Abstract:
An aircraft communication system for performing communication between each of a plurality of devices installed in an aircraft, wherein the communication system is provided with a plurality of communication processing units provided corresponding to the plurality of devices and a plurality of communication lines for connecting between the communication processing units, the plurality of communication processing units being capable of bidirectional communication via the plurality of communication lines. Upon receiving a plurality of communication data from the plurality of communication lines, one of the communication processing units determines, on the basis of identification information included in the received plurality of communication data, whether the received plurality of communication data needs to be acquired and acquires the communication data determined to need to be acquired.

Description:
RELATED APPLICATIONS 
     The present application is a National Phase entry of International Application No. PCT/JP2013/083053, filed Dec. 10, 2013, which claims priority of Japanese Application No. 2013-006482, filed Jan. 17, 2013. 
     TECHNICAL FIELD 
     The present invention relates to an aircraft communication system, an aircraft communication method, and a communication device. 
     BACKGROUND ART 
     Conventionally, fly-by-wire flight control system is known as an aircraft communication system (for example, see PTL 1). This fly-by-wire flight control system has multi-redundant configuration in which three independent data buses are included in order to fly the aircraft safely. Various devices such as three primary flight computers and three actuator control electronics (ACEs) are connected to the three data buses, respectively. 
     CITATION LIST 
     Patent Literature 
     [PTL 1] Japanese Unexamined Patent Application 
     SUMMARY OF INVENTION 
     Technical Problem 
     Another communication system used in aircraft is, for example, an avionics full-duplex switched Ethernet (AFDX (registered trademark)). The AFDX has dual redundant configuration in which two data buses are included. In AFDX, various devices are connected to the two data buses, and are able to perform bidirectional communication (transmission and reception) via the respective data buses. When transmission and reception of the communication data are performed between the various devices using the AFDX, the communication data is transmitted and received using the two data buses. Thus, in the aircraft communication system as disclosed in PTL 1 or such as the AFDX, multi-redundancy is achieved. 
     Meanwhile, in a communication system, different degree of redundancy may be set depending on devices. That is, the communication system may have configuration in which dual redundancy and triple redundancy co-exist. In this case, the communication system is designed to be configured according to the redundancy of the devices. In this case, in the communication system described in PTL 1, from the fact that the various devices are connected to the data buses, there is a possibility that it is necessary to redesign the device itself according to the design of the communication system. Further, the AFDX can handle only dual redundancy, and thus, it is difficult to secure triple or more redundancy. Therefore, devices may be affected by the design of communication system, and it is difficult to design a communication system suitable to the redundancy. 
     Therefore, objective of the present invention is to provide an aircraft communication system, an aircraft communication method, and a communication device, capable of achieving multi-redundancy and easily applicable to a design of a communication system while securing reliable transmission and reception of communication data. 
     Solution to Problem 
     An aircraft communication system of the present invention is an aircraft communication system that performs communication between respective devices of an aircraft on which a plurality of devices are mounted, the aircraft communication system including: a plurality of communication processing units provided corresponding to the plurality of devices; and a plurality of communication lines connecting between the respective communication processing units, in which the plurality of communication processing units are able to perform bidirectional communication via the plurality of communication lines, and when the communication processing unit receives a plurality of pieces of communication data from the plurality of communication lines, the communication processing unit determines whether the plurality of pieces of received communication data are to be acquired based on identification information included in the plurality of pieces of received communication data, and acquires the communication data determined to be acquired. 
     According to this configuration, the communication processing unit can acquire necessary communication data among the plurality of pieces of the received communication data based on the identification information included in the communication data. In this case, redundancy is realized between the communication processing units by the plurality of communication lines, and highly reliable communication data is acquired from among the plurality of pieces of the communication data, and thus, it is possible to secure the reliability of the communication data. Further, since the communication line is appropriately provided according to the degree of redundancy set in the device, and the communication line and the communication processing unit may be appropriately connected, it is possible to easily cope with the set degree of redundancy without affecting the device. 
     In this case, it is preferable that the communication data includes a sequence number that is information regarding order of the communication data, and the communication processing unit determines whether each piece of communication data is newer than previously received communication data based on the sequence number included in the received communication data, and acquires the communication data determined to be new. 
     According to this configuration, the communication processing unit can acquire new communication data. Therefore, the communication processing unit can transmit the new acquired communication data to the device, and thus, the device can perform control based on the new communication data. 
     In this case, it is preferable that, when the communication processing unit receives a plurality of pieces of the communication data determined to be newer than the previously received communication data, the communication processing unit acquires the first received communication data. 
     According to this configuration, the communication processing unit can acquire the first received communication data among the plurality of pieces of the communication data determined to be new. Therefore, since the communication processing unit can transmit the first received communication data to the device, the device can execute the control more rapidly based on the communication data. 
     In this case, it is preferable that the identification information included in the communication data or configuration data for reception stored in the communication processing unit includes communication line identification information in which the communication data and the communication line are associated with each other, and when there is communication data determined to be erroneous, the communication processing unit detects that the communication line associated with the communication data determined to be erroneous is abnormal based on the communication line identification information. 
     According to this configuration, the communication processing unit can detect the abnormality of the communication line based on the communication line identification information. Therefore, it is possible to rapidly take appropriate measures for the communication line detected to be abnormal. Further, the configuration data for reception is data set in advance (configuration data) in order to acquire predetermined communication data from among the plurality of pieces of the received communication data. 
     In this case, it is preferable that the communication data or configuration data for reception stored in the communication processing unit includes information regarding set reception status in which reception status from the plurality of communication lines used for communication of the communication data has been set in advance, and when the set reception status and actual reception status of the communication data from the plurality of communication lines are different, the communication processing unit detects that there is abnormality. 
     According to this configuration, if the set reception status is different from the actual reception status, the communication processing unit can detect that there is abnormality in any one of the plurality of communication lines. More specifically, the reception status is the number of reception paths via which the communication data is received from the plurality of communication lines, and when the actual number of reception paths is smaller than the set number of reception paths, the communication processing unit detects that there is abnormality in any one of the plurality of communication paths. Therefore, it is possible to rapidly take appropriate measures to solve the abnormality of the communication system. Further, the reception status is not limited to the number of reception paths. 
     In this case, it is preferable that the communication data includes an error detection code for detecting whether the communication data has been destroyed, and the communication processing unit determines whether the plurality of received pieces of communication data have been destroyed based on the error detection code included in the plurality of pieces of the received communication data, and acquires the communication data determined not to have been destroyed. 
     According to this configuration, the communication processing unit can acquire the communication data that has not been destroyed. Therefore, the communication processing unit transmits the acquired non-destroyed communication data to the device, and thus, the device can accurately execute control based on the communication data. Further, the error detection code includes, for example, a cyclic redundancy check (CRC). 
     In this case, it is preferable that, when the communication processing unit receives device status data that is data regarding status of the device from the corresponding device, the communication processing unit generates a plurality of pieces of the communication data including the identification information corresponding to the plurality of communication lines based on the received device status data, and transmits the plurality of generated pieces of the communication data to the plurality of communication lines. 
     According to this configuration, the communication processing unit can transmit the plurality of pieces of the communication data to the plurality of communication lines. Therefore, the communication processing unit can transmit the device status data of the corresponding device to another communication processing unit. 
     In this case, it is preferable that the communication data or the configuration data for reception stored in the communication processing unit includes information regarding a survival period of the communication data, and when the communication processing unit or the device connected to the communication processing unit does not acquire the communication data within the survival period, the communication processing unit or the device detects that there is abnormality. 
     According to this configuration, when the communication processing unit or the device does not acquire the communication data within the survival period, the communication processing unit or the device can detect abnormality. Therefore, it is possible to rapidly take appropriate measures to solve the abnormality of the communication system. 
     In this case, it is preferable for the communication processing unit to be provided in the device. 
     According to this configuration, the processing unit provided in the device can function as the communication processing unit. That is, software capable of causing the processing unit to function as the communication processing unit is executed by the processing unit of the device, and thus, the processing unit can be realized as the communication processing unit. 
     In this case, it is preferable for the communication processing unit to be provided in a separate communication device to be connected to the device. 
     According to the configuration of this embodiment, since the device and the communication processing unit can be separate, it is possible to clearly isolate the configuration of the device and the configuration of the communication system. Further, since the communication device can be configured as a dedicated communication device of the communication processing unit, it is possible to improve processing speed of the communication. 
     An aircraft communication method of the present invention is an aircraft communication method using a communication system that performs communication between respective devices of an aircraft on which a plurality of devices are mounted, in which the communication system includes a plurality of communication processing units provided corresponding to the plurality of devices; and a plurality of communication lines connecting between the respective communication processing units, and the plurality of communication processing units are able to perform bidirectional communication via the plurality of communication lines, and the aircraft communication method includes: a reception process of receiving, by the communication processing unit, a plurality of pieces of communication data from the other communication processing unit via the plurality of communication lines; an acquisition determination process of determining, by the communication processing unit, whether the plurality of pieces of received communication data are to be acquired based on identification information included in the plurality of pieces of received communication data; and a data acquisition process of acquiring, by the communication processing unit, the communication data determined to be acquired. 
     According to this configuration, the communication processing unit can receive a plurality of pieces of the communication data in the reception process, the communication processing unit can determine whether each piece of communication data is to be acquired in the acquisition determination process, and the communication processing unit can acquire the necessary communication data in the data acquisition process. In this case, redundancy is realized between the communication processing units by the plurality of communication lines, and highly reliable communication data is acquired from among the plurality of pieces of the communication data, and thus, it is possible to secure the reliability of the communication data. Further, since the communication line is appropriately provided according to the degree of redundancy set in the device, and the communication line and the communication processing unit may be appropriately connected, it is possible to easily cope with the set degree of redundancy without affecting the device. 
     A communication device of the present invention is a communication device provided in a communication system that performs communication between respective devices of an aircraft on which a plurality of devices are mounted, the communication device including: a plurality of transmission and reception units to which a plurality of communication lines are connected and that are able to bidirectionally transmit and receive communication data between the plurality of communication lines; and a communication processing unit connected to the plurality of transmission and reception units, and processing the communication data, in which when the communication processing unit receives a plurality of pieces of the communication data from the plurality of communication lines via the plurality of transmission and reception units, the communication processing unit determines whether the plurality of pieces of received communication data are to be acquired based on identification information included in the plurality of pieces of received communication data, and acquires the communication data determined to be acquired. 
     According to this configuration, since a separate communication device can be connected to a device to configure the communication system, it is possible to clearly isolate the configuration of the device and the configuration of the communication system. Further, since the communication device can be configured as a dedicated communication device for the communication processing unit, it is possible to improve processing speed of the communication. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a conceptual diagram illustrating a conceptual configuration of an aircraft communication system according to the present embodiment. 
         FIG. 2  is an illustrative diagram regarding a frame format of communication data. 
         FIG. 3  is an illustrative diagram of configuration data for reception. 
         FIG. 4  is a flowchart of an example regarding an aircraft communication method according to the present embodiment. 
         FIG. 5  is a flowchart of an example regarding an aircraft communication method according to the present embodiment. 
         FIG. 6  is a flowchart of an example regarding an aircraft communication method according to the present embodiment. 
         FIG. 7  is a block diagram of an example of an aircraft to which a communication system according to the present embodiment has been applied. 
         FIG. 8  is a schematic diagram of a communication device of the communication system according to the present embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. Further, the present invention is not limited to the embodiments. Further, components in the embodiments below include simple components that can be easily replaced by those skilled in the art, or substantially the same components. 
     Embodiments 
       FIG. 1  is a conceptual configuration diagram illustrating a conceptual configuration of an aircraft communication system according to the present embodiment. A plurality of devices  5  are mounted on an aircraft, and a communication system  1  communicates with each device  5  mounted on the aircraft. The communication system  1  has a redundant configuration in order to realize safe flight of the aircraft. First, a conceptual configuration of the communication system  1  of the aircraft will be described with reference to  FIG. 1 . 
     The communication system  1  includes a plurality of communication processing units  11  provided corresponding to the plurality of devices  5 , and a plurality of communication lines  12  that connect the respective communication processing units  11 . The communication system  1  has a configuration in which the communication data D is transmitted and received from the communication processing unit  11  to the other communication processing unit  11  via the plurality of communication lines  12 , and bidirectional communication is possible between the respective communication processing units  11 . Thus, the communication system  1  has a simple master-less configuration in which a master server is not provided. Accordingly, analysis of failure of the master server is unnecessary in this configuration. 
     Here, as illustrated in  FIG. 1 , the plurality of devices  5  mounted on the aircraft are configured to have different degrees of redundancy. Specifically, in the device  5   a  shown on an upper left side and the device  5   b  shown on the lower left side among the four devices  5   a ,  5   b ,  5   c , and  5   d , the degree of redundancy is set to be triple redundancy, and in the device  5   c  shown on an upper right side and the device  5   d  shown on the lower right side, the degree of redundancy is set to be dual redundancy. 
     The plurality of communication processing units  11  are connected to the plurality of corresponding devices  5 , respectively, and have a redundancy corresponding to the redundancy of the devices  5  to which the communication processing units  11  are connected. Here, for the plurality of communication processing units  11 , four communication processing units  11  are provided corresponding to the four devices  5   a ,  5   b ,  5   c , and  5   d . The communication processing unit  11   a  corresponding to the device  5   a  has a configuration in which triple redundancy is possible, that is, three communication lines  12  are connectable. Similarly, the communication processing unit  11   b  corresponding to the device  5   b  has a configuration in which triple redundancy is possible, that is, three communication lines  12  are connectable. Meanwhile, the communication processing unit  11   c  corresponding to the device  5   c  has a configuration in which dual redundancy is possible, that is, two communication lines  12  are connectable. Similarly, the communication processing unit  11   d  corresponding to the device  5   d  has a configuration in which dual redundancy is possible, that is, two communication lines  12  are connectable. 
     Each communication processing unit  11  performs a process for generating a plurality of pieces of the communication data D to be transmitted to the plurality of communication lines  12  to be connected thereto. Further, the communication processing unit  11  processes the plurality of pieces of the communication data D received from the plurality of communication lines  12  to be connected thereto. Further, in  FIG. 1 , while the communication processing unit  11  has a separate configuration to be connected to the device  5 , the communication processing unit  11  may have a configuration provided inside the device  5 . That is, the communication processing unit  11  may be provided inside a communication device connected to the device  5 , or a processing unit provided inside the device  5  may function as the communication processing unit  11 . 
     The plurality of communication lines  12  are provided corresponding to the degree of redundancy in the communication system  1 . That is, for the plurality of communication lines  12 , three communication lines  12  are provided which correspond to maximum redundancy in the communication system  1  and, in this embodiment, a maximum of triple redundancy. Each communication line  12  connects the plurality of communication processing units  11 . Specifically, all the communication lines  12   a ,  12   b , and  12   c  among the three communication lines  12   a ,  12   b , and  12   c  are connected to the communication processing unit  11   a  and the communication processing unit  11   b . On the other hand, any two communication lines  12  among the three communication lines  12   a ,  12   b , and  12   c  are connected to the communication processing unit  11   c  and the communication processing unit  11   d . That is, the communication line  12   b  is connected to the four communication processing units  11   a ,  11   b ,  11   c , and  11   d . Further, the communication line  12   a  is connected to three communication processing units  11   a ,  11   b , and  11   d  among the four communication processing units  11   a ,  11   b ,  11   c , and  11   d . Further, the communication line  12   c  is connected to the three communication processing units  11   a ,  11   b , and  11   c  among the four communication processing units  11   a ,  11   b ,  11   c , and  11   d . In the plurality of communication lines  12 , priority such as a main and sub are not specifically set, but may be appropriately set. 
     Thus, in the above-described communication system  1 , the communication processing unit  11  is able to receive a plurality of pieces of the communication data D transmitted from the other communication processing unit  11  via the plurality of connected communication lines  12 . The communication processing unit  11  is able to transmit a plurality of pieces of the communication data D to the other communication processing unit  11  via the plurality of connected communication lines  12 . Thus, the communication system  1  performs bidirectional communication between the respective communication processing units  11 . 
     Next, the communication data D used in the communication system  1  will be described with reference to  FIG. 2 .  FIG. 2  is an illustrative diagram of a frame format of the communication data. The communication data D has a frame format including at least device status data D 1  and a data link layer (second layer) to be described below. The communication data D may also include a network layer (third layer), and a transport layer (fourth layer). This communication data D includes a data field F 1 , a field F 2  on the header side of the data field F 1 , and a field F 3  on the footer side of the data field F 1 . 
     The device status data D 1  is stored in the data field F 1 . The device status data D 1  is data regarding a status of the device  5  connected to the communication processing unit  11 , which is transmitted from the device  5 , and is data that is shared among the plurality of communication processing units  11 . 
     A standard identifier D 2  for identifying a communication standard, a data type identifier D 3  for identifying a type of the communication data D, and a transmission source device identifier D 4  for identifying the device  5  that is a transmission source are stored as identification information in the field F 2 . Further, a sequence number D 5  that is information regarding order of the communication data D, a previously designated survival period D 6 , and the like are stored in the field F 2 . Further, while in the present embodiment, the survival period D 6  is included in the communication data D, the survival period D 6  may be stored in configuration data for reception T, which will be described below. 
     An error detection code D 7  for checking whether the communication data D is missing is stored in the field F 3 . The error detection code D 7  includes, for example, FCS. 
     Further, information regarding the network layer (third layer) and the transport layer (fourth layer) may be included in the field F 2  and the field F 3 . Further, the information stored in the field F 2  and the field F 3  is not limited to the above-described information. For example, a communication line identifier D 8  (indicated by a dotted line) for identifying the communication line  12  may be included as the identification information. Further, a flag as a variable, status of the communication data D, or the like may be included as the identification information. 
     Here, as described above, the communication processing unit  11  transmits a plurality of pieces of the communication data D to the other communication processing unit  11  via a plurality of communication lines  12  to be connected to the communication processing unit  11 . Further, the other communication processing unit  11  receives the plurality of pieces of the communication data D transmitted from the communication processing unit  11  via the plurality of communication lines  12  to be connected to the other communication processing unit  11 . That is, the communication system  1  has a publishing and subscribing communication standard in which the communication processing unit  11  is a publishing side, and the other communication processing unit  11  is a subscribing side. 
     The standard identifier D 2  is represented by “Protocol Identification”, and an identifier for identifying the communication standard is set. Specifically, an identifier regarding the publishing and subscribe communication standard is set. The data type identifier D 3  is represented by “Frame Type”, and an identifier corresponding to the type of the device  5  is set. For example, if the device  5  is a speedometer, the type of the communication data D is speed data, and thus, an identifier for identifying the speed data is set in the data type identifier D 3 . The transmission source device identifier D 4  is represented by “Source ID”, and is an ID specific to the device  5 . The sequence number D 5  is represented by the “Sequence Num”, and is counted up after each transmission of the communication data D. The survival period D 6  is referred to as “Limit of Period”, and when a previously designated survival period D 6  elapses, the communication data D is discarded. The error detection code D 7  is represented by “FCS”, and is a code for detecting an error such as destruction and missing of data. 
     Next, a communication process of the communication processing unit  11  in the communication system  1  will be described. In the communication system  1  of a publishing and subscribing type, the communication data D is transmitted and received in an asynchronous manner. Also, each communication processing unit  11  appropriately functions as a transmitting side (publishing side) and a receiving side (subscription side). When the communication processing unit  11  functions as the transmitting side that transmits a plurality of pieces of the communication data D to the plurality of communication lines  12 , the communication processing unit  11  generates a plurality of pieces of the communication data D illustrated in  FIG. 2  according to a plurality of communication lines  12  to be connected to the communication processing unit  11 . Also, the communication processing unit  11  transmits the plurality of pieces of generated communication data D to the plurality of communication lines  12 . 
     Meanwhile, when the communication processing unit  11  functions as the receiving side that receives the plurality of pieces of the communication data D from the plurality of communication lines  12 , the communication processing unit  11  determines whether the plurality of pieces of received communication data D is to be acquired, and acquires predetermined communication data D. Also, the communication processing unit  11  stores the acquired predetermined communication data D while updating the predetermined communication data D at a predetermined update period. Further, the stored communication data D is sent in response to a request from each device  5 . 
     Here, a communication process (transmission process) when the communication processing unit  11  functions as a transmitting side will first be described. Predetermined data including device status data D 1  is transmitted from the connected device  5  to the communication processing unit  11 . When the communication processing unit  11  acquires the predetermined data including the device status data D 1  from the connected device  5 , the communication processing unit  11  stores, in the data field F 1 , the device status data D 1  included in the data, and adds the above-described predetermined information to the field F 2  and the field F 3  to generate the communication data D illustrated in  FIG. 2 . In this case, the communication processing unit  11  generates a plurality of pieces of the communication data D according to the plurality of connected communication lines  12 . Also, the communication processing unit  11  transmits the plurality of pieces of generated communication data D to the plurality of communication lines  12 . The communication processing unit  11  repeatedly performs such a transmission process at a predetermined period. 
     Next, a communication process (reception process) when the communication processing unit  11  functions as a receiving side will be described. The plurality of pieces of the communication data D generated by the other communication processing unit  11  are transmitted to the communication processing unit  11  via the plurality of connected communication lines  12 . The communication processing unit  11  selects communication data D from among the plurality of pieces of transmitted communication data D based on the configuration data for reception T illustrated in  FIG. 3  to acquire the predetermined communication data D. 
       FIG. 3  is an illustrative diagram of the configuration data for reception. As illustrated in  FIG. 3 , the configuration data for reception T is stored (saved) in the plurality of respective communication processing units  11 . The configuration data for reception T includes a table in which the data type identifier (Frame Type) D 3 , the transmission source device identifier (Source ID) D 4 , and the number of reception paths (Path Redundant Level) are associated. Here, the number of reception paths is the number of receptions of the communication data D to be received at an update period for the communication data D, and indicates an aspect of the reception status. The configuration data for reception T illustrated in  FIG. 3  is set, for example, so that the data type identifier D 3  “10”, the transmission source device identifier D 4  “10”, and the number of reception paths “3” are associated. Further, the configuration data for reception T is set, for example, so that the data type identifier D 3  “10”, the transmission source device identifier D 4  “11”, and the number of reception paths “1” are associated. Further, the configuration data for reception T is set, for example, so that the data type identifier D 3  “11”, the transmission source device identifier D 4  “20”, and the number of reception paths “2” are associated. Further, the configuration data for reception T is set, for example, so that the data type identifier D 3  “11”, the transmission source device identifier D 4  “21”, and the number of reception paths “1” are associated. 
     Here, a control operation regarding the reception process of the communication processing unit  11  will be described with reference to  FIGS. 4 and 5 .  FIG. 4  is a flowchart of an example regarding an aircraft communication method according to the present embodiment.  FIG. 5  is a flowchart of an example regarding an aircraft communication method according to the present embodiment. 
     First, the communication processing unit  11  receives the communication data D (step S 1 : reception step). After the step S 1 , the communication processing unit  11  determines whether the communication data D has been destroyed based on the error detection code D 7  included in the received communication data D (step S 2 ). When the communication processing unit  11  determines that the communication data D has not been destroyed, the communication processing unit  11  determines no abnormality (step S 3 : Yes), and the process proceeds to step S 4 . On the other hand, when the communication processing unit  11  determines that the communication data D has been destroyed, the communication processing unit  11  determines abnormality (step S 3 : No), and the process proceeds to step S 11  to be described below. 
     When the communication processing unit  11  determines that there is no abnormality in step S 3 , the communication processing unit  11  determines whether information regarding the network layer (third layer) and the transport layer (fourth layer) is included in a frame format of the communication data D (step S 4 ). The communication processing unit  11  determines that the information regarding the third layer and the fourth layer are not included in the communication data D (step S 4 : Yes), and proceeds to step S 6 . On the other hand, the communication processing unit  11  determines that the information regarding the third layer and the fourth layer is included in the communication data D (step S 4 : No), the communication processing unit  11  executes the process regarding the third layer and the fourth layer (step S 5 ), and then proceeds to step S 6 . 
     Subsequently, the communication processing unit  11  determines whether or not the communication data D has the present standard based on the standard identifier D 2  included in the communication data D (step S 6 ). When the communication processing unit  11  determines that the communication data D has the standard (step S 6 : Yes), the communication processing unit  11  determines whether the communication data is the type of the communication data D set in the configuration data for reception T based on the data type identifier D 3  included in the communication data D (step S 8 ). On the other hand, when the communication processing unit  11  determines that the communication data D does not have the present standard (step S 6 : No), the communication processing unit  11  performs a process for another communication standard (step S 7 ), and then proceeds to step S 11 . 
     When the communication processing unit  11  determines that the communication data D is a predetermined type in step S 8  (step S 8 : Yes), the communication processing unit  11  executes a process of updating a management table for managing the communication data D (step S 9 ). Further, the process of updating a management table in step S 9  will be described below. On the other hand, when the communication processing unit  11  determines that the communication data D is not a predetermined type in step S 8  (step S 8 : No), the communication processing unit  11  proceeds to step S 11 . 
     In step S 9 , when the update process is executed, the communication processing unit  11  acquires and stores predetermined communication data D (step S 10 : data acquisition step), and ends the reception process. Meanwhile, when the communication processing unit  11  proceeds to step S 11 , the communication processing unit  11  ends the reception process without storing the received communication data D. Also, the communication processing unit  11  repeatedly performs such a reception process at an update period of the communication data D. Further, if the survival period D 6  elapses, the non-stored communication data D is discarded. 
     Thus, the reception process includes receiving the communication data D in step S 1  (reception step), determining whether the communication data D is to be acquired in steps S 2  to S 9  (acquisition determination step), and acquiring predetermined communication data D determined to be acquired in step S 10  (data acquisition step). 
     Next, the process of updating the management table for the communication data D in step S 9  will be described with reference to  FIG. 5 . Here, the management table used for the update process is stored in the communication processing unit  11 . In this management table, the number of reception paths of the communication data D, the sequence number D 5 , and the survival period D 6  are managed (registered and stored). When the communication processing unit  11  determines that the communication data D is a predetermined type in step S 8  (step S 8 : Yes), the communication processing unit  11  determines whether the sequence number (here, N) of the received communication data D is the same as the sequence number obtained by adding an order (here, 1) to the sequence number (here, n) registered in the management table, that is, N=n+1 (step S 21 ). 
     When the communication processing unit  11  determines that N=n+1 in step S 21  (step S 21 : Yes), the communication processing unit  11  determines whether the number of reception paths registered in the management table (actual number of reception paths) is equal to or greater than the number of reception paths (set number of reception paths) set in the configuration data for reception (step S 22 ). When the communication processing unit  11  determines that the number of reception paths registered in the management table is equal to or greater than the set number of reception paths (step S 22 : Yes), the communication processing unit  11  updates the management table (step S 23 ). That is, the communication processing unit  11  updates the registered sequence number n in the management table with the sequence number N of the received communication data D, resets the registered number of reception paths, and resets the registered survival period D 6 . On the other hand, when the communication processing unit  11  determines that the number of reception paths that is registered in the management table is smaller than the set number of reception paths (step S 22 : No), the communication processing unit  11  determines that communication data D is missing, records a missing error (step S 24 ), and proceeds to step S 23 . Further, during the execution of step S 24 , the communication processing unit  11  detects that there is abnormality in any one communication line  12  among the plurality of communication lines  12 . Also, if the communication processing unit  11  ends the process of updating the management table in step S 23 , the communication processing unit  11  proceeds to step S 10 . Thus, the communication processing unit  11  determines whether the received communication data D is newer than previously received communication data D based on the sequence number included in the received communication data D, and acquires the communication data D is determined to be new. 
     On the other hand, when the communication processing unit  11  determines that N=n+1 is not satisfied in step S 21  (step S 21 : No), the communication processing unit  11  determines whether N≦n−1 (step S 25 ). When the communication processing unit  11  determines that the N n−1 (step S 25 : Yes), the communication processing unit  11  determines that the communication data D is delayed, records a delay error (step S 26 ), and proceeds to step S 11 . 
     When the communication processing unit  11  determines that N≦n−1 is not satisfied in step S 25  (step S 25 : No), the communication processing unit  11  determines whether N=n (step S 27 ). When the communication processing unit  11  determines that N=n (step S 27 : Yes), the communication processing unit  11  determines that the communication data D having the same sequence number has been received, and counts up the number of reception paths in the management table to update the number of reception paths (step S 28 ). After step S 28 , the communication processing unit  11  proceeds to step S 11 . Thus, when the communication processing unit  11  has received a plurality of pieces of communication data D having the same sequence number, the communication processing unit  11  stores the first received communication data D, and uses the communication data D received later for the update of the number of reception paths. Therefore, when the communication processing unit has received a plurality of pieces of communication data D having the same sequence number, the communication processing unit  11  acquires the first received communication data D as the communication data D. 
     When the communication processing unit  11  determines that N=n is not satisfied in step S 27  (step S 27 : No), the communication processing unit  11  determines whether N&gt;n+1 (step S 29 ). When the communication processing unit determines that N&gt;n+1 (step S 29 : Yes), the communication processing unit  11  determines that the communication data D is missing, records a missing error (step S 30 ), and proceeds to step S 23 . That is, the communication processing unit  11  stores the communication data D having the latest sequence number in the management table even when the sequence number is missing. Further, when the communication processing unit  11  determines that N&gt;n+1 is not satisfied (step S 29 : No), the communication processing unit  11  proceeds to step S 11 . 
     Next, a control operation regarding an abnormality detection process of the communication processing unit  11  will be described with reference to  FIG. 6 .  FIG. 6  is a flowchart of an example regarding an aircraft communication method according to the present embodiment. The abnormality detection process is a process of determining whether the plurality of communication lines  12  are abnormal. Further, it is preferable that, when the communication processing unit  11  specifies the abnormal communication line  12  from among the plurality of communication lines  12 , the communication processing unit  11  attaches the communication line identifier D 8  that is an identifier corresponding to the communication line  12  to the communication data D. 
     The communication processing unit  11  determines whether there is communication data D determined to be erroneous in the reception process (step S 41 ). The error determination includes, for example, the missing error and the delay error described above. When the communication processing unit  11  determines that there is communication data D determined to be erroneous (step S 41 : Yes), the communication processing unit  11  specifies the communication line  12  based on the communication line identifier D 8  attached to the communication data D (step S 42 ). When the communication processing unit  11  specifies the communication line  12  in step S 42 , the communication processing unit  11  detects that a predetermined communication line  12  is abnormal (step S 43 ), and then ends the abnormality detection process. On the other hand, when the communication processing unit  11  determines that there is no communication data D determined to be erroneous (step S 41 : No), the communication processing unit  11  ends the abnormality detection process. Also, the communication processing unit  11  repeatedly executes the abnormality detection process at a predetermined period. 
     Next, a control operation regarding the abnormality detection process for the device  5  connected to the communication processing unit  11  will be described. The device  5  requests the communication processing unit  11  to transmit the communication data D at a predetermined period in order to acquire, from the communication processing unit  11 , the communication data D updated at a predetermined period in the communication processing unit  11 . Here, when the device  5  cannot acquire the communication data D within the survival period D 6  included in the communication data D, the device  5  detects that there is abnormality. That is, since the communication data D is discarded when the previously designated survival period D 6  elapses, the device  5  cannot acquire the discarded communication data D, and in this case, the device  5  determines that there is abnormality in the communication processing unit  11  or the plurality of communication lines  12 , and detects the abnormality. 
     Next, an example in which the communication system  1  described above has been applied to an aircraft  100  will be described with reference to  FIGS. 7 and 8 .  FIG. 7  is a configuration diagram regarding an example of an aircraft to which the communication system according to the present embodiment has been applied. The aircraft  100  includes control surfaces such as multifunction spoilers MFSs on wing, ground spoilers GSs on wing, ailerons  111 , elevators  112 , and a rudder  113 . Further, a plurality of devices  5  are mounted on the aircraft  100 . A plurality of actuators  102  for driving the various control surfaces described above, a primary flight control device (PFCC: Primary Flight Control Computer)  101  for controlling the plurality of actuators  102 , and an interface module IM, for example, are provided as the plurality of devices  5 . 
     In such an aircraft  100 , the communication system  1  includes a plurality of communication processing units  11  connected to a plurality of actuators  102 , respectively, and three backbone bus lanes  12   a ,  12   b , and  12   c  serving as communication lines connecting between the communication processing units  11 . 
     Three primary flight control devices  101  are provided. Three primary flight control devices  101   a ,  101   b , and  101   c  are respectively connected to the three backbone bus lanes  12   a ,  12   b , and  12   c . Further, a processing unit functioning as the communication processing unit  11  is provided in the three primary flight control devices  101   a ,  101   b , and  101   c.    
     Further, a plurality of communication processing units  11  are connected to the three backbone bus lanes  12   a ,  12   b , and  12   c , respectively. In this case, the different backbone bus lanes  12   a ,  12   b , and  12   c  are connected to the adjacent communication processing units  11 , and the respective adjacent communication processing units  11  are connected by a bus lane  105 . Therefore, the communication processing unit  11  transmits and receives the communication data D via the backbone bus lanes  12   a ,  12   b , and  12   c  and the bus lane  105  connected to the other adjacent communication processing unit  11 , resulting in a dual redundant configuration. Thus, the communication system including the backbone bus lane  12  and the bus lane  105  is configured described above, and thus, it is possible to reduce wirings of communication lines. 
     Next, the communication processing unit  11  will be described with reference to  FIG. 8 .  FIG. 8  is a schematic diagram of a communication device of the communication system according to the present embodiment. The communication processing unit  11  provided in the aircraft  100  is provided in a communication device  200  which is separate from the device  5 . The communication device  200  includes the communication processing unit  11  provided therein, a plurality of transmission and reception ports (transmission and reception units)  201 , and a device connection port  202 . The plurality of transmission and reception ports  201  are connected to the backbone bus lanes  12   a ,  12   b , and  12   c , and the bus lane  105 . The device connection port  202  is connected to the device  5 , such as the actuator  102 . Therefore, the communication system  1  has a configuration in which the device  5  can be physically disconnected from the communication device  200 . 
     As described above, according to the configuration of this embodiment, the communication processing unit  11  can require necessary communication data D among the plurality of pieces of the received communication data D based on the various identifiers D 2 , D 3 , D 4 , and D 8  included in the communication data D. In this case, redundancy is realized between the communication processing units  11  by the plurality of communication lines  12 , and highly reliable communication data D is acquired from among the plurality of pieces of the communication data D, and thus, it is possible to secure the reliability of the communication data D. Further, since the communication line  12  is appropriately provided according to the degree of redundancy set in the device  5 , and the communication line  12  and the communication processing unit  11  may be appropriately connected, it is possible to easily cope with the set degree of redundancy without affecting the device  5 . 
     Further, according to the configuration of this embodiment, the communication processing unit  11  can acquire new communication data D. Therefore, the communication processing unit  11  becomes able to transmit the new acquired communication data D to the device  5 , and thus, the device  5  can execute control without delay based on the communication data D. 
     Further, according to the configuration of this embodiment, the communication processing unit  11  can acquire the first received communication data D among the plurality of pieces of the communication data D determined to be new. Therefore, since the communication processing unit  11  can transmit the first received communication data D to the device  5 , the device  5  can execute the control more rapidly based on the communication data D. Further, in the present embodiment, when the communication processing unit  11  receives a plurality of pieces of communication data D having the same sequence number, the communication processing unit  11  acquires the first received communication data D as the communication data D, but the present invention is not limited thereto. For example, when the communication processing unit  11  receives the plurality of pieces of communication data D having the same sequence number, the communication processing unit  11  may acquire matching communication data D as the communication data D among the plurality of pieces of the communication data D. 
     Further, according to the configuration of this embodiment, the communication processing unit  11  can detect the abnormality of the communication line  12  based on the communication data D. Therefore, it is possible to rapidly take appropriate measures to solve the abnormality of the communication line  12 . Further, in the present embodiment, the abnormality of the communication line  12  is detected based on the communication line identifier D 8  included in the communication data D, but the present invention is not limited to this configuration. For example, the communication line identifier D 8  may be stored in the configuration data for reception T, and the communication processing unit  11  may detect the abnormality of the communication line  12  based on the communication line identifier D 8  stored in the configuration data for reception T. 
     Further, according to the configuration of this embodiment, when the set number of reception paths is different from the actual number of reception paths, the communication processing unit  11  can detect that the communication line is abnormal. That is, if the actual number of reception paths is smaller than the set number of reception paths, the communication processing unit  11  can detect that there is abnormality in any one of the plurality of communication lines  12 . Therefore, it is possible to rapidly take appropriate measures to solve the abnormality of the communication system. Further, it is possible to simplify the abnormality detection process as compared with the case in which the communication line identifier D 8  is attached, and to suppress an increase in a control load regarding the abnormality detection process. 
     Further, according to the configuration of this embodiment, the communication processing unit  11  can acquire the non-destroyed communication data D. Therefore, the communication processing unit  11  transmits the acquired non-destroyed communication data D to the device  5 , making it possible for the device  5  to accurately execute the control based on the communication data D. 
     Further, according to the configuration of this embodiment, the communication processing unit  11  can transmit the plurality of pieces of the communication data D to the plurality of communication lines  12 . Therefore, the communication processing unit  11  can transmit the device status data D 1  of the corresponding device  5  to the other communication processing unit  11 . 
     Further, according to the configuration of this embodiment, when the device  5  does not acquire new communication data D in the survival period D 6 , the device  5  can detect abnormality. Therefore, it is possible to rapidly take appropriate measures to solve the abnormality of the communication system. Further, while, in the present embodiment, when the device  5  is unable to acquire the communication data D in the previously designated survival period D 6 , the device  5  has detected the abnormality, the present invention is not limited to this configuration, and the communication processing unit  11  may detect the abnormality. That is, when there is no reception of the communication data D in the survival period D 6  included in the communication data D, the communication processing unit  11  may detect that there is the abnormality. 
     Further, according to the configuration of this embodiment, since the device  5  and the communication processing unit  11  can be separate, it is possible to clearly isolate the configuration of the device  5  and the configuration of the communication system  1 . Further, since the communication device can be configured as a dedicated communication device  200  of the communication processing unit  11 , it is possible to improve processing speed of the communication. 
     Further, the processing unit provided in the device  5  may function as the communication processing unit  11 . That is, software (so-called middleware) capable of causing the processing unit to function as the communication processing unit  11  is caused to be executed by the processing unit of the device  5 , and thus, the processing unit may be realized as the communication processing unit  11 . 
     Further, according to the configuration of this embodiment, the communication processing unit  11  can receive a plurality of pieces of the communication data D in the reception process, the communication processing unit  11  can determine whether the communication data D is to be acquired in the acquisition determination process, and the communication processing unit  11  can acquire the necessary communication data D in the data acquisition process. 
     While the present invention has been applied as the communication system  1  of the aircraft in the present embodiment, the present invention may be applied to objects other than the aircraft as long as the communication system is multiple redundant, and the present invention is not particularly limited. Further, the plurality of communication lines  12  in this embodiment may be wired or may be wireless, and the present invention is not particularly limited. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  communication system 
               5  device 
               11  communication processing unit 
               12  communication line 
               100  aircraft 
               101  primary flight control device 
               102  actuator 
               105  bus lane 
               111  aileron 
               112  elevator 
               113  rudder 
               200  communication device 
               201  transmission and reception port 
               202  device connection port 
             D communication data 
             D 1  device status data 
             D 2  standard identifier 
             D 3  data type identifier 
             D 4  transmission source device identifier 
             D 5  sequence number 
             D 6  survival period 
             D 7  error detection code 
             D 8  communication line identifier 
             F 1  data field 
             F 2  field 
             F 3  field 
             MFS multifunction spoiler 
             GS ground spoiler 
             IM interface module