JP7044081B2 - In-vehicle communication system - Google Patents

Description

The present invention relates to a communication system mounted on a vehicle or the like.

The vehicle is equipped with a communication system including a plurality of in-vehicle devices called ECUs (Electronic Control Units) and a relay device to which the ECUs are connected. In the communication system, the ECUs communicate with each other via the relay device. In such a communication system, as an example, an Ethernet (registered trademark) standard can be adopted, and a switching hub can be used as a relay device.

In the switching hub, the received messages are temporarily stored in the buffer, and the messages are transmitted in the order determined according to the priority of the messages and the like. Non-Patent Document 1 discloses an evaluation method of a weighted round robin method, which is a method of determining the transmission order of messages.

"Improved Formal Worst-Case Timing Analysis of Weighted Round Robin Scheduling for Ethernet", Published in: 2013 1nternational Conference on Hardware / Software Codesign and System Synthesis (CODES + ISSS), Publisher: IEEE, Electronic ISBN: 9781-4799- 1417-3, NSPEC Accession Number: 13895801.

The switching hub sequentially sends the messages stored in the buffer to the destination ECU and erases the sent messages from the buffer. However, when many messages are received at the same time, the size of the buffer becomes insufficient and the received messages are sent. Not all can be remembered and there is a risk of losing the message. Therefore, it is necessary to increase the size of the buffer sufficiently to prevent message loss. However, increasing the size of the buffer increases the cost of the switching hub.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an in-vehicle communication system that suppresses message loss in a switching hub and reduces costs.

In order to solve the above problems, one aspect of the present invention is an in-vehicle communication system including a switching hub and a plurality of ECUs connected to the switching hub and capable of communicating with each other, each of the plurality of ECUs. , A message generation unit that generates a message to be transmitted to any of the other ECUs, a communication unit that communicates with the other ECU, and a timing for controlling communication between the communication unit and the other ECU and transmitting a message. The communication control unit includes the communication control unit for determining the above, and the communication control unit generates message information which is information for specifying the priority of the message within a predetermined arbitration period, and sends the message information of its own ECU to each of the other ECUs. The timing of transmitting, receiving the message information of the other ECU from each of the other ECUs, and transmitting the message based on the message information of the own ECU and the other ECUs according to the rules common to the other ECUs is arbitrated. It is an in-vehicle communication system that determines that at least a part of the communication system does not overlap with each other within a predetermined communication period after the period.

As described above, according to the present invention, it is possible to provide an in-vehicle communication system with reduced costs while suppressing message loss in a switching hub.

Configuration diagram of the communication system according to the embodiment of the present invention Functional block diagram of ECU according to one embodiment of the present invention A flowchart showing a process according to an embodiment of the present invention.

In the communication system according to the present invention, a plurality of ECUs connected to a switching hub determine the transmission timing of each message so that at least a part thereof does not overlap with each other. As a result, it is possible to reduce the size required for the buffer provided in the switching hub for temporarily storing untransmitted messages.

(Embodiment)
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

<Structure>
FIG. 1 shows a part of the configuration of the communication system 1 according to the present embodiment. The communication system 1 is mounted on a vehicle as an example. The communication system 1 is a wired communication system adopting an Ethernet (registered trademark) standard as an example, and includes ECUs 11 to 16 and a switching hub 20. The number of ECUs is set to 6 in FIG. 1, but is not limited. Each of the ECUs 11 to 16 is connected to the switching hub 20, and can send and receive messages to and from each other via the switching hub 20. When the switching hub 20 receives a message from each of the ECUs 11 to 16, the switching hub 20 stores the message in the built-in buffer. The switching hub 20 identifies the destination ECU by referring to the information for specifying the destination included in the message, and transmits the message to the specified ECU. The buffer is used for temporary storage of messages that have not been transmitted, and the switching hub 20 deletes the messages from the buffer when the transmission of the messages is completed.

FIG. 2 is a functional block diagram showing the configurations of ECUs 11 to 16. The ECUs 11 to 16 have the same configuration, and all include a message generation unit 101, a communication control unit 102, a message buffer 103, a message information table 104, and a communication unit 105.

The message generation unit 101 generates a message to be transmitted to another ECU. The message generation unit 101 is, for example, an execution unit that executes one or more applications, and the message is generated as a result of executing the application.

The communication control unit 102 generates message information for each message, which is information for specifying the priority of the message. The message buffer 103 is a storage unit that stores the generated message. The communication control unit 102 stores the message in the message buffer 103. The message information table 104 is a storage unit for storing message information. The communication control unit 102 stores the message information in the message information table 104.

The communication unit 105 transmits a message and receives a message from another ECU according to the control of the communication control unit 102.

<Processing>
The details of the process according to this embodiment will be described below. FIG. 3 is a flowchart showing the processing of one ECU 11. The processing of the ECU 11 and the processing of the entire communication system 1 will be described with reference to FIG. This process is continuously executed, for example, during the activation of the communication system 1.

(Step S101): The communication control unit 102 synchronizes the time with the other ECUs 12 to 16. The time synchronization can be executed by controlling the communication unit 105 and performing communication using a time synchronization protocol such as gptp or NTP. By this synchronization processing, the ECUs 11 to 16 can suitably control the transmission timing described later.

(Step S102): The message generation unit 101 generates a message to be transmitted to another ECU. Further, the message generation unit 101 generates, for example, a data size of the message, an allowable delay time, a value representing the priority, and the like as information used for determining the transmission priority of the message. Further, the message generation unit 101 outputs, for example, a source or destination MAC address, an IP address, or the like as information necessary for communication.

The communication control unit 102 appropriately adds information and the like necessary for the above-mentioned communication to the message and stores it in the message buffer 103.

(Step S103): The communication control unit 102 generates message information including information used for determining the transmission priority of the above-mentioned message for each message and stores it in the message information table 104. The processes of steps S101 to S103 are also executed in the other ECUs 12 to 16, respectively.

(Step S104): In the communication system 1, the set of the arbitration period and the subsequent communication period is repeated. When a new arbitration period is started, the communication control unit 102 acquires message information with reference to the message information table 104, and controls the communication unit 105 to simultaneously transmit the acquired message information to the other ECUs 12 to 16. do. That is, the message information about the message generated in the Nth arbitration period or the Nth communication period (N = 1, 2, 3, ...) After activation is simultaneously transmitted in the (N + 1) th arbitration period. Similarly, the other ECUs 12 to 16 simultaneously transmit the message information of the own device.

(Step S105): The communication unit 105 sequentially receives message information of each ECU from the other ECUs 12 to 16. The communication control unit 102 stores the received message information in the message information table 104. The other ECUs 12 to 16 also store the received message information in the same manner. The execution order of the process of transmitting message information and the process of receiving message information from any of the other ECUs 12 to 16 in steps S104 and S105 is not limited.

(Step S106): In the next communication period, the communication control unit 102 refers to the message information table 104 and acquires the message information of the ECU 11 which is its own device and the message information of the ECUs 12 to 16 which are other devices. , The transmission timing of the message corresponding to these message information is determined so as not to overlap each other within the next communication period based on the data size included in these, the allowable delay time, the value representing the priority, and the like. That is, within the (N + 1) th arbitration period, the transmission timing of the message corresponding to the generated and acquired message information is determined to be a timing that does not overlap with each other within the (N + 1) th communication period. The other ECUs 12 to 16 also determine the transmission timing of each message in the same manner. In each of the ECUs 11 to 16, the same rule for determining the transmission timing is used. Further, the message information stored in each of the ECUs 11 to 16 is the same in steps S104 and S105 described above. Therefore, the transmission timings determined by the ECUs 11 to 16 are the same. The rule for determining the transmission timing is not limited, and the transmission timing may be determined according to a value indicating the priority, the one with a short allowable delay time may be preferentially determined, and the one with a small size is prioritized. These may be appropriately weighted and determined.

(Step S107): The communication control unit 102 acquires the message whose transmission timing is determined in step S106 from the message buffer 103, controls the communication unit 105, and transmits the acquired message at the determined timing. The other ECUs 12 to 16 also transmit a message at a similarly determined timing. When the communication unit 105 receives a message from the other ECUs 12 to 16, the communication control unit 102 notifies the message generation unit 101 or the like, which is an application execution unit, of the received message. Further, the communication control unit 102 deletes the transmitted message from the message buffer 103, and deletes the message information corresponding to the transmitted or received message from the message information table 104. The other ECUs 12 to 16 also perform the same processing.

After that, the processes of steps S102 to S107 are repeated. Regarding the message generated in the Nth arbitration period or the Nth communication period, the message information is shared with each ECU 11 to 16 in the (N + 1) th arbitration period, and the transmission timing is set in the (N + 1) th communication period. If the determination and transmission are executed, the processes of steps S102 and S103 may be executed in parallel with the processes of steps S104 to S107. The arbitration period and the communication period may be set as periods of predetermined lengths, respectively, or the arbitration period may be switched to the communication period when the steps S104 and S105 are completed, or the communication period may be switched to the arbitration period when the step S107 is completed. You may. If either the arbitration period or the communication period is not predetermined as a period of a predetermined length, the ECUs 11 to 16 notify each other that the period has ended, and the synchronization accuracy of switching the period is determined. You may secure it.

(effect)
As described above, in the communication system 1 according to the present invention, the ECUs 11 to 16 connected to the switching hub 20 determine the transmission timing in advance based on the message to be transmitted, and transmit the message at the determined timing. By shifting the transmission timing so that at least a part of the transmission timing does not overlap, the number of messages to be stored simultaneously by the buffer of the switching hub 20 can be reduced, and the buffer size can be reduced. The length of the communication period, the method of shifting the transmission timing, and the amount of shift are the data size and transmission frequency of the messages of the ECUs 11 to 16, the relay delay of the switching hub 20, the desired reduction amount of the buffer size, and the collision avoidance of the messages. It can be appropriately designed according to the transmission interval and the like. Further, if the number of messages to be transmitted is small and the buffer of the switching hub 20 can store all the messages even if they are transmitted at the same time, it is not necessary to make the transmission timings different.

Here, an example of the effect of the present invention will be described. Each of the ECUs 11 to 16 shall transmit a first message having a size of 1000 bytes, a second message having a size of 500 bytes, and a third message having a size of 100 bytes to each of the other ECUs within a predetermined period. .. In this case, a total (1000 + 500 + 100) × 5 = 8000 bytes of data is transmitted from one ECU 11 to the other five ECUs 12 to 16. One ECU 11 receives a total of 8000 bytes of data from the other five ECUs 12 to 16.

Unlike the present invention, when the ECUs 11 to 16 continuously transmit these data at the same time, the switching hub 20 transmits a total of 8000 bytes of data to be sequentially transmitted to each of the six ports corresponding to the ECUs 11 to 16. A buffer that can be stored is required, and a buffer size of 8000 × 6 = 48000 bytes is required for the entire switching hub 20.

On the other hand, according to the above embodiment of the present invention, the timings at which the ECUs 11 to 16 transmit the first message, the second message, and the third message are different from each other, and correspond to the ECUs 11 to 16 of the switching hub 20. If it is not necessary to store two or more unsent messages at the same time on each of the six ports, each port stores 1000 bytes of data of the first message, which is the maximum size message. It suffices if there is a buffer that can be used, and a buffer size of 1000 × 6 = 6000 bytes is sufficient for the entire switching hub 20. In general, the size of the message information can be made sufficiently smaller than the maximum size of the message, so that the buffer size required for transmitting the message information does not need to be considered separately. As described above, according to the present invention, it is possible to provide a communication system capable of suppressing message loss and reducing costs even if the amount of communication is the same and the buffer size of the switching hub is suppressed as compared with the conventional one. can.

The present invention includes not only a communication system, but also an ECU constituting the communication system, a message transmission method executed by the computer of the ECU, a message transmission program, a computer-readable non-temporary storage medium that stores the message transmission program, and a communication system. It can be regarded as a vehicle or the like. Further, the present invention can be applied to a communication system other than the communication system mounted on the vehicle.

The present invention is useful for communication systems mounted on vehicles and the like.

1 Communication system 11, 12, 13, 14, 15, 16 ECU
20 Switching hub 101 Message generation unit 102 Communication control unit 103 Message buffer 104 Message information table 105 Communication unit

Claims (1)

An in-vehicle communication system including a switching hub and a plurality of ECUs connected to the switching hub and capable of communicating with each other.
Each of the plurality of ECUs
A message generator that generates a message to be sent to any of the other ECUs,
With the communication unit that communicates with other ECUs,
It includes a communication control unit that controls communication with other ECUs by the communication unit and determines a timing at which the message is transmitted.
The communication control unit
Within a predetermined arbitration period, message information that is information for specifying the priority of the message is generated, the message information of the own ECU is transmitted to each of the other ECUs, and each of the other ECUs concerned with the other ECU. Received the above message information of
Based on the message information of the own ECU and other ECUs, the timing of transmitting the message according to the rules common to other ECUs does not overlap with each other at least in a predetermined communication period after the arbitration period. In-vehicle communication system to be determined.

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