Patent Publication Number: US-2022232750-A1

Title: Automatic Travel System for Work Vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to an automatic travel system for a work vehicle that enables automatic travel of a work vehicle, such as a tractor, a riding mower, a riding rice transplanter, a riding sowing machine, a riding fertilizer application machine, a combine harvester, and an unmanned mower. 
     BACKGROUND ART 
     An automatic travel system for a work vehicle, for example, includes a replenishment position setting unit that sets a replenishment position (an example of a standby position) of materials at a position specified by a user, and is configured to cause the work vehicle to travel automatically to the above-described replenishment position and to stand by at the replenishment position when the work vehicle needs to be replenished with the materials (for example, see Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2018-050491 
       
    
     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     In the automatic driving system for a work vehicle described in Patent Literature 1, the replenishment position of the materials is set at a single position that is specified by the user in advance using a replenishment position setting window shown on a display of a wireless communication terminal. Accordingly, for example, the set replenishment position may be unsuitable for a reason for the standby of the work vehicle (in this case, the replenishment of the materials), a work condition, or the like because, in reality, there is an obstacle such as a tree in the vicinity of the replenishment position, which interferes with the replenishment of the materials to the work vehicle, or because the replenishment position is far from a current position of the work vehicle, which requires the replenishment of the materials, and thus it takes time to move the work vehicle to the replenishment position. 
     In order to prevent occurrence of the inconveniences as described above, it is necessary for the user to specify an appropriate replenishment position in full consideration of the reason for the standby of the work vehicle, the work situation, and the like. In addition, in the case where any of the inconveniences as described above occurs, the user has to specify the replenishment position again. Therefore, a burden on the user to specify the appropriate replenishment position is increased. 
     In view of this circumstance, a primary object of the present invention is to provide an automatic travel system for a work vehicle capable of setting a standby position suitable for a reason for standby of a work vehicle, a work situation, and the like while reducing a burden on a user. 
     Means for Solving the Problems 
     A first characteristic configuration of the present invention is in a point that an automatic travel system for a work vehicle includes: an automatic travel control section that causes a work vehicle to travel automatically along a target path at a registered work site by using a satellite positioning system; and a standby position setting section that sets a standby position of the work vehicle, in which the standby position setting section acquires an entry point at a time of entering the registered work site from outside the registered work site and sets the entry point as the standby position, and in which the automatic travel control section determines whether a standby condition to cause the work vehicle to stand by at the standby position is satisfied and, in the case where the standby condition is satisfied, causes the work vehicle to travel automatically from a current position to the standby position and to stand by at the standby position. 
     With such a configuration, it is possible to set the standby position suited for a reason for standby of the work vehicle, a work situation, and the like while reducing a burden on a user. 
     A second characteristic configuration of the present invention is in a point that an automatic travel control section that causes a work vehicle to travel automatically along a target path at a registered work site by using a satellite positioning system and a standby position setting section that sets a standby position of the work vehicle are provided, the standby position setting section sets an intersection point of an extension line of a work path included in the target path with an outline of the registered work site, as the standby position, and the automatic travel control section determines whether a standby condition to cause the work vehicle to stand by at the standby position is satisfied and, in the case where the standby condition is satisfied, causes the work vehicle to travel automatically from a current position to the standby position and to stand by at the standby position. 
     With such a configuration, it is possible to set the standby position suited for the reason for the standby of the work vehicle, the work situation, and the like while reducing the burden on a user. 
     A fourth characteristic configuration of the present invention is in a point that an automatic travel control section that causes a work vehicle to travel automatically along a target path at a registered work site by using a satellite positioning system, a standby position setting section that sets a standby position of the work vehicle at plural locations in the registered work site, a standby position selection section that selects a single standby position from the plural standby positions are provided, and the automatic travel control section determines whether a standby condition to cause the work vehicle to stand by at the standby position is satisfied and, in the case where the standby condition is satisfied, causes the work vehicle to travel automatically from a current position to the standby position selected by the standby position selection section and to stand by at the standby position. 
     With such a configuration, it is possible to select the standby position suited for the work situation, such as the current position of the work vehicle, or the like which varies from time to time when the above-described standby condition is satisfied, while reducing the burden on the user. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view illustrating a schematic configuration of an automatic travel system for a work vehicle. 
         FIG. 2  is a schematic diagram illustrating a transmission configuration of a tractor. 
         FIG. 3  is a block diagram illustrating the schematic configuration of the automatic travel system. 
         FIG. 4  is a block diagram illustrating a schematic configuration of an obstacle detection system. 
         FIG. 5  is a plan view illustrating a target path, a standby position, and the like of a work vehicle in a field (registered work site) in a first embodiment. 
         FIG. 6  is a view illustrating a state where a display screen of a display device is switched to a registered field display screen. 
         FIG. 7  is a view illustrating a state where the display screen of the display device is switched to a selected field display screen. 
         FIG. 8  is a view illustrating a state where the display screen of the display device is switched to a work device selection screen. 
         FIG. 9  is a view illustrating a state where the display screen of the display device is switched to a headland area setting screen. 
         FIG. 10  is a view illustrating a state where the display screen of the display device is switched to a work condition setting screen. 
         FIG. 11  is a flowchart of standby position acquisition control in the first embodiment. 
         FIG. 12  is a flowchart of seed replenishment movement control. 
         FIG. 13  is a plan view illustrating the target paths, the standby positions, and the like of the work vehicles for side-by-side work in the field (registered work site) in the first embodiment. 
         FIG. 14  is a plan view illustrating a target path, a replenishment standby position (a standby position), and the like of a work vehicle in a field (registered work site) in a second embodiment. 
         FIG. 15  is a partial plan view illustrating an off-field movement path, an off-field standby position (a standby position), and the like of the work vehicle in the field (registered work site) in the second embodiment. 
         FIG. 16  is a flowchart of standby position acquisition control in the second embodiment. 
         FIG. 17  is a flowchart of seedling replenishment movement control in the second embodiment. 
         FIG. 18  is a flowchart of the seedling replenishment movement control in the second embodiment. 
         FIG. 19  is a flowchart of off-field movement path acquisition control in the second embodiment. 
         FIG. 20  is a plan view illustrating a target path, a discharge standby position (a standby position), and the like of a work vehicle in a field (registered work site) in a third embodiment. 
         FIG. 21  is a plan view illustrating the target path, the plural discharge standby positions (standby positions), and the like of the work vehicle in the field (registered work site) in the third embodiment. 
         FIG. 22  is a flowchart of grain discharge movement control in the third embodiment. 
         FIG. 23  is a plan view illustrating a target path, an evacuation standby position (a standby position), and the like of a work vehicle in a landing area (registered work site) in a fourth embodiment. 
         FIG. 24  is a plan view illustrating an example of the evacuation standby positions (the standby positions), an evacuation path, and the like of the work vehicle selected in a vegetated area (work area) of a landing area (registered work site) in the fourth embodiment. 
         FIG. 25  is a plan view illustrating an example of the evacuation standby positions (the standby positions), the evacuation path, and the like of the work vehicle selected in the vegetated area (work area) of the landing area (registered work site) in the fourth embodiment. 
         FIG. 26  is a plan view illustrating an example of the evacuation standby positions (the standby positions), the evacuation path, and the like of the work vehicle selected in the vegetated area (work area) of the landing area (registered work site) in the fourth embodiment. 
         FIG. 27  is a flowchart of standby position selection control in the fourth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     A description will hereinafter be made on, as an example of a mode for carrying out the present invention, a first embodiment in which the automatic travel system for a work vehicle according to the present invention is applied to a tractor as an example of the work vehicle with reference to the drawings. 
     The automatic travel system for a work vehicle according to the present invention can be applied to, in addition to the tractor, riding work vehicles, such as a riding rice transplanter, a combine harvester, a riding mower, a snowplow, and a wheel loader, and unmanned work vehicles such as an unmanned cultivator and an unmanned mower, for example. 
     As illustrated in  FIG. 1 , in a tractor V 1  exemplified in this first embodiment, a work device for sowing (hereinafter referred to as a sowing device)  3  is coupled to a rear portion via a three-point linkage mechanism  2 . In this way, this tractor V 1  is configured for a sowing specification to perform sowing work using the sowing device  3 , which is coupled to the rear portion thereof. The sowing device  3  is coupled to the rear portion of the tractor V 1  in a liftable and rollable manner. 
     Instead of the sowing device  3 , any of various work devices such as a fertilizer application device, a fertilizer sowing device, a chemical spraying device, a rotary cultivator, a plow, a disc harrow, a cultivator, a subsoiler, and a mower can be coupled to the rear portion of this tractor V 1 . 
     By using the automatic travel system for a work vehicle, the tractor V 1  can travel automatically in fields Aa to Ag illustrated in  FIGS. 5 to 6 , which are exemplified as registered work sites, and the like. The fields Aa to Ag exemplified in  FIGS. 5 to 6  are the fields Aa, Ab, Ad to Af in rectangular outer shapes and the deformed fields Ac, Ag in trapezoidal outer shapes. However, each of the registered fields may be the deformed field in a triangular or pentagonal outer shape, or may be the deformed field having a curved portion in at least one side of the outer shape. 
     As illustrated in  FIG. 1  and  FIG. 3 , the automatic travel system for a work vehicle includes: an automatic travel unit  4  mounted on the tractor V 1 ; and a mobile communication terminal  5  as an example of wireless communication equipment that is set to be wirelessly communicable with the automatic travel unit  4 . The mobile communication terminal  5  includes a multi-touch type display device (for example, a liquid crystal panel)  50  that allows various information displays, input operations, and the like related to automatic travel. 
     A tablet-type personal computer, a smartphone, or the like can be adopted as the mobile communication terminal  5 . For the wireless communication, wireless local area network (LAN) such as Wi-Fi®, short-range wireless communication such as Bluetooth®, or the like can be adopted. 
     As illustrated in  FIGS. 1 to 2 , the tractor V 1  includes: a front frame  10  that are arranged in a front portion thereof; right and left front wheels  11  that are steerable and drivable; right and left rear wheels  12  that are drivable; an electronically-controlled diesel engine (hereinafter referred to as the engine)  13  that has a common rail system; a main clutch  14  that connects/disconnects power from the engine  13 ; a transmission unit  15  that shifts the power transmitted through the main clutch  14 ; a hood  16  that covers the engine  13  and the like; a cabin  17  that is arranged in the rear portion of the tractor V 1 ; and the like. An electronically-controlled gasoline engine having an electronic governor, or the like may be adopted as the engine  13 . 
     As illustrated in  FIG. 2 , the right and left front wheels  11  are steerably coupled to right and left ends of a front axle case  18 , which is supported in a rollable manner by the front frame  10 , via right and left front wheel gear cases  19 , respectively. The right and left rear wheels  12  are supported by right and left rear axle cases (not illustrated) that are provided behind the transmission unit  15 . The engine  13  is vibration-isolated and supported by the front frame  10 . 
     As illustrated in  FIG. 2 , the transmission unit  15  has: a travel transmission system  15 A that shifts the power from the engine  13  for travel; and a work transmission system  15 B that shifts the power from the engine  13  for work. 
     The travel transmission system  15 A includes: an electronically-controlled primary transmission  20  that shifts the power from the engine  13 ; an electro-hydraulically controlled forward-reverse switching device  21  that switches the power from the primary transmission  20  for forward travel or reverse travel; a gear-type secondary transmission  22  that shifts the power from the forward-reverse switching device  21  for the forward travel or the reverse travel at one of two high and low stages; a gear-type creep transmission  23  that shifts the power for the forward travel or the reverse travel from the forward-reverse switching device  21  to an ultra-low speed stage; a rear-wheel differential  24  that distributes the power from the secondary transmission  22  or the creep transmission  23  to the right and left rear wheels  12 ; right and left reduction gears  25  that decelerate the power from the rear-wheel differential  24  and transmits the decelerated power to the right and left rear wheels  12 , respectively; an electro-hydraulically controlled transmission switching device  26  that switches transmission of the power from the secondary transmission  22  or the creep transmission  23  to the right and left front wheels  11 . 
     The work transmission system  15 B includes: a hydraulic PTO clutch  27  that connects/disconnects the power from the engine  13 ; a PTO transmission  28  that switches the power transmitted through the PTO clutch  27  to one of three forward stages and one reverse stage; a PTO shaft  29  that outputs the power from the PTO transmission  28  for work; and the like. 
     The transmission unit  15  includes right and left brakes  30  that separately brake the right and left rear wheels  12 , respectively. 
     As the primary transmission  20 , an integrated hydrostatic mechanical transmission (I-HMT), which is an example of a hydromechanical continuously variable transmission having higher transmission efficiency than a hydrostatic transmission (HST), is adopted. 
     Instead of the I-HMT, a continuously variable transmission, such as a hydraulic mechanical transmission (HMT) as an example of the hydromechanical continuously variable transmission, the hydrostatic transmission, or a belt-type continuously variable transmission, may be adopted as the primary transmission  20 . Alternatively, instead of the continuously variable transmission, an electro-hydraulically controlled stepped transmission having plural hydraulic shift clutches, plural electromagnetic shift valves that control oil flows thereto, and the like may be adopted. 
     The transmission switching device  26  switches a transmission state to the right and left front wheels  11  among: a transmission cutoff state in which the transmission to the right and left front wheels  11  is cut off; a constant speed transmission state in which the power is transmitted to the right and left front wheels  11  such that circumferential speeds of the right and left front wheels  11  become the same as circumferential speeds of the right and left rear wheels  12 ; and a double speed transmission state in which the power is transmitted to the right and left front wheels  11  such that the circumferential speeds of the right and left front wheels  11  become approximately twice the circumferential speeds of the right and left rear wheels  12 . The power from the transmission switching device  26  is transmitted to a front-wheel differential  32 , which is built into the front axle case  18 , via a transmission shaft  31  for driving the front wheels and the like. The front-wheel differential  32  distributes the power from the transmission switching device  26  to the right and left front wheels  11 . The distributed power is transmitted to the right and left front wheels  11  through right and left transmission devices (not illustrated) that are built into the right and left front wheel gear cases  19 , respectively. The right and left transmission devices decelerate the power from the front-wheel differential  32  and transmit the decelerated power to the right and left front wheels  11  while allowing steering of the right and left front wheels  11 . The power taken from the PTO shaft  29  is transmitted to the work device via an external transmission shaft (not illustrated) or the like in the case where the work device such as sowing device or the fertilizer application device driven by the power is coupled to the rear portion of the tractor V 1 . 
     As illustrated in  FIG. 1 , the cabin  17  includes therein: a steering wheel  35  for manual steering; an occupant seat  36 ; a multi-touch type liquid crystal monitor  37  that allows the various information displays, the input operations, and the like; and the like. In this way, a boarding-type driving unit that allows an occupant to drive the tractor V 1  is formed in the cabin  17 . 
     Although not illustrated, the driving unit includes: an accelerator lever that can maintain an engine speed at a set speed; an accelerator pedal that can increase the engine speed from the set speed; a clutch pedal that enables an engagement/disengagement operation of the main clutch  14 ; a primary gear shift lever that enables a gear shift operation of the primary transmission  20 ; a reverser lever that enables a forward-reverse switching operation of the forward-reverse switching device  21 ; a secondary gear shift lever that enables a gear shift operation of the secondary transmission  22 ; a creep gear shift lever that enables a gear shift operation of the creep transmission  23 ; a PTO switch that enables an engagement/disengagement operation of the PTO clutch  27 ; a PTO gear shift lever that enables a gear shift operation of the PTO transmission  28 ; right and left brake pedals and a parking lever that enable a switching operation to braking states of the right and left brakes  30 ; and the like. 
     The right and left brakes  30  are mechanically linked to the right and left brake pedals and the parking lever. In the case where one or both of the right and left brakes  30  are depressed to be operated, one or both of the right and left brakes  30  brake the corresponding rear wheels  12  with a braking force that corresponds to a depressed operation amount at the time. In the case where the parking lever is operated and held in a braking range, the right and left brakes  30  brake the right and left rear wheels  12  with the braking force that corresponds to a holding position at the time. 
     As illustrated in  FIG. 1 , the sowing device  3  has: a sowing frame  3 A that is detachably coupled to the three-point linkage mechanism  2 ; and a sowing unit  3 B for the number of working strips. Each of the sowing units  3 B has: a storage section  3 Ba that stores seeds as an example of agricultural materials; a delivery section  3 Bb that delivers a predetermined amount of the seeds from the storage section  3 Ba; a disc-type furrowing device  3 Bc that forms a sowing furrow on a field surface; plural press wheels  3 Bd that press covered soil after sowing; and the like. Although not illustrated, the sowing device  3  has: a ground wheel that is grounded during working travel of the tractor V 1  and rotates in conjunction with the travel of the tractor V 1 ; and a transmission system that transmits rotary power of the ground wheel to the delivery section  3 Bb in each of the sowing units  3 B. Each of the delivery sections  3 Bb is driven by the rotary power from the ground wheel and thereby delivers, per predetermined amount, the seeds that are stored in each of the storage sections  3 Ba. That is, the sowing device  3  is configured in a ground wheel drive mode to perform sowing by the rotary power of the ground wheel. 
     The sowing device  3  may be configured as a PTO-driven type that is driven by the power taken from the PTO shaft  29  or an electric type that is driven by power from an electric motor. 
     As illustrated in  FIG. 3 , the tractor V 1  includes: a full-hydraulic power steering unit  40  that steers the right and left front wheels  11 ; an electro-hydraulically controlled auto brake unit  41  that operates the right and left brakes  30 ; an electronically-controlled PTO valve unit  42  that operates the PTO clutch  27 ; an electro-hydraulically controlled lifting drive unit  43  that lifts/lowers the sowing device  3 ; an electro-hydraulically controlled rolling unit  44  that rolls the sowing device  3  in a roll direction; a vehicle state detector  45  that includes various sensors, switches, and the like provided to the tractor V 1 ; a vehicle-mounted control unit  46  that has various control sections; and the like. 
     The power steering unit  40  may be of an electric type having a steering electric motor. 
     The vehicle state detector  45  is a collective term for the various sensors, the switches, and the like that are provided in the sections of the tractor V 1 . Although not illustrated, the vehicle state detector  45  includes various sensors such as: an accelerator sensor that detects operation amounts of the accelerator lever and the accelerator pedal from idling positions; a speed sensor that detects the engine speed; a gear shift sensor that detects an operation amount of the primary gear shift lever; a vehicle speed sensor that detects the vehicle speed of the tractor V 1 ; a reverser sensor that detects an operation position of the reverser lever; a steering angle sensor that detects a steering angle of the front wheel  11 ; a height sensor that detects a height position of the sowing device  3 ; an inclination sensor that detects a roll angle of the tractor V 1 ; and plural remaining amount sensors  45 A, each of which detects that a remaining amount of the seeds stored in respective one of the storage sections  3 Ba in the sowing device  3  has dropped to a seed replenishment setting value (see  FIG. 3 ). The vehicle state detector  45  includes various switches such as the PTO switch to command engagement/disengagement of the PTO clutch  27  and a lift switch to command lifting/lowering of the sowing device  3 . 
     As illustrated in  FIGS. 3 to 4 , the vehicle-mounted control unit  46  includes: an engine control section  46 A that executes control related to the engine  13 ; a transmission unit control section  46 B that executes control related to the vehicle speed and the forward-reverse switching of the tractor V 1 ; a steering control section  46 C that executes control related to steering; a work device control section  46 D that executes control related to the work device such as the sowing device  3 ; a display control section  46 E that executes control related to the display and notification on the liquid crystal monitor  37  and the like; an automatic travel control section  46 F that executes control related to automatic travel; a non-volatile vehicle-mounted storage section  46 G that stores an automatic travel target path P (see  FIG. 5 ) generated according to a travel area in a field, and the like; and the like. Each of the control sections  46 A to  46 F is constructed of an electronic control unit, in which a microcontroller and the like are integrated, various control programs, and the like. The control sections  46 A to  46 F are connected in a mutually communicable manner via a Controller Area Network (CAN). 
     For example, in-vehicle Ethernet, CAN with Flexible Data rate (CAN-FD), or the like that is a communication standard other than the CAN or a next-generation communication standard may be adopted for the mutual communication among the control sections  46 A to  46 F. 
     When the accelerator lever is operated, the engine control section  46 A executes engine speed maintenance control on the basis of detection information from the accelerator sensor and detection information from the rotation sensor so as to maintain the engine speed at a speed that corresponds to the operation amount of the accelerator lever from the idling position. In the case where the accelerator pedal is operated and the operation amount of the accelerator pedal from the idling position exceeds the operation amount of the accelerator lever from the idling position, the engine control section  46 A performs, based on the detection information from the accelerator sensor and the detection information from the rotation sensor, the engine control section  46 A executes engine speed change control on the basis of the detection information from the accelerator sensor and the detection information from the rotation sensor so as to change the engine speed to a speed that corresponds to the operation amount of the accelerator pedal from the idling position. 
     When the gear shift lever is operated, the transmission unit control section  46 B executes vehicle speed control to change the vehicle speed of the tractor V 1  to a speed corresponding to an operation position of the gear shift lever by controlling actuation of the primary transmission  20  on the basis of detection information from the gear shift sensor and detection information from the vehicle speed sensor. The vehicle speed control includes deceleration stop processing for decelerating the primary transmission  20  to a zero-speed state so as to stop the travel of the tractor V 1  in the case where the gear shift lever is operated to a zero-speed position. 
     When the reverser lever is operated, the transmission unit control section  46 B executes a forward-reverse switching control to switch a transmission state of the forward-reverse switching device  21  on the basis of detection information from the reverser sensor. The forward-reverse switching control includes: cutoff state switching processing for switching the forward-reverse switching device  21  to the transmission cutoff state when the reverser lever is operated to a neutral position; forward travel state switching processing for switching the forward-reverse switching device  21  to a forward transmission state when the reverser lever is operated to a forward position; and reverse travel state switching processing for switching the forward-reverse switching device  21  to a reverse transmission state when the reverser lever is operated to a reverse position. 
     When the PTO switch is operated to an ON position, the work device control section  46 D controls actuation of the PTO valve unit  42  to switch the PTO clutch  27  from the transmission cutoff state to a transmission state. When the PTO switch is operated to an OFF position, the work device control section  46 D controls the actuation of the PTO valve unit  42  to switch the PTO clutch  27  from the transmission state to the transmission cutoff state. 
     The work device control section  46 D executes lifting control to control actuation of the lifting drive unit  43  on the basis of an operation of a lifting switch, detection information from the height sensor, a work height position and a non-work height position for evacuation that are set in advance, so as to lift/lower the sowing device  3  to the work height position or the non-work height position. The lifting control includes: lifting processing for lifting the sowing device  3  from the work height position to the non-work height position when a lifting command is generated by the operation of the lifting switch; and lowering processing for lowering the sowing device  3  from the non-work height position to the work height position when a lowering command is generated by the operation of the lifting switch. 
     The work device control section  46 D has a turning and lifting control function to determine, on the basis of detection information from the steering angle sensor, the detection information from the height sensor, and the non-work height position, which is set in advance, that the tractor V 1  starts turning when detecting that the steering angle of the front wheel  11  reaches a threshold value from a smaller value than the threshold value, control the actuation of the lifting drive unit  43 , and lift the sowing device  3  from the work height position to the non-work height position. 
     The work device control section  46 D has a reverse lifting control function to control the actuation of the lifting drive unit  43  when detecting the operation of the reverse lever to the reverse position on the basis of the detection information from the reverser sensor, the detection information from the height sensor, and the non-work height position, which is set in advance, and lift the sowing device  3  from the work height position to the non-work height position. 
     The work device control section  46 D has an automatic rolling control function to control actuation of the rolling unit  44  and maintain a rolling posture of the sowing device  3  at a control target posture, which is set in advance, on the basis of detection information from the inclination sensor and the control target posture. 
     As illustrated in  FIG. 3 , the tractor V 1  includes a positioning unit  70  that measures a current position, a current direction, and the like of the tractor V 1 . The positioning unit  70  has: a satellite navigation device  71  that measures the current position and the current direction of the tractor V 1  by using the Global Navigation Satellite System (GNSS) as an example of a Navigation Satellite System (NSS); an inertial measurement unit (IMU)  72  that has a three-axis gyroscope, a three-direction acceleration sensor, and the like to measure a posture, a direction, and the like of the tractor V 1 ; and the like. As positioning methods using the GNSS, Differential GNSS (DGNSS), Real Time Kinematic GNSS (RTK-GNSS), and the like are available. In the present embodiment, the RTK-GNSS, which is suited for measurement of a moving body, is adopted. Accordingly, as illustrated in  FIG. 1 , a reference station  6  that enables positioning by the RTK-GNSS is installed at a known location in the periphery of the field. 
     As illustrated in  FIG. 1  and  FIG. 3 , the tractor V 1  and the reference station  6  respectively include: GNSS antennas  73 ,  60  that receive a radio wave transmitted from a positioning satellite  7  (see  FIG. 1 ); communication modules  74 ,  61  that enable the wireless communication of information including positioning information between the tractor V 1  and the reference station  6 ; and the like. As a result, the satellite navigation device  71  in the positioning unit  70  can measure the current position and the current direction of the tractor V 1  with a high degree of accuracy on the basis of: the positioning information that is acquired when the GNSS antenna  73  on the tractor V 1  side receives the radio wave from the positioning satellite  7 ; and the positioning information that is acquired when the GNSS antenna  60  on the reference station  6  side receives the radio wave from the positioning satellite  7 . In addition, due to provision of the satellite navigation device  71  and the inertial measurement unit  72 , the positioning unit  70  can measure the current position, the current direction, and posture angles (a yaw angle, the roll angle, and a pitch angle) of the tractor V 1  with a high degree of accuracy. 
     In this tractor V 1 , the communication module  74  is included in the positioning unit  70  (see  FIG. 3 ). The tractor V 1  includes a communication module  76  that enables the wireless communication of respective information, including the positioning information, with the mobile communication terminal  5 . The inertial measurement unit  72  in the positioning unit  70 , the GNSS antenna  73 , and the communication module  76  are included in an antenna unit  75  illustrated in  FIG. 1 . The antenna unit  75  is arranged at a center in a right-left direction of an upper portion on a front surface side of the cabin  17 . A positioning target position at the time of measuring the current position and the like of the tractor V 1  is set at an axle center position between the right and left rear wheels  12 , which is calculated from an attachment position of the GNSS antenna  73  in the tractor V 1 . 
     Here, in the case where the wireless LAN such as Wi-Fi is adopted for the wireless communication in this tractor V 1 , the communication module  76  functions as a converter that converts communication information bidirectionally between the wireless LAN and the CAN. 
     As illustrated in  FIG. 3 , the mobile communication terminal  5  includes: a terminal control unit  51  having an electronic control unit, in which a microcontroller and the like are integrated, various control programs, and the like; a communication module  52  that allows the wireless communication of the information including the positioning information with the communication module  76  on the tractor V 1  side; and the like. The terminal control unit  51  includes: a display control section  51 A that executes control related to the display and notification on the display device  50  and the like; a target path generation section  51 B that generates the target path P (see  FIG. 5 ) for the automatic travel; a non-volatile terminal storage section  51 C that stores the target path P generated by the target path generation section  51 B, and the like; and the like. The terminal storage section  51 C stores, as various types of information used to generate the target path P, vehicle body information on a turning radius, a work width, and the like of the tractor V 1 , field information that is acquired from the above-described positioning information, and the like. The field information includes plural area identification points Ap 1  to Ap 4  (see  FIG. 5 ) and an area identification frame F (see  FIG. 5 ) used to identify a travel area of the tractor V 1  corresponding to a shape, size, and the like of the field. The plural area identification points Ap 1  to Ap 4  can be acquired by manually registering, using the GNSS, corner points and the like of the field that are necessary to identify the travel area of the tractor V 1  in the field at the time when the user manually drives the tractor V 1  along an outer circumferential edge of the field within the field as a registration target. The area identification frame F can be acquired when the target path generation section  51 B generates line segments that connect the plural acquired area identification points Ap 1  to Ap 4  in an acquisition order. 
     In the case where the field as the registration target is the deformed field having a curved portion in at least one side of an outer shape thereof, in order to identify the travel area of the tractor V 1  corresponding to the shape and size thereof, it is necessary to register plural area identification points corresponding to a shape of the curved portion in addition to the corner points. 
     When the user performs a touch operation on the display device  50  to select a target path generation mode, the target path generation section  51 B initiates information acquisition processing for acquiring various types of information on generation of the target path P (see  FIG. 5 ). 
     A description will hereinafter be made on the information acquisition processing by the target path generation section  51 B with reference to  FIGS. 6 to 10 . 
     With the selection of the target path generation mode, the target path generation section  51 B checks whether the fields Aa to Ag that have been registered exist in the vicinity of the tractor V 1  on the basis of the current position of the tractor V 1  that is transmitted from the vehicle-mounted control unit  46 . 
     In the case where the fields Aa to Ag that have been registered exist, the target path generation section  51 B switches a display screen of the display device  50  to a registered field display screen  50 A that displays map data including the fields Aa to Ag (see  FIG. 6 ). 
     In the case where none of the fields Aa to Ag that have been registered exists, the target path generation section  51 B switches the display screen of the display device  50  to a new registration confirmation screen (not illustrated) on which it is checked whether to newly register the field. 
     In the case where the target path generation section  51 B confirms that the user performs the touch operation on the new registration confirmation screen to newly register the field, the target path generation section  51 B switches the display screen of the display device  50  to a field registration screen (not illustrated) that displays the map data in the vicinity of the tractor and also displays an operation procedure for registering the field, and the like. Then, when the registration of the field is completed according to the operation procedure on the field registration screen, the target path generation section  51 B switches the display screen of the display device  50  to the registered field display screen  50 A and displays the newly registered field as the registered field that exists in the vicinity of the tractor V 1 . The operating procedure, which is displayed on the field registration screen, includes an operation method for acquiring each shape-identifying point (such as the corner points Ap 1  to Ap 4  illustrated in  FIG. 5 ) of an unregistered field, and the like. 
     In the case where the target path generation section  51 B confirms that the field is not newly registered by the user&#39;s touch operation on the new registration confirmation screen, the target path generation section  51 B terminates the target path generation mode. 
     For example, in the case where the user performs the touch operation on the registered field display screen  50 A illustrated in  FIG. 6  to select, of the fields Aa to Ag displayed on the registered field display screen  50 A, the rectangular field Ad as a work target field, the target path generation section  51 B switches the display screen of the display device  50  to a selected field display screen  50 B that displays the selected field Ad and the like (see  FIG. 7 ). In the selected field display screen  50 B illustrated in  FIG. 7 , along with the selected field Ad, a message  50 Ba that urges selection of a start position S of the automatic travel and the like, a screen switching button  50 Bb that commands switching to a next screen, and the like are displayed. 
     In the case where the start position S of the automatic travel is selected and the screen switching button  50 Bb is operated on the selected field display screen  50 B illustrated in  FIG. 7 , the target path generation section  51 B switches the display screen of the display device  50  to a work device selection screen  50 C that enables selection of the work device (see  FIG. 8 ). In the work device selection screen  50 C illustrated in  FIG. 8 , plural order setting buttons  50 Ca,  50 Cb that enable setting of an order of the work devices displayed on the work device selection screen  50 C, plural work device selection buttons  50 Cc,  50 Cd, each of which enables selection of one of the displayed work devices, a screen switching button  50 Ce that commands switching to the next screen, and the like are displayed. 
     For example, in the case where the sowing device is selected and the screen switching button  50 Ce is operated on the work device selection screen  50 C illustrated in  FIG. 8 , the target path generation section  51 B switches the display screen of the display device  50  to a headland area setting screen  50 D that enables setting of headland areas A 1 , A 2  (see  FIG. 5 ) in the field Ad (see  FIG. 9 ). In the headland area setting screen  50 D illustrated in  FIG. 9 , a first headland area setting button  50 Da for setting a pair of first headland areas A 1  where the tractor V 1  changes a direction with respect to the field Ad and a pair of second headland areas A 2  where the tractor V 1  does not change the direction, a second headland area setting button  50 Db for setting only the pair of first headland areas A 1  for the field Ad, a minimum setting button  50 Dc for setting each of the headland areas A 1 , A 2  to be minimized, a multiple setting button  50 Dd for setting each of the headland areas A 1 , A 2  to be a multiple of the work width, a headland area work button  50 De for including each of the headland areas A 1 , A 2  in a work area Aw (see  FIG. 5 ), a screen switching button  50 Df that commands switching to the next screen, and the like are displayed. In regard to the multiple setting button  50 Dd for setting the headland area to be the multiple of the work width, a one-time setting button for setting the headland area to one time the working width, a two-time setting button for setting the headland area to two times the working width, and the like may be provided. 
     In the case where necessary setting operations are performed and then the screen switching button  50 Df is operated on the headland area setting screen  50 D illustrated in  FIG. 9 , the target path generation section  51 B switches the display screen of the display device  50  to a work condition setting screen  50 E that enables setting of work conditions such as the vehicle speed and the engine speed during work (see  FIG. 10 ). In the work condition setting screen  50 E illustrated in  FIG. 10 , plural work condition display sections  50 Ea to  50 Ed, each of which displays the work condition such as the vehicle speed during the work set by the user, a headland work display section  50 Ee that displays presence or absence of headland work, a screen switching button  50 Ef that commands switching to the next screen, and the like are displayed. 
     In the case where the screen switching button  50 Ce is operated on the work condition setting screen  50 E illustrated in  FIG. 10 , the target path generation section  51 B terminates the information acquisition processing. Then, the target path generation section  51 B executes, for the field Ad that is selected on the registered field display screen  50 A illustrated in  FIG. 6 , target path generation processing for generating the target path P in consideration of various types of the information that are acquired in the information acquisition processing. 
     More specifically, for example, in the case where, for the field Ad illustrated in  FIG. 5 , the first headland area setting button  50 Da and the multiple setting button  50 Dd are operated on the headland area setting screen  50 D illustrated in  FIG. 9 , as illustrated in  FIG. 5 , the target path generation section  51 B secures the pair of first headland areas A 1  and the pair of second headland areas A 2  to be the multiples of the working width in the area identification frame F of the field Ad, and identifies a central area A 3  in the area identification frame F excluding those headland areas A 1 , A 2  as the rectangular work area Aw. Then, in the case where the start position S is selected in a lower left portion of the field Ad on selected field display screen  50 B illustrated in  FIG. 7  and the sowing device  3  is selected on the work device selection screen  50 C illustrated in  FIG. 8 , as illustrated in  FIG. 5 , the target path generation section  51 B generates, for the work area Aw in the field Ad, plural work paths P 1  that are arranged in parallel with predetermined clearances therebetween according to the work width of the sowing device  3 , and generates, for the pair of first headland areas A 1 , plural direction changing paths P 2  that connect the plural work paths P 1  in a travel order of the tractor V 1  from the start position S. 
     In this way, the target path generation section  51 B can set the work area Aw, generate the target path P, and the like for the field Ad illustrated in  FIG. 5  on the basis of the user settings. The generated target path P is then stored in the terminal storage section  51 C together with various setting contents including a seed delivery amount per unit distance by each of the delivery sections  3 Bb in the sowing device  3 . 
     In the target path P illustrated in  FIG. 5 , each of the work paths P 1  is a path on which the tractor V 1  travels automatically while performing the sowing work. Each of the direction changing paths P 2  is a path on which the tractor V 1  travels automatically from an end point of the previous work path P 1  to a start point of the next work path P 1  without performing the sowing work. The start point of each of the work paths P 1  is a work start point p 1  at which the tractor V 1  starts the sowing work, and the end point of each of the work paths P 1  is a work stop point p 2  at which the tractor V 1  stops the sowing work. 
     The target path P illustrated in  FIG. 5  merely constitutes an example. Based on the vehicle body information such as the turning radii and the number of the working strips that vary by models and the like of the tractor V 1  and the sowing device  3 , the field information such as the shape, the size, and the like of the field that vary among the fields Aa to Ag, and the like, the target path generation section  51 B can generate the various target paths P that are suited for those. 
     The target path P is stored in the terminal storage section  51 C in association with the vehicle body information, the field information, and the like, and can be displayed on the display device  50  of the mobile communication terminal  5 . The target path P includes the travel direction and a target vehicle speed of the tractor V 1  in each of the work paths P 1 , the target vehicle speed and the front-wheel steering angle of the tractor V 1  in each of the direction changing paths P 2 , and the like. 
     In response to a transmission request command from the vehicle-mounted control unit  46 , the terminal control unit  51  transmits the field information, the target path P, and the like, which are stored in the terminal storage section  51 C, to the vehicle-mounted control unit  46 . The vehicle-mounted control unit  46  stores the received field information, the received target path P, and the like in the vehicle-mounted storage section  46 G. In regard to the transmission of the target path P, for example, the terminal control unit  51  may transmit all of the target paths P from the terminal storage section  51 C to the vehicle-mounted control unit  46  at once at a stage before the tractor V 1  starts traveling automatically. Alternatively, the terminal control unit  51  may divide the target path P into plural pieces of divided path information per predetermined distance. Then, from the stage before the tractor V 1  starts traveling automatically, every time a travel distance of the tractor V 1  reaches the predetermined distance, the terminal control unit  51  may sequentially transmit the predetermined number of the divided path information, which corresponds to a travel order of the tractor V 1 , from the terminal storage section  51 C to the vehicle-mounted control unit  46 . 
     In a state where the user performs a manual operation to satisfy various automatic travel start conditions and a travel mode of the tractor V 1  is switched to an automatic travel mode, in the case where the user performs the touch operation on the display device  50  of the mobile communication terminal  5  to command a start of the automatic travel, the automatic travel control section  46 F initiates automatic travel control to cause the tractor V 1  to travel automatically along the target path P in a registered work site A while acquiring the current position, the current direction, and the like of the tractor V 1 , which are measured by the positioning unit  70  using the above-described GNSS. 
     During the automatic travel control, for example, in the case where the user operates the display device  50  of the mobile communication terminal  5  to command termination of the automatic travel, or in the case where the user in the driving unit operates a manual operation tool such as the steering wheel  35  or the accelerator pedal, the automatic travel control section  46 F terminates the automatic travel control, and switches the travel mode from the automatic travel mode to a manual travel mode. 
     The automatic travel control by the automatic travel control section  46 F includes engine automatic control processing, vehicle speed automatic control processing, steering automatic control processing, work automatic control processing, and the like. In the engine automatic control processing, an automatic travel control command for the engine  13  is transmitted to the engine control section  46 A. In the vehicle speed automatic control processing, an automatic travel control command for the vehicle speed and forward-reverse switching of the tractor V 1  is transmitted to the transmission unit control section  46 B. In the steering automatic control processing, an automatic travel control command for steering is transmitted to the steering control section  46 C. In the work automatic control processing, an automatic travel control command for the work device such as the sowing device  3  is transmitted to the work device control section  46 D. 
     In the engine automatic control processing, the automatic travel control section  46 F transmits an engine speed change command and the like to the engine control section  46 A. The engine speed change command commands to change the engine speed on the basis of the set speed and the like included in the target path P. The engine control section  46 A executes engine speed automatic change control and the like. In the engine speed automatic change control, the engine speed is automatically changed in response to any of the various control commands for the engine  13  that are transmitted from the automatic travel control section  46 F. 
     In the vehicle speed automatic control processing, the automatic travel control section  46 F transmits a gear shift operation command, a forward-reverse switching command, and the like to the transmission unit control section  46 B. The gear shift operation command commands the gear shift operation of the primary transmission  20  on the basis of the target vehicle speed included in the target path P. The forward-reverse switching command commands the forward-reverse switching operation of the forward-reverse switching device  21  on the basis of an advancing direction of the tractor V 1  and the like included in the target path P. In response to the various control commands for the primary transmission  20 , the forward-reverse switching device  21 , and the like that are transmitted from the automatic travel control section  46 F, the transmission unit control section  46 B executes: automatic vehicle speed control to automatically control the actuation of the primary transmission  20 ; automatic forward-reverse switching control to automatically control actuation of the forward-reverse switching device  21 ; and the like. The automatic vehicle speed control includes automatic deceleration stop processing and the like. In the automatic deceleration stop processing, for example, in the case where the target vehicle speed included in the target path P is zero, deceleration control is executed to bring the primary transmission  20  into the zero-speed state, so as to stop the travel of the tractor V 1 . 
     In the steering automatic control processing, the automatic travel control section  46 F transmits a steering command and the like to the steering control section  46 C. The steering command commands steering of the right and left front wheels  11  on the basis of the front wheel steering angle included in the target path P, and the like. In response to the steering command that is transmitted from the automatic travel control section  46 F, the steering control section  46 C executes: automatic steering control to control actuation of the power steering unit  40  and steer the right and left front wheels  11 ; automatic brake turning control to control actuation of the auto brake unit  41  and actuate the brake  30  on an inner side of a turn when the steering angle of the front wheels  11  reaches the threshold value; and the like. 
     In the work automatic control processing, the automatic travel control section  46 F transmits a work start command, a work stop command, and the like to the work device control section  46 D. The work start command commands switching of the sowing device  3  to a work state on the basis of the work start point p 1  included in the target path P. The work stop command commands switching of the sowing device  3  to a non-work state on the basis of the work stop point p 2  included in the target path P. In response to the various control commands for the sowing device  3  that are transmitted from the automatic travel control section  46 F, the work device control section  46 D executes: automatic work start control to control the actuation of the lifting drive unit  43 , lower the sowing device  3  to the work height position, and actuate the sowing device  3 ; automatic work stop control to lift the sowing device  3  to the non-work height position and stop the sowing device  3 ; and the like. 
     In the case where the work device  3  is the sowing device, the mower, or the like that is driven by the power from the PTO shaft  29 , in the automatic work start control that is based on the work start command from the automatic travel control section  46 F, the work device control section  46 D controls the actuation of the PTO valve unit  42  and the lifting drive unit  43  to lower the work device  3  to the work height position and actuate the work device  3 . Meanwhile, in the automatic work stop control that is based on the work stop command from the automatic travel control section  46 F, the work device control section  46 D controls the actuation of the PTO valve unit  42  and the lifting drive unit  43  to stop the work device  3  and lift the work device  3  to the non-work height position. 
     That is, the above-described automatic travel unit  4  includes the power steering unit  40 , the auto brake unit  41 , the PTO valve unit  42 , the lifting drive unit  43 , the rolling unit  44 , the vehicle state detector  45 , the vehicle-mounted control unit  46 , the positioning unit  70 , the communication modules  74 ,  76 , and the like. When these components are actuated appropriately, the tractor V 1  can travel automatically along the target path P with the high degree of accuracy, and tillage work by the sowing device  3  can be performed appropriately. 
     As illustrated in  FIGS. 3 to 4 , the tractor V 1  includes an obstacle detection system  80  that monitors surroundings of the tractor V 1  and detects an obstacle present in the surroundings. The obstacles detected by the obstacle detection system  80  are a person such as a worker and another work vehicle working in any of the fields Aa to Ag, and an existing utility pole, tree, and the like in any of the fields Aa to Ag. 
     As illustrated in  FIG. 1  and  FIG. 4 , the obstacle detection system  80  has: four cameras  81  to  84 , each of which captures an image of the surroundings of the tractor V 1 ; an active sensor unit  85  that measures a distance to a measurement target object present in the surroundings of the tractor V 1 ; an image processor  86  that processes the image from each of the cameras  81  to  84 ; and an obstacle detector  87  that performs integrated processing of information from the image processor  86  and measurement information from the active sensor unit  85  to detect the obstacle. Each of the image processor  86  and the obstacle detector  87  is constructed of an electronic control unit, in which a microcontroller and the like are integrated, various control programs, and the like. The active sensor unit  85 , the image processor  86 , and the obstacle detector  87  are connected to the vehicle-mounted control unit  46  in a mutually communicable manner via the CAN. 
     The obstacle detection system  80  has, as the four cameras  81  to  84 : a front camera  81 , for which a predetermined range in front of the cabin  17  is set as an imaging range; a rear camera  82 , for which a predetermined range behind the cabin  17  is set as the imaging range; a right camera  83 , for which a predetermined range to the right of the cabin  17  is set as the imaging range; and a left camera  84 , for which a predetermined range to the left of the cabin  17  is set as the imaging range. 
     The front camera  81  and the rear camera  82  are arranged on a right-left center line of the tractor V 1 . The front camera  81  is arranged at the center in the right-left direction of the upper portion on a front end side of the cabin  17  and has a front-down posture to look down the front of the tractor V 1  from a diagonally upper side. In this way, a predetermined range on a front side of a vehicle body with the right-left center line of the tractor V 1  being a symmetrical axis is set as the imaging range of the front camera  81 . The rear camera  82  is arranged at the center in the right-left direction of the upper portion on a rear end side of the cabin  17  and has a rear-down posture to look down the rear of the tractor V 1  from the diagonally upper side. In this way, a predetermined range on a rear side of the vehicle body with the right-left center line of the tractor V 1  being a symmetrical axis is set as the imaging range of the rear camera  82 . The right camera  83  is arranged at a center in a front-rear direction of the upper portion on a right end side of the cabin  17  and has a right-down posture to look down the right of the tractor V 1  from the diagonally upper side. In this way, a predetermined range on a right side of the vehicle body is set as the imaging range of the right camera  83 . The left camera  84  is arranged at the center in the front-rear direction of the upper portion on a left end side of the cabin  17  and has a left-down posture to look down the left of the tractor V 1  from the diagonally upper side. In this way, a predetermined range on a left side of the vehicle body is set as the imaging range of the left camera  84 . 
     The active sensor unit  85  has: a front lidar sensor  85 A, for which predetermined range in front of the cabin  17  is set as a measurement range; a rear lidar sensor  85 B, for which a predetermined range behind the cabin  17  is set as the measurement range; and a sonar  85 C, for which a predetermined range to the right of the cabin  17  and a predetermined range to the left of the cabin  17  are set as the measurement ranges. The lidar sensors  85 A,  85 B respectively have: measurement sections  85 Aa,  85 Ba that use a laser beam (for example, a pulsed near-infrared laser beam) as an example of measurement light to perform measurement in the measurement ranges; lidar control sections  85 Ab,  85 Bb that generate distance images and the like on the basis of the measurement information from the measurement sections  85 Aa,  85 Ba. The sonar  85 C has a right ultrasonic sensor  85 Ca, a left ultrasonic sensor  85 Cb, and a single sonar control section  85 Cc. Each of the lidar control sections  85 Ab,  85 Bb and the sonar control section  85 Cc is constructed by an electronic control unit in which a microcontroller or the like is integrated, various control programs, and the like. The lidar control sections  85 Ab,  85 Bb and the sonar control section  85 Cc are connected to the obstacle detector  87  in the mutually communicable manner via the CAN. 
     In the lidar sensors  85 A,  85 B, the measurement sections  85 Aa,  85 Ba each measure a distance from respective one of the measurement sections  85 Aa,  85 Ba to each ranging point (an example of the measurement target object) by a Time Of Flight (TOF) method for measuring the distance to the ranging point on the basis of a round-trip time from arrival of the irradiated laser beam at the ranging point to return thereof. Each of the measurement sections  85 Aa,  85 Ba scans the laser beam vertically and horizontally at a high speed over respective one of the measurement ranges, sequentially measures the distance to the ranging point per scan angle (coordinate), and thereby performs three-dimensional measurement in respective one of the measurement ranges. Each of the measurement sections  85 Aa,  85 Ba sequentially measures intensity of reflected light (hereinafter referred to as reflection intensity) from each of the ranging points that are acquired when scanning the laser beam vertically and horizontally at the high speed over respective one of the measurement ranges. Each of the measurement sections  85 Aa,  85 Ba repeatedly measures the distance to each of the ranging points, the reflection intensity, and the like in real time in respective one of the measurement ranges. Each of the lidar control sections  85 Ab,  85 Bb generates the distance image and extracts a ranging point group estimated as the obstacle from the measurement information, such as the distance to each of the ranging points and the scan angle (coordinate) for each of ranging points, measured by respective one of the measurement sections  85 Aa,  85 Ba. Then, each of the lidar control sections  85 Ab,  85 Bb transmits, as measurement information on an obstacle candidate, the measurement information on the extracted ranging point group to the obstacle detector  87 . 
     Similar to the front camera  81  and the rear camera  82 , the front lidar sensor  85 A and the rear lidar sensor  85 B are arranged on the right-left center line of the tractor V 1 . The front lidar sensor  85 A is arranged at the center in the right-left direction of the upper portion on the front end side of the cabin  17  and has the front-down posture to look down the front of the tractor V 1  from the diagonally upper side. In this way, the front lidar sensor  85 A sets a predetermined range on the front side of the vehicle body with the right-left center line of the tractor V 1  being the symmetrical axis as the measurement range of the measurement section  85 Aa. The rear lidar sensor  85 B is arranged at the center in the right-left direction of the upper portion on the rear end side of the cabin  17  and has the rear-down posture to look down the rear of the tractor V 1  from the diagonally upper side. In this way, the rear lidar sensor  85 B sets a predetermined range on the rear side of the vehicle body with the right-left center line of the tractor V 1  being the symmetrical axis as the measurement range of the measurement section  85 Ba. 
     In the sonar  85 C, the sonar control section  85 Cc determines presence or absence of the measurement target object in the measurement range on the basis of transmission and reception of the ultrasonic waves by the right and left ultrasonic sensors  85 Ca,  85 Cb. The sonar control section  85 Cc measures a distance from each of the right and left ultrasonic sensors  85 Ca,  85 Cb to the measurement target object by the Time Of Flight (TOF) method for measuring the distance to the ranging point on the basis of the round-trip time from arrival of the transmitted ultrasonic wave at the ranging point to return thereof, and transmits, to the obstacle detector  87 , the distance to the measurement target object that has been measured and a direction of the measurement target object as the measurement information on the obstacle candidate. 
     The right ultrasonic sensor  85 Ca is attached to a getting-on/off step (not illustrated) on a right side that is arranged between the right front wheel  11  and the right rear wheel  12  in the cabin  17  and has a posture facing a right outer side of the vehicle body. In this way, a predetermined range on the right outer side of the vehicle body is set as the measurement range of the right ultrasonic sensor  85 Ca. The left ultrasonic sensor  85 Cb is attached to the getting-on/off step  17 A on a left side that is arranged between the left front wheel  11  and the left rear wheel  12  in the cabin  17  and has a posture facing a left outer side of the vehicle body. In this way, a predetermined range on the left outer side of the vehicle body is set as the measurement range of the left ultrasonic sensor  85 Cb. 
     The image processor  86  performs image processing on the images that are sequentially transmitted from the cameras  81  to  84 . The image processor  86  is subjected to learning processing for recognizing, as the obstacles, the person such as the worker and the other work vehicle working in the registered field, and the existing utility pole, tree, and the like in the registered field. 
     The image processor  86  synthesizes the images that are sequentially transmitted from the cameras  81  to  84  to generate an all-around image (for example, a surround view) of the tractor V 1 . Then, the image processor  86  transmits the generated all-around image and the images from the cameras  81  to  84  to the display control section  46 E on the tractor side and the display control section  51 A on the mobile communication terminal side. 
     In this way, the all-around image generated by an all-around image generation section  86 A, the image in the travel direction of the tractor V 1 , and the like can be displayed on the liquid crystal monitor  37  of the tractor V 1 , the display device  50  of the mobile communication terminal  5 , and the like. Then, by such display, the user can visually recognize a situation in the surroundings of the tractor V 1  and a situation in the travel direction. 
     Based on the images that are sequentially transmitted from the cameras  81  to  84 , the image processor  86  determines whether the obstacle that interferes with the travel of the tractor V 1  exists in any of the imaging ranges of the cameras  81  to  84 . In the case where the obstacle exists, coordinate calculation processing is performed to calculate the coordinates of the obstacle on the image where the obstacle exists, and convert the calculated coordinates of the obstacle into coordinates with a vehicle body coordinate origin being a reference on the basis of mounted positions, mounted angles, and the like of the cameras  81  to  84 . Then, a linear distance between the converted coordinates and a preset distance calculation reference point is calculated as a distance from the distance calculation reference point to the obstacle. Then, as detection information on the obstacle, the calculated distance from the converted coordinates to the calculated obstacle is transmitted to the obstacle detector  87 . On the other hand, in the case where the obstacle does not exist, a fact that the obstacle is not detected is transmitted to the obstacle detector  87 . 
     Just as described, in the case where the obstacle exists in any of the imaging ranges of the cameras  81  to  84 , the image processor  86  transmits the detection information on the obstacle to the obstacle detector  87 . Accordingly, when receiving the detection information on the obstacle, the obstacle detector  87  can detect that the obstacle exists in any of the imaging ranges of the cameras  81  to  84 , and can detect a position of the obstacle and the distance to the obstacle. On the other hand, in the case where the obstacle does not exist in any of the imaging ranges of the cameras  81  to  84 , the image processor  86  transmits non-detection of the obstacle to the obstacle detector  87 . Thus, the obstacle detector  87  can detect that the obstacle does not exist in any of the imaging ranges of the cameras  81  to  84 . 
     In the case where the detection information on the obstacle the image processor  86  with a high degree of object determination accuracy matches the measurement information on the obstacle candidate from the active sensor unit  85  with a high degree of ranging accuracy, the obstacle detector  87  adopts a distance to the obstacle candidate that is acquired from the active sensor unit  85  as the distance to the obstacle. In this way, the obstacle detector  87  can acquire the detection information on the obstacle with the high degrees of the object determination accuracy and the ranging accuracy. The obstacle detector  87  transmits the acquired detection information on the obstacle to the vehicle-mounted control unit  46 . 
     As illustrated in  FIGS. 3 to 4 , the vehicle-mounted control unit  46  includes a collision avoidance control section  4611  to avoid a collision with the obstacle on the basis of the detection information from the obstacle detector  87 . The collision avoidance control section  4611  is constructed of an electronic control unit, in which a microcontroller and the like are integrated, various control programs, and the like. The collision avoidance control section  4611  is connected to the other control sections  46 A to  46 F of the vehicle-mounted control unit  46 , the active sensor unit  85 , the image processor  86 , and the obstacle detector  87  in the mutually communicable manner via the CAN. 
     The collision avoidance control section  4611  is configured to appropriately perform collision avoidance processing for the obstacle. The collision avoidance processing includes: notification processing for acquiring the distance to the obstacle and the like on the basis of the detection information from the obstacle detector  87  and actuating a notification device such as a notification buzzer or a notification lamp provided in the tractor V 1  and the mobile communication terminal  5  according to the acquired distance to the obstacle and the like; automatic deceleration processing for reducing the vehicle speed of the tractor V 1 ; automatic travel stop processing for stopping the travel of the tractor V 1 ; and the like. 
     As illustrated in  FIGS. 3 to 4 , the vehicle-mounted control unit  46  includes a standby position setting section  46 K that sets a standby position (hereinafter referred to as a replenishment standby position) p 0  (see  FIG. 5 ) of the tractor V 1  at the time of replenishing the seeds to the sowing device  3  of the tractor V 1 . The standby position setting section  46 K is constructed of an electronic control unit, in which a microcontroller and the like are integrated, various control programs, and the like. The standby position setting section  46 K is connected to the other control sections  46 A to  46 F,  4611  of the vehicle-mounted control unit  46  and the like in the mutually communicable manner via the CAN. 
     The standby position setting section  46 K executes standby position acquisition control when detecting the manual travel of the tractor V 1  to any of the fields Aa to Ag as the work targets on the basis of position information of the tractor V 1  that is measured by the positioning unit  70  using the above-described GNSS, the information on each of the fields Aa to Ag (see  FIGS. 5 to 6 ) that exist in the vicinity of the tractor V 1 , and the like. 
     A description will hereinafter be made on the standby position acquisition control by the standby position setting section  46 K for the sowing work in the field Ad illustrated in  FIG. 5  with reference to a flowchart in  FIG. 11 . 
     The standby position setting section  46 K initiates path acquisition processing for acquiring a manual travel path Rm of the tractor V 1  from the position information of the tractor V 1  measured by the positioning unit  70  in conjunction with the detection of the manual travel of the tractor V 1  to the field Ad (step # 1 ). 
     The standby position setting section  46 K performs first determination processing for determining whether the tractor V 1  has entered the field Ad from outside the field Ad on the basis of the currently-acquired manual travel path Rm and an outline OL of the field Ad that is included in information on the field Ad (step # 2 ). More specifically, the standby position setting section  46 K determines whether the currently-acquired manual travel path Rm has intersected the outline OL of the field Ad. 
     In the first determination processing, the standby position setting section  46 K continues the path acquisition processing until the tractor V 1  enters the field. Then, when the tractor V 1  enters the field Ad, the standby position setting section  46 K performs entry point acquisition processing for acquiring an entry point at the time when the tractor V 1  has entered the field Ad from outside the field A (step # 3 ), and performs standby position setting processing for setting the acquired entry point to the replenishment standby position p 0  (step # 4 ). More specifically, in the case where the currently-acquired manual travel path Rm intersects the outline OL of the field Ad, the standby position setting section  46 K determines that the tractor V 1  has entered the field Ad, sets an intersection point of the manual travel path Rm with the outline OL of the field Ad as the entry point of the tractor V 1  into the field Ad, sets this entry point to the replenishment standby position p 0 , and stores the replenishment standby position p 0  in the vehicle-mounted storage section  46 G. 
     After performing the standby position setting processing, the standby position setting section  46 K performs second determination processing for determining whether the tractor V 1  has reached the start position S of the automatic travel (step # 5 ). 
     In second determination processing, the standby position setting section  46 K continues the path acquisition processing until the tractor V 1  reaches the start position S of the automatic travel. Then, when the tractor V 1  reaches the start position S of the automatic travel, the standby position setting section  46 K stores the manual travel path Rm to the start position S in the vehicle-mounted storage section  46 G, terminates the path acquisition processing (Step # 6 ), and thereafter terminates the standby position acquisition control. 
     The automatic travel control section  46 F determines whether a standby condition for causing the tractor V 1  to stand by at the replenishment standby position p 0  is satisfied in an automatic travel state where the automatic travel control is executed to cause the tractor V 1  to travel automatically along the target path P. Then, in the case where the standby condition is satisfied, the automatic travel control section  46 F executes seed replenishment movement control to cause the tractor V 1  to travel automatically from the current position to the replenishment standby position p 0  and to stand by at the replenishment standby position p 0 . 
     More specifically, since the tractor V 1  is configured to have the sowing specification in this first embodiment, the automatic travel control section  46 F is set to determine that the standby condition is satisfied in the case where the remaining amount sensors  45 A (see  FIG. 3 ) provided in the storage sections  3 Ba of the sowing device  3  detect that the remaining amount of the seeds in any of the storage sections  3 Ba has dropped to the seed replenishment setting value. 
     That is, in the automatic travel state of the tractor V 1  by the automatic travel control, the automatic travel control section  46 F determines whether the remaining amount of the seeds in any of the storage sections  3 Ba in the sowing device  3  has dropped to the seed replenishment setting value on the basis of the detection information from each of the remaining amount sensors  45 A. Then, in the case where the remaining amount of the seeds in any of the storage sections  3 Ba has dropped to the seed replenishment setting value, the automatic travel control section  46 F executes the seed replenishment movement control. 
     Here, the seed replenishment setting value in this first embodiment is set to a larger value than an amount of the seeds that is consumed when the tractor V 1  travels automatically on the single work path P 1  of the target path P. 
     A description will hereinafter be made on the seed replenishment movement control by the automatic travel control section  46 F for the sowing work in the field Ad illustrated in  FIG. 5  with reference to a flowchart in  FIG. 12 . 
     In conjunction with the initiation of the seed replenishment movement control, the automatic travel control section  46 F performs remaining amount dropping notification processing for notifying the user that the remaining amount of the seeds in the storage section  3 Ba has dropped to the seed replenishment setting value by the display device  50  of the mobile communication terminal  5 , or the like (step # 11 ). 
     The automatic travel control section  46 F performs interruption position setting processing and resumption position setting processing on the basis of the target path P and the current position of the tractor V 1  (steps # 12  to  13 ). In the interruption position setting processing, a work stop point (end point) p 2  on the work path P 1  where the tractor V 1  currently travels is set as a seed replenishment interruption position p 3 . In the resumption position setting processing, a next work start point (start point of the next work path P 1 ) p 1  from the interruption position p 3  is set as a resumption position p 4  after the seed replenishment. 
     After setting the above positions, the automatic travel control section  46 F performs replenishment path generation processing and resumption path generation processing (steps # 14  to  15 ). In the replenishment path generation processing, the shortest replenishment movement path Pm 1  from the seed replenishment interruption position p 3  to the replenishment standby position p 0  is generated by using untraveled paths (paths indicated by thin lines of the target path P illustrated in  FIG. 5 ) of the target path P and the manual travel path Rm stored in the vehicle-mounted storage section  46 G. In the resumption path generation processing, the shortest resumption movement path Pm 2  from the replenishment standby position p 0  to the resumption position p 4  after the seed replenishment is generated by using the manual travel path Rm. 
     Although not illustrated, the resumption movement path Pm 2  includes, in a path start end portion thereof, a direction changing path to change the direction of the tractor V 1  from a reverse posture to a forward posture. 
     The automatic travel control section  46 F performs third determination processing for determining whether the tractor V 1  has reached the interruption position p 3  (step # 16 ). In the third determination processing, the automatic travel control section  46 F continues the sowing work by the automatic travel control until the tractor V 1  reaches the interruption position p 3 . Then, in the case where the tractor V 1  reaches the interruption position p 3 , the automatic travel control section  46 F performs automatic travel control interruption processing for interrupting the automatic travel control (step # 17 ). 
     After the interruption of the automatic travel control, the automatic travel control section  46 F initiates replenishment movement processing and replenishment movement notification processing (steps # 18  to  19 ). In the replenishment movement processing, the tractor V 1  travels automatically from the interruption position p 3  to the replenishment standby position p 0  along the replenishment movement path Pmt. In the replenishment movement notification processing, the user is notified that the tractor V 1  currently travels to the replenishment standby position p 0  by the display device  50  of the mobile communication terminal  5 , or the like. 
     The automatic travel control section  46 F performs fourth determination processing for determining whether the tractor V 1  has reached the replenishment standby position p 0  (step # 20 ). In the fourth determination processing, the automatic travel control section  46 F continues the replenishment movement processing and the replenishment movement notification processing until the tractor V 1  reaches the replenishment standby position p 0 . Then, when the tractor V 1  reaches the replenishment standby position p 0 , the automatic travel control section  46 F terminates the replenishment movement processing and the replenishment movement notification processing and causes the tractor V 1  to stand by at the replenishment standby position p 0  (step # 21  to  22 ). 
     The automatic travel control section  46 F performs fifth determination processing for determining whether the user has performed the touch operation on the display device  50  of the mobile communication terminal  5  to command the resumption of the automatic travel of the tractor V 1  by the automatic travel control while the tractor V 1  stands by at the replenishment standby position p 0  (step # 23 ). 
     In the fifth determination processing, until the resumption of the automatic travel is commanded, the automatic travel control section  46 F determines that the replenishment of the seeds to each of the storage sections  3 Ba is not completed, and causes the tractor V 1  to stand by at the replenishment standby position p 0 . Then, in the case where the resumption of the automatic travel is commanded, the automatic travel control section  46 F determines that the replenishment of the seeds to each of the storage sections  3 Ba is completed, and initiates: resumption movement processing for causing the tractor V 1  to travel automatically from the replenishment standby position p 0  to the resumption position p 4  along the resumption movement path Pm 2 ; and resumption movement notification processing for notifying the user that the tractor V 1  currently travels to the resumption position p 4  by the display device  50  of the mobile communication terminal  5 , or the like (steps # 24  to  25 ). 
     The automatic travel control section  46 F performs sixth determination processing for determining whether the tractor V 1  has reached the resumption position p 4  (step # 26 ). In the sixth determination processing, the automatic travel control section  46 F continues the resumption movement processing and the resumption movement notification processing until the tractor V 1  reaches the resumption position p 4 . Then, when the tractor V 1  reaches the resumption position p 4 , the automatic travel control section  46 F terminates the resumption movement processing and the resumption movement notification processing (step # 27  to  28 ). 
     After terminating the resumption movement processing and the resumption movement notification processing, the automatic travel control section  46 F performs automatic travel control resumption processing for resuming the automatic travel of the tractor V 1  by the automatic travel control (step # 29 ), and thereafter terminates the seed replenishment movement control. 
     With the configuration that has been described so far, in this automatic travel system for a work vehicle, when detecting the manual travel of the tractor V 1  to any of the fields Aa to Ag as the work target, the standby position setting section  46 K executes the standby position acquisition control to acquire the entry point of the tractor V 1  to respective one of the fields Aa to Ag as the work target, and sets this entry point as the replenishment standby position p 0 . In this way, the user no longer has to set the replenishment standby position p 0  for each of the fields Aa to Ag. 
     The entry point that is set at the replenishment standby position p 0  is an entrance/exit of each of the fields Aa to Ag, by which each of the fields Aa to Ag is connected to a farm road Rf or the like where a carrier vehicle that is loaded with the replenishment seeds, and the like can be stopped. Accordingly, in the case where the seeds are replenished to the sowing device  3  of the tractor V 1  that stands by at the replenishment standby position p 0 , the carrier vehicle or the like loaded with the seeds can be easily brought close to the tractor V 1  at the replenishment standby position p 0 . In this way, it is possible to reduce labor required to replenish the seeds from the carrier vehicle or the like to the sowing device  3  of the tractor V 1 . 
     In addition, in this automatic travel system for a work vehicle, in the case where the remaining amount of the seeds in the sowing device  3  drops to the seed replenishment setting value, the automatic travel control section  46 F executes the seed replenishment movement control to move the tractor V 1  to the replenishment standby position p 0  and then to stand by at the replenishment standby position p 0 . In this way, the user no longer has to cause the tractor V 1  to travel manually from the interruption position p 3  to the replenishment standby position p 0 . 
     Furthermore, in this automatic travel system for a work vehicle, in the case where the replenishment of the seeds to the sowing device  3  is completed and the user performs the touch operation on the display device  50  of the mobile communication terminal  5  to command the resumption of the automatic travel control while the tractor V 1  stands by at the replenishment standby position p 0 , the automatic travel control section  46 F moves the tractor V 1  from the replenishment standby position p 0  to the resumption position p 4 , and thereafter resumes the automatic travel of the tractor V 1  along the target path P by the automatic travel control. In this way, the user no longer has to cause the tractor V 1  to travel manually from the replenishment standby position p 0  to the resumption position p 4 . 
     In other words, the setting of the replenishment standby position p 0  in each of the fields Aa to Ag and the movement of the tractor V 1  to the replenishment standby position p 0  can be performed automatically and appropriately. Thus, the replenishment work for the sowing device  3  of the tractor V 1  can be performed efficiently while a burden on the user is reduced. 
     Moreover, in this automatic travel system for a work vehicle, the interruption position p 3  of the sowing work is set at the work stop point p 2  of the currently traveled work path P 1 . Thus, even in the case where the remaining amount of the seeds in the sowing device  3  drops to the seed replenishment setting value in the middle of the work path P 1 , the tractor V 1  can continue the sowing work to the work stop point p 2  of the currently traveled work path P 1  under the automatic travel control. In addition, the resumption position p 4  after the seed replenishment is set at the next work start point (start point of the next work path P 1 ) p 1  from the interruption position p 3 . Thus, for example, compared to a case where the resumption position p 4  after the seed replenishment (the interruption position p 3  of the sowing work) is set at a position in the middle of the currently traveled work path P 1 , in the resumption movement processing for causing the tractor V 1  to travel automatically to the resumption position p 4 , the tractor V 1  no longer has to travel forward to a position near the resumption position p 4 , thereafter be switched to the reverse travel state, and travel reversely to the resumption position p 4 . As a result, the tractor V 1  can travel automatically and efficiently to the resumption position p 4 . 
     In this automatic travel system for a work vehicle, in both of the replenishment movement processing and the resumption movement processing, the tractor V 1  travels along the untraveled path of the target path P and the manual travel path Rm. Thus, it is possible to avoid a possibility that the tractor V 1  tramples a worked area Awa of each of the fields Aa to Ag and a possibility of forming ruts, which adversely affect the sowing work, in an unworked area Awb of each of the fields Aa to Ag. 
     Although not illustrated, the automatic travel control section  46 F includes a side-by-side travel control module that enables side-by-side work (see  FIG. 13 ) in which the plural tractors V 1  travel side-by-side along the target path P. In the case where the user performs the touch operation on the display device  50  of the mobile communication terminal  5  to command initiation of the side-by-side work in a state where various manual setting operations are performed to enable the side-by-side work, the side-by-side travel control module execute automatic side-by-side travel control to cause the plural tractors V 1  to travel side-by-side along the target path P by using the GNSS, the obstacle detection system  80 , the collision avoidance control section  4611 , and the like described above. 
     In the side-by-side work, of the plural tractors V 1 , the standby position setting section  46 K of the tractor V 1  traveling in the lead sets the entry point of the tractor V 1  to any of the fields Aa to Ag, which is acquired in the above-described the entry point acquisition processing, at the replenishment standby position p 0 . The standby position setting section  46 K of each of the following tractors V 1  sets a predetermined position in the field with a predetermined distance from the replenishment standby position p 0  of the leading tractor V 1  to the replenishment standby position p 0  according to a travel order during the side-by-side work. Then, in the case where the remaining amount of the seeds in any of the sowing devices  3  of the tractors V 1  drops to the seed replenishment setting value during the side-by-side travel control, the side-by-side travel control modules of the tractors V 1  execute the above-described seed replenishment movement control and moves the tractors V 1  from the interruption position p 3  of the sowing work to the replenishment standby position p 0  in the travel order during the side-by-side work in a state where a predetermined inter-vehicular distance is provided between two each of the tractors V 1 . Thereafter, the side-by-side travel control modules each cause the tractor V 1  to stand by at the replenishment standby position p 0 . 
     In the case where, during the standby of each of the tractors V 1  at the replenishment standby position p 0 , the replenishment of the seeds to the sowing device  3  of each of the tractors V 1  is completed and the user performs the touch operation on the display device  50  of the mobile communication terminal  5  to command resumption of the side-by-side travel control, the side-by-side travel control module of each of the tractors V 1  moves respective one of the tractors V 1  from the replenishment standby position p 0  to the resumption position p 4 , and thereafter resumes the automatic travel of respective one of the tractors V 1  along the target path P by the side-by-side travel control. 
     In this way, also in the side-by-side work in which the plural (two in  FIG. 13 ) tractors V 1  travel side-by-side along the target path P as illustrated in  FIG. 13 , it is possible to automatically and appropriately set the replenishment standby position p 0  in each of the fields Aa to Ag and move the tractor V 1  to the replenishment standby position p 0 . Thus, it is possible to efficiently perform the replenishment work for the sowing device  3  of the tractor V 1  while reducing the burden on the user. 
     For example, as illustrated in  FIG. 13 , in the case where, in the side-by-side work in which the two tractors V 1  travel side-by-side along the target path P, the preceding tractor V 1  is a manned machine with the user on board in the driving unit thereof and the following tractor V 1  that accompanies this manned machine is an unmanned machine, the side-by-side travel control module and the standby position setting section  46 K in each of the tractors V 1  may perform control actuation as follows. 
     When detecting switching of the travel mode of the manned machine from the automatic travel mode to the manual travel mode during the side-by-side travel control, the side-by-side travel control module of the manned machine interrupts the side-by-side travel control and performs interruption point transmission processing for transmitting the interruption point to the unmanned machine. In addition, the side-by-side travel control module of the manned machine executes: path acquisition control to acquire the manual travel path Rm of the manned machine from the position information of the manned machine measured by the positioning unit  70  of the manned machine; and acquired path transmission control to transmit the acquired manual travel path Rm of the manned machine to the unmanned machine. 
     When receiving the interruption point of the manned machine during the side-by-side travel control, the side-by-side travel control module of the unmanned machine continues the side-by-side travel control to a point corresponding to the interruption point of the manned machine in the currently traveled work path P 1 , and thereafter interrupts the side-by-side travel control. Then, in the case where the side-by-side travel control module of the unmanned machine receives the manual travel path Rm of the manned machine, after the interruption of the side-by-side travel control, the side-by-side travel control module of the unmanned machine executes manual path following control to cause the unmanned machine to follow the manned machine along the manual travel path Rm in a state of being provided with the predetermined inter-vehicular distance from the manned machine. The manual path following control includes the standby position setting processing and standby stop processing. In the standby position setting processing, the standby position setting section  46 K of the unmanned machine acquires the detection information from the obstacle detector  87  of the unmanned machine. Then, when detecting a stop of the manned machine on the basis of the acquired detection information, the standby position setting section  46 K of the unmanned machine sets a position behind the manned vehicle with a predetermined distance from a stop position of the manned machine as a standby position p 0  of the unmanned machine. In the standby stop processing, in the case where the standby position setting section  46 K sets the standby position p 0  of the unmanned machine, the side-by-side travel control module of the unmanned machine automatically stops the unmanned machine at the standby position p 0 . 
     In this way, for example, in the case where the user who is in the manned machine comprehends, via the display device  50  of the mobile communication terminal  5 , or the like, that the remaining amount of the seeds in any of the tractors V 1  has dropped to the seed replenishment setting value, and makes the manual travel to move the manned machine to the desired replenishment standby position p 0  after the manned machine reaches the work stop point p 2  of the currently traveled work path P 1  (the interruption position p 3 ) by the side-by-side travel control, the user who is in the manned machine interrupts the side-by-side travel control and executes the manual path following control after the manned machine reaches the work stop point p 2  of the currently traveled work path P 1  (the interruption position p 3 ). As a result, as indicated by two-dot chain lines in  FIG. 13 , the unmanned machine can follow the manned machine along the manual travel path Rm of the manned machine. Then, when the manned machine reaches the replenishment standby position p 0  and stops at the replenishment standby position p 0 , the unmanned machine can be stopped automatically at the standby position p 0  with the predetermined distance from the stop position of the manned machine. 
     Second Embodiment 
     A description will hereinafter be made on, as an example of the mode for carrying out the present invention, a second embodiment in which the automatic travel system for a work vehicle according to the present invention is applied to the riding rice transplanter as an example of the work vehicle with reference to the drawings. 
     The automatic travel system for a work vehicle exemplified in this second embodiment differs from the automatic travel system for a work vehicle exemplified in the first embodiment in terms of, in addition to the applied work vehicle, the control actuation of the standby position setting section  46 K and the automatic travel control section  46 F, and the like. Thus, a description will be made on a main configuration of the applied work vehicle, the control actuation of the standby position setting section  46 K and the automatic travel control section  46 F, and the like. 
     As illustrated in  FIGS. 14 to 15 , a riding rice transplanter V 2  exemplified in this second embodiment has: a travel body  1  that corresponds to the tractor V 1  exemplified in the first embodiment; and a work device for planting seedlings (hereinafter referred to as a seedling planting device)  3  that is coupled to a rear portion of the travel body  1  via a link mechanism (not illustrated). For this reason, this riding rice transplanter V 2  can plant the seedlings in the field Ad as the work target by using the seedling planting device  3 , which is provided in the rear portion thereof. The seedling planting device  3  is coupled to the rear portion of the travel body  1  in a liftable and rollable manner. Here,  FIGS. 14 to 15  each exemplify a case where the field Ad of the fields Aa to Ag is selected as the work target. Instead of the seedling planting device  3 , the work device such as the fertilizer application device or the chemical spraying device can be provided to the riding rice transplanter V 2 . 
     As illustrated in  FIGS. 14 to 15 , the seedling planting device  3  includes a seedling loading table  3 C onto which a seedling mat as an example of the agricultural material is loaded. Although not illustrated, the seedling planting device  3  includes plural ground leveling floats, a power distribution unit, a lateral feed mechanism, vertical feed mechanisms and planting mechanisms for the number of working strips, a planting frame for supporting those, and the like. 
     The seedling loading table  3 C is formed to load the seedling mats for the number of the working strips. The seedling loading table  3 C is supported by the planting frame in a slidable manner in the right-left direction. Each of the ground leveling floats levels a mud surface of the field in conjunction with travel of a machine body during the working travel. The power distribution unit distributes the power from the engine, which is transmitted via the work transmission system, to the lateral feed mechanism and each of the planting mechanisms. The lateral feed mechanism is driven by the power from the power distribution unit and, with this driving, causes the seedling loading table  3 C to reciprocate in the right-left direction at a constant stroke corresponding to a right-left width of the seedling mat. Every time the seedling loading table  3 C reaches a right or left stroke end, the vertical feed mechanism is driven by the lateral feed mechanism and, with this driving, feeds each of the seedling mats, which are loaded onto the seedling loading table  3 C, vertically and downwardly at a predetermined pitch. The planting mechanisms are arranged in the right-left direction at a constant interval corresponding to spacing between planting strips. Each of the planting mechanisms is configured to be of a rotary type having a pair of planting claws. Each of the planting mechanisms is driven by power from the power distribution unit and, with this driving, scrapes a predetermined amount of the seedlings from a lower end of each of the seedling mats to plant the seedlings in the field. The planting frame includes: a main member in a square pipe shape that extends in the right-left direction; a support frame that extends upward from the main member; plural transmission cases, each of which extends rearward from the main member. A right and left pair of the planting mechanisms is drivably attached to a rear end portion of each of the transmission cases. In each of the transmission cases, a transmission mechanism that transmits the power from the power distribution unit to the planting mechanism is provided. 
     The vehicle state detector  45  of the riding rice transplanter V 2  includes, instead of the plural remaining amount sensors  45 A (see  FIG. 3 ) exemplified in the first embodiment, plural seedling remaining amount sensors  45 B (indicated by two-dot chain lines in  FIG. 3 ), each of which detects that a remaining amount of any of the seedling mats for the number of the working strips, which are loaded onto the seedling loading table  3 C of the seedling planting device  3 , has dropped to a seedling replenishment setting value. 
       FIGS. 14 to 15  each illustrates an example of the work area Aw that is identified by the target path generation section  51 B for the field Ad, the target path P generated by the target path generation section  51 B for the field Ad, and the like in the case where, in the state where the field Ad is selected as the work target, the start position S is selected in the lower left portion of the field Ad on the selected field display screen  50 B illustrated in  FIG. 7 , the seedling planting device  3  is selected on the work device selection screen  50 C illustrated in  FIG. 8 , and the first headland area setting button  50 Da and the headland area work button  50 De are operated on the headland area setting screen  50 D illustrated in  FIG. 9 . 
     More specifically, for the field Ad illustrated in  FIGS. 14 to 15 , a pair of the first headland areas A 1  and a pair of the second headland areas A 2  are secured in the multiples of the work width in the area identification frame F of the field Ad, the central area A 3  in the area identification frame F excluding those headland areas A 1 , A 2  is identified as a rectangular first work area Aw 1 , and each of the headland areas A 1 , A 2  is identified as a frame-shaped second work area Aw 2 . Then, for the first work area Aw 1 , plural first work paths P 1  and plural first direction changing paths P 2 . The plural first work paths P 1  are arranged in parallel at a predetermined interval that corresponds to the working strips (the work width) of the seedling planting device  3 . The plural first direction changing paths P 2  connect the plural first work paths P 1  in a travel order of the riding rice transplanter V 2  from the start position S. Then, for the second work area Aw 2 , four second work paths P 3  along the area identification frame F, a single second direction changing path P 4 , and three third direction changing paths P 5  are generated. The second direction changing path P 4  connects the last first work path P 1  in the first work area Aw 1  to the first second work path P 3  in the second work area Aw 2 . The third direction changing paths P 5  connect the second work paths P 3  in the travel order of the riding rice transplanter V 2 . 
     The target paths P illustrated in  FIGS. 14 to 15  merely constitute an example. Based on the vehicle body information such as the turning radius and the working strip that vary by a model and the like of the riding rice transplanter V 2 , the field information such as the shape, the size, and the like of the field that vary among the fields Aa to Ag, and the like, the target path generation section  51 B can generate the various target paths P suited for those. 
     Although not illustrated, in the selected field display screen  50 B (see  FIG. 7 ) that is displayed on the display device  50  of the mobile communication terminal  5 , it is possible to perform a touch operation to select a field side (a field side As 1  in  FIGS. 14 to 15 ) that is suited to replenish the seedlings to the seeding planting device  3  of the riding rice transplanter V 2  among four field sides (corresponding to outline identification lines) As 1  to As 4  (see  FIG. 14 ) that identify the outline OL of the field Ad. The standby position setting section  46 K has a function as a specifying section that specifies the field side As 1  of the field Ad as the replenishment field side in response to the touch operation at the time when the touch operation is performed. In this way, for example, as illustrated in  FIGS. 14 to 15 , in the case where one of the paired first headland areas A 1  where a direction of the riding rice transplanter V 2  is changed is adjacent to the farm road Rf or the like where a carrier vehicle that is loaded with the replenishment seeding mats, and the like can be stopped, it is possible to specify the field side As 1  of the field Ad along the one first headland area A 1  as the seedling replenishment field side. For example, in the case where the utility pole, the tree, or the like that interferes with the replenishment of the seedlings exists on the field side As 3  that is along one of the paired first headland areas A 1  where the direction of the riding rice transplanter V 2  is changed, such a field side As 3  is not specified as the replenishment field side. In this way, it is possible to avoid a possibility that the field side As 3  is used as the replenishment field side. 
     Here, the seedling replenishment setting value in this second embodiment is set to a larger value than an amount of the seedlings that is consumed when the riding rice transplanter V 2  travels automatically on the two first work paths P 1  of the target path P. 
     In the automatic travel of the riding rice transplanter V 2 , which is along the target path P in the first work area Aw 1 , by the automatic travel control of the automatic travel control section  46 F, in the case where the standby position setting section  46 K detects that the remaining amount of any of the seedling mats for the number of the working strips, which are loaded onto the seedling loading table  3 C of the seedling planting device  3 , has dropped to the seedling replenishment setting value on the basis of the detection information from each of the seeding remaining amount sensors  45 B, the standby position setting section  46 K executes the standby position acquisition control. 
     A description will hereinafter be made on the standby position acquisition control by the standby position setting section  46 K for seedling planting work in the field Ad illustrated in  FIG. 14  with reference to a flowchart in  FIG. 16 . 
     The standby position setting section  46 K performs work path identification processing for identifying the first work path P 1  where the riding rice transplanter V 2  currently travels on the basis of the target path P and the current position of the riding rice transplanter V 2  in conjunction with the detection that the remaining amount of any of the seedling mats for the number of the working strips, which are loaded onto the seedling loading table  3 C, has dropped to the seedling replenishment setting value (step # 31 ). 
     The standby position setting section  46 K performs seventh judgment processing for determining whether the travel direction of the riding rice transplanter V 2  on the identified first work path (hereinafter referred to as the identified work path) P 1  is a direction to approach the seedling replenishment field side As 1  that is selected by the user&#39;s touch operation on the selected field display screen  50 B (step # 32 ). 
     In the case where the travel direction of the riding rice transplanter V 2  is the direction to approach the seedling replenishment field side As 1  in the seventh judgment processing, the standby position setting section  46 K performs first standby position setting processing for setting an intersection point of an extension line L of the identified work path P 1  with the seedling replenishment field side As 1  to a replenishment standby position p 0   a  on the basis of the identified work path P 1  and the seedling replenishment field side As 1  (step # 33 ), and thereafter terminates the standby position acquisition control. 
     In the case where the travel direction of the riding rice transplanter V 2  is not the direction to approach the seedling replenishment field side As 1  in the seventh judgment processing, the standby position setting section  46 K performs second standby position setting processing for setting an intersection point of the extension line L of the first work path (hereinafter referred to as a next process work path) P 1 , on which the riding rice transplanter V 2  travels after the identified work path P 1 , with the seedling replenishment field side As 1  as the replenishment standby position p 0   a  on the basis of the next process work path P 1  and the seedling replenishment field side As 1  (step # 34 ), and thereafter terminates the standby position acquisition control. 
     In the automatic travel of the riding rice transplanter V 2 , which is along the target path P in the first work area Aw 1 , by the automatic travel control, the automatic travel control section  46 F determines whether a first standby condition to cause the riding rice transplanter V 2  to stand by at the replenishment standby position p 0   a  is satisfied. In the case where the first standby condition is satisfied, the automatic travel control section  46 F executes seedling replenishment movement control to cause the riding rice transplanter V 2  to travel automatically from the current position to the replenishment standby position p 0   a  and to stand by at the replenishment standby position p 0   a.    
     More specifically, in this second embodiment, the standby position setting section  46 K sets the replenishment standby position p 0   a  in the case where the work vehicle is the riding rice transplanter V 2  and any of the plural seedling remaining amount sensors  45 B provided to the seedling loading table  3 C detects that the remaining amount of any of the seedling mats for the number of the working strips, which are loaded onto the seedling loading table  3 C, has dropped to the seedling replenishment setting value. Accordingly, the automatic travel control section  46 F is set to determine that the first standby condition is satisfied in the case where the standby position setting section  46 K sets the replenishment standby position p 0   a.    
     In other words, in the automatic travel of the riding rice transplanter V 2  by the automatic travel control, the automatic travel control section  46 F determines whether the standby position setting section  46 K has set the replenishment standby position p 0   a . In the case where the replenishment standby position p 0   a  has been set, the automatic travel control section  46 F executes the seedling replenishment movement control. 
     A description will hereinafter be made on the seedling replenishment movement control by the automatic travel control section  46 F for the seedling planting work in the field Ad illustrated in  FIG. 14  with reference to a flowchart in  FIGS. 17 to 18 . 
     In conjunction with the initiation of the seedling replenishment movement control, the automatic travel control section  46 F performs the remaining amount dropping notification processing for notifying the user that the remaining amount of the seedling mat loaded onto the seedling loading table  3 C has dropped to the seedling replenishment setting value by the display device  50  of the mobile communication terminal  5 , or the like (step # 41 ). 
     The automatic travel control section  46 F performs eighth determination processing for determining whether the replenishment standby position p 0   a , which is set by the standby position setting section  46 K, is the intersection point of the extension line L of the identified work path P 1  with the seedling replenishment field side As 1  (step # 42 ). 
     In the case where the replenishment standby position p 0   a  is the intersection point of the extension line L of the identified work path P 1  with the seedling replenishment field side As 1  in the eighth determination processing, the automatic travel control section  46 F performs first interruption position setting processing for setting the work stop point (end point) p 2  of the identified work path P 1  to the seedling replenishment interruption position p 3  on the basis of the target path P and the current position of the riding rice transplanter V 2  (step # 43 ). 
     In the case where the automatic travel control section  46 F determines that the replenishment standby position p 0   a  is not the intersection point of the extension line L of the identified work path P 1  with the seedling replenishment field side As 1  in the eighth determination processing, the automatic travel control section  46 F performs second interruption position setting processing for setting the work stop point (end point) p 2  of the next process work path P 1  to the seedling replenishment interruption position p 3  on the basis of the target path P and the current position of the riding rice transplanter V 2  (step # 44 ). 
     After setting the seedling replenishment interruption position p 3 , the automatic travel control section  46 F performs the resumption position setting processing and movement path setting processing. In the resumption position setting processing, the next work start point (start point of the next work path P 1 ) p 1  with respect to the interruption position p 3  is set to the resumption position p 4  after the replenishment of the seedlings. In the movement path setting processing, the extension line L of the identified work path P 1  from the seedling replenishment interruption position p 3  to the replenishment standby position p 0   a  or the extension line L of the next process work path P 1  is set as a replenishment movement path Pm 3 , and this replenishment movement path Pm 3  and the first direction changing path P 2  from the interruption position p 3  to the resumption position p 4  are set as a resumption movement path Pm 4  (steps # 45  to  46 ). 
     The automatic travel control section  46 F performs ninth determination processing for determining whether the riding rice transplanter V 2  has reached the interruption position p 3  (step # 47 ). In the ninth determination processing, the automatic travel control section  46 F continues the seedling planting work under the automatic travel control until the riding rice transplanter V 2  reaches the interruption position p 3 . Then, when the riding rice transplanter V 2  reaches the interruption position p 3 , the automatic travel control section  46 F performs the automatic travel control interruption processing for interrupting the automatic travel control (step # 48 ). 
     After the interruption of the automatic travel control, the automatic travel control section  46 F initiates the replenishment movement processing and the replenishment movement notification processing (steps # 49  to  50 ). In the replenishment movement processing, the riding rice transplanter V 2  travels automatically from the interruption position p 3  to the replenishment standby position p 0   a  along the replenishment movement path Pm 3 . In the replenishment movement notification processing, the user is notified that the riding rice transplanter V 2  currently travels to the replenishment standby position p 0   a  by the display device  50  of the mobile communication terminal  5 , or the like. 
     The automatic travel control section  46 F performs tenth determination processing for determining whether the riding rice transplanter V 2  has reached the replenishment standby position p 0   a  (step # 51 ). In the tenth determination processing, the automatic travel control section  46 F continues the replenishment movement processing and the replenishment movement notification processing until the riding rice transplanter V 2  reaches the replenishment standby position p 0   a . When the riding rice transplanter V 2  reaches the replenishment standby position p 0   a , the automatic travel control section  46 F terminates the replenishment movement processing and the replenishment movement notification processing, and causes the riding rice transplanter V 2  to stand by at the replenishment standby position p 0   a  (steps # 52  to  53 ). 
     The automatic travel control section  46 F performs eleventh determination processing for determining whether the user has performed the touch operation on the display device  50  of the mobile communication terminal  5  to command the resumption of the automatic travel of the riding rice transplanter V 2  by the automatic travel control while the riding rice transplanter V 2  stands by at the replenishment standby position p 0   a  (step # 54 ). 
     In the eleventh determination processing, the automatic travel control section  46 F initiates the resumption movement processing and the resumption movement notification processing (steps # 55  to  56 ). In the resumption movement processing, until the resumption of the automatic travel is commanded, it is determined that the replenishment of the seeds to each of the storage sections  3 Ba is not completed, and the riding rice transplanter V 2  stands by at the replenishment standby position p 0   a . Then, when the resumption of the automatic travel is commanded, it is determined that the replenishment of the seeds to each of the storage sections  3 Ba is completed, and the riding rice transplanter V 2  travels automatically from the replenishment standby position p 0   a  to the resumption position p 4  along the resumption movement path Pm 4 . In the resumption movement notification processing, the user is notified that the riding rice transplanter V 2  currently travels to the resumption position p 4  by the display device  50  of the mobile communication terminal  5 , or the like. 
     The automatic travel control section  46 F performs twelfth determination processing for determining whether the riding rice transplanter V 2  has reached the resumption position p 4  (step # 57 ). In the twelfth determination processing, the automatic travel control section  46 F continues the resumption movement processing and the resumption movement notification processing until the riding rice transplanter V 2  reaches the resumption position p 4 . Then, when the riding rice transplanter V 2  reaches the resumption position p 4 , the automatic travel control section  46 F terminates the resumption movement processing and the resumption movement notification processing (steps # 58  to  59 ). 
     After terminating the resumption movement processing and the resumption movement notification processing, the automatic travel control section  46 F performs the automatic travel control resumption processing for resuming the automatic travel of the riding rice transplanter V 2  by the automatic travel control (step # 60 ), and thereafter terminates the seedling replenishment movement control. 
     With the configuration that has been described so far, in this automatic travel system for a work vehicle, in the case where the standby position setting section  46 K detects that the remaining amount of the seedling mat in the seedling planting device  3  has dropped to the seedling replenishment setting value, the standby position setting section  46 K executes the standby position acquisition control to acquire the intersection point of the seedling replenishment field side As 1  in any of the fields Aa to Ag as the work target with the extension line L of the identified work path P 1  or the extension line L of the next process work path P 1  and to set this intersection point as the replenishment standby position p 0   a . In this way, the user no longer has to set the replenishment standby position p 0   a  for each of the fields Aa to Ag. 
     The replenishment standby position p 0   a  is the intersection point of the seedling replenishment field side As 1 , which is adjacent to the farm road Rf where the carrier vehicle loaded with the replenishment seedling mats, and the like can be stopped, with the extension line L of the identified work path P 1  or the extension line L of the next process work path P 1 . Accordingly, in the case where the seedling mats are replenished to the seedling planting device  3  of the riding rice transplanter V 2  that stands by at the replenishment standby position p 0   a , the carrier vehicle loaded with the seedling mats, or the like can be easily brought close to the riding rice transplanter V 2  at the replenishment standby position p 0   a . In this way, it is possible to reduce labor required to replenish the seedlings from the carrier vehicle or the like to the seedling planting device  3  of the riding rice transplanter V 2 . 
     In addition, in this automatic travel system for a work vehicle, in the case where the remaining amount of the seedling mat in the seedling planting device  3  drops to the seedling replenishment setting value and the standby position setting section  46 K sets the replenishment standby position p 0   a , the automatic travel control section  46 F executes the seedling replenishment movement control to move the riding rice transplanter V 2  to the replenishment standby position p 0   a  and to thereafter cause the riding rice transplanter V 2  to stand by at the replenishment standby position p 0   a . In this way, the user no longer has to cause the riding rice transplanter V 2  to travel manually from the interruption position p 3  to the replenishment standby position p 0   a.    
     Furthermore, in this automatic travel system for a work vehicle, in the case where the replenishment of the seedling mats to the seedling loading table  3 C of the seedling planting device  3  is completed and the user performs the touch operation on the display device  50  of the mobile communication terminal  5  to command the resumption of the automatic travel of the riding rice transplanter V 2  by the automatic travel control while the riding rice transplanter V 2  stands by at the replenishment standby position p 0   a , the automatic travel control section  46 F moves the riding rice transplanter V 2  from the replenishment standby position p 0   a  to the resumption position p 4 , and thereafter resumes the automatic travel of the riding rice transplanter V 2  along the target path P by the automatic travel control. In this way, the user no longer has to cause the riding rice transplanter V 2  to travel manually from the replenishment standby position p 0   a  to the resumption position p 4 . 
     In other words, the setting of the replenishment standby position p 0   a  in each of the fields Aa to Ag and the movement of the riding rice transplanter V 2  to the replenishment standby position p 0   a  can be performed automatically and appropriately. Thus, the replenishment work for the seedling planting device  3  of the riding rice transplanter V 2  can be performed efficiently while the burden on the user is reduced. 
     Moreover, in this automatic travel system for a work vehicle, the interruption position p 3  in the seedling planting work is set at the work stop point p 2  on the identified work path P 1  or the next process work path P 1 . Thus, even in the case where the remaining amount of the seedling mat in the seedling planting device  3  drops to the seedling replenishment setting value in the middle of the work path P 1 , the riding rice transplanter V 2  can continue the seedling planting work to the work stop point p 2  on the identified work path P 1  or the next process work path P 1  under the automatic travel control. In addition, the resumption position p 4  after the replenishment of the seedlings is set at the next work start point (start point of the next work path P 1 ) p 1  from the interruption position p 3 . Thus, for example, compared to a case where the resumption position p 4  after the replenishment of the seedlings (the interruption position p 3  in the seedling planting work) is set at a position in the middle of the identified work path P 1 , in the resumption movement processing for causing the riding rice transplanter V 2  to travel automatically to the resumption position p 4 , the riding rice transplanter V 2  no longer has to travel forward to a position near the resumption position p 4 , thereafter be switched to the reverse travel state, and travel reversely to the resumption position p 4 . As a result, the riding rice transplanter V 2  can travel automatically and efficiently to the resumption position p 4 . 
     The interruption position p 3  in the seedling planting work is the work stop point p 2  on the identified work path P 1  or the next process work path P 1  near the seedling replenishment field side As 1 . The resumption position p 4  after the replenishment of the seedlings is the next work start point p 1  that is adjacent to the interruption position p 3  near the seedling replenishment field side As 1 . Accordingly, it is possible to shorten the replenishment movement path Pm 3  from the interruption position p 3  to the replenishment standby position p 0   a  and the resumption movement path Pm 4  from the replenishment standby position p 0   a  to the resumption position p 4 . As a result, it is possible to reduce the time required for the movement of the riding rice transplanter V 2  from the interruption position p 3  to the replenishment standby position p 0   a  and the movement thereof from the replenishment standby position p 0   a  to the resumption position p 4 . 
     In this automatic travel system for a work vehicle, in both of the replenishment movement processing and the resumption movement processing, the riding rice transplanter V 2  travels along the extension line L of the identified work path P 1  or the next process work path P 1  and the first direction changing path P 2 . Thus, it is possible to avoid a possibility that the riding rice transplanter V 2  tramples the worked area Awa of each of the fields Aa to Ag and a possibility of forming the ruts, which adversely affect the seedling planting work, in the unworked area Awb of each of the fields Aa to Ag. 
     In the case where the user performs the touch operation on a path acquisition button (not illustrated) that is displayed on the display device  50  of the mobile communication terminal  5 , the standby position setting section  46 K executes off-field movement path acquisition control to acquire, as an off-field movement path Pm 5  (see  FIGS. 14 to 15 ), the manual travel path Rm of the riding rice transplanter V 2  outside any of the fields Aa to Ag. 
     A description will hereinafter be made on the off-field movement path acquisition control for the field Ad illustrated in  FIGS. 14 to 15  by the standby position setting section  46 K for the sowing work in the field Ad illustrated in  FIG. 5  with reference to a flowchart in  FIG. 19 . 
     In conjunction with the user&#39;s touch operation on the path acquisition button, the standby position setting section  46 K performs start point acquisition processing for acquiring a manual travel start point p 5  of the riding rice transplanter V 2  with respect to the field Ad from the position information of the riding rice transplanter V 2  measured by the positioning unit  70  (step # 61 ). Thereafter, the standby position setting section  46 K initiates the path acquisition processing for acquiring the manual travel path Rm of the riding rice transplanter V 2  (step # 62 ). 
     The standby position setting section  46 K performs thirteenth determination processing for determining whether the riding rice transplanter V 2  has reached the travel area in the field Ad on the basis of the currently-acquired manual travel path Rm and the area identification frame F of the field Ad included in the information on the field Ad (step # 63 ). More specifically, the standby position setting section  46 K determines whether the currently-acquired manual travel path Rm has contacted the area identification frame F of the field Ad. 
     In the thirteenth determination processing, the standby position setting section  46 K continues the path acquisition processing until the riding rice transplanter V 2  reaches the travel area in the field Ad. Then, when the riding rice transplanter V 2  reaches the travel area in the field Ad, the standby position setting section  46 K performs arrival point acquisition processing for acquiring an arrival point p 6  thereof (step # 64 ). 
     More specifically, in the case where the currently-acquired manual travel path Rm comes into contact with the area identification frame F of the field Ad, it is determined that the riding rice transplanter V 2  has reached the travel area in the field Ad. Then, a contact point between the manual travel path Rm and the area identification frame F is set as the arrival point p 6  of the riding rice transplanter V 2  at the travel area in the field Ad. 
     After acquiring the arrival point p 6 , the standby position setting section  46 K performs off-field movement path storing processing, start position setting processing, and the standby position setting processing (steps # 65  to  67 ). In the off-field movement path storing processing, the manual travel path Rm from the manual travel start point p 5  to the arrival point p 6  is set as the off-field movement path Pm 5  and stored in the vehicle-mounted storage section  46 G. In the start position setting processing, the arrival point p 6  is set as a travel start position at the time when the riding rice transplanter V 2  travels automatically along the off-field movement path Pm 5 . In the standby position setting processing, the manual travel start point p 5  is set as a standby position (hereinafter referred to as an off-field standby position) p 0   b  of the riding rice transplanter V 2  outside the field Ad. Thereafter, the standby position setting section  46 K terminates the path acquisition processing (step # 68 ), and terminates the off-field movement path acquisition control. 
     In conjunction with the termination of the automatic travel control to cause the riding rice transplanter V 2  to travel automatically along the target path P in the field Ad illustrated in  FIGS. 14 to 15 , the automatic travel control section  46 F determines whether a second standby condition to cause the riding rice transplanter V 2  to stand by at an off-field standby position p 0   b  is satisfied. Then, in the case where the second standby condition is satisfied, the automatic travel control section  46 F executes off-field automatic travel control to cause the riding rice transplanter V 2  to travel automatically from the current position (the end point of the target path P) to the off-field standby position p 0   b  and to stand by at the off-field standby position p 0   b.    
     More specifically, the automatic travel control section  46 F is set to determine that the second standby condition is satisfied in the case where the standby position setting section  46 K has set the off-field movement path Pm 5 , the travel start position p 6 , and the off-field standby position pOb at a stage where the riding rice transplanter V 2  reaches the end point of the target path P. 
     In other words, at the stage where the riding rice transplanter V 2  reaches the end point of the target path P, the automatic travel control section  46 F determines whether the standby position setting section  46 K has set the off-field movement path Pm 5 , the travel start position p 6 , and the off-field standby position p 0   b . Then, in the case where the standby position setting section  46 K has set the off-field movement path Pm 5 , the travel start position p 6 , and the off-field standby position p 0   b , the automatic travel control section  46 F executes the off-field automatic travel control. 
     In this way, after the riding rice transplanter V 2  finishes the seedling planting work in the field Ad and reaches the end point of the target path P, as illustrated in  FIG. 15 , the riding rice transplanter V 2  can travel automatically to the off-field standby position p 0   b  along the off-field movement path Pm 5 . Then, upon arrival to the off-field standby position p 0   b , the riding rice transplanter V 2  can stand by at the off-field standby position p 0   b.    
     As a result, as illustrated in  FIGS. 14 to 15 , in the case where the off-field standby position p 0   b  is a loading/unloading position for a carrier vehicle Z that transports the riding rice transplanter V 2 , it is possible to eliminate time and effort for causing the riding rice transplanter V 2  to travel manually from the field Ad to the loading/unloading position. Alternatively, in the case where the off-field standby position p 0   b  is an installation position of a barn in which the riding rice transplanter V 2  is stored, or the like, it is possible to eliminate time and effort for causing the riding rice transplanter V 2  to travel manually from the field Ad to the barn. Furthermore, in the case where the off-field standby position p 0   b  is a position near the registered field to be worked after the field Ad, it is possible to eliminate time and effort for causing the riding rice transplanter V 2  to travel manually from the field Ad to a position in the vicinity of the next registered field and also to improve work efficiency. 
     In the second embodiment, such an aspect has been exemplified that the standby position setting section  46 K executes the off-field movement path acquisition control in the case where the user performs the touch operation on the path acquisition button that is displayed on the display device  50  of the mobile communication terminal  5 . However, for example, in the case where the off-field standby position p 0   b  is the loading/unloading position for the carrier vehicle Z that transports the riding rice transplanter V 2 , the standby position setting section  46 K may initiate the off-field movement path acquisition control when the gear shift operation is performed to switch a gear shift state of the transmission unit  15  in the riding rice transplanter V 2  from the ultra-low speed stage for unloading to the high-speed stage for travel. Meanwhile, for example, in the case where the off-field standby position p 0   b  is the installation position of the barn, which stores the riding rice transplanter V 2 , or the like, the standby position setting section  46 K may initiate the off-field movement path acquisition control when a power-on operation of the riding rice transplanter V 2  is performed. 
     Third Embodiment 
     A description will hereinafter be made on, as an example of the mode for carrying out the present invention, a third embodiment in which the automatic travel system for a work vehicle according to the present invention is applied to the combine harvester as an example of the work vehicle with reference to the drawings. 
     The automatic travel system for a work vehicle exemplified in this third embodiment differs from the automatic travel systems for a work vehicle exemplified in the first embodiment and the second embodiment in terms of, in addition to the applied work vehicle, the control actuation of the standby position setting section  46 K and the automatic travel control section  46 F, and the like. Thus, a description will be made on a main configuration of the applied work vehicle, the control actuation of the standby position setting section  46 K and the automatic travel control section  46 F, and the like. 
     As illustrated in  FIGS. 20 to 21 , the combine harvester V 3  exemplified in this third embodiment has a travel body (not illustrated) with a full crawler specification that corresponds to the tractor V 1  exemplified in the first embodiment and the travel body  1  exemplified in the second embodiment and that is equipped with: a work device for harvesting grain culms (hereinafter referred to as a harvesting and conveying device)  3 ; a threshing device  8  that performs threshing and sorting processing on the grain culms harvested and conveyed by the harvesting and conveying device  3 ; a grain tank  9  that stores grain from the threshing device  8 ; and the like. The grain tank  9  includes a grain discharger  9 A of a screw conveyance type that discharges the grain stored therein to a platform of the carrier vehicle Z or the like outside the machine. In this way, this combine harvester V 3  can harvest the grain culms, which are planted in the field Ad as the work target, by the harvesting and conveying device  3  provided in a front portion thereof. Then, the grain that is obtained by subjecting the harvested grain culms to the threshing and sorting processing can be stored in the grain tank  9 . 
     Here,  FIGS. 20 to 21  each exemplify a case where the field Ad of the fields Aa to Ag is selected as the work target. 
     The vehicle state detector  45  of the combine harvester V 3  includes, instead of the plural remaining amount sensors  45 A (see  FIG. 3 ) exemplified in the first embodiment and the plural seedling remaining amount sensors  45 B (see  FIG. 3 ) exemplified in the second embodiment, a full sensor  45 C (indicated by two-dot chain lines in  FIG. 3 ) detecting that an amount of the grain stored in the grain tank  9  has reached a grain discharge setting value. 
       FIGS. 20 to 21  each illustrate an example of the target path P and the like. The target path P is generated in the field Ad by the target path generation section  51 B in the case where, in the state where the field Ad is selected as the work target, the harvesting and conveying device  3  is selected on the work device selection screen  50 C illustrated in  FIG. 8 . 
     More specifically, for the field Ad illustrated in  FIGS. 20 to 21 , an area within the area identification frame F of the field Ad is identified as the rectangular work area Aw, and the target path P for rotary harvesting is generated for this work area Aw. This target path P includes: the plural work paths P 1  that are arranged in parallel with field sides of the field Ad at predetermined intervals corresponding to the number of the working strips (the work width) of the harvesting and conveying device  3 ; and the plural direction changing paths P 2  that connect the plural work paths P 1  in a travel order of the combine harvester V 3  from the start position S. 
     The target paths P illustrated in  FIGS. 20 to 21  merely constitute an example. Based on the vehicle body information such as the turning radius and the working strip that vary by a model and the like of the combine harvester V 3 , the field information such as the shape, the size, and the like of the field that vary among the fields Aa to Ag, and the like, the target path generation section  51 B can generate the various target paths P suited for those. 
     The standby position setting section  46 K executes the standby position acquisition control exemplified in the first embodiment in the case where the user performs the touch operation on a standby position setting button (not illustrated) that is displayed on the display device  50  of the mobile communication terminal  5 . In this way, an entry point of the combine harvester V 3  to the field Ad is set to the standby position (hereinafter referred to as a discharge standby position) p 0  (see  FIG. 20 ) of the combine harvester V 3  at the time of discharging the grain stored in the grain tank  9  of the combine harvester V 3  to the outside of the machine. Together with the manual travel path Rm (see  FIG. 20 ) from this discharge standby position p 0  to the start position S of the automatic travel, the discharge standby position p 0  is stored in the vehicle-mounted storage section  46 G. 
     The automatic travel control section  46 F determines whether a standby condition for causing the combine harvester V 3  to stand by at the discharge standby position p 0  is satisfied in the automatic travel state where the automatic travel control is executed to cause the combine harvester V 3  to travel automatically along the target path P. Then, in the case where the standby condition is satisfied, the automatic travel control section  46 F executes grain discharge movement control to cause the combine harvester V 3  to travel automatically from the current position to the discharge standby position p 0  and to stand by at the discharge standby position p 0 . 
     More specifically, since the work vehicle is the combine harvester V 3  in this third embodiment, the automatic travel control section  46 F is set to determine that the standby condition is satisfied in the case where the full sensor  45 C provided to the grain tank  9  detects that the amount of the grain stored in the grain tank  9  has reached the grain discharge setting value. 
     In other words, in the automatic travel state of the combine harvester V 3  under the automatic travel control, the automatic travel control section  46 F determines whether the amount of the grain stored in the grain tank  9  has reached the grain discharge setting value on the basis of detection information from the full sensor  45 C. Then, in the case where the storage amount has reached the grain discharge setting value, the automatic travel control section  46 F executes the grain discharge movement control. 
     Here, the grain discharge setting value in this third embodiment is set to such a value that the grain obtained during the automatic travel of the combine harvester V 3  on the single work path P 1  of the target path P can be stored in the grain tank  9 . 
     A description will hereinafter be made on the grain discharge movement control by the automatic travel control section  46 F for harvesting work in the field Ad illustrated in  FIG. 20  with reference to a flowchart in  FIG. 22 . 
     In conjunction with initiation of the grain discharge movement control, the automatic travel control section  46 F performs full notification processing for notifying the user that the amount of the grain stored in the grain tank  9  has reached the grain discharge setting value by the display device  50  of the mobile communication terminal  5 , or the like (step # 71 ). 
     The automatic travel control section  46 F performs the interruption position setting processing and the resumption position setting processing on the basis of the target path P and the current position of the combine harvester V 3  (steps # 72  to # 73 ). In the interruption position setting processing, the work stop point (end point) p 2  on the work path P 1  where the combine harvester V 3  currently travels is set as the grain discharge interruption position p 3 . In the resumption position setting processing, the next work start point (start point of the next work path P 1 ) p 1  from the interruption position p 3  is set as the resumption position p 4  after the grain discharge. 
     After setting the above positions, the automatic travel control section  46 F performs discharge path generation processing and the resumption path generation processing by using the already-traveled path (paths indicated by bold lines of the target path P illustrated in  FIG. 20 ) of the target path P and the manual travel path Rm stored in the vehicle-mounted storage section  46 G (steps # 74  to  75 ). In the discharge path generation processing, the shortest discharge movement path Pm 6  from the grain discharge interruption position p 3  to the discharge standby position p 0  is generated. In the resumption path generation processing, the shortest resumption movement path Pm 7  from the discharge standby position p 0  to the resumption position p 4  after the grain discharge is generated. 
     Although not illustrated, the resumption movement path Pm 7  includes, in a path start end portion thereof, a direction changing path to change a direction of the combine harvester V 3  from the reverse posture to the forward posture. 
     The automatic travel control section  46 F performs fourteenth determination processing for determining whether the combine harvester V 3  has reached the interruption position p 3  (step # 76 ). In the fourteenth determination processing, the automatic travel control section  46 F continues the harvesting work by the automatic travel control until the combine harvester V 3  reaches the interruption position p 3 . Then, in the case where the combine harvester V 3  reaches the interruption position p 3 , the automatic travel control section  46 F performs the automatic travel control interruption processing for interrupting the automatic travel control (step # 77 ). 
     After the interruption of the automatic travel control, the automatic travel control section  46 F initiates discharge movement processing and discharge movement notification processing (steps # 78  to  79 ). In the discharge movement processing, the combine harvester V 3  travels automatically from the interruption position p 3  to the discharge standby position p 0  along the discharge movement path Pm 6 . In the discharge movement notification processing, the user is notified that the combine harvester V 3  currently travels to the discharge standby position p 0  by the display device  50  of the mobile communication terminal  5 , or the like. 
     The automatic travel control section  46 F performs fifteenth determination processing for determining whether the combine harvester V 3  has reached the discharge standby position p 0  (step # 80 ). In the fifteenth determination processing, the automatic travel control section  46 F continues the discharge movement processing and the discharge movement notification processing until the combine harvester V 3  reaches the discharge standby position p 0 . Then, when the combine harvester V 3  reaches the discharge standby position p 0 , the automatic travel control section  46 F terminates the discharge movement processing and the discharge movement notification processing and causes the combine harvester V 3  to stand by at the discharge standby position p 0  (step # 81  to  82 ). 
     The automatic travel control section  46 F performs sixteenth determination processing for determining whether the user has performed the touch operation on the display device  50  of the mobile communication terminal  5  to command the resumption of the automatic travel of the combine harvester V 3  by the automatic travel control while the combine harvester V 3  stands by at the discharge standby position p 0  (step # 83 ). 
     In the sixteenth determination processing, until the resumption of the automatic travel is commanded, the automatic travel control section  46 F determines that the discharge of the grain from the grain tank  9  is not completed, and causes the combine harvester V 3  to stand by at the discharge standby position p 0 . Then, in the case where the resumption of the automatic travel is commanded, the automatic travel control section  46 F determines that the discharge of the grain from the grain tank  9  is completed, and initiates: the resumption movement processing for causing the combine harvester V 3  to travel automatically from the discharge standby position p 0  to the resumption position p 4  along the resumption movement path Pm 7 ; and the resumption movement notification processing for notifying the user that the combine harvester V 3  currently travels to the resumption position p 4  by the display device  50  of the mobile communication terminal  5 , or the like (steps # 84  to  85 ). 
     The automatic travel control section  46 F performs seventeenth determination processing for determining whether the combine harvester V 3  has reached the resumption position p 4  (step # 86 ). In the seventeenth determination processing, the automatic travel control section  46 F continues the resumption movement processing and the resumption movement notification processing until the combine harvester V 3  reaches the resumption position p 4 . Then, when the combine harvester V 3  reaches the resumption position p 4 , the automatic travel control section  46 F terminates the resumption movement processing and the resumption movement notification processing (steps # 87  to  88 ). 
     After terminating the resumption movement processing and the resumption movement notification processing, the automatic travel control section  46 F performs the automatic travel control resumption processing for resuming the automatic travel of the combine harvester V 3  by the automatic travel control (step # 89 ), and thereafter terminates the grain discharge movement control. 
     With the configuration that has been described so far, in this automatic travel system for a work vehicle, in the case where the user performs the touch operation on the standby position setting button that is displayed on the display device  50  of the mobile communication terminal  5 , the standby position setting section  46 K executes the standby position acquisition control to acquire the entry point of the combine harvester V 3  to any of the fields Aa to Ag as the work target, and sets this entry point as the discharge standby position p 0 . In this way, the user no longer has to set the discharge standby position p 0  for each of the fields Aa to Ag. 
     The entry point that is set at the discharge standby position p 0  is the entrance/exit of each of the fields Aa to Ag, by which each of the fields Aa to Ag is connected to the farm road Rf or the like where the carrier vehicle Z for transporting the grain that is loaded with the grain from the grain tank  9  of the combine harvester V 3 , and the like can be stopped. In this way, the carrier vehicle Z for transporting the grain and the like can be stopped near the discharge standby position p 0 . As a result, after the combine harvester V 3  reaches the discharge standby position p 0 , it is possible to smoothly perform grain discharge work from the grain tank  9  of the combine harvester V 3  to the platform of the carrier vehicle Z, or the like. 
     In addition, in this automatic travel system for a work vehicle, in the case where the amount of the grain stored in the grain tank  9  reaches the grain discharge setting value, the automatic travel control section  46 F executes the grain discharge movement control to move the combine harvester V 3  to the discharge standby position p 0  and then to stand by at the discharge standby position p 0 . In this way, the user no longer has to cause the combine harvester V 3  to travel manually from the interruption position p 3  to the discharge standby position p 0 . 
     Furthermore, in this automatic travel system for a work vehicle, in the case where the discharge of the grain from the grain tank  9  is completed and the user performs the touch operation on the display device  50  of the mobile communication terminal  5  to command the resumption of the automatic travel control of the combine harvester V 3  by the automatic travel control while the combine harvester V 3  stands by at the discharge standby position p 0 , the automatic travel control section  46 F moves the combine harvester V 3  from the discharge standby position p 0  to the resumption position p 4 , and thereafter resumes the automatic travel of the combine harvester V 3  along the target path P by the automatic travel control. In this way, the user no longer has to cause the combine harvester V 3  to travel manually from the discharge standby position p 0  to the resumption position p 4 . 
     In other words, the setting of the discharge standby position p 0  in each of the fields Aa to Ag and the movement of the combine harvester V 3  to the discharge standby position p 0  can be performed automatically and appropriately. Thus, grain discharge work from the grain tank  9  of the combine harvester V 3  can be performed efficiently while the burden on the user is reduced. 
     Moreover, in this automatic travel system for a work vehicle, the interruption position p 3  of the harvesting work is set at the work stop point p 2  of the currently traveled work path P 1 . Thus, even in the case where the amount of the grain stored in the grain tank  9  reaches the grain discharge setting value in the middle of the work path P 1 , the combine harvester V 3  can continue the harvesting work to the work stop point p 2  of the currently traveled work path P 1  under the automatic travel control. In addition, the resumption position p 4  after the grain discharge is set at the next work start point (start point of the next work path P 1 ) p 1  from the interruption position p 3 . Thus, for example, compared to a case where the resumption position p 4  after the grain discharge (the interruption position p 3  of the harvesting work) is set at the position in the middle of the currently traveled work path P 1 , in the discharge movement processing for causing the combine harvester V 3  to travel automatically from the interruption position p 3  to the discharge standby position p 0 , the combine harvester V 3  no longer has to travel reversely from the interruption position p 3 , thereafter be switched to the forward travel state, and travel forward to the discharge standby position p 0 . As a result, the combine harvester V 3  can travel automatically and efficiently to the discharge standby position p 0 . 
     In this automatic travel system for a work vehicle, in both of the discharge movement processing and the resumption movement processing, the combine harvester V 3  travels along the already-traveled path of the target path P and the manual travel path Rm. Thus, it is possible to avoid a possibility that the combine harvester V 3  tramples the unworked area Awb of each of the fields Aa to Ag. 
     Although not illustrated, in the selected field display screen  50 B (see  FIG. 7 ) displayed on the display device  50  of the mobile communication terminal  5 , a touch operation can be performed to set the discharge standby position p 0  at plural locations in the field Ad. In the case where such a touch operation is performed, the standby position setting section  46 K sets the discharge standby position p 0  at the plural locations in the field Ad corresponding to the touch operation. 
     As illustrated in  FIG. 3 , the vehicle-mounted control unit  46  includes a standby position selection section  46 L (indicated by two-dot chain lines in  FIG. 3 ) that selects the single discharge standby position p 0  from the plural discharge standby positions p 0  in the case where the discharge standby position p 0  is set at the plural locations in the field Ad. The standby position selection section  46 L is constructed of an electronic control unit, in which a microcontroller and the like are integrated, various control programs, and the like. The standby position selection section  46 L is connected to the other control sections  46 A to  46 F,  4611 ,  46 K of the vehicle-mounted control unit  46  and the like in the mutually communicable manner via the CAN. 
     For example, as illustrated in  FIG. 21 , the plural (two in  FIG. 21 ) discharge standby positions p 0  are set at a field end of the field Ad, and the field end is adjacent to the farm road Rf, where the carrier vehicle Z for transporting the grain and the like can be stopped, and the like. In such a case, the standby position selection section  46 L performs standby position selection processing for selecting the appropriate discharge standby position p 0  for the current grain discharge work on the basis of the current position of the combine harvester V 3  at the time when the above-described standby condition is satisfied, the number of movement of the combine harvester V 3  to each of the discharge standby positions p 0 , and the like. In addition, the standby position selection section  46 L performs selected standby position notification processing for notifying the user of the selected discharge standby position p 0  by the display device  50  of the mobile communication terminal  5 , or the like. 
     More specifically, for example, in the case where one of the discharge standby positions p 0  is closer to the interruption position p 3 , which is set from the current position of the combine harvester V 3  at the time when the above-described standby condition is satisfied, than the other discharge standby position p 0 , in the standby position selection processing, the standby position selection section  46 L selects the one discharge standby position p 0  that is closer as the current discharge standby position p 0 . In this way, it is possible to reduce the time required for the movement of the combine harvester V 3  between the interruption position p 3  and the discharge standby position p 0  and thus to perform the grain discharge work efficiently. 
     Alternatively, for example, in the case where the number of the movement of the combine harvester V 3  to the one discharge standby position p 0  is smaller than the number of the movement of the combine harvester V 3  to the other discharge standby position p 0 , in the standby position selection processing, the standby position selection section  46 L selects the one discharge standby position p 0  with the smaller number of the movement as the current discharge standby position p 0 . In this way, it is possible to suppress the discharge standby position p 0  from becoming severely muddy due to the increased number of the movement of the combine harvester V 3 . 
     In addition, due to the selected standby position notification process by the standby position selection section  46 L, the user can comprehend in advance the discharge standby position p 0  to be used in the current grain discharge work. As a result, the user can move the carrier vehicle Z for transporting the grain or the like to the discharge standby position p 0  in accordance with the movement of the combine harvester V 3  to the discharge standby position p 0  that is selected by the standby position selection section  46 L in the grain discharge movement control by the automatic travel control section  46 F. 
     Fourth Embodiment 
     A description will hereinafter be made on, as an example of the mode for carrying out the present invention, a fourth embodiment in which the automatic travel system for a work vehicle according to the present invention is applied to the riding mower as an example of the work vehicle with reference to the drawings. 
     The automatic travel system for a work vehicle exemplified in this second embodiment differs from the automatic travel systems for a work vehicle exemplified in the first embodiment to the third embodiment in terms of, in addition to the applied work vehicle, the control actuation of the standby position setting section  46 K and the automatic travel control section  46 F, and the like. Thus, a description will be made on a main configuration of the applied work vehicle, the control actuation of the standby position setting section  46 K and the automatic travel control section  46 F, and the like. 
     As illustrated in  FIGS. 23 to 26 , in a riding mower V 4  exemplified in this fourth embodiment, a work device for mowing (hereinafter referred to as the mower)  3  is coupled to the rear portion of the tractor V 1 , which is exemplified in the first embodiment, via the three-point linkage mechanism  2 . The mower  3  is coupled to the rear portion of the tractor V 1  in the liftable and rollable manner. In  FIG. 23 , a landing area A of an airport is exemplified as an example of the registered work site. 
     As illustrated in  FIGS. 23 to 26 , the landing area A includes plural vegetated areas  91  that are adjacent to a runway  90 .  FIGS. 23 to 26  each illustrate an example of the work area Aw, which is identified by the target path generation section  51 B for the landing area A, the generated target path P, and the like. 
     More specifically, each of the vegetated areas  91  is identified as the work area Aw for the landing area A, and the target path P is generated for each of the work areas Aw. Each of the target paths P includes: the four first work paths P 1  along a periphery of the respective work area Aw; three second direction changing paths P 2  that connect the plural first work paths P 1  in a travel order of the riding mower V 4 ; the plural second work paths P 3  that are arranged in parallel at predetermined intervals corresponding to the work width of the mower  3 ; the single second direction changing path P 4  that connects the last first work path P 1  to the predetermined second work paths P 3 ; the plural third direction changing paths P 5  that connect the second work paths P 3  in the travel order of the riding mower V 4 . Between the work areas Aw, a movement path Pm is generated to connect those target paths P in the travel order of the riding mower V 4 . 
     The target path P illustrated in  FIGS. 23 to 26  merely constitutes an example. Based on the vehicle body information such as the turning radii, the work widths, and the like that vary by models and the like of the tractor V 1  and the mower  3 , work site information such as a shape, size, and the like of the vegetated area  91  that vary by the landing area A, and the like, the target path generation section  51 B can generate the various target paths P that are suited for those. 
     Although not illustrated, in the selected field display screen  50 B (see  FIG. 7 ) that is displayed on the display device  50  of the mobile communication terminal  5 , a touch operation can be performed to set a standby position (hereinafter referred to as an evacuation standby position) p 0  (see  FIGS. 23 to 26 ) of the riding mower V 4  at the time of evacuating the riding mower V 4  during takeoff and landing of an aircraft at plural locations away from the runway  90  by a predetermined distance or longer. In the case where such a touch operation is performed, the standby position setting section  46 K sets the evacuation standby position p 0  at the plural locations corresponding to the touch operation. In  FIGS. 23 to 26 , a connection point (entry/exit point) for each of the vegetated areas  91  that connects the respective vegetated area  91  in the landing area A to a perimeter road  92  located outside the landing area A is set as the evacuation standby position p 0 . 
     As illustrated in  FIG. 3 , the vehicle-mounted control unit  46  includes the standby position selection section  46 L (indicated by the two-dot chain lines in  FIG. 3 ) that selects the single evacuation standby position p 0  from the plural evacuation standby positions p 0 . The standby position selection section  46 L is constructed of the electronic control unit, in which the microcontroller and the like are integrated, the various control programs, and the like. The standby position selection section  46 L is connected to the other control sections  46 A to  46 F,  4611 ,  46 K of the vehicle-mounted control unit  46  and the like in the mutually communicable manner via the CAN. 
     In the case where a standby condition to cause the riding mower V 4  to stand by at the evacuation standby position p 0  is satisfied, the standby position selection section  46 L executes standby position selection control to select the evacuation standby position p 0  that the riding mower V 4  can reach in the shortest time. 
     In this fourth embodiment, since the registered work site is the landing area A of the airport, the standby position selection section  46 L is set to determine that the standby condition is satisfied in the case where the standby position selection section  46 L receives an advance notification from a control tower at the time of takeoff and landing of the aircraft at the airport. 
     A description will hereinafter be made on the standby position selection control by the standby position selection section  46 L in the vegetated area  91  illustrated in  FIGS. 23 to 26  with reference to a flowchart in  FIG. 27 . 
     When the standby condition is satisfied, the standby position selection section  46 L performs the information acquisition processing for acquiring the current position, the travel state, and the like of the riding mower V 4  at the time (step # 91 ). 
     The standby position selection section  46 L estimates plural evacuation paths to each of the evacuation standby positions p 0 , a travel mode of the riding mower V 4 , and the like according to the acquired information, and performs required time calculation processing for calculating a required time for the riding mower V 4  to reach each of the evacuation standby positions p 0  from the estimated evacuation paths, travel mode, and the like (step # 92 ). 
     The standby position selection section  46 L performs the standby position selection processing and evacuation information transmission processing (steps # 93  to  94 ). In the standby position selection processing, the evacuation standby position p 0  with the calculated required time being the shortest is selected as the current evacuation standby position p 0 . In the evacuation information transmission processing, together with the selected evacuation standby position p 0 , an evacuation path Pm 8  suited for movement to the evacuation standby position p 0 , the travel mode, and the like are transmitted as evacuation information to the automatic travel control section  46 F. Thereafter, the standby position selection section  46 L terminates the standby position selection control. 
     When receiving the evacuation information from the standby position selection section  46 L, the automatic travel control section  46 F determines that the standby condition to cause the riding mower V 4  to stand by at the evacuation standby position p 0  is satisfied. Then, the automatic travel control section  46 F executes evacuation movement control to cause the riding mower V 4  to travel automatically to the evacuation standby position p 0  and to stand by at the evacuation standby position p 0  according to the evacuation path Pm 8 , the travel mode, and the like included in the evacuation information from the standby position selection section  46 L. 
     More specifically, for example, as illustrated in  FIG. 24 , in the case where a current position of the riding mower V 4  at the time when the standby position selection section  46 L receives the advance notification from the above-described control tower is located closer to the evacuation standby position p 0  set on an end side of the target path P than to the evacuation standby position p 0  set on a start side of the target path P and where the travel state of the riding mower V 4  is a forward travel state toward the perimeter road  92 , the standby position selection section  46 L selects the evacuation standby position p 0  on the end side as the current evacuation standby position p 0 , and transmits, as the evacuation information, the evacuation standby position p 0  on the end side, the shortest evacuation path Pm 8  from the current position of the riding mower V 4  to the evacuation standby position p 0  on the end side, the forward travel, and the like to the automatic travel control section  46 F. Then, based on the evacuation information from the standby position selection section  46 L, the automatic travel control section  46 F causes the riding mower V 4  to travel forward to the evacuation standby position p 0  on the end side along the evacuation path Pm 8 . 
     For example, as illustrated in  FIG. 25 , in the case where the current position of the riding mower V 4  at the time when the standby position selection section  46 L receives the advance notification from the above-described control tower is located closer to the evacuation standby position p 0  on the start side than to the above-described evacuation standby position p 0  on the end side and where the travel state of the riding mower V 4  is the forward travel state toward the perimeter road  92 , the standby position selection section  46 L selects the evacuation standby position p 0  on the start side as the current evacuation standby position p 0 , and transmits, as the evacuation information, the evacuation standby position p 0  on the start side, the shortest evacuation path Pm 8  from the current position of the riding mower V 4  to the evacuation standby position p 0  on the start side, the forward travel, and the like to the automatic travel control section  46 F. Then, based on the evacuation information from the standby position selection section  46 L, the automatic travel control section  46 F causes the riding mower V 4  to travel forward to the evacuation standby position p 0  on the start side along the evacuation path Pm 8 . 
     For example, as illustrated in  FIG. 26 , in the case where the current position of the riding mower V 4  at the time when the standby position selection section  46 L receives the advance notification from the above-described control tower is located closer to the evacuation standby position p 0  on the end side than to the above-described evacuation standby position p 0  on the start side and where the travel state of the riding mower V 4  is the forward travel state toward the runway  90 , the standby position selection section  46 L selects the evacuation standby position p 0  on the end side as the current evacuation standby position p 0 , and transmits, as the evacuation information, the evacuation standby position p 0  on the end side, the shortest evacuation path Pm 8  from the current position of the riding mower V 4  to the evacuation standby position p 0  on the end side, reverse travel, and the like to the automatic travel control section  46 F. Then, based on the evacuation information from the standby position selection section  46 L, the automatic travel control section  46 F causes the riding mower V 4  to travel reversely to the evacuation standby position p 0  on the end side along the evacuation path Pm 8 . 
     With the configuration that has been described so far, in this automatic travel system for a work vehicle, in the case where the standby condition to cause the riding mower V 4  to stand by at the evacuation standby position p 0  is satisfied, the standby position setting section  46 K executes the standby position selection control, and selects the optimal evacuation standby position p 0  at the time when the standby condition is satisfied (at the time of takeoff and landing of the aircraft). In this way, the user no longer has to select the optimal evacuation standby position p 0 , which varies from time to time, when the standby condition is satisfied. 
     In addition, the automatic travel control section  46 F executes the evacuation movement control on the basis of the evacuation information from the standby position setting section  46 K, moves the riding mower V 4  to the optimal evacuation standby position p 0  in the shortest time, and thereafter causes the riding mower V 4  to stand by at the evacuation standby position p 0 . In this way, the user no longer has to cause the riding mower V 4  to travel manually to the evacuation standby position p 0 . 
     In other words, the selection of the evacuation standby position p 0  in the landing area A of the airport and the movement of the riding mower V 4  to the evacuation standby position p 0  can be performed automatically and appropriately. Thus, the riding mower V 4  can move favorably to the evacuation standby position p 0  according to takeoff and landing of the aircraft while the burden on the user is reduced. 
     OTHER EMBODIMENTS 
     A description will be made on other embodiments of the present invention. Note that a configuration of each of the other embodiments described below can be applied not only independently but can also be applied in combination with the configuration of another embodiment. 
     (1) Other typical embodiments regarding the configuration of the work vehicle are as follows. For example, the work vehicle may be configured to have an electric specification that includes an electric motor instead of the engine  13 . For example, the work vehicle may be configured to have a hybrid specification that includes the engine  13  and the electric motor. 
     (2) The automatic travel system for a work vehicle exemplified in the first embodiment can be applied to, in addition to the tractor V 1  having the sowing specification, the work vehicles such as the tractor V 1  having a sowing and fertilizing specification in which a sowing and fertilizing work device  3  is coupled to the rear portion of the tractor V 1  via the three-point linkage mechanism  2 , the tractor V 1  having a fertilizing specification in which the fertilizing work device  3  is coupled to the rear portion of the tractor V 1  via the three-point linkage mechanism  2 , the riding rice transplanter V 2  exemplified in the second embodiment, the riding rice transplanter V 2  with a fertilizing function that includes the fertilizer application device in addition to the seedling planting device  3 , the riding rice transplanter V 2  with a chemical application function that includes the chemical spraying device in addition to the seedling planting device  3 . 
     (3) The automatic travel system for a work vehicle exemplified in the second embodiment can be applied to, in addition to the riding rice transplanter V 2 , the work vehicles such as the riding rice transplanter V 2  with the above-described fertilizing function, the riding rice transplanter V 2  with the chemical application function, the tractor V 1  with the sowing specification, the tractor V 1  having the sowing and fertilizing specification, and the tractor V 1  in a fertilizing specification. 
     (4) The automatic travel system for a work vehicle exemplified in the third embodiment can be applied to, in addition to the combine harvester V 3 , the work vehicle such as a harvester for harvesting corn or the like. 
     (5) The automatic travel system for a work vehicle exemplified in the fourth embodiment can be applied to, in addition to the riding mower V 4 , the work vehicles such as the tractor V 1 , the snowplow, and the wheel loader having a rotary cultivation specification, in each of which the rotary cultivator is coupled to the rear portion of the tractor V 1  via the three-point linkage mechanism  2 . 
     (6) In the automatic travel system for a work vehicle exemplified in the fourth embodiment, the standby position selection section  46 L may be configured to transmit, to the automatic travel control section  46 F, the evacuation path Pm 8  on which the work vehicle (the riding mower V 4 ) is moved to the evacuation standby position p 0  after termination of the work on the current work path P 1  in the case where there is a time margin to terminate the work on the work path P 1  before the work vehicle is moved from the current position to the evacuation standby position p 0 . 
     Additional Statements of the Invention 
     A first characteristic configuration of the present invention is in a point that the automatic travel system for a work vehicle includes: the automatic travel control section that causes the work vehicle to travel automatically along the target path at the registered work site by using the satellite positioning system; and a standby position setting section that sets the standby position of the work vehicle, in which the standby position setting section acquires the entry point at the time of entering the registered work site from outside the registered work site and sets the entry point as the standby position, and in which the automatic travel control section determines whether the standby condition to cause the work vehicle to stand by at the standby position is satisfied and, in the case where the standby condition is satisfied, causes the work vehicle to travel automatically from the current position to the standby position and to stand by at the standby position. 
     With such a configuration, in the case where the user causes the work vehicle to travel manually toward the registered work site, the standby position setting section acquires the entry point of the work vehicle to the registered work site, and sets this entry point as the standby position. In this way, the user no longer has to set the standby position per registered work site where the work is performed. 
     For example, in the case where the registered work site is the field, the entry point, which is set as the standby position, is the entrance/exit to/from the registered field that connects the registered field to the farm road or the like outside the field. For example, in the case where the registered work site is the landing area at the airport, the entry point, which is set as the standby position, is the entrance/exit to/from the registered landing area that connects the registered landing area to the perimeter road or the like outside the registered landing area. 
     In this way, for example, in the case where the work vehicle is the riding rice transplanter that plants the seedlings in the field or the riding fertilizer application machine that supplies the fertilizer to the field, the entrance/exit (entry point), which connects the field to the farm road or the like, where the carrier vehicle or the like loaded with the agricultural materials such as the replenishment seedlings or fertilizer can be stopped, is set as the standby position of the work vehicle at the time of replenishing the agricultural materials to the work vehicle. In addition, in the case where the work vehicle is the harvester such as the combine harvester that harvests crops such as rice or soybeans in the field, the entrance/exit (entry point) that connects the field to the farm road or the like where the carrier vehicle or the like, to which the harvested crops are transferred, can be stopped is set as the standby position of the work vehicle at the time of transferring the crops from the work vehicle to the carrier vehicle or the like. In this way, it is possible to easily replenish the agricultural materials, to easily transfer the crops from the work vehicle to the carrier vehicle or the like, and the like. 
     Meanwhile, in the case where the work vehicle is the mower or the like that mows grass in the vegetated area around the runway in the landing area at the airport, the entrance/exit (entry point) that connects the landing area to the perimeter road or the like outside the landing area is set as the standby position of the work vehicle at the time of evacuating the work vehicle during takeoff and landing of the aircraft. In this way, it is possible to evacuate the work vehicle to a position away from the runway during takeoff and landing of the aircraft. 
     In the case where, as the standby condition to cause the work vehicle to stand by at the standby position, for example, a shortage of the remaining amount of the agricultural materials, excess storage of the crops, or the like in the work vehicle is set, upon satisfaction of any of these conditions, the work vehicle travels automatically from the current position to the standby position for replenishing the materials or transferring the crops, and stands by at the standby position. Meanwhile, in the case where, as the standby condition to cause the work vehicle to stand by at the standby position, for example, the reception of the advance notification from the control tower at the time when the aircraft is taking off or landing at the airport, or the like is set, upon satisfaction of this condition, the work vehicle travels automatically from the current position to the evacuation standby position, and stands by at the standby position. In this way, the user no longer has to cause the work vehicle to travel manually from the current position to the standby position. 
     In other words, it is possible to set the standby position suitable for a reason for standby of the work vehicle, a work situation, and the like while reducing the burden on the user. In addition, when the standby condition is satisfied, the work vehicle can travel automatically to the appropriate standby position. In the case where the work vehicle is an agricultural work machine such as the riding rice transplanter or the combine harvester, it is possible to efficiently perform the work such as the replenishment of the materials to the work vehicle or the transfer of the crops from the work vehicle at the standby position. In the case where the work vehicle is the mower that works the landing area at the airport, the work in the landing area can be performed favorably without interfering with takeoff and landing of the aircraft. 
     A second characteristic configuration of the present invention is in a point that the automatic travel control section that causes the work vehicle to travel automatically along the target path at the registered work site by using the satellite positioning system and the standby position setting section that sets the standby position of the work vehicle are provided, the standby position setting section sets the intersection point of the extension line of the work path included in the target path with the outline of the registered work site as the standby position, and the automatic travel control section determines whether the standby condition to cause the work vehicle to stand by at the standby position is satisfied and, in the case where the standby condition is satisfied, causes the work vehicle to travel automatically from the current position to the standby position and to stand by at the standby position. 
     With such a configuration, the standby position setting section acquires the above-described intersection point from the target path and the outline of the work site included in the registration information on the registered work site, and sets this intersection point as the standby position. In this way, the user no longer has to set the standby position per work site. 
     For example, in the case where the registered work site is the field, the intersection point of the extension line of the work path, which is included in the target path generated according to the work in the field, with the outline of the field as a boundary between the inside and the outside of the field is set as the standby position. In this way, it is possible to shorten the travel distance of the work vehicle from the current position to the standby position. 
     Furthermore, for example, in the case where the work vehicle is the agricultural work machine such as the riding rice transplanter or the combine harvester that works in the field, as the standby condition to cause the work vehicle to stand by at the standby position, the shortage of the remaining amount of the agricultural materials, the excess storage of the crops, or the like in the work vehicle is set. In such a case, upon satisfaction of any of these conditions, the work vehicle travels automatically from the current position to the standby position, which is the intersection point of the extension line of the currently traveled work path with the outline of the field, and stands by at the standby position. In this way, the user no longer has to cause the work vehicle to travel manually from the current position to the standby position. 
     In other words, it is possible to set the standby position suitable for the reason for the standby of the work vehicle, the work situation, and the like while reducing the burden on the user. In addition, when the standby condition is satisfied, the work vehicle can travel automatically to the appropriate standby position. In the case where the work vehicle is the agricultural work machine such as the riding rice transplanter or the combine harvester, it is possible to efficiently perform the work, such as the replenishment of the materials to the work vehicle or the transfer of the crops from the work vehicle, including the movement to the standby position. 
     A third characteristic configuration of the present invention is in a point that the specifying section is provided to specify, of plural outline identification lines identifying the outline of the registered work site, the outline identification line with which the standby position can be set. 
     With such a configuration, in regard to the outline identification line that is adjacent to the obstacle such as a ditch or a wall interfering with the movement of the work vehicle to the standby position, such an outline specific line that the obstacle such as the tree or an electric wire interfering with the replenishment of the materials to the work vehicle having moved to the standby position or the transfer of the crops from the work vehicle exists nearby, and the like, it is possible to prevent occurrence of such an inconvenience that the intersection point of any of those outline identification lines with the extension line of the work path is set as the standby position. 
     In other words, it is possible to avoid a possibility that the standby position unsuitable for the reason for the standby of the work vehicle, the work condition, or the like is set. As a result, it is possible to avoid the occurrence of such inconveniences that the work vehicle cannot travel automatically to the standby position even when the standby condition to cause the work vehicle to stand by at the standby position is satisfied and that it is difficult to replenish the materials to the work vehicle, transfer the crops from the work vehicle, or the like even when the work vehicle stands by at the standby position. 
     A fourth characteristic configuration of the present invention is in a point that the automatic travel control section that causes the work vehicle to travel automatically along the target path at the registered work site by using the satellite positioning system, the standby position setting section that sets the standby position of the work vehicle at the plural locations in the registered work site, the standby position selection section that selects the single standby position from the plural standby positions are provided, and the automatic travel control section determines whether the standby condition to cause the work vehicle to stand by at the standby position is satisfied and, in the case where the standby condition is satisfied, causes the work vehicle to travel automatically from the current position to the standby position selected by the standby position selection section and to stand by at the standby position. 
     With such a configuration, the standby position selection section can select, from the standby positions at the plural locations set by the standby position setting section, the single standby position that is suited for the current position of the work vehicle or the like at the time when the standby condition to cause the work vehicle to stand by at the standby position is satisfied. In this way, the user no longer has to select the standby position suited for the current position of the work vehicle or the like that varies from time to time when the above-described standby condition is satisfied. 
     In the case where, as the standby condition to cause the work vehicle to stand by at the standby position, for example, the shortage of the remaining amount of the agricultural materials, the excess storage of the crops, or the like in the work vehicle is set, upon satisfaction of any of these conditions, the work vehicle travels automatically from the current position to the selected standby position for replenishing the materials or transferring the crops, and stands by at the standby position. Meanwhile, in the case where, as the standby condition to cause the work vehicle to stand by at the standby position, for example, the reception of the advance notification from the control tower at the time when the aircraft is taking off or landing at the airport, or the like is set, upon satisfaction of this condition, the work vehicle travels automatically from the current position to the selected evacuation standby position, and stands by at the standby position. In this way, the user no longer has to cause the work vehicle to travel manually from the current position to the standby position. 
     In other words, it is possible to select the standby position suited for the work situation, such as the current position of the work vehicle, or the like which varies from time to time when the above-described standby condition is satisfied, while reducing the burden on the user. In addition, when the standby condition is satisfied, the work vehicle can travel automatically to the appropriate standby position. In the case where the work vehicle is the agricultural work machine such as the riding rice transplanter or the combine harvester, it is possible to efficiently perform the work such as the replenishment of the materials to the work vehicle or the transfer of the crops from the work vehicle at the standby position. In the case where the work vehicle is the mower that works the landing area at the airport, the work in the landing area can be performed favorably without interfering with takeoff and landing of the aircraft.