Patent Publication Number: US-2022221865-A1

Title: Autonomous Travel System

Description:
TECHNICAL FIELD 
     The present invention relates primarily to an autonomous travel system that causes a work vehicle to autonomously travel along a travel route after a field is registered. 
     BACKGROUND ART 
     In a system with which a work vehicle autonomously travels in a field, a travel route for autonomous travel is created after the shape (position) of the field is registered. Furthermore, as the distance and area are not accurately represented on a map that is made plane by using, for example, Mercator projection, it is difficult to register the accurate shape of the field from this type of map. Therefore, as described in Patent Literature 1, the process to register the position of the field is performed after a work vehicle actually travels along the outer periphery of the field. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2017-127289 
       
    
     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     However, causing the work vehicle to travel along the outer periphery of the field is time-consuming and troublesome for users. 
     The present invention has been made in consideration of the above circumstances, and its primary object is to provide an autonomous travel system with which it is possible to properly register a field without the actual travel in the field. 
     Means for Solving the Problems 
     Effect of the Invention 
     The problem to be solved by the present invention is as described above, and the means for solving this problem and an effect thereof will be described below. 
     According to an aspect of the present invention, an autonomous travel system having the configuration below is provided. Specifically, the autonomous travel system includes a map acquisition unit, a field specifying unit, a route creation unit, and a travel control unit. The map acquisition unit acquires an orthophoto. The field specifying unit specifies a field area included in a map of the orthophoto acquired by the map acquisition unit. The route creation unit creates a travel route along which a work vehicle autonomously travels in the field area specified by the field specifying unit. The travel control unit causes the work vehicle to autonomously travel along the travel route created by the route creation unit. 
     Thus, by using the field area created based on the orthophoto, it is possible to properly register the field and conduct autonomous travel along an appropriate travel route without the actual travel in the field to register the field. 
     The above-described autonomous travel system preferably has the configuration below. Specifically, the autonomous travel system includes a display unit that displays an image. The display unit displays an image combining the map acquired by the map acquisition unit and the field area specified by the field specifying unit. 
     Thus, by specifying the field area from the map, the position of the specified field matches the position of the field on the map. As a result, the display positions of them may match on the screen of the display unit. 
     The above-described autonomous travel system preferably has the configuration below. Specifically, the autonomous travel system includes a division unit and a correction unit. The division unit further divides the field area into a plurality of unit field areas. The correction unit removes a designated area from the unit field area or adds a designated area to the unit field area to update the unit field area. 
     Thus, the unit field area may be updated so as to have an appropriate shape in a case where an unnecessary area is set as a unit field area or a necessary area is not set as a unit field area. 
     The above-described autonomous travel system preferably has the configuration below. Specifically, the autonomous travel system includes a division unit and a correction unit. The division unit further divides the field area into a plurality of unit field areas. The correction unit combines the plurality of designated unit field areas to obtain the one new unit field area. 
     Thus, it is possible to combine unit field areas in a situation where, for example, it is desirable to process them as one unit field area although they are divided as a plurality of unit field areas. 
     The above-described autonomous travel system preferably has the configuration below. Specifically, the autonomous travel system includes a division unit and a correction unit. The division unit further divides the field area into a plurality of unit field areas. The correction unit divides the one designated unit field area to obtain the plurality of new unit field areas. 
     Thus, it is possible to divide a unit field area in a situation where, for example, it is desirable to process it as a plurality of unit field areas although it is divided as one unit field area. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view illustrating an overall configuration of a rice transplanter used in an autonomous travel system according to an embodiment of the present invention. 
         FIG. 2  is a plan view of the rice transplanter. 
         FIG. 3  is a block diagram illustrating a primary configuration of the autonomous travel system. 
         FIG. 4  is a diagram illustrating a travel route created in a field. 
         FIG. 5  is a flowchart illustrating a process to acquire an orthophoto and register a field. 
         FIG. 6  is a diagram conceptually illustrating a process to combine an orthophoto and a field area to create a superimposed image. 
         FIG. 7  is a diagram illustrating how field information is displayed for the combined image of the orthophoto and the field area. 
         FIG. 8  is a diagram illustrating a process to change a shape of a specified field. 
         FIG. 9  is a diagram illustrating a process to combine specified fields to change them into one field. 
         FIG. 10  is a diagram illustrating a process to divide a specified field to change it into two fields. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Next, an embodiment of the present invention will be described with reference to the drawings.  FIG. 1  is a side view of a rice transplanter  1  used in an autonomous travel system  100  according to an embodiment of the present invention.  FIG. 2  is a plan view of the rice transplanter  1 .  FIG. 3  is a block diagram illustrating a primary configuration of the autonomous travel system  100 . 
     The autonomous travel system  100  according to the present embodiment is a system that causes the rice transplanter  1 , which performs rice planting (seedling planting) in a field, to autonomously travel. The autonomous travel means that a device related to travel is controlled by a control device included in the rice transplanter  1  so that at least steering is autonomously performed along a predetermined route. Furthermore, a configuration may be such that a vehicle velocity, a work by a work machine, or the like, in addition to steering is autonomously performed. During the autonomous travel, there may be a case where a person is riding on the rice transplanter  1  and a case where no person is riding on the rice transplanter  1 . Moreover, the work vehicle according to the present invention is not limited to the rice transplanter  1 , but may be for example a seeder, a tractor, or a combine harvester. 
     As illustrated in  FIGS. 1 and 2 , the rice transplanter  1  includes a vehicle body portion  11 , front wheels  12 , rear wheels  13 , and a planting portion (work machine)  14 . The front wheels  12  and the rear wheels  13  are provided as pairs on the right and left of the vehicle body portion  11 . 
     The vehicle body portion  11  includes a hood  21 . The hood  21  is provided in a front portion of the vehicle body portion  11 . An engine  22  is provided inside the hood  21 . 
     Power generated by the engine  22  is transmitted to the front wheels  12  and the rear wheels  13  via a transmission case  23 . The power is also transmitted to the planting portion  14  via the transmission case  23  and a PTO shaft  24  provided in a rear portion of the vehicle body portion  11 . 
     The vehicle body portion  11  further includes a driver seat  25  where the user sits and a plurality of operating tools. The driver seat  25  is provided between the front wheels  12  and the rear wheels  13  in a front-back direction of the vehicle body portion  11 . The operating tools include, for example, a steering wheel  26  and a gearshift operation pedal  27 . 
     The user operates the steering wheel  26  to change the traveling direction of the rice transplanter  1 . The user operates the gearshift operation pedal  27  to adjust the traveling velocity (vehicle velocity) of the rice transplanter  1 . 
     The planting portion  14  is provided behind the vehicle body portion  11 . The planting portion  14  is coupled to the vehicle body portion  11  via a lifting/lowering link mechanism  31 . The lifting/lowering link mechanism  31  is configured by a parallel link including a top link  31   a  and a lower link  31   b.    
     A lifting/lowering cylinder  32  is coupled to the lower link  31   b . As the lifting/lowering cylinder  32  expands and contracts, the planting portion  14  is lifted and lowered in a vertical direction with respect to the vehicle body portion  11 . Furthermore, although the lifting/lowering cylinder  32  is a hydraulic cylinder according to the present embodiment, an electric cylinder may be used. 
     The planting portion  14  includes a planting entry case portion  33 , a plurality of planting units  34 , a seedling placement table  35 , a plurality of floats  36 , and a preliminary seedling table  37 . The planting portion  14  may sequentially supply a seedling to each of the planting units  34  from the seedling placement table  35  to continuously plant the seedlings. 
     Each of the planting units  34  includes a planting transmission case portion  41  and a rotary case portion  42 . Power is transmitted to the planting transmission case portion  41  via the PTO shaft  24  and the planting entry case portion  33 . 
     The rotary case portion  42  is rotatably attached to the planting transmission case portion  41 . The rotary case portions  42  are provided on both sides of the planting transmission case portion  41  in a vehicle width direction. Two planting claws  43  are attached to one side of each of the rotary case portions  42 . 
     The two planting claws  43  are aligned in the traveling direction of the rice transplanter  1 . The two planting claws  43  are displaced in accordance with the rotation of the rotary case portion  42 . By the displacement of the two planting claws  43 , the seedlings corresponding to one row are planted. 
     The seedling placement table  35  is provided at a front upper side of the planting units  34 . On the seedling placement table  35 , a seedling mat may be placed. The seedling placement table  35  is configured so as to supply the seedlings of the seedling mat placed on the seedling placement table  35  to each of the planting units  34 . 
     Specifically, the seedling placement table  35  is configured to be movable transversely (slidable in a transverse direction) so as to reciprocate in the vehicle width direction. Furthermore, the seedling placement table  35  is configured to convey the seedling mat longitudinally downward and intermittently at the end of reciprocating movement of the seedling placement table  35 . 
     The floats  36  are provided in a lower portion of the planting portion  14  so as to be swingable. A lower surface of the float  36  may be in contact with the surface of the field to obtain the stable planting posture of the planting portion  14  with respect to the surface of the field. 
     The preliminary seedling tables  37  are provided as a pair on the right and left of the vehicle body portion  11 . The preliminary seedling tables  37  are provided on the outer side of the hood  21  in the vehicle width direction. On the preliminary seedling table  37 , a seedling box containing preliminary mat seedlings may be placed. 
     Upper portions of the preliminary seedling tables  37  in a pair on the right and left are coupled to each other via a coupling frame  28  extending in the vertical direction and the vehicle width direction. At the center of the coupling frame  28  in the vehicle width direction, a chassis  29  is provided. In the chassis  29 , a positioning antenna  61 , an inertial measurement device  62 , and a communication antenna  63  are provided. 
     The positioning antenna  61  receives radio waves (positioning signals) from a positioning satellite that forms a satellite positioning system (GNSS). 
     The inertial measurement device  62  specifies the posture, acceleration, and the like, of the rice transplanter  1 . The inertial measurement device  62  includes three gyroscope sensors (angular velocity sensors) and three acceleration sensors. This allows the inertial measurement device  62  to specify the angular velocity of the posture change of the rice transplanter  1  and the accelerations in the three axial directions (front-back direction, right-left direction, and up-down direction). Furthermore, the posture (roll angle, pitch angle, and yaw angle) of the rice transplanter  1  may be specified by integrating the angular velocity. 
     The communication antenna  63  is an antenna to perform a wireless communication with a wireless communication terminal  7  illustrated in  FIG. 3 . 
     A control unit  50  includes an arithmetic device, a storage device, an input/output unit, and the like, which are not illustrated. The storage device stores various types of programs and data, and the like. The arithmetic device may read and execute various programs from the storage device. The control unit  50  may operate as a travel control unit  51  and a work machine control unit  52  due to the cooperation of the above-described hardware and software. The control unit  50  may be a single piece of hardware or a plurality of pieces of hardware that may communicate with each other. Further, the control unit  50  is coupled to a position acquisition unit  64 , a communication processing unit  65 , a vehicle velocity sensor  66 , and a steering angle sensor  67  in addition to the inertial measurement device  62  described above. 
     The position acquisition unit  64  is electrically connected to the positioning antenna  61 . The position acquisition unit  64  acquires, from a positioning signal received by the positioning antenna  61 , the position of the rice transplanter  1  as for example information on the latitude and the longitude. The position acquisition unit  64  receives a positioning signal from a reference station  120  by an appropriate method and then performs positioning using the known GNSS-RTK method. In place of this, for example, positioning using differential GNSS, independent positioning, or the like, may be performed. Alternatively, position acquisition based on the radio field intensity of a wireless LAN, or the like, position acquisition by inertial navigation, etc. may also be performed. 
     The communication processing unit  65  is electrically connected to the communication antenna  63 . The communication processing unit  65  may perform modulation processing or demodulation processing by an appropriate method to transmit and receive data to and from the wireless communication terminal  7 . 
     The vehicle velocity sensor  66  detects the vehicle velocity of the rice transplanter  1 . The vehicle velocity sensor  66  is provided at an appropriate position of the rice transplanter  1 , e.g., at a wheel axis of the front wheel  12 . In this case, the vehicle velocity sensor  66  generates the pulse corresponding to the rotation of the wheel axis of the front wheel  12 . Data on a detection result obtained by the vehicle velocity sensor  66  is output to the control unit  50 . 
     The steering angle sensor  67  detects the steering angle of the front wheel  12 . The steering angle sensor  67  is provided at an appropriate position of the rice transplanter  1 , e.g., at a kingpin, not illustrated, provided on the front wheel  12 . Furthermore, the steering angle sensor  67  may be provided on the steering wheel  26 . Data on a detection result obtained by the steering angle sensor  67  is output to the control unit  50 . 
     The travel control unit  51  performs control regarding the travel of the rice transplanter  1 . For example, the travel control unit  51  may perform vehicle velocity control and steering control. The travel control unit  51  may simultaneously perform both vehicle velocity control and steering control or may perform only steering control. In the latter case, the user uses the gearshift operation pedal  27  to control the vehicle velocity of the rice transplanter  1 . 
     During the vehicle velocity control, the vehicle velocity of the rice transplanter  1  is adjusted based on a predetermined condition. During the vehicle velocity control, specifically, the travel control unit  51  performs control so that the current vehicle velocity obtained from a detection result of the vehicle velocity sensor  66  becomes close to a target vehicle velocity. This control is performed by changing at least either the transmission gear ratio of a gearshifter in the transmission case  23  or the rotational velocity of the engine  22 . Moreover, this vehicle velocity control includes the control to bring the vehicle velocity to zero so that the rice transplanter  1  stops. 
     The steering control is the control to adjust the steering angle of the rice transplanter  1  based on a predetermined condition. During the steering control, specifically, the travel control unit  51  performs control so that the current steering angle obtained from a detection result of the steering angle sensor  67  becomes close to a target steering angle. This control is performed by, for example, driving a steering actuator provided on a rotary shaft of the steering wheel  26 . Moreover, with regard to the steering control, the travel control unit  51  may directly adjust the steering angle (wheel) of the front wheel  12  of the rice transplanter  1  instead of the rotation angle (steering angle) of the steering wheel  26 . 
     The work machine control unit  52  may control the operation (lifting/lowering operation, planting work, etc.) of the planting portion  14  based on a predetermined condition. 
     The wireless communication terminal  7  is a tablet terminal including a communication antenna  71 , a communication processing unit  72 , a display unit  73 , an operating unit  74 , a storage unit  75 , and an arithmetic unit  80 . Furthermore, the wireless communication terminal  7  is not limited to a tablet terminal, but may be a smartphone or a notebook computer. Although the wireless communication terminal  7  performs various kinds of processing regarding autonomous travel of the rice transplanter  1 , the control unit  50  of the rice transplanter  1  may perform at least part of such processing. Conversely, the wireless communication terminal  7  may perform at least a part of the various kinds of processing regarding autonomous travel conducted by the control unit  50  of the rice transplanter  1 . 
     The communication antenna  71  is a short-range communication antenna to perform a wireless communication with the rice transplanter  1 . The communication processing unit  72  is electrically connected to the communication antenna  71 . The communication processing unit  72  performs modulation processing on transmission signals, demodulation processing on reception signals, etc. Furthermore, either the rice transplanter  1  or the wireless communication terminal  7  includes a mobile communication antenna to perform a communication using a mobile phone line and the Internet. Thus, for example, part of the information stored in the rice transplanter  1  or the wireless communication terminal  7  may be stored on an external server, or information may be acquired from an external server. 
     The display unit  73  is a liquid crystal display or an organic EL display and is configured to display images. The display unit  73  may display, for example, information about autonomous travel, information about settings of the rice transplanter  1 , detection results of various sensors, warning information, etc. 
     The operating unit  74  includes a touch panel and a hardware key. The touch panel is provided on the display unit  73  in a superimposed manner and is capable of detecting operations by a user&#39;s finger, or the like. The hardware key is provided on a side surface of a chassis of the wireless communication terminal  7 , around the display unit  73 , or the like, and may be operated by user&#39;s pressing. Further, the wireless communication terminal  7  may be configured to include only either the touch panel or the hardware key. 
     The storage unit  75  is a non-volatile memory such as a flash memory or a hard disk. The storage unit  75  stores, for example, information about autonomous travel. 
     The arithmetic unit  80  is an arithmetic device such as a CPU. The arithmetic unit  80  may read and execute various programs from the storage unit  75 . The arithmetic unit  80  may operate as a display control unit  81 , a map acquisition unit  82 , a field specifying unit  83 , a division unit  84 , a correction unit  85 , and a route creation unit  86  due to the cooperation of the above-described hardware and software. 
     Next, with reference to  FIG. 4 , a field and a travel route for autonomous travel will be described. The field includes a work area and a headland area. The work area is an area located at a central part of the field to perform a work. The headland area is an area located outside the work area and is used to appropriately perform a work in the work area. For example, the headland area is used to cause the rice transplanter  1 , which has entered the field, to move to a start position of the work in the work area. Further, the headland area is also used as an area to cause the rice transplanter  1  to turn. 
     The route creation unit  86  creates a travel route  91  along which the rice transplanter  1  autonomously travels. As illustrated in  FIG. 4 , the travel route  91  includes a plurality of linear routes  91   a  and a plurality of turning routes  91   b . Furthermore, a start position (S in  FIG. 4 ) and an end position (G in  FIG. 4 ) are set for the travel route  91 . Furthermore, the travel route  91  illustrated in  FIG. 4  is an example, and the rice transplanter  1  may autonomously travel along a route having a different feature. The above-described travel control unit  51  performs at least steering control so that the rice transplanter  1  moves along the travel route  91 . 
     Next, with reference to  FIGS. 5 to 10 , the process to register a field is described. Although the wireless communication terminal  7  performs the process illustrated in the flowchart of  FIG. 5 , the control unit  50  may perform some of the process. Furthermore, the image described below is displayed on the wireless communication terminal  7 , but may also be displayed on a display at the side of the rice transplanter  1  or on another terminal. 
     First, the map acquisition unit  82  of the wireless communication terminal  7  acquires an orthophoto (S 101 ). Orthophotos are obtained by conducting orthorectification on aerial photographs (central projection) captured by an aircraft or satellite to correct a distortion by orthographic projection transformation. Orthophotos may accurately represent the shape and position of terrain. The map acquisition unit  82  may acquire an orthophoto stored in a storage device of the rice transplanter  1  or the wireless communication terminal  7  or may communicate with an external unit to acquire an orthophoto. In the case of a communication with an external unit, it is preferable to select and acquire an orthophoto near the position acquired by the position acquisition unit  64 . Furthermore, in this description, the orthophoto includes not only an image obtained by conducting orthorectification on an aerial photograph but also an image obtained by conducting additional correction on the image having undergone orthorectification. The additional correction includes, for example, correction to convert an orthophoto in a photographic form into a linear drawing form and correction to add information such as a building and a place name. 
     Subsequently, the field specifying unit  83  of the wireless communication terminal  7  specifies a field area based on the acquired orthophoto (S 102 ). In the example illustrated in  FIG. 7 , the area marked with dots corresponds to a field area. The field specifying unit  83  executes for example image recognition on the orthophoto to specify a field area. The field area is an area where a field (a place to grow crops) exists. Here, the field contains for example soil or crops and often has a geometric configuration such as a polygon. Furthermore, a plurality of fields is often adjacently located. An orthophoto is analyzed based on these tendencies so as to specify a field. Alternatively, machine learning may be applied to an image of the field to configure a model, and this model may be used to specify the field included in the orthophoto. Moreover, there is no limitation on the configuration in which the field specifying unit  83  specifies the field from the orthophoto, and information (vector data such as polygon data) indicating the position and shape of the field may be acquired from, for example, an external server. 
     Subsequently, the division unit  84  of the wireless communication terminal  7  divides the field area into unit field areas (S 103 ). A unit field area is a division of a field area into each continuous field area (in other words, each one of the fields). In the example illustrated in  FIG. 7 , the area surrounded by a dashed line is a unit field area. For example, when the field area specified at Step S 102  is divided into two by a road, or the like, the division unit  84  sets the two divided areas as unit field areas. Furthermore, the division unit  84  assigns identification information to each unit field area. Therefore, information (e.g., a field name attached by a user, registration date, etc.) may be registered in association with a unit field area. 
     Moreover, instead of the configuration in which the division unit  84  divides the field area into unit field areas, the wireless communication terminal  7  may acquire the information on divided unit field areas from an external unit. 
     Subsequently, the display control unit  81  of the wireless communication terminal  7  causes the wireless communication terminal  7  to display the orthophoto and the field area in a superimposed manner (S 104 ). As illustrated in  FIG. 6 , the display control unit  81  superimposes the orthophoto and the image representing the field area created from the orthophoto to create a display image. Then, as illustrated in  FIG. 7 , the display control unit  81  performs the process to display this display image on the display unit  73  of the wireless communication terminal  7 . As the orthophoto contains information (building, river, road, etc.) other than the field, displaying the orthophoto and the field area in a superimposed manner makes it easy for the user to identify the desired field. 
     Furthermore, although the orthophoto and the image representing the field area are both superimposed according to the present embodiment, another image may be further superimposed. Another image to be superimposed may be a map associating a position (area) with usage, such as a land use map or city planning map. 
     Furthermore, as a map created by the commonly used Mercator projection contains distortions, the accurate shape of the field is sometimes not represented. Therefore, there is a possibility that, when the map created by Mercator projection and the field area created by the actual travel of the rice transplanter  1  are superimposed, the field represented on the map does not match the created field area. In this respect, as the orthophoto represents the accurate shape of the field, the field represented on the map matches the created field area. Thus, the map and the field area may be superimposed without providing the user a feeling of strangeness. 
     Hereinafter, the image obtained by superimposing the orthophoto and the field area is referred to as a superimposed image. The user checks the superimposed image illustrated in  FIG. 7 . For example, as illustrated in the lower section of  FIG. 7 , the user selects a unit field area so as to check the information about the selected unit field area. The information about the unit field area includes, for example, the field name, address, and registration date. Furthermore, the field name may be changed in accordance with the user input. 
     Furthermore, the user views the superimposed image to check the shape and division of a unit field area. The user determines whether the unit field area needs to be corrected, and if correction is necessary, operates the wireless communication terminal  7  to make correction. 
     As illustrated in  FIG. 7 , the wireless communication terminal  7  displays buttons indicating shape changing, combining, dividing, and deleting. These buttons are used to correct a unit field area. The correction unit  85  of the wireless communication terminal  7  determines whether the instruction for correction has been given based on whether the user operates these buttons (S 105 ). Then, when it is determined that these buttons have been operated, the correction unit  85  corrects the unit field area in accordance with the user&#39;s operation (S 106 ). 
     The correction on the unit field area is described in detail below. The autonomous travel system  100  according to the present embodiment is configured so as to execute shape changing, combining, dividing, and deleting as correction on the unit field area. 
     First, the shape change of the unit field area is described with reference to  FIG. 8 . For example, when the shape of the unit field area is different from the actual field, or when there is an undesired area that is not to be registered as a field because of the difficulty in work due to its shape, difference in level, etc., the user gives an instruction to change the shape of the unit field area. 
     Specifically, the user operates the button “Shape Change” displayed on the wireless communication terminal  7 , selects one unit field area, which is the target to be changed in shape, from the unit field areas displayed on the wireless communication terminal  7 , and confirms the selection. Then, the user gives an instruction to change the shape in detail. The shape change includes the process to add an additional area to the selected unit field area and the process to remove a removal area from the selected unit field area. 
     Although there are various methods for designating an additional area and a removal area, a configuration may be such that the user draws a line with the finger, a stylus, or the like, on the map displayed on the wireless communication terminal  7  to designate an additional area or a removal area. Here, the correction unit  85  may adjust the angle of the line drawn by the user such that the line becomes parallel to any edge of the selected unit field area. This is because it is desirable that the edge of the field is parallel as a plurality of parallel linear routes is often created as travel routes. Furthermore, instead of the process to draw the line by the user, a configuration may be such that the user performs the process to move the edge line (including an extended line of the edge line) of the selected unit field area to designate an additional area or a removal area. Here, the correction unit  85  may adjust the moving direction, or the like, of the edge line such that the edge line of the unit field area moves in parallel. 
     The correction unit  85  adds an additional area to the selected unit field area or removes a removal area from the selected unit field area to change the shape of the unit field area. 
     With reference to  FIG. 9 , combining the unit field areas is described below. When one field is specified as a plurality of unit field areas, the user gives an instruction to combine the unit field areas. For example, one field may be specified as a plurality of unit field areas in a case where there are two fields when the orthophoto is taken and then the fields are combined into one by removing a farm road, or the like, or in a case where a certain line appearing on the field is mistakenly recognized as a road during image recognition of the orthophoto. 
     The user operates the button “Combine” displayed on the wireless communication terminal  7 , selects a plurality of unit field areas, which is the target to be combined, from the unit field areas displayed on the wireless communication terminal  7 , and confirms the selection. Furthermore, after a first unit field area is selected, the correction unit  85  performs the process to specify unit field areas whose distance from the selected first unit field area is less than a threshold so that only the unit field areas are selectable. This may prevent the selection of unit field areas that are far apart and cannot be combined. Alternatively, after the user selects and confirms a plurality of unit field areas, the correction unit  85  may determine based on the distance whether the selected unit field areas may be combined, and if it is difficult to combine them, display a message on the wireless communication terminal  7 . 
     The correction unit  85  combines the unit field areas selected by the user to create a new unit field area. Furthermore, new identification information or the identification information on any of the unit field areas before combining may be assigned to the new unit field area. 
     Division of the unit field area is described below with reference to  FIG. 10 . When a plurality of fields is specified as one unit field area, the user gives an instruction to divide the unit field area. For example, a plurality of fields may be specified as one unit field area in a case where there is one field when the orthophoto is taken and then the field is divided into a plurality of fields due to the construction of a farm road, or the like, or in a case where it is difficult to recognize a farm road, or the like, in the field during image recognition of the orthophoto. 
     The user operates the button “Divide” displayed on the wireless communication terminal  7 , selects one unit field area, which is the target to be divided, from the unit field areas displayed on the wireless communication terminal  7 , and confirms the selection. Then, the user designates a specific division position. The division position is designated when the user draws a line (straight line or curve) or moves an edge line in the same way as for shape change. Furthermore, the division position may be designated to divide the unit field area into two, or the division position may be designated to divide the unit field area into three or more. Moreover, the line width (the width of a farm road) may be designated by, for example, inputting a numerical value. The portion corresponding to the line width is excluded from the field area after division. 
     Furthermore, for division at an appropriate position, a configuration may be such that an instruction for division is given by using a travel trajectory obtained by the actual travel of the rice transplanter  1 . Specifically, the rice transplanter  1  travels along a dike of the field to be divided. Then, this travel trajectory is moved in parallel in accordance with the width (designated value) of the farm road. Then, the travel trajectory and the line obtained by moving the travel trajectory in parallel are used as division positions. Furthermore, as the area between the two division positions (division lines) corresponds to a farm road and is therefore excluded from the field area after division. 
     The correction unit  85  divides the unit field area at the designated division position to create a plurality of new unit field areas. New identification information is assigned to the new unit field area. Furthermore, the identification information on the unit field area before division may be assigned to one of the new unit field areas. 
     Deletion of the unit field area is described below. The user gives an instruction to delete a unit field area when an unnecessary field (e.g., an unmanaged field) is specified as a unit field area or an area that is not a field is specified as a unit field area. Specifically, the button “Delete” displayed on the wireless communication terminal  7  is operated, one or more unit field areas, which are the target to be deleted, are selected from the unit field areas displayed on the wireless communication terminal  7 , and the selection is confirmed. 
     The correction unit  85  performs the process to delete the selected unit field area. Furthermore, the correction unit  85  may actually delete the information on the unit field area to be deleted or may simply hide the unit field area to be deleted. In the latter case, the deleted unit field area may be confirmed later or restored. 
     Furthermore, when the target unit field area is selected for the above-described operations of shape changing, combining, dividing, and deleting, only the unit field area that is displayed in whole on the wireless communication terminal  7  may be selected. That is, in the configuration, even when only part of the unit field area is displayed on the wireless communication terminal  7 , the unit field area is not selectable. This allows the correction of the unit field area only in a situation where the user is able to confirm the entire shape of the unit field area. 
     After the correction of the unit field area has been completed as described above, for example, the user operates the confirmation button to instruct the wireless communication terminal  7  that the correction of the unit field area has been completed. In response to this instruction, the arithmetic unit  80  stores the information on the corrected unit field area in the storage unit  75  or an external server to register the field (S 107 ). 
     When the route creation unit  86  creates a travel route, information on the registered field is referred to. Here, a map created by the commonly used Mercator projection contains distortions, and therefore when a field is registered based on the map, the field having the accurate shape or the field having the shape intended by the user is sometimes not registered. Conversely, as the orthophoto represents the accurate shape of the field, the field having the accurate shape or the shape intended by the user may be easily registered based on the map. 
     As described above, the autonomous travel system  100  according to the present embodiment includes the map acquisition unit  82 , the field specifying unit  83 , the route creation unit  86 , and the travel control unit  51 . The map acquisition unit  82  acquires an orthophoto. The field specifying unit  83  specifies the field area included in the map of the orthophoto acquired by the map acquisition unit  82 . The route creation unit  86  creates a travel route along which the rice transplanter  1  autonomously travels in the field area specified by the field specifying unit  83 . The travel control unit  51  causes the rice transplanter  1  to autonomously travel along the travel route created by the route creation unit  86 . 
     Thus, by using the field area created based on the orthophoto, it is possible to properly register the field and conduct autonomous travel along an appropriate travel route without the actual travel in the field to register the field. 
     Furthermore, the autonomous travel system  100  according to the present embodiment includes the display unit  73  that displays an image. The display unit  73  displays the image combining the map acquired by the map acquisition unit and the field area specified by the field specifying unit  83 . 
     Thus, by specifying the field area from the map, the position of the specified field matches the position of the field on the map. As a result, the display positions of them may match on the screen of the display unit. 
     Furthermore, the autonomous travel system  100  according to the present embodiment includes the division unit  84  and the correction unit  85 . The division unit  84  further divides the field area into a plurality of unit field areas. The correction unit  85  removes a designated area from the unit field area or adds a designated area to the unit field area to update the unit field area. 
     Thus, the unit field area may be updated so as to have an appropriate shape in a case where an unnecessary area is set as a unit field area or a necessary area is not set as a unit field area. 
     Furthermore, the correction unit  85  in the autonomous travel system  100  according to the present embodiment combines the plurality of designated unit field areas to obtain one new unit field area. 
     Thus, it is possible to combine unit field areas in a situation where, for example, it is desirable to process them as one unit field area although they are divided as a plurality of unit field areas. 
     Further, the correction unit  85  in the autonomous travel system  100  according to the present embodiment divides one designated unit field area to obtain a plurality of new unit field areas. 
     Thus, it is possible to divide a unit field area in a situation where, for example, it is desirable to process it as a plurality of unit field areas although it is divided as one unit field area. 
     Although preferred embodiments of the present invention have been described above, the above-described configuration may be modified as below, for example. 
     The flowchart described in the above embodiment is an example; some processing may be omitted, the content of some processing may be changed, or new processing may be added. For example, when the wireless communication terminal  7  displays only the field area, the process at Step S 104  may be omitted. Further, when the unit field area may be accurately divided based on the above-described land use map, or the like, the inquiry regarding correction of the unit field area may be omitted. 
     In the above embodiment, all of shape changing, combining, dividing, and deleting may be performed as correction on the unit field area; however, it is appropriate if only at least one of them may be performed. Moreover, it may also be possible to perform the process to create a new unit field area based on a line, or the like, drawn by the user. 
     In the above embodiment, the process to register a field by the actual travel around the outer periphery of the field is not required; however, this function may be performed. That is, it may be possible to switch between the process to specify the field area based on the orthophoto and the process to specify the field area by the actually travel around the outer periphery of the field in accordance with the user&#39;s instruction, etc. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
         
           
               1  Rice transplanter (work vehicle) 
               7  Wireless communication terminal 
               50  Control unit 
               51  Travel control unit 
               80  Arithmetic unit 
               81  Display control unit 
               82  Map acquisition unit 
               83  Field specifying unit 
               84  Division unit 
               85  Correction unit 
               86  Route creation unit 
               100  Autonomous travel system