JP2019166981A - Autonomous steering device - Google Patents

Abstract

To provide an autonomous steering device that stably travels a work vehicle along a travel path set in advance for a farm field.SOLUTION: An autonomous steering device comprises a front target angle calculation unit, a yaw rate acquisition unit, an arithmetic tire angle calculation unit, and a steering angle control unit. The front target angle calculation unit calculates a front target angle formed between a travel path and a line segment connecting a rice transplanter and a front target point, which is a forward point on the travel path and is a target point for bringing the rice transplanter into a position closer to the travel path. The yaw rate acquisition unit acquires a yaw rate, which is an angular velocity of the rice transplanter using a vertical direction as a rotation axis thereof. The arithmetic tire angle calculation unit calculates an arithmetic tire angle, which is a tire steering angle for achieving the yaw rate acquired by the yaw rate acquisition unit. The steering angle control unit performs a first comparison process for comparing the front target angle and the arithmetic tire angle and controls the steering angle on the basis of a comparison result.SELECTED DRAWING: Figure 5

Description

  The present invention mainly relates to an autonomous steering device that autonomously steers a work vehicle and causes the work vehicle to travel along a travel route set in advance in a field.

  Patent Document 1 discloses a tractor that can autonomously travel along a travel route set in a farm field. The tractor autonomously travels along the travel route by performing processing for calculating the target steering angle based on the direction of the vehicle body relative to the travel route, the current steering angle, and the target orientation.

JP 2002-358122 A

  Here, when skidding has occurred due to the influence of disturbance or the like, there is a difference between the current steering angle and the actual traveling direction of the work vehicle, which makes it difficult to stably travel along the travel route.

  The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide an autonomous steering device that allows a work vehicle to travel stably along a travel route set in advance in a farm field.

Means and effects for solving the problems

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

  According to an aspect of the present invention, an autonomous steering device having the following configuration is provided. That is, this autonomous steering device autonomously steers the work vehicle and causes the work vehicle to travel along a travel route set in advance in the field. The autonomous steering apparatus includes a front target angle calculation unit, a yaw rate acquisition unit, a calculated tire angle calculation unit, and a rudder angle control unit. The forward target angle calculation unit is a line connecting the forward target point and the work vehicle, which is a forward point on the travel route and is a target point for bringing the work vehicle closer to the travel route; A front target angle that is an angle formed by the travel route is calculated. The yaw rate acquisition unit acquires a yaw rate that is an angular velocity of the work vehicle with a vertical direction as a rotation axis from an angular velocity sensor arranged in the work vehicle. The calculation tire angle calculation unit calculates a calculation tire angle that is a steering angle of a tire that realizes the yaw rate acquired by the yaw rate acquisition unit. The rudder angle control unit performs a first comparison process for comparing the front target angle with the calculated tire angle, and controls the rudder angle based on the comparison result.

  Thus, by using the yaw rate instead of the tire angle, the work vehicle can be stably driven along the travel route even when a skid or the like due to disturbance can occur.

  The autonomous steering device preferably has the following configuration. In other words, the autonomous steering device includes a steering angle acquisition unit that acquires a current steering angle from a steering angle sensor arranged in the work vehicle. The rudder angle control unit performs a second comparison process for comparing the current rudder angle acquired by the rudder angle acquisition unit with the front target angle, and the comparison results of both the first comparison process and the second comparison process. The rudder angle is controlled based on

  As a result, by performing control while further considering the current steering angle, the position of the work vehicle can be corrected in a short period of time, even if the current steering angle may be significantly changed.

  In the autonomous steering device, the steering angle control unit may control the steering angle by assigning different weights to the comparison result of the first comparison process and the comparison result of the second comparison process. preferable.

  As a result, it is possible to perform control suitable for the specifications of the work vehicle, the nature of the field, the required operation, and the like.

  In the autonomous steering device, it is preferable that the steering angle control unit calculates a target steering angular velocity based on the comparison result and changes the target steering angular velocity.

  Thereby, the steering angle, in particular, the steering angular velocity can be controlled, and the steering angle can be changed at an appropriate angular velocity according to the situation.

A side view of a rice transplanter provided with a control part (autonomous steering device) concerning one embodiment of the present invention. The top view of a rice transplanter. The block diagram of an autonomous running system. The figure explaining a mode and the front target angle which make a rice transplanter autonomously drive along a linear driving | running | working path | route. The figure which shows the process which calculates the target steering angular velocity in the case of making a rice transplanter drive autonomously along a linear driving | running | working path | route. The figure explaining the process which calculates a calculation tire angle from a yaw rate. The figure explaining a mode that a rice transplanter autonomously travels along the turning travel route, and a front target angle. The figure which shows the process which calculates the target steering angular velocity in the case of making a rice transplanter drive autonomously along the driving | running | working path | route for turning. The figure which shows the process which calculates the target steering angular velocity which concerns on a 1st modification. The figure which shows the process which calculates the target steering angular velocity which concerns on a 2nd modification.

  Next, embodiments of the present invention will be described with reference to the drawings. The autonomous traveling system 100 of this embodiment is a system for causing the rice transplanter 1 that performs rice planting (planting seedlings) in an agricultural field to perform autonomous traveling. Here, the autonomous traveling means that the rice transplanter 1 travels at least by autonomously steering. In the present embodiment, the operator makes settings related to autonomous traveling using the wireless communication terminal 7, and the rice transplanter 1 performs autonomous traveling based on the settings. Moreover, in this embodiment, although it is the structure which makes the rice transplanter 1 perform autonomous driving | running | working in an operator's boarding, the rice transplanter 1 which the operator has not boarded can also make autonomous driving | running | working.

  First, the rice transplanter 1 of this embodiment is demonstrated with reference to FIG.1 and FIG.2. FIG. 1 is a side view of the rice transplanter 1. FIG. 2 is a plan view of the rice transplanter 1. As shown in FIGS. 1 and 2, the rice transplanter 1 includes a vehicle body portion 11, a pair of left and right front wheels 12, a pair of left and right rear wheels 13, and a planting portion 14.

  An engine 22 is disposed inside the bonnet 21 disposed at the front portion of the vehicle body 11. The power generated by the engine 22 is transmitted to the front wheels 12 and the rear wheels 13 via the mission case 23. The power transmitted through the mission case 23 is also transmitted to the planting unit 14 through the PTO shaft 24 disposed at the rear part of the vehicle body unit 11. A driver's seat 25 on which an operator gets is provided at a position between the front wheel 12 and the rear wheel 13 in the front-rear direction of the vehicle body 11. A steering handle 26 for an operator to steer the rice transplanter 1 is disposed in front of the driver seat 25.

  The planting part 14 is connected to the rear of the vehicle body part 11 via an elevating link mechanism 31. The elevating link mechanism 31 has a parallel link structure including a top link 31a and a lower link 31b. A lifting cylinder 32 is connected to the lower link 31b. With this configuration, the entire planting unit 14 can be moved up and down by extending and lowering the lifting cylinder 32.

  The planting unit 14 mainly includes a planting input case 33, a plurality of planting units 34, a seedling mounting table 35, a plurality of floats 36, and a spare seedling table 38.

  Each planting unit 34 includes a planting transmission case 41 and a rotation case 42. Power is transmitted to the planting transmission case 41 via the PTO shaft 24 and the planting input case 33. A rotation case 42 is attached to each planting transmission case 41 on both sides in the vehicle width direction. Two planting claws 43 are attached to each rotating case 42 in the traveling direction of the rice transplanter 1. By these two planting claws 43, planting for one line is performed.

  As shown in FIG. 1, the seedling mounting table 35 is disposed in front of the planting unit 34 and is configured to be capable of mounting a seedling mat. The seedling stage 35 is configured to be capable of laterally moving in a reciprocating manner (slidable in the lateral direction). In addition, the seedling stage 35 is configured to be capable of intermittently feeding the seedling mat vertically downward at the reciprocating end of the seedling stage 35. With this configuration, the seedling stage 35 can supply seedlings of a seedling mat to each planting unit 34. Thus, the rice transplanter 1 can sequentially supply seedlings to the respective planting units 34 to continuously plant seedlings.

  The float 36 shown in FIG. 1 is provided in the lower part of the planting part 14, and is arrange | positioned so that the lower surface can contact the ground. When the float 36 is in contact with the ground, the field surface before planting the seedling is leveled. The float 36 is provided with an unillustrated float sensor that detects the swing angle of the float 36. The swing angle of the float 36 corresponds to the distance between the ground and the planting part 14. The rice transplanter 1 can keep the height of the planting part 14 at a constant level by operating the lifting cylinder 32 based on the swing angle of the float 36 to move the planting part 14 up and down.

  The spare seedling stand 38 is disposed outside the bonnet 21 in the vehicle width direction and can mount a seedling box containing a spare mat seedling. The upper portions of the pair of left and right auxiliary seedling stands 38 are connected to each other by a connecting frame 27 extending in the vertical direction and the vehicle width direction. A housing 28 is disposed at the center of the connecting frame 27 in the vehicle width direction. In the housing 28, a positioning antenna 61, an inertial measurement device (angular velocity sensor) 62, and a communication antenna 63 are arranged. The positioning antenna 61 can receive radio waves from positioning satellites constituting a satellite positioning system (GNSS). The position of the rice transplanter 1 can be acquired by performing a known positioning calculation based on this radio wave. The inertial measurement device 62 includes three gyro sensors (angular velocity sensors) and three acceleration sensors. Therefore, the inertial measurement device 62 detects a value including the yaw rate that is the angular velocity of the rice transplanter 1 with the vertical direction (vertical direction) as the rotation axis. By using the angular velocity and acceleration of the rice transplanter 1 detected by the inertial measuring device 62 as auxiliary means, the accuracy of the positioning result of the rice transplanter 1 is enhanced. The communication antenna 63 is an antenna for performing wireless communication with the wireless communication terminal 7.

  As shown in FIG. 3, the rice transplanter 1 includes a control unit (autonomous steering device) 50. The control unit 50 is configured as a known computer and includes a CPU, a ROM, a RAM, an input / output unit, and the like (not shown). The CPU can read various programs from the ROM and execute them. Various programs and data are stored in the ROM. And by cooperation of said hardware and software, the control part 50, the memory | storage part 51, the vehicle speed control part 52, the steering angle control part 53, the working machine control part 54, the steering angle acquisition part 55, and a yaw rate acquisition part 56, the front target angle calculation unit 57, and the calculation tire angle calculation unit 58 can be operated. The control unit 50 may be a single piece of hardware or a plurality of pieces of hardware that can communicate with each other. Therefore, for example, another hardware may perform a process related to autonomous steering. Moreover, the structure which performs a part of process which the control part 50 performs with the hardware provided in addition to the rice transplanter 1 may be sufficient. In addition to the inertia measuring device 62 described above, a position acquisition unit 64, a communication processing unit 65, a vehicle speed sensor 66, and a rudder angle sensor 67 are connected to the control unit 50.

  The position acquisition unit 64 is electrically connected to the positioning antenna 61. The position acquisition unit 64 acquires the position of the rice transplanter 1 as, for example, latitude and longitude information from the positioning signal based on the radio wave received by the positioning antenna 61. The position acquisition unit 64 performs positioning using a known GNSS-RTK method after receiving a positioning signal from a reference station (not shown) by an appropriate method. However, instead of this, for example, positioning using a differential GNSS, single positioning, or the like may be performed. Alternatively, position acquisition based on radio wave intensity such as wireless LAN or position acquisition by inertial navigation may be performed.

  The communication processing unit 65 is electrically connected to the communication antenna 63. The communication processing unit 65 can perform modulation processing or demodulation processing by an appropriate method to transmit / receive data to / from the wireless communication terminal 7.

  The vehicle speed sensor 66 is disposed at an appropriate position of the rice transplanter 1, for example, at the axle of the front wheel 12. The vehicle speed sensor 66 is configured to generate a pulse corresponding to the rotation of the axle, for example. The detection result data obtained by the vehicle speed sensor 66 is output to the control unit 50.

  The rudder angle sensor 67 is a sensor that detects the rudder angle. In the present specification, the rudder angle includes a steering angle and a tire angle (wheel angle). The steering angle is the rotation angle of the steering shaft. The tire angle is an inclination angle of the wheel with respect to the front / rear axis of the rice transplanter 1 (more specifically, an angle formed by the front / rear axis of the vehicle and a direction perpendicular to the rotation axis of the wheel in plan view). In the present embodiment, the steering angle sensor 67 is disposed on the steering shaft, and the steering angle is detected. The rudder angle sensor 67 may be configured to detect a tire angle. In this configuration, the rudder angle sensor 67 is provided, for example, on a king pin (not shown) provided on the front wheel 12. The detection result data obtained by the steering angle sensor 67 is output to the control unit 50.

  The vehicle speed control unit 52 performs vehicle speed control for autonomously changing the vehicle speed of the rice transplanter 1. Vehicle speed control is control which adjusts the vehicle speed of the rice transplanter 1 based on a predetermined condition. Specifically, the vehicle speed control unit 52 determines the gear ratio of the transmission in the mission case 23 and the rotation of the engine 22 so that the current vehicle speed obtained from the detection result of the vehicle speed sensor 66 approaches the target vehicle speed. Change at least one of the speeds. The vehicle speed control includes control for stopping the rice transplanter 1 by setting the vehicle speed to zero.

  The rudder angle control unit 53 performs rudder angle control for autonomously changing the rudder angle of the rice transplanter 1. The rudder angle control is control for adjusting the rudder angle of the rice transplanter 1 based on a predetermined condition. Specifically, the steering angle control unit 53 drives, for example, a steering actuator provided on the rotation shaft (steering shaft) of the steering handle 26 based on the current steering angle obtained from the detection result of the steering angle sensor 67. . Details of the steering angle control will be described later. The steering angle control unit 53 may be configured to directly adjust the tire angle instead of the steering angle.

  The controller 50 can perform both the vehicle speed control and the steering angle control at the same time, but can also perform only one of them. For example, when the control unit 50 performs only the steering angle control, the vehicle speed is manually operated by the operator.

  The work machine control unit 54 can control the operation (elevating operation or planting operation) of the planting unit 14 based on a predetermined condition.

  The steering angle acquisition unit 55 performs a process of acquiring the steering angle detected by the steering angle sensor 67. The yaw rate acquisition unit 56 performs processing for acquiring a yaw rate that is one of the detection values of the inertial measurement device 62. The front target angle calculation unit 57 and the calculated tire angle calculation unit 58 calculate values used in the steering angle control performed by the steering angle control unit 53 (details will be described later).

  The wireless communication terminal 7 is a tablet computer. The wireless communication terminal 7 includes a communication antenna 71, a communication processing unit 72, a display unit 73, an operation unit 74, and a control unit 80. The wireless communication terminal 7 is not limited to a tablet computer, and may be a smartphone or a notebook computer. The wireless communication terminal 7 performs various processes related to the autonomous traveling of the rice transplanter 1 as described later, but at least a part of this process can be performed by the arithmetic unit of the rice transplanter 1. Conversely, the wireless communication terminal 7 can also perform at least a part of various processes related to autonomous traveling performed by the rice transplanter 1.

  The communication antenna 71 is configured to include a short-distance communication antenna for performing wireless communication with the rice transplanter 1 and a portable communication antenna for performing communication using a mobile phone line and the Internet. The communication processing unit 72 is electrically connected to the communication antenna 71. The communication processing unit 72 can perform data transmission / reception with the wireless communication terminal 7 or other devices by performing modulation processing or demodulation processing by an appropriate method.

  The display unit 73 is a liquid crystal display, an organic EL display, or the like, and is configured to display an image. The display unit 73 can display, for example, information related to autonomous traveling, information related to the setting of the rice transplanter 1, detection results of various sensors, warning information, and the like. The operation unit 74 includes a touch panel and hardware keys. The touch panel is disposed so as to overlap the display unit 73 and can detect an operation with an operator's finger or the like. The hardware key is disposed on the side surface of the casing of the wireless communication terminal 7 or around the display unit 73 and can be operated by being pressed by the operator. The wireless communication terminal 7 may be configured to include only one of a touch panel and a hardware key.

  The control unit 80 is configured as a known computer and includes a CPU, a ROM, a RAM, an input / output unit, and the like (not shown). The CPU can read various programs from the ROM and execute them. Various programs and data are stored in the ROM. And the control part 80 can be operated as the memory | storage part 81, the display control part 82, and the driving route creation part 83 by cooperation of said hardware and software.

  The storage unit 81 stores information related to the setting of the rice transplanter 1, travel routes created by the operator, various conditions for creating travel routes, and the like. The display control unit 82 performs control to display the above-described information on the display unit 73. The travel route creation unit 83 performs a process of creating a travel route based on the operation of the operator. The traveling route includes a linear traveling route, a turning traveling route, and a route combining them. The straight path includes not only a completely straight path but also a path whose direction slightly changes.

  Next, referring to FIG. 4 to FIG. 6, by performing the steering angle control along the linear travel route 91 using the yaw rate, even if a side slip occurs, the linear travel route 91 is accurately obtained. A process for enabling the rice transplanter 1 to travel along will be described. FIG. 4 is a diagram illustrating a state in which the rice transplanter 1 autonomously travels along the straight traveling route 91 and a front target angle. FIG. 5 is a diagram illustrating a process of calculating a target steering angular speed when the rice transplanter 1 autonomously travels along the linear travel route 91. FIG. 6 is a diagram for explaining a process for calculating the calculated tire angle from the yaw rate.

  FIG. 4 shows a straight traveling route 91. The rice transplanter 1 travels at a position away from the linear travel route 91. In this situation, the steering angle control performed by the steering angle control unit 53 to return the rice transplanter 1 to the linear travel route 91 will be described. Further, as shown in FIG. 5, the inputs of this steering angle control are the front target angle φ and the calculated tire angle θ.

  First, a method for calculating the front target angle φ will be described. The front target angle φ is calculated by the control unit 50 (front target angle calculation unit 57). The front target angle φ is an angle used when the rice transplanter 1 travels along the linear travel route 91. The forward target angle φ is determined based on the forward target point P1. A front target distance is set in advance in the rice transplanter 1, and the front target angle calculation unit 57 specifies a point (a front target point P1) where the distance from the rice transplanter 1 to the linear travel route 91 is the front target distance. To do. Moreover, the front target angle calculation part 57 draws the line segment (line L1) which connects the rice transplanter 1 and the front target point P1. An angle formed by the line L1 and the linear travel route 91 (particularly an angle of 180 degrees or less) is the front target angle φ. When the line L2 that passes through the rice transplanter 1 and is parallel to the straight traveling route 91 is drawn, the front target angle φ can also be expressed as an angle formed by the line L1 and the line L2. Moreover, how to obtain | require the front target angle (phi) is an example, and if it is an angle required in order to make the rice transplanter 1 follow the linear driving | running | working path | route 91, it can also obtain | require with another calculation method.

  Next, a method for calculating the calculated tire angle θ will be described with reference to FIG. The calculated tire angle θ is calculated by the control unit 50 (calculated tire angle calculation unit 58). The calculated tire angle θ is an ideal (theoretical) tire angle for turning the rice transplanter 1 at the detected yaw rate. In other words, the calculated tire angle θ is a value obtained by converting the detected yaw rate into a tire angle. The calculated tire angle θ is calculated by converting the rice transplanter 1 that is a four-wheeled vehicle into a two-wheeled vehicle model. The two-wheeled vehicle model is a model that assumes that the front wheels 12 and the rear wheels 13 are not left and right, but one at the center. In FIG. 6, ω is the yaw rate, V is the vehicle speed, Wb is the wheel base, and R is the turning radius in the two-wheeled vehicle model. The detection result of the vehicle speed sensor 66 can be used for V. The wheel base is stored in advance in the storage unit 51 or the like. Equation (1) in FIG. 6 is an equation showing a method for calculating the turning radius in the two-wheeled vehicle model. Equation (2) is an equation obtained by substituting the relationship of Equation (1) into the equation showing the relationship between angular velocity, velocity, and radius. Expression (3) is an expression indicating the value of the calculated tire angle θ by modifying Expression (2). By performing such processing, the calculated tire angle θ can be calculated from the yaw rate.

  Here, consider a case where the rice transplanter 1 slides on the field. Side slip means that the rice transplanter 1 travels in a direction different from the direction calculated by the tire angle. Since the rice transplanter 1 travels through paddy fields, skidding is likely to occur compared to a tractor traveling on soil. Moreover, even if it is other work vehicles, such as a tractor, when a farm field is inclined etc., a skid tends to occur. When the side slip occurs, the rice transplanter 1 travels in a direction different from the tire angle. Therefore, if the steering angle control is performed based on the detection result of the steering angle sensor 67 and the front target angle φ, the rice transplanter 1 is stably linearized due to the influence including the difference between the tire angle and the traveling direction. The vehicle could not travel along the travel route 91.

  On the other hand, in the present embodiment, the calculated tire angle θ calculated from the yaw rate is used instead of the detection result of the rudder angle sensor 67. Specifically, the rudder angle control unit 53 performs a first comparison process that compares the front target angle φ with the calculated tire angle θ (specifically, the calculated tire angle θ is subtracted from the front target angle φ). As a result, the front target angle φ is corrected based on the calculated tire angle θ so as to eliminate the influence of skidding. The comparison result of the first comparison process is a value related to a tire angle that is insufficient to realize the front target angle φ, and this value is input to the PID controller. The output of the PID controller is a target steering angular velocity. By applying the target steering angular velocity output from the PID controller, the values of the front target angle φ and the calculated tire angle θ change, so the comparison result of the first comparison process also changes, and a new target steering angular velocity is output. The By continuously performing the above processing, the rice transplanter 1 can travel along the straight traveling route 91.

  In particular, since the yaw rate is a value including the effect of skidding, the steering angle control can be performed while taking into account the effect of skidding. Therefore, compared to the configuration using the detection result of the rudder angle sensor 67, the rudder angle control unit 53 of the present embodiment prevents meandering and offset of the rice transplanter 1, and is stable along the linear travel path 91. The rice transplanter 1 can be driven.

  Next, with reference to FIG.7 and FIG.8, the steering angle control in the case of making the rice transplanter 1 autonomously drive along the turning travel path | route 92 is demonstrated. FIG. 7 is a diagram illustrating a state in which the rice transplanter 1 autonomously travels along the turning travel path 92 and the front target angle. FIG. 8 is a diagram illustrating a process of calculating a target steering angular velocity when the rice transplanter 1 autonomously travels along the traveling route 92 for turning.

  The forward target angle φ when the rice transplanter 1 autonomously travels along the turning travel path 92 is calculated as follows. Although the method of obtaining the forward target point P1 is the same as that of the linear travel route 91, the value of the front target distance may be different between the linear travel route 91 and the turning travel route 92. Then, the front target angle calculation unit 57 draws a line L3 that is a line segment connecting the rice transplanter 1 and the point P2 indicating the turning center of the turning traveling route 92. Next, the front target angle calculation unit 57 draws a line L4 that is perpendicular to the line L3 and passes through the rice transplanter 1. The front target angle calculation unit 57 calculates the angle formed by the line L1 and the line L4 as the front target angle φ. Since the line L4 is a tangent drawn from the turning travel route 92 at the intersection of the line L3 and the turning travel route 92, the line L4 can also be understood as indicating the direction of the turning travel route 92 in the current rice transplanter 1. . Note that the point P2 or the front target angle φ may be obtained using a method different from this. In addition, the calculated tire angle calculation unit 58 calculates the calculated tire angle θ based on the yaw rate detected by the inertia measuring device 62 as in the linear travel route 91.

  As shown in FIG. 8, when the rice transplanter 1 travels along the traveling route 92 for turning, the turning calculation tire angle is added to the comparison result of the first comparison process. The turning calculation tire angle is a tire angle required for turning along the turning travel path 92. As the turning calculation tire angle, a turning yaw rate, which is a yaw rate for turning along the turning travel route 92, is estimated, and the turning yaw rate is converted into a tire angle by the method described with reference to FIG. The turning yaw rate can be estimated based on the radius of curvature of the turning travel path 92 and the like.

  When the vehicle travels along the traveling route 92 for turning, only the turning calculation tire angle is added, and control other than the above is performed. Therefore, as described above, even if a side slip occurs in the rice transplanter 1, the rice planter 1 can be prevented from meandering and offset, and the rice transplanter 1 can be stably transplanted along the turning travel path 92. The machine 1 can be driven.

  Next, a first modification will be described with reference to FIG. FIG. 9 is a diagram illustrating processing for calculating the target steering angular velocity according to the first modification. In the first and second modified examples, when the rice transplanter 1 autonomously travels along the turning travel path 92, only the turning calculation tire angle is added, and thus the description thereof is omitted.

  In the first modification shown in FIG. 9, in addition to the first comparison process, the second comparison process is performed. The second comparison process is a process of comparing the front target angle φ and the current tire angle (current steering angle) (a process of subtracting the current tire angle from the front target angle φ). In this embodiment, since the steering angle sensor 67 detects the steering angle, the current steering angle can be converted into the current tire angle by integrating a preset ratio. Even when such conversion is performed, since the steering angle and the tire angle both correspond to the steering angle, the current steering angle acquired by the steering angle acquisition unit 55 is compared with the front target angle φ. Will be. As described above, the current tire angle can also be detected directly.

  The comparison result of the second comparison process is added to the comparison result of the first comparison process. Therefore, for example, when the difference between the front target angle φ and the current tire angle is large, in other words, when the front wheels 12 are facing away from the target, the comparison result of the second comparison process is large. Therefore, the steering angle can be corrected early in such a case by performing the second comparison process.

  Next, a second modification will be described with reference to FIG. FIG. 10 is a diagram illustrating processing for calculating the target steering angular velocity according to the second modification. In the first and second modified examples, when the rice transplanter 1 autonomously travels along the turning travel path 92, only the turning calculation tire angle is added, and thus the description thereof is omitted.

  In the second modified example shown in FIG. 10, the weighting factor α is added to the comparison result of the first comparison process, and the weighting factor β is added to the comparison result of the second comparison process. The weighting coefficient α and the weighting coefficient β have different values. Here, by performing the rudder angle control using the comparison result of the first comparison process, it is possible to stabilize the traveling of the rice transplanter 1 even when skidding or the like occurs, but depending on the situation, the steering The angle may not be corrected early. On the other hand, the steering angle can be corrected early by performing the steering angle control using the comparison result of the second comparison process, but the traveling of the rice transplanter 1 is stabilized even when a side slip or the like occurs. It may not be possible.

  Therefore, the steering angle control according to the situation and the operator's request can be realized by adjusting the weighting factor based on the state of the field, the nature of the work vehicle, and the operator's request. The weighting factor may be adjusted manually by an operator or maintenance company, or may be configured such that optimum values are calculated according to detection values of various sensors.

  As described above, the control unit 50 autonomously steers the rice transplanter 1 and causes the rice transplanter 1 to travel along a travel route set in advance in the field. The control unit 50 includes a front target angle calculation unit 57, a yaw rate acquisition unit 56, a calculated tire angle calculation unit 58, and a steering angle control unit 53. The front target angle calculation unit 57 is a line segment connecting the front target point P1 which is a point on the travel route and is a target for bringing the rice transplanter 1 closer to the travel route and the rice transplanter 1 ( A front target angle φ, which is an angle formed by the line L1) and the travel route, is calculated. The yaw rate acquisition unit 56 acquires the yaw rate that is the angular velocity of the rice transplanter 1 with the vertical direction as the rotation axis from the inertial measurement device 62 arranged in the rice transplanter 1. The calculated tire angle calculation unit 58 calculates a calculated tire angle that is a steering angle of a tire (front wheel 12) that realizes the yaw rate acquired by the yaw rate acquisition unit 56. The steering angle control unit 53 performs a first comparison process that compares the front target angle φ with the calculated tire angle, and controls the steering angle based on the comparison result (calculates and applies the target steering angular velocity).

  As a result, by using the yaw rate instead of the tire angle, the rice transplanter 1 can travel stably along the travel route even when a skid or the like due to disturbance can occur.

  In addition, the control unit 50 of the present embodiment includes a steering angle acquisition unit 55 that acquires the current steering angle (current steering angle) from the steering angle sensor 67 arranged in the rice transplanter 1. The rudder angle control unit 53 performs a second comparison process for comparing the current rudder angle acquired by the rudder angle acquisition unit 55 (the current tire angle obtained by converting the current steering angle) with the front target angle φ, and the first comparison process. And the steering angle are controlled based on the comparison results of both the second comparison process and the second comparison process.

  As a result, the position of the rice transplanter 1 can be corrected in a short period of time even when the current rudder angle is largely changed by performing control in consideration of the current rudder angle.

  Further, in the control unit 50 of the present embodiment, the steering angle control unit 53 controls the steering angle by assigning different weights to the comparison result of the first comparison process and the comparison result of the second comparison process. .

  Thereby, control suitable for the specification of the rice transplanter 1, the property of the field, the required operation, and the like can be performed.

  Moreover, in the control part 50 of this embodiment, the steering angle control part 53 calculates a target steering angular velocity based on a 1st comparison result and a 2nd comparison result, and changes the said target steering angular velocity.

  Thereby, the steering angle, in particular, the steering angular velocity can be controlled, and the steering angle can be changed at an appropriate angular velocity according to the situation.

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

  In the above embodiment, the output value (control target) of the steering angle control performed by the steering angle control unit 53 is the target steering angular speed, but it may be the target tire angular speed. Further, the output value of the steering angle control may be a target steering angle or a target tire angle.

  In the above embodiment, the inertial measurement device 62 is configured to include the triaxial angular velocity sensor, but may be configured to detect only the yaw rate.

  In the above embodiment, the target steering angle (target steering angular velocity) is calculated by PID control, but the target steering angle can also be calculated by other feedback control (for example, PI control).

  In the above embodiment, the rice transplanter 1 and the wireless communication terminal 7 perform wireless communication, but may be configured to perform wired communication.

  Although the example which applies an autonomous steering apparatus to the rice transplanter 1 was demonstrated in the said embodiment, an autonomous steering apparatus is applicable also to the tractor and combine which are other agricultural work vehicles. Moreover, even if it is a case where it applies to work vehicles other than the rice transplanter 1, the autonomous steering apparatus may be arrange | positioned at the work vehicle and may be arrange | positioned at the apparatus different from a work vehicle.

1 Rice transplanter (work vehicle)
12 Front wheel 26 Steering handle 50 Control unit (autonomous steering device)
53 Steering angle control unit 55 Steering angle acquisition unit 56 Yaw rate acquisition unit 57 Forward target angle calculation unit 58 Calculated tire angle calculation unit 62 Inertial measurement device (angular velocity sensor)
67 Rudder angle sensor 100 Autonomous traveling system

Claims (4)

In an autonomous steering device that autonomously steers a work vehicle and causes the work vehicle to travel along a travel route set in advance in the field,
An angle formed by a line segment connecting the forward target point, which is a forward point on the travel route, and a target point for bringing the work vehicle closer to the travel route, and the work vehicle, and the travel route. A forward target angle calculation unit for calculating a forward target angle that is,
A yaw rate acquisition unit that acquires a yaw rate that is an angular velocity of the work vehicle with a vertical direction as a rotation axis from an angular velocity sensor disposed in the work vehicle;
A calculation tire angle calculation unit that calculates a calculation tire angle that is a steering angle of a tire that realizes the yaw rate acquired by the yaw rate acquisition unit;
A steering angle control unit that performs a first comparison process that compares the front target angle and the calculated tire angle, and controls a steering angle based on the comparison result;
An autonomous steering device comprising: The autonomous steering device according to claim 1,
A steering angle acquisition unit that acquires a current steering angle from a steering angle sensor arranged in the work vehicle;
The rudder angle control unit performs a second comparison process for comparing the current rudder angle acquired by the rudder angle acquisition unit with the front target angle, and the comparison results of both the first comparison process and the second comparison process. An autonomous steering device that controls the rudder angle based on the above. The autonomous steering device according to claim 2,
The autonomous steering device, wherein the steering angle control unit controls the steering angle by assigning different weights to the comparison result of the first comparison process and the comparison result of the second comparison process. The autonomous steering device according to any one of claims 1 to 3,
The said steering angle control part calculates a target steering angular velocity based on the said comparison result, The autonomous steering apparatus characterized by changing the said target steering angular velocity.

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