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TECHNICAL FIELD 
       [0001]    The present disclosure relates to control of automated excavation machines, particularly real-time coordination between multiple automated excavation machines. 
       BACKGROUND 
       [0002]    Worksites, particularly mining worksites, are increasingly using automated machines, such as automated dozers, to move earth into position for excavation and processing. The automated machines often work in parallel slots using location information and topographical maps to determine where to load and spread. In many cases, the spread zone is at a crest or ledge where traveling too far may result in the machine tipping over the crest or causing a slide. In these cases, the machine may be released from automatic control and operated manually by a remote human operator. 
         [0003]    It is possible that more machines may enter the spread zone than there are human operators to manually control them. In this case, it is common to stop a machine prior to its entering the spread zone. However, restarting a machine with a fully loaded blade induces a great deal of stress on multiple areas of the machine from the blade to the drive train. This may lead to increased wear and unnecessarily accelerate component failure in the drive train, tracks, and blade components of the machine. 
         [0004]    With respect to preventing multiple machines from being in a particular operating zone, U.S. Pat. No. 8,265,873 (the &#39;873 patent) discloses a system that divides the path for a mobile unit into segments and reserves various segments along its path to prevent multiple units from concurrently occupying the same path segment. The &#39;873 patent at least fails to account for a state of the machine, such as blade load, when allocating segment reservations. 
       SUMMARY OF THE DISCLOSURE 
       [0005]    In an aspect of the disclosure, a method of managing automated machines at a worksite includes identifying a zone at the worksite, the zone having geographic boundaries specified, and setting a limit on a number of machines concurrently allowed in the zone. The method may continue by predicting when a first machine will be within the geographic boundaries of the zone and also predicting that a second machine operating at current conditions will be within the geographic boundaries of the zone concurrently with the first machine such that the second machine&#39;s entry into the zone will cause the number of machines in the zone to exceed the limit. The method may continue by analyzing a load of a blade on the second machine and when the second machine blade is loaded, setting, via a controller remote from the automated machines, the second machine to a lower speed than a current speed. The lower speed may be calculated to prevent the second machine from entering the zone while the first machine occupies the zone. The method may also include, when the blade of the second machine is unloaded, stopping, via the controller, the second machine for a duration calculated to prevent the second machine from entering the zone while the first machine occupies the zone. 
         [0006]    In another aspect of the disclosure, a system for managing automated machines includes a first machine that operates responsive to commands from a controller, a second machine that operates responsive to commands from the controller, and the controller. The controller may be configured to send operating commands to the first and second machines, wherein the controller defines a zone with geographic boundaries at the worksite and predicts that more than a predetermined number of machines will be within the zone given a current operating state of each machine. Responsive to the prediction, the controller controls the second machine according to a load of a blade on the second machine to prevent entry of the second machine into the zone when the first machine is in the zone. 
         [0007]    In yet another aspect of the disclosure, a controller that manages two or more automated machines operating in separate designated slots at a worksite includes a processor, an output driver coupled to the processor used to control at least one automated machine, and a memory coupled to the processor storing executable instructions. The executable instructions cause the processor to identify a zone within the worksite, identify a limit number of machines that can operate in the zone concurrently, and determine, based on a location prediction, when more than the limit number of machines will occupy the zone concurrently. Based on the current operating state of at least one of the two or more machines, the controller may alter an operating characteristic of at least one of the two or more automated machines to prevent more than the limit number of machines from occupying the zone concurrently. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a plan view of a worksite; 
           [0009]      FIG. 2  is a side elevation view of the worksite of  FIG. 1 ; 
           [0010]      FIG. 3  is another plan view of the worksite of  FIG. 1 ; 
           [0011]      FIG. 4  is a block diagram of an exemplary controller for use in an automated mobile excavation machine control system; and 
           [0012]      FIG. 5  is a flowchart of an exemplary method of managing automated excavation machines at a worksite. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Mining and other earthmoving-related operations are increasingly using automated mobile excavation machines to cut contours and move earth either out of the way or to a loading/processing area.  FIG. 1  illustrates a mining operation  100  including a worksite  102  set up for automated excavation work. The worksite  102  may include designated slots  104 ,  106 ,  108  in which respective automated machines  112 ,  114 ,  116  may operate, such as automated track-type tractor dozers. The worksite  102  may include a spread zone  110 , also known as a spread gap or crest zone where material accumulated during the run of the machine  116  may be unloaded from the blade  117 . 
         [0014]    A controller  128  may be located at a central control station and may communicate with each of the automated machines  112 ,  114 ,  116  to receive both information about the position and status of each of the machines and to send instructions to each of the machines regarding speed, direction, blade position, ripper position, etc. The status of the machine may include operational information such as drawbar pull, blade position, gear setting, and groundspeed as well as state information such as oil pressure, fuel level, oil and coolant temperatures, etc. 
         [0015]    One or more human operators  130  may interact with the controller  128  to both oversee automated operations and to manually take control of a particular machine when needed, for example when operating in the spread zone  110 . 
         [0016]      FIG. 2  illustrates a side view of the worksite  102  illustrating spread zone  110  and associated crest  111 .  FIG. 2  shows the current position of the machines in  FIG. 1 , with machine  112  at a top or start of its slot  104  with its blade  113  unloaded, machine  114  in mid-run with a loaded blade  115  at slot  106 , and machine  116  in the process of spreading its load from blade  117  in the spread zone  110  of slot  108 . The need for caution while operating in the spread zone  110  is apparent from the crest  111  and associated drop off so that the machine  116  is not unnecessarily put at risk of toppling over the crest  111 . For this reason the operator  130  may take over manual control of the operation of any machine  112 ,  114 ,  116  while it is in the spread zone  110 . As will be referred to below, the maximum blade load may occur any time after the beginning of the run, such as during the mid-portion of a particular slot and may continue through to a beginning of the spread zone  110 . It is common for a blade load of an exemplary machine  116  to be in a range of 100 tons. 
         [0017]    In the following example for simplicity of explanation it will be assumed that there is one human operator and a limit of one will be set for the number of automated machines  112 ,  114 ,  116  that can be allowed in the spread zone  110  at one time. Obviously, other operating conditions may dictate a different limit. Should the controller  128  determine that in order to avoid having two of the machines  112 ,  114 ,  116  concurrently operating in the spread zone  110 , a change to a current operating state of one or more of the machines  112 ,  114 ,  116  needs to occur. 
         [0018]    For example, referring to  FIG. 2 , the controller  128  may determine that machines  114  and  116  will concurrently occupy the spread zone  110 . Because the rule in this example embodiment does not allow two machines to concurrently occupy the spread zone  110 , the controller  128  may send one or more operating commands to change an operating characteristic of one machine to delay its entry to the spread zone  110 . Again in this example, the machine  116  that is currently in the spread zone  110 , is already under manual control, so the controller is limited to changing the operating characteristic of the other machine  114 . In the case where both machines are still under automated control, more options may be available, as discussed below. 
         [0019]    One option is to stop machine  114 . However, as discussed above, starting machine  114  from a dead stop with a loaded blade may cause an undesirable wear on one or more of its components. Therefore, when the machine  114  has a loaded blade it is preferable to slow the machine  114  rather than stop it. This may be accomplished by reducing its gear in order to delay its entry into the spread zone  110 . Reducing a throttle setting is another option, but often this type of machine is operated at an optimum range of engine revolutions per minute (rpm) settings so reducing the gear may be the preferred way to slow the machine. 
         [0020]    In another example, the controller  128  may determine that machine  112  and machine  114  will occupy the spread zone  110  concurrently. In this case, machine  112  may be stopped since it&#39;s blade is unloaded and no undesirable wear will be incurred by restarting from the stopped state. It is, in most cases, desirable to effect changes to an unloaded machine both because it lowers the chance of wear on the machine as well as saving fuel by delaying the unloaded versus loaded machine. In theory, a speed of the lead machine  114  may be increased to further distance it from the trailing machine  112 , but in many cases the machine  114  may already be operating at a fastest desired speed. In other cases, an increase in speed may cause an undesired overlap with machine  116  or another machine ahead of machine  114 . In an embodiment, all machines  112 ,  114 ,  116  are always monitored and predicted spread zone occupancy predictions are continuously updated for each machine. 
         [0021]    Referring to  FIG. 3  and still referencing this current example, rather than stopping machine  112 , the machine  112  may be driven in a zigzag or serpentine path to delay the entry of machine  112  into the spread zone  110  until after machine  114  can be unloaded and backed out of the spread zone  110 . Variations of this exact protocol may be implemented, for example, two machines may be allowed in a spread zone  110  as long as one machine is in reverse and no longer under manual control. 
         [0022]    The reduction in wear caused by selectively slowing or stopping machines  112 ,  114 ,  116  may be significant enough to warrant even a slight loss in productivity caused by taking such a step. Not only is wear reduced, reducing the cost associated with replacing worn parts, but the uptime is increased, allowing the machines to operate longer between maintenance downtimes. 
         [0023]      FIG. 4  illustrates an exemplary controller  128  including a processor  150  and a memory  152  coupled by a data bus  154 . The controller  128  may also include an operator interface  156  used to receive instructions, worksite definitions, and for manual control of a machine when required. Machine input data may be received via one or more wireless interfaces  158  and may include, as discussed above, machine position, machine operating information such as blade load drawbar pull, as well as machine status information such as temperatures, pressures, warning indicators, and fuel load. 
         [0024]    The memory  152  may be any combination of volatile and nonvolatile memory including both solid-state and rotating media but does not include propagated media such as carrier waves. The memory  152  may include an operating system  160  and utilities  162  used to support basic functionality and set up of the controller  128 . The memory  152  may also include program code  164 . The program code  164  may include executable instructions that are used by the processor  150  to define and implement an excavation strategy  166  related to worksite operations as well as a location prediction module  168  and a location management module  170 . The location prediction module may use a number of inputs to determine speed and run times for machines  112 ,  114 ,  116  including, but not limited to, loaded volume predictions, pitch (slope) prediction, terrain curvature, learned material hardness, and multipliers based on previous run data. The location management module  170  may operate on data developed by the location prediction module  168  to slow or stop a machine  112 ,  114 ,  116  responsive to a prediction that more than a limit number of machines will concurrently reside in a spread zone  110 . Site map data  172  may include contour and other information about the worksite  102  and may include a particular set of zone definition data  174 , such as geographic boundaries received via programming or via the operator interface  156 , that defines, for example, a spread zone  110 . 
         [0025]    The controller  128  may also include one or more output drivers  180  that send signals be of the same or different wireless connections to machines  112 ,  114 ,  116  to implement both automatic and manual control of those machines. 
       INDUSTRIAL APPLICABILITY 
       [0026]      FIG. 5  is a flowchart of an exemplary method  200  of regulating the pace of automated machines  112 ,  114 ,  116  at a worksite  102  to both increase safety and reduce component wear in the automated machines. Safety is increased when an operator is not faced with manually operating multiple machines in a spread zone  110 . Component wear is reduced when machines are not stopped and started under heavily loaded conditions. At block  202 , a spread zone  110  at a worksite  102  may be identified and a limit may be placed on the number of machines that are to be allowed in the zone  110  at any one time. 
         [0027]    At block  204 , a prediction may be made of a time when a first machine  116  will be in the zone  110 . At block  206 , a prediction may be made that under current operating conditions, such as a current speed, a second machine  114  will concurrently be in the zone  110  with the first machine  116 . That is, if no changes to speed or course are made to either machine, both the first and second machine  114 ,  116  will be in the zone  110  at the same time. 
         [0028]    At block  208 , an analysis may be made of the blade load of the second machine  114 . If the second machine  114  is loaded, the “loaded” branch may be taken from block  208  to block  212 . At block  212 , because the second machine  114  is carrying a load on its blade, the second machine  114  may be set to a lower speed either by throttling down or by reducing from a current gear to a lower gear so as to avoid coming to a complete stop. An amount of the speed reduction combined with the distance over which the delay is imposed may be used to determine a duration of the delay imposed on the second machine  114 . In an exemplary embodiment, this delay may be in a range of four to six seconds. 
         [0029]    Returning to block  208 , if the second machine  114  is unloaded, the “unloaded” branch may be taken to block  210 . At block  210 , the second machine may be stopped, slowed, or delayed so that the desired delay required to avoid both machines being in the zone  110  is achieved. When stopped, the duration of the stop may simply be the desired time delay. When slowed, the change in speed multiplied by the travel distance at the lower speed can be calculated to give the time delay needed to avoid concurrent occupation in the zone  110 . When increasing the path length, the speed times the increased distance can be calculated to give the desired time delay. 
         [0030]    The ability to analyze a machine operating state and selectively stop or slow a machine based on its current load gives an operator  130  using automated excavating machines  112 ,  114 ,  116  a valuable tool to minimize wear and tear on expensive equipment while still maintaining manual control in areas where safety is an issue. Even if some delays are incurred in the above-described operations, overall uptime for equipment should be improved by reducing or eliminating the stop/start cycles of fully loaded machines so that the cost of slowing some machines slightly can be recouped through longer intervals between maintenance and fewer damaged components.

Summary:
Automated excavating uses automated dozers and other earthmoving equipment to move material at a worksite. Some areas of the worksite may require that control of the automated dozer revert to manual control, such as a spread zone near a crest. A controller monitors the position of automated dozers and adjusts an operating characteristic of an individual automated dozer so that there are not more dozers in the zone than there are operators to manually control them. The adjustment made may depend on the blade loading of an individual dozer, particularly so that a dozer with a loaded blade is not brought to a complete stop, which may cause undue wear on the dozer when re-starting.