Patent Publication Number: US-2021163025-A1

Title: Vehicle-mounted communication system, data acquisition device, management device, and monitoring method

Description:
TECHNICAL FIELD 
     The present invention relates to vehicle-mounted communication systems, data acquisition devices, management devices, and monitoring methods. 
     This application is based on and claims priority from Japanese Patent Application No. 2018-160940 filed Aug. 30, 2018, the disclosure of which is incorporated herein. 
     BACKGROUND ART 
     Japanese Unexamined Patent Application Publication No. 2013-131907 (Patent Literature 1) discloses the following vehicle network monitoring device. Specifically, the vehicle network monitoring device is disposed in a vehicle network where data communication is performed between a plurality of vehicle-mounted control devices and monitors the communication data. The vehicle network monitoring device includes a monitoring unit that detects illegal data through monitoring with a data communication format defined for putting into practice a communication protocol used in the vehicle network. 
     Japanese Unexamined Patent Application Publication No. 2017-112590 (Patent Literature 2) discloses the following communication device. Specifically, the communication device includes a communication unit that exchanges messages in a network and a first illegality detector that detects an illegal message by detecting values of a plurality of monitoring items from a message received in the communication unit and determining whether or not each of the detection values of the plurality of monitoring items is within a corresponding reference range. For each of the plurality of monitoring items, a first reference range and a second reference range smaller than the first reference range are set. The first illegality detector determines that the message is an illegal message when any of the detection values is outside the first reference range, and determines that the message is an illegal message if a predetermined rule is satisfied when any of the detection values is within the first reference range but outside the second reference range. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Unexamined Patent Application Publication No. 2013-131907 
     PTL 2: Japanese Unexamined Patent Application Publication No. 2017-112590 
     SUMMARY OF INVENTION 
     (1) A vehicle-mounted communication system according to the present disclosure is mounted in a vehicle. The vehicle-mounted communication system includes a plurality of functional units connected to a control network in the vehicle, and also includes a management device connected to a security network in the vehicle. Communication from the control network to the security network is partially limited. The vehicle-mounted communication system further includes a data acquisition device that acquires data transmitted through the control network and transmits the data to the management device. The management device detects an abnormality related to the control network based on the data received from the data acquisition device. 
     (8) A vehicle-mounted communication system according to the present disclosure is mounted in a vehicle. The vehicle-mounted communication system includes a plurality of functional units connected to a control network in the vehicle, and also includes a data acquisition device that is communicable with a management device connected to a security network in the vehicle and that acquires data transmitted through the control network. Communication from the control network to the security network is partially limited. The data acquisition device is a connector that connects between paths in the control network and detects an abnormality related to the control network based on the acquired data. 
     (9) A data acquisition device according to the present disclosure is a data acquisition device in a vehicle-mounted communication system mounted in a vehicle, the vehicle-mounted communication system having a plurality of functional units connected to a control network and a management device connected to a security network. Communication from the control network to the security network is partially limited. The data acquisition device includes an acquisition unit that acquires data transmitted through the control network, and also includes a transmitter that transmits the data acquired by the acquisition unit to the management device. 
     (12) A management device according to the present disclosure is a management device in a vehicle-mounted communication system mounted in a vehicle, the management device being connected to a security network. In the vehicle, a plurality of functional units are connected to a control network and communication from the control network to the security network is partially limited. The management device includes a communication unit that acquires data transmitted through the control network, and also includes a processor that detects an abnormality related to the control network based on the data acquired by the communication unit. 
     (13) A monitoring method according to the present disclosure is a monitoring method in a vehicle-mounted communication system mounted in a vehicle, the vehicle-mounted communication system including a plurality of functional units connected to a control network in the vehicle and a management device connected to a security network in the vehicle. Communication from the control network to the security network is partially limited. The monitoring method includes a step for acquiring data transmitted through the control network, a step for transmitting the acquired data to the management device, and a step performed by the management device for detecting an abnormality related to the control network based on the received data. 
     (14) A monitoring method according to the present disclosure is a monitoring method in a vehicle-mounted communication system mounted in a vehicle, the vehicle-mounted communication system including a plurality of functional units connected to a control network in the vehicle and a data acquisition device communicable with a management device connected to a security network in the vehicle. Communication from the control network to the security network is partially limited. The data acquisition device is a connector that connects between paths in the control network. The monitoring method includes a step performed by the data acquisition device for acquiring data transmitted through the control network, and a step performed by the data acquisition device for detecting an abnormality related to the control network based on the acquired data. 
     An aspect of the present disclosure may be realized not only as a vehicle-mounted communication system equipped with such a characteristic processor, but also as a program for causing a computer to execute such characteristic processing steps. Furthermore, an aspect of the present disclosure may be realized as a semiconductor integrated circuit that partially or entirely realizes the vehicle-mounted communication system. 
     An aspect of the present disclosure may be realized not only as a data acquisition device equipped with such a characteristic processor, but also as a method including such characteristic processing steps or a program for causing a computer to execute such steps. Moreover, an aspect of the present disclosure may be realized as a semiconductor integrated circuit that partially or entirely realizes the data acquisition device. 
     An aspect of the present disclosure may be realized not only as a management device equipped with such a characteristic processor, but also as a method including such characteristic processing steps or a program for causing a computer to execute such steps. Moreover, an aspect of the present disclosure may be realized as a semiconductor integrated circuit that partially or entirely realizes the management device. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates an example of the configuration of a vehicle-mounted communication system according to a first embodiment of the present invention. 
         FIG. 2  illustrates an example of a partial configuration of the vehicle-mounted communication system according to the first embodiment of the present invention. 
         FIG. 3  illustrates an example of the configuration of each data acquisition device according to the first embodiment of the present invention. 
         FIG. 4  illustrates an example of the configuration of a management device in the vehicle-mounted communication system according to the first embodiment of the present invention. 
         FIG. 5  illustrates an example of sensor information in the vehicle-mounted communication system according to the first embodiment of the present invention. 
         FIG. 6  illustrates an example of control information in the vehicle-mounted communication system according to the first embodiment of the present invention. 
         FIG. 7  illustrates an example of the relationship between an angular velocity in sensor information and a motor speed in control information in the vehicle-mounted communication system according to the first embodiment of the present invention. 
         FIG. 8  illustrates an example of the relationship between a drive amount based on a value of an angular velocity field in sensor information and a drive amount in control information in the vehicle-mounted communication system according to the first embodiment of the present invention. 
         FIG. 9  illustrates another example of a partial configuration of the vehicle-mounted communication system according to the first embodiment of the present invention. 
         FIG. 10  illustrates another example of the configuration of each data acquisition device according to the first embodiment of the present invention. 
         FIG. 11  illustrates an example of a sequence of abnormality detection and abnormality-related processing in a power line communication system according to the first embodiment of the present invention. 
         FIG. 12  illustrates a partial configuration in modification 1 of the vehicle-mounted communication system according to the first embodiment of the present invention. 
         FIG. 13  illustrates an example of the configuration of each data acquisition device in modification 1 of the vehicle-mounted communication system according to the first embodiment of the present invention. 
         FIG. 14  illustrates an example of a sequence of abnormality detection and abnormality-related processing in modification 1 of the power line communication system according to the first embodiment of the present invention. 
         FIG. 15  illustrates the configuration of modification 2 of the vehicle-mounted communication system according to the first embodiment of the present invention. 
         FIG. 16  illustrates an example of the configuration of a vehicle-mounted communication system according to a second embodiment of the present invention. 
         FIG. 17  illustrates an example of a partial configuration of the vehicle-mounted communication system according to the second embodiment of the present invention. 
         FIG. 18  illustrates an example of the configuration of each data acquisition device according to the second embodiment of the present invention. 
         FIG. 19  illustrates an example of a sequence of abnormality detection and abnormality-related processing in a power line communication system according to the second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the related art, a vehicle-mounted network system that detects illegal communication in a vehicle-mounted network has been developed. 
     Problems to be Solved by Present Disclosure 
     There is a demand for a technology that can establish a vehicle-mounted network with improved security over the technologies described in Patent Literature 1 and Patent Literature 2. 
     The present disclosure has been made for solving the aforementioned problems, and an object thereof is to provide a vehicle-mounted communication system, a data acquisition device, a management device, and a monitoring method that can establish a vehicle-mounted network with improved security. 
     Advantages of Present Disclosure 
     According to the present disclosure, a vehicle-mounted network with improved security can be established. 
     Description of Embodiments of Present Invention 
     First, the following description relates to a list of contents for embodiments of the present invention. 
     (1) A vehicle-mounted communication system according to an embodiment of the present invention is mounted in a vehicle and includes a plurality of functional units connected to a control network in the vehicle and a management device connected to a security network in the vehicle. Communication from the control network to the security network is partially limited. The vehicle-mounted communication system further includes a data acquisition device that acquires data transmitted through the control network and transmits the data to the management device. The management device detects an abnormality related to the control network based on the data received from the data acquisition device. 
     Accordingly, the communication is limited by isolating the control network for transmitting information between the functional units and the security network for monitoring from each other, thereby detecting an abnormality in the vehicle while achieving improved security by using the security network in which the effect of the abnormality in the control network is minimized. Consequently, a vehicle-mounted network with improved security can be established. 
     (2) Preferably, the data acquisition device performs control related to the control network when an abnormality is detected by the management device. 
     According to this configuration, for example, transmission of illegal data through the control network can be prevented, thereby reducing the effect of the abnormality. 
     (3) Preferably, the data acquisition device performs control for cutting off each functional unit from the control network when the abnormality is detected by the management device. 
     According to this configuration, transmission paths for illegal data can be blocked. For example, transmission of illegal data from the functional unit detected as being abnormal through the control network can be prevented, and reception of illegal data by a normal functional unit can be prevented. 
     (4) Preferably, the data acquisition device performs control for switching paths in the control network when the abnormality is detected by the management device. 
     According to this configuration, for example, another transmission path is used in place of the transmission path corresponding to the detected abnormality, so that the vehicle-mounted communication system can continue to perform normal operation. 
     (5) Preferably, the management device controls each functional unit when the abnormality is detected. 
     According to this configuration, for example, the operation of the functional unit detected as being abnormal can be stopped, or the operation of a normal functional unit can be stopped to prevent the functional unit from receiving illegal data, so that the effect of the abnormality can be reduced. 
     (6) Preferably, the management device changes operation of each functional unit toward a safer side for running of the vehicle when the abnormality is detected. 
     According to this configuration, a malfunction of a functional unit caused as a result of receiving illegal data can be suppressed, thereby ensuring stable running of the vehicle. 
     (7) Preferably, the management device performs control for providing a notification about the abnormality when the abnormality is detected. 
     According to this configuration, for example, the driver of the vehicle can recognize that inoperability is caused by an abnormality in the control network, so as to be able to ascertain the situation in detail. 
     (8) A vehicle-mounted communication system according to an embodiment of the present invention is mounted in a vehicle, and also includes a plurality of functional units connected to a control network in the vehicle and a data acquisition device that is communicable with a management device connected to a security network in the vehicle and that acquires data transmitted through the control network. Communication from the control network to the security network is partially limited. The data acquisition device is a connector that connects between paths in the control network and detects an abnormality related to the control network based on the acquired data. 
     Accordingly, the communication is limited by isolating the control network for transmitting information between the functional units and the security network for monitoring from each other, thereby detecting an abnormality in the vehicle while achieving improved security by using the security network in which the effect of the abnormality in the control network is minimized. Moreover, the data acquisition device can be readily retrofitted to, for example, a vehicle-mounted communication system equipped with existing functional units, and the functional units can be simplified. Consequently, a vehicle-mounted network with improved security can be established. 
     (9) A data acquisition device according to an embodiment of the present invention is a data acquisition device in a vehicle-mounted communication system mounted in a vehicle, the vehicle-mounted communication system having a plurality of functional units connected to a control network and a management device connected to a security network. Communication from the control network to the security network is partially limited. The data acquisition device includes an acquisition unit that acquires data transmitted through the control network, and also includes a transmitter that transmits the data acquired by the acquisition unit to the management device. 
     Accordingly, the communication is limited by isolating the control network for transmitting information between the functional units and the security network for monitoring from each other, thereby detecting an abnormality in the vehicle while achieving improved security by using the security network in which the effect of the abnormality in the control network is minimized. Consequently, a vehicle-mounted network with improved security can be established. 
     (10) Preferably, the data acquisition device is a connector that connects between paths in the control network. 
     According to this configuration, the data acquisition device can be readily retrofitted to, for example, a vehicle-mounted communication system equipped with existing functional units, and the functional units can be simplified. 
     (11) Preferably, the data acquisition device is included in each functional unit. 
     According to this configuration, the configuration of the vehicle-mounted communication system can be simplified. 
     (12) A management device according to an embodiment of the present invention is a management device in a vehicle-mounted communication system mounted in a vehicle, the management device being connected to a security network. In the vehicle, a plurality of functional units are connected to a control network and communication from the control network to the security network is partially limited. The management device includes a communication unit that acquires data transmitted through the control network, and also includes a processor that detects an abnormality related to the control network based on the data acquired by the communication unit. 
     Accordingly, the communication is limited by isolating the control network for transmitting information between the functional units and the security network for monitoring from each other, thereby detecting an abnormality in the vehicle while achieving improved security by using the security network in which the effect of the abnormality in the control network is minimized. Moreover, various types of abnormalities can be detected collectively in a single device. Consequently, a vehicle-mounted network with improved security can be established. 
     (13) A monitoring method according to an embodiment of the present invention is a monitoring method in a vehicle-mounted communication system mounted in a vehicle, the vehicle-mounted communication system including a plurality of functional units connected to a control network in the vehicle and a management device connected to a security network in the vehicle. Communication from the control network to the security network is partially limited. The monitoring method includes a step for acquiring data transmitted through the control network, a step for transmitting the acquired data to the management device, and a step performed by the management device for detecting an abnormality related to the control network based on the received data. 
     Accordingly, the communication is limited by isolating the control network for transmitting information between the functional units and the security network for monitoring from each other, thereby detecting an abnormality in the vehicle while achieving improved security by using the security network in which the effect of the abnormality in the control network is minimized. Consequently, a vehicle-mounted network with improved security can be established. 
     (14) A monitoring method according to an embodiment of the present invention is a monitoring method in a vehicle-mounted communication system mounted in a vehicle, the vehicle-mounted communication system including a plurality of functional units connected to a control network in the vehicle and a data acquisition device communicable with a management device connected to a security network in the vehicle. Communication from the control network to the security network is partially limited. The data acquisition device is a connector that connects between paths in the control network. The monitoring method includes a step performed by the data acquisition device for acquiring data transmitted through the control network, and a step performed by the data acquisition device for detecting an abnormality related to the control network based on the acquired data. 
     Accordingly, the communication is limited by isolating the control network for transmitting information between the functional units and the security network for monitoring from each other, thereby detecting an abnormality in the vehicle while achieving improved security by using the security network in which the effect of the abnormality in the control network is minimized. Moreover, the data acquisition device can be readily retrofitted to, for example, a vehicle-mounted communication system equipped with existing functional units, and the functional units can be simplified. Consequently, a vehicle-mounted network with improved security can be established. 
     Embodiments of the present invention will be described below with reference to the drawings. In the drawings, identical or equivalent sections will be given the same reference signs, and the descriptions thereof will not be repeated. Moreover, at least a part of the embodiments to be described below may be arbitrarily combined. 
     First Embodiment 
     [Configuration and Basic Operation] 
       FIG. 1  illustrates an example of the configuration of a vehicle-mounted communication system according to a first embodiment of the present invention. 
     Referring to  FIG. 1 , a vehicle-mounted communication system  301  includes a plurality of functional units  111 , a management device  121 , and a plurality of data acquisition devices  131 . The plurality of functional units  111  include, for example, a central gateway  101  and a TCU (telematics communication unit). 
     The vehicle-mounted communication system  301  is mounted in a vehicle  1 . The plurality of functional units  111  excluding the central gateway  101  are connected to the central gateway  101  by a control network  10 , such as a CAN (controller area network) (registered trademark) bus compliant with the CAN standard or an Ethernet (registered trademark) cable. 
     Furthermore, each of the functional units  111  is, for example, an automated driving ECU (electronic control unit), a driving support device, or a sensor, and is capable of communicating with another functional unit  111  via the central gateway  101 . 
     For example, the central gateway  101  relays information between functional units  111 , excluding the central gateway  101 , connected to different control networks  10 . 
     The central gateway  101  and the functional units  111  communicate with each other via the control network  10 . For example, control information for controlling the various types of functional units  111  is exchanged between the central gateway  101  and the functional units  111 . 
     Each of the data acquisition devices  131  is connected between functional units  111  excluding the central gateway  101  or between the central gateway  101  and another functional unit  111 . 
     The management device  121  is connected to the data acquisition devices  131  by a security network  20 . 
     Communication from the control network  10  to the security network  20  is partially limited. Specifically, data created by one functional unit  111  can be transmitted therefrom to another functional unit  111  via the control network  10  but cannot be transmitted to the management device  121  via the security network  20 . 
     Each data acquisition device  131  acquires data transmitted through the control network  10  and transmits the data to the management device  121 . 
       FIG. 2  illustrates an example of a partial configuration of the vehicle-mounted communication system according to the first embodiment of the present invention.  FIG. 2  illustrates a power steering function for assisting with the steering operation of the vehicle  1 . 
     Referring to  FIG. 2 , a steering angle sensor  111 A, a control unit  111 B, and the central gateway  101  as examples of the functional units  111  are connected to one another by the control network  10 . 
     Furthermore, the central gateway  101  and a drive unit  111 C as examples of the functional units  111  are connected to each other by the control network  10 . The drive unit  111 C has a motor  151  for assisting with the steering operation. 
     Moreover, a data acquisition device  131 A is connected between the steering angle sensor  111 A and the control unit  111 B. A data acquisition device  131 B is connected between the control unit  111 B and the central gateway  101 . A data acquisition device  131 C is connected between the central gateway  101  and the drive unit  111 C. 
     The steering angle sensor  111 A detects, for example, the angular velocity of the steering angle in the steering operation and the direction of the steering operation, and transmits sensor information indicating the detected angular velocity and the detected direction to the control unit  111 B via the data acquisition device  131 A. 
     For example, the control unit  111 B calculates a power-steering assistance amount based on the sensor information received from the steering angle sensor  111 A via the data acquisition device  131 A, and creates control information containing the direction, the motor speed, and the drive amount for controlling the rotation of the motor  151  based on the calculated assistance amount. 
     Then, the control unit  111 B transmits the created control information to the drive unit  111 C via the data acquisition device  131 B, the central gateway  101 , and the data acquisition device  131 C. 
     For example, the drive unit  111 C controls the rotation of the motor  151  included therein based on the control information received from the control unit  111 B via the data acquisition device  131 B, the central gateway  101 , and the data acquisition device  131 C. 
       FIG. 3  illustrates an example of the configuration of each data acquisition device according to the first embodiment of the present invention. 
     Referring to  FIG. 3 , the data acquisition device  131  is, for example, a connector that connects between paths in the control network  10 . 
     More specifically, the data acquisition device  131  includes an acquisition unit  31 , a transmitter  32 , a receiver  33 , and a switch  34 . The acquisition unit  31  includes a processor  35 . The acquisition unit  31 , the transmitter  32 , the receiver  33 , and the switch  34  are mounted on, for example, a substrate  141 . 
     The substrate  141  is connected to the functional units  111  or the central gateway  101  by wire harnesses  21  and  22  used as the control network  10 , and is connected to the management device  121  by a wire harness  23  used as the security network  20 . 
     Referring to  FIGS. 2 and 3 , the acquisition unit  31  in the data acquisition device  131 A acquires sensor information transmitted through the control network  10 . 
     In detail, the sensor information transmitted from the steering angle sensor  111 A is transmitted to the control unit  111 B via the wire harness  21 , the switch  34 , and the wire harness  22  in the data acquisition device  131 A. 
     The switch  34  in the data acquisition device  131 A is connected between the wire harness  21  and the wire harness  22 . 
     The switch  34  switches between a connected mode and a non-connected mode between the wire harness  21  and the wire harness  22  in accordance with control of the processor  35 . 
     In the normal state, the processor  35  turns on the switch  34  to connect the wire harness  21  and the wire harness  22  to each other. Accordingly, the sensor information from the wire harness  21  is transmitted to the wire harness  22 . 
     The acquisition unit  31  in the data acquisition device  131 A acquires, for example, the sensor information transmitted through the data acquisition device  131 A between the wire harness  21  and the switch  34 , and outputs the acquired sensor information to the transmitter  32 . 
     The acquisition unit  31  in the data acquisition device  131 B acquires the control information transmitted through the control network  10 . 
     In detail, the control information transmitted from the control unit  111 B is transmitted to the central gateway  101  via the wire harness  21 , the switch  34 , and the wire harness  22  in the data acquisition device  131 B. 
     The switch  34  in the data acquisition device  131 B is connected between the wire harness  21  and the wire harness  22 . 
     The switch  34  switches between a connected mode and a non-connected mode between the wire harness  21  and the wire harness  22  in accordance with control of the processor  35 . 
     In the normal state, the processor  35  turns on the switch  34  to connect the wire harness  21  and the wire harness  22  to each other. Accordingly, the control information from the wire harness  21  is transmitted to the wire harness  22 . 
     The acquisition unit  31  in the data acquisition device  131 B acquires, for example, the control information transmitted through the data acquisition device  131 B between the wire harness  21  and the switch  34 , and outputs the acquired control information to the transmitter  32 . 
     The transmitter  32  transmits the data acquired by the acquisition unit  31  to the management device  121 . 
     More specifically, the transmitter  32  in the data acquisition device  131 A transmits the sensor information received from the acquisition unit  31  to the management device  121  via the wire harness  23  used as the security network  20 . 
     The transmitter  32  in the data acquisition device  131 B transmits the control information received from the acquisition unit  31  to the management device  121  via the wire harness  23 . 
     Furthermore, the data acquisition device  131 C acquires control information transmitted to the drive unit  111 C via the central gateway  101  and transmits the acquired control information to the management device  121 . 
     The management device  121  detects an abnormality related to the control network  10  based on data received from the data acquisition devices  131 . 
     More specifically, the management device  121  receives the sensor information transmitted from the data acquisition device  131 A and the control information transmitted from the data acquisition device  131 B, and detects an abnormality in the steering angle sensor  111 A, the control unit  111 B, and the drive unit  111 C based on the received pieces of information. 
       FIG. 4  illustrates an example of the configuration of the management device in the vehicle-mounted communication system according to the first embodiment of the present invention. 
     Referring to  FIG. 4 , the management device  121  includes a communication unit  41 , a storage unit  42 , and a processor  43 . 
     [Abnormality Detection Example 1] 
     The communication unit  41  acquires data transmitted through the control network. 
     More specifically, the communication unit  41  receives sensor information transmitted from the data acquisition device  131 A and stores the received sensor information in the storage unit  42 . Moreover, the communication unit  41  receives control information transmitted from the data acquisition device  131 B and stores the received control information in the storage unit  42 . 
       FIG. 5  illustrates an example of sensor information in the vehicle-mounted communication system according to the first embodiment of the present invention. 
     Referring to  FIG. 5 , the sensor information is constituted of a direction field and an angular velocity field in that order from the head. 
     The direction field has stored therein a value indicating the direction of a steering angle detected by the steering angle sensor  111 A. The angular velocity field has stored therein a value indicating the angular velocity of the steering angle detected by the steering angle sensor  111 A. 
       FIG. 6  illustrates an example of control information in the vehicle-mounted communication system according to the first embodiment of the present invention. 
     Referring to  FIG. 6 , the control information is constituted of a header, a direction field, a motor speed field, a drive amount field, and a delimiter in that order from the head. 
     The direction field, the motor speed field, and the drive amount field have stored therein values indicating the direction, motor speed, and drive amount, respectively, set by the control unit  111 B. 
     The processor  43  detects an abnormality related to the control network  10  based on data acquired by the communication unit  41 . 
     More specifically, for example, the processor  43  compares the value of the direction field in the sensor information and the value of the direction field in the control information stored in the storage unit  42  with each other to determine whether or not the direction of the steering angle matches the direction of the assistance. 
     Then, if the processor  43  determines that the direction of the steering angle does not match the direction of the assistance, the processor  43  creates an abnormality notification indicating an abnormality in the control unit  111 B, and transmits the created abnormality notification to the data acquisition device  131 B, serving as the acquisition source of the control information, via the communication unit  41  and the security network  20 . 
       FIG. 7  illustrates an example of the relationship between an angular velocity in sensor information and a motor speed in control information in the vehicle-mounted communication system according to the first embodiment of the present invention. In  FIG. 7 , the abscissa axis indicates the angular velocity in the sensor information, whereas the ordinate axis indicates the motor speed in the control information. 
     Referring to  FIG. 7 , the relationship between the angular velocity in the sensor information and the motor speed in the control information is a proportional relationship. 
     For example, if the value of the motor speed field in the control information is not included in a range between an upper limit L 1  and a lower limit L 2  shown in  FIG. 7  relative to the value of the angular velocity field in the sensor information, the processor  43  determines that the control unit  111 B is abnormal. 
     Then, the processor  43  creates an abnormality notification indicating the abnormality in the control unit  111 B, and transmits the created abnormality notification to the data acquisition device  131 B, serving as the acquisition source of the control information, via the communication unit  41  and the security network  20 . 
       FIG. 8  illustrates an example of the relationship between a drive amount based on a value of the angular velocity field in sensor information and a drive amount in control information in the vehicle-mounted communication system according to the first embodiment of the present invention. In  FIG. 8 , the abscissa axis indicates the drive amount based on the value of the angular velocity field in the sensor information, whereas the ordinate axis indicates the drive amount in the control information. 
     Referring to  FIG. 8 , the relationship between the drive amount based on the value of the angular velocity field in the sensor information, specifically, a value obtained by multiplying the value of the angular velocity field by a unit time period, namely, a predetermined time period, and the drive amount in the control information is a proportional relationship. 
     When the value of the drive amount field in the control information is not included in a range between an upper limit L 3  and a lower limit L 4  shown in  FIG. 8  relative to the value obtained by multiplying the value of the angular velocity field in the sensor information by the unit time period, namely, the predetermined time period, the processor  43  determines that the control unit  111 B is abnormal. 
     Then, based on the determination result, the processor  43  creates an abnormality notification indicating the abnormality in the control unit  111 B, and transmits the created abnormality notification to the data acquisition device  131 B, serving as the acquisition source of the control information, via the communication unit  41  and the security network  20 . 
     [Abnormality Detection Example 2] 
     For example, the processor  43  counts the number of pieces of control information received from the data acquisition device  131 B via the communication unit  41  during a predetermined time period. 
     The number of pieces of control information transmitted from the control unit  111 B becomes extremely large when, for example, the control unit  111 B is taken over or a DOS attack (denial of service attack) involving transmission of a large volume of illegal data is performed due to the control unit  111 B being replaced with an unauthorized functional unit. 
     For example, when the count value is larger than or equal to a predetermined threshold value, the processor  43  determines that the control unit  111 B is abnormal. 
     Then, the processor  43  creates an abnormality notification indicating the abnormality in the control unit  111 B, and transmits the created abnormality notification to the data acquisition device  131 B, serving as the acquisition source of the control information, via the communication unit  41  and the security network  20 . 
     For example, when an abnormality is detected by the management device  121 , the data acquisition device  131 B performs control related to the control network  10 . 
     More specifically, the receiver  33  in the data acquisition device  131 B receives the abnormality notification transmitted from the management device  121  via the wire harness  23 , and outputs the received abnormality notification to the processor  35  in the acquisition unit  31 . 
     [Control Example 1] 
     The processor  35  turns off the switch  34  in accordance with the abnormality notification received from the receiver  33 , so as to perform, for example, control for cutting off the control unit  111 B serving as the functional unit  111  indicated in the abnormality notification from the control network  10 . 
     More specifically, the processor  35  turns off the switch  34  to block the path used for transmitting control information from the control unit  111 B toward the drive unit  111 C in the data acquisition device  131 B. 
     Accordingly, the control information becomes non-transmittable to the drive unit  111 C, so that power steering becomes non-usable in the vehicle  1 . However, the driver of the vehicle  1  can continue to drive the vehicle  1  since the steering operation itself is still possible. 
     [Control Example 2] 
     For example, the processor  35  may be configured to perform control for switching paths in the control network  10  in accordance with the abnormality notification received from the receiver  33 . 
       FIG. 9  illustrates another example of a partial configuration of the vehicle-mounted communication system according to the first embodiment of the present invention. 
     As compared with the vehicle-mounted communication system  301  shown in  FIG. 2 , the vehicle-mounted communication system  301  shown in  FIG. 9  further includes a spare control unit  111 D, and also includes a data acquisition device  131 D, as one of the data acquisition devices  131 , in place of the data acquisition device  131 C. 
     The control unit  111 D receives an abnormality notification transmitted from the management device  121  and indicating an abnormality in the control unit  111 B, and starts performing operation. 
     More specifically, for example, the control unit  111 D receives an abnormality notification transmitted from the management device  121  and indicating an abnormality in the control unit  111 B, calculates a power-steering assistance amount based on sensor information received from the steering angle sensor  111 A, and creates control information containing the direction, motor speed, and drive amount for controlling the rotation of the motor  151  based on the calculated assistance amount. 
     Then, the control unit  111 D transmits the created control information to the drive unit  111 C via the data acquisition device  131 D. 
       FIG. 10  illustrates another example of the configuration of each data acquisition device according to the first embodiment of the present invention. 
     Referring to  FIG. 10 , as compared with the data acquisition device  131  shown in  FIG. 3 , the data acquisition device  131 D further includes a switch  36  provided in place of the switch  34  and connected to the control unit  111 D by a wire harness  24 . 
     The switch  37  in the data acquisition device  131 D is connected between the wire harness  21  and the wire harness  22  as well as between the wire harness  21  and the wire harness  24 . 
     The switch  36  switches between a mode for connecting the wire harness  22  to the wire harness  21  and a mode for connecting the wire harness  22  to the wire harness  24  in accordance with control of the processor  35 . 
     In the normal state, the processor  35  controls the switch  36  such that the connection destination for the wire harness  22  is the wire harness  21 . 
     Accordingly, in the normal state, control information from the wire harness  21  is transmitted to the wire harness  22 . Specifically, control information transmitted from the control unit  111 B is transmitted to the drive unit  111 C via the data acquisition device  131 B, the central gateway  101 , the wire harness  21 , the switch  36 , and the wire harness  22 . 
     The processor  35  controls the switch  36  in accordance with the abnormality notification received from the receiver  33  such that the connection destination for the wire harness  22  is the wire harness  24 . Accordingly, control information transmitted from the control unit  111 D is transmitted to the drive unit  111 C via the wire harness  24 , the switch  36 , and the wire harness  22 . 
     The data acquisition device  131  may be connected between the steering angle sensor  111 A and the control unit  111 D. 
     Furthermore, the data acquisition device  131  may be configured to include a relay unit in place of the switch  34  or the switch  36 . In this case, the processor  35  controls a relay in accordance with the abnormality notification received from the receiver  33 . 
     Moreover, the data acquisition device  131  may be configured not to include the switch  34  or the switch  36 . In this case, for example, the vehicle-mounted communication system  302  includes a junction box containing a plurality of switches corresponding to the switch  34  or the switch  36  in each data acquisition device  131 . Each data acquisition device  131  controls the switches in the junction box so as to perform control related to the control network  10 . The junction box may be configured to include the management device  121 . 
     Furthermore, the management device  121  performs control for notifying a vehicle occupant of an abnormality when such an abnormality is detected. 
     More specifically, the processor  43  in the management device  121  transmits the created abnormality notification to a display control device, as a functional unit  111  having a function for displaying the abnormality notification on a screen on the dashboard of the vehicle  1 , via the communication unit  41  and the security network  20 . 
     The display control device receives the abnormality notification transmitted from the management device  121  and performs a process for displaying the screen for notifying the vehicle occupant of the abnormality on, for example, a display on the dashboard of the vehicle  1  in accordance with the received abnormality notification. 
     Furthermore, for example, the processor  43  transmits the created abnormality notification mentioned above to an external communication device, such as a TCU, as a functional unit  111  capable of communicating wirelessly with a server outside the vehicle  1 , via the communication unit  41 . 
     The external communication device receives the abnormality notification transmitted from the management device  121  and transmits the received abnormality notification to a server set at a security operation center via a wireless base station by including the abnormality notification in a wireless signal compliant with a communication standard, such as LTE (Long Term Evolution) or 3G. 
     Accordingly the contents of the abnormality indicated in the abnormality notification are visualized at the security operation center, so that an operator can cope with the abnormality. 
     [Flow of Operation] 
     The devices in the vehicle-mounted communication system are each equipped with a computer that includes a memory. An arithmetic processor, such as a CPU, in the computer reads a program partially or entirely containing the steps of a following sequence diagram or flowchart from the memory and executes the program. The program for each of these plurality of devices can be installed from an external source. The program for each of these plurality of devices is distributed in a state where the program is stored in a storage medium. 
       FIG. 11  illustrates an example of a sequence of abnormality detection and abnormality-related processing in a power line communication system according to the first embodiment of the present invention.  FIG. 11  representatively illustrates the operation of one management device  121  and the operation of one of the data acquisition devices  131 . 
     Referring to  FIG. 11 , the data acquisition device  131  first acquires data, such as sensor information and control information, transmitted through the control network  10  (step S 101 ). 
     Then, the data acquisition device  131  transmits the acquired data to the management device  121  (step S 102 ). 
     Subsequently, the management device  121  receives the data transmitted from the data acquisition device  131  and detects an abnormality related to the control network  10  based on the received data (step S 103 ). 
     Then, if the management device  121  detects an abnormality related to the control network  10 , the management device  121  creates an abnormality notification indicating the abnormality, and transmits the created abnormality notification to the data acquisition device  131  (step S 104 ). 
     Subsequently, the data acquisition device  131  receives the abnormality notification transmitted from the management device  121 , and performs control related to the control network  10 , such as control for cutting off the functional unit  111  detected as being abnormal from the control network  10  and control for switching paths in the control network  10 , in accordance with the received abnormality notification (step S 105 ). 
     [Modification 1] 
       FIG. 12  illustrates a partial configuration in modification 1 of the vehicle-mounted communication system according to the first embodiment of the present invention. 
     Referring to  FIG. 12 , the vehicle-mounted communication system  301  according to modification 1 includes data acquisition devices  131 E,  131 F, and  131 G, as data acquisition devices  131 , in place of the data acquisition devices  131 A,  131 B, and  131 C, as compared with the vehicle-mounted communication system  301  shown in  FIG. 2 . The data acquisition devices  131 E,  131 F, and  131 G may also be referred to as data acquisition devices  131  hereinafter. 
     When the management device  121  detects an abnormality, the management device  121  controls the functional units  111  via the data acquisition devices  131 . 
     When the management device  121  detects an abnormality, the management device  121  changes the operation of the functional units  111  toward the safer side for the running of the vehicle  1 . 
     More specifically, when the management device  121  detects an abnormality in a functional unit  111 , the management device  121  controls another functional unit  111  that corresponds to the functional unit  111  detected as being abnormal. 
     In detail, when the management device  121  detects an abnormality in the control unit  111 B, the management device  121  performs control for stopping the supply of electric power to the drive unit  111 C that is to receive control information from the control unit  111 B. 
       FIG. 13  illustrates an example of the configuration of each data acquisition device in modification 1 of the vehicle-mounted communication system according to the first embodiment of the present invention. 
     Referring to  FIG. 13 , the data acquisition device  131 G further includes a switch  37 , as compared with the data acquisition device  131  shown in  FIG. 3 . 
     For example, the data acquisition device  131 G is supplied with electric power from a power supply unit (not shown) via a dedicated cable. The electric power from the power supply unit may be supplied to the data acquisition device  131  via any of the wire harnesses  21  to  23 . 
     The switch  37  is connected between a connector CN, which is supplied with the electric power from the power supply unit, and the wire harness  22 . 
     For example, the data acquisition device  131 G supplies the electric power from the power supply unit (not shown) to the corresponding functional unit  111  via the switch  37  and the wire harness  22  or via the switch  37  and a cable different from the wire harness  22 . 
     Referring to  FIGS. 12 and 13 , the management device  121  controls the switch  37  in the data acquisition device  131  so as to switch between a mode for supplying electricity to the corresponding functional unit  111  and a mode for not supplying electricity thereto. 
     More specifically, the switch  37  switches between a mode for connecting the connector CN and the wire harness  22  to each other and a mode for not connecting connector CN and the wire harness  22  to each other in accordance with control of the management device  121 . 
     In the normal mode, the processor  35  turns on the switch  37  to connect the connector CN and the wire harness  22  to each other. Accordingly, the electric power from the power supply unit is transmitted to the wire harness  22 . 
     In detail, when an abnormality in the control unit  111 B is detected, the processor  43  in the management device  121  creates a switch command for switching the switch  37  in the data acquisition device  131 G and transmits the created switch command to the switch  37  in the data acquisition device  131 G via the communication unit  41  and the wire harness  23 , so as to turn off the switch  37  in the data acquisition device  131 G. 
     Alternatively, for example, the processor  43  may transmit the switch command to the switch  37  in the data acquisition device  131 G via a cable different from the wire harness  23 . 
     Accordingly, the supply of electric power to the motor  151  in the drive unit  111 C is stopped so that the effect of illegal control information can be eliminated, thereby, for example, preventing a malfunction of the drive unit  111 C caused by illegal control information and causing the vehicle  1  to run on the safer side. In the vehicle  1 , power steering becomes non-usable. However, the driver of the vehicle  1  can continue to drive the vehicle  1  since the steering operation itself is still possible. 
     Alternatively, when the management device  121  detects an abnormality in a functional unit  111 , the management device  121  may be configured to control the functional unit  111  detected as being abnormal instead of being configured to control another functional unit  111  that corresponds to the functional unit  111  detected as being abnormal. 
     In detail, for example, when the management device  121  detects an abnormality in the control unit  111 B, the management device  121  may control the control unit  111 B. 
       FIG. 14  illustrates a sequence of abnormality detection and abnormality-related processing in modification 1 of the power line communication system according to the first embodiment of the present invention.  FIG. 14  representatively illustrates the operation of one management device  121  and the operation of one of the data acquisition devices  131 . 
     Referring to  FIG. 14 , the data acquisition device  131  first acquires data, such as sensor information and control information, transmitted through the control network  10  (step S 201 ). 
     Then, the data acquisition device  131  transmits the acquired data to the management device  121  (step S 202 ). 
     Subsequently, the management device  121  receives the data transmitted from the data acquisition device  131  and detects an abnormality related to the control network  10  based on the received data (step S 203 ). 
     Then, when the management device  121  detects an abnormality related to the control network  10 , the management device  121  creates a switch command for controlling the functional unit  111  corresponding to the abnormality, and transmits the created switch command to the data acquisition device  131 , thereby controlling the relevant functional unit  111  (step S 204 ). 
     [Modification 2] 
     The management device  121  may be configured to directly control the functional units  111  instead of being configured to control the functional units  111  via the data acquisition devices  131 . 
       FIG. 15  illustrates the configuration of modification 2 of the vehicle-mounted communication system according to the first embodiment of the present invention. 
     Referring to  FIG. 15 , the vehicle-mounted communication system  301  according to modification 2 includes the central gateway  101 , the plurality of functional units  111 , the management device  121 , and the plurality of data acquisition devices  131 . 
     The central gateway  101  and the functional units  111  are connected to each other by the control network  10 . 
     The management device  121  is connected to the central gateway  101 , the functional units  111 , and the data acquisition devices  131  by the security network  20 . 
     Each functional unit  111  includes a switch (not shown) equivalent to the switch  37  in each data acquisition device  131 . 
     The management device  121  controls the switch included in each functional unit  111 . More specifically, for example, when an abnormality in a functional unit  111  is detected, the processor  43  in the management device  121  creates a switch command and transmits the created switch command to the functional unit  111  via the communication unit  41  and the security network  20 , thereby turning off the switch in the functional unit  111 . 
     In the vehicle-mounted communication system according to the first embodiment of the present invention, when the management device  121  detects an abnormality, the management device  121  is configured to change the operation of the functional units  111  toward the safer side for the running of the vehicle  1  so as to allow the vehicle  1  to continue running. However, the configuration is not limited to this. When the management device  121  detects an abnormality, for example, the management device  121  may be configured to change the operation of the functional units  111  to cause the vehicle  1  to stop running. 
     Furthermore, in the vehicle-mounted communication system according to the first embodiment of the present invention, when the management device  121  detects an abnormality, the management device  121  is configured to perform control for notifying the vehicle occupant of the abnormality. However, the configuration is not limited to this. When the management device  121  detects an abnormality, the management device  121  may be configured not to provide an abnormality notification. 
     There is a demand for a technology that can establish a vehicle-mounted network with improved security over the technologies described in Patent Literature 1 and Patent Literature 2. 
     In this respect, in the vehicle-mounted communication system according to the first embodiment of the present invention, the plurality of functional units  111  are connected to the control network  10  in the vehicle  1 . The management device  121  is connected to the security network  20  in the vehicle  1 . The communication from the control network  10  to the security network  20  is partially limited. The data acquisition devices  131  acquire data transmitted through the control network  10  and transmit the data to the management device  121 . The management device  121  detects an abnormality related to the control network  10  based on the data received from the data acquisition devices  131 . 
     Accordingly, the communication is limited by isolating the control network  10  for transmitting information between the functional units  111  and the security network  20  for monitoring from each other, thereby detecting an abnormality in the vehicle  1  while achieving improved security by using the security network  20  in which the effect of the abnormality in the control network  10  is minimized. Moreover, with the management device  121  being configured to detect an abnormality, various types of abnormalities can be detected collectively in a single device. 
     Therefore, in the vehicle-mounted communication system according to the first embodiment of the present invention, a vehicle-mounted network with improved security can be established. 
     Furthermore, in the vehicle-mounted communication system according to the first embodiment of the present invention, each data acquisition device  131  performs control related to the control network  10  when an abnormality is detected by the management device  121 . 
     With this configuration, for example, transmission of illegal data through the control network  10  can be prevented, thereby reducing the effect of the abnormality. 
     Furthermore, in the vehicle-mounted communication system according to the first embodiment of the present invention, the data acquisition devices  131  perform control for cutting off the functional units  111  from the control network  10  when an abnormality is detected by the management device  121 . 
     According to this configuration, transmission paths for illegal data can be blocked. For example, transmission of illegal data from the functional unit  111  detected as being abnormal through the control network  10  can be prevented, and reception of illegal data by a normal functional unit  111  can be prevented. 
     Furthermore, in the vehicle-mounted communication system according to the first embodiment of the present invention, each data acquisition device  131  performs control for switching paths in the control network  10  when an abnormality is detected by the management device  121 . 
     According to this configuration, for example, another transmission path is used in place of the transmission path corresponding to the detected abnormality, so that the vehicle-mounted communication system  301  can continue to perform normal operation. 
     Furthermore, in the vehicle-mounted communication system according to the first embodiment of the present invention, when the management device  121  detects an abnormality, the management device  121  controls the functional units  111 . 
     According to this configuration, for example, the operation of the functional unit  111  detected as being abnormal can be stopped, or the operation of a normal functional unit  111  can be stopped to prevent the functional unit  111  from receiving illegal data, so that the effect of the abnormality can be reduced. 
     Furthermore, in the vehicle-mounted communication system according to the first embodiment of the present invention, when the management device  121  detects an abnormality, the management device  121  changes the operation of the functional units  111  toward the safer side for the running of the vehicle  1 . 
     According to this configuration, a malfunction of a functional unit  111  caused as a result of receiving illegal data can be suppressed, thereby ensuring stable running of the vehicle  1 . 
     Furthermore, in the vehicle-mounted communication system according to the first embodiment of the present invention, when the management device  121  detects an abnormality, the management device  121  performs control for providing an abnormality notification. 
     According to this configuration, for example, the driver of the vehicle  1  can recognize that inoperability is caused by an abnormality in the control network  10 , so as to be able to ascertain the situation in detail. 
     Furthermore, in each data acquisition device according to the first embodiment of the present invention, the communication from the control network  10  to the security network  20  is partially limited. The acquisition unit  31  acquires data transmitted through the control network  10 . The transmitter  32  transmits the data acquired by the acquisition unit  31  to the management device  121 . 
     Accordingly, the communication is limited by isolating the control network for transmitting information between the functional units and the security network for monitoring from each other, thereby detecting an abnormality in the vehicle while achieving improved security by using the security network in which the effect of the abnormality in the control network is minimized. Consequently, a vehicle-mounted network with improved security can be established. 
     Therefore, with the data acquisition devices according to the first embodiment of the present invention, a vehicle-mounted network with improved security can be established. 
     Furthermore, each data acquisition device according to the first embodiment of the present invention is a connector that connects between paths in the control network  10 . 
     According to this configuration, the data acquisition devices  131  can be readily retrofitted to, for example, a vehicle-mounted communication system equipped with existing functional units  111 , and the functional units  111  can be simplified. 
     In the management device according to the first embodiment of the present invention, the communication unit  41  acquires data transmitted through the control network  10 . The processor  43  detects an abnormality related to the control network  10  based on the data acquired by the communication unit  41 . 
     Accordingly, the communication is limited by isolating the control network  10  for transmitting information between the functional units  111  and the security network  20  for monitoring from each other, thereby detecting an abnormality in the vehicle  1  while achieving improved security by using the security network  20  in which the effect of the abnormality in the control network  10  is minimized. Moreover, various types of abnormalities can be detected collectively in a single device. 
     Therefore, in the management device according to the first embodiment of the present invention, a vehicle-mounted network with improved security can be established. 
     In a monitoring method in the vehicle-mounted communication system according to the first embodiment of the present invention, data transmitted through the control network  10  is first acquired. Then, the acquired data is transmitted to the management device  121 . Subsequently, the management device  121  detects an abnormality related to the control network  10  based on the received data. 
     Accordingly, the communication is limited by isolating the control network  10  for transmitting information between the functional units  111  and the security network  20  for monitoring from each other, thereby detecting an abnormality in the vehicle  1  while achieving improved security by using the security network  20  in which the effect of the abnormality in the control network  10  is minimized. Moreover, with the management device  121  being configured to detect an abnormality, various types of abnormalities can be detected collectively in a single device. 
     Therefore, in the monitoring method in the vehicle-mounted communication system according to the first embodiment of the present invention, a vehicle-mounted network with improved security can be established. 
     Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, identical or equivalent sections will be given the same reference signs, and the descriptions thereof will not be repeated. 
     Second Embodiment 
     This embodiment relates to a vehicle-mounted communication system in which the installation locations of the data acquisition devices are different from those in the vehicle-mounted communication system according to the first embodiment. Contents other than those to be described below are identical to those of the vehicle-mounted communication system according to the first embodiment. 
       FIG. 16  illustrates an example of the configuration of a vehicle-mounted communication system according to a second embodiment of the present invention. 
     Referring to  FIG. 16 , a vehicle-mounted communication system  302  includes the plurality of functional units  111  and the management device  121 . Each functional unit  111  includes a data acquisition device  132 . The plurality of functional units  111  include, for example, the central gateway  101  and a TCU (telematics communication unit). 
     The vehicle-mounted communication system  302  is mounted in the vehicle  1 . The plurality of functional units  111  excluding the central gateway  101  are connected to the central gateway  101  by the control network  10 , such as a CAN (controller area network) (registered trademark) bus compliant with the CAN standard or an Ethernet (registered trademark) cable. 
     The management device  121  is connected to the data acquisition devices  132  by the security network  20 . 
       FIG. 17  illustrates an example of a partial configuration of the vehicle-mounted communication system according to the second embodiment of the present invention. 
     Referring to  FIG. 17 , the steering angle sensor  111 A, the control unit  111 B, and the central gateway  101  as examples of the functional units  111  are connected to one another by the control network  10 . 
     Furthermore, the central gateway  101  and the drive unit  111 C as examples of the functional units  111  are connected to each other by the control network  10 . The drive unit  111 C has the motor  151  for assisting with the steering operation. 
     Moreover, a data acquisition device  132 A is included in the steering angle sensor  111 A. A data acquisition device  132 B is included in the control unit  111 B. A data acquisition device  132 C is included in the drive unit  111 C. 
     Each data acquisition device  132  acquires data transmitted through the control network  10 . 
       FIG. 18  illustrates an example of the configuration of each data acquisition device according to the second embodiment of the present invention. 
     Referring to  FIGS. 17 and 18 , the data acquisition device  132 C includes an acquisition unit  51 , a transmitter  52 , a receiver  53 , and a switch  54 . The acquisition unit  51  includes a processor  55 . The data acquisition device  132 C is connected to the central gateway  101  by the wire harness  21  used as the control network  10 , and is connected to the management device  121  by the wire harness  23  used as the security network  20 . 
     Control information transmitted from the control unit  111 B is transmitted via the central gateway  101  to a processor (not shown) in, for example, the drive unit  111 C via the wire harness  21  and the switch  54  in the data acquisition device  132 C. 
     The switch  54  in the data acquisition device  132 C is connected between the wire harness  21  and the processor in the drive unit  111 C. 
     The switch  54  switches between a connected mode and a non-connected mode between the wire harness  21  and the processor in the drive unit  111 C in accordance with control of the processor  55 . 
     In the normal state, the processor  55  turns on the switch  54  to connect the wire harness  21  and the processor in the drive unit  111 C to each other. Accordingly, the control information from the wire harness  21  is transmitted to the processor in the drive unit  111 C. 
     The acquisition unit  51  in the data acquisition device  132 C acquires the control information transmitted through the data acquisition device  132 C between the wire harness  21  and the switch  54 . 
     Then, the processor  55  in the acquisition unit  51  counts the number of pieces of control information acquired by the acquisition unit  51  within a predetermined time period. 
     Subsequently, the processor  55  detects an abnormality related to the control network  10  based on the acquired data. 
     More specifically, when the count value indicating the number of pieces of control information is larger than or equal to a predetermined threshold value, the processor  55  determines that the control unit  111 B is abnormal. In other words, the processor  55  detects an abnormality in the control unit  111 B and outputs the detection result to the transmitter  52 . 
     The transmitter  52  transmits the detection result received from the processor  55  to the management device  121  via the wire harness  23 . 
     The management device  121  receives the detection result transmitted from the transmitter  52  in the data acquisition device  132 C via the wire harness  23  and performs a process according to the received detection result. 
     More specifically, the processor  43  in the management device  121  receives the detection result transmitted from the data acquisition device  133 C via the wire harness  23  and the communication unit  41 . 
     The processor  43  creates an abnormality notification indicating the abnormality in the control unit  111 B based on the received detection result, and transmits the created abnormality notification to the data acquisition device  132 C, serving as the acquisition source of the control information, via the communication unit  41  and the wire harness  23 . 
     The receiver  53  in the data acquisition device  132 C receives the abnormality notification transmitted from the management device  121  via the wire harness  23 , and outputs the received abnormality notification to the processor  55  in the acquisition unit  51 . 
     The processor  55  turns off the switch  54  in accordance with the abnormality notification received from the receiver  53 , so as to perform control for cutting off the drive unit  111 C serving as the functional unit  111  indicated in the abnormality notification from the control network  10 . 
     More specifically, the processor  35  turns off the switch  54  to block the path used for transmitting control information from the control unit  111 B toward the drive unit  111 C in the data acquisition device  132 C. Accordingly, the control information becomes non-transmittable to the processor in the drive unit  111 C. 
       FIG. 19  illustrates an example of a sequence of abnormality detection and abnormality-related processing in a power line communication system according to the second embodiment of the present invention.  FIG. 19  representatively illustrates the operation of one management device  121  and the operation of one of the data acquisition devices  132 . 
     Referring to  FIG. 19 , the data acquisition device  132  first acquires data transmitted through the control network  10  (step S 301 ). 
     Then, if the data acquisition device  132  detects an abnormality related to the control network  10  based on the acquired data (step S 302 ), the data acquisition device  132  transmits the detection result to the management device  121  (step S 303 ). 
     Subsequently, the management device  121  receives the detection result transmitted from the data acquisition device  132 , creates an abnormality notification indicating the abnormality in the corresponding functional unit  111  in accordance with the received detection result, and transmits the created abnormality notification to the data acquisition device  132  (step S 304 ). 
     Then, the data acquisition device  132  receives the abnormality notification transmitted from the management device  121 , and performs control related to the control network  10 , such as control for cutting off the functional unit  111  detected as being abnormal from the control network  10 , in accordance with the received abnormality notification (step S 305 ). 
     In the power line communication system according to the second embodiment of the present invention, the data acquisition device  132  is configured to perform control for cutting off the functional unit  111  indicated in the abnormality notification from the control network  10  as the control related to the control network  10 . However, the configuration is not limited to this. The data acquisition device  132  may be configured to perform control for switching paths in the control network  10  as the control related to the control network  10 . 
     Furthermore, in the power line communication system according to the second embodiment of the present invention, the management device  121  is configured to transmit an abnormality notification to the data acquisition device  132  as a process according to a detection result. However, the configuration is not limited to this. The management device  121  may be configured to control the functional unit  111  indicated in the detection result or another functional unit  111  corresponding to the functional unit  111  indicated in the detection result as the process according to the detection result. 
     In detail, in order to block the supply of electric power to the functional unit  111  indicated in the detection result, for example, the management device  121  may transmit, to the functional unit  111 , a switch command for switching the switch included in the functional unit  111 . 
     Accordingly, in the vehicle-mounted communication system according to the second embodiment of the present invention, the plurality of functional units  111  are connected to the control network  10  in the vehicle  1 . Each data acquisition device  132  is communicable with the management device  121  connected to the security network  20  in the vehicle  1 . In the vehicle-mounted communication system according to the second embodiment of the present invention, communication from the control network  10  to the security network  20  is partially limited. The data acquisition device  132  acquires data transmitted through the control network  10 . The data acquisition device  132  is a connector that connects between paths in the control network  10  and detects an abnormality related to the control network  10  based on the acquired data. 
     Accordingly, the communication is limited by isolating the control network  10  for transmitting information between the functional units  111  and the security network  20  for monitoring from each other, thereby detecting an abnormality in the vehicle  1  while achieving improved security by using the security network  20  in which the effect of the abnormality in the control network  10  is minimized. Moreover, with each data acquisition device  131  being configured to detect an abnormality, the processing load in the vehicle-mounted communication system  301  can be distributed. Moreover, the data acquisition devices  131  can be readily retrofitted to, for example, a vehicle-mounted communication system equipped with existing functional units  111 , and the functional units  111  can be simplified. 
     Accordingly, in the vehicle-mounted communication system according to the second embodiment of the present invention, a vehicle-mounted network with improved security can be established. 
     Furthermore, in the vehicle-mounted communication system according to the second embodiment of the present invention, the data acquisition devices  132  are included in the functional units  111 . 
     According to such a configuration, the configuration of the vehicle-mounted communication system  301  can be simplified. 
     Furthermore, in a monitoring method in the vehicle-mounted communication system according to the second embodiment of the present invention, each data acquisition device  132  first acquires data transmitted through the control network  10 . Then, the data acquisition device  132  detects an abnormality related to the control network  10  based on the acquired data. 
     Accordingly, the communication is limited by isolating the control network  10  for transmitting information between the functional units  111  and the security network  20  for monitoring from each other, thereby detecting an abnormality in the vehicle  1  while achieving improved security by using the security network  20  in which the effect of the abnormality in the control network  10  is minimized. Moreover, with each data acquisition device  131  being configured to detect an abnormality, the processing load in the vehicle-mounted communication system  301  can be distributed. 
     Therefore, in the monitoring method in the vehicle-mounted communication system according to the second embodiment of the present invention, a vehicle-mounted network with improved security can be established. 
     Since other components and operation are identical to those in the vehicle-mounted communication system according to the first embodiment, detailed descriptions will not be repeated here. 
     It should be regarded that the above embodiments are exemplary in all aspects and are not limitative. The scope of the present invention is indicated not by the above description but by the claims, and is intended to include all changes within the meaning and scope equivalent to the scope of the claims. 
     The above description includes the following additional features. 
     [Additional Item 1] 
     A vehicle-mounted communication system mounted in a vehicle, comprising: a plurality of functional units connected to a control network in the vehicle; and a management device connected to a security network in the vehicle, wherein communication from the control network to the security network is partially limited, 
     wherein the vehicle-mounted communication system further comprises: 
     a data acquisition device that acquires data transmitted through the control network and transmits the data to the management device, 
     wherein the management device detects an abnormality related to the control network based on the data received from the data acquisition device, and 
     wherein the data acquisition device acquires the data and transmits the data to the management device via the security network. 
     [Additional Item 2] 
     A vehicle-mounted communication system mounted in a vehicle, comprising: 
     a plurality of functional units connected to a control network in the vehicle; and 
     a data acquisition device that is communicable with a management device connected to a security network in the vehicle and that acquires data transmitted through the control network, 
     wherein communication from the control network to the security network is partially limited, 
     wherein the data acquisition device is a connector that connects between paths in the control network and detects an abnormality related to the control network based on the acquired data, and 
     wherein the data acquisition device transmits a detection result to the management device via the security network. 
     [Additional Item 3] 
     A data acquisition device in a vehicle-mounted communication system mounted in a vehicle, the vehicle-mounted communication system having a plurality of functional units connected to a control network and a management device connected to a security network, 
     wherein communication from the control network to the security network is partially limited, 
     wherein the data acquisition device comprises: 
     an acquisition unit that acquires data transmitted through the control network; and 
     a transmitter that transmits the data acquired by the acquisition unit to the management device, and 
     wherein the transmitter transmits the data to the management device via the security network. 
     [Additional Item 4] 
     A management device in a vehicle-mounted communication system mounted in a vehicle, the management device being connected to a security network, wherein, in the vehicle, a plurality of functional units are connected to a control network and communication from the control network to the security network is partially limited, the management device comprising: 
     a communication unit that acquires data transmitted through the control network; and 
     a processor that detects an abnormality related to the control network based on the data acquired by the communication unit, 
     wherein the communication unit acquires data transmitted via the security network. 
     REFERENCE SIGNS LIST 
     
         
         
           
               10  control network 
               20  security network 
               21 ,  22 ,  23 ,  24  wire harness 
               31 ,  51  acquisition unit 
               32 ,  52  transmitter 
               33 ,  53  receiver 
               34 ,  36 ,  37 ,  54  switch 
               35 ,  43 ,  55  processor 
               41  communication unit 
               42  storage unit 
               101  central gateway 
               111  functional unit 
               121  management device 
               131 ,  132  data acquisition device 
               141  substrate 
               301 ,  302  vehicle-mounted communication system