Abstract:
A system for coordinating the relative movements of an agricultural harvester ( 104 ) and a cart ( 108 ) by electronically estimating an unload position at which it the agricultural harvester ( 104 ) should be unloaded, and electronically calculating a path for the cart ( 108 ) to follow to arrive at that unload position.

Description:
FIELD 
       [0001]    This invention relates to agricultural harvesting. 
       BACKGROUND 
       [0002]    Traditional harvesting of crops involves an agricultural harvester traveling through the field severing the crop plants from the ground and storing the plants (or portions of the plant) in a storage structure part of the agricultural harvester. This storage structure is not large enough to carry an entire field&#39;s worth of harvested crop, and therefore must be emptied many times during the harvesting of every field. 
         [0003]    During harvesting, time is of the essence. For this reason, agricultural harvesters are operated continuously as they travel through the field, not stopping for unloading or to drive to an unloading location. 
         [0004]    A second vehicle travels alongside the agricultural harvester to receive crop from the storage structure even as the agricultural harvester is traveling through the field harvesting crop. Thus the second vehicle, often called a “cart”, matches speed and location with the always-moving agricultural harvester as the agricultural harvester unloads crop from the storage structure into the cart. 
         [0005]    Once the harvester is emptied, the cart leaves the side of the agricultural harvester and travels to an unloading location where it deposits the crop. It then returns to the side of the harvester to receive and ferry more crop to the unloading location. The process is repeated many times while a single field is harvested. 
         [0006]    It is not easy, even for an experienced cart operator, to predict where the agricultural harvester will be when it next needs to be unloaded and to drive there just in time to unload the agricultural harvester. In one common practice the driver of the agricultural harvester and the driver of the cart are in radio contact, each informing the other of their anticipated locations in an attempt to synchronize the operation of their vehicles. 
         [0007]    One common outcome is a too-early arrival of the cart at the agricultural harvester. The cart rushes to the side of the agricultural harvester, travels alongside for a distance and then is ready when the agricultural harvester needs unloading. This is inefficient. If the unloading location was known with accuracy, the cart could simply move to that location at a more efficient speed to arrive just as the unloading became necessary, thereby saving fuel for the cart. 
         [0008]    Another outcome is a too-late arrival. The harvester fills up and no cart is present. The harvester then stops harvesting and waits stationary in the field until the cart arrives and unloading begins. This is an inefficient use of the agricultural harvester, delays harvesting and consumes unnecessary time and fuel during the wait. 
         [0009]    What is needed is a better system for synchronizing the operation of the agricultural harvester and cart during unloading operations. It is an object of this invention to provide such a system. 
       SUMMARY 
       [0010]    In accordance with one aspect, a system for coordinating the movements of an agricultural harvester and a cart by electronically estimating an unload position at which it the agricultural harvester should be unloaded, and electronically calculating a path for the cart to follow to arrive at that unload position. 
         [0011]    In accordance with another aspect, lowercase system for coordinating the movements of an includes a first electronic control circuit on an agricultural harvester that is configured to receive status signals from sensors indicative of a physical status of the agricultural harvester, a first radio navigation receiver coupled to the first electronic control circuit, wherein the radio navigation receiver is configured to receive radio navigation signals and to provide a first location signal indicative of a current location of the agricultural harvester to the first electronic control circuit, a first radio transmitter/receiver coupled to the first electronic control circuit, wherein the first radio transmitter/receiver is configured to transmit first status data of the agricultural harvester, a second electronic control circuit on a cart configured to receive signals from sensors indicative of a physical status of the cart, and a second radio transmitter/receiver coupled to the second electronic control circuit, wherein the second radio transmitter/receiver is configured to receive the first status data from the first radio transmitter/receiver, wherein the second electronic control circuit is configured to calculate a path to be followed by the cart. 
         [0012]    The first status data may be derived from the first location signal. 
         [0013]    The first status data may include a location of the agricultural harvester. 
         [0014]    The first status data may include a predicted location of the agricultural harvester, wherein the predicted location is generated by the first electronic control circuit. 
         [0015]    The first radio transmitter/receiver may be configured to sequentially transmit each of a plurality of first status data while the cart is traveling from an unload location to the agricultural harvester, the second radio transmitter/receiver maybe configured to sequentially receive each of said plurality of first status and to sequentially provide each of said plurality of first status data to the second electronic control circuit, and the second electronic control circuit maybe configured to calculate a new path for the cart to follow upon receipt of each of said plurality of first status data. 
         [0016]    Each of a plurality of first status data may comprise sensor data at least indicative of an amount of crop in a storage structure of said agricultural harvester. 
         [0017]    Each of a plurality of first status data may comprise data at least indicative of an actual position of said agricultural harvester in said field. 
         [0018]    The first electronic control circuit may be configured to sequentially calculate a series of unload locations of said agricultural harvester and each of a plurality of first status data comprises data may be indicative of each location of said series of unload locations. 
         [0019]    The first electric chronic control circuit may be configured to sequentially calculate the series of unload locations at the same time as said cart is traveling toward said agricultural harvester. 
         [0020]    The second electronic control circuit may be configured to calculate new driving directions for the operator in order to maintain the cart on said new path. 
         [0021]    The second electronic control circuit may be configured to display the new driving directions on a visual display. 
         [0022]    The second electronic control circuit may be configured to predict a new unload location of the agricultural harvester in response to receiving each of said plurality of first status data from the second radio transmitter/receiver. 
         [0023]    The system may further comprise a steering actuator coupled to the second electronic control circuit and configured to steer the cart. 
         [0024]    The second electronic control circuit may be configured to steer the cart along the path calculated by the second electronic control circuit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a plan view of an agricultural field showing an agricultural harvester and cart. 
           [0026]      FIG. 2  illustrates an electronic control system and sensors for the agricultural harvester. 
           [0027]      FIG. 3  illustrates an electronic control system for the cart. 
           [0028]      FIG. 4  illustrates a flow chart of the system operation. 
           [0029]      FIG. 5  illustrates another flowchart of the system operation. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    In  FIG. 1 , a plan view of an agricultural field  100  is shown. Crop plants  102  are growing in the field. They&#39;re being harvested by an agricultural harvester  104 . The agricultural harvester  104  follows a path  106  through the field. Once the agricultural harvester  104  has passed over a region of the field  100 , and the field  100  is harvested, it becomes available for travel by a cart  108 . The cart  108  cannot travel through regions of the field  100  that are not yet harvested, since travel by the cart  108  through the field  100  would destroy the crop plants  102  in the as yet unharvested regions of the field  100 . 
         [0031]    The cart  108  travels between the agricultural harvester  104  and a grain storage area  110 , here shown as a grain truck. Alternatively, the grain storage area can be as simple as a pile on the ground, a stationary structure having walls such as a silo, tank, or bin, or movable structure, such as a cart, bin, wagon, or truck. 
         [0032]    When the cart  108  arrives at the grain storage area, it unloads the crop that has accumulated from the agricultural harvester  104  and returns again to the agricultural harvester  104  to receive another load of crop. 
         [0033]    To reach the agricultural harvester  104 , the cart  108  must traverse the field, avoiding various natural hazards, such as standing water  112 , or other barriers, such as trees  114 , or even manmade barrier to such as fence lines  116 , to the free movement of the cart  108 , until it arrives at the agricultural harvester  104 . 
         [0034]    Unharvested regions  118  of the agricultural field  100  also constitute barriers. They are not constant barriers during harvesting, since they will eventually be harvested by the agricultural harvester  104 , but nonetheless the cart  108  cannot travel through the unharvested regions  118  since such travel would destroy crops. 
         [0035]    A typical agricultural harvester  104  is illustrated herein which comprises an agricultural harvesting vehicle  120 . The harvester also comprises an agricultural harvesting head  122  fixed to the front of the agricultural harvesting vehicle  120  to sever the crop plants from the ground and send them to the agricultural harvesting vehicle  120 . A storage structure  124  is coupled to the agricultural harvesting vehicle  120  to store at least a portion of the severed crop plants. Other portions of the severed crop plants may be stored in a separate storage structure or spread upon the ground. 
         [0036]    In  FIG. 2 , a first configuration of electronic control circuit  200  and associated sensors  202  for agricultural harvester  104  is illustrated. Electronic control circuit  200  includes an ECU  204  that further comprises a digital microprocessor  208 , a digital working memory (RAM)  210 , and a digital static memory (ROM)  212 . Driver circuits  214  are also provided that couple external devices such as sensors, other ECUs, and the equipment to be driven such as valves and actuators to electronic control circuit  200 . In  FIG. 2 , the arrangement is shown with a single ECU  204 . 
         [0037]    Alternatively, the system may be arranged such that the functions described herein for the various components in  FIG. 2  can be provided by multiple ECUs  204  coupled together using radio signals, serial or parallel communication buses. The term “ECU” therefore is defined to encompass a single ECU, or a plurality of ECUs on the agricultural harvester  104  that are coupled together using radio signals, serial, or parallel communication buses. 
         [0038]    ECU  204  is coupled to a radio navigation receiver  220  to receive signals indicative of a location of the radio navigation receiver  220 , and therefore also indicative of the location of the agricultural harvester  104  upon which the radio navigation receiver  220  is located. The radio navigation receiver  220  may be a GPS, Loran, GLONASS, or other radio navigation receiver currently existing or to be developed in the future. 
         [0039]    ECU  204  is also coupled to an operator input device  222  which is provided to permit the operator to interact with and otherwise issue commands to the electronic control circuit  200 . 
         [0040]    ECU  204  is also coupled to a visual display  224 , which is provided to permit the electronic control circuit  200  to communicate to the operator. The visual display  224  can be a CRT, an LCD display, a plasma display, or other display configured to generate visual indicia. 
         [0041]    In addition, ECU  204  is also coupled to an annunciator  226  which is provided to permit the electronic control circuit  200  to communicate to the operator using sound. The annunciator can be a horn, a speaker, or other sound generating device. 
         [0042]    ECU  204  is coupled to a yield monitor  228 . Yield monitor  228  is configured to sense the amount of crop being harvested by the agricultural harvester  104 . Yield monitor  228  generates a signal indicative of the rate at which crop is being harvested by the agricultural vehicle  104 . 
         [0043]    ECU  204  is coupled to a speed sensor  230 . Speed sensor  230  is configured to sense the speed of the agricultural harvester  104  and to generate a signal indicative of the speed of the agricultural vehicle  104 . 
         [0044]    ECU  204  is coupled to a bin sensor  232 . Bin sensor  232  is configured to sense the quantity of accumulated crop in the storage structure  124  ( FIG. 1 ) in which the agricultural harvester  104  stores the crop it harvests. As just one example, if the agricultural harvester  104  is a combine harvester this structure would be the grain tank or reservoir, and the bin sensor  232  would indicate the level of grain in the grain tank a reservoir. 
         [0045]    ECU  204  is coupled to a radio transmitter/receiver  234 . Radio transmitter/receiver  234  is provided to permit electronic control circuit  200  to transmit data regarding the status of the agricultural harvester  104 , such as the location of the agricultural harvester  104 , the previous path of agricultural harvester  104 , the projected path of the agricultural harvester  104 , the projected location of the agricultural harvester  104  when the level of crop in the storage structure  124  reaches a predetermined level, for example. 
         [0046]    In  FIG. 3  a first configuration of electronic control circuit  300  and associated sensors for cart  108  is illustrated. Electronic control circuit  300  includes an ECU  304  that further comprises a digital microprocessor  308 , a digital working memory (RAM)  310 , and a digital static memory (ROM)  312 . In addition are driver circuits  314  that are configured to couple to external devices such as sensors, other ECUs, and the equipment to be driven such as valves and actuators. In  FIG. 3 , the arrangement is shown with a single ECU  304 . 
         [0047]    Alternatively, the system may be arranged such that the functions described herein for the various components in  FIG. 3  can be provided by multiple ECUs  304  coupled together using radio signals, serial or parallel communication buses. The term “ECU” therefore is defined to encompass a single ECU, or a plurality of ECUs on the cart  108  that are coupled together using radio signals, serial, or parallel communication buses. 
         [0048]    ECU  304  is coupled to a radio navigation receiver  320  to receive signals indicative of a location of the radio navigation receiver  320 , and therefore also indicative of the location of the cart  108  upon which the radio navigation receiver  320  is located. The radio navigation receiver  320  may be a GPS, Loran, GLONASS, or other radio navigation receiver currently existing or to be developed in the future. 
         [0049]    ECU  304  is also coupled to an operator input device  322  which is provided to permit the operator to interact with and otherwise issue commands to the electronic control circuit  300 . 
         [0050]    ECU  304  is also coupled to a visual display  324 , which is provided to permit the electronic control circuit  302  communicate to the operator. The visual display  324  can be a CRT, an LCD display, a plasma display, or other device capable of generating visual indicia for the operator. 
         [0051]    In addition, ECU  304  is also coupled to an annunciator  326  which is provided to permit the electronic control circuit  300  to communicate to the operator using sound. The annunciator can be a horn, a speaker, or other sound generating device. 
         [0052]    ECU  304  is coupled to a speed sensor  330 . Speed sensor  330  is configured to sense the speed of the cart  108  and to generate a signal indicative of the speed of the cart  108 . 
         [0053]    ECU  304  is coupled to a radio transmitter/receiver  334 . Radio transmitter/receiver  334  is provided to permit electronic control circuit  300  to receive data regarding the status of the agricultural harvester  104 , such as the location of the agricultural harvester  104 , the previous path of agricultural harvester  104 , the projected path of the agricultural harvester  104 , the projected location of the agricultural harvester  104  when the level of crop in storage structure  124  reaches a predetermined level, for example. 
         [0054]    ECU  304  is also coupled to a steering actuator  350  that is, in turn, coupled to the wheels of the cart  108  to steer the cart  108  as it travels through the field. In one operating mode, ECU  304  is configured to control the steering actuator  350  as the cart  108  is driven through the agricultural field  100  to steer the cart through the field, and to ensure that the cart arrives at a projected unloading location in the agricultural field for agricultural harvester  104 . In another operating mode, ECU  304  provides driving directions to the operator on visual display  324  and the driver steers the cart  108 . 
         [0055]      FIG. 4  is a flow chart of a first mode of operation of the navigation system. In step  400 , the process starts. 
         [0056]    In step  402 , the electronic control circuit  200  reads the yield monitor and determines the time rate of fill of the storage structure  124 . 
         [0057]    In step  404 , the electronic control circuit  200  reads the bin sensor and determines the level of the crop (i.e. the fill level) in storage structure  124 . 
         [0058]    In step  406 , the electronic control circuit reads the speed sensor  230  to determine the field speed (i.e. the time rate of vehicle travel through the agricultural field) of the agricultural harvester  104 . 
         [0059]    In step  408 , the electronic control circuit  200  reads the radio navigation receiver  320  and determines the position of the agricultural harvester  104  in the field  100 . 
         [0060]    In step  410 , the electronic control circuit  200  combines the foregoing information together with the width of the agricultural harvesting head extending across the front of the agricultural harvester  104  in order and predicts the future path of the agricultural harvester  104  in the field  100 . The width of the agricultural harvesting head defines the maximum width of the swathe of crop that is harvested with each pass of the agricultural harvester  104 . The width of the swathe defines the distance between adjacent segments of path  106  that are followed by agricultural harvester  104  as it travels through the field  100 . 
         [0061]    This calculation is performed using data previously stored in the memory circuits of electronic control circuit  200 , in particular electronic models of the agricultural field showing the extent of the field, the path previously followed by the agricultural harvester  104  (and therefore that portion of the field  100  which has already been harvested and therefore will not beat reversed by the agricultural harvester  104  again), the remaining portion and the field that is currently unharvested (and therefore needs to be traversed by agricultural harvester  104 ). These models are continually updated as the agricultural harvester  104  travels through the field harvesting crop. Using this information, and the width of the harvesting head (which is stored in one of the memory circuits of electronic control circuit  200 ) agricultural harvester  104  can determine the path it will follow through the field in order to completely harvest the crop. 
         [0062]    Examples of path planning algorithms to provide complete coverage of an area are described in Jin, J, Ting, L., Optimal Coverage Path Planning for Arable Farming in 2D Surfaces, ASABE 53(1) 283-295, 2010; Spekken, M., Bruin, S., Optimizing Routes on Agricultural Fields Minimizing Maneuvering and Servicing Time, Precision Agriculture, 411-425, 2011; Ali, O, Verlinden B., Van Oudheusden, Infield Logistics Planning for Crop-Harvesting Operations, Engineering Optimization, Vol. 41., No. 2, pp 183-197, February 2009; and Bochtis, D., Vougioukas, S., Tsatsarelis, C., Ampatzidis, Y., Field Operation Planning for Agricultural Vehicles: A Hierarchical Modeling Framework, Agricultural Engineering International; the CIGR Ejournal, Manuscript PM 06 021, Vol. IX, February 2007, all of which references are incorporated herein by reference for all that they teach. 
         [0063]    In step  412 , the electronic control circuit  200  estimates the position along the predicted path at which the storage structure  124  will be filled to a predetermined level at which it should be unloaded. 
         [0064]    To do this, electronic control circuit  200  combines data indicating the rate at which new crop is being poured into the storage structure  124  (provided by the yield monitor  228 ), data indicating the current level of crop in the storage structure  124  (provided by the bin sensor  232 ), and the speed of the agricultural harvester  104  through the field (provided by the speed sensor  230 ), and based upon these measurements, determines how much farther along the calculated path the agricultural harvester  104  will travel until the storage structure  124  is filled to its unloading level. 
         [0065]    In step  414 , electronic control circuit  200  transmits the position it determined in the foregoing steps (the unloading location) to the cart  108  using the radio transmitter/receiver  234 . 
         [0066]    In step  416 , the electronic control circuit  300  of cart  108  receives the unloading location transmitted by the agricultural harvester  104 . 
         [0067]    In step  418 , the electronic control circuit  300  calculates a path to the unloading location. Typical path planning algorithms acceptable for this task can be found in Dantzig, G. B. and Ramser, J. H., (1959) “the Truck Dispatching Problem”, Management Science, Vol. 6, No. 1, pp. 80-91; Braysay, O., (2003): “A reactive variable neighborhood search for the vehicle routing problem with time windows”, INFORMS Journal Computing, Vol. 15, pp. 347-368; and Bodin, L. D., (1990), “Twenty years of routing and scheduling”, Operations Research, Vol. 38, pp. 571-579, all of which are incorporated herein by reference for all that they teach. 
         [0068]    The electronic control circuit  300  uses the location of the cart  108  provided by radio navigation receiver  320  and the speed of the cart  108  provided by the speed sensor  330  to determine a preferred path to be followed by the cart  108  to the unloading location. 
         [0069]    In step  420 , the electronic control circuit  300  generates driving directions that indicate how the operator of the cart  108  should follow the preferred path calculated in step  418  and shows these driving directions to the operator of the cart  108  on visual display  324 . 
         [0070]    These driving directions indicate to the operator of the cart  108  the direction in which to steer the cart  108 . These driving directions are turn-by-turn driving directions indicating where and how much the operator should turn the cart  108 . When the operator of the cart  108  follows these driving directions, the operator will arrive at the unloading location at a time that coincides with the arrival of the agricultural harvester  104 . 
         [0071]    In one embodiment of the invention, the electronic control circuit  300  generates the driving directions and displays the turn by turn driving directions to the operator. As long as the operator follows those driving directions he will arrive on time that the unloading location. 
         [0072]    In an alternative embodiment, the electronic control circuit  300  loops through steps  418  and  420  at intervals during the time the operator drives the cart  108  to the unloading location of the agricultural harvester  104 . Each time electronic control circuit  300  executes this loop, the electronic control circuit  300  recalculates the driving directions it provides to the operator, using the position of the cart  108  provided by radio navigation receiver  320  as the revised starting point each time it iterates steps  418  and  420 . 
         [0073]    This recalculation of the preferred path and the driving directions accommodates operator error produced by the operator when the operator does not exactly follow the directions of electronic control circuit  300  as the operator drives through the field. Since the operator may not follow the exact driving directions, and therefore is not at the optimum position at every point in the field it would be beneficial to provide updated driving directions, preferably including changed turn-by-turn driving directions that will return the cart  108  to an optimum course for on-time arrival at the unloading location. 
         [0074]    The driving directions provided to the operator by electronic control circuit  300  may also include speed directions indicating the speed at which the operator should travel as he follows the turn-by-turn driving directions. The speed directions are calculated by electronic control circuit  300  such that if the speed directions are followed accurately, the cart  108  will arrive that the unloading location at the same time as the agricultural harvester  104 . The speed directions would also be recalculated in the alternative embodiment discussed above. Thus, in the alternative embodiment, the electronic control circuit  300 , looping periodically through steps  418  and  420  as it travels to the agricultural harvester  104  provides revised turn-by-turn driving directions as well as revised speed directions. 
         [0075]    In the embodiment of  FIG. 4  described above, the agricultural harvester  104  monitors various sensors on the vehicle and, based upon the values provided by those sensors, calculates an unloading location, which it then transmits to the cart  108 . 
         [0076]    Depending upon the bandwidth of the radio communications between the agricultural harvester  104  and the cart  108 , this process of navigation can be improved by the electronic control circuit  200  repeatedly calculating an unloading location for the agricultural harvester  104  as electronic control circuit  200  receives revised information from its associated sensors. 
         [0077]    The unloading location is a prediction of the field location of the agricultural harvester  104  when the amount of crop in the storage structure  124  reaches a predetermined level. It is therefore based upon a prediction of how much the agricultural harvester  104  will harvest. 
         [0078]    It may be, however, that having calculated an initial unloading location and transmitted that initial unloading location to the cart  108  (in step  414 ), that the agricultural harvester  104  harvests less or more grain than it had earlier anticipated and upon which it had earlier based its calculation of the initial unloading location which it previously transmitted to the electronic control circuit  301  on the cart  108  in step  414 . 
         [0079]    Better performance is provided by electronic control circuit  200  in an alternative arrangement by electronic control circuit  200  periodically looping through steps  402 - 412  as the agricultural harvester  104  travels through the field, continually revising its unloading location as it receives more grain and gets closer to the ultimate unloading location. 
         [0080]    By looping through steps  402 - 412 , the electronic control circuit  200  provides a succession of revised estimated unloading locations each of these estimated unloading locations being more accurate than the previous estimated unloading locations as the agricultural harvester  104  gathers more grain. 
         [0081]    It would be beneficial to provide these revised estimated unloading locations at periodic intervals to electronic control circuit  300  on cart  108  and for electronic control circuit  300  to recalculate the path it should travel to the agricultural harvester  104  based upon these revised estimated unloading locations. In order to do this, the electronic control circuit  300  of the cart  108  is configured in another mode of operation to receive and to use the new revised estimated unloading locations as each is a periodically transmitted by electronic control circuit  200  and to periodically recalculate the turn-by-turn driving directions (and speed directions, if any) that the electronic control circuit  300  provides to the operator on visual display  324  by when electronic control circuit  300  loops through steps  416 - 420 . 
         [0082]    In the examples above, the agricultural harvester  104  includes an electronic control circuit  200  that monitors various sensors and calculates an estimated unloading location of the agricultural harvester  104 . This arrangement requires a substantial computing capacity of the agricultural harvester  104 . Some agricultural harvesters  104  may not have this computing capacity. Instead, they may only be able to gather sensor data and transmit that sensor data. 
         [0083]    For this reason, an alternative embodiment of the process is provided in  FIG. 5 , in which the agricultural harvester  104  does not calculate the unloading location and transmit that information to the cart  108 . Instead, the cart  108  receives the appropriate sensor data from the agricultural harvester  104  in steps  402  through  408 , skips the steps of  410  and  412 , and in step  414  transmits not the unloading position of the agricultural harvester  104  but the sensor data that the agricultural harvester  104  gathered. This sensor data is received by electronic control circuit  300 , which in turn predicts the path of the agricultural harvester  104  in step  410  and estimates the future position of agricultural harvester  104  in step  412 . 
         [0084]    The process is the same as that illustrated in  FIG. 4 . With the exception that the steps of predicting the path in estimating the future position are performed by the electronic control circuit  300  instead of the electronic control circuit  200 . 
         [0085]    In step  502 , the electronic control circuit  200  reads the yield monitor  228 , the speed sensor  230 , the bin sensor  232 , and the radio navigation receiver  220 . 
         [0086]    In step  504 , the electronic control circuit  200  calculates the position of the agricultural harvester  104  based upon the signal from the radio navigation receiver  220 . 
         [0087]    In step  506 , the electronic control circuit  200  transmits the sensor data and the location of the agricultural harvester  104  using its radio transmitter/receiver  234 . 
         [0088]    In step  508 , the electronic control circuit  300  receives the sensor data and the location of agricultural harvester  104  using its radio transmitter/receiver  334 . 
         [0089]    In step  510 , the electronic control circuit  300  combines the information it received from agricultural harvester  104  (including harvesting head width) in order to predict the future path of the agricultural harvester  104  in the field  100 . This path prediction is performed in the same manner as it is performed in the example of  FIG. 4 , above. 
         [0090]    In step  512 , electronic control circuit  300  estimates the unloading location, the position all along the predicted path of agricultural harvester  104  at which the storage structure  124  will be filled to the unloading level. This unloading location is calculated identically to the way described above in conjunction with  FIG. 4 . 
         [0091]    In step  514 , the electronic control circuit  300  calculates a path to the unloading location. This path is calculated identically to the way described above in conjunction with  FIG. 4 . 
         [0092]    In step  516 , the electronic control circuit  300  generates driving directions for the operator of the cart  108  to drive the cart to the unloading location. These driving directions are calculated in the same manner as described above in conjunction with  FIG. 4 . 
         [0093]    Just as in the example of  FIG. 4 , in an alternative mode of operation electronic control circuit  300  is configured to periodically and automatically recalculate the driving directions it displays on visual display  224  to accommodate the changing position of the vehicle and any operator error as the operator drives the cart  108  toward the estimated unloading location of agricultural harvester  104 . 
         [0094]    Just as in the example of  FIG. 4 , in an alternative mode of operation, electronic control circuit  200  is configured to periodically perform the steps  502 ,  504 ,  506  while the operator is driving the cart  108  toward the agricultural harvester  104 . In this manner, the electronic control circuit  300  of the cart  108  is provided with updated information regarding the status of agricultural harvester  104  as it is traveling tour the agricultural harvester  104 . In this embodiment, the electronic control circuit  300  of the cart  108  is configured to not only periodically we calculate the driving directions to the agricultural harvester  104  in view of operator error, but also to recalculate the unloading location of agricultural harvester  104  in the field  100  as the operator is driving the cart  108  to the agricultural harvester  104  for unloading. 
         [0095]    In another alternative embodiment, the process of estimating the unloading location is based on a historical yield in the field. In any of the examples above regarding the calculation of the unloading location, whether it is performed by the electronic control circuit  200  or electronic control circuit  300 , the calculation can be performed by referring to historical yield data. 
         [0096]    When calculating the unloading location by referring to historical yield data, the electronic control circuit ( 200  or  300 ) determines the location of the agricultural harvester  104 , determines the remaining capacity of the storage structure  124  based upon a signal from the bin sensor  232 , and refers to historical yield data for the field to determine how much farther the agricultural harvester  104  can travel along its predicted path before the storage structure  124  reaches its predetermined fill level, and must be unloaded. 
         [0097]    In one arrangement, a single value of yield-per-acre may be provided for the entire field and stored in electronic memory of the electronic control circuit performing the calculation. If this single valued yield-per-acre algorithm is used by the electronic control circuit, the distance to the unloading location from the current location can be determined by simple algebra: the additional volume of crop necessary to fill the storage structure  124  is converted to a linear distance traveled by calculating the surface area of the field (the acreage) necessary to fill the storage structure  124 , and then dividing that by the width of the harvesting head. The resulting figure is equal to the linear distance traveled along the path to reach the unloading location. These calculations are performed by whichever electronic control circuit ( 200  or  300 ) is described above as performing the step of calculating the unloading location. 
         [0098]    In another alternative embodiment, a single value for the agricultural field is not used. Instead, a two dimensional yield map is provided and stored inside the electronic control circuit ( 200  or  300 ) described above. The yield-per-acre is determined by using a succession of locations of the agricultural harvester as it travels along its predicted path to look up corresponding yield values in the yield map. This provides a more accurate estimation of the yield, but requires additional calculations. 
         [0099]    These two methods of using historical yield values (i.e. either a single value for the entire field or multiple values expressed in the yield map as a function of field location) can either replace or be combined with the signal from the yield monitor  228 . For example, if the actual yield through the field is larger than the historical yield a variety of locations within the field, then a ratio of the average actual yield over the average historical yield can be multiplied by each of the historical yield values in the yield map. These modified yield map values can then be used instead of the raw yield map values to calculate the unloading location of the agricultural harvester  104 . 
         [0100]    In another alternative embodiment, instead of (or in addition to) providing turn-by-turn driving directions and/or speed directions to the operator of the cart  108 , as described above in conjunction with  FIGS. 4 and 5  or any of the alternative embodiments also described above, electronic control circuit  300  can be configured to calculate the path of the cart  108  to the agricultural harvester  104 , and to automatically signal the steering actuator  350  to drive the steering mechanism  352  to steer the cart  108  on to the proper path. This alternative embodiment is applicable to any of the above embodiments are alternates described in which the turn-by-turn driving directions or speed directions are provided to the operator. 
         [0101]    In all the embodiments above, radio communication between radio transmitter/receiver  234  and radio transmitter/receiver  334  has been described as transmitting information from the agricultural harvester  104  to the cart  108 . The types of radio communication may include long range radio telecommunications such as satellite telecommunications (e.g. Globalstar, Iridium, Orbcomm, Inmarsat, Thuraya) intermediate range radio telecommunications such as cell phones, and short range radio telecommunications such as Bluetooth, WIFI, MIFI, or any successor long range, intermediate range, or short range radio telecommunications.