Patent Publication Number: US-2007102998-A1

Title: Method and system for distributing power across an automotive network

Description:
RELATED CASES  
      This patent application is related to U.S. patent application Ser. No. 10/439,702, entitled “Power and Communication Architecture for a Vehicle,” filed May 16, 2003, which is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION  
      This invention relates to vehicles, and more particularly to a power architecture for a vehicle.  
     BACKGROUND OF THE INVENTION  
      Vehicles have been getting ever more complex with the advances in computer technology. Sensors are becoming more intelligent and actuators are becoming increasingly controlled by microcomputers. The number of microcomputers inside a vehicle has greatly proliferated, so that effectively each sensor or actuator, as well as the various interactive devices such as entertainment systems, all include microcomputers. Because of this proliferation, serial communication networks have been developed for use inside the vehicle to simplify overall operation. These exist according to various standards depending on both region and particular manufacturer. Nonetheless, a general communication architecture has been developed. However, power distribution throughout the vehicle has remained at existing levels of wiring and fusing arrangements, with complicated wire looms which are expensive to build, install and repair.  
      In the patent application referenced above, it was proposed to build a modular architecture for both communications and power, with various switching nodes to switch both the communications and the power. In this manner the wiring of a vehicle can be dramatically simplified to a few standardized links or cables based on particular power requirements, with each link having power and communication portions. While the architecture of the referenced patent application does provide significant benefits, the actual power distribution scheme was relatively simplistic in that each of the nodes would only monitor for faults and otherwise would simply provide power. As a result of this simplistic approach, each of the modules would effectively have to be designed for similar power levels, such as high power levels, and so would require expensive components. In many cases it would be more desirable to use lower cost components, i.e., for lower power applications, but the limited and simplistic design of the prior art system does not provide for this capability. Each portion of the system must be designed for a worst case maximum load environment, so lower cost improvements effectively can not be used. Therefore it would be desirable to be able to provide more control of the distribution of power within a node architecture in a vehicle to allow use of lower cost components. 
    
    
     DESCRIPTION OF THE FIGURES  
       FIG. 1  is an illustration of a vehicle indicating exemplary nodes and power wiring.  
       FIG. 2  is a simplified block diagram illustrating a first embodiment of nodes and switched power flow.  
       FIG. 3  adds standby power capabilities to the embodiment of  FIG. 2 .  
       FIG. 4  is a block diagram of a node useful in the architecture of  FIG. 2 .  
       FIG. 5  is a block diagram of a node, similar to  FIG. 4  except that standby power as used in  FIG. 3  has been incorporated.  
       FIGS. 6A-6D  are schematic diagrams of switching points contained in the nodes of  FIGS. 3 and 4 .  
       FIGS. 7A-7C  illustrate the network of  FIG. 2  with various fault conditions.  
       FIG. 8  is an illustration of the network of  FIG. 2  with alternate paths available at particular nodes.  
       FIG. 9  is a variation of  FIG. 2  with a dual power source arrangement.  
       FIG. 10  is a variation of  FIG. 2  with a high and low voltage source arrangement.  
       FIGS. 11A-11D  illustrate various load flows and load balancing capabilities of a system according to the present invention.  
       FIG. 12  illustrates an ordering hierarchy for use in fault detection according to the present invention.  
       FIG. 13  is a flow chart of initialization operations of an architecture according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PRESENT INVENTION  
      Nodes according to the present invention include additional sensing and communication capability as compared to prior nodes. The sensing capability allows determination of actual current flows through the particular nodes, including each port of the node, to allow a determination of power flow to better control operations. Because of this understanding of power flow, smaller modules or nodes can be utilized if desired. For protection of a lower power node, an upstream node can open the link to the node should it go overcurrent or otherwise fault. Further, with the additional sensing capability, actual load balancing and multiple controllable flows, such as for standby, can be developed. The additional communication in combination with the sensing also allows better fault isolation. By being able to determine the actual location of the fault, other operations in the vehicle can continue with just the faulty area being disconnected.  
      Referring now to  FIG. 1 , an illustration of a typical vehicle  100  is shown. A battery  102  forms the representative power source, it being understood that the actual power source would be some combination of a battery, an alternator and/or a super capacitor. Shown connected to the battery  102 , directly or indirectly, are a series of ovals which represent the various control and power nodes or modules in the vehicle  100 . These nodes can be complex, such as computing/switching/control nodes; intermediate, such as smart switches; or simple, such as sensors or actuators. Each node may have direct inputs and outputs to devices and switches which are not shown for simplicity. The complex nodes will have greater computing capacity and handle more complex tasks, while intermediate nodes have less computing capacity and handle simpler tasks. Simple nodes have the least computing capacity, effectively only enough to perform the required communication, and handle simple, usually digital, devices. For example, a powertrain control module (PCM)  104  is connected to the battery  102 . In conventional parlance the PCM  104  is a complex node and controls the engine and transmission of the vehicle  100 . The PCM  104  is connected to a dash entertainment and ventilation module  106 . The dash entertainment and ventilation module  106  is also a complex node and is typically behind the dash in the vehicle  100  and controls the various information, entertainment and heating and ventilation controls that are present in the dashboard. Further connected to the PCM  104  is a right front door node  108 . The right front door node  108 , for example, controls the power window, power mirror and door lock for the right passenger door. Connected to the right front door node  108  is an actuator  110  which is, for example, contained in the right front door to control the power window and door lock. A controller  109  is located in the right front door and connected to the right front door node  108  to allow the right front door node  108  to control the power mirror. A right rear door node  112  is connected to the PCM  104  through a switch node  111  and is also connected to an actuator  114  which controls the power window and lock. An engine compartment node  116  is connected to the PCM  104  and is also connected to actuator  118 . In addition, an actuator  120  is connected to the PCM  104  as are two controllers  122 .  
      In the illustrated vehicle  100 , a steering column node  124 , an intermediate node, is connected to the dashboard module  106 . A controller  126  is connected to the steering column node  124 , as is an actuator node  128 . A driver&#39;s side node  130 , also an intermediate node, is connected to the steering column node  124 . Controllers  132  and actuator node  134  are connected to the driver&#39;s side node  130 . Additionally connected to the driver&#39;s side node  130  is a front left door node  136 , which in turn receives a controller  138  and an actuator  140 . In addition, a left rear door node  142  is connected to the driver&#39;s side node  130  through a switch node  141  and is connected to an actuator  144 . The driver&#39;s side node  130  is also connected to the engine compartment node  116  to provide a parallel path for switching purposes.  
      The next major node in the vehicle is the body and ABS module  146 , which is a complex node and is connected to both the battery  102  in the illustrated embodiment and to the dashboard module  106 . An airbag control node  148  is connected to the body and ABS module  146  to perform the airbag functions necessary in the car. A roof node  150  is also connected to the body and ABS module  146  to control items such as the sunroof and the lighting and to that end an actuator  152  is connected to the roof node  150 . Various other actuators  154  and  156  are connected to the body and ABS module  146 . Controllers  158  and  160  are also connected to the body and ABS module  146 , for example to control the power seats. A fuel node  162 , an intermediate node, is further connected to the body and ABS module  146  and is connected to a controller  164 , which may be a fuel pump for example. A rear body node  166  is connected to the fuel tank node  162  and links to an actuator  168  to control, for example, the rear lamps. The fuel tank node  162  is also connected to the switch nodes  111  and  141  to provide additional parallel paths.  
      An actuator  170  and controllers  172  are also connected to the dashboard module  106 .  
      Each of the links between the particular nodes or modules is uniform in a first embodiment and includes a power cable, a ground cable and communications cables, as necessary, for the particular communication protocol. The links between the various nodes, actuators and controllers would also be similar in that they would contain power, ground and communications links though, in some embodiments of the present invention, the links could have different size power and ground conductors, for example, in that a sensor may require less power than an actuator node and various actuator nodes could require less power than other actuator nodes. In alternate embodiments, power line communications technique are used, so the links include only power and ground cables, the communications signals being provided over the power cable.  
      Thus it can be seen that a switching network is developed in the vehicle for both communications and power.  
      This switching network for power is more clearly seen in  FIG. 2 . The battery  102  is connected to a first illustrative node  200 . The node  200  is similar to the nodes illustrated in  FIG. 1  but in this case is shown in a simplified format. Each illustrated node has four ports to receive cables to form links. The battery  102  is connected to node  200  at a first input port. A second node  204  is connected to a second port of the node  200  at its own first port. In turn, an additional node  210  is connected to the second port of the node  204  at its own first port. Similarly, a node  212  is connected to a third port of the node  200  through its first port. Then a node  214  has its first port connected to a second port of the node  212 . An exemplary load  216  is connected to the node  210  and a load  218  is connected to the node  214 . Thus, in the example of  FIG. 2 , power flows from the battery  102  through node  200  to node  204  to node  210  and to the load  216 . Similarly, power flows from the battery  102  through the node  200  through the node  212  and through the node  214  to the load  218 .  
       FIG. 3  is similar to  FIG. 2  except that a standby voltage source  300  has been connected to each of the nodes  200 ,  204 ,  210 ,  212  and  214 .  
      A block diagram of a node as used in  FIG. 2  is shown in more detail in  FIG. 4 . A node  400  contains various components. For example, the node  400  contains first, second, third and fourth power connections  402 ,  404 ,  406  and  408 . The node  400  contains data connections  410 , which preferably includes four connections, one to be paired with each power connection, each connection including various conductors as appropriate for the communications network. The node  400  contains a ground connection  412 , which is generally tied to vehicle ground and also preferably paired with the power connections so that four ports are developed for the node  400 . In the embodiment of  FIG. 4 , the node  400  not only provides power and communication switching capabilities, it also has the capability to provide and directly drive loads. Thus a first load  414  is connected to the node  400 . As this is a highside load, both sides of the load  414  are connected to the node  400 , one to receive power and one to a lowside driver  434 . For a lowside load  416 , the lowside load  416  is simply connected directly to a highside driver  432  in the node  400 , with the other connection of the load  416  being connected to ground.  
      Each of the power connections  402  to  408  is connected to power switches  422 ,  424 ,  426  and  428 . While these will be described in more detail below, effectively these are switching points to control power flow, either power into or power out of, or in some cases both, of the particular connection. The second power sides of the four switches  422 - 428  are connected together to form a central power point or bus  430 . This central power point  430  is connected to the highside load  414  and to the highside driver  432 . A voltage regulator  436  is connected to the central power point  430  and to ground  412  to provide a controlled voltage environment for the node  400 . Finally, a microcontroller  438  is connected to the various power switches  422 ,  424 ,  426  and  428 , the voltage regulator  436  and the drivers  432  and  434 , as well as the data connections  410  to provide overall communication and control capability to the node  400 . Each switch  422 ,  424 ,  426  and  428  further has a sense connection to the microcontroller  438 , preferably through an analog to digital interface, and has a control or switch connection to the microcontroller  438  to allow control of the operation of the switches  422 ,  424 ,  426  and  428 .  
      If power line communications are used, the external data connections  410  are not present, but an interface module is present and is connected between the respective power connection and the microcontroller  438 .  
       FIG. 5  similarly shows a node  500  with like parts from node  400  being similarly numbered. The addition to the node  500  is a standby connection  502  to receive the standby voltage from the standby voltage source  300 . This standby voltage connection  502  is connected to the voltage regulator  436  to provide an alternate source of voltage to the node  500  when the main battery  102  is not coupled to the node  500 .  
       FIGS. 6A-6D  are more detailed drawings of the switches  422 ,  424 ,  426 ,  428 . The differences between the  FIGS. 6A-6D  are in capabilities of the particular functions of the switch node.  FIG. 6A  is a simplified schematic version, with just a transistor  600  in series with a sense resistor  602 , with the current sense being measured across the sense resistor  602  and the transistor  600  having a control or gate input  608 . This simple switch format is useful in many cases, particularly those where the actual node will only be a downstream device and the only items downstream are actuators, with no situations for reverse flows of power. A power input terminal  606  is connected to connection  402  and a power output terminal  604  is connected to the central power point  430 , for example.  
       FIG. 6B  is a more detailed schematic of the switch of  FIG. 6A .  FIG. 6B  includes primarily more details on the control or gate circuitry. The base of an NPN transistor  610  is connected to the control input  608  through a series resistor  612 . A resistor  614  is connected from the base of the transistor  610  to ground and to the emitter of the transistor  610 . The collector of the transistor  610  is connected to the output power terminal  604  through a resistor  616  to provide pull up capability. The collector of the transistor  610  is also coupled through the series of connection of resistors  618  and  620  to the drain terminal of the transistor  600  and to one end of the current sense resistor  602 . The connection point between the resistors  618  and  620  is connected to the gate input of the transistor  600 . As before, the source of the transistor  600  is connected to the power input terminal  606 . A capacitor  622  is connected between the power input terminal  606  and ground to provide filtering.  
       FIG. 6C  is a similar detailed schematic of a switch. The switch of  FIG. 6C  is slightly different from that of  FIG. 6B  in that the current sense lines are developed in a slightly different format. Instead of taking signals from both sides of the sense resistor  602 , in the embodiment of  FIG. 6C  ground-referenced voltage levels from the input and output sides are provided. On the power input side a first resistor  640  has an end connected to the power input terminal  606  and the source of the transistor  600 . The other end of resistor  640  is connected to one end of a resistor  642 , which is also connected to ground. The connection point of the resistors  640  and  642  is one signal of the pair used for current sensing. In one embodiment of the present invention, a Zener diode  644  is connected across the resistor  642  for protection purposes, as is a capacitor  646 . A resistor  648  has one end connected to the power output terminal  604  and the second end connected to the first end of a resistor  650 , whose second end is connected to ground. A Zener diode  652  is connected in parallel with the resistor  650 . As before, the connection point between the resistors  648  and  650  is one portion of the I or current sense signal, so that the actual sensing for current flow through the switch is determined by measuring the voltage difference between the two current sense signals, there being a predetermined amount of resistance between the power input terminal  606  and power output terminal  604 .  
      While the embodiments of  FIG. 6A-6C  were simple embodiments which are generally used for more downstream applications, the embodiment of  FIG. 6D  provides full input and output power control. The switch  654  of FIG.  6 D has a common power connection  656 , which would be connected to central power point  430  in the node of  FIG. 4 , for example. It also has an input or output (I/O) power connection  658 , which for example would be connected to connection  402  on the node  400 . A ground connection  660  is provided. As both input and output control are available on the switch  654 , output control connection  662  and input control connection  664  are provided. Similarly, there is an output current sense signal  666  and an input current sense signal  668 . In one embodiment, highside power switches  670  and  672  such as the BTS  6143 D are used in place of the simple FETs illustrated in  FIGS. 6A-6C . The VBB or supply voltage input to this switch  670  is connected to the common power connection  656 . The VBB or supply voltage input of the switch  672  is connected to the I/O power connection  658 . The output voltage signals of the two switches  670  and  672  are connected together. Further connected to this common point are a pair of Schottky diodes  674  and  676 . The anodes of the two diodes  674  and  676  are connected to the outputs of the switches  670  and  672 . The cathode of the diode  674  is connected to the common power connection  656 , while the cathode of the diode  676  is connected to the I/O power connection  658 .  
      The output control connection  662  is provided to one side of a resistor  678  and the second side is connected to one side of a resistor  680  and the base of an NPN transistor  682 . The second side of the resistor  680  is connected to the emitter of the transistor  682  which is connected to ground. The collector of the transistor  682  is connected to the control input connection of the switch  670 .  
      The input control of the switch  672  is more complicated because of the need to supply power to the microcontroller  438  even though the input power is disabled. The input control connection  664  is connected to the first end of a resistor  684  whose second end is connected to the first end of a resistor  686  and the base of an NPN transistor  688 . The emitter of the transistor  688  and the second end of the resistor  686  are connected to ground. The collector of the transistor  688  is connected to one end of a resistor  690 , whose second end is connected to the I/O power connection  658 . A resistor  692  has one end connected to the I/O power connection  658  and the second end connected to a voltage sense connection  694 . The voltage sense connection  694  is also connected to one end of the capacitor  696 , whose other side is connected to ground. Further, the voltage sense connection  694  is connected to one end of a resistor  698  whose second end is connected to the collector of an NPN transistor  700  and one end of a resistor  702 . The second end of the resistor  702  and the emitter of the transistor  700  are connected to ground. The collector of the transistor  700  is connected to the first end of a resistor  704 , whose other end is connected to the I/O power connection  658 . The collector of the transistor  700  is also connected to one end of a resistor  706 , whose second end is connected to the base of an NPN transistor  708  and one end of a resistor  710 . The second end of the resistor  710  and the emitter of the transistor  708  are connected to ground. The collector of the transistor  708  is connected to the collector of the transistor  688 . This collector connection is also connected to one end of a resistor  712  whose second end is connected to the base of an NPN transistor  714  and one end of a resistor  716 . The second end of the resistor  716  is connected to the emitter of the transistor  716  and is connected to ground. The collector of the transistor  714  is connected to the control input of the switch  672 .  
      The circuit can be simplified to just the resistors  712  and  716  and transistor  714  if the schematic of  FIG. 4  is modified to include diodes bypassing the switches  422 - 428  to provide power to the voltage regulator  436 .  
      The output current sense connection  666  is connected to the current sense pin of the switch  670 , which is connected to one end of a resistor  718 , which has its other end connected to ground. Similarly, the input current sense connection  668  is connected to the current sense pin of the switch  672  and connected to one end of a resistor  720 , whose other end is connected to ground.  
      With the switch  654  properly controlling the input and output control connections  662  and  664 , this allows full bidirectional control of power flow through the switch if desired, rather than the one-way flow of the prior switch embodiments.  
      It is understood that  FIGS. 6A-6D  are specific embodiments and there are many other possible embodiments.  
       FIGS. 7A, 7B  and  7 C show three different fault conditions for the network of  FIG. 2 . In  FIG. 7A , there is a fault to ground at the load  216 . In  FIG. 7B  the node  210  itself has a fault to ground, while in  FIG. 7C  the link connecting nodes  204  and  210  is faulted to ground. By properly monitoring the various load currents in the various locations, such as the output power ports of switch nodes  204  and  210 , a determination of the location of the fault can be developed. As there is a switched communication path between all nodes, with the microcomputer  438  in each node performing the data switching function, the various nodes can communicate their fault conditions to each other to determine the fault location. Once the location is determined, then the appropriate switch can be turned off via node  204  or node  210  to alleviate the problem.  
       FIG. 8  illustrates a link between the nodes  210  and  214  to allow multiple routing of power in the case of a fault. For example, should node  204  fail or the links to and from node  204  fail, power can ultimately in this case be routed from node  214  to node  210 , rather than having node  210  rely only on node  204  for its power source. This use of interconnection and redundant connections provides great redundancy and failover capabilities for the network. Several examples of these redundant or parallel connections are provided in  FIG. 1 .  
       FIG. 9  has an exemplary second battery  900  connected to the node  210  so that two batteries i.e., two power sources as discussed above, are present in the network of  FIG. 9 . In this case power can then flow from node  210  to node  204 , if desired, instead of flowing only from node  200 . Alternatively, the link between nodes  200  and  204  can become a redundant link and utilized if there is a failure in the battery  900 , the node  210  or the links between them.  
      In  FIG. 10 a  battery  902  connected to node  210  is noted as being at a lower voltage, such as six volts. This provides standby capability or multiple voltage operation if desired. For example, if full power operation was over and the vehicle was turned off, a backup or standby power capacity could be developed using the battery  902  by properly rerouting the power flow to be from battery  902  instead of battery  102  by enabling the proper nodes.  
      One major advantage of the nodes of the present design is the capability to power balance and to reroute power in case of failures.  FIGS. 11A, 11B ,  11 C, and  11 D illustrate various aspects of power balancing and rerouting. In  FIG. 11A , the battery  102  is providing a total of 38 amps to node  1100 . Two amps are used by node  1100 , either internally or to components directly connected to node  1100 . Eighteen amps are then provided to node  1102 , which uses three amps and provides the remaining fifteen amps to node  1104 . Node  1104  uses ten amps and provides the remaining five amps to node  1106 . Eighteen amps are also provided from node  1100  to node  1108 , which uses ten amps and provides eight amps to node  1110 . Node  1110  uses the eight amps it receives from node  1108 . No current flows in the links from node  1108  to node  1104  and from node  1110  to node  1106 , so these links are switched off or opened.  
      In  FIG. 11B  the loads used at the various nodes change. Node  1102  now uses seventeen amps, node  1104  uses five amps, node  1106  uses three amps, node  1108  uses five and node  1110  uses six amps. To keep the flows from node  1100  balanced, seventeen amps are provided from node  1100  to node  1102 , with nineteen amps from node  1100  to node  1108 . No current can be provided from node  1102  as it uses all seventeen amps it receives. Instead, node  1104  receives eight amps from node  1108 , over the previously unused link. Node  1104  then provides three amps to node  1106 . Node  1108  provides the remaining six amps to node  1110 . Now, the link between nodes  1102  and  1104  is unused and can be opened. As can be seen, the load flows in the network have been changed to remain substantially balanced.  
      In  FIG. 11C , it is assumed that either nodes  1104  or  1110  can provide five amps to an actuator. Normally the power is supplied from node  1104  but in  FIG. 11C , node  1104  is treated as having failed, so node  1110  must begin driving the actuator and also providing power to node  1106 . As a result, the load flows change to have the additional five amps flow from node  1108  to node  1110  for the actuator and an additional three amps for node  1106 . Thus this first failover situation is readily handled by the network.  
      In  FIG. 11D , node  1102  is also connected to the battery  102 . Thus the eighteen amps from node  1100  to node  1102  in  FIG. 11A  is provided directly from the battery  102  so that the link between node  1100  and node  1102  carries no power and can be opened.  
      Loads carried over a link and provided to the various devices can be determined several ways and then are used to perform the load balancing. The most direct way is by monitoring the current at each port using the current sense capabilities of each switch and then summing the results to determine internal current consumption. Detection for individual loads can be done by momentarily strobing the load and monitoring current during the on and off periods. Additionally, changes can be monitored as loads are activated, thus allowing a direct reading.  
      Ultimately each load can be determined by each node and the results provided to a primary control node. This node will know the topology of the network and be able to instruct the proper nodes to enable or disable selected ports.  
      The current distribution can be determined in several manners. As one example, a full true analysis can be performed for all possible arrangements. As a second example, a trial and error approach can be used where links are activated or deactivated and the resulting current balance measured until a desired balance is achieved. Other techniques known to those in the art, such as a variation on Dijkstra&#39;s algorithm where currents are the weighting factors or others, may be used as well.  
      This power routing can also be done dynamically by each node providing messages to the primary node before turning loads on or off, thus allowing the primary node to prepare for load increases or decreases. Alternatively, each node can periodically repeat the load calculations discussed above.  
       FIG. 12  illustrates a hierarchy of nodes to enable improved fault detection and containment. In one embodiment of the present invention, nodes which are directly connected to the battery are considered source nodes and have the highest hierarchal number. Nodes directly connected to those nodes have a lower hierarchal number and so on until you reach nodes which are the farthest from the source nodes and the battery. To perform fault isolation, control actions are taken, first at the farthest nodes, i.e., those with the lowest hierarchy number, to determine if containment can be developed at that level. Containment moves back one hierarchy level at a time to determine the node which can correct or alleviate the fault with the least number of other side effects. This is preferably done by delaying the trip time after detecting a fault by a factor based on the hierarchy level of the node. Alternatively, as discussed above, the various nodes can also pass fault messages over the communication network to try and isolate the fault based on sensed fault information.  
      Fault detection can occur in various manners. The most direct is by sensing currents over a given limit to indicate a downstream fault. An internal or directly connected fault can be determined by summing currents into and out of the node and determining if the difference exceeds the expected directly connected and internal loads. Profiling can be used, where the turn on and off characteristics of a load are monitored for deviations from normal. Of course, other methods as known to those in the art can be used.  
      Because this is a distributed network generally powered from a single power source with power being delivered through the switching components, it is necessary to have a power initialization protocol. A simple protocol or flowchart is shown in  FIG. 13 . In step  1300  power is applied to a node, such as when the battery is connected or the vehicle is turned on. In step  1302  the node determines if there are power source ports connected to the node, i.e., which of the ports on the node are receiving power. Further, a determination is made whether the vehicle is in a standby or run status. Control proceeds to step  1304  where a check for faults occurs. This can be done by the techniques discussed above. In step  1306  when run voltage is detected, discovery of the data network is done by sending queries or messages on each of the data links and awaiting responses. After all responses have been received and the connections known, routing tables are developed to allow messages to be passed between the sensors, actuator and nodes. Upon initialization of the primary node, in one embodiment the node closest to the battery and with the lowest module number if two are equally distant, the primary node receives responses from each of the subservient or non-source nodes in step  1308 . The responses include the power requirements of each node, that is, the power being directly supplied by the node itself. This is used in determining power routing and sharing. In step  1310 , when all of the nodes have responded with their power requirements, a power routing and sharing calculation is performed in step  1312 . The redundant power routes at this time are inhibited to stop potential circulating loop problems, and so on. In step  1314  a signal is provided that the network is ready to start so that the vehicle operations can begin. In step  1316  the various other applications or modules present in the vehicle initialize and communicate their successful startup. In step  1318  each of the nodes performs periodic power rediscovery to determine if the source of power has changed and to perform more fault checking to determine if a fault has developed. Once the network has completed the checking of step  1318 , control returns to step  1318  on a periodic basis.  
      While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.