JP7155328B2 - work vehicle - Google Patents

Description

The present invention primarily relates to a work vehicle that travels autonomously along a predetermined route.

2. Description of the Related Art Conventionally, a work vehicle capable of autonomous travel using a satellite positioning system has been known. Patent Literature 1 discloses this type of work vehicle. The work vehicle of Patent Document 1 includes position calculation means for measuring the position of the machine body using a satellite positioning system, and a control device for automatically running and working along the set running route, The remote control device is configured to be able to communicate with the work vehicle wirelessly. With this configuration, in Patent Document 1, the work vehicle can be remotely operated without the worker getting on the work vehicle.

In addition, Patent Literature 2 discloses a work vehicle that can execute a mode in which the work vehicle travels manually and a mode in which the work vehicle travels autonomously while a worker is on the vehicle.

JP 2015-188423 A JP 2014-182453 A

Here, Patent Documents 1 and 2 do not describe how to control the steering angle when switching from forward to reverse (or vice versa).

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its main object is to provide a construction capable of smoothly switching between forward and backward travel in a work vehicle that autonomously travels along a predetermined route. That's what it is.

The problems to be solved by the present invention are as described above. Next, the means for solving the problems and the effects thereof will be described.

According to the aspect of the present invention, a working vehicle having the following configuration is provided. That is, the work vehicle autonomously travels along a travel path having a plurality of predetermined work paths and a turning path that connects ends of the work paths and includes switching from forward to reverse or from reverse to forward. run. The work vehicle includes wheels and a controller. The control unit controls the direction of rotation of the wheels and the steering angle, which is the turning angle of the wheels, along the travel route. When the control unit determines that the steering angle at the timing of switching from forward to reverse or from reverse to forward in the turning circuit is equal to or less than a predetermined angle, the steering angle is not a neutral angle, and the direction of rotation of the wheel is determined. can be changed from the forward direction to the reverse direction or from the reverse direction to the forward direction.

In the work vehicle described above, it is preferable that the predetermined angle or less is a case where a judgment angle, which is a steering angle with respect to the neutral angle of the wheels, is a first angle or less.

It is preferable that the work vehicle has the following configuration. That is, the turning path includes a straight path and a forward turning path , which is a path for turning while moving forward. The control unit is capable of changing the rotation direction of the wheel from the forward direction to the reverse direction when switching from the forward turning circuit to the straight turning circuit, and switching from the straight turning circuit to the forward turning circuit. It is possible to change the direction of rotation of the wheels from the backward direction to the forward direction when the vehicle is moving.

BRIEF DESCRIPTION OF THE DRAWINGS The side view which shows the whole structure of the robot tractor which concerns on one Embodiment of this invention. The top view of a robot tractor. The figure which shows the radio|wireless communication terminal with which an autonomous driving system is equipped. FIG. 2 is a block diagram showing the main configuration of the control system of the robot tractor and wireless communication terminal; FIG. 4 is a diagram showing a display example of a monitor screen on the display of the wireless communication terminal; FIG. 4 is a schematic diagram showing an example of an autonomous driving route generated by a wireless communication terminal; The schematic diagram explaining the flow when switching forward/backward and turning. FIG. 4 is a schematic diagram showing a determination angle θ when a neutral angle is used as a reference angle; 4 is a flowchart showing a process related to steering angle change at the time of switching between forward and backward travel; FIG. 4 is a schematic diagram showing that the current position is different between when moving forward and when moving backward; The schematic diagram explaining another method which switches forward and backward and turns. FIG. 4 is a schematic diagram showing a determination angle θ when a target angle is used as a reference angle; 4 is a flowchart showing a process related to steering angle change at the start of forward/backward movement;

Next, embodiments of the present invention will be described with reference to the drawings. Below, the same reference numerals are given to the same members in each figure of the drawings, and redundant description may be omitted. In addition, the names of members and the like corresponding to the same reference numerals may be simplified, or may be replaced with names of higher-level concepts or lower-level concepts.

An autonomous traveling system autonomously travels one or more work vehicles in a work area and a non-work area to perform all or part of work. In this embodiment, a tractor is used as a working vehicle. machine is also included. In this specification, the term "autonomous travel" means that the tractor travels along a predetermined route under the control of a configuration related to travel provided by the tractor by a control unit (ECU) provided in the tractor. It means that the configuration related to the work of the tractor is controlled by the control unit of the tractor, and the tractor performs the work along a predetermined route. It should be noted that autonomous traveling and autonomous work include cases where a person is on the tractor and cases where no person is on the tractor. On the other hand, manual travel/manual work means that each component of the tractor is operated by the user to travel/work.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side view showing the overall configuration of a robot tractor 1 provided in an autonomous traveling system 99 according to one embodiment of the invention. FIG. 2 is a plan view of the robot tractor 1. FIG. FIG. 3 is a diagram showing a wireless communication terminal 46 provided in an autonomous driving system 99 according to one embodiment of the invention. FIG. 4 is a block diagram showing the main configuration of the control system of the robot tractor 1 and wireless communication terminal 46. As shown in FIG.

As shown in FIG. 1, a robot tractor (work vehicle) 1 provided in an autonomous traveling system 99 according to one embodiment of the present invention performs work operated by performing wireless communication with a wireless communication terminal 46. is a vehicle. By the user operating the wireless communication terminal 46 and appropriately exchanging signals with the control unit 4 of the tractor 1, the tractor 1 can be caused to travel autonomously and work autonomously.

First, a robot tractor (hereinafter sometimes simply referred to as "tractor") 1 provided in an autonomous traveling system 99 according to an embodiment of the present invention will be described mainly with reference to FIGS. 1 and 2. .

The tractor 1 includes a traveling body (body portion) 2 capable of autonomously traveling within a field (traveling area). A working machine 3 shown in FIGS. 1 and 2 is detachably attached to the traveling body 2 . As the work machine 3, for example, there are various work machines such as a cultivator, a plow, a fertilizer applicator, a lawn mower, and a seed machine. 2 can be installed. The traveling machine body 2 is configured such that the height and attitude of the work machine 3 mounted thereon can be changed.

The configuration of the tractor 1 will be described in more detail with reference to FIGS. 1 and 2. FIG. As shown in FIG. 1, the traveling body 2 of the tractor 1 has a front portion supported by a pair of left and right front wheels (wheels) 7, and a rear portion supported by a pair of left and right rear wheels 8, 8. there is

A bonnet 9 is arranged on the front part of the traveling body 2 . An engine 10 which is a driving source of the tractor 1 and a fuel tank (not shown) are accommodated in the bonnet 9 . The engine 10 can be configured by, for example, a diesel engine, but is not limited to this, and may be configured by, for example, a gasoline engine. Also, an electric motor may be used as the drive source in addition to or instead of the engine.

A cabin 11 for a user to board is arranged behind the bonnet 9 . Inside the cabin 11, there are mainly provided a steering handle 12 for steering operation by the user, a seat 13 on which the user can sit, and various operation devices for performing various operations. However, the work vehicle is not limited to one with the cabin 11 and may be one without the cabin 11 .

2, a monitor device 14, a throttle lever 15, a main speed change lever 27, a plurality of hydraulic control levers 16, a PTO switch 17, a PTO speed change lever 18, an auxiliary speed change lever 19, and a work machine lift switch. 28 etc. can be mentioned as an example. These operating devices are arranged near the seat 13 or near the steering handle 12 .

The monitor device 14 is configured to be able to display various information about the tractor 1 . The throttle lever 15 is an operating tool for setting the output speed of the engine 10 . The main shift lever 27 is an operation tool for changing the running speed of the tractor 1 steplessly. The hydraulic operating lever 16 is an operating tool for switching a hydraulic external extraction valve (not shown). The PTO switch 17 is an operation tool for switching transmission/interruption of power to a PTO shaft (not shown) projecting from the rear end of the transmission 22 (power take-off shaft). That is, when the PTO switch 17 is in the ON state, power is transmitted to the PTO shaft, the PTO shaft rotates, and the working machine 3 is driven. As a result, the PTO shaft does not rotate, and the working machine 3 is stopped. The PTO speed change lever 18 is used to change the power input to the working machine 3, and more specifically, it is an operation tool for changing the rotation speed of the PTO shaft. The sub-transmission lever 19 is an operation tool for switching the gear ratio of the traveling sub-transmission gear mechanism in the transmission 22 . The working machine lifting switch 28 is an operation tool for raising and lowering the height of the working machine 3 mounted on the traveling body 2 within a predetermined range.

As shown in FIG. 1 , a chassis 20 of the tractor 1 is provided below the traveling body 2 . The chassis 20 includes a body frame 21, a transmission 22, a front axle 23, a rear axle 24, and the like.

The body frame 21 is a supporting member in the front part of the tractor 1, and supports the engine 10 directly or via a vibration isolating member or the like. The transmission 22 changes the power from the engine 10 and transmits it to the front axle 23 and the rear axle 24 . The front axle 23 is configured to transmit power input from the transmission 22 to the front wheels 7 . The rear axle 24 is configured to transmit power input from the transmission 22 to the rear wheels 8 . The tractor 1 moves forward by rotating the front wheels 7 and the rear wheels 8 in the forward direction. The tractor 1 moves backward by rotating the front wheels 7 and the rear wheels 8 in the backward direction.

As shown in FIG. 4, the tractor 1 includes a control unit 4 for controlling the operations (forward, backward, stop, turning, etc.) of the traveling body 2 and the operations (lifting, driving, stopping, etc.) of the working machine 3. . The control unit 4 includes a CPU, ROM, RAM, and I/O (not shown), and the CPU can read and execute various programs from the ROM. The control unit 4 is electrically connected to a controller for controlling each component (for example, the engine 10, etc.) provided in the tractor 1, a wireless communication unit 40 capable of wireless communication with other wireless communication devices, and the like. ing.

As the controllers, the tractor 1 includes at least an engine controller, a vehicle speed controller, a steering controller, and an elevation controller (not shown). Each controller can control each component of the tractor 1 according to the electrical signal from the control unit 4 .

The engine controller controls the rotational speed of the engine 10 and the like. Specifically, the engine 10 is provided with a governor device 41 having an unillustrated actuator for changing the rotation speed of the engine 10 . The engine controller can control the rotation speed of the engine 10 by controlling the governor device 41 . The engine 10 is also provided with a fuel injection device 45 that adjusts the injection timing and injection amount of fuel to be injected (supplied) into the combustion chamber of the engine 10 . By controlling the fuel injection device 45 , the engine controller can stop the supply of fuel to the engine 10 and stop driving the engine 10 , for example.

A vehicle speed controller controls the vehicle speed of the tractor 1 . Specifically, the transmission 22 is provided with a transmission 42 that is, for example, a movable swash plate type hydraulic continuously variable transmission. The vehicle speed controller can change the gear ratio of the transmission 22 by changing the angle of the swash plate of the transmission 42 using an actuator (not shown) to achieve a desired vehicle speed.

The steering controller controls the rotation angle of the steering handle 12 . Specifically, a steering actuator 43 is provided at an intermediate portion of the rotating shaft (steering shaft) of the steering handle 12 . With this configuration, when the tractor 1 travels along a predetermined route, the control unit 4 calculates an appropriate rotation angle of the steering handle 12 so that the tractor 1 travels along the route. A control signal is output to the steering controller so as to achieve the rotation angle. The steering controller drives the steering actuator 43 based on the control signal input from the control unit 4 to control the rotation angle of the steering handle 12 .

The lift controller controls the lift of the working machine 3 . Specifically, the tractor 1 includes an elevation actuator 44 such as a hydraulic cylinder in the vicinity of the three-point link mechanism that connects the working machine 3 to the traveling machine body 2 . With this configuration, the elevation controller drives the elevation actuator 44 based on the control signal input from the control unit 4 to appropriately raise and lower the working machine 3, thereby performing agricultural work with the working machine 3 at a desired height. It can be carried out. By this control, the working machine 3 can be supported at a desired height such as a retraction height (a height at which farm work is not performed) and a working height (a height at which farm work is performed).

Note that the plurality of controllers (not shown) described above control each unit such as the engine 10 based on signals input from the control unit 4. Therefore, it is assumed that the control unit 4 substantially controls each unit. can grasp.

The tractor 1 equipped with the control unit 4 as described above controls each part of the tractor 1 (the traveling body 2, the working machine 3, etc.) by the control unit 4 when the user enters the cabin 11 and performs various operations. It is configured so that the farm work can be performed while running in the field. Further, the tractor 1 can be caused to autonomously travel and autonomously work based on a predetermined control signal output from the wireless communication terminal 46 while the user is on or off the tractor 1 . It's becoming

Specifically, as shown in FIG. 4 and the like, the tractor 1 has various configurations for enabling autonomous travel and autonomous work. For example, the tractor 1 is provided with a positioning antenna 6 and the like necessary for acquiring position information of itself (the traveling body 2) based on the positioning system. With such a configuration, the tractor 1 can acquire its own position information based on the positioning system and travel autonomously on the field.

Next, the configuration of the tractor 1 for enabling autonomous travel will be described in more detail. Specifically, the tractor 1 of this embodiment includes a positioning antenna 6, a wireless communication antenna 48, a front camera 56, a rear camera 57, a storage unit 55, a vehicle speed sensor 53, and a An angle sensor 52 and the like are provided. In addition to these, the tractor 1 is equipped with an inertial measurement unit (IMU) capable of specifying the attitude (roll angle, pitch angle, yaw angle) of the traveling body 2 .

The positioning antenna 6 receives signals from positioning satellites that form a positioning system such as the Global Positioning System (GNSS). As shown in FIG. 1 , the positioning antenna 6 is attached to the top surface of the roof 92 of the cabin 11 of the tractor 1 . A positioning signal received by the positioning antenna 6 is input to a position information acquiring section 49 as a position detecting section shown in FIG. The position information acquisition unit 49 calculates and acquires the position information of the traveling body 2 (strictly speaking, the positioning antenna 6) of the tractor 1 as latitude/longitude information, for example. The position information acquired by the position information acquisition unit 49 is input to the control unit 4 and used for autonomous travel.

In this embodiment, a high-precision satellite positioning system using the GNSS-RTK method is used. good too. For example, relative positioning (DGPS) or geostationary satellite augmentation system (SBAS) could be used.

The wireless communication antenna 48 receives signals from the wireless communication terminal 46 operated by the user and transmits signals to the wireless communication terminal 46 . As shown in FIG. 1 , the wireless communication antenna 48 is attached to the upper surface of the roof 92 of the cabin 11 of the tractor 1 . A signal from the wireless communication terminal 46 received by the wireless communication antenna 48 is input to the control unit 4 after signal processing by the wireless communication unit 40 shown in FIG. A signal to be transmitted from the control unit 4 or the like to the wireless communication terminal 46 is processed by the wireless communication unit 40 , transmitted from the wireless communication antenna 48 and received by the wireless communication terminal 46 .

The front camera 56 is for photographing the front of the tractor 1 . The rear camera 57 is for photographing the rear of the tractor 1 . A front camera 56 and a rear camera 57 are mounted on the roof 92 of the tractor 1 . The moving image data captured by the front camera 56 and the rear camera 57 is transmitted from the wireless communication antenna 48 to the wireless communication terminal 46 by the wireless communication unit 40 . The radio communication terminal 46 that has received the moving image data displays the contents on the display 37 .

The vehicle speed sensor 53 detects the vehicle speed of the tractor 1, and is provided on the axle between the front wheels 7, 7, for example. The data of the detection result obtained by the vehicle speed sensor 53 is signal-processed by the wireless communication unit 40, transmitted from the wireless communication antenna 48, received by the wireless communication terminal 46, and displayed on the display 37. be. The steering angle sensor 52 is a sensor that detects the steering angles of the front wheels 7,7. In this embodiment, the steering angle sensor 52 is provided on a kingpin (not shown) provided on the front wheels 7 , 7 . Data of the detection result obtained by the steering angle sensor 52 is output to the control section 4 . Note that the steering angle sensor 52 may be provided on the steering handle 12 .

The storage unit 55 stores the travel route for autonomously traveling the tractor 1 and the work route for autonomous work, and stores the position transition (traveling trajectory) of the tractor 1 (strictly speaking, the positioning antenna 6) during autonomous travel. It is a memory that In addition, the storage unit 55 stores various information necessary for the tractor 1 to travel and work autonomously.

The wireless communication terminal 46 is configured as a tablet personal computer having a touch panel 39, as shown in FIG. The user can refer to and confirm information displayed on the display 37 of the wireless communication terminal 46 (for example, information from the front camera 56, rear camera 57, vehicle speed sensor, etc.). Further, the user operates the touch panel 39 or the hardware keys 38 or the like arranged near the display 37 to send a control signal (for example, temporary stop signal, etc.). The wireless communication terminal 46 is not limited to a tablet-type personal computer, and can be configured by a notebook-type personal computer, for example.

The tractor 1 configured as described above travels along the traveling route P on the field based on the instruction of the user using the wireless communication terminal 46, and performs agricultural work with the working machine 3 along the working route P1. can be done.

Specifically, by performing various settings using the wireless communication terminal 46, the user can set a linear or polygonal work path P1 for agricultural work and an arc-shaped turning path connecting the ends of the work path P1. (Non-work path on which the tractor 1 turns) P2 can be generated as a series of paths P2 alternately (see FIG. 6). Information on the travel route (work route P1 and non-work route P2) P generated in this manner is input (transferred) to the storage unit 55 electrically connected to the control unit 4 of the tractor 1, and a predetermined By operating the tractor 1, the controller 4 controls the tractor 1 so that the tractor 1 can autonomously travel along the travel route P, and the work machine 3 can autonomously work along the work route P1.

The configuration of the wireless communication terminal 46 will be described in more detail below with reference to FIGS. 3 to 6. FIG. FIG. 5 is a diagram showing a display example of the monitor screen 100 on the display 37 of the wireless communication terminal 46. As shown in FIG. FIG. 6 is a schematic diagram showing an example of an autonomous driving route generated by a wireless communication terminal.

As shown in FIGS. 3 and 4, the wireless communication terminal 46 of the present embodiment includes a display 37, hardware keys 38, and a touch panel 39, as well as a display control unit 31 and a storage unit 32 as main components of the control system. , an agricultural field acquisition unit 33, a work area acquisition unit 34, a travel route acquisition unit 35, and the like.

Specifically, the wireless communication terminal 46 is configured as a computer as described above, and includes a CPU, a ROM, a RAM, and the like. Further, the ROM stores appropriate programs for causing the tractor 1 to perform autonomous traveling and autonomous work. The cooperation of this software and hardware allows the wireless communication terminal 46 to operate as the display control unit 31, the storage unit 32, the farm field acquisition unit 33, the work area acquisition unit 34, the traveling route acquisition unit 35, and the like.

The display control unit 31 creates display data to be displayed on the display 37 and appropriately controls display contents. For example, the display control unit 31 displays the monitor screen 100 shown in FIG.

The storage unit 32 stores the information about the tractor 1 and the information about the farm field input by the user by operating the touch panel 39 of the wireless communication terminal 46, and stores the created travel route P (the working route P1 and the non-working route P2). ) is a memory for storing information such as

The agricultural field acquisition unit 33 stores the position and shape of the agricultural field (traveling area) on which the tractor 1 performs autonomous traveling and autonomous work. The position and shape of the field are obtained by, for example, the user riding the tractor 1 and driving the tractor 1 around the circumference of the field and recording the transition of the position information of the positioning antenna 6 at that time. can do. The position and shape of the farm field acquired by the farm field acquisition unit 33 are stored in the storage unit 32 as farm field information.

The work area acquisition unit 34 sets the position of the work area where the tractor 1 performs agricultural work, which is arranged in the target field in which the tractor 1 travels autonomously. Specifically, the wireless communication terminal 46 of the present embodiment is configured to be able to set the width of the headland and the width of the non-cultivated land by performing a predetermined operation. Then, the non-work area consisting of the headland and the non-cultivated land is determined based on the above-described settings and the position and shape of the farm field acquired by the farm field acquisition unit 33. is defined as the work area.

The travel route acquisition unit 35 alternately connects a work route P1 along which the tractor 1 autonomously performs farm work in a field and a non-work route (turning route) P2 that connects the ends of the work route P1. Generate and obtain P. When the user inputs information necessary for generating the travel route P through the touch panel 39 or the like, the travel route acquisition unit 35 automatically creates the travel route P (the work route P1 and the non-work route P2) based on the information. . The travel path P is generated so that the work path P1 in the shape of a straight line or a polygonal line is included in the work area, and the non-work path (turning path) P2 is included in the non-work area such as a headland. The travel route P generated by the travel route acquisition unit 35 is stored in the storage unit 32 .

The user appropriately operates the wireless communication terminal 46 to input (transfer) the information of the travel route P generated by the travel route acquisition unit 35 to the storage unit 55 of the tractor 1 . After that, the user places the tractor 1 at the start position of the travel route P by riding and driving the tractor 1 . Subsequently, the user gets off the tractor 1 and operates the wireless communication terminal 46 to instruct the start of autonomous travel/autonomous work. As a result, the control unit 4 controls the travel and farm work of the tractor 1 so that the tractor 1 travels along the travel route P and performs farm work along the work route P1.

With the start of autonomous travel/autonomous work, the display screen of the display 37 switches to the monitoring screen 100 shown in FIG.

A front camera display section 101 and a rear camera display section 102 for displaying data transmitted from the front camera 56 and the rear camera 57 as moving image data are arranged vertically on the left part of the monitoring screen 100 . In the right part of the monitoring screen 100, there is arranged a work state display section 103 that graphically shows the travel route P and the current position of the tractor 1 in a drawing or the like. A vehicle speed display unit 106 for displaying the current vehicle speed of the tractor 1 is provided above the front camera display unit 101 . The vehicle speed display unit 106 displays the current vehicle speed of the tractor 1 obtained based on the data transmitted from the vehicle speed sensor.

Next, the control for changing the steering angle at the time of switching between forward and backward travel during autonomous travel will be described with reference to FIGS. 7 to 9. FIG. FIG. 7 is a schematic diagram for explaining the flow when switching between forward and backward travel and turning. FIG. 8 is a schematic diagram showing the determination angle θ when the neutral angle is used as the reference angle. FIG. 9 is a flowchart showing a process for changing the steering angle when switching between forward and backward travel.

First, the situation of switching between forward and backward travel during autonomous travel will be described. For example, when the distance between the work paths P1 is narrow and the tractor 1 cannot reach the next work path P1 by only moving forward, the tractor 1 is turned by switching forward and backward. Specifically, first, as shown in the leftmost diagram of FIG. 7, the robot is advanced and turned by approximately 90 degrees toward the next work path P1 (first step), and then reversed as shown in the central diagram of FIG. (Second step), and thereafter, as shown in the rightmost drawing of FIG. Note that the turning angle in the first step is not limited to approximately 90°.

Here, in order to shorten the time required for turning, it is preferable to shorten the switching time when switching from the first process to the second process and the switching time when switching from the second process to the third process. However, when the first step is completed, the steering angle may not be the neutral angle as shown in FIG. Further, in the second step, it is assumed that the steering angle is set to the neutral angle to move backward. Here, when the tractor 1 is stopped and the steering angle is returned to the neutral angle at the time of switching from the first step to the second step (that is, at the time of switching between forward and backward travel), the switching time from the first step to the second step is (that is, the stop time of the tractor 1) becomes long, and switching between forward and backward travel is not performed smoothly.

In this regard, in this embodiment, switching between forward and backward travel can be performed smoothly by performing the control shown in FIG. A specific description will be given below. The control unit 4 determines whether or not it is time to switch between forward and backward travel (S101). between), and it is determined whether or not the steering angle (determination angle) is equal to or less than the first angle (S102). In this embodiment, the neutral angle is used as the reference angle, and the steering angle with respect to the neutral angle is used as the determination angle (the angle used in the determination processing of FIG. 9, etc.). As shown in a modified example, an angle other than the neutral angle may be used as the reference angle. Also, the first angle is, for example, 10 degrees (10 degrees to the left and 10 degrees to the right).

When the control unit 4 determines that the steering angle (determined angle) is equal to or less than the first angle, the control unit 4 stops the tractor 1 and simultaneously switches forward and backward travel (S103). In other words, the controller 4 does not change the steering angle while the tractor 1 is stopped when the steering angle (determined angle) is equal to or smaller than the first angle. Thereafter, if there is a difference between the steering angle and the target angle, the controller 4 changes the steering angle to the target angle (S104).

On the other hand, when the controller 4 determines that the steering angle (determined angle) is greater than the first angle, it stops the tractor 1 (S105). Then, the controller 4 changes the steering angle to the second angle while the tractor 1 is stopped (S106). That is, when the steering angle (determined angle) is greater than the first angle, the control unit 4 changes the steering angle while the tractor 1 is stopped. However, in order to shorten the stop time of the tractor 1, the control unit 4 changes the steering angle so that the judgment angle becomes the second angle instead of the neutral angle. The second angle is a value smaller than the first angle, eg, 2°.

After changing the steering angle to the second angle, the control unit 4 switches forward and backward (S106). After that, the controller 4 changes the steering angle to the target angle (S104).

In this way, by changing the steering angle not during the stop of the tractor 1 but after switching between forward and backward travel, the stopping time of the tractor 1 can be shortened, so that switching between forward and backward travel can be smoothly performed. That is, in this embodiment, even if the steering angle is other than the non-neutral angle, the forward/rearward movement can be switched. Furthermore, when the steering angle at the time of stopping is large, by changing the steering angle to some extent (up to a second angle) while the tractor 1 is stopped, the stopping time of the tractor 1 can be suppressed and the steering angle can be significantly increased after switching between forward and backward travel. You can prevent the corners from being changed. By preventing a large change in the steering angle after switching between forward and backward travel, it is possible to reduce swaying before and after switching between forward and backward travel and to reduce the amount of deviation from the route.

Further, in step S106, the steering angle may be changed to the neutral angle, or the steering angle may be changed to the first angle. Further, in the present embodiment, the process of step S102 is executed before the tractor 1 stops, but may be executed while the tractor 1 is stopped. In this case, the first line of step S103 and step S105 are unnecessary.

Further, in the tractor 1 of the present embodiment, as shown in FIG. 10, the positioning antenna 6 is arranged at a position (front position) off the center of the tractor 1 in the longitudinal direction. Therefore, when moving forward, the position on the traveling direction side of the center of the tractor in the longitudinal direction is used as the current position. It will be done. Therefore, there is a possibility that the autonomous travel control method must be different between forward travel and reverse travel.

Considering this, in the present embodiment, the method of calculating the current position of the tractor 1 is made different when the vehicle is moving in reverse. That is, as shown in FIG. 10, the position of the positioning antenna 6 is virtually corrected so that the positioning antenna 6 is positioned symmetrically with respect to the line passing through the center of the tractor 1 when moving in reverse. As the actual process, the distance L in the front-rear direction from the center of the tractor 1 in the front-rear direction to the positioning antenna 6 is stored in advance. A value offset by twice the distance L is treated as the current position. As a result, the same autonomous travel control method can be used for forward travel and reverse travel.

In the turning method shown in FIG. 7, the rudder angle may not be the neutral angle when the first step is completed, but basically the rudder angle is considered to be the neutral angle when the second step is completed. be done. That is, between the second step and the third step, the forward/rearward travel is switched, so the process of FIG. 9 is executed, but the steering angle change is not required when the forward/rearward travel is switched, so it is not performed. Therefore, in this turning direction, when switching from forward travel to reverse travel, forward and backward travel is switched at a non-neutral angle. On the other hand, by using the control of this embodiment, for example, in the turning method shown in FIG. 11, when switching from reverse to forward, it is possible to switch forward and backward without a neutral angle.

The turning method of FIG. 11 is used when the normal turning method or the turning method of FIG. 7 cannot be used due to, for example, the presence of an obstacle A. Specifically, first, the tractor 1 is moved forward and turned in one direction (leftward) as shown in the left end of FIG. 11 (first step). After that, as shown in the second drawing from the left in FIG. 11, the tractor 1 is moved forward and turned in the other direction (rightward direction) (second step). After that, as shown in the second figure from the right in FIG. 11, it is rotated approximately 90 degrees while moving backward (third step), and then, as shown in the rightmost figure of FIG. 11, it is rotated forward to the next work path P1 ( 4th step). Note that the turning angle in the third step is not limited to 90°. The tractor 1 is moved forward in both the first step and the second step. , the same processing as in FIG. 9 is performed. That is, based on the comparison result between the steering angle (determination angle) and the first angle, the control unit 4 moves the tractor 1 forward without changing the steering angle while the tractor 1 is stopped, or stops the tractor 1 and changes the steering angle. decide to change the Further, since it is preferable to stop immediately after turning in the third step, the steering angle may not be the neutral angle when the third step is completed. Therefore, when using the turning method of FIG. 11, the vehicle is switched from reverse to forward when the steering angle is not at the neutral angle. Therefore, the control unit 4 performs the same processing as in FIG. 9 also between the second step and the third step. That is, based on the comparison result between the steering angle (determination angle) and the first angle, the control unit 4 stops the tractor 1 and at the same time switches it to forward (without changing the steering angle), or stops the tractor 1. Decide whether to change the rudder angle during

Next, the 1st modification of the said embodiment is demonstrated. FIG. 12 is a schematic diagram showing the determination angle θ when the target angle is used as the reference angle. In addition, in the description of the first modified example and the later-described second modified example, members that are the same as or similar to those in the above-described embodiment may be denoted by the same reference numerals in the drawings, and the description thereof may be omitted.

In the above embodiment, since the reference angle is the neutral angle, the steering angle and the judgment angle are the same. However, in the first modified example, the reference angle is an angle other than the neutral angle. As the reference angle in the first modified example, for example, a target steering angle after switching between forward and backward travel can be used. The processing related to the steering angle change at the time of switching between forward and backward travel performed in the first modified example is the same as that of the present embodiment, so the description is omitted.

Next, the 2nd modification of the said embodiment is demonstrated. FIG. 13 is a flow chart showing a process for changing the steering angle at the start of forward/backward travel.

In the above embodiment, the processing for changing the steering angle at the time of switching between forward and backward travel has been described, but the control unit 4 of the second modification also performs the same processing for changing the steering angle at the start of forward and backward travel.

A specific description will be given below. The control unit 4 determines whether or not it is time to start forward and backward movement (S201), and when it is determined that it is time to start forward and backward movement, determines whether or not the steering angle (determination angle) is equal to or less than a third angle (S202). . The third angle is a rudder angle that is a condition for starting forward and backward movement by autonomous travel, and forward and backward movement cannot be started at a steering angle greater than the third angle. The third angle has a larger value than the first angle, but may have a smaller value. Also, the third angle is for example 15°, but may be another value between 10° and 20°.

If the control unit 4 determines that the steering angle is equal to or less than the third angle, it starts forward/backward movement without changing the steering angle (S203). Thereafter, if there is a difference between the steering angle and the target angle, the controller 4 changes the steering angle to the target angle (S204).

On the other hand, when determining that the steering angle is greater than the third angle, the control section 4 changes the steering angle to the second angle without starting forward/rearward travel (S205). After changing the steering angle to the second angle, the control unit 4 starts forward and backward travel (S206). After that, the controller 4 changes the steering angle to the target angle (S204).

As in the above embodiment, in step S205, the steering angle may be changed to the neutral angle, the steering angle may be changed to the target angle, or the steering angle may be changed to the first angle. Further, similarly to the first modification, the reference angle may be other than the neutral angle in the second modification as well.

As described above, the tractor 1 of this embodiment includes wheels (the front wheels 7 and the rear wheels 8) and the controller 4. As shown in FIG. The control unit 4 controls the rotation direction of the rear wheels 8 and the steering angle, which is the turning angle of the front wheels 7, along the travel route. The control unit 4 can change the rotational direction of the rear wheels 8 from the forward direction to the reverse direction or from the reverse direction to the forward direction when the steering angle is a non-neutral angle.

As a result, even when the steering angle is at a non-neutral angle, it is possible to shift from forward to reverse, or vice versa, so that forward and reverse can be switched smoothly.

Further, in the tractor 1 of the present embodiment, when the determination angle, which is the steering angle with respect to the reference angle, is equal to or less than the first angle, the control unit 4 does not change the steering angle while the rotation of the rear wheels 8 is stopped. It is possible to change the rotation direction of the rear wheel 8 from the forward direction to the reverse direction or from the reverse direction to the forward direction.

As a result, if the determined angle is equal to or less than the predetermined first angle, it is possible to smoothly switch between forward and backward travel. Further, by setting the first angle as the threshold value, it is possible to prevent a large change in the steering angle after switching between forward and backward travel.

Further, in the tractor 1 of the present embodiment, the control unit 4 stops the rotation of the rear wheel 8 when the determination angle exceeds the first angle, and the determination angle is the first angle or the second angle smaller than the first angle. After changing the rudder angle so that it becomes an angle, if the rear wheel 8 is rotating in the forward direction, it is changed to the backward direction, and if the rear wheel 8 is rotating in the backward direction, it is changed to the forward direction.

As a result, when the determination angle is large, the steering angle is changed after the vehicle is temporarily stopped, and the forward and backward travel is switched, so that the impact at the time of switching between the forward and backward travel can be reduced.

Moreover, in the tractor 1 of this embodiment, the second angle is a non-neutral angle.

As a result, the forward/reverse switching is performed without reaching the neutral angle, so that the forward/rearward motion can be quickly switched.

Further, in the tractor 1 of this embodiment, after the control unit 4 changes the rotation direction of the rear wheels 8 from the forward direction to the reverse direction or from the reverse direction to the forward direction, there is a difference between the steering angle and the target angle. If so, change the steering angle to the target angle.

As a result, even when there is a difference between the steering angle and the target angle, the steering angle is changed after switching the forward and backward travel of the tractor 1, so that the forward and backward travel can be switched smoothly.

Although the preferred embodiments and modifications of the present invention have been described above, the above configuration can be modified as follows, for example.

In the above-described embodiment and modified example, the process of changing the steering angle either during a stop or after switching between forward and backward travel has been described, but the configuration is such that the steering angle is changed immediately before switching between forward and backward travel and while the vehicle is stopped. Alternatively, the steering angle may be changed while the vehicle is stopped and immediately after switching between forward and backward travel, or the steering angle may be changed from immediately before to immediately after switching between forward and backward travel.

In the above-described embodiment and modified example, the front wheels 7 are the wheels targeted for steering angle change control, and the rear wheels 8 are the wheels targeted for rotational direction control. may be For example, in the case of front-wheel drive or four-wheel drive, the wheels to be controlled are the same in the two controls. Moreover, both the front wheels 7 and the rear wheels 8 may be the wheels to be controlled for changing the steering angle.

1 tractor (work vehicle)
4 control unit 7 front wheel (wheel)

Claims (3)

A work vehicle that autonomously travels along a travel route having a plurality of predetermined work routes and a turning path that connects ends of the work routes and includes switching from forward to reverse or from reverse to forward ,
wheels and
A control unit that controls the direction of rotation of the wheels and the steering angle that is the turning angle of the wheels along the travel route;
with
When the control unit determines that the steering angle at the timing of switching from forward to reverse or from reverse to forward in the turning circuit is equal to or less than a predetermined angle, the steering angle is not a neutral angle, and the direction of rotation of the wheels is changed. can be changed from the forward direction to the reverse direction or from the reverse direction to the forward direction. The work vehicle according to claim 1,
A work vehicle, wherein the predetermined angle or less is a case where a judgment angle, which is a steering angle with respect to a neutral angle of the wheels, is equal to or less than a first angle. The work vehicle according to claim 1 or 2,
The turning path includes a straight path and a forward turning path that is a path that turns while moving forward,
The control unit is capable of changing the rotation direction of the wheel from the forward direction to the reverse direction when switching from the forward turning circuit to the straight turning circuit, and switching from the straight turning circuit to the forward turning circuit. A work vehicle characterized in that it is possible to change the rotation direction of the wheels from the backward direction to the forward direction when the vehicle is moving.

Images