Abstract:
The entire right, title and interest in and to this application and all subject matter disclosed and/or claimed therein, including any and all divisions, continuations, reissues, etc., thereof are, effective as of the date of execution of this application, assigned, transferred, sold and set over by the applicant(s) named herein to Deere &amp; Company, a Delaware corporation having offices at Moline, Ill. 61265, U.S.A., together with all rights to file, and to claim priorities in connection with, corresponding patent applications in any and all foreign countries in the name of Deere &amp; Company or otherwise.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates generally to a system for determining the relative position of a second farm vehicle in relation to a first farm vehicle, wherein the first vehicle and the second vehicle are equipped to perform jointly an operation on a field that is to be cultivated. The first vehicle contains a first satellite-supported position sensing device equipped to receive signals from several satellites and to provide position data of the first vehicle. The second vehicle contains a second satellite-support position sensing device equipped to receive signals from several satellites and to make position data of the second vehicle available. A data transmission connection exists between the first vehicle and the second vehicle, and the position data of the first vehicle can be transmitted to a computer of the second vehicle or vice versa. The computer provides data with respect to the relative position of the second vehicle relative to the first vehicle based on the position data of the first vehicle and the position data of the second vehicle.  
       BACKGROUND OF THE INVENTION  
       [0002]     In the past it has been frequently suggested to have two farm vehicles travel on parallel paths, wherein the first vehicle (master) is steered by an operator or automatically and the second vehicle (slave) is automatically kept on a track of travel parallel next to or behind the first vehicle. Both vehicles can perform a cultivation operation or the second vehicle can serve as the transport vehicle for the crop harvested by the first vehicle. By way of example reference is made to the following publications: “Elektronik als Hofknecht (Electronics used as Court Servants)”, Landtechnik 3/2000, pgs. 256 f; G. Wallmann and H.-H. Harms, “Assistenzsystem zur Oberladung landwirtschaftlicher Guter (Support System for transferring agricultural goods)”, Landtechnik 6/2002, pgs. 352 f; DE 197 05 842 A, DE 100 57 374 A, DE 100 64 860 A, DE 100 64 862 A, DE 102 24 939 A, EP 956 522 B, and JP 04 101 206 A.  
         [0003]     At least two types of transmission have been suggested for transmitting steering information from the first to the second vehicle. On one hand, steering data in the form of speed and directional data can be transmitted from the first vehicle to the second vehicle (see DE 100 64 860 A and JP 04 101 206 A), but this type has the disadvantage that possible errors in the directional and speed specifications to the second vehicle add up over time to large errors in the position information so that parallel travel is not always guaranteed.  
         [0004]     On the other hand, it is possible (see Wallmann, loc. cit., DE 100 64 862 A, DE 102 24 939 A and EP 956 522 B) to equip both vehicles with a satellite-supported position capturing system, especially with GPS receivers, and establish a data transmission connection between the two vehicles. In this type, the first vehicle informs the second vehicle of the respective position of the first vehicle. Based on that data and the output of the position capturing system of the second vehicle, the relative position is calculated by forming the difference between the two absolute positions based on which a steering and/or speed signal is generated for the second vehicle.  
         [0005]     Satellite-supported position capturing systems such as GPS, Glonass or the future Galileo employ several satellites located in an earth orbit and equipped with atomic clocks, which emit the electromagnetic (radio) waves containing time and identity or location information, respectively. The corresponding receivers have to receive the signals of at least three satellites, respectively, in order to be able to determine the current position in space. If the current time is also to be determined, signals from four satellites must be received. Position sensing accuracy increases with the number of satellites. The accuracy of the position sensing systems is commonly improved through the reception of radio signals containing corrective data emitted by reference stations in known locations.  
         [0006]     In the case of slave vehicles steered on the basis of position capturing systems, errors in the absolute positions occurring during the subtraction operation are eliminated as long as the same reception conditions exist for both receivers and they hence use signals of the same satellites. The relative position then is sufficiently accurate. If different reception conditions for the two receivers exist, caused for example by the shading of one satellite for the first receiver (e.g., on the edge of a field covered by trees where the vehicle travels) while the second vehicle travels further inward in the non-shaded center of the field, errors result in the relative position which can lead to undesirable erroneous steering processes of the second vehicle.  
         [0007]     It has further been suggested to detect the quality of signals of satellite-supported position capturing system and if the quality is not sufficient for sufficiently accurate position sensing, to determine the position based on other means, such as radio waves (U.S. Pat. No. 5,999,126 A), sensors for detecting a crop boundary (DE 101 29 133 A, DE 101 29 135 A) or inertial navigation systems (EP 0 604 404 A, JP 04 134 212 A). These means, however, are only provided for a single vehicle and cannot solve the problem of different reception conditions of two receivers.  
         [0008]     It is suggested in JP 04 174 389 A to equip a vehicle with two satellite antennas. For a single satellite the better suited antenna is selected, respectively, in order to obtain as accurate a position signal as possible. This as well cannot solve the problem of different reception conditions of receivers on two vehicles.  
       SUMMARY OF THE INVENTION  
       [0009]     It is therefore an object of the present invention to provide a position sensing system in which the afore-mentioned problems no longer exist or exist to a lesser extent.  
         [0010]     The problems are resolved pursuant to the invention through structure wherein a data link exists between the first vehicle and the second vehicle. The position data of the first vehicle can be transmitted to a computer of the second vehicle or vice versa, and the computer can be operated such that it can determine data with respect to the relative position of the second vehicle in relation to the first vehicle based on the position data of the first vehicle and the position data of the second vehicle. The position sensing devices of both vehicles provide information regarding the quality of the signals of the respectively received satellites to a control device, and the control device can be operated so that the two position sensing devices are in the same reception modes.  
         [0011]     The invention relates to a system for determining the relative position of two farm vehicles, which jointly operate in a field and are equipped with position sensing devices. A computer on one of the two vehicles receives position data from both position sensing devices and uses the received data to determine data regarding the relative position of the two vehicles. Based on the data, steering and/or speed signals can be generated which can be used to operate the second vehicle automatically and possibly without an operator. Alternatively, a driver signal can be provided which may include specific displayed values useful to coordinate the operations of the two vehicles. The position data is transmitted from one vehicle to a computer equipped vehicle, via a wireless data transmission connection operating by means of radio, sound or light waves.  
         [0012]     In order to prevent possible errors in position sensing due to different reception conditions of the receivers of the two position sensing devices, it is suggested that information about the quality of the satellites&#39; signals received by the two position sensing devices be fed to a control device. This information can indicate which of the satellites can even receive information, or it can indicate the field strength or error rate of the signals. The control device is located on board of one of the vehicles and receives the aforementioned information in a wireless fashion from the position sensing device of the other vehicle. The above-mentioned data transmission connection can be used, which then operates bi-directionally. Based on the information regarding the quality of the signals, the control device prompts both position sensing devices to operate in the same reception modes. Here preferably only those satellites are considered, which can be received by both position sensing devices. In another embodiment, the signals of the individual satellites are considered in a weighted fashion as a function of their quality, in particular in the same fashion by both position sensing devices. The control device can be integrated into one of the position sensing devices or can communicate with the position sensing devices as a separate element.  
         [0013]     The above structure assures that both position sensing devices operate in the same reception mode to thereby prevent errors in the determined relative position caused by differing numbers or signal qualities of the satellites received by the position sensing devices. The fact that under certain circumstances the accuracy of the absolute positions can be reduced has no negative effect here.  
         [0014]     For certain applications, however, a relatively accurate absolute position is required. Examples include automatic steering of the first vehicle on the basis of a road map and the position of the first vehicle as determined by the first position sensing device; crop mapping; the documentation of work processes, such as the tractive force applied during cultivation of the soil or the sowing depth; or of spreading processes, such as the amount of fertilizer or seeds that was spread. It is therefore useful to switch the respective position sensing device alternately between two modes of operation. This way operation occurs alternately in a reception mode, as that specified by the control device (i.e., possibly fewer satellites considered in the position determination than can in fact be received), and in a reception mode in which the maximum available position accuracy is achieved by considering all satellites that can be received. If both position sensing devices receive the same satellites, they operate only in that mode in which all receivable satellite signals are considered for position determination.  
         [0015]     The reception conditions taken into consideration by the control device are not limited to whether or not a satellite can be viewed. They can also include the quality of corrective data or the like and can be used for appropriately actuating the position sensing devices. If the corrective signal in one position sensing device is poor, accordingly the corrective signals in both position sensing devices remain unconsidered. Also preliminary results during position data calculation can be adjusted.  
         [0016]     The control device can also switch one or both position sensing devices to a different mode in case of poor reception conditions, e.g., into an inertial navigation operation in which the position is determined, for example, with a gyro compass or the like and a propulsive speed sensor.  
         [0017]     The determined positions can also be fed to the control device. Plausibility tests can then be performed or emergency programs activated to issue warning notices to an operator or a spaced monitoring station to prevent an imminent collision.  
         [0018]     The control device can also instruct a position sensing device to shift its position data in a specified direction in order to compensate for determined errors.  
         [0019]     These and other objects, features and advantages of the present invention will become apparent from the description which follows in view of the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a diagrammatic top view on two farm vehicles, which jointly perform a harvesting and transferring operation on a field.  
         [0021]      FIG. 2  is a diagrammatic view of the position sensing devices of the two vehicles of  FIG. 1  along with interacting elements.  
         [0022]      FIG. 3  is a system flow chart for determining the relative position of the second vehicle in relation to the first vehicle. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]     A first farm vehicle  10  being a type of automated crop chopper shown in  FIG. 1  is constructed on a frame  12 , supported by front-driven wheels  14  and steerable rear wheels  16 . The harvester  10  is operated from a driver&#39;s cab  18 , from which a crop receiving device  20  can be viewed. The crop receiving device  20 , the Crop such as corn, grass or the like is picked up from the ground by the crop receiving device  20  and is fed to a chopper drum, which shreds the crop and passes it on to a conveying device. The crop is conveyed from the vehicle  10  to a trailer  24  traveling next to the vehicle via a discharge auger or conveyor  22  that can pivot about a vertical axis.  
         [0024]     The trailer  24  is pulled by a second farm vehicle  26  shown as a tractor, which includes front steerable wheels  28  and rear-driven wheels  30  rotatably mounted on and supporting a frame  32  having a driver&#39;s cab  34 .  
         [0025]     The first vehicle  10  harvests plants from a field  36 , corn in the illustrated example, which is picked up by the crop receiving device  20  implemented as a corn head. The second vehicle  26  travels on the harvested part  36 ′ of the field parallel to the first vehicle  10  in such a position that the plants shredded in the first vehicle  10  can reach the trailer  24  via the discharge conveyor  22 . The second vehicle  26  therefore must always travel parallel and next to the first vehicle  10 ; especially when turning into the field. The second vehicle  26  can also travel behind the first vehicle  10  when no harvested part  36 ′ of the field  36  exists yet on which the second vehicle  26  could travel without damaging the plants located there.  
         [0026]     The first vehicle  10  is steered by a driver sitting in the driver&#39;s cab  18  or by a conventional automatically operating steering device. The automatic steering device can include a mechanical plant feeler structure which follows individual plants, or an optical image processing, or a laser or ultrasound sensor for detecting the boundary between the part of the field  36  containing the plants and the harvested part  36 ′. An automatic steering system based on the position data of a position sensing system  38  of the first vehicle  10  in conjunction with a road map can also be used. The second vehicle  26  is likewise equipped with a steering device, which is illustrated in more detail below, to facilitate and/or automate parallel travel to the first vehicle  10 .  
         [0027]     The first vehicle  10  could also be another one of a number of other types of automated harvester, such as a combine or beet harvester. The invention can also be used in any other types of farm vehicles which cultivate a field as two or more units. Examples include several combines that travel next to each other and fertilizer distributors or ground cultivators, which can travel in any random relative configurations across the field  36 .  
         [0028]     The first vehicle  10  is equipped with a first position sensing device  38 , which is arranged on the roof of the cab  18 . A first radio antenna  40  is also positioned on the roof. The second vehicle  26  is equipped with a second position sensing device  42 , which is located on the roof of the cab  34 . A second radio antenna  44  is positioned on the roof of the second vehicle  26 .  
         [0029]     Reference is now made to  FIG. 2 , which diagrammatically illustrates the individual components of the position sensing devices  38 ,  42  and the steering devices of the second vehicle  26 . The first position sensing device  38  on board of the first vehicle  10  includes an antenna  46  and an evaluating circuit  48  connected to the antenna  46 . The antenna  46  receives signals from the satellites of a position sensing system, such as GPS, Galileo or Glonass, which are fed to the evaluating circuit  50 . Based on the signals from the satellites, the evaluating circuit  48  determines the current position of the antenna  46 . The evaluating circuit  48  is also connected to a corrective data reception antenna  50  which receives radio waves emitted by reference stations in known locations. Based on the radio waves, the evaluating circuit  48  generates corrective data to improve the accuracy of the position sensing device  38 .  
         [0030]     The evaluating circuit  48  transmits first position data to a first control device  60  via a bus line  58 . The bus line  58  also conveys information regarding the identity of the satellites that can be received at the respective times. The field strength on the corrective data reception antenna  50  is transmitted to the control device  60 .  
         [0031]     The control device  60  is connected via an interface  66  to a transmit-receive device  68 , which in turn is connected to the radio antenna  40 . The transmit-receive device  68  receives and generates radio waves, which are received or emitted by the antenna  40 . The second position sensing device  42 , which includes an antenna  52  and an evaluating circuit  54  connected to the antenna  52 , is located on board of the second vehicle  26 . The antenna  52  receives signals from satellites of the same position sensing system as the antenna  46 . The satellite signals are fed to the evaluating circuit  54 . Based on the signals from the satellites, the evaluating circuit  54  determines the current position of the antenna  52 . The evaluating circuit  54  is also connected to a corrective data reception antenna  56  which receives radio waves emitted by reference stations in known locations. Based on the radio waves, the evaluating circuit  54  generates corrective data for improving the accuracy of the position sensing device  42 .  
         [0032]     The evaluating circuit  54  transmits a second set of position data to a computer  64  via a bus line  62 . The bus line  62  transmits information to the computer  64 , including information regarding the identity of the satellites that can be received at the respective times and information on the field strength of the corrective data reception antenna  56 .  
         [0033]     The computer  64  is connected via an interface  70  to a transmit-receive device  72 , which in turn is connected to the radio antenna  44 . The transmit-receive device  72  receives and generates radio waves, which are received or emitted by the antenna  44 . Through the transmit-receive devices  68 ,  72  and the radio antennas  40 ,  44  data can be transmitted from the control device  60  to the computer  64  and from the computer  64  to the control device  60 . The connection between the antennas  40 ,  44  can be a direct one, e.g., in an approved radio frequency such as CB radio or the like, or it can be established via one or more relay stations, for example when the transmit-receive devices  68 ,  72  and the radio antennas  40 ,  44  operate based on the GSM standard or another suitable standard for cellular telephones.  
         [0034]     The flow chart in  FIG. 3  shows the operation of the system for determining the relative position of the second vehicle in relation to the first vehicle. In operation, after starting in step  100 , the control device  60  transmits position data of the first vehicle  10  generated by the first position sensing device  38  to the computer  64  of the first vehicle  26  (step  102 ) at regular intervals, for example, every 100 ms. The computer  64  receives the simultaneously determined or approximately simultaneously determined position data of the second vehicle from the second position sensing device  42  (step  104 ). Thereafter, the computer  64  determines in step  106  the difference between the two positions and compares the difference to a target value expedient for proper filling of the trailer  24 . Steering signals generated based on the comparison steering signals are fed to an automatic steering device  74 , which is equipped to specify the position of the steerable wheels  28  of the vehicle  26 . Additionally, based on the afore-mentioned comparison, the computer  64  generates speed signals and transmits them to a speed specification device  76  which regulates the speed of the second vehicle  26  by varying the engine rotational speed of the second vehicle  26  and/or the gear ratio. The target value for the difference in the positions of the two vehicles  10 ,  26  can be firmly specified in the computer. Alternatively, the target value is determined based on stored and/or transmitted vehicle data or is programmed (taking into consideration the respective position data of the two vehicles  10 ,  16 ) into the computer after a calibrating input by the operator of one of the two vehicles  10  or  26  after the vehicles have been brought into a suitable relative position.  
         [0035]     A further feature is possible wherein only the steering device  74  is activated automatically, while the operator regulates the speed input device  76 . In this way, the entire trailer  24  can be filled gradually. A further possible feature would be to facilitate operator regulation of the steering device  74  and the speed input device  76  and provide a target value signal to the operator through the computer  64 .  
         [0036]     In order to ensure that both position sensing devices  38  and  42  operate under the same operating conditions, the computer  64  transmits in step  108  information regarding the identity of the satellites that can be received with the antenna  52  at the respective times and the field strength on the corrective data reception antenna  56  to the control device  60  via the bidirectional data transmission connection by means of the antennas  40 ,  42 . The control device  60  also receives in step  110  corresponding data for the antenna  46  and the corrective data reception antenna  50 . The control device  60  compares in step  112  the data and transmits information regarding the intersection of receivable satellites to the evaluating circuit  48  and, via the data transmission connection and the computer  64 , to the evaluating circuit  54 . The evaluating circuits  48  and  54  are instructed to take into consideration only signals from satellites that both antennas  46  and  52  can receive when calculating the position data. This way, errors in the position data, which can be caused by different satellites taken into consideration in the position determination, can be prevented. Subsequently the procedure is begun again with step  100 .  
         [0037]     In addition, the evaluating circuits  48  and  54  only take into consideration corrective signals from the corrective data reception antennas  50  and  56  when both receive sufficient field strengths. The control device  60  makes a decision based on the field strength data available and transmits corresponding instructions to the evaluating circuits  48  and  54 .  
         [0038]     The first vehicle  10  includes a throughput measuring device  78  which measures, for example, the vertical distance between two prepress rollers which are arranged upstream from the chopper drum. A storage device  80  is connected to the throughput measuring device  78  and serves the georeferenced mapping of the readings of the throughput measuring device  78 . In order to obtain information about the appropriate position of the first vehicle  10 , the storage device  80  is connected to the control device  60 . When the storage device  80  signals to the control device  60  for position data that is required, the control device  60  prompts the evaluating circuit  48  in the meantime to make available position data based on all receivable satellites. The position data is then transmitted to the storage device  80  rather than the control device  64 .  
         [0039]     The control device  60  is also connected to an inertial navigation system  82 , and the computer  64  is connected to an inertial navigation system  84 . If the number of different satellites receivable is insufficient to generate position data, the control device  60  transmits the output data of the inertial navigation system  82  to the computer  64  which based on the output data of the inertial navigation systems  82  and  84  and the last available reliable position data from the position sensing devices  38 ,  42  determines the relative positions of both vehicles  10 ,  26  and transmits corresponding steering and speed specification signals to the steering device  74  and the speed specification device  76 . The output data of the inertial navigation system  82  can also serve as position data for the storage device  80 , if necessary.  
         [0040]     Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.