Autonomous driving system and method

Abstract

To prevent an erroneous detection of an orientation of a work vehicle when a predetermined process of an inertial measurement device is performed by intentionally changing a position of the work vehicle.SOLUTION: An automatic travel system comprises a control unit 4. The control unit 4 can cause a tractor 1 to travel automatically based on positional information of the tractor 1, which can perform both an automatic travel and a manual travel. The automatic travel system includes a state in which an orientation of the tractor 1 is specified as a condition for causing the tractor 1 to travel automatically. The orientation of the tractor 1 is specified during manual travel of the tractor 1.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an automated driving system and an automated driving method. [Background technology]

[0002] Conventionally, autonomous driving systems have been known that acquire position information for a work vehicle based on radio waves received from GNSS satellites and autonomously drive the work vehicle along a predetermined route. Patent Document 1 discloses this type of autonomous driving system (driving control system). The autonomous driving system described in Patent Document 1 can start autonomous driving by positioning the work vehicle to be driven autonomously with its forward direction facing a predetermined direction relative to the starting position of a predetermined route. To achieve such autonomous driving, it is considered necessary for the orientation of the work vehicle to be known by the autonomous driving control device that drives the work vehicle autonomously.

[0003] One possible method for obtaining the orientation of a work vehicle is to equip the work vehicle with a known inertial measurement unit (IMU) equipped with three gyro sensors (angular velocity sensors) and three acceleration sensors. This IMU uses the gyro sensors to detect the angular velocity of rotation around each of three mutually orthogonal axes, and the acceleration sensors to detect the acceleration along these three axes. The IMU is mounted so that these three axes are parallel to the vehicle's pitch axis, roll axis, and yaw axis, respectively. With this configuration, by integrating the angular velocities obtained from a certain point in time to the present, the amount of change in the orientation of the work vehicle relative to that point in time can be obtained.

[0004] When the autonomous driving control device performs autonomous driving, the position of the work vehicle is basically determined from position information obtained by GNSS positioning, but there are cases where positioning cannot be performed satisfactorily depending on the reception conditions of GNSS radio waves, etc. However, if the work vehicle is equipped with the above-mentioned inertial measurement unit, the position of the work vehicle can be obtained by inertial navigation using the detection results of the inertial measurement unit even when GNSS positioning is not possible.

[0005] Incidentally, the gyro sensor of the inertial measurement unit can detect changes in the orientation of the work vehicle, but cannot detect the orientation itself. Therefore, the inertial measurement unit must know the vehicle's attitude at a given point in time, specifically the pitch angle, roll angle, and yaw angle. Note that, hereinafter, the process of determining at least the yaw angle of the above three angles may be referred to as the initialization process.

[0006] As mentioned above, the inertial measurement unit is equipped with an acceleration sensor. Taking advantage of the fact that gravitational acceleration always points toward the center of the Earth, the pitch angle and roll angle of the vehicle can be determined by determining the direction of gravitational acceleration using the acceleration sensor, for example, while the vehicle is stationary. On the other hand, the yaw angle of the vehicle cannot, in principle, be determined using the sensors provided in the inertial measurement unit.

[0007] Although a technology has been put into practical use that uses a gyro sensor to detect the rotation of the Earth to determine the yaw angle (gyrocompass), this method requires a highly accurate gyro sensor, which increases the cost of the inertial measurement unit. Also, while it is conceivable to install a direction sensor on the work vehicle, as in Patent Document 1, this also increases costs.

[0008] Therefore, by taking advantage of the fact that the work vehicle is equipped with a configuration that can receive radio waves from GNSS satellites, it is possible to have the user manually drive the work vehicle forward, detect changes in the vehicle's position relative to the Earth based on the radio waves from the GNSS satellites, and consider the direction in which this position has changed to be the direction of the vehicle, thereby calculating the vehicle's yaw angle. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2015 / 119265 Summary of the Invention [Problem to be solved by the invention]

[0010] However, with the above configuration, when the user actually moves the work vehicle for the initialization process, there may be cases where the work vehicle must temporarily move in reverse instead of forward due to various circumstances, such as the presence of an obstacle ahead. In such cases, there is a risk that the orientation of the work vehicle may be determined to be 180 degrees different from the actual orientation, resulting in erroneous initialization, which could cause unintended control to be performed, leaving room for improvement.

[0011] The present invention has been made in consideration of the above circumstances, and its purpose is to prevent erroneous detection of the orientation of a work vehicle when performing predetermined processing of an inertial measurement unit while intentionally changing the position of the work vehicle in an automated driving system. [Means for solving the problem]

[0012] An automated driving system according to one aspect of the present invention includes a control unit. The control unit is capable of causing a work vehicle capable of both automated and manual driving to drive automatically based on position information of the work vehicle. The automated driving system includes a condition for causing the work vehicle to drive automatically that specifies the orientation of the work vehicle. The orientation of the work vehicle is specified when the work vehicle is manually driven. In one aspect of the present invention, an automatic driving method includes specifying a direction of a work vehicle that is capable of both automatic and manual driving based on position information of the work vehicle. The direction of the work vehicle is specified when the work vehicle is manually driven. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a side view showing the overall configuration of a robot tractor provided in an autonomous driving system according to an embodiment of the present invention. [Figure 2] FIG. 1 is a plan view of a robot tractor. [Figure 3]FIG. 2 is a block diagram showing the main electrical configuration of the robot tractor. [Figure 4] 5 is a flowchart illustrating the determinations and processes performed in the initialization process of the inertial measurement unit in the first embodiment. [Figure 5] 10 is a flowchart illustrating the determinations and processes performed in the initialization process of the inertial measurement unit in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Next, an embodiment of the present invention will be described with reference to the drawings. In the following, the same components in each drawing will be assigned the same reference numerals, and duplicate explanations may be omitted. In addition, the names of components corresponding to the same reference numerals may be rephrased in a simplified manner or rephrased with names of higher or lower concepts.

[0015] The present invention is applied to an autonomous driving system that autonomously drives one or more work vehicles within a predetermined field to perform all or part of agricultural work within the field, as shown in the following embodiments, for example. In this embodiment, a tractor is used as an example of the work vehicle. However, work vehicles include not only tractors but also ride-on and walk-behind work machines such as rice transplanters, combine harvesters, civil engineering and construction work equipment, and snowplows. In this specification, autonomous driving refers to the tractor's control unit (ECU) controlling the tractor's driving-related components and causing the tractor to drive along a predetermined route. Autonomous operation refers to the tractor's control unit controlling the tractor's work-related components and causing the tractor to work along a predetermined route. In contrast, manual driving and manual operation refer to the tractor's driving and work being performed by a user operating each component of the tractor.

[0016] In the following description, an autonomously driven and operated tractor may be referred to as an "unmanned tractor" or "robot tractor," and a manually driven and operated tractor may be referred to as a "manned tractor." When part of a farm task in a field is performed by an unmanned tractor, the remaining task is performed by a manned tractor. Performing farm tasks in a single field with an unmanned tractor and a manned tractor may be referred to as cooperative farming, following work, accompanying work, etc. In this specification, the difference between an unmanned tractor and a manned tractor is whether or not it is operated by a user, and the configuration of each is basically the same. That is, even an unmanned tractor can be operated by a user while riding (i.e., can be used as a manned tractor), or even a manned tractor can be operated by a user while dismounting (i.e., can be used as an unmanned tractor). In addition, cooperative agricultural work may include not only "agricultural work being performed in a single field by unmanned vehicles and manned vehicles," but also "agricultural work being performed in different fields, such as adjacent fields, by unmanned vehicles and manned vehicles at the same time."

[0017] First Embodiment Next, a first embodiment 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 driving system 100 according to one embodiment of the present invention. Fig. 2 is a plan view of the robot tractor 1. Fig. 3 is a block diagram showing the main electrical configuration of the robot tractor 1.

[0018] The robot tractor 1 of this embodiment is configured to perform autonomous work while autonomously traveling along an autonomous traveling route (path) generated by the autonomous traveling system 100.

[0019] The robot tractor 1 is operated by wireless communication with the wireless communication terminal 46 via a short-range wireless network. The user operates the touch panel 39 of the wireless communication terminal 46 to appropriately exchange signals with the control unit (autonomous driving control unit) 4 of the tractor 1, thereby allowing the tractor 1 to drive and work autonomously.

[0020] The tractor 1 is equipped with a traveling machine body 2 that can travel autonomously within a field. A work implement 3 shown in Figures 1 and 2 is detachably attached to the traveling machine body 2. This work implement 3 includes various types of implements, such as cultivators, plows, fertilizer applicators, mowers, and seed sowing machines, and a desired work implement 3 can be selected from these as needed and attached to the traveling machine body 2. The traveling machine body 2 is configured so that the height and posture of the attached work implement 3 can be changed.

[0021] The configuration of the tractor 1 will be described in more detail with reference to Figures 1 and 2. As shown in Figure 1, the traveling body 2 of the tractor 1 has its front part supported by a pair of left and right front wheels 7, 7 and its rear part supported by a pair of left and right rear wheels 8, 8.

[0022] A hood 9 is disposed at the front of the traveling machine body 2. Inside this hood 9, an engine 10, which is the drive source of the tractor 1, is housed. This engine 10 may be configured as, for example, a diesel engine, but is not limited to this and may also be configured as, for example, a gasoline engine. Furthermore, an electric motor may be used as the drive source in addition to or instead of the engine 10.

[0023] A cabin 11 for the user to board is located behind the hood 9. Inside this cabin 11, mainly provided are a steering handle 12 for the user to steer, a seat 13 in which the user can sit, and various operating devices for performing various operations. However, the work vehicle is not limited to one with a cabin 11, and may not be equipped with a cabin 11.

[0024] Examples of the operating devices include the monitor device 14, throttle lever 15, main speed change lever 27, multiple hydraulic control levers 16, PTO switch 17, PTO speed change lever 18, sub-speed change lever 19, and work equipment lift switch 28, all of which are shown in Fig. 2. These operating devices are located near the seat 13 or the steering handle 12.

[0025] The monitor device 14 is configured to be able to display various information about the tractor 1. The throttle lever 15 is an operating device for setting the output speed of the engine 10. The main speed change lever 27 is an operating device for continuously changing the traveling mode of the tractor 1. The PTO switch 17 is an operating device for switching between transmitting and cutting off power to a PTO shaft (power take-off shaft) (not shown) protruding from the rear end of the transmission 22. That is, when the PTO switch 17 is in the ON position, power is transmitted to the PTO shaft, causing the PTO shaft to rotate and drive the work implement 3. On the other hand, when the PTO switch 17 is in the OFF position, power to the PTO shaft is cut off, causing the PTO shaft to not rotate and stopping the work implement 3. The PTO speed change lever 18 is used to change the power input to the work implement 3, and more specifically, is an operating device for changing the rotational speed of the PTO shaft. The sub-speed change lever 19 is an operating device for changing the gear ratio of a traveling sub-speed change gear mechanism in the transmission 22. The work implement lifting switch 28 is an operating tool for lifting or lowering the height of the work implement 3 attached to the traveling machine body 2 within a predetermined range.

[0026] As shown in Fig. 1, a chassis 20 of the tractor 1 is provided below the traveling body 2. The chassis 20 is made up of a body frame 21, a transmission 22, a front axle 23, a rear axle 24, and the like.

[0027] The machine frame 21 is a support member at the front of the tractor 1, and supports the engine 10 directly or via a vibration-damping member or the like. The transmission 22 changes the power from the engine 10 and transmits it to a front axle 23 and a rear axle 24. The front axle 23 is configured to transmit the power input from the transmission 22 to the front wheels 7. The rear axle 24 is configured to transmit the power input from the transmission 22 to the rear wheels 8.

[0028] As shown in Fig. 3, the tractor 1 is equipped with a control unit 4 for controlling the operation (forward, backward, stopping, turning, etc.) of the traveling machine body 2 and the operation (lifting, lowering, driving, stopping, etc.) of the work implement 3. The control unit 4 is configured with a CPU, ROM, RAM, I / O, etc. (not shown), and the CPU can read and execute various programs from the ROM. A controller for controlling each component (for example, the engine 10, etc.) of the tractor 1, and a wireless communication device for wireless communication with other wireless communication devices, etc. are electrically connected to the control unit 4 via a standard such as CAN.

[0029] As the above-mentioned controllers, the tractor 1 is equipped with at least an engine controller 41, a vehicle speed controller 42, a steering controller 43, and a lift controller 44. Each controller can control each component of the tractor 1 in response to an electrical signal from the control unit 4.

[0030] The engine controller 41 controls the rotation speed and other parameters of the engine 10. The engine controller 41 is electrically connected to a common rail device (not shown) serving as a fuel injection device provided in the engine 10. The common rail device injects fuel into each cylinder of the engine 10. In this case, by controlling the opening and closing of fuel injection valves of injectors for each cylinder of the engine 10, high-pressure fuel pumped from a fuel tank to the common rail device by a fuel supply pump is injected from each injector into each cylinder of the engine 10, and the injection pressure, injection timing, and injection period (injection amount) of the fuel supplied from each injector are controlled with high precision. By controlling the common rail device, the engine controller 41 can, for example, stop the supply of fuel to the engine 10 and stop the operation of the engine 10.

[0031] The vehicle speed controller 42 controls the vehicle speed of the tractor 1. Specifically, the transmission 22 is provided with, for example, a variable swash plate type hydraulic continuously variable transmission (not shown). The vehicle speed controller 42 can change the gear ratio of the transmission 22 and achieve a desired vehicle speed by changing the angle of the swash plate of the hydraulic continuously variable transmission using an actuator.

[0032] The steering controller (traveling device) 43 controls the rotation angle of the steering wheel 12. Specifically, a steering actuator is provided midway through the rotation angle (steering shaft) of the steering wheel 12. With this configuration, when the tractor 1 (as an unmanned tractor) travels along a predetermined route, the control unit 4 calculates an appropriate rotation angle of the steering wheel 12 so that the tractor 1 travels along the route, and outputs a control signal to the steering controller 43 to achieve the obtained rotation angle. The steering controller 43 drives the steering actuator based on the control signal input from the control unit 4, and controls the rotation angle (steering angle) of the steering wheel 12. Note that the steering controller 43 may directly adjust the rudder angle of the front wheels 7 of the tractor 1 rather than adjusting the rotation angle of the steering wheel 12. In that case, the steering wheel 12 does not rotate even when the tractor 1 is turning.

[0033] The lift controller 44 controls the lifting and lowering of the work implement 3. Specifically, the tractor 1 is equipped with a lift actuator (not shown) made up of a hydraulic cylinder or the like, near the three-point linkage that connects the work implement 3 to the traveling body 2. With this configuration, the lift controller 44 drives the lift actuator based on a control signal input from the control unit 4 to appropriately lift and lower the work implement 3, thereby enabling the work implement 3 to perform agricultural work at a desired height. Through this control, the work implement 3 can be supported at a desired height, such as a retraction height (a height at which agricultural work is not performed) or a working height (a height at which agricultural work is performed).

[0034] Furthermore, since the above-mentioned multiple controllers 41, 42, 43, and 44 control each part such as the engine 10 based on signals input from the control unit 4, it can be understood that the control unit 4 is essentially aware of each part.

[0035] The tractor 1 equipped with the control unit 4 as described above is configured so that a user can ride in the cabin 11 and perform various operations, thereby controlling each part of the tractor 1 (traveling body 2, work implement 3, etc.) with the control unit 4, and perform agricultural work while traveling in a field. In addition, the tractor 1 of this embodiment can perform autonomous traveling and autonomous work based on predetermined control signals output from the wireless communication terminal 46, even if a user does not ride in the tractor 1.

[0036] Specifically, as shown in Fig. 3 etc., the tractor 1 is equipped with various components for enabling autonomous driving and autonomous work. For example, the tractor 1 is equipped with a positioning antenna 6 etc. necessary for constantly acquiring position information of the tractor itself (the traveling body 2) based on radio waves received from satellites (positioning satellites) 105, 105, .... With this configuration, the tractor 1 is able to acquire its own position information based on radio waves received from the satellites 105, 105, ... and autonomously drive along a predetermined route in the field.

[0037] Next, a more detailed description will be given of the configuration of the tractor 1 that enables autonomous traveling. Specifically, as shown in Fig. 3 etc., the tractor 1 of this embodiment includes a positioning antenna 6, a position information acquisition unit 52, a wireless communication antenna 48, a short-range wireless communication device 51, a camera 56, an inertial measurement unit 54, a memory unit 55, etc.

[0038] The positioning antenna 6 receives radio waves from satellites 105, 105, ... that make up a global positioning satellite system (GNSS). In this embodiment, the global positioning system (GPS) is used as the GNSS. As shown in Fig. 1, the positioning antenna 6 is attached to the upper surface of the roof 26 of the cabin 11 of the tractor 1.

[0039] The position information acquisition unit 52 acquires position information (latitude and longitude information) based on the input positioning signal using the well-known GNSS-RTK method. Since the GNSS-RTK method is well-known, detailed description is omitted. However, the position information acquisition unit 52 acquires position information by performing its own positioning and also receives positioning correction information acquired (calculated) by a reference station whose position is known via wireless communication from time to time. The position information acquisition unit 52 corrects the position information based on this positioning correction information. Furthermore, the position information acquisition unit 52 and the reference station perform measurements based not only on data (navigation messages) received via GNSS radio waves but also on the detection of the phase of the GNSS radio waves (carrier waves) as waves. This allows the position information of the traveling vehicle 2 to be acquired with significantly higher accuracy than conventional GNSS positioning, specifically with an error of approximately several centimeters. The position information acquired by the position information acquisition unit 52 is stored in the memory unit 55 and is also read from the memory unit 55 as needed and input to the control unit 4 for use in autonomous traveling.

[0040] The wireless communication antenna 48 is an antenna compatible with the standards of a short-range wireless network used for communication with the wireless communication terminal 46 used by the user. The wireless communication antenna 48 is disposed on the upper surface of the roof 26 of the cabin 11 of the tractor 1. A signal received by the wireless communication antenna 48 from the wireless communication terminal 46 is processed by the short-range wireless communication device 51 and then input to the control unit 4. In addition, a signal to be transmitted from the control unit 4, etc. to the wireless communication terminal 46 is processed by the short-range wireless communication device 51, then transmitted from the wireless communication antenna 48 and received by the wireless communication terminal 46.

[0041] The short-range wireless communication device 51 demodulates and extracts the signal received by the wireless communication antenna 48 from the wireless communication terminal 46, and inputs the signal to the control unit 4. As a result, instructions issued by the user using the wireless communication terminal 46 are input to the control unit 4 and used to control each part of the tractor 1.

[0042] The camera 56 captures images of the environment around the tractor 1. Although not shown in FIGS. 1 and 2, the camera 56 is attached to the roof 26 of the tractor 1. The image data captured by the camera 56 is modulated by the short-range wireless communication device 51, then transmitted from the wireless communication antenna 48, and received by the wireless communication terminal 46. Based on this received image data, display data is generated by the display control unit 31 of the wireless communication terminal 46, and the image captured by the camera 56 is displayed on the display 37 based on the display data.

[0043] The memory unit 55 is a memory that stores a predetermined route (driving route) for the tractor 1 to travel autonomously, and stores position information (position information, speed vector information, etc.) of the tractor 1 (strictly speaking, the positioning antenna 6).

[0044] The inertial measurement unit 54 is a sensor unit capable of identifying the attitude, acceleration, etc. of the traveling body 2 of the tractor 1. Specifically, the inertial measurement unit 54 includes a sensor group in which an angular velocity sensor and an acceleration sensor are attached to each of a first axis, a second axis, and a third axis that are orthogonal to each other.

[0045] More specifically, the inertial measurement unit 54 includes a first acceleration sensor that detects acceleration in a first axis direction, a second acceleration sensor that detects acceleration in a second axis direction, a third acceleration sensor that detects acceleration in a third axis direction, a first angular velocity sensor that detects angular velocity around the first axis, a second angular velocity sensor that detects angular velocity around the second axis, and a third angular velocity sensor that detects angular velocity around the third axis.

[0046] The inertial measurement unit 54 is attached to the center of gravity of the traveling body 2 of the tractor 1, with its direction determined relative to the traveling body 2 so that the first angular velocity sensor can detect the roll angular velocity of the tractor 1, the second angular velocity sensor can detect the pitch angular velocity of the tractor 1, and the third angular velocity sensor can detect the yaw angular velocity of the tractor 1. In other words, the first axis is arranged to coincide with the front-to-rear direction of the traveling body 2, i.e., to be the roll rotation axis. The second axis is arranged to coincide with the left-to-right direction of the traveling body 2, i.e., to be the pitch rotation axis. The third axis is arranged to coincide with the up-and-down direction of the traveling body 2, i.e., to be the yaw rotation axis.

[0047] The detection results of the inertial measurement device 54 configured as described above make it possible to identify the angular velocities (roll angular velocity, pitch angular velocity, and yaw angular velocity) of the attitude change of the traveling body 2 of the tractor 1, as well as the acceleration in the front-to-back, left-to-right, and up-to-down directions. The result of integrating the obtained angular velocities is then used to acquire the attitude of the traveling body 2. Information regarding the attitude of the traveling body 2 is input to the control unit 4 and used to correct the position information acquired by the position information acquisition unit 52, and for other control purposes.

[0048] In addition, by performing known inertial navigation calculations using information regarding the attitude changes and acceleration of the traveling body 2 acquired by the inertial measurement device 54, the position of the tractor 1 during times when radio waves from satellites 105, 105, ... are temporarily interrupted and position information cannot be calculated can be determined.

[0049] In order for the tractor 1 configured in this way to perform appropriate autonomous driving, it is not enough for the control unit 4 to accurately grasp the position information of the tractor 1; it is also necessary for the control unit 4 to accurately grasp the orientation of the tractor 1 (traveling body 2). In this regard, the angular velocity sensor of the inertial measurement unit 54 can detect changes in the orientation of the tractor 1, but cannot detect the orientation of the tractor 1 itself.

[0050] As mentioned above, the roll angle and pitch angle of the traveling body 2 can be determined by detecting the direction of the gravitational acceleration acting on the tractor 1 while it is stopped (stationary) using three acceleration sensors, but the yaw angle cannot be determined using the gravitational acceleration as a clue. Note that it is conceivable to equip the tractor 1 with a known compass, such as an electronic compass or a mechanical gimbal compass, in order to determine the yaw angle, but this would increase costs.

[0051] Therefore, in this embodiment, the tractor 1 is actually moved forward by manual operation by the user, and the change in position of the tractor 1 at this time is determined using GNSS radio waves, and the yaw angle is determined based on the direction of the change in position. Details of this predetermined process (hereinafter sometimes referred to as initialization process) will be described later.

[0052] If initial values ​​for the attitude (roll angle, pitch angle, and yaw angle) of the tractor 1 are given in this way, as long as subsequent changes in the direction of the tractor 1 are continuously detected by the angular velocity sensor, the current attitude of the tractor 1 can be obtained in real time by adding the integrated result of the detected value of the angular velocity sensor to the initial value. Even if GNSS positioning is not possible, the position of the tractor 1 can be estimated by known inertial navigation based on the attitude of the tractor 1 and the detection result of the acceleration sensor.

[0053] 3, the configuration provided in autonomous driving system 100 for making various determinations associated with the initialization process of inertial measurement unit 54. Specifically, autonomous driving system 100 of this embodiment includes forward / reverse motion detection unit 53, steering angle detection unit (turning detection unit) 57, vibration detection unit 58, and vehicle speed detection unit 59.

[0054] The forward / reverse detection unit 53 detects the rotation of the front wheels 7, thereby detecting whether the tractor 1 is moving forward, moving backward, or in a neutral state (when the tractor 1 is not moving forward or backward). The detection result of the forward / reverse detection unit 53 is input to the control unit 4.

[0055] The steering angle detection unit 57 detects the steering angle of the steering wheel 12. Various known sensors can be used as the steering angle detection unit 57, but it can be configured, for example, by a rotary potentiometer. The detection result of the steering angle detection unit 57 is input to the control unit 4.

[0056] The vibration detection unit 58 detects vibrations of the traveling machine body 2 of the tractor 1. Specifically, the vibration detection unit 58 of this embodiment reads out the detection values ​​of the three acceleration sensors of the inertial measurement unit 54 from the storage unit 55 and comprehensively evaluates these values ​​to detect vibrations of the traveling machine body 2. The detection result of the vibration detection unit 58 is input to the control unit 4.

[0057] The vehicle speed detection unit (vehicle speed determination unit) 59 detects the vehicle speed (travel speed) of the tractor 1. There are various methods for detecting the vehicle speed, but one possible method is to provide a rotation sensor (not shown) facing the outer periphery of a gear (not shown) arranged inside the transmission 22, and count pulse signals that the rotation sensor detects and outputs when it detects gear teeth. The vehicle speed information acquired by the vehicle speed detection unit 59 is input to the control unit 4.

[0058] The initialization process of the inertial measurement unit 54 performed in the autonomous driving system 100 of this embodiment will be described in detail below with reference to FIG. 4. FIG. 4 is a flowchart illustrating the determinations and processes performed in the initialization process of the inertial measurement unit 54 of this embodiment. The series of determinations and processes shown in FIG. 4 are performed when the tractor 1 is started (specifically, when an engine switch (not shown) is turned on). In other words, the series of determinations and processes shown in FIG. 4 are performed each time the tractor 1 is started. As a result, even if the orientation of the tractor 1 changes due to transportation or the like while there is no power supply to the inertial measurement unit 54, the inertial measurement unit 54 can be properly initialized for the changed orientation of the tractor 1.

[0059] When the tractor 1 is started, the control unit 4 displays a message saying "For initialization, please move the tractor forward as straight as possible" on the monitor device 14 provided in the tractor 1. Seeing this, the user operates the throttle lever 15, the main speed change lever 27, etc. to move the tractor 1 forward.

[0060] First, the control unit 4 acquires the detection result of the forward / reverse movement detection unit 53 and determines whether or not the forward movement of the traveling machine body 2 is detected (step S101).

[0061] If the result of the judgment in step S101 is that the forward / reverse movement detection unit 53 has not detected the forward movement of the running body 2 (step S101, No), the control unit 4 repeatedly makes the judgment and waits until the forward movement of the running body 2 is detected.

[0062] If the result of the judgment in step S101 is that the forward / reverse movement detection unit 53 detects the forward movement of the running body 2 (step S101, Yes), the control unit 4 then acquires the detection result of the vehicle speed detection unit 59 and determines whether the vehicle speed of the running body 2 exceeds the threshold value (step S102).

[0063] If the result of the determination in step S102 is that the vehicle speed detected by the vehicle speed detection unit 59 is equal to or lower than the threshold value (step S102, No), it is considered that the influence of errors described below on the direction of the detected vehicle speed becomes relatively large, and therefore it is not possible to accurately obtain the direction of the traveling machine body 2. In this case, the control unit 4 returns to step S101 and repeats the above-mentioned determination.

[0064] If the result of the judgment in step S102 is that the vehicle speed detected by the vibration detection unit 58 exceeds the threshold value (step S102, Yes), the control unit 4 then acquires the detection result of the vibration detection unit 58 and determines whether the magnitude of the vibration of the running body 2 is less than the threshold value (step S103).

[0065] If the result of the determination in step S103 is that the magnitude of the vibration detected by the vibration detection unit 58 is equal to or greater than the threshold value (step S103, No), the behavior of the traveling machine body 2 is unstable, and it may be impossible to accurately obtain the orientation of the traveling machine body 2. In this case, the control unit 4 returns to step S101 and repeats the above-mentioned determination.

[0066] If the result of the judgment in step S103 is that the magnitude of the vibration detected by the vibration detection unit 58 is less than the threshold value (step S103, Yes), the control unit 4 then acquires the detection result of the steering angle detection unit 57 and judges whether the steering angle of the steering wheel 12 is less than the threshold value (step S104).

[0067] If the result of the determination in step S104 is that the steering angle detected by the steering angle detection unit 57 is equal to or greater than the threshold value (step S104, No), there is a possibility that the orientation of the traveling machine body 2 is changing rapidly and therefore it is not possible to accurately obtain the orientation of the traveling machine body 2. In this case, the control unit 4 returns to step S101 and repeats the above-mentioned determination.

[0068] If the result of the determination in step S104 is that the magnitude of the steering angle detected by the steering angle detection unit 57 is less than the threshold value (step S104, Yes), it can be said that the conditions for accurately detecting the orientation of the traveling machine body 2 are met. Therefore, the control unit 4 performs initialization processing (step S105).

[0069] To explain the processing of step S105 in detail, the control unit 4 calculates the velocity vector of the running vehicle 2 based on the velocity of the satellites 105, 105, ..., which is determined from the satellite orbit information of the navigation message carried on the GNSS radio waves received from the satellites 105, 105, ..., and the relative velocity of the running vehicle 2 with respect to the satellites 105, 105, ..., which is determined by measuring the frequency change of the carrier wave caused by the Doppler effect when the GNSS radio waves are received.

[0070] When using GPS as the GNSS, there are multiple types of GPS carrier waves. For example, when measuring a carrier wave called L1 (1575.42 MHz), its wavelength is approximately 19 centimeters. Therefore, by measuring the wave properties of the carrier wave (Doppler effect) as described above, it is possible to measure the change in distance between the satellites 105, 105, ... and the traveling vehicle 2 with high accuracy, with an error of several centimeters per second. Therefore, if the traveling vehicle 2 is traveling at a certain speed or higher (step S102), its velocity vector can be obtained with sufficiently high accuracy.

[0071] As described above, it is conceivable that the user may move the tractor 1 backward to avoid an obstacle or for other reasons, when the user should move the tractor 1 forward according to the display on the monitor device 14. However, in this embodiment, when backward movement is detected, the control unit 4 controls so that the initialization process is not performed (step S101), so that the initialization process is not performed when the direction of the velocity vector and the direction of the traveling body 2 are opposite. This increases the reliability of the detection results of the inertial measurement unit 54.

[0072] The obtained velocity vector can be represented by a north velocity component, an east velocity component, and a downward velocity component. The yaw angle (initial yaw angle) for initializing the inertial measurement unit 54 can be calculated by calculating the arctangent of the ratio of the east velocity component to the north velocity component.

[0073] In this way, in this embodiment, the yaw angle for initializing the inertial measurement unit 54 can be obtained with high accuracy by utilizing the Doppler effect of GPS radio waves. Therefore, it is expected that the attitude of the traveling vehicle 2 output by the inertial measurement unit 54 based on this will also be highly accurate, and position determination by inertial navigation, which is performed when GNSS-RTK positioning is no longer possible, can be performed with an accuracy that allows it to be substituted for GNSS-RTK positioning.

[0074] As described above, the autonomous driving system 100 of this embodiment includes the position information acquisition unit 52, the control unit 4, the forward / reverse movement detection unit 53, and the inertial measurement unit 54. The position information acquisition unit 52 acquires position information of the tractor 1 based on radio waves received from the satellites 105, 105, .... The control unit 4 can autonomously drive the tractor 1 along a predetermined route based on the position information. The forward / reverse movement detection unit 53 can detect whether the tractor 1 is moving forward or backward. The inertial measurement unit 54 detects the angular velocity and acceleration of the tractor 1. By performing an initialization process while moving the tractor 1, the inertial measurement unit 54 can determine the orientation of the tractor 1 at the time of execution of the initialization process based on the direction of the change in position of the tractor 1 obtained based on the radio waves received from the satellites 105, 105, .... The inertial measurement unit 54 performs the initialization process when the forward / reverse movement detection unit 53 detects forward movement, but does not perform the initialization process when the forward / reverse movement detection unit 53 detects reverse movement.

[0075] As a result, the inertial measurement unit 54 does not execute the initialization process when the tractor 1 is moving backward, which prevents erroneous initialization that would otherwise result in the orientation of the tractor 1 being determined to be 180° different from the actual orientation. As a result, the reliability of the detection results by the inertial measurement unit 54 can be improved.

[0076] Furthermore, the autonomous driving system 100 of this embodiment includes a steering angle detection unit 57 that detects the degree of turning of the tractor 1. The inertial measurement unit 54 does not execute initialization processing when the degree of turning (specifically, the steering angle) detected by the steering angle detection unit 57 exceeds a threshold value.

[0077] This prevents the inertial measurement unit 54 from performing initialization processing when, for example, the tractor 1 turns to avoid an obstacle and the orientation of the tractor 1 changes suddenly, making it difficult to accurately determine the orientation of the tractor 1. Therefore, initialization processing based on an inaccurate orientation of the work vehicle can be prevented.

[0078] Furthermore, the autonomous driving system 100 of this embodiment includes a vibration detection unit 58 that detects vibrations of the tractor 1. The inertial measurement unit 54 does not execute the initialization process when the vibrations detected by the vibration detection unit 58 exceed a threshold value.

[0079] This makes it possible to prevent the inertial measurement unit 54 from performing initialization processing when the vibrations generated in the tractor 1 are large and it is difficult to obtain the orientation of the tractor 1 with high accuracy.

[0080] Furthermore, the autonomous driving system 100 of this embodiment includes a vehicle speed detection unit (vehicle speed determination unit) 59 that determines the vehicle speed of the tractor 1. The inertial measurement unit 54 does not execute the initialization process when the vehicle speed determined by the vehicle speed detection unit 59 is less than a threshold value.

[0081] This makes it possible to prevent the inertial measurement unit 54 from performing initialization processing when the vehicle speed is slow and it is difficult to accurately obtain the direction of the change in position of the tractor 1.

[0082] Second Embodiment Next, a second embodiment of the present invention will be described with reference to Fig. 5. Fig. 5 is a flowchart illustrating the determinations and processing performed in the initialization processing of the inertial measurement unit 54 in the second embodiment. In the description of this embodiment, components that are the same as or similar to those in the previous embodiment are given the same reference numerals in the drawings, and their description may be omitted.

[0083] The autonomous driving system 100 according to the second embodiment differs from the autonomous driving system 100 according to the first embodiment in that the initialization process can be performed not only when the user moves the traveling vehicle 2 forward, but also when the user moves the traveling vehicle 2 backward.

[0084] The series of determinations and processes shown in FIG. 5 are performed every time the tractor 1 is started, similarly to the first embodiment.

[0085] First, the control unit 4 performs the processes from step S201 to step S203 to determine whether the conditions for starting the initialization process are met. Step S201 is similar to the above step S102, step S202 is similar to the above step S103, and step S203 is similar to the above step S104, so their explanations will be omitted.

[0086] In step S204, the control unit 4 calculates the velocity vector of the traveling machine body 2 by utilizing the frequency change of the carrier wave due to the Doppler effect of the GNSS radio wave, in the same way as described in the first embodiment (step S105).

[0087] Next, the control unit 4 acquires the detection result of the forward / reverse movement detection unit 53, and determines whether or not the forward movement of the traveling machine body 2 has been detected (step S205).

[0088] As a result of the determination in step S205, if the forward / reverse movement detection unit 53 detects that the traveling machine body 2 is moving backward (step S205, No), the change in position of the traveling machine body 2 that occurred in step S204 was backward. Therefore, the control unit 4 reverses the direction of the velocity vector obtained in step S204 (step S206). On the other hand, if the forward / reverse movement detection unit 53 detects that the traveling machine body 2 is moving forward (step S205, Yes), the processing of step S206 is skipped. Thereafter, the control unit 4 calculates the yaw angle based on the velocity vector (step S207).

[0089] In this embodiment, the initialization process can be performed appropriately not only when the user moves the traveling machine body 2 forward, but also when the user moves it backward. Therefore, the initialization process of the inertial measurement unit 54 can be performed flexibly according to the state of the field, etc., thereby improving user convenience.

[0090] As described above, the autonomous driving system 100 of this embodiment includes the position information acquisition unit 52, the control unit 4, the forward / reverse movement detection unit 53, and the inertial measurement unit 54. The position information acquisition unit 52 acquires position information of the tractor 1 based on radio waves received from satellites 105, 105, .... The control unit 4 can autonomously drive the tractor 1 along a predetermined route based on the position information. The forward / reverse movement detection unit 53 can detect whether the tractor 1 is moving forward or backward. The inertial measurement unit 54 detects the angular velocity and acceleration of the tractor 1. By performing an initialization process while moving the tractor 1, the inertial measurement unit 54 can determine the orientation of the tractor 1 at the time of execution of the initialization process based on the orientation of the position change of the tractor 1 obtained based on the radio waves received from satellites 105, 105, .... If the forward / reverse movement detection unit 53 detects forward movement during the initialization process, the inertial measurement unit 54 determines that the direction of the position change is the direction of the tractor 1, and if the forward / reverse movement detection unit 53 detects reverse movement during the initialization process, the inertial measurement unit 54 determines that the direction opposite to the position change is the direction of the tractor 1.

[0091] This allows the inertial measurement unit 54 to correctly grasp the orientation of the tractor 1 and perform initialization processing, whether the tractor 1 is moving forward or backward. This improves user convenience.

[0092] The preferred embodiment of the present invention has been described above, but the above configuration can be modified, for example, as follows.

[0093] Instead of using the method of calculating a velocity vector based on the Doppler effect as described above, the initialization process for the inertial measurement unit 54 may be performed by using GNSS positioning to calculate position information for the tractor 1 before and after the movement, and then calculating the direction of the position change from the transition of the two pieces of position information to obtain the orientation of the tractor 1. Using the GNSS-RTK method allows the positions before and after the movement to be determined with high accuracy, so the above method can also be used to determine the accurate orientation of the tractor 1 and perform the initialization process for the inertial measurement unit 54. However, the method using the Doppler effect as in the above embodiment is advantageous in that it does not use a reference station and does not require waiting for the process of determining the so-called integer bias in the GNSS-RTK method, allowing the velocity of the tractor 1 to be obtained with high accuracy and quickly.

[0094] The forward / reverse movement detection unit 53 can be changed to a configuration that detects the operating position of an operating member that instructs forward / reverse movement, instead of a configuration that detects the rotation of the front wheels 7.

[0095] In the above embodiment, the vehicle speed detection unit (vehicle speed determination unit) 59 determines the vehicle speed of the tractor 1 by detecting the rotation of a gear (not shown), but this is not necessarily limited to this. For example, instead of this, the vehicle speed determination unit may be a vehicle speed sensor or the like that detects the vehicle speed by detecting the number of rotations of the front wheels 7 or the rear wheels 8.

[0096] The calculation process of the tractor velocity vector as explained in step S105 of Fig. 4 may be configured to be repeated at short time intervals, and whether vibration is occurring in the tractor 1 may be determined based on whether the change in the velocity vector is equal to or greater than a threshold value. The degree of turning can also be determined based on the change in the velocity vector.

[0097] The degree of turning of the tractor 1 may be determined by detecting the steering angle of the front wheels 7 using a turning angle sensor, instead of detecting the steering angle of the steering wheel 12.

[0098] The start conditions for the initialization process of the inertial measurement unit 54 shown in the above embodiment are merely examples, and some of these start conditions may be omitted. Alternatively, other start conditions may be added. For example, the tractor 1 may be configured to include a predetermined operating tool that the user operates when he or she wants to start the initialization process of the inertial measurement unit 54, and the operation of this operating tool may be added as one of the start conditions.

[0099] Furthermore, the order of determining the start conditions for the initialization process of the inertial measurement unit 54 shown in the above embodiment is merely an example, and the order may be reversed.

[0100] Inertial navigation using the inertial measurement unit 54 has the property that position detection errors accumulate over time. In consideration of this, the initialization process of the inertial measurement unit 54 may be configured to be performed at any appropriate timing after startup, not just immediately after startup of the tractor 1.

[0101] In the above embodiment, a highly accurate satellite positioning system using the so-called GNSS-RTK method is used, which appropriately corrects the position information obtained by the GNSS method, but the present invention is not limited to this, and other positioning systems may be used as long as they can obtain highly accurate position coordinates. For example, a differential GPS (DGPS) or a satellite-based augmentation system (SBAS) may be used.

[0102] If the specified processing is not performed even after a certain amount of time has passed since the engine 10 was turned on, the display control unit 31 may display a warning screen on the display 37 of the wireless communication terminal 46, thereby prompting the user to perform initialization processing of the inertial measurement unit 54.

[0103] In the above-described embodiment, the determinations and processes in FIGS. 4 and 5 are triggered by the start of the tractor 1, but the trigger is not limited thereto. For example, in the first embodiment, the trigger may be the detection of forward movement of the tractor 1 by the forward / reverse movement detection unit 53 after the start of the tractor 1. In the second embodiment, the trigger may be the detection of forward or reverse movement of the tractor 1 by the forward / reverse movement detection unit 53 after the start of the tractor 1. In this case, in the flowchart of FIG. 4, the determinations in steps S102 to S104 are subsequently made, and the initialization process is executed when the start conditions for these initialization processes are met. In the flowchart of FIG. 5, the determinations in steps S201 to S203 are subsequently made, and the start conditions for these initialization processes are met, and the initialization process is executed appropriately depending on whether the detection result of the forward / reverse movement detection unit 53 indicates forward or reverse movement. By not starting the IMU initialization process when the tractor 1 must be reversed after start or when a predetermined task is to be performed without moving, the control unit 4 can prioritize various processes other than the IMU initialization process.

[0104] [Appendix to the invention] According to a first aspect of the present invention, there is provided an autonomous driving system having the following configuration. Specifically, this autonomous driving system comprises a position information acquisition unit, an autonomous driving control unit, a forward / reverse movement detection unit, and an inertial measurement unit. The position information acquisition unit acquires position information of a work vehicle based on radio waves received from a satellite. The autonomous driving control unit is capable of autonomously driving the work vehicle along a predetermined route based on the position information. The forward / reverse movement detection unit is capable of detecting forward or reverse movement of the work vehicle. The inertial measurement unit detects the angular velocity and acceleration of the work vehicle. When the forward / reverse movement detection unit detects forward movement, the inertial measurement unit performs initialization processing on the orientation of the work vehicle based on the position information.

[0105] This makes it possible to improve the reliability of the detection results obtained by the inertial measurement unit.

[0106] According to a second aspect of the present invention, there is provided an autonomous driving system having the following configuration. Specifically, this autonomous driving system comprises a position information acquisition unit, an autonomous driving control unit, a forward / reverse motion detection unit, and an inertial measurement unit. The position information acquisition unit acquires position information of a work vehicle based on radio waves received from a satellite. The autonomous driving control unit is capable of autonomously driving the work vehicle along a predetermined route based on the position information. The forward / reverse motion detection unit is capable of detecting forward or reverse motion of the work vehicle. The inertial measurement unit detects angular velocity and acceleration of the work vehicle. When the forward / reverse motion detection unit detects reverse motion, the inertial measurement device reverses the direction of the position information, thereby assuming that the work vehicle is in a forward motion state, thereby enabling initialization processing to be performed.

[0107] This allows the initialization process to be performed even when the work vehicle is in reverse, thereby improving user convenience.

[0108] An autonomous driving system according to one aspect of the present invention includes a position information acquisition unit, a control unit, and an inertial measurement unit. The position information acquisition unit acquires position information of a work vehicle capable of both autonomous driving and manual driving. The control unit is capable of causing the work vehicle to autonomously drive along a predetermined route based on the position information. The inertial measurement unit detects at least the angular velocity of the work vehicle. The control unit includes in a start condition for autonomous driving of the work vehicle that the orientation of the work vehicle is identified as the work vehicle is manually driven. [Explanation of symbols]

[0109] 1 Tractor (Robot Tractor, Work Vehicle) 4. Control unit (autonomous driving control unit) 52 Location information acquisition unit 53 Forward / reverse detection unit 54 Inertial Measurement Unit 100 Autonomous Driving System 105 satellites (positioning satellites)

Claims

1. A control unit is provided that can automatically drive a work vehicle based on position information of the work vehicle, the work vehicle being capable of both automatic and manual driving; The work vehicle is actually manually driven, and the orientation of the work vehicle is identified during the manual driving, which is set as a start condition for the automatic driving of the work vehicle. Autonomous driving system.

2. The control unit displays a guide prompting an operation to identify the orientation of the work vehicle. The automated driving system according to claim 1 .

3. The control unit identifies the orientation of the work vehicle each time the work vehicle is started. The automated driving system according to claim 1 or 2.

4. a work vehicle capable of both automatic and manual driving, and causing the work vehicle to automatically drive based on position information of the work vehicle; The work vehicle is actually manually driven, and the orientation of the work vehicle is identified during the manual driving, which is set as a start condition for the automatic driving of the work vehicle. Automated driving method.

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