JP2015053568A - Communication controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a delay of a message during gateway communication in spite of priority by ID.SOLUTION: For controlling a transmission order of a message, an order of priority is applied to the message to be transmitted. When ID of all the messages to be transmitted are compared and the plurality of messages whose ID are overlapped are detected, transmission delay is determined to occur, and the order of priority of the message is changed so that the message which is kept for long time is preferentially transmitted in time series among the plurality of messages.

Description

  The present invention relates to an in-vehicle communication control apparatus, and more particularly to a communication control apparatus that is connected to an in-vehicle network that uses a communication method for transmitting and receiving messages according to a priority order according to an identifier and that transmits a plurality of messages having different priority orders.

    CAN communication and LIN communication are common as communication methods in an in-vehicle network. In these in-vehicle networks, electronic control units (ECUs) that perform transmission and reception are electrically connected by a bus. In CAN communication, an ID identifier is added to communication data to compose a message, and the priority order is determined according to the numerical value of the ID. The ID and the ECU to transmit and the ECU to receive are determined at the time of designing the in-vehicle network and are installed in each ECU.

    The ECU converts the message into an electrical signal and transmits it on the bus. Each ECU monitors an electrical signal on the bus, acquires an ID during communication, and specifies a message to be received.

    When multiple ECUs transmit at the same time on the same bus, the ID is sent from each ECU at the same time, and the ID on the bus is judged, and the message with the ID with the highest priority gets the transmission right. Transmits the communication data, and the other units wait until the completion of the communication of the high priority message. For this reason, when there are many communications with high priority, the transmission opportunity of ID with low priority decreases. In particular, when a message with a high priority is sent more frequently than a message with a low priority, a transmission delay of a message with a low priority occurs, and if the transmission delay continues for a long time, the ECU determines that communication is impossible. There is a possibility of misjudgment as a network failure.

    On the other hand, when there are a plurality of in-vehicle networks on the vehicle, gateway ECUs connected to both networks are used to enable communication between ECUs that are not directly connected across the networks. The gateway ECU transmits data received from one in-vehicle network to the other in-vehicle network.

    Especially in the case of gateway ECU, when the load on the sending network is higher than the load on the receiving network, the frequency of receiving messages from the receiving network and the sending frequency of messages to the sending network are balanced. Otherwise, message transmission may be delayed. It is difficult to dynamically consider the load for multiple in-vehicle networks and gateways during design.

    Thus, as a technique for reducing communication delay when the ECU performs gateway communication, Patent Document 1 discloses monitoring the bus load of the CAN network and adjusting the relay processing of the gateway ECU.

    Patent Document 2 discloses that when message transmission via the CAN network fails, the message transmission is stopped and another message with a higher priority is transmitted.

JP 2006-287738 A JP 2003-115852 JP

    When the gateway ECU communicates with the gateway and the transmission timing conflicts with other ECUs on the destination network, whether or not to send a message that is scheduled to be sent is determined by the ID of the other ECU's message and the ID of the gateway ECU's scheduled transmission message. Determined by priority.

    When the gateway ECU cannot transmit the scheduled transmission message, the gateway ECU waits until the bus is ready for transmission and performs transmission again. During this time, the data received from the reception source network is stored in the internal memory of the gateway ECU, and after being ready for transmission, it is sequentially read from the internal memory and transmitted.

    If the state of waiting for transmission continues, the time required until the message stored in the internal memory is transmitted from the gateway ECU becomes long, and there is a possibility that the message is delayed or thinned out.

    In the case of using the technique described in Patent Document 1, in order to monitor the bus load, the bus load monitoring unit needs to grasp communication information about messages of all IDs on the network in advance. For this reason, the resources of the nonvolatile memory of the gateway ECU are consumed. The bus load monitoring means consumes CPU resources because it receives all the messages on the network and makes the determination.

    When the technique described in Patent Document 2 is used, it is possible to prevent a delay of a high priority message, but a low priority message cannot obtain a transmission right, and a delay of a low priority message is not eliminated. .

    In the case where a message delay occurs, it is necessary to prevent the delay regardless of the priority based on the ID, and the present invention was invented in view of such a problem.

  In order to solve the above problems, a communication control apparatus according to the present invention includes a message transmission unit that performs a transmission process of a message including an identifier that specifies a communication destination of data on an in-vehicle network, and a plurality of messages before transmission by the message transmission unit. Storage means for assigning and storing a priority order, transmission message selection means for selecting a transmission target by the message transmission means based on the priority order given from the messages stored in the storage means, In the communication control apparatus comprising: a delay determining unit that determines a message in which a transmission delay is generated by the message transmitting unit from among messages stored in the storage unit; and a delay is generated by the transmission detecting unit. Raise the priority of messages that are determined to be higher than those that have no delay Comprising the previous priority changing means.

    According to the present invention, when transmission delay is determined to occur, transmission is preferentially performed from messages held in the ECU for a long time, so transmission delay is reduced even for messages with low priority. Is possible.

  Further, according to the present invention, even when the priority of a message scheduled to be transmitted is changed while the transmission right on the bus is not obtained, the message with the highest priority is immediately transmitted. It is possible to start.

It is a block diagram of a vehicle-mounted network. It is a block diagram of gateway ECU. It is a figure showing the procedure of the update software of a transmission queue. It is a figure showing the update of a transmission queue. FIG. 10 is a diagram illustrating a software procedure for update processing of a transmission waiting table according to the second embodiment. FIG. 10 is a diagram illustrating an update of a transmission waiting table relating to the second embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a vehicle configuration to which one embodiment of the present invention is applied. The vehicle has two networks, a network 110 and a network 120. The network 110 and the network 120 are connected to the vehicle-mounted ECUs 111, 112, 121, and 122, which are nodes of the network, by an electrically independent bus 113 and a bus 123, respectively.

    As the network protocol, CAN communication, LIN communication, or FlexRay communication is used. In CAN communication, an ID identifier is added to communication data to compose a message, and the priority order is determined according to the numerical value of the ID. The ID that is the priority of each message, the ECU to be transmitted and the ECU to be received are determined at the time of designing the in-vehicle network, and are stored in the memory of each ECU. Each ECU monitors an electrical signal on the bus, acquires an ID during communication, and specifies a message to be received.

    When messages are sent simultaneously from multiple ECUs on the network, the ECU with the highest priority ID sends, and the other ECUs wait until the bus is free. That is, data with higher priority IDs can communicate without delay, and data with lower priority IDs is more likely to be delayed.

    The in-vehicle ECU 111 and the in-vehicle ECU 112 are electrically connected to the bus 113 and are not electrically connected to the bus 123. On the other hand, the in-vehicle ECU 121 and the in-vehicle ECU 122 are electrically connected to the bus 123 and are not electrically connected to the bus 113.

    The gateway ECU 100 is electrically connected to both the bus 113 and the bus 123. For this reason, the gateway ECU 100 enables data communication from the in-vehicle ECU 111 to the in-vehicle ECU 122 by receiving data on the bus 113 and transmitting it to the bus 123, for example. This is the gateway communication performed by the gateway ECU 100 between the in-vehicle network 110 and the in-vehicle network 120.

  FIG. 2 shows the configuration of the gateway ECU 100 for performing gateway communication. Although FIG. 2 shows gateway communication from the in-vehicle network 110 to the in-vehicle network 120, bidirectional gateway communication is possible by adding a configuration from the in-vehicle network 120 to the in-vehicle network 110 in the gateway ECU 100.

  The message 220 received from the ECU on the in-vehicle network 110 via the bus 113 is stored in the reception buffer 200 by the receiver 205. The message 220 is transmitted to the bus 123 as the message 228, but the in-vehicle network 110 and the in-vehicle network 120 are independent, and the ID of the message 220 is changed to the transmission ID designed in the in-vehicle network 120.

    The gateway ECU 100 holds the relationship between the ID of the in-vehicle network 110 and the ID of the in-vehicle network 120 in each message as an ID conversion table 210 on the ROM or RAM. The ID conversion process 202 converts the ID of the message 221 in the reception buffer 202 into a corresponding ID on the network 120 using the ID conversion table 210 and outputs it as a message 222. For example, if the ID of the message 221 is ID11, the message 222 is converted to ID23 after being converted.

    The message 222 is registered in the normal transmission queue 211 by the algorithm of the transmission wait table update process 203. If it is determined that the message is delayed, the delayed message in the normal transmission queue 211 is registered in the delay transmission queue 212.

    The transmission process 204 stores the message at the head of the delayed transmission queue 212 in the transmission buffer 201 when the transmission buffer 201 is empty. When the delay transmission queue 212 is empty, the first message in the normal transmission queue 211 is stored in the transmission buffer 201.

    The transmitter 206 attempts transmission with the ID of the transmission buffer 201 to the bus 123, and when the transmission right is acquired according to the priority order with other ECUs, transmits a message of the transmission buffer 201 and clears the transmission buffer 201.

    Upon completion of transmission, the transmission process 204 deletes the corresponding message in the delayed transmission queue 212 or the normal transmission queue 211. As a result, the priority of the message in the corresponding queue is incremented one by one.

    Since the transmission buffer 201 is empty, the transmission process 204 repeats transmission of the next message.

    While there is no delay, the message 227 scheduled to be transmitted cannot acquire the transmission right and is waiting for transmission to the bus 123, there is a new reception from the bus 113, and the delayed transmission queue is updated. In this case, the transmission process 204 may cancel the current transmission and update the transmission buffer 201 with the message in the delayed transmission queue. By this processing, when a delay occurs, the operation can be immediately shifted to an operation for reducing the delay, and the delay can be reduced.

Next, FIG. 3 shows an algorithm of the transmission wait table update process 203.
The process 301 acquires the transmission ID of the message 222, and in the process 302, searches the normal transmission queue 211 using the transmission ID of the message 222 as a key, and tries to acquire a message with the same ID.

    In process 303, it is determined whether or not a message with the same ID can be acquired. If acquired, the process proceeds to process 304. On the other hand, if a message with the same ID cannot be acquired, the process proceeds to process 306.

    In processing 304 and processing 305, since an existing message with the same ID is detected, it is determined that there is a possibility of communication delay due to data stagnation in this gateway ECU 100, and processing for reducing delay is performed. I do.

    In process 304, an existing message with the same ID is deleted from the normal transmission queue 211, and the normal transmission queue 211 is updated. In process 305, an existing message with the same ID is added to the end of the delayed transmission queue 212.

    In the process 306, the message 222 is added to the normal transmission queue 211. In this embodiment, since messages received from the reception source network are transmitted to the transmission destination network in the order of reception, a queue for adding messages to the end of the table is employed as the table. The normal transmission queue 211 and the delayed transmission queue 212 may be tables that employ priority orders based on IDs.

    FIG. 4 is a diagram illustrating the transmission wait table as a result of applying the algorithm of the transmission wait table update process 203 in FIG. 3 in time series.

    At time t1, message 401, message 410, and message 411 are stored in normal transmission queue 211, and message 401 at the head of normal transmission queue 211 is copied to transmission buffer 201.

    At time t2, a message 402 transmission request is generated by the ID conversion processing 202 before the message 401 is transmitted. The ID 45 of the message 402 is searched from the normal transmission queue 211. As a result, since the message 410 has the same ID, it is determined that the same ID exists. In order to give priority to the transmission operation of the message 410, the message 410 is deleted from the normal transmission queue 211 and moved to the delayed transmission queue 212. On the other hand, the message 402 is added to the end of the normal transmission queue 211.

    Since the head of the delayed transmission queue 212 has been updated, transmission of the message 401 is canceled and the transmission buffer 201 is updated with the message 410. Thereby, the transmission operation of the message 410 is started, and the message 410 is transmitted when the transmission right to the bus is obtained.

    Next, at time t3, before the message 410 is transmitted, a transmission request for the message 403 is generated from the ID conversion processing 202. The normal transmission queue 211 is searched for ID 28 which is the ID of the message 403. As a result, since the message 411 has the same ID, it is determined that the same ID exists. In order to give priority to the transmission operation of the message 411, the message 411 is deleted from the normal transmission queue 211 and moved to the end of the delayed transmission queue 212. Since the message 410 has already been registered in the delay transmission queue 212, and it can be considered that the delay time is long in the first-come-first-served basis, the registration of the message from the normal transmission queue 211 is performed in the delay transmission queue 212. To the end of.

    In this case, since the head of the delayed transmission queue 212 has not been updated, the transmission buffer 201 is not updated.

    In this way, even if a message with an ID with a low priority becomes a bottleneck, gateway transmission is delayed, and the number of messages waiting to be transmitted in the gateway ECU increases, the device according to this embodiment gives priority to the message with the delay. Therefore, the delay can be reduced.

  In addition, even for a communication whose cycle is not constant, the transmission priority is changed when a message waiting for transmission is duplicated in the gateway ECU, so that the message delay can be eliminated.

Next, a second embodiment of the present invention will be shown. The target network is the same as in the first embodiment. FIG. 5 shows the configuration of the gateway ECU 100 of the second embodiment.
The difference from the first embodiment is the method for managing the priority of messages.
In the second embodiment, the priority of message transmission is managed using a transmission waiting table 511 which is a table on a memory.
The transmission waiting table 511 holds priority, transmission ID, and message data for a message scheduled to be transmitted.

    The transmission wait table update processing 503 updates the transmission wait table 511 when a new message is received from the bus 113 and the message 222 is transmitted. The transmission wait table update processing 503 first searches for a message having the same ID as the message 222 in the transmission wait table 511. If there is no message with the same ID, the lowest priority is added to the message 222 and stored in the transmission wait table 511. If there is a message with the same ID, for example, if the message 2113 is the transmission ID 45, the priority of the message 2113 is set to the priority next to the delay number 505, and the delay number 505 is incremented. Details are shown in FIG.

    The transmission process 504 sets the transmission waiting state by copying the messages in the transmission waiting table 511 to the transmission buffer 201 in the descending order of priority. A message waiting for transmission is transmitted to the bus 123 when the transmission right of the bus 123 is obtained. When it is detected that the transmission is completed and the transmission buffer 201 is empty, the transmission process 504 decrements the delay number 505 when the delay number 505 is zero or more.

  Next, FIG. 6 shows the transmission processing of the second embodiment in time series.

  It is assumed that there is no transmission delay at time t1. In the transmission waiting table 511, the priority 1 having the highest priority is the message 601, the priority 2 is the message 602, and the message having the lowest priority at this time is the message 603. A message 601 with a priority of 1 is stored in the transmission buffer 201, and when a transmission right on the bus is obtained, it is transmitted on the bus.

  When there is a transmission request for the message 604 from the ID conversion processing 202 at time t2, a message having the same ID as the message 604 is searched from the transmission waiting table 511. In this case, the message 603 is applicable. Therefore, the priority level of the message 603 is set to priority level 1, and the priority levels of the messages 601 and 602 are sequentially decreased and updated. Then, the message 604 is stored in the transmission waiting table 511 as the priority 4 having the lowest priority. Since the message 603 and the message 604 have the same ID, it is determined as a transmission delay, and the transmission delay number 505 is incremented.

  Since the priority level 1 message in the transmission waiting table 511 is changed, the transmission buffer is updated with the message 603. As a result, the message 603 is preferentially transmitted.

  Next, at time t3, when there is a transmission request for the message 605 from the ID conversion process 202, the transmission waiting table 511 is searched for a message having the same ID as the message 605. In this case, the message 602 corresponds. At this time, since the transmission delay number 505 is 1, the priority of the message 602 is set to priority 2. As a result, the transmission of the most delayed message 603 is continued.

  Next, when transmission of the message 603 is completed at time t4, the transmission buffer 201 becomes empty, the message 603 is deleted from the transmission waiting table 511, and priority of other messages is given priority one by one. Update. Since the transmission delay number 505 is 1 or more, it means that the delay of the message that has been transmitted is eliminated, and the transmission delay number 505 is decremented. On the other hand, since the message of priority 1 is changed to the message 602, the message 602 is stored in the transmission buffer 201, and the transmission standby state is entered.

  According to the second embodiment described above, since the transmission priority is changed when a message waiting for transmission is duplicated in the ECU with respect to a message whose transmission is delayed, it is effective in eliminating the transmission delay.

DESCRIPTION OF SYMBOLS 110 ... Network, 120 ... Network, 111 ... In-vehicle ECU, 112 ... In-vehicle ECU, 113 ... In-vehicle ECU, 114 ... In-vehicle ECU, 113 ... Bus, 123 ... Bus 203, transmission waiting table update processing, 211 ... normal transmission queue, 212 ... delayed transmission queue

Claims (4)

A message transmission means for performing transmission processing of a message including an identifier for specifying a communication destination of data in an in-vehicle network;
Storage means for assigning and storing priorities for a plurality of messages before transmission by the message transmission means;
In a communication control apparatus comprising: a transmission message selection unit that selects a transmission target by the message transmission unit based on a priority given from messages stored in the storage unit;
A delay determination unit that determines a message in which a transmission delay is generated by the message transmission unit from among the messages stored in the storage unit;
A communication control apparatus comprising: priority changing means for raising a priority of a message determined to have a delay by the transmission detection means over a message having no delay. A message transmission means for performing transmission processing of a message including an identifier for specifying a communication destination of data in an in-vehicle network;
Gateway communication means for transmitting a message received on one in-vehicle network to another in-vehicle network;
Storage means for assigning and storing priorities for a plurality of messages before transmission by the message transmission means;
In a communication control apparatus comprising: a transmission message selection unit that selects a transmission target by the message transmission unit based on a priority given from messages stored in the storage unit;
A delay determination unit that determines a message in which a transmission delay is generated by the message transmission unit based on a comparison between a message received on the certain in-vehicle network and a message stored in the storage unit;
A communication control apparatus comprising: priority changing means for raising a priority of a message determined to have a delay by the transmission detection means over a message having no delay. In the communication control device according to claim 1 or 2,
The delay determination unit determines a message in which a delay has occurred by detecting a duplicate identifier from a message stored in the storage unit or a message received on the certain in-vehicle network. Communication control device. 3. The communication control device according to claim 1, wherein the communication control device temporarily stores the message selected by the transmission message selection unit before the transmission processing is performed by the message transmission unit. 4. Transmission buffer means for
The storage means holds the message even after storing the message in the transmission buffer means,
The communication control apparatus characterized in that the priority changing means stores a message in which the priority of the message stored in the storage means is increased in the transmission buffer means.