Work vehicle, motor control method, and computer program

Abstract

A work vehicle according to the present invention is an electric work vehicle to which can be attached a work machine for performing application work including crop spraying, fertilization, and seeding, the work vehicle comprising: a PTO shaft that supplies motive power to the work machine; an electric motor that has an output shaft directly or indirectly connecting to the PTO shaft; and a control device that controls the electric motor. The control device determines a target motor rotation speed on the basis of a target application amount and controls the application amount of the application work by changing the rotation speed of the electric motor in accordance with the target motor rotation speed.

Description

Work vehicle, motor control method, and computer program

[0001] The present disclosure relates to a work vehicle, a motor control method, and a computer program.

[0002] In the field of automobiles whose main purpose is to move people or objects, electric vehicles (EVs) that generate driving force (traction) for driving by an electric motor (hereinafter sometimes simply referred to as "motor") instead of an internal combustion engine are becoming popular.

[0003] On the other hand, in order to realize a decarbonized society, it is required to reduce the amount of carbon dioxide (CO ２ ) emitted by work vehicles such as tractors used in fields. Different from general automobiles, work vehicles such as tractors need to tow a work implement (agricultural implement) to perform agricultural work such as tilling. Therefore, in order to realize the electrification of work vehicles, there are problems to be solved that are different from the electrification of passenger cars.

[0004] Patent Document 1 discloses an electric tractor that distributes and supplies electric power from a battery to a plurality of electric motors. The electric tractor includes a hydraulic pump, a pump motor, a PTO motor, a traveling motor, a battery, and an electric drive controller. The pump motor is an electric motor that drives the hydraulic pump. The PTO motor is an electric motor that drives the PTO shaft. The traveling motor is an electric motor that drives to make the traveling body travel. The battery supplies electric power to the pump motor, the PTO motor, and the traveling motor. The electric drive controller controls the distribution of electric power to the pump motor, the PTO motor, and the traveling motor.

[0005] Japanese Patent Application Laid-Open No. 2023-66721

[0006] In a conventional work vehicle equipped with an internal combustion engine, consumption of fossil fuels and emission of greenhouse gases are inevitable. On the other hand, in an electric work vehicle, various problems to be solved such as ensuring safety, improving running performance, reducing environmental impact, improving convenience, or reducing costs remain.

[0007] This disclosure provides an electric work vehicle capable of solving at least one of these problems.

[0008] This disclosure provides solutions as described in the following items.

[0009] [Item 1] An electric work vehicle capable of being fitted with a work machine for performing application work including pesticide spraying, fertilization and sowing, comprising: a PTO shaft for supplying power to the work machine; an electric motor having an output shaft directly or indirectly connected to the PTO shaft; and a control device for controlling the electric motor, wherein the control device determines a target motor rotation speed based on a target application rate, and controls the application rate of the application work by changing the rotation speed of the electric motor according to the target motor rotation speed.

[0010] [Item 2] The work vehicle according to Item 1, wherein the control device determines the target rotational speed of the PTO shaft based on the target application rate, and determines the target motor rotational speed according to the target rotational speed of the PTO shaft.

[0011] [Item 3] The work vehicle according to Item 2, comprising a storage device that stores a table relating the target rotational speed of the PTO shaft and the target application rate, wherein the control device refers to the table and determines the target rotational speed of the PTO shaft based on the target application rate.

[0012] [Item 4] The work vehicle according to item 2 or 3, further comprising: a running gear including drive wheels; a positioning device for acquiring positional information of a work vehicle in a field, wherein the control device further determines a target rotational speed of the PTO shaft based on at least one of the ground speed of the work vehicle calculated based on data output from the positioning device, or the rotational speed of the drive wheels.

[0013] [Item 5] The work vehicle according to Item 4, wherein the control device determines the slip ratio of the work vehicle from the ground speed and the rotational speed of the drive wheels, and determines the target rotational speed of the PTO shaft based on the target application rate and the slip ratio.

[0014] [Item 6] The work vehicle according to item 4 or 5, wherein the electric motor is a first electric motor and is equipped with a second electric motor that drives the traveling device.

[0015] [Item 7] A work vehicle according to any one of items 1 to 6, comprising a communication device for communicating with a server, wherein the communication device receives application work plan data including information on the target application amount transmitted from the server, and the control device receives the application work plan data output from the communication device and obtains the target application amount from the application work plan data.

[0016] [Item 8] The work vehicle according to Item 7, wherein the application work plan includes information on target application rates associated with each of a plurality of work areas included in one or more fields, and the control device determines a target rotational speed of the PTO shaft for each corresponding work area among the plurality of work areas based on the target application rates associated with each of the plurality of work areas.

[0017] [Item 9] The work vehicle according to Item 1, wherein the control device includes one or more processors and one or more memories that store programs for controlling the operation of the one or more processors, and the one or more processors execute a process to control the amount of application work by determining a target motor rotation speed based on the target application amount according to the program and changing the rotation speed of the electric motor according to the target motor rotation speed.

[0018] [Item 10] A motor control method executed by a computer for use in a work vehicle equipped with a PTO shaft that supplies power to a work machine that performs application work including pesticide spraying, fertilization and sowing, and an electric motor having an output shaft directly or indirectly connected to the PTO shaft, the motor control method comprising: determining a target motor rotation speed based on a target application rate; and controlling the application rate of the application work by changing the rotation speed of the electric motor in accordance with the target motor rotation speed.

[0019] [Item 11] A computer program used for motor control of a work vehicle comprising a PTO shaft that supplies power to a work machine that performs application work including pesticide spraying, fertilization, and sowing, and an electric motor having an output shaft directly or indirectly connected to the PTO shaft, wherein the computer causes the computer to perform the following: determine a target motor rotation speed based on a target application rate, and control the application rate of the application work by changing the rotation speed of the electric motor in accordance with the target motor rotation speed.

[0020] [Item 12] A control device configured to perform the method described in Item 10.

[0021] [Item 13] A computer-readable non-temporary storage medium that stores a computer program containing instructions for causing a computer to perform the method described in Item 10.

[0022] [Item 14] A system comprising the control device described in Item 12, and an electric motor.

[0023] [Item 15] A control device for controlling an electric motor mounted on an electric work vehicle, which is connected to a work machine that performs application work including pesticide spraying, fertilization and sowing, and which is equipped with a PTO shaft that supplies power to the work machine, wherein the electric motor has an output shaft that is directly or indirectly connected to the PTO shaft, and the control device includes: a determination means for determining a target motor rotation speed based on a target application rate, and a processing means for performing a process to control the application rate of the application work by changing the rotation speed of the electric motor in accordance with the target motor rotation speed.

[0024] [Item 16] A system comprising the control device described in Item 15, and an electric motor.

[0025] Comprehensive or specific embodiments of the present invention may be realized by apparatus, systems, methods, integrated circuits, computer programs, or computer-readable non-temporary storage media, or any combination thereof. The computer-readable storage media may include volatile storage media or non-volatile storage media. The apparatus may consist of multiple devices. If the apparatus consists of two or more devices, these two or more devices may be located in a single device or in two or more separate devices.

[0026] According to embodiments of the present disclosure, an electric work vehicle is provided that can change the application rate in application work, including fertilization and sowing.

[0027] This is a schematic plan view showing an example of the basic configuration of a work vehicle according to an exemplary embodiment of the present invention. This is a side view of a work vehicle according to an exemplary embodiment of the present invention. This is a top view of a work vehicle according to an exemplary embodiment of the present invention. This is a block diagram showing an example of the main components of a work vehicle and their connection relationships. This is a block diagram showing an example of the configuration of a power converter and its connection to other equipment. This is a block diagram showing an example of the hardware configuration of each ECU. This is a block diagram showing an example of the configuration of a power distribution unit. This is a flowchart showing an example of a motor control procedure for controlling the amount of fertilizer applied by the rotation speed of the PTO shaft. This is a schematic diagram showing an example of the connection between a work vehicle and an external server. This is a flowchart showing the procedure for determining the target motor rotation speed according to the first implementation example. This is a flowchart showing the procedure for determining the target motor rotation speed according to the second implementation example. This is a flowchart showing the procedure for determining the target motor rotation speed according to the third implementation example. This is a schematic diagram showing a work vehicle performing fertilizer application work in a field containing two work areas.

[0028] Embodiments of the present invention will be described below. However, unnecessarily detailed descriptions may be omitted. For example, detailed descriptions of already well-known matters and redundant descriptions of substantially identical configurations may be omitted. This is to avoid the following description becoming unnecessarily verbose and to facilitate understanding for those skilled in the art. The inventors provide the accompanying drawings and the following description so that those skilled in the art can fully understand the present invention, and not to limit the subject matter described in the claims. In the following description, components having the same or similar function are denoted by the same reference numerals.

[0029] The following embodiments are illustrative examples for realizing the technical concept of the present invention, and the present invention is not limited to these embodiments. For example, the numerical values, shapes, materials, steps, and order of steps shown in the following embodiments are merely examples, and various modifications are possible as long as they do not create a technical inconsistency. Furthermore, it is possible to combine one embodiment with other embodiments. The size and positional relationships of the components shown in each drawing may be exaggerated for ease of understanding.

[0030] (Definition of Terms) In this specification, “work vehicle” means a vehicle used for a specific task, such as agricultural work or construction work. “Work” may be, for example, agricultural work, construction work, rubble removal work, or snow removal work. Agricultural work vehicles may be, for example, tractors, combine harvesters, rice transplanters, riding cultivators, vegetable transplanters, vegetable harvesters, mowers, seeders, fertilizer spreaders, sprayers, or broadcasters. Construction work vehicles may be, for example, backhoes, wheel loaders, or carriers. An agricultural work vehicle such as a tractor or combine harvester, or a construction work vehicle, may function as a “work vehicle” on its own, or the work vehicle and any implements attached to or towed by it may function as a single “work vehicle.” Agricultural work vehicles perform agricultural tasks on the ground within a field (or work area), such as tilling, sowing, pest control, fertilizing, planting crops, or harvesting. Construction vehicles perform tasks such as transporting soil, rubble, and other materials at construction sites. These tasks are sometimes referred to as "ground work" or simply "work." When a construction vehicle moves while performing work, it is sometimes referred to as "work driving."

[0031] An "electric work vehicle" refers to a work vehicle that runs using an electric motor as its power source. An electric work vehicle may also be equipped with an internal combustion engine as an auxiliary power source in addition to the electric motor. Alternatively, an electric work vehicle may be equipped with an electric motor as an auxiliary power source in addition to the internal combustion engine. An electric work vehicle is equipped with an electrical energy source, such as a battery or fuel cell, to supply power to the electric motor. In the following description, an "electric work vehicle" may be simply referred to as a "work vehicle."

[0032] Electric motors can be synchronous motors such as permanent magnet synchronous motors or reluctance motors, or asynchronous motors such as induction motors.

[0033] A battery is an energy storage device that stores the electrical energy necessary for the operation of electric motors and other electrical components mounted on a work vehicle and / or work machine. A fuel cell is a power generation device that generates such electrical energy from a fuel such as hydrogen. An electrical energy source can be realized by an energy storage device, a power generation device, or a combination of an energy storage device and a power generation device. Furthermore, an electric work vehicle may obtain electrical energy from an electrical energy source located at a distance from the vehicle (e.g., on the ground or on another vehicle) via wired or wireless means.

[0034] When an electric work vehicle performs various "tasks" while moving or stationary, the power required for those tasks may be obtained from electric motors. An electric work vehicle is equipped with one or more electric motors. If an electric work vehicle is equipped with multiple electric motors, certain electric motors may output the driving force required for movement, while other electric motors may output the driving force required for the "tasks." If some or all of the "tasks" are performed by a work machine, the driving force can be mechanically transmitted from one or more electric motors on the electric work vehicle to the work machine. Such mechanical transmission of driving force can be achieved via a power transmission shaft called a power take-off (PTO) shaft.

[0035] The work machine itself may be equipped with an electric motor for the work. In this case, power may be supplied to the electric motor of the work machine from an electrical energy source such as a battery or fuel cell equipped in the electric work vehicle. The work machine may also be equipped with an electrical energy source that stores the power required for the work.

[0036] A "control device" (controller) is a device that controls the operation of part or all of a work vehicle. One example of a "control device" is a computing device comprising at least one processor and at least one memory that stores a computer program (code) that defines the control process executed by the processor. Another example of a "control device" is a computing device with a hardware accelerator such as an FPGA (Field-Programmable Gate Array), ASSP (Application Specific Standard Product), or ASIC (Application-Specific Integrated Circuit) configured or programmed to execute the control process. A control device may also be a collection of multiple devices. For example, several computing devices such as physically separated electronic control units (ECUs) may work together to function as a "control device".

[0037] A "processor" is a hardware electronic circuit such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), DSP (Digital Signal Processor), ISP (Image Signal Processor), or NPU (Neural Network Processing Unit).

[0038] "Memory" refers to hardware electronic circuits such as ROM (Read Only Memory) or RAM (Random Access Memory). Part of the memory may be a storage medium connected to the processor via wiring or a network. These hardware electronic circuits may be implemented by one or more integrated circuits (ICs) or large-scale integrated circuits (LSIs). Each functional unit or block and associated component within the electronic circuit may be manufactured individually as separate integrated circuit chips, or some or all of these functional units or blocks may be combined and manufactured as a single integrated circuit chip. Memory may store computer programs (hereinafter sometimes simply referred to as "programs") that define the operation of the processor. The programs are designed to cause the processor to perform one or more functions, operations, steps, or processes in embodiments of the present invention.

[0039] (Embodiments) Hereinafter, with reference to the drawings, several embodiments of the present invention applied to an electric agricultural tractor, which is an example of an electric work vehicle, will be described. The various technologies described for tractors in the following description can also be applied to agricultural machinery other than tractors, construction vehicles used at construction sites, work vehicles used at disaster sites, snowplows used in heavy snow areas, and vehicles for transporting goods, etc.

[0040] In the following explanation, the direction of arrow F in the diagram will be referred to as "forward," the direction of arrow B as "backward," the direction of arrow L as "left," the direction of arrow R as "right," the direction of arrow U as "up," and the direction of arrow D as "down."

[0041] <1. Basic Configuration of the Work Vehicle> Figure 1 is a schematic plan view showing an example of the basic configuration of a work vehicle 10 according to an exemplary embodiment of the present invention. The work vehicle 10 shown is an electric tractor for agricultural use. The work vehicle 10 can travel within a field while carrying or towing implements and performing agricultural work according to the type of implement. The work vehicle 10 can also travel within and outside of a field (including roads) with the implement lifted or without the implement attached.

[0042] The work vehicle 10 is equipped with a body (vehicle frame) 11 that rotatably supports the left and right front wheels 14F and the left and right rear wheels 14R. The body 11 includes a front frame 12 on which the front wheels 14F are mounted and a transmission case 13 on which the rear wheels 14R are mounted. The front frame 12 is fixed to the front of the transmission case 13. The front wheels 14F and the rear wheels 14R may be collectively referred to as "wheels 14". Strictly speaking, wheels 14 are wheels, and tires are mounted on the wheels 14. In this disclosure, "wheels" generally means the entire "wheel and tire". One or both of the front wheels 14F and the rear wheels 14R may be replaced with a plurality of wheels (crawlers) equipped with a track instead of wheels with tires.

[0043] The work vehicle 10 in the example shown in Figure 1 is equipped with a battery 20 and an electric motor 30 (hereinafter simply referred to as "motor 30") which are directly or indirectly supported by the front frame 12. The battery 20 may be configured as a battery pack including, for example, multiple cells connected in series. The battery 20 is a rechargeable battery that outputs a relatively high voltage, such as a lithium-ion battery or an all-solid-state battery. The battery 20 stores power to drive the motor 30. The battery 20 may be housed in a front housing, for example, called a "bonnet." The front housing is supported by the front frame 12 located at the front of the vehicle body 11.

[0044] Motor 30 is electrically connected to battery 20. Motor 30 can convert the electric power output from battery 20 into mechanical motion (power) to generate the driving force (traction) necessary for the running of work vehicle 10. Motor 30 can be, for example, an AC synchronous motor. Battery 20 generates a direct current. Therefore, when motor 30 is an AC synchronous motor, an electric circuit group including an inverter device (hereinafter, may be simply referred to as "inverter") may be provided between battery 20 and motor 30. The direct current is converted into an alternating current by the inverter device. A part of such an electric circuit group may be inside battery 20. Also, another part of the electric circuit group may be attached to motor 30 as a drive circuit of motor 30.

[0045] Motor 30 has a rotating output shaft 33. The torque of output shaft 33 is transmitted to rear wheel 14R through mechanical components such as a transmission (speed change device) provided inside transmission case 13 and a rear wheel differential device (differential gear device). In other words, the power generated by motor 30, which is a power source, is transmitted to rear wheel 14R by a power transmission system (drive train) 34 including a transmission provided inside transmission case 13. For this reason, the "transmission case" may be called the "mission case". In the four-wheel drive mode, a part of the power of motor 30 is also transmitted to front wheel 14F. Thus, motor 30 drives a running device including a plurality of wheels 14.

[0046] The power of motor 30 may be used not only for the running of work vehicle 10 but also for driving a work implement. A PTO shaft 40 is provided at the rear end of transmission case 13. A work implement can be connected to PTO shaft 40. PTO shaft 40 can be driven by motor 30 that drives the running device or another electric motor not shown in FIG. 1. The torque of output shaft 33 of motor 30 or the output shaft of another motor is transmitted to PTO shaft 40. A work implement mounted on or towed by work vehicle 10 can receive power from PTO shaft 40 and perform operations according to various works. Motor 30 and power transmission system 34 may be collectively referred to as an electric powertrain.

[0047] As described above, the work vehicle 10 shown in FIG. 1 does not have an internal combustion engine such as a diesel engine, but instead has a battery 20 and a motor 30. Further, the output shaft 33 of the motor 30 is mechanically coupled to a power transmission system 34 such as a transmission within a transmission case 13. The motor 30 can efficiently generate torque within a relatively wide rotational speed range compared to an internal combustion engine. By using the power transmission system 34 including the transmission, it becomes easy to perform a multi-stage or continuously variable transmission operation to adjust the torque and rotational speed from the motor 30 over an even wider range. For this reason, not only can the work vehicle 10 travel efficiently, but it is also possible to efficiently perform various operations using work implements.

[0048] Depending on the application or size of the work vehicle 10, some functions of the power transmission system 34 may be deleted. For example, part or all of the transmission responsible for the shifting function may be omitted. The number and mounting position of the motors 30 are also not limited to the example shown in FIG. 1. Further, the work vehicle may be a hybrid electric vehicle (HEV) that has an internal combustion engine such as a diesel engine as a power source in addition to an electric motor.

[0049] The work vehicle 10 shown in Figure 1 is equipped with one motor 30. However, the work vehicle 10 may be equipped with multiple electric motors. For example, the work vehicle 10 may be equipped with a travel electric motor that drives a travel system including four 14s and a PTO electric motor that drives the PTO shaft 40. The work vehicle 10 may be equipped with multiple PTO shafts (e.g., a rear PTO shaft, a mid PTO shaft, a front PTO shaft, etc.). In that case, one electric motor may drive multiple PTO shafts, or multiple electric motors may drive multiple PTO shafts. For example, the work vehicle 10 may be equipped with multiple electric motors, each driving a corresponding one of the multiple PTO shafts. The work vehicle 10 may be equipped with a front wheel electric motor that drives two front wheels 14F and a rear wheel electric motor that drives two rear wheels 14R. Alternatively, the work vehicle 10 may be equipped with two electric motors for the front wheels, each driving one of the two front wheels 14F, and two electric motors for the rear wheels, each driving one of the two rear wheels 14R. In other words, the work vehicle 10 may be equipped with four electric motors, each driving one of the four wheels 14. Thus, the work vehicle 10 may be equipped with one or more electric motors for driving the running gear and one or more electric motors for driving one or more PTO shafts. By providing multiple electric motors, the work vehicle 10 can control the rotation of multiple wheels 14 and one or more PTO shafts more flexibly. In the following description, electric motors for driving may be referred to as "driving motors," and electric motors for PTOs may be referred to as "PTO motors."

[0050] <2. Specific Examples of Work Vehicles> Next, we will explain a more specific example of the configuration of work vehicle 10.

[0051] Figure 2 is a side view of a work vehicle 10 according to an exemplary embodiment of the present invention. Figure 3 is a top view of the work vehicle 10 according to this embodiment.

[0052] The work vehicle 10 shown in Figures 2 and 3 comprises a vehicle body 11 and a running gear supported by the vehicle body 11. The running gear includes various devices necessary for driving, such as left and right front wheels 14F, left and right rear wheels 14R, front axle 15F, rear axle 15R, and a rear wheel differential.

[0053] The vehicle body 11 comprises a front frame 12, a transmission case 13, and a housing frame 16. The front frame 12 is connected to the front of the housing frame 16. The transmission case 13 is connected to the rear of the housing frame 16. A first electric motor 30A and a second electric motor 30B are housed inside the housing frame 16. The first electric motor 30A is a driving motor and drives the running gear via a power transmission system in the transmission case 13. The second electric motor 30B is a PTO motor and drives the PTO shaft 40 and one or more hydraulic pumps. The first electric motor 30A and the second electric motor 30B may be electric motors capable of relatively high efficiency and high torque output, such as permanent magnet synchronous motors.

[0054] The front frame 12 is fitted with a front axle case 17F. The front axle case 17F supports the left and right front wheels 14F. The transmission case 13 includes a rear axle case 17R. The rear axle case 17R supports the left and right rear wheels 14R and transmits power to the rear wheels 14R.

[0055] A battery 20 is mounted on the front frame 12. The battery 20 is supported by the front frame 12 and housed inside the front housing 19 (bonnet). The battery 20 stores the power supplied to the first electric motor 30A and the second electric motor 30B. In other words, the battery 20 stores power for driving, operation, and hydraulic drive. In the following description, the battery 20 may be referred to as the "drive battery 20".

[0056] Above the housing frame 16 and the transmission case 13 are a steering wheel 53, a meter panel unit 54, a group of pedals 55 including the accelerator and brake, a group of switches 56 for work driving, and a driver's seat 52. A safety frame 51 is provided behind the driver's seat 52. The safety frame 51 is attached to the transmission case 13 and has a structure that extends upward. Inside the housing frame 16 are the first electric motor 30A and the second electric motor 30B.

[0057] The switch group 56 includes various operating devices such as switches, levers, and dials for adjusting the operation of the work vehicle 10 and the work implement. The switch group 56 includes various operating devices such as an accelerator lever for adjusting the travel speed, a switch for switching the PTO shaft 40 on and off, a dial for adjusting the rotational speed of the PTO shaft 40, and a lever for adjusting the height of the three-point linkage supporting the work implement. By operating the switch group 56, the driver can give various instructions to the work vehicle 10 for travel and work.

[0058] The meter panel unit 54 displays information regarding the status of the work vehicle 10. For example, the meter panel unit 54 displays various information such as the travel speed, the rotational speed of the PTO shaft 40, the height of the three-point linkage, the output of the motors 30A and 30B, the charge status of the battery 20, and the temperature of the battery 20. The meter panel unit 54 may be equipped with analog meters and / or a digital display (hereinafter sometimes simply referred to as "display") for displaying this information. The display of the meter panel unit 54 may display a graphical user interface (GUI) that allows the user to perform various setting operations related to the work vehicle 10. The user can perform various settings related to the work vehicle 10 on the display screen using an input device connected to the meter panel unit 54 or an input means such as a touchscreen mounted on the display.

[0059] As shown in Figure 3, a charging inlet 57 is provided to the right of the steering wheel 53. The charging inlet 57 is a device that includes a socket configured to allow connection of a charging adapter extending from an external power source or charging device. Near the charging inlet 57, a device for the user to initiate charging, such as a charging start button, may be provided. When the user connects the charging adapter to the charging inlet 57 and performs a predetermined operation, such as pressing the charging start button, charging of the battery 20 begins.

[0060] The battery 20 can be charged using either normal charging or rapid charging. In normal charging, AC power supplied from an external AC power source is converted to high-voltage DC power (e.g., around 350V to 450V), and this DC power is supplied to the battery 20. In rapid charging, high-voltage DC power is directly supplied to the battery 20 from an external DC power source. The charging inlet 57 in this embodiment supports both normal and rapid charging. For normal charging, a commercial AC power source that outputs an AC voltage of, for example, 200V or 100V may be used as the power source. For rapid charging, a DC power source that outputs a DC voltage of, for example, around 350V to 450V may be used as the power source. Rapid charging can be performed using protocols compliant with standards such as CHAdeMO, NACS, CCS1, CCS2, GB / T, or ChaoJi.

[0061] The power stored in the battery 20 can also be output to external electrical equipment via the charging inlet 57. Such external power output is referred to as "external power supply" in this specification. External power supply is performed with an external power supply adapter connected to the charging inlet 57. The DC power from the battery 20 can be converted to AC power by a power converter in the work vehicle 10. This AC power can then be supplied to external equipment via the charging inlet 57 and the external power supply adapter.

[0062] As shown in Figure 3, the first electric motor 30A and the second electric motor 30B in this embodiment are arranged side by side. The first electric motor 30A and the second electric motor 30B are rotated by power supplied from the battery 20. The first electric motor 30A drives the running gear via a power transmission system in the transmission case 13. The second electric motor 30B drives the PTO shaft 40 and the hydraulic pump via a power transmission system in the transmission case 13. As a result, the second electric motor 30B drives the work implement and various hydraulic devices. The hydraulic devices may be used, for example, to change the height of the three-point linkage supporting the work implement. The work vehicle 10 may be equipped with a power steering system that assists the driver's steering wheel operation. In this case, the hydraulic devices may also be used in the power steering system to supply auxiliary force to change the steering angle of the front wheels 104F.

[0063] <3. System Configuration of the Work Vehicle> Figure 4 is a block diagram showing the main components of the work vehicle 10 and an example of their connection relationships. In Figure 4, connection relationships related to power transmission, high-voltage drive power, and low-voltage auxiliary power are represented by solid lines of different thicknesses. Connection relationships related to signals (digital signals and analog signals) are represented by dotted lines. Coolant flow is represented by thick dashed lines.

[0064] As shown in Figure 4, the work vehicle 10 is equipped with a first inverter 35A and a second inverter 35B. The first inverter 35A is connected to the first electric motor 30A. The second inverter 35B is connected to the second electric motor 30B. Each of the first inverter 35A and the second inverter 35B converts the DC voltage from the battery 20 into a three-phase AC voltage. The first inverter 35A supplies the converted three-phase AC voltage to the first electric motor 30A. This causes the first electric motor 30A to rotate and the traction device to be driven. The second inverter 35B also supplies the converted three-phase AC voltage to the second electric motor 30B. This causes the second electric motor 30B to rotate and the hydraulic pump 36 and the PTO shaft 40 to be driven.

[0065] The transmission case 13 houses the power transmission system 34A for driving, the power transmission system 34B for work, and the hydraulic pump 36. The power transmission system 34A for driving may include components such as a reduction gear, a sub-transmission, and a differential. The power transmission system 34A for driving transmits power from the rotation of the first electric motor 30A to the rear wheels 14R. In four-wheel drive mode, the power transmission system 34A for driving also transmits a portion of the power from the rotation of the first electric motor 30A to the front wheels 14F. The power transmission system 34B for work may include components such as a reduction gear, a PTO clutch, and a PTO transmission. The power transmission system 34B for work transmits power from the rotation of the second electric motor 30B to the hydraulic pump 36 and the PTO shaft 40. The PTO shaft 40 supplies power for work to the work implement.

[0066] The PTO shaft 40 shown in Figure 4 is the rear PTO shaft. In addition to the rear PTO shaft, the work vehicle 10 may also have a mid-PTO shaft or a front PTO shaft. If the work vehicle 10 has multiple PTO shafts, the power transmission system 34B may be configured to distribute the power generated by the rotation of the second electric motor 30B to the multiple PTO shafts. Alternatively, in addition to the second electric motor 30B that drives the PTO shaft 40, the work vehicle 10 may include other electric motors that drive the other PTO shafts.

[0067] The implements connected to the PTO shaft 40 may include, for example, a rotary tiller, a seeder, a spreader, a transplanter, a mower, a rake, a baler, a harvester, a sprayer, or a harrow. Any implement can be connected to the work vehicle 10 and used.

[0068] The hydraulic pump 36 is driven by power from the second electric motor 30B. The hydraulic pump 36 pressurizes the hydraulic fluid, thereby changing the height of the three-point linkage to which the work equipment is connected. Alternatively, the hydraulic pump 36 may be used in a hydraulic power steering system. If a front loader is mounted as the work equipment, the hydraulic pump 36 may be used in a hydraulic system that enables the lifting and lowering of the front loader. Power from the second electric motor 30B may be transmitted to multiple hydraulic pumps to drive these multiple hydraulic systems. Alternatively, the work vehicle 10 may have one or more electric motors for hydraulics separate from the second electric motor 30B.

[0069] In the example shown in Figure 4, the work vehicle 10 further comprises a power converter 58, a power distribution unit (PDU) 80, an auxiliary battery 21, and a battery temperature control system 70.

[0070] The power converter 58 is positioned between the charging inlet 57 and the battery 20 and performs power conversions such as AC to DC conversion and voltage conversion. Figure 5 shows an example of the configuration of the power converter 58 and its connection to other equipment. The power converter 58 shown in Figure 5 includes an onboard charger (OBC) 81 and a DC-DC converter 82. During normal charging, the OBC 81 converts AC power from the charging inlet 57 to DC power and supplies it to the drive battery 20 via the power distribution unit 80. The drive battery 20 is charged by this DC power. The DC-DC converter 82 is connected to the OBC 81 and also to the battery 20 via the power distribution unit 80. The DC-DC converter 82 converts the relatively high-voltage DC power output from the OBC 81 or the drive battery 20 to lower-voltage DC power (e.g., 12V or 24V). The low-voltage DC power converted by the DC-DC converter 82 is supplied to the auxiliary battery 21 and the auxiliary components 84. The auxiliary components 84 include several devices that operate on the relatively low voltage output from the DC-DC converter 82 or the battery 21. For example, the auxiliary components 84 include several electronic control units (ECUs) and other electrical components. The auxiliary battery 21 is charged by the DC voltage output from the DC-DC converter 82. The auxiliary battery 21 stores the power supplied to the auxiliary components 84, such as each ECU, the meter panel unit 54, the pumps 67, 77, and the air conditioner. The battery 21 may be, for example, a lead-acid battery.

[0071] Refer to Figure 4 again. The work vehicle 10 is equipped with multiple ECUs. The multiple ECUs include a main ECU 61, an electric ECU 62, and a charging ECU 63. The main ECU 61 controls the overall operation of the work vehicle 10 based on signals generated by the user operating the pedal group 55, the switch group 56, and the meter panel unit 54. The electric ECU 62 mainly controls the charging and discharging of the battery 20 and the operation of the electric motors 30A and 30B. The charging ECU 63 communicates with an external charger (external power supply) and performs control to ensure smooth charging by appropriately controlling the relay 64.

[0072] In this embodiment, the combination of the main ECU 61, the electric ECU 62, and the charging ECU 63 functions as a "control device" that controls the operation of the work vehicle 10. Therefore, in the following description, the operations performed by the main ECU 61, the electric ECU 62, and the charging ECU 63 all correspond to operations performed by the "control device". These ECUs can communicate with each other according to a vehicle bus standard such as CAN (Controller Area Network). Instead of CAN, a faster communication method such as on-board Ethernet (registered trademark) may be used. An on-board computer integrating at least some of the functions of the main ECU 61, the electric ECU 62, and the charging ECU 63 may be provided as the "control device". The control device may include ECUs other than the main ECU 61, the electric ECU 62, and the charging ECU 63. Each ECU may be a computing device including one or more processors and one or more memories. Each ECU can perform the operations described later by having the processor execute a computer program stored in the memory.

[0073] The electric ECU 62 sends control signals to the first inverter 35A and the second inverter 35B in response to signals from the pedal group 55 and the switch group 56. The electric ECU 62 can perform motor control based on a rotational speed command value or a torque command value determined, for example, according to the amount of operation of the pedal group 55 by the driver. In this specification, the control based on the former rotational speed command value may be referred to as "speed control".

[0074] The electric ECU 62 controls the switching operation of multiple switch elements (e.g., MOSFETs) in the first inverter 35A and the second inverter 35B, respectively. Specifically, the electric ECU 62 generates control signals to control the switching operation of each switch element and outputs them to each inverter. The first inverter 35A converts the DC power from the battery 20 into three-phase AC power, which is a pseudo-sine wave of, for example, u-phase, v-phase, and w-phase, according to the control signals from the electric ECU 62, and supplies this three-phase AC power to the first electric motor 30A. Similarly, the second inverter 35B converts the DC power from the battery 20 into three-phase AC power, which is a pseudo-sine wave of, for example, u-phase, v-phase, and w-phase, according to the control signals from the electric ECU 62, and supplies this three-phase AC power to the second electric motor 30B. As a result, the electric ECU 62 can rotate the electric motors 30A and 30B at appropriate rotational speeds and torques according to the driver's operation.

[0075] While the work vehicle 10 is in operation, the main ECU 61 causes the meter panel unit 54 to display information regarding the status of the work vehicle 10. For example, the main ECU 61 displays information such as the travel speed, the operating status of the motors 30A and 30B, the charge status of the battery 20, and the status of the power transmission system 34A and the transmission included in 34A on the meter panel unit 54.

[0076] Figure 6 is a block diagram showing an example of the hardware configuration of each ECU. Each ECU 400 includes a processor 434, ROM 435, RAM 436, external I / F 437, and communication I / F 438. These components are interconnected via a bus 439.

[0077] ROM 435 is, for example, writable memory (e.g., PROM), rewritable memory (e.g., flash memory), or read-only memory. ROM 435 stores a program that controls the operation of the processor 434. ROM 435 does not have to be a single recording medium; it may be a collection of multiple recording media. Some of the multiple storage media may be removable memory.

[0078] RAM 436 provides a working area for temporarily unpacking the program stored in ROM 435 at boot time. RAM 436 does not need to be a single recording medium; it may be a collection of multiple recording media.

[0079] External I / F 437 is an interface for connecting to external devices. Communication I / F 438 is an interface for communicating with other electronic devices (e.g., sensors and other ECUs). For example, communication I / F 438 can perform wired communication compliant with various protocols such as CAN or Ethernet®. Communication I / F 438 may also perform wireless communication compliant with wireless communication standards such as Bluetooth® and / or Wi-Fi®.

[0080] The ECU may further include a storage device for storing data generated by the processor 434 for a relatively long period of time. Such a storage device may be, for example, a semiconductor storage device, a magnetic storage device, or an optical storage device, or a combination thereof.

[0081] The power distribution unit 80 shown in Figure 4 is a device that electrically connects equipment such as the charging inlet 57, power converter 58, battery 20, inverters 35A and 35B, and heater 72.

[0082] Figure 7 shows an example of the configuration of the power distribution unit 80. The power distribution unit 80 may have a plurality of relay circuits 83 (83a to 83g) that operate under the control of the electric ECU 62. During charging, the power distribution unit 80 is configured to supply power from the charging inlet 57 or the power converter 58 to the battery 20, and to the heater 72 when the temperature is low. On the other hand, during discharging, the power distribution unit 80 is configured to distribute power from the battery 20 to the first inverter 35A, the second inverter 35B, and the power converter 23. The electric ECU 62 may be configured or programmed to control the charging and discharging of the battery 20 by appropriately switching the on and off of the plurality of relay circuits 83a to 83g in the power distribution unit 80. In this specification, relay circuits may be simply referred to as "relays".

[0083] As shown in Figure 4, the battery 20 includes a battery management system (BMS) 22 and a temperature sensor 24. The BMS 22 is configured to monitor the state of the battery 20, such as the input voltage, output voltage, and temperature, and to control the charging and discharging currents to the battery 20 based on these states. The temperature sensor 24 may be configured to measure the temperature of each of the multiple cells contained in the battery 20.

[0084] The work vehicle 10 illustrated in Figure 4 is equipped with a cooling system 60 for high-voltage equipment and a battery temperature control system 70. The cooling system 60 is used to cool equipment to which high voltage is applied (also referred to as "high-voltage equipment"). The cooling system 60 comprises a radiator 65, a reservoir tank 66, a pump 67, and a cooling fan 68. In the example in Figure 4, the cooling system 60 is connected via hoses to the first inverter 35A, the first electric motor 30A, the second electric motor 30B, the second inverter 35B, and the power converter 58 in that order. This forms a flow path through which the coolant circulates. The coolant in the cooling system 60 is, for example, water or oil. The cooling system 60 cools these high-voltage equipment by circulating the coolant through the flow path. The coolant heated by the high-voltage equipment is cooled by heat dissipation in the radiator 65. The cooling fan 68 generates cooling air to cool the coolant inside the radiator 65. The cooling air promotes heat dissipation from the radiator 65.

[0085] The battery temperature control system 70 is used to cool or heat (also referred to as "heating") the battery 20. The battery temperature control system 70 comprises a heater 72, a radiator 75, a reservoir tank 76, and a pump 77. The battery temperature control system 70 is connected to the battery 20 via a hose. This creates a passage through which the coolant circulates. The coolant in the battery temperature control system 70 is, for example, water or oil. The battery temperature control system 70 cools the battery 20 by circulating the coolant through the passage. The coolant heated by the battery 20 is cooled by heat dissipation in the radiator 75. Cooling air from the cooling fan 68 also plays a role in cooling the coolant inside the radiator 75. The heater 72 raises the temperature of the battery 20 by warming the coolant. This makes it possible to suppress a decrease in the charge and discharge performance of the battery 20 even in low-temperature environments where the ambient temperature is, for example, below 0 degrees Celsius (°C).

[0086] The operation of the cooling system 60 and the battery temperature control system 70 is controlled by the electric ECU 62. For example, the electric ECU 62 is configured or programmed to maintain the temperature of the battery 20 within an appropriate range by controlling the battery temperature control system 70 based on the temperature of the battery 20 measured by the temperature sensor 24. In addition to the measurement value of the temperature sensor 24, the electric ECU 62 may also control the battery temperature control system 70 based on the measurement value of a temperature sensor 25 that measures the ambient temperature and is installed in the work vehicle 10.

[0087] The flow paths of the coolant in the cooling system 60 and the battery temperature control system 70 are not limited to the illustrated paths and can be changed as appropriate. The cooling method in the cooling system 60 and the battery temperature control system 70 is not limited to water cooling or oil cooling, but may also be air cooling. Alternatively, the refrigerant used in an air conditioner may be used instead of the above-mentioned coolant.

[0088] <4. Control of Application Rate in Application Operations> In conventional agricultural machinery driven by engine power, control is performed to maintain the rotation speed of the PTO shaft at the rated rotation speed (e.g., 540 rpm) from the viewpoint of performing agricultural work stably. Therefore, in implements such as seeders or broadcasters, a dedicated unit is provided that enables electronic control of the shutter opening in order to dynamically change the application rate, such as the amount of pesticide or fertilizer sprayed or the amount of seeds sown. With the dedicated unit, it becomes possible to control the shutter opening in conjunction with the vehicle speed, thereby controlling the application rate in conjunction with the vehicle speed.

[0089] Furthermore, in conventional agricultural machinery driven by engine power, it is difficult to independently control the vehicle speed and the rotational speed of the PTO shaft. For example, it is difficult to change only the rotational speed of the PTO shaft while maintaining a constant vehicle speed. To set the rotational speed of the PTO shaft and the vehicle speed to a desired ratio, a multi-speed gear or a hydrostatic continuously variable transmission (HST) is required. However, using these components tends to increase costs and complicate control.

[0090] To solve the above problems, the work vehicle in this embodiment is capable of being fitted with implements for application work including pesticide spraying, fertilization, and seeding, and comprises a PTO shaft for supplying power to the implements, a PTO motor having an output shaft directly or indirectly connected to the PTO shaft, and a control device for controlling the PTO motor. The work vehicle may be configured to be driven by automatic driving, including autonomous driving, and / or manual driving.

[0091] The control device may be configured or programmed to control the application rate of the fertilizer by determining a target motor speed based on the target application rate and changing the speed of the PTO motor in accordance with the target motor speed. In the example in Figure 4, the electric ECU 62 functions as a control device that controls the application rate of the fertilizer. The target application rate may be calculated, for example, from a given fertilizer application rate specified by the user.

[0092] In one embodiment, the control device may include one or more processors and one or more memories that store programs for controlling the operation of the one or more processors. The one or more processors may, according to the program, determine a target motor rotation speed based on a target application rate and perform a process to control the application rate of the application work by changing the rotation speed of the PTO motor according to the target motor rotation speed.

[0093] The motor control method performed by (or implemented in) a computer in this embodiment is used for a work vehicle equipped with a PTO shaft that supplies power to a work machine that performs application work including pesticide spraying, fertilization, and seeding, and a PTO motor having an output shaft directly or indirectly connected to the PTO shaft. The method includes determining a target motor rotation speed based on a given target application rate and controlling the application rate of the application work by changing the rotation speed of the PTO motor in accordance with the target motor rotation speed.

[0094] A computer program containing a set of instructions for causing one or more computers to execute the above-described method for controlling the PTO motor may be manufactured and sold independently of the work vehicle. The computer program may be provided, for example, by being stored in a computer-readable non-temporary storage medium. The computer program may also be provided by download via a telecommunications line (e.g., the Internet).

[0095] According to the electric work vehicle, motor control method, or computer program of this embodiment, the application rate can be dynamically changed independently of the vehicle speed by controlling the rotation speed of the PTO motor in accordance with a target motor rotation speed determined based on the target application rate. For example, speed control can be applied to the control of the PTO motor. Even without providing the dedicated unit, multi-speed gear, or HST mentioned above, it becomes possible to control the application rate of the application work in conjunction with the vehicle speed, for example.

[0096] In this embodiment, the work vehicle may optionally be equipped with a drive motor to drive the travel mechanism in addition to the PTO motor. However, the power source that generates the power to drive the travel mechanism is not limited to a motor, but may be an engine. With such a work vehicle, it becomes possible to control the drive motor and the PTO motor independently. Therefore, since the ratio of the rotational speeds of the drive motor and the PTO motor can be changed arbitrarily, for example, by changing the rotational speed of the PTO shaft while keeping the rotational speed of the drive motor constant, it becomes possible to dynamically change the application rate while maintaining a constant vehicle speed of the work vehicle.

[0097] Figure 8 is a flowchart showing an example of a motor control procedure for controlling the application rate of an application operation by the rotation speed of the PTO shaft. The motor control method in the example of Figure 8 includes calculating a target application rate (step S110), determining a target motor rotation speed based on the target application rate (step S120), and controlling the application rate of the application operation by changing the rotation speed of the PTO motor according to the target motor rotation speed (step S130).

[0098] (Step S110) Figure 9 is a schematic diagram showing an example of connection between the work vehicle 10 and the external server 700.

[0099] The work vehicle 10 may be equipped with a communication device 90 for communicating with the server 700. The server 700 is, for example, a cloud server. The server 700 may create and manage application work plan data, which includes information on application amounts. Application amounts may be defined by the weight (e.g., grams) of fertilizer, pesticide, or seeds to be sprayed or sown per unit distance (e.g., 1 m). For example, the application work plan may include information for each registered agricultural machine indicating the day and time the application work will be performed, the field, the work content, and the machinery to be used. Depending on the work content, the application work plan may further include information such as pesticides, the amount of pesticide to be sprayed, or the amount of seeds to be sown.

[0100] The communication device 90 of the work vehicle 10 and the server 700 are connected via a network for communication. Data for the application work plan can be transmitted from the server 700 to the communication device 90 via the network. The application work plan data transmitted from the server 700 can be downloaded by the control device 410 of the work vehicle 10 before the application work is performed and stored in the storage device of the work vehicle 10. Alternatively, the server 700 can sequentially issue instructions for the application work to the work vehicle 10 according to the application work plan. When coordinating with the server in this way, data indicating a given application amount can be transmitted from the server 700 periodically or periodically. Therefore, the given application amount acquired by the control device 410 can be updated periodically or periodically.

[0101] In this embodiment, the communication device 90 receives application work plan data transmitted from the server 700 before the application work and outputs it to the control device 410. The control device 410 receives the application work plan data output from the communication device 90 and can obtain a given application amount from the application work plan data.

[0102] As another example, the work vehicle 10 may be equipped with a terminal monitor 91. The terminal monitor 91 is a terminal for the user to perform operations related to the driving and work of the work vehicle 10, and is also called a virtual terminal (VT). The terminal monitor 91 may be equipped with a display device such as a touchscreen and / or one or more buttons. The display device may be a display such as a liquid crystal or organic light-emitting diode (OLED). By operating the terminal monitor 91, the user can perform various operations such as specifying the amount to be applied, recording or editing field map data, setting the driving route, setting the type of crop, and setting the type of application work.

[0103] As yet another example, a user may specify the application rate using a terminal device such as a smartphone. Once the application rate is specified by the terminal monitor 91 or the terminal device, the work vehicle may perform the application work according to the specified rate until the application work is completed.

[0104] The control device can calculate a target application rate based on a specified application rate. The target application rate may be defined, for example, by the number of PTO shaft rotations per unit distance. For example, if 100 g is specified as the application rate per meter, the control device can calculate the number of PTO shaft rotations per meter (e.g., 100 rotations) from the given fertilizer application rate and determine the calculated number of PTO shaft rotations as the target application rate.

[0105] Taking fertilization as an example of application work, the control device can control the rotational speed of the fertilizer rolls, which are installed on the broadcaster and driven by power from the PTO shaft, by changing the rotational speed of the PTO shaft. The control device can determine the planned distance to be traveled and, while controlling the rotational speed of the fertilizer rolls installed on the broadcaster, can have the work vehicle perform the fertilization work.

[0106] (Step S120) The control device determines the target motor rotation speed based on the target application rate. The target motor rotation speed corresponds to the rotation speed command value in the speed control described above. Referring to Figures 10 to 12, the procedures for determining the target motor rotation speed according to the first to third implementation examples in this embodiment will be explained.

[0107] Figure 10 is a flowchart showing the procedure for determining the target motor rotation speed according to the first implementation example. The process for determining the target motor rotation speed according to the first implementation example (step S120) includes determining the target rotation speed of the PTO shaft based on the target application rate (step S210-1), and determining the target motor rotation speed according to the target rotation speed of the PTO shaft (step S120-2).

[0108] (Step S120-1) The control device determines the target rotational speed of the PTO shaft based on the target application rate. A linear relationship basically exists between the target application rate of the application work and the target rotational speed of the PTO shaft. Therefore, the control device can use this linear relationship to determine the target rotational speed of the PTO shaft from the target application rate. On the other hand, there may be exceptional cases where a linear relationship does not exist between the target application rate of the application work and the target rotational speed of the PTO shaft. In this case, for example, a table relating the rotational speed of the PTO shaft and the target application rate may be generated in advance. This table may be stored in a memory device provided by the work vehicle. The control device can refer to the table to determine the target rotational speed of the PTO shaft based on the target application rate. Even when a linear relationship exists between the target application rate and the target rotational speed of the PTO shaft, a reference table may be generated, and the control device can refer to the table to determine the target rotational speed of the PTO shaft.

[0109] (Step 120-2) The control device determines the target motor speed according to the target rotational speed of the PTO shaft. As mentioned above, the power transmission system for work may include a speed reducer. In this case, the control device may determine the target motor speed according to the target rotational speed of the PTO shaft and the reduction ratio of the speed reducer. In other words, the control device may apply a correction process based on the reduction ratio of the speed reducer to determine the target motor speed. For example, this correction process is effective when the target application rate and the target rotational speed of the PTO shaft are theoretically designed to change linearly, but the target application rate does not change linearly with respect to the target rotational speed of the PTO shaft.

[0110] Figure 11 is a flowchart showing the procedure for determining the target motor rotation speed according to the second implementation example. The process for determining the target motor rotation speed according to the second implementation example (step S120) includes obtaining at least one of the ground speed of the work vehicle or the rotation speed of the drive wheels (hereinafter referred to as "vehicle speed") (step S210-3), determining the target rotation speed of the PTO shaft based on the ground speed and / or vehicle speed and the target application rate (step S120-4), and determining the target motor rotation speed according to the target rotation speed of the PTO shaft (step S120-2).

[0111] (Step S120-3) Refer again to Figure 9. As illustrated in Figure 9, the work vehicle 10 may be equipped with a vehicle speed sensor 92 for measuring the travel speed of the work vehicle 10. The vehicle speed sensor 92 measures, for example, the rotational speed of the drive wheels or axles, i.e., the number of rotations per unit time, and calculates the vehicle speed based on the measured value. In the case of two-wheel drive, the front wheels or rear wheels function as drive wheels, and in the case of four-wheel drive, the front wheels and rear wheels may function as drive wheels.

[0112] The work vehicle 10 further includes a positioning device 93 that acquires positional information of the work vehicle 10 in the field. The positioning device 93 acquires positional data of the work vehicle 10 and may include a GNSS unit that includes a GNSS receiver. The GNSS unit may also include an inertial measuring unit (IMU). The GNSS receiver may include an antenna that receives signals from GNSS satellites and a processor that calculates the position of the work vehicle 10 based on the signals received by the antenna. The positioning device 93 outputs GNSS data that includes the positional information of the work vehicle 10. The GNSS unit receives satellite signals transmitted from multiple GNSS satellites and performs positioning based on the satellite signals. GNSS is a general term for satellite positioning systems such as GPS (Global Positioning System), QZSS (Quasi-Zenith Satellite System, e.g., Michibiki), GLONASS, Galileo, and BeiDou.

[0113] The control device can calculate the ground speed of the work vehicle 10 based on the GNSS data output from the positioning device 93. In this way, the control device can acquire information regarding at least one of the ground speed or vehicle speed of the work vehicle.

[0114] The control device 410, terminal monitor 91, vehicle speed sensor 92, and positioning device 93 are connected to each other so as to be able to communicate with one another, for example, via a CAN bus. The control device 410 receives sensor data output from the vehicle speed sensor 92 and acquires the vehicle speed indicated by the sensor data. Based on the acquired vehicle speed, the control device 410 can determine the target speed of the work vehicle 10 and control the drive motor according to the rotational speed command value corresponding to the target speed.

[0115] (Step S120-4) The control device may determine a target rotational speed of the PTO shaft based on the acquired ground speed and / or vehicle speed and the target application rate. In this way, by determining the target rotational speed of the PTO shaft based on the target application rate and further based on at least one of the ground speed or the rotational speed of the drive wheels, it becomes possible to improve the accuracy of application rate control.

[0116] When comparing ground speed derived from GNSS data with vehicle speed, the vehicle speed has higher responsiveness and a lower update rate. Therefore, by combining the two speeds, it is possible to improve the accuracy of the true vehicle speed necessary for determining the target rotational speed of the PTO shaft. For this reason, it is preferable to use a combination of the two speeds to determine the target rotational speed of the PTO shaft.

[0117] Once the control device determines the target rotational speed of the PTO shaft, it determines the target motor rotational speed or rotational speed command value according to the target rotational speed of the PTO shaft (step S120-2). The control device can then control the PTO motor according to the target motor rotational speed or rotational speed command value.

[0118] Figure 12 is a flowchart showing the procedure for determining the target motor rotation speed according to the third implementation example. The process for determining the target motor rotation speed according to the third implementation example (step S120) includes obtaining the ground speed and vehicle speed of the work vehicle (step S210-5), calculating the slip ratio from the ground speed and vehicle speed of the work vehicle (step S210-6), determining the target rotation speed of the PTO shaft based on the target application rate and the slip ratio (step S120-7), and determining the target motor rotation speed according to the target rotation speed of the PTO shaft (step S120-2).

[0119] (Step S120-5) The control device acquires the ground speed and vehicle speed of the work vehicle.

[0120] (Step S120-6) The control device may determine the slip ratio of the work vehicle from the ground speed and vehicle speed. The slip ratio of the work vehicle may be calculated by known methods. For example, the control device acquires information on the ground speed and vehicle speed of the work vehicle while the work vehicle is running in automatic or manual mode, and calculates the slip ratio of the work vehicle based on the ground speed and vehicle speed. The control device also determines the target speed of the work vehicle based on the vehicle speed.

[0121] If there is no slip between the drive wheels and the ground, the target speed and the ground speed will be equal. However, if there is slip in the drive wheels, a discrepancy will occur between the target speed and the ground speed. The control device can calculate the slip ratio based on the discrepancy between the target speed and the ground speed. The larger the discrepancy between the target speed and the ground speed, the larger the slip ratio. The slip ratio is generally expressed as the ratio of the difference between the target speed and the ground speed to the target speed (slip ratio = (target speed - ground speed) / target speed).

[0122] (Step S120-7) The control device can determine the target rotational speed of the PTO shaft based on the target dispensing rate and the slip ratio. The control device can dynamically correct the target rotational speed of the PTO shaft, which was determined based on the target dispensing rate, based on the slip ratio. In this way, by correcting the target rotational speed of the PTO shaft according to the slip ratio, it becomes possible to improve the accuracy of dispensing rate control even when slip occurs.

[0123] Once the control device determines the target rotational speed of the PTO shaft, it determines the target motor rotational speed or rotational speed command value according to the target rotational speed of the PTO shaft (step S120-2). The control device can then control the PTO motor according to the target motor rotational speed or rotational speed command value.

[0124] (Step S130) Refer to Figure 8 again. In this embodiment, the control device determines the target motor rotation speed in any of the procedures of the first to third embodiments, and then controls the application rate of the application work by changing the rotation speed of the PTO motor according to the target motor rotation speed. As described above, for example, the control device can control the rotation speed of the fertilizer roll provided on the broadcaster by changing the rotation speed of the PTO shaft. This ensures that the application work is carried out accurately in accordance with the specified application rate.

[0125] As described above, according to this embodiment, by controlling the rotation speed of the PTO motor in accordance with a target motor rotation speed determined based on a given application rate, it becomes possible to dynamically change the application rate independently of the vehicle speed.

[0126] Figure 13 is a schematic diagram showing a work vehicle performing application work in a field containing two work areas. The field 500 illustrated in Figure 13 includes two work areas 500A and 500B. Figure 13 shows the travel path P for the work vehicle 10 to travel.

[0127] The aforementioned application work plan may include information regarding target application rates associated with each of the multiple work areas contained in one or more fields. Based on the target application rates associated with each of the multiple work areas, the control device may determine the target rotational speed of the PTO shaft for each corresponding work area among the multiple work areas.

[0128] In the example shown in Figure 13, the application work plan includes information on target application rates associated with each of the two work areas 500A and 500B contained within field 500. The target application rates associated with each of the two work areas 500A and 500B may be different or the same. This sets different or identical target rotational speeds for the PTO shaft in each of the two work areas 500A and 500B.

[0129] Even within the same field, crop growth conditions can vary depending on the location due to factors such as soil properties. According to this embodiment, for example, in an application work plan, it is possible to specify the application rate for each location on a field map. For example, while a work vehicle is driving around the field and performing application work, a cloud server can apply image processing to field image data that includes the crops planted in the field as subjects to analyze the crop growth conditions, and from the analysis results, it can determine the application rate to be administered according to the location or work area. In this way, by coordinating with a cloud server, for example, it becomes possible to make the application rate variable for each location or work area.

[0130] In the example shown in Figure 13, the control device may determine a target rotational speed of the PTO shaft for performing application work in work area 500A based on a target application rate associated with work area 500A, and determine a target rotational speed of the PTO shaft for performing application work in work area 500B based on a target application rate associated with work area 500B.

[0131] Although the crop growth conditions in the two work areas 500A and 500B may differ, this type of control makes it possible to apply fertilizer at a rate that is appropriate for the crop growth conditions in each work area.

[0132] The present invention is applicable to all types of work vehicles equipped with a PTO motor for application work.

[0133] 10...Work vehicle, 11...Body, 12...Front frame, 13...Transmission case, 14...Wheels, 14F...Front wheels, 14R...Rear wheels, 15F...Front axle, 15R...Rear axle, 16...Housing frame, 17F...Front axle case, 17R...Rear axle case, 19...Front housing, 20...Battery, 22...Battery management system (BMS), 24...Temperature sensor, 30, 30A, 30B...Electric motor, 33...Output shaft, 34...Power transmission system, 35A, 35B...Inverter, 36...Hydraulic pump, 40...PTO shaft, 51...Rops frame, 52...Driver's seat, 53...Steering wheel, 54...Meter panel unit, 55...Pedal group, 56...Switch group, 57...Charging inlet 58... Power converter, 60... Cooling system for high-voltage equipment, 61... Main ECU, 62... Electric ECU, 63... Charging ECU, 64... Relay, 65... Radiator for high-voltage equipment, 66... ​​Reservoir tank, 67... Pump, 68... Cooling fan, 70... Battery temperature control system, 72... Heater, 75... Radiator for battery, 76... Reservoir tank, 77... Pump, 80... Power distribution unit, 81... Onboard charger (OBC), 82... DC-DC converter, 90... Communication device, 91... Terminal monitor, 92... Vehicle speed sensor, 93... Positioning device

Claims

1. An electric work vehicle capable of being fitted with a work machine for performing application work including pesticide spraying, fertilization, and sowing, comprising: a PTO shaft for supplying power to the work machine; an electric motor having an output shaft directly or indirectly connected to the PTO shaft; and a control device for controlling the electric motor, wherein the control device determines a target motor rotation speed based on a target application rate, and controls the application rate of the application work by changing the rotation speed of the electric motor according to the target motor rotation speed.

2. The work vehicle according to claim 1, wherein the control device determines a target rotational speed of the PTO shaft based on the target application rate, and determines the target motor rotational speed according to the target rotational speed of the PTO shaft.

3. The work vehicle according to claim 2, comprising a storage device that stores a table relating the target rotational speed of the PTO shaft and the target application rate, wherein the control device refers to the table and determines the target rotational speed of the PTO shaft based on the target application rate.

4. A work vehicle according to claim 2 or 3, further comprising: a running gear including drive wheels; a positioning device for acquiring positional information of a work vehicle in a field, wherein the control device further determines a target rotational speed of the PTO shaft based on at least one of the ground speed of the work vehicle calculated based on data output from the positioning device, or the rotational speed of the drive wheels.

5. The work vehicle according to claim 4, wherein the control device determines the slip ratio of the work vehicle from the ground speed and the rotational speed of the drive wheels, and determines the target rotational speed of the PTO shaft based on the target application rate and the slip ratio.

6. The work vehicle according to claim 4, wherein the electric motor is a first electric motor and is further equipped with a second electric motor that drives the traveling device.

7. A work vehicle according to any one of claims 1 to 3, comprising a communication device for communicating with a server, wherein the communication device receives application work plan data including information on the target application amount transmitted from the server, and the control device receives the application work plan data output from the communication device and obtains the target application amount from the application work plan data.

8. The work vehicle according to claim 7, wherein the application work plan includes information relating to a target application rate associated with each of a plurality of work areas included in one or more fields, and the control device determines a target rotational speed of the PTO shaft for each corresponding work area among the plurality of work areas based on the target application rate associated with each of the plurality of work areas.

9. The work vehicle according to claim 1, wherein the control device includes one or more processors and one or more memories for storing a program for controlling the operation of the one or more processors, and the one or more processors, in accordance with the program, determine a target motor rotation speed based on the target application rate and perform a process to control the application rate of the application work by changing the rotation speed of the electric motor in accordance with the target motor rotation speed.

10. A motor control method performed by a computer for use in a work vehicle equipped with a PTO shaft for supplying power to a work machine that performs application work including pesticide spraying, fertilization, and sowing, and an electric motor having an output shaft directly or indirectly connected to the PTO shaft, the motor control method comprising: determining a target motor rotation speed based on a target application rate; and controlling the application rate of the application work by changing the rotation speed of the electric motor in accordance with the target motor rotation speed.

11. A computer program used for motor control of a work vehicle comprising a PTO shaft for supplying power to a work machine that performs application work including pesticide spraying, fertilization, and sowing, and an electric motor having an output shaft directly or indirectly connected to the PTO shaft, wherein the computer causes the computer to perform the following: determine a target motor rotation speed based on a target application rate, and control the application rate of the application work by changing the rotation speed of the electric motor in accordance with the target motor rotation speed.

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