JP2006319381A - Method for transmitting urgent message - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to transmit a CAN message in an early stage when the CAN message having priority and transmission cycle which are fixed is desired to be urgently transmitted. <P>SOLUTION: A frame 22 for transmitting an urgent message having the shortest transmission cycle having the ID of the highest priority is added for each of nodes 11-16, and a frame 24 for receiving an urgent message capable of receiving only the frame is set in a specific node. When an urgent message is generated, this message is preferentially transmitted by the frame 22 for urgent message onto a CAN bus 17, the transmitted message is received by a frame 24 for urgent message of another node, and the urgent message is retransmitted with the original ID at a transmission cycle shorter than the original transmission cycle. Thus, since the message is transmitted at a cycle shorter than the unchangeable transmission cycle set in the transmission source, the message can be transmitted earlier than in the case where it is transmitted at the original long cycle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an emergency message transmission method, and in particular, priority is given to other messages when an emergency message occurs in a network adopting a CAN (Controller Area Network) communication protocol in an in-vehicle LAN (Local Area Network) system. The present invention relates to an emergency message transmission method for transmitting an emergency message.

  A vehicle uses a plurality of electronic control units (ECUs) composed of computers and sensors having specific control functions, which are connected to each other via a LAN to form a network. (For example, refer to Patent Document 1). In the in-vehicle LAN system, various communication protocols are employed, and the CAN communication protocol is becoming mainstream. Here, a network adopting this CAN communication protocol will be described.

FIG. 5 is a system diagram showing an example of a network based on the CAN communication protocol.
This system has a plurality of nodes 101 to 106 serving as electronic control units, and these nodes 101 to 106 are connected to a CAN bus 107. All the nodes 101 to 106 connected to the CAN bus 107 can frame the message and transmit it. For example, to describe the node 101 as a representative, it is assumed that the node 101 is set to be able to transmit n messages.

  A unique ID (Identifier) is set in advance in a frame for transmitting a message, and a transmission cycle to be sent to the CAN bus 107 is set for each frame. Each message is given a priority, and the priority is determined by the ID. For example, in the illustrated example, the ID of the first frame is “100” in hexadecimal, the ID of the second frame is “200”, the ID of the n−1th frame is “300”, and the ID of the nth frame. Is 400, which means that the first frame having the smallest ID value has the highest priority, and the higher the value, the lower the priority.

Each of the nodes 101 to 106 periodically transmits each message at a period set for each frame. At that time, when the transmission of the message competes with the transmission of the message by another node, the priority is high. The node that sent the message can send the message with priority, and the node that sent the message with the lower priority stops the message sending operation and moves to the receiving operation.
Japanese Patent Laying-Open No. 2004-038388 (FIG. 5)

  Since the ID for each message and the periodic transmission period set in advance at each node are fixed and cannot be changed, the priority order of messages when being sent to the CAN bus cannot be changed. Therefore, an event with a very low probability of occurrence, and a message that has been set to a low priority and a long transmission cycle should be sent urgently in combination with other events that occurred at the same time, for example. If this happens suddenly, or if the data itself has multiple risk levels and the probability of occurrence is very low, it will cause a very serious safety issue. There was a problem that the message could not be transmitted early in preference to other messages.

  The present invention has been made in view of the above points, and it is an object of the present invention to provide an emergency message transmission method capable of transmitting an early message when a message requiring emergency transmission suddenly occurs. And

  In the present invention, in order to solve the above-described problem, an emergency message transmission method which allows an emergency message to be transmitted in a network in which a plurality of nodes are connected to a CAN bus and in which an ID indicating a priority order and a transmission cycle are determined. When the normal message is changed to an emergency message that requires urgent transmission, the data of the normal message is copied to the emergency message transmission frame that is prepared in advance in the own node and has the highest priority and the shortest transmission cycle. The first step of transmitting the emergency message transmission frame to the CAN bus, and when another node that has prepared an emergency message reception frame that can receive only the emergency message transmission frame receives the emergency message, Another node sends the emergency message to the normal message The normal emergency message transmission method characterized in that it comprises a second step, the retransmitting to the CAN bus in a shorter period than the transmission period of the message is provided by ID.

  According to such an emergency message transmission method, in the first step, a normal message is transmitted as an emergency message by an emergency message transmission frame having the highest priority and set in the shortest transmission cycle in the own node, In the step, the emergency message transmission frame is received by a specific other node, and the received emergency message is retransmitted at a cycle shorter than the transmission cycle of the normal message with the original normal message ID. As a result, even a message whose priority order and transmission cycle cannot be changed can be transmitted with a short transmission cycle, so an emergency message requiring sudden emergency transmission is transmitted early. It becomes possible.

  In the emergency message transmission method of the present invention, the transmission cycle that cannot be changed is retransmitted at a transmission cycle shorter than the transmission cycle of the normal message that the other node has changed to the emergency message. There is an advantage that it becomes possible.

  Further, when another node retransmits, it retransmits with the original ID of the normal message, so that the receiving node can receive without performing special processing such as changing the received ID.

  In addition, a message frame that has a very low probability of occurrence but would result in a very serious safety issue will usually have a high priority ID and a short transmission period in accordance with its worst case conditions. However, according to the emergency message transmission method of the present invention, it is possible to set the frame ID and the transmission period under conditions with a higher probability of occurrence, that is, the transmission period can be set longer with low priority. As a result, the bus load can be kept low, and if a message requiring urgent transmission suddenly occurs, it can be transmitted in a short transmission cycle.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a system diagram for explaining an emergency message transmission method according to the present invention.
As a system, it is assumed that a plurality of nodes 11 to 16 serving as electronic control units are connected to a CAN bus 17 to constitute a network.

  Here, among the nodes 11 to 16 connected to the CAN bus 17, there are n messages that are normally set in a node that may transmit an unexpected emergency message, here, for example, the node 11. In addition to the transmission frame 21, an emergency message transmission frame 22 is additionally set. The emergency message transmission frame 22 is set with the ID having the highest priority among the nodes 11 and set with the shortest transmission cycle. Of course, such an emergency message transmission frame 22 is set for each node even in all other nodes in which a normal message to be transmitted can be an emergency message.

  On the other hand, any one of the nodes 11 to 16 connected to the CAN bus 17, here, the node 14 can receive only the emergency message transmission frame 22 in addition to the normal message reception frame 23. The emergency message reception frame 24 set to “1” is additionally set.

  Next, as an example, when a message is transmitted to an arbitrary node on the CAN bus 17 by a frame (1) by a frame (1), the message is changed to a message to be transmitted urgently. An emergency message transmission procedure in the case of an error will be described.

  FIG. 2 is a flowchart showing an operation when an emergency message is transmitted from a specific node, FIG. 3 is a diagram showing a data structure of an emergency message transmission frame, and FIG. 4 is a flowchart showing an emergency message retransmission operation in the specific node. .

  As shown in FIG. 3, the data frame in the CAN communication protocol includes a frame start bit SOF, an arbitration field ID, a control field Control, a data field Data, a cyclic redundancy check field CRC, a response field ACK, and a frame end bit EOF. The ID information indicating the priority is stored in the arbitration field ID, and the data of the message to be transmitted is stored in the data field Data.

  First, in FIG. 2, it is assumed that a situation occurs in which a normal message is desired to be transmitted as an emergency message. As an example of this, for example, when the node of the inter-vehicle distance control ECU measures the inter-vehicle distance and periodically transmits the data to the CAN bus 17 as a normal message, the measurement data is used as the risk level. When the highest risk level is reached, an emergency message may be sent to the brake control ECU node.

  In such a case, the data of the normal message is first copied to the emergency message transmission frame 22 having the highest priority and the shortest transmission cycle (step S1). That is, data in the data field Data of the normal message transmission frame is copied to the data field Data of the emergency message transmission frame 22.

  Next, the ID information in the arbitration field ID of the normal message transmission frame is copied after the previously copied data in the data field Data of the emergency message transmission frame 22 and embedded in the data (step S2). . As a result, the data length changes, so the data length code set in the control field Control is changed (step S3), and the emergency message transmission frame 22 is transmitted on the CAN bus 17 (step S4). That is, when this emergency message is transmitted, the normal message is transmitted as the emergency message with the ID having the highest priority in the shortest cycle.

  The emergency message transmitted in this way is received by the emergency message receiving frame 24 at a specific node (node 14 in the illustrated example). As shown in FIG. 4, the node 14 reads ID information from the data field Data of the received emergency message receiving frame 24, and sets the read ID information as an arbitration field ID (step S11). Next, the ID information is deleted from the data field Data, and the data length code of the control field Control is restored to match it (step S12). Next, based on the ID information set in the arbitration field ID, it is determined whether the message received in the emergency message reception frame 24 is destined only for the own node (step S13). If it is known in advance that it will not be received, the retransmission is stopped, the message is received, and the process is terminated. When it is known in advance that other nodes also receive the urgent message, or when it is not possible to determine whether the message is destined only for the own node, the node 14 transmits the transmission cycle at the node 11. The emergency message is retransmitted on the CAN bus 17 by the emergency transmission frame set shorter than the cycle set in the normal message frame (step S14).

  Thus, when a normal message to be transmitted from the node 11 is transmitted as an emergency message, the normal message is the shortest by the emergency message transmission frame 22 having the highest priority ID in the node 11. It is transmitted in the transmission cycle, and the ID is returned to the original in another specific node, and it is retransmitted from that node in a transmission cycle shorter than the transmission cycle set in the normal message frame. . As a result, even a normal message that can transmit a low-priority message only in a long transmission cycle can be transmitted preferentially and in a short cycle as an emergency message that requires more urgent transmission. In the entire flow, a message to be transmitted from the node 11 with a long transmission cycle is converted into a short cycle and retransmitted from the node 14. Of course, the priority of the message when it is retransmitted will return to the original priority, but it will be retransmitted in a short period, so it will be sufficient compared to the case of transmitting in the original long period. Can be sent early.

  As another embodiment, when an emergency message is transmitted from the node 11, it is possible to try transmission once. In other words, when an urgent message occurs, it is attempted to be transmitted as a normal message although it is an urgent message. Therefore, if the CAN bus 17 is in the bus idle state, it is faster to transmit it as it is, so that it is transmitted as a normal message as it is, and if transmission is awaited, at this stage, as described above, an emergency message You may make it transmit using the trust frame 22. FIG.

It is a system diagram for demonstrating the emergency message transmission method of this invention. It is a flowchart which shows operation | movement when an emergency message is transmitted from a specific node. It is a figure which shows the data structure of an urgent message transmission frame. It is a flowchart which shows the resending operation | movement of the emergency message in a specific node. It is a system diagram which shows an example of the network by a CAN communication protocol.

Explanation of symbols

11 to 16 nodes 17 CAN bus 21 frame 22 frame for emergency message transmission 23 frame 24 frame for emergency message reception

Claims (4)

In an emergency message transmission method in which a plurality of nodes can urgently transmit a message having an ID indicating a priority and a transmission cycle determined in a network connected to a CAN bus.
When the normal message is changed to an emergency message requiring urgent transmission, the data of the normal message is copied in an emergency message transmission frame prepared in advance in the own node and having the highest priority and the shortest transmission cycle, A first step of transmitting the emergency message transmission frame to the CAN bus;
When another node that has prepared an emergency message reception frame that can receive only the emergency message transmission frame receives the emergency message, the other node transmits the emergency message with the ID of the normal message. A second step of retransmitting to the CAN bus with a shorter period;
An emergency message transmission method comprising:   When copying the normal message data in the emergency message transmission frame in the first step, the normal message ID is embedded in the emergency message data and transmitted, and in the second step, the emergency message is transmitted. 2. The other node that has received a transmission frame sets the ID embedded in the data of the emergency message as an ID of a transmission frame that is retransmitted from the other node. Emergency message sending method.   In the first step, when the normal message is changed to the emergency message, the self-node tries to transmit, and when the normal message cannot be transmitted, the emergency message is transmitted by the emergency message transmission frame. The emergency message transmission method according to claim 1, wherein: In the second step, after the other node receives the emergency message transmission frame, the second step determines whether the emergency message is a message addressed only to the own node. 2. The emergency message transmission method according to claim 1, wherein retransmission by message ID is stopped.

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