pressure control signal to the pressure control device.

3. The method of claim 1 or 2, wherein the processing circuitry is configured to receive a vehicle speed signal indicative of the current speed to the agricultural spraying system, and wherein deriving the current heater drive signal and the current actuator drive signal comprises:receiving a heater state target signal and an actuator control state target signal each dependent upon a first subset of the one or more of the transformations;receiving the vehicle speed signal;deriving, using a timer unit, a heater timing control signal and an actuator timing control signal; andsending the heater timing control signal and an actuator timing control signal to one or more drivers, for generating the current heater drive signal and the current actuator drive signal.

4. The method of claim 3, wherein the first subset of the one or more of the transformations comprises a combined injection control model, deriving the current heater drive signal and the current actuator drive signal comprises:receiving a fluid temperature target signal and a fluid quantity target signal each dependent upon a second subset of the one or more of the transformations;19 07 24receiving the current delivery pressure signal;receiving a fluid characteristics signal defining one or more physical characteristics of the fluid in the fluid delivery rail;generating, based upon the fluid temperature target signal, the fluid quantity target signal, the current delivery pressure signal and the fluid characteristics signal, and using the combined injection control model, the heater state target signal and the actuator control state target signal; andsending the heater state target signal and an actuator control state target signal to the timer unit.

5. The method of claim 4, wherein the combined injection control model comprises (a) a pre-stored first plurality of tables, the first plurality of tables providing a mapping, based upon empirical data, between (i) fluid temperature target signal, fluid quantity target signal, current delivery pressure signal and fluid characteristics signal and (ii) heater state target signal and actuator control state target signal, or (b) a predetermined first plurality of equations, the first plurality of equations taking as variables fluid temperature target, fluid quantity target, current delivery pressure and fluid characteristics, and having as outputs the values of the heater state target signal and the actuator control state target signal.

6. The method of claim 3, wherein the first subset of the one or more of the transformations comprises an injector / heater thermal model and an injector flow model, the method further comprising:receiving a fluid temperature target signal and a fluid quantity target signal each dependent upon a second subset of the one or more of the transformations;receiving the current delivery pressure signal and a fluid characteristics signal defining one or more physical characteristics of the fluid in the fluid delivery rail;generating, based upon the fluid temperature target signal, the fluid quantity target signal, the current delivery pressure signal and the fluid characteristics signal, and using the injector / heater thermal model, the heater state target signal;19 07 24generating, based upon fluid quantity target signal, the current delivery pressure signal and the fluid characteristics signal, and using the injector flow model, the actuator control state target signal; andsending the heater state target signal and the actuator control state target signal to the timer unit.

7. The method of claim 6, wherein the injector / heater thermal model comprises (a) a pre-stored second plurality of tables, the second plurality of tables providing a mapping, based upon empirical data, between (i) fluid temperature target signal, fluid quantity target signal, current delivery pressure signal and fluid characteristics signal and (ii) the heater state target signal, or (b) a predetermined second plurality of equations, the second plurality of equations taking as variables fluid temperature target, fluid quantity target, current delivery pressure and fluid characteristics, and having as outputs the value of the heater state target signal.

8. The method of claim 6 or 7, wherein the injector flow model comprises (a) a pre-stored third plurality of tables, the third plurality of tables providing a mapping, based upon empirical data, between (i) fluid temperature target signal, fluid quantity target signal, current delivery pressure signal and fluid characteristics signal and (ii) the actuator control state target signal, or (b) a predetermined third plurality of equations, the third plurality of equations taking as variables fluid temperature target, fluid quantity target, current delivery pressure and fluid characteristics, and having as outputs the value of the actuator control state target signal.

9. The method of claim 4, or any claim dependent thereon, wherein the second subset of the one or more of the transformations comprises a quantity I spray model, and wherein the method comprises:in response to receiving the auxiliary sensor signal from the or each auxiliary sensor and the current delivery pressure signal, deriving the fluid temperature target signal and the fluid quantity target signal using the quantity I spray model.19 07 2410. The method of claim 9, wherein the one or more auxiliary sensors comprises an imaging device configured to output a captured image of the target vegetative item to be sprayed and the quantity I spray model comprises an image recognition module, wherein:in a case where the captured image is matched to first predetermined target data using the image recognition module, the fluid temperature target signal and the fluid quantity target signal are derived based upon the first predetermined target data.

11. The method of claim 10, wherein the imaging device comprises a camera configured to be mounted on the fluid delivery rail or on a vehicle of the agricultural spraying system to which the spray unit is mounted, and wherein the method comprises (i) capturing one or more successive ones of the images using the camera and (ii) optionally storing each captured image in association with first identifying data and I or storing key features of the images.

12. The method of claim 9, 10 or 11, wherein the one or more auxiliary sensors comprises a positioning device configured to output a current position corresponding to the target vegetative item to be sprayed and the quantity I spray model comprises a target position mapping module, wherein:in a case where the current position is matched to second predetermined target data using the target position mapping module, the fluid temperature target signal and the fluid quantity target signal are derived based upon the second predetermined target data.

13. The method of claim 12, wherein the positioning device comprises a GNSS-based positioning device, preferably a GPS device, configured to be mounted on the fluid delivery rail or on a vehicle of the agricultural spraying system to which the spray unit is mounted, and wherein the method comprises (i) capturing one or more successive ones of the current position corresponding to the target vegetative item to be sprayed and (ii) optionally storing each current position in association with second identifying data.19 07 2414. The method of claim 13, when dependent upon claim 10, wherein the method comprises storing each captured image, and the first identifying data includes the current position output by the positioning device at the time that the respective image of the target vegetative item was captured.

15. The method of any of the preceding claims, wherein the processing circuitry includes a pump driver configured to output a pump drive signal to a pump configured to pump the fluid at a flowrate corresponding to a magnitude of the pump drive signal; and wherein the method further comprises:deriving the pump drive signal by (i) determining a pump pressure control signal dependent upon a third subset of the one or more of the transformations and (ii) sending the pump control signal to the pump driver, for generating the pump drive signal.

16. The method of claim 15, wherein the third subset of the one or more of the transformations comprises a pump flow model, and determining the pump control signal comprises:receiving a fluid quantity target signal dependent upon the second subset of the one or more of the transformations;receiving a pressure demand signal, the pressure demand signal being dependent upon (i) a fluid characteristics signal defining one or more physical characteristics of the fluid in the supply rail and optionally (ii) a user input, for example defining a type and / or age or base date of the target vegetative item;generating, based upon the fluid quantity target signal and the pressure demand signal, and using the pump flow model, the pump control signal.

17. The method of claim 16, wherein the pump flow model comprises (a) a pre-stored fourth plurality of tables, the fourth plurality of tables providing a mapping, based upon empirical data, between (i) fluid quantity target signal and pressure demand signal and (ii) the pump control signal, or (b) a predetermined fourth plurality of equations, the fourth plurality of equations taking as variables fluid quantity target and pressure demand, and having as outputs the value of the pump control signal.19 07 2418. The method of any of claims 15 to 17, wherein the third subset of the one or more of the transformations comprises a pressure demand model, and determining the pump control signal comprises:receiving a fluid characteristics signal defining one or more physical characteristics of the fluid in the supply rail; andreceiving a user input defining a type and / or age or base date of the target vegetative item; andgenerating the pressure demand signal based upon the fluid characteristics signal and the user input defining the type and / or age or base date and using the pressure demand model.

19. The method of claim 18, wherein the pressure demand model comprises (a) a pre-stored fifth plurality of tables, the fifth plurality of tables providing a mapping, based upon empirical data, between (i) fluid characteristics signal and type and / or age or base date of the target vegetative item and (ii) the pressure demand signal or (b) a predetermined fifth plurality of equations, the fifth plurality of equations taking as variables fluid characteristics and type and / or age or base date of the target vegetative item, and having as outputs the value of the pressure demand signal.

20. The method of claim 2, or any claim dependent thereon, wherein the current rail pressure control signal is derived dependent upon a fourth subset of the one or more of the transformations, the fourth subset of the one or more of the transformations comprising a pressure control model, and deriving the current rail pressure control signal comprises:receiving the current delivery pressure signal;receiving a pressure demand signal, the pressure demand signal being dependent upon (i) a fluid characteristics signal defining one or more physical characteristics of the fluid in the supply rail and optionally (ii) a user input defining a type and / or age or base date of the target vegetative item; and19 07 24generating, based upon at least the current delivery pressure signal and the pressure demand signal, and using the pressure control model, the current rail pressure control signal.

21. The method of claim 20, wherein the pressure control model comprises (a) a pre-stored sixth plurality of tables, the sixth plurality of tables providing a mapping, based upon empirical data, between (i) current delivery pressure signal and pressure demand signal and (ii) the rail pressure control signal, or (b) a predetermined sixth plurality of equations, the sixth plurality of equations taking as variables delivery pressure and pressure demand, and having as outputs the value of the rail pressure control signal.

22. The method of claim 20 or 21, when dependent upon claim 18 or 19, wherein the pressure demand signal is received as the output of the pressure demand model.

23. The method of any of the preceding claims, wherein the agricultural spraying system comprises a plurality of spray units mounted to the rail; and wherein the method comprises:deriving the current heater drive signal and current actuator drive signal for each of the plurality of spray units; and, for each of the plurality of spray units sending the current heater drive signal to the heater of the ejector of a respective spray unit; andsending the current actuator drive signal to the flow control valve of the ejector of a respective spray unit.

24. The method of claim 23, wherein (i) the current heater drive signal and the current actuator drive signal is different for different spray units or (ii) the current heater drive signal and the current actuator drive signal is different for different subsets of the plurality of spray units.19 07 2425. A control unit, for controlling a spray unit of an agricultural spraying system, the control unit comprising the processing circuitry configured to carry out the method of any of the preceding claims.

26. An agricultural spraying system comprising:a vehicle and, mounted thereto, a fluid delivery rail for supplying a spray unit, a delivery rail pressure sensor being configured to output a delivery pressure signal indicative of the current pressure of the fluid in the fluid delivery rail, one or more spray unit being mounted to and supplied by the rail;one or more auxiliary sensors each configured to output a respective auxiliary sensor signal corresponding to a target vegetative item to be sprayed,wherein (i) the one or more auxiliary sensors comprise an imaging device configured to output a captured image of the target vegetative item or (ii) the one or more auxiliary sensors comprise a positioning device configured to output a current position corresponding to the target vegetative item,wherein the or each spray unit comprises an ejector having a heater configured to heat fluid passing through the ejector in response to a heater drive signal and a flow control valve configured to control the flow of fluid passing through the ejector in response to an actuator drive signal; and, the agricultural spraying system further comprisesthe control unit of claim 25 for controlling the or each spray unit.

27. A computer program product comprising instructions which, when executed by processing circuitry, cause the method of any of claims 1 to 24 to be performed.

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