Patent Publication Number: US-9414204-B2

Title: Fleet communication network

Description:
This is a continuation of U.S. application Ser. No. 12/391,911, filed Feb. 24, 2009, based on which this continuation claims priority under 35 U.S. C. §120. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to communication networks and, more particularly, to a fleet communication network. 
     BACKGROUND 
     Worksites, such as mines, landfills, quarries, excavation sites, etc., commonly have machines operating thereon to perform a variety of tasks. At a mining site, for example, a fleet of mining shovels and haul trucks may cooperate to remove material from various quarries and to transport the material to various dump sites. Communication networks have been provided to enable fleet communication on the worksite. A conventional worksite communication network includes a fleet of machines and a dispatch system which coordinates operations of the fleet to accomplish the task at hand. The fleet members may monitor their performance on the worksite, and may transmit performance data to the dispatch system. The dispatch system may, based on the performance data, monitor progress at the worksite and coordinate machine operations to efficiently accomplish the task. In addition, the fleet members may communicate with each other, such as to avoid collisions, to provide loading or dumping positioning information, or for other reasons. 
     Due to the nature of the worksite, however, it can be difficult to establish reliable communication networks. The movement of the fleet members, geographical obstacles, exposure to the elements, and other factors can degrade the integrity of signal transmissions. Accordingly, there is a need to provide reliable communication networks suitable for changing conditions on the worksite. 
     One such communication network is disclosed in U.S. Patent Application Publication No. 2005/0002354 by Kelly et al., published on Jan. 6, 2005 (the &#39;354 publication). The &#39;354 publication discloses an ad-hoc communication network whereby machines form sub-networks as they travel about the worksite and come within communication range of one another. Collectively, the sub-networks form an overall ad-hoc network that allows the machines to communicate with each other via intermediate nodes overlapped by two or more sub-networks. 
     While the communication network formed by the &#39;354 publication may be advantageous because of its versatility, it may be unreliable in some ways. For example, a message transmitted on the network propagates from source to destination across the sub-networks, and between the sub-networks via the intermediate nodes. However, because the structure of the network continually changes with the movement of the machines, the path from a particular source to a particular destination may also continually change. Accordingly, traffic on the network is not structured or organized in any particular way to ensure reliability, because the network architecture is based entirely upon geographical location. 
     This disclosure is directed to overcoming one or more of the problems set forth above. 
     SUMMARY 
     One aspect is directed to a communication network for a fleet of vehicles. The communication network may include a first group of the fleet of vehicles having a first level of priority on the network and a second group of the fleet of vehicles having a second level of priority on the network. In addition, a first vehicle in the first group may be assigned as a supervisor of a second vehicle in the second group. 
     Another aspect is directed to a communication method for a network of a fleet of vehicles. The method may include assigning a first group of the fleet of vehicles to a first level of priority on the network, assigning a second group of the fleet of vehicles to a second level of priority on the network, and assigning a first vehicle in the first group as a supervisor of a second vehicle in the second group. 
     Yet another aspect is directed to another communication network for a fleet of vehicles. The communication network has an off-board system configured to transmit a message destined for a first vehicle in the fleet, a first group of the fleet of vehicles having a first level of priority on the network and including the first vehicle, and a second group of the fleet of vehicles having a second level of priority on the network and including a second vehicle assigned as a supervisor of the first vehicle. The vehicles in the fleet may be configured to receive the message from the off board system, determine whether the first vehicle is within direct communication range and, when the first vehicle is not within direct communication range, forward the message to the second vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a representation of an exemplary environment in which a fleet of machines operates; 
         FIG. 2  is a representation of an exemplary machine operating in the environment of  FIG. 1 ; 
         FIG. 3  is a representation of an exemplary disclosed gateway onboard the machine of  FIG. 2 ; 
         FIG. 4  is a representation of exemplary disclosed network information stored in memory of the machine of  FIG. 2 ; 
         FIG. 5  is a representation of an exemplary disclosed communication network for the fleet of machines in  FIG. 1 ; 
         FIG. 6  is a flowchart describing an exemplary disclosed message forwarding process performed by a fleet member of  FIG. 1 ; 
         FIG. 7  is a representation of an exemplary message transmitted on the communication network of  FIG. 5 ; and 
         FIG. 8  is a flowchart describing an exemplary disclosed process performed by an off-board system for promoting a fleet member. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an exemplary environment  100  in which the disclosed fleet communication network may be implemented. Environment  100  may represent, for example, a construction site, a quarry, an excavation site, a highway system, a war zone, or another environment in which a fleet  102  of machines  104  may cooperate to accomplish a task. Machines  104  may include, for example, haul trucks, excavators, dozers, loaders, graders, scrapers, passenger vehicles, battle vehicles, or other mobile machines which perform a task. Machines  104  may also include immobile machines, such as a power systems (e.g., generator sets) or offshore drilling platforms. In one example, environment  100  may be an excavation site upon which fleet  102  cooperates in earth-working operations. It is noted, however, that the examples listed above are intended to be non-limiting, as other suitable types of machines and environments are contemplated. Machines  104  may be manned or unmanned, and may be autonomous, semi-autonomous, or completely manually controlled. Fleet  102  may be interconnected via a communication network  106  to exchange information in connection with various tasks performed by fleet  102 . 
       FIG. 2  illustrates an exemplary control system  200  onboard machine  104 . Onboard system  200  may monitor or control functions of machine  104 . For example, onboard system  104  may control and monitor mechanical or electrical systems onboard machine  104  in connection with autonomous control of machine  104 . Onboard system  200  may also communicate with an off-board system  202  or with other fleet members to exchange information in connection with autonomous control of machine  104  or with other operations. 
     As shown by  FIG. 2 , onboard system  200  may include a power train control module  204 , a positioning module  206 , a hydraulic system control module  208 , a power system control module  210 , a brake system control module  212 , a navigation control module  214 , and a gateway module  216  interconnected on bus  218 . It is noted that onboard system  200  may include other components than those listed above for performing different functions. 
     Power train control module  204  may be an electronic control unit which controls operations of a combustion engine (not shown) and a transmission (not shown) onboard machine  104 . For example, based on signals from bus  218  (e.g., signals from other onboard modules) and on signals from various sensors, power train control module  204  may command the quantity of fuel injected into the combustion engine, ignition timing, valve timing, or other operations of the combustion engine. Power train control module  204  may also determine and command an appropriate gear for the transmission. 
     Positioning module  206  may be an electronic control unit which determines the position and orientation of machine  104 . For example, positioning module  206  may be associated with a global positioning system (GPS) receiver  220  which receives signals from GPS satellites (not shown). Based on the received signals, positioning module  206  may determine a real-time position, speed, or velocity of machine  104 . Alternatively or additionally, positioning module  206  may include an Inertial Reference Unit (IRU), an odometric or dead-reckoning device, a speed sensor, an accelerometer, a radio direction finder, or another device for determining the position and/or speed of machine  104 . In addition, positioning module  206  may include a tilt sensor, an inclinometer, a gyrocompass, a radio direction finder, or another device for determining the pitch, roll, or yaw (i.e., orientation) of machine  104 . Positioning module  206  may transmit on bus  218  signals indicative of the determined position, orientation, direction, speed, or velocity of machine  104 . 
     Hydraulic system control module  208  may be an electronic control unit which controls a hydraulic system (not shown) onboard machine  104 . For example, based on signals received from bus  218  and on signals from various sensors associated with the hydraulic system, hydraulic system control module  208  may generate control signals for various hydraulic valves to control the motion of an implement, such as a bucket, a dump bed, a ripper, or tool with which machine  104  may be equipped. Hydraulic system control module  208  may also control any other hydraulic systems onboard machine  104 . 
     Power system control module  210  may be an electronic control unit which controls power distribution to various electronic systems onboard machine  104 . For example, power system control module  210  may generate signals to control a generator-motor (not shown), a pump-motor (not shown), or another device to manage the storage and consumption of power onboard machine  104  (e.g., hybrid power management, auxiliary power management, etc.). 
     Brake control module  212  may be an electronic control unit which controls the application of the machine&#39;s brakes based on signals on bus  218 , For example, brake control module  212  may transmit control signals to valves associated with a pressurized air or hydraulic brake system (not shown) onboard machine  104  to engage or disengage the machine&#39;s brakes. 
     Navigation control module  214  may control one or more of the other onboard modules  204 - 212  in connection with autonomous or semi-autonomous operation of machine  104 . For example, navigation control module  214  may access a task plan stored in a memory (not shown) or received from off-board system  202 . A task plan may include, for example, computer program instructions for causing machine  104  to perform various tasks. For example, a task plan for a dump truck may include repeating the steps of traveling to a first location to be loaded by an excavator with material, performing a handshake communication with the excavator when within communication range, receiving loading position information from the excavator, positioning itself with respect to the excavator for loading based on the received loading position information, sending a signal to the excavator when loading capacity has been reached, traveling to a second location, and dumping the ore at the second location. Accordingly, based on such a task plan, navigation control module  214  may send various command signals on bus  218  for execution by onboard modules  204 - 212 . 
     It is to be appreciated that on-board system  200  may further include an operator interface module (not shown), which may receive input from an operator at the controls of machine  104 . Based on the operator&#39;s input, the operator interface module may send various command signals on bus  218  for execution by onboard modules  204 - 214  Accordingly, machine  104  may be fully-autonomous, semi-autonomous, or controlled manually by an operator. 
     Gateway  216  may be an electronic control module which provides a communication interface between onboard modules  204 - 214  and off-board system  202  and other fleet members. For example, gateway  216  may include communications hardware and software for leveraging a radio communication device  222  (e.g., an antenna) to transmit messages to, and to receive messages from, off-board system  202  and other fleet members. As shown by  FIG. 3 , gateway  216  may include an onboard communication module  300 , an off-board communication module  302 , a protocol conversion module  304 , and a network communication module  306 , among other things. 
     Onboard communication module  300  may interface with bus  218  to receive messages from, and provide messages to, onboard modules  204 - 214 . For example, onboard communication module  300  may include an onboard data link port  308  for each of onboard modules  204 - 214 . Messages sent to, or received from, an onboard module  204 - 214  may be transmitted to, or received from, bus  218  via a corresponding onboard data link port  308 . Onboard data link ports  308  may include a controller area network (CAN) data link, a Society of Automotive Engineers (SAE) J1850 or J1939 data link, a Media Oriented Systems Transport (MOST) data link, an Ethernet data link, FlexRay™ data link, a Bluetooth™ data link, an RS-232 or -242 data link, or another suitable data link for communicating with onboard modules  204 - 214 . 
     Off-board communication module  302  may be a communication interface between gateway  216  and off-board system  202  and other fleet members. Specifically, off-board communication module  302  may leverage off-board data link ports  310  to receive messages from, and provide messages to, off-board system  202  and other fleet members. Off-board data link ports  310  may include a controller area network (CAN) data link, a wireless local area network (WLAN) data link, a wireless wide area network data link (WWAN), a radio data link, a satellite data link, or another suitable wireless data link for communicating with off-board system  202  and with other fleet members. In one aspect, each data link port  310  may provide a communication channel with a particular fleet member or with off-board system  202 . For example, each data link port  310  and may be associated with a unique network address, such as Internet Protocol (IP) address, corresponding to a particular fleet member or to off-board system  202 . 
     Protocol conversion module  304  may convert or translate messages from one protocol to another. Specifically, protocol conversion module  304  may convert onboard messages received from bus  218  to a format compatible for off-board communication, and vice versa. The protocol conversion may be based on the onboard data link port from which the message is received and on the off-board data link port through which the message must be forwarded to reach its destination, and vice versa. For example, protocol conversion module  304  may convert a message received from power train control module  204  from a format appropriate for onboard communication to a format appropriate for off-board communication to another fleet member or to off-board system  202 . Similarly, protocol conversion module  304  may covert a message received from a fleet member or from off-board system  202  from a format appropriate for off-board communication to a format appropriate for onboard communication and processing by navigation control module  214 . 
     Network communication module  306  may leverage onboard communication module  300 , off-board communication module  302 , protocol conversion module  304 , and a network information database  312  to route messages received by gateway  216 . Specifically, based on the source address and the destination address of a message, network communication module  306  may determine through which of onboard data link ports  308  or off-board data link ports  310  the message must be forwarded, and whether any processing by protocol conversion module  304  is necessary. 
     It is noted that onboard modules  204 - 216  may be implemented by hardware and/or by combinations of hardware and software. For example, onboard modules  204 - 216  may include software on an integrated circuit (IC), such as an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a flash module, or another suitable IC. Accordingly, onboard modules  204 - 216  may be embodied as a single IC (i.e., a controller) configured to perform all of the functions of onboard modules  204 - 216 , or as multiple ICs each configured to perform different functions of onboard modules  204 - 216 . Alternatively, onboard modules  204 - 216  may be implemented by way of a microprocessor executing software instructions for performing the functions of onboard modules  204 - 216 . Onboard modules  204 - 216  may also include or otherwise be associated with any means for storing or processing information, such as a central processing unit (CPU), random access memory (RAM), read-only memory (ROM), a magnetic or optical storage device, or other computer-readable storage media. Onboard modules  204 - 216  may also be associated with power supply circuitry, signal-conditioning circuitry, solenoid driver circuitry, communication circuitry, or other appropriate circuitry. 
     Network information database  312  may be, for example, a database stored in memory associated with gateway  216  and containing information about the structure of communication network  106 .  FIG. 4  shows a representation of network information database  312 . As illustrated, network information database  312  may include, for example, a machine information table  400  and a network information table  402 . 
     Machine information table  400  may contain information about communication network  106  and about the location of machine  104  on communication network  106 . For example, machine information table  400  may indicate a network level  404  of machine  104 , an identification number  406  of machine  104 , a network level  408  of a supervisor of machine  104 , an identification number  409  of the supervisor, and an address  410  of machine  104  on communication network  106  (e.g., an IP address). Fleet members and off-board system  202  may correspond to “nodes” in communication network  106 . 
     According to one aspect, communication network  106  may be divided into tiers or levels of priority. As described in further detail below, these tiers or levels may be utilized when a destination machine is not within direct communication range, so that traffic on network  106  follows a structured pattern (rather than an arbitrary pattern). As a result, communication on network  106  may be made more reliable, and network resources can be conserved. A fleet member in a higher level may be responsible for transmitting, receiving, forwarding, or otherwise managing the communications of a fleet member in a lower level, as discussed below. Network level  404  may indicate to what level of communication network  106  machine  104  is assigned (e.g., level 3). In one example, level 1 may correspond to a higher level of priority of than level 2, level 2 may correspond to a higher level of priority than level 3, etc. 
     Machine identification number  406  may be a number or another ID assigned to machine  104  within the network level to which it is assigned. For example, level 2 of communication network may contain five fleet members, and machine  104  may be designated the third machine in the level (e.g., machine  3 ). 
     Supervisor network level  408  may indicate the network level to which the supervisor of machine  104  is assigned (e.g., level 1). Supervisor identification number  409  may be a number (or another ID) assigned to the supervisor of machine  104  within the network level to which it is assigned (e.g., machine  2 ). A “supervisor,” as used herein, may be any fleet member in communication network  106  assigned to a network level directly above another fleet member for which it handles communications. A supervisor may be responsible for transmitting, receiving, forwarding, or otherwise managing communications of its supervisees when the supervisees or their destinations are not within direct communication range. For example, messages destined for machine  104  (or another fleet member) may be routed via the supervisor of machine  104 . Likewise, a message from machine  104  (or another fleet member) destined for off-board system  202  may be routed through the supervisor of machine  104 . In other words, a supervisor may act as a node through which communications involving its supervisees are channeled when the supervisees or their destinations are not within direct communication range. Accordingly, any fleet member in communication network  106  may be referenced by its network level  404 , its machine identification number  406 , and its supervisor&#39;s identification number  409 . 
     Network information table  402  may contain information describing the manner in which communication network  106  is organized. As shown in  FIG. 4 , network information table  402  may contain a network level column  412 , a machine identification number column  414 , a supervisor network level column  416 , a supervisor identification number column  417 , a peers in local network column  418 , a fleet members within direct communication range column  420 , and a network address column  422 . Network information table  402  may be a relational database or another data storage structure suitable for storing, searching, sorting, reading, or writing data in an organized fashion. 
     Network level column  412  may list the various priority levels within communication network  106  (e.g., levels 1-5). For example, network level column  412  may list all levels of communication network  106  to which at least one fleet member is assigned, it is to be appreciated that communication network  106  may include any number of levels, depending upon the particular implementation. 
     Machine identification number column  414  may list the numbers (or other IDs) of the fleet members within the network level to which they are assigned. It is to be appreciated that each network level may contain any amount of fleet members, depending upon the particular implementation. For example, level 1 may contain only machine  1 , level 2 may contain machines  1 - 3 , level 3 may contain machines  1 - 7 , etc. Fleet members in the same network level may be considered “peers,” as they may have the same degree of priority on communication network  106 . 
     Supervisor network level column  416  may list the network levels to which the supervisors of the fleet members listed in columns  412  and  414  are assigned. Supervisor identification number column  417  may list the numbers (or other IDs) of the supervisors of the fleet members listed in columns  412  and  414  within the network levels to which they are assigned. For example, machine  1  in level 1 may be the supervisor of machines  1 - 3  in level 2, and machine  2  in level 2 may be the supervisor of machines  4 - 9  in level 3, etc. 
     Peers in local network column  418  may list identification numbers (or other IDs) of fleet members which share supervisors with corresponding fleet members listed in columns  412  and  414 . For example, machines  1 - 4  in level 3 may all share as a supervisor machine  2  in level 2. Accordingly, machines  1 - 4  in level 3 may be listed in column  418  across from machine  2  in level 2 in columns  412  and  414 . A supervisor and its respective supervisees may be considered a “local network” or a “local cell.” 
     Fleet members within direct communication range column  420  may list information about other fleet members (or off-board system  202 ) that are within direct radio communication range of respective fleet members listed in columns  412  and  414 . Specifically, column  420  may identify the network levels and numbers within the network levels of such fleet members. For example, machine  3  in level 3 may be in direct radio communication range of machine  2  in level 3, of machine  4  in level 2, and of off-board system  202 . It is to be appreciated that information listed in column  420  may change as the fleet members travel about environment  100  and move in and out of direct radio communication range with each other or with off-board system  202 . For example, fleet members may periodically broadcast a beacon, and any fleet member that receives the beacon may acknowledge receipt of the beacon. Each fleet member may then update its respective column  420  in network table  402  to indicate that the other fleet member is currently within direct communication range. The fleet members may also communicate upstream (i.e., to a supervisor) a message indicating that the status of communication network  106  has changed (i.e., that the two fleet members are now within direct communication range). Each fleet member that receives the message may forward it upstream until it reaches off-board system  202 . Such status messages may similarly be communicated upstream to off-board system  202  in other situations, such as when a fleet member goes off-line. In response, off-board system  202  may broadcast a network status update message to fleet  102  containing information about the change in the structure of communication network  106  so that the fleet members may update their respective network information tables  402 . 
     Off-board system  202  may be a computing system of a business entity associated with fleet  102 , such as a contractor, a manufacturer, a dealer, a retailer, an owner, a service provider, or any other entity that sends, receives, or stores information associated with the operation of fleet  102 . For example, off-board system  202  may belong to a worksite contractor or manager responsible for an excavation project taking place in environment  100 . Off-board system  202  may include, for example, a laptop or desktop computer, a personal digital assistant, a mainframe, or another computing system known in the art. Off-board system  202  may include any means for monitoring, recording, storing, indexing, processing, and/or communicating information. Such means may include a central processing unit (CPU), random access memory (RAM), read-only memory (ROM), a magnetic or optical storage device, a display device, a user input device, a network communication device, or other computing devices known in the art. Off-board system  202  may include communications hardware and software for communicating wirelessly with fleet  102  (e.g., via radio). Accordingly, off-board system  202  may transmit messages to, and receive messages from, fleet  102  to coordinate activities taking place in environment  100 . 
     As shown in  FIG. 5 , off-board system  202  may include a dispatch system  500  configured to leverage an excavation fleet server  502 , a haul fleet server  504 , and a utility fleet server  506 . Dispatch system  500  may transmit messages to, and receive messages from, fleet members via excavation fleet server  502 , haul fleet server  504 , and utility fleet server  506  to coordinate fleet operations. In order to facilitate such communication, dispatch system  500  may include or otherwise be associated with a network information database  505 , which may contain the same or similar information as that discussed above in connection with network information database  312  ( FIG. 3 ). Depending upon the configuration of fleet  102 , fleet operations may be autonomous, semiautonomous, or manual, and the fleet members may be manned or unmanned. For example, dispatch system  500  may automatically manage an excavation project according to a digital terrain map stored in memory and containing a description, in worksite coordinates, of desired worksite terrain. 
     Data gathered by fleet members during operation may be communicated via radio to dispatch system  500  for fleet coordination purposes. Such gathered data may include GPS positions, travel speeds and distances, payload values, fuel levels, engine speeds, scanned worksite terrain coordinates, waiting times, queuing times, loading times, round trip times, hauling times, status information (e.g., whether a fleet member is enabled/disabled, online/offline, loading/unloading, traveling, refueling, etc.), or other performance data valuable for coordinating fleet activities. Based on the gathered information, dispatch system  500  may monitor or log fleet operations taking place in environment  100 , dispatch or recall fleet members (e.g., for scheduled maintenance or repairs), route fleet members to loading and unloading destinations, reroute fleet members based on waiting times at the destinations, provide or update tasks to be performed by fleet members, or perform other fleet management operations. In addition, dispatch system  500  may calculate and log worksite metrics, such as fleet member efficiencies, overall worksite progress, and other information useful for evaluating the performance of fleet  102 . 
     As shown by  FIG. 5 , each of servers  502 - 504  may manage a different portion of fleet  102 . For example, excavation fleet server  502  may relay messages between dispatch system  500  and excavating fleet members  508  (e.g., excavators, dozers, loaders, mining shovels, etc.). Haul fleet server  504  may relay messages between dispatch system  500  and hauling fleet members  510  (e.g., dump trucks or loaders). Utility fleet server  506  may relay messages between dispatch system  500  and utility fleet members  512  (e.g., scrapers, pavers, fork lifts, etc.). It is to be appreciated, however, that other configurations for off-board system  202  are possible depending upon the particular configuration of fleet  102 . For example, a single fleet server may be responsible for all of fleet  102 . 
     As shown in  FIG. 5  and discussed above, communication network  106  may be hierarchical in nature. That is, communication network  106  may have multiple tiers or levels corresponding to different degrees of priority of fleet members contained therein. In the example shown in  FIG. 5 , communication network  106  includes first through fourth levels  514 - 520 . It is noted, however, communication network  106  may include any suitable number of levels, depending upon the particular implementation. The hierarchical structure of network  106  may be used, when a destination node is not within direct radio communication range of a source node, to impose structure on traffic on network  106  and thereby increase the reliability of network  106  and reduce consumption of network resources, such as available bandwidth. 
     First level  514  may include off-board system  202 , and may correspond to a “command” level having the highest degree of priority on communication network  106 . Similarly, second level  516  may have a higher degree of priority than third level  518 , and third level  518  may have a higher degree of priority than fourth level  520 . First level  514  may manage communications between excavating fleet members  508 , hauling fleet members  510 , utility fleet members  512 , or other branches of communication network  106  (not shown). For example, a message received from one of hauling fleet members  510  and destined for one of excavating fleet members  508  may first be received and processed by offboard system  202 . Off-board system  202  may then forward the message to excavating fleet members  508 . A message transmitted by off-board system  202  and destined for a particular fleet member may originate at first level  514 , and may sequentially propagate through subsequent levels  516 - 520  to reach its destination. 
     In  FIG. 5 , off-board system  202  in first level  514  is the supervisor of machines  522 - 530  in second level  516 . Machine  526  in second level  516  is the supervisor of machines  532 - 540  in third level  518 . Machine  534  in third level  518  is the supervisor of machines  542 - 546  in fourth level  520 . Accordingly, it is to be appreciated that communication network  106  may have a regimented or tiered priority configuration independent of the fleet members&#39; geographical location in environment  100 . 
       FIG. 6  illustrates an exemplary disclosed communication process  600  for communication network  106 . As discussed above, offboard system  202  may need to communicate with a particular fleet member in certain situations. For example, dispatch system  500  may need to send a message to recall a particular fleet member for scheduled maintenance.  FIG. 7  shows an exemplary configuration of a message  700  transmitted on communication network  106 . Message  700  may be a packet containing a source address  702 , a destination address  704 , a destination network level  706 , a destination identification number  707 , a command  708 , and a time-stamp  710 . 
     Source address  702  may be an address on communication network  106  address (e.g., IP address) of the source node (e.g., off-board system  202 ). Destination address  704  may be an address on communication network  106  (e.g., an IP address) of the destination node (e.g., a fleet member). Destination network level  706  may indicate the level of communication network  106  to which the destination node is assigned (e.g., level 4). Destination identification number  707  may include a number of the destination node within the network level to which it is assigned (e.g., machine  3 ). Command  708  may contain, for example, an instruction or other information to be processed by the destination node. Time-stamp  710  may indicate the time at which message  700  was generated or transmitted by off-board system  202 . 
     Returning to  FIG. 6 , off-board system  202  may broadcast message  700  to any fleet members within direct communication range (step  602 ). For example, excavation fleet server  502 , haul fleet server  504 , or utility fleet server  506  may broadcast message  700  via radio, and any fleet members within direct radio communication range may receive message  700 . It is noted that the broadcast may be an open broadcast, or may be a transmission only to select fleet members on certain channels (e.g., to particular IP addresses). 
     Any fleet member that receives message  700  may extract destination address  704  (step  604 ). The fleet member may then determine whether the extracted destination address is the same as its own address (step  606 ). For example, gateway  216  onboard the fleet member may compare the extracted destination address to network address  410  contained in machine information table  410  ( FIG. 4 ). 
     If the fleet member determines in step  606  that the extracted destination address is the same as its own address, the fleet member may process message  700  (step  608 ). For example, gateway  216  may extract command  708 . Protocol conversion module  304  may determine to which of onboard modules  204 - 214  command  708  is to be sent, and generate an onboard message containing command  708  and formatted appropriately for communication on bus  218 . Onboard communication module  300  may then transmit the onboard message on bus  218  via a data link port  308  associated with the onboard module. The onboard module may then extract the command and execute the message. Continuing with the recall message example above, the onboard message may be transmitted on a data link port  308  associated with navigation control module  214 . Navigation control module  214  may then extract and execute the command. For example, in the case of autonomous control, navigation control module  214  may reroute machine  104  to a maintenance facility indicated in the command. In the case of semi-autonomous or manual control, navigation control module  214  may display a message instructing the machine operator to bring machine  104  to the maintenance facility. 
     If the fleet member determines in step  606  that the extracted destination address is not the same as its own address, the fleet member may identify any fleet members within direct communication range of itself (step  610 ). Specifically, network communication module  306  may identify in machine information table  400  its own network address  410 . Network communication module  306  may then look up its network address  410  in column  422  of network information table  402 , and may identify any corresponding fleet members (i.e., network levels and identification numbers) listed in column  420 . Network communication module  306  may then look up in columns  412  and  414  the network levels and machine identification numbers, respectively, of the identified fleet members within direct communication range, and may identify and extract their corresponding network addresses listed in column  422 . 
     Next, the fleet member may determine whether the network address of any fleet member identified in step  610  is the same as the extracted destination address  704  (step  612 ). That is, the fleet member may determine whether the destination of message  700  is within direct radio communication range. Specifically, network communication module  306  may compare the network address of any fleet member identified in step  610  to the extracted destination address  704  and determine, based on the comparison, whether the network address of any fleet member identified in step  610  is the same as the extracted destination address  704 . If so, the fleet member may forward message  700  to destination address  704  (step  614 ). Specifically, off-board communication module  302  may forward message  700  to destination address  704  via open radio broadcast or via an off-board data link port  310  associated with the extracted destination address. 
     If it is determined in step  612  that the address of any fleet member identified in step  610  is not the same as destination address  704 , the fleet member may identify the supervisor of the destination (step  616 ). Specifically, network communication module  306  may look up destination address  704  in column  422 , and may identify the corresponding supervisor&#39;s network level and identification number listed in columns  416  and  417 , respectively. Alternatively, network communication module  306  may extract from message  700  destination network level  706  (e.g., level 3) and destination identification number  707  (e.g., machine  4 ). Network communication module  306  may then look up the extracted destination network level  706  and destination identification number  707  in columns  412  and  414 , respectively. Network communication module  306  may then identify the corresponding supervisor level network level and supervisor identification number listed in columns  416  and  417 , respectively. 
     The fleet member may then determine whether the supervisor of the destination identified in step  616  is within direct communication range (step  618 ). Specifically, network communication module  306  may look up the fleet member&#39;s own address  410  in column  422 , and may determine whether the supervisor network level and supervisor identification number identified in step  616  are listed in column  420  for the that address. Alternatively, network communication module  306  may look up the fleet member&#39;s own network level  404  and machine identification number  406  network level in columns  412  and  414 , respectively, and may determine whether the supervisor level and supervisor identification number identified in step  616  are listed in column  420 . If the supervisor level and supervisor identification number are listed in column  420 , network communication module  306  may determine that the supervisor of the destination is within direct communication range. If it is determined in step  618  that the supervisor of the destination is within direct communication range, the fleet member may forward message  700  to the supervisor (step  620 ) as discussed above. 
     If it is determined in step  618  that the supervisor of the destination is not within direct communication range, the fleet member may identify any peers of the destination (step  622 ). That is, the fleet member may identify any other fleet members in the same network level (e.g., level 3) as the destination. Specifically, network communication module  306  may look up extracted destination network level  706  in column  412  (i.e., network communication module  306  may look up all “level 3” fleet members), and may identify all corresponding machine identification numbers (e.g., machines  1 - 5 ) listed in column  414 . 
     The fleet member may next determine whether any peer of the destination identified in step  622  is within direct communication range (step  624 ). Specifically, network communication module  306  may look up the fleet member&#39;s own network address  410  in column  422 , and may determine whether any peer identified in step  622  is listed in column  420  for the address. Alternatively, network communication module  306  may look up the fleet member&#39;s own network level  404  and machine identification number  406  in columns  412  and  414 , respectively, and may determine whether a corresponding peer is listed in column  420 . If so, network communication module  306  may determine that the peer of the destination is within direct communication range. If it is determined in step  624  that a peer of the destination is within direct communication range, the fleet member may forward message  700  to that peer (step  626 ), as discussed above. 
     If it is determined in step  624  that no peer is within direct communication range, the fleet member may identify any peer of the supervisor of the destination (step  628 ). That is, the fleet member may identify any fleet members in the same level (e.g., level 2) as the supervisor of the destination. Specifically, network communication module  306  may look up the network level of the supervisor of the destination identified in step  616  in column  412  (e.g., all level 2 fleet members), and may identify all corresponding machine identification numbers listed in column  414 . 
     The fleet member may next determine whether any peer of the destination&#39;s supervisor identified in step  628  is within direct communication range (step  630 ). Specifically, network communication module  306  determine whether any peer of the destination&#39;s supervisor is listed in column  420 . If so, the network communication module  306  may determine that the peer of the supervisor of the destination is within direct communication range, and may forward message  700  to that peer of the supervisor of the destination (step  632 ) as discussed above. 
     If it is determined in step  630  that a peer of the destination&#39;s supervisor is not within direct communication range of the fleet member, the fleet member may determine that the destination is currently out of range (step  634 ). In addition, the fleet member may broadcast message  700  to any fleet member currently within direct communication range (step  636 ). Specifically, network communication module  306  may look up the fleet member&#39;s own network address  410  in column  422 , and may identify the network level and machine identification number of any corresponding fleet members listed in column  420 . Network communication module  306  may then look up the network levels and machine identification numbers of the identified fleet members within direct communication range in columns  412  and  414 , respectively, and may identify their corresponding network addresses listed in column  422 . Off-board communication module  302  may then forward message  700  to the network addresses as discussed above. 
     The fleet members to which message  700  is forwarded in step  636  may store message  700  in a mailbox associated with the destination until the destination is within communication range. For example, the fleet members may perform steps  604 - 636  discussed above until message  700  is delivered to the destination. 
     It is to be appreciated that a supervisor fleet member may, for one reason or another, go offline and therefore be unable to communicate. For example, a supervisor fleet member may travel outside of communication range of the rest of fleet  102 . Alternatively, the supervisor fleet member may malfunction technically. In such cases, the supervisees of that supervisor may be “cut-off” from communication network  106 . For example, referring to  FIG. 5 , if machine  534  goes off-line, its supervisees, machines  542 ,  544 , and  546 , may be cut-off from communication network  106 . 
       FIG. 8  shows an exemplary disclosed “promotion” process  800  that may be performed by off-board system  202  to rectify communication network  106  when such an event occurs. As discussed above, off-board system  202  may receive a message from fleet  102  indicating that a fleet member is off-line (step  802 ). The message may contain, for example, the network level and machine identification number of the off-line fleet member. Off-board system  202  may then analyze the message to determine whether the off-line fleet member is a supervisor (step  804 ) (i.e., whether it has any supervisees). For example, off-board system  202  may extract the network level and the number within the network from the message, and look up the off-line fleet member in network information database  505  ( FIG. 5 ) to determine whether the off-line fleet member has any supervisee fleet members. 
     If it is determined in step  804  that the off-line fleet member is not a supervisor, off-board system  202  may update network information database  505  to indicate that the off-line fleet member is no longer available (step  806 ), and may broadcast a network status update message (step  808 ). For example, referring to  FIG. 5 , if machine  546  has technical difficulties and therefore goes off-line, off-board system  202  may determine that the off-line fleet member is not a supervisor (i.e., it has no supervisees), and may update network information database  505  to reflect that machine  546  is no longer available. For example, off-board system  202  may delete an associated entry for machine  546  in network information database  505 . Off-board system  202  may then broadcast a message to fleet  102  indicating that machine  546  is no longer available. The fleet members may also update their own network information tables  402  to indicate that machine  546  is no longer available. 
     However, if off-board system  202  determines in step  804  that the off-line fleet member is a supervisor (i.e., it has supervisees), it may select one of the supervisees of the off-line supervisor for promotion (step  810 ). For example, referring to  FIG. 5 , if machine  534  goes off-line, off-board system  202  may access network information database  505  to identify its supervisees (i.e., machines  542 - 546 ). Off-board system  202  may then select one of the supervisees (e.g., machine  542 ) for promotion to supervisor. That is, off-board system  202  may select one of the supervisees to take the place of the supervisor (i.e., machine  534 ) in communication network  106 . This selection may be based on various factors, such as the machine types of the supervisees (e.g., haul truck, excavator, etc.), the functions performed by the supervisees, the current status of the supervisees, the geographical location of the supervisees (e.g., the locations of the supervisees in environment  100  and the surround terrain), available bandwidth on network  106 , etc. The promoted supervisee may have the remaining supervisees of the off-line fleet member (i.e., machines  544  and  546 ) as supervisees. 
     Off-board system  202  may then update network information database  505  to reflect the promotion (step  812 ). Specifically, off-board system  202  may update the promoted fleet member&#39;s network level and machine identification number stored in network information database  505  with that of the off-line fleet member. This may be accomplished by incrementing the promoted fleet member&#39;s network level by one (e.g., from level 3 to level 2) and by replacing the promoted fleet member&#39;s current machine identification number with that of the off-line fleet member. Off-board system  202  may also update network information database  505  to indicate that the off-line fleet member is no longer available for communication, as discussed above. 
     Upon completion of step  812 , off-board system  202  may determine whether the promoted supervisee is also a supervisor (step  813 ). That is, off-board system  202  may look up look up the promoted supervisee fleet member&#39;s network level and machine identification number in network information database  505  ( FIG. 5 ) to determine whether it has any supervisee fleet members. For example, referring to  FIG. 5 , supervisee machine  534  may be selected in step  810  for promotion, but may also have its own supervisee machines  542 - 546 . If it is determined in step  813  that the supervisee selected for promotion in step  810  is also a supervisor, off-board system  202  may return to step  810  to select one of the promoted supervisee&#39;s supervisees for promotion. That is, off-board system  202  may repeat step  810  with respect to the promoted supervisee. For example, if supervisee machine  534  has been selected for promotion, off-board system may select one of supervisee machines  542 - 546  for promotion (i.e., to take the promoted supervisee&#39;s position in communication network  106 ). Off-board system  202  may then repeat step  812  to update network information database  505  with respect to the promoted supervisee&#39;s supervisees. Accordingly, off-board system  202  may repeat the promotion process of steps  810 - 813 , working its way through network levels  518 - 520 , until no supervisors remain to be promoted, or until a supervisee which is not also a supervisor is promoted. 
     Once it is determined in step  813  that the promoted supervisee is not also a supervisor, off-board system  202  may broadcast a network status update message to fleet (step  814 ). The network status update message may indicate that the off-line fleet member is no longer available for communication. The network status message may also contain information about the promotion(s). The fleet members may then update their respective network information tables  402  to reflect the promotion(s) and to indicate that the off-line fleet member is no longer available. For example, the fleet members may update the promoted fleet member&#39;s network level and machine identification number stored in network information network information table  402  with that of the off-line fleet member, as described above. The fleet members may similarly update the network level and machine identification number of any subsequent fleet member promoted in steps  810 - 813 . Accordingly, during future communication on communication network  106 , the promoted supervisee may act as a substitute supervisor for the off-line fleet member. Likewise, any subsequent promoted supervisee may act as a substitute for the supervisor for which it was promoted to replace. 
     It is noted that the assignment of addresses of the fleet members on communication network  106 , and the layout of communication network  106  may be predetermined. For example, a network administrator may determine which fleet members are to be supervisors and supervisees, and network information databases  312 ,  505  may be preconfigured with this information. Accordingly, the fleet members may each have a static IP address and a predetermined network level and machine identification number on communication network  106  (e.g., level 3, machine  3 ). Off-board system  202  may alternatively allocate dynamic addresses to fleet members based on the available bandwidth on communication network  106 . It is to be appreciated, however, that any other suitable methods for assigning addresses on a network may be utilized. 
     INDUSTRIAL APPLICABILITY 
     The disclosed fleet communication network may be applicable to any communication network where a reliable architecture would be advantageous. By routing messages between sources and destinations according to various tiers of priority on the network when a destination is not within direct communication range, as disclosed, traffic on the network can be organized in a structurally reliable manner and network resources (e.g., bandwidth) can be conserved. In addition, the basic architecture of the network may remain intact irrespective of the geographical positions of the fleet members. Thus, the disclosed fleet communication network may be particularly useful in situations where the reliability of communications is an issue, such as in a network of an autonomous fleet of machines cooperating to accomplish a task. 
     Other embodiments of the disclosed methods and systems will be apparent to those skilled in the art upon consideration of the specification and practice of the disclosure. It is intended that the specification be considered exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.