JP2003333048A - Mounted vehicle communication control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the collision of data to efficiently execute transmission/ reception of data. <P>SOLUTION: After setting the state to a state capable of receiving all messages from other ECUs, whether a reception from the other ECU exists is decided, and if there is reception, the time of its reception interrupt (reception time Tr1) is stored (steps 101-103). Message transmission at own sending timing is executed, and its sending time Ts is stored (steps 104, 105). Thereafter, whether there is a reception from the other ECU exists is again decided, and if the reception exists, the time of its reception interrupt (reception time Tr2) is stored (steps 106, 107). Finally, the next transmission timing is delayed by ((Tr2-Tr1)/2-Ts (step 108). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle-mounted communication control system in which a large number of control units (ECUs) are communicably connected to each other on a network.

[0002]

2. Description of the Related Art Conventionally, an in-vehicle communication control system in which a large number of ECUs are communicably connected to a network such as an in-vehicle LAN has been put into practical use, and a large number of data (messages) are sequentially sent from each ECU on the LAN. To be done. In such a system, it is necessary to reduce the frequency of data collision on the LAN and reduce the time delay of transmission data (the delay from the generation of a transmission request until the data is actually transmitted on the LAN). As an example of such measures, there is one in which an index is set in advance such that the bus load (time role of data existing on the LAN) of the entire LAN is set to, for example, 30% or less. In this case, by determining the type of transmission data and the transmission cycle of each ECU so that it can be protected,
It was possible to avoid excessive collision of transmitted data.

[0003]

The above-mentioned prior art is effective in reducing the probability of collision of transmission data in the entire system, but when looking at each data individually, various factors such as communication clock error, etc. Could cause data collisions. That is, when a certain data is transmitted, the time until it is actually transmitted depends on the state of the bus at that time. Therefore, if adverse conditions overlap, the delay time may increase, and if the degree of the delay cannot be predicted, data collision will occur as described above. When data collision occurs, inconvenience such as waiting for data transmission occurs.

The present invention has been made in view of the above problems, and an object thereof is to provide an in-vehicle communication control system capable of suppressing data collision and efficiently executing data transmission / reception. Is to provide.

[0005]

In a vehicle-mounted communication control system according to a first aspect of the present invention, a plurality of control devices are communicably connected to each other on a network, and each control device sends data at a predetermined cycle. Further, the control device monitors the data received from other control devices before and after the data transmission by itself, and the timing of the next data transmission so that the timing of the data transmission and the timing of the data reception before and after the data transmission are equal to each other. Adjust. In this case, the data transmitted from each control device on the network are dispersed at equal time intervals. Therefore, data collision can be suppressed and data transmission / reception can be efficiently performed.

According to the second aspect of the invention, when the data received from the other control device before and after the data transmission is found,
After that, the reception is monitored only for the identified reception data. Basically, the order of data transmission in each control device is fixed, and when transmitting certain data, the data received from other control devices before and after the certain data are the same every time. Therefore, it is only necessary to monitor the reception of the specific data, and the processing can be simplified.

As described in claim 3, it is convenient that the transmission cycle of all data in each control device is the same cycle. That is, if all the control devices have the same transmission cycle, the communication load becomes almost uniform in any case by distributing the data as described above.

According to the invention described in claim 4, each control device transmits a plurality of data having different transmission cycles, and the transmission cycles are set to be an integral multiple of the shortest cycle. When the control device transmits the data of the shortest period, the control device also transmits the data of another period which is synchronized with the data of the shortest period, and further monitors the transmission and reception of the data of the shortest period as well as the next time when the data is transmitted. Adjust the data transmission timing of. In this case, the time interval between the data having the shortest period is properly maintained. Further, even if there are data with different transmission cycles, collision can be suppressed.

As a concrete timing adjusting method, as described in claim 5, the time of data reception before and after the data transmission is stored each time, and the next data is transmitted at a timing of 1/2 of the difference between the times. Adjust the transmission timing.

It is also possible that the timing of data transmission and the timing of data reception before and after that are specified in advance. In such a case, as described in claim 6, instead of adjusting the timings evenly (matters of claim 1), the timing of the next data transmission may be adjusted to be as specified in advance. good.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an in-vehicle communication control system. In-vehicle LAN wired in the vehicle in FIG.
A large number of control devices, that is, ECU 1, ECU 2, ECU 3, ... Are connected to the (network) bus 10, and the respective ECUs can communicate with each other. Each ECU transmits a message (data) to another ECU at a predetermined time cycle. Particularly in this embodiment, each E
The transmission cycle of all messages by the CU is the same cycle.

Here, the order of message transmission in each ECU is fixed, and when transmitting a message,
The messages received from other ECUs before and after that should be the same every time. However, there is a possibility that the time interval will gradually change due to an error or the like in the communication clock of each other, and in some cases, messages may collide on the bus 10. Therefore, the procedure for adjusting the transmission timing will be described below.

FIG. 2 is a time chart showing how messages are transmitted and received by a certain ECU (eg ECU 1). In the figure, (a) shows the message transmission and reception of this time,
(B) shows the next message transmission / reception.

As shown in FIG. 2A, a message Y of the ECU 2, a message X of the ECU 1, and a message Z of the ECU 3 are sent on the bus 10 in the order shown. From the ECU 1, the message Y is received at the time T1, the message X is transmitted at the time T2, and the message Z is further received at the time T3. In this case, the message X is transmitted and the messages Y and Z before and after the message X are transmitted.
, And the time intervals between the reception of A and B are A and B, respectively, and A and B are not uniform.

When the transmission and reception of the message is not uniform in time as described above, the ECU for transmitting the message adjusts its own transmission timing. Specifically, the shift of the transmission timing of the message X between the reception timings of the messages Y and Z is calculated based on the above A and B. Then, as shown in FIG. 2B, at the next message transmission, the transmission timing of the message X is changed so as to eliminate the time difference between A and B. Actually, the message X is transmitted at the time Ta. The time Ta is a time when the elapsed time from the time when the message Y is received is used as a reference and is delayed from the time T2 in (a) of FIG.

To change the transmission timing of the message X, the interruption time of the transmission timer may be changed. As a result, the transmission of the message X and the reception of the messages Y and Z before and after the message X are performed uniformly. By the way, in order to realize easily, 1 / of the above A and B
Although it is sufficient to send the message X at 2, in this case, the sending time of the message X is not actually equal. Therefore, it is desirable to transmit the message X at a timing earlier than the timing of (A + B) / 2 by the transmission time of the message X.

FIG. 3 is a flow chart showing the process of adjusting the transmission timing. The process of FIG. 3 is performed by each of the ECUs 1 to 3 and the like, and the ECUs monitor messages. For example, if the ECU 1 executes the processing of FIG.
CU2, 3 etc. correspond to other ECUs.

First, at step 101, all messages from other ECUs are set to be receivable. Then, in step 102, it is determined whether or not there is a reception from another ECU,
If there is reception, the time at which the reception interrupt occurs (reception time Tr1) is stored in step 103. Further, in step 104, it is determined whether or not it is the transmission timing of itself, and if it is not the transmission timing, the process returns to step 102 (step 103 is performed again if necessary).

At the transmission timing, the process proceeds to step 105, the message is transmitted, and the transmission time Ts is stored. Then, in step 106, the presence / absence of reception from another ECU is determined again, and if reception is present, the time at which the reception interrupt has occurred (reception time Tr2) is stored in step 107.

Finally, in step 108, the next transmission timing is delayed by "((Tr2-Tr1) / 2) -Ts". The reception time Tr1 is the time T1 in FIG.
In addition, the reception time Tr2 corresponds to the time T2 in FIG.

If a message received from another ECU (a message received in steps 102 and 106) is identified before and after the message is transmitted, the reception may be monitored thereafter only for the identified received message. . Basically, the order of message transmission in each ECU is fixed, and when a certain message is transmitted, the messages received from other ECUs before and after that message are the same every time.
Therefore, it suffices to monitor the reception of the specific message, and the processing can be simplified.

According to the present embodiment described in detail above, the LA
The messages sent from each ECU on N will be distributed at equal time intervals. Therefore, it is possible to suppress message collision and efficiently perform message transmission / reception. In this case, the waiting time from the transmission request to the actual message transmission is reduced, and the transmission delay can be eliminated.

(Second Embodiment) Next, a second embodiment of the present invention will be described focusing on the differences from the above-described first embodiment. In the above embodiment,
Although all messages are monitored with a single message transmission cycle, in the present embodiment, a large number of messages with different transmission cycles are provided for each ECU, and only the message with the shortest cycle among them is monitored.

FIG. 4 is a time chart showing an example of setting the transmission cycle of each message. The message transmission cycle is set in four ways, M1, M2, M3 and M4.
4ms period, 8ms period, 16ms period, 32ms period
It is a cycle. In this case, all transmission cycles are set to be an integral multiple of the shortest transmission cycle (4 ms), and in each case, each message is transmitted in accordance with the shortest transmission cycle.

Further, when a plurality of transmission cycles are set in this way, the message transmission timing is decentralized with the shortest transmission cycle as a reference in order to average the bus load. Therefore, at the time of transmission of the message M1 having a period of 4 ms (T0, T4, T8, ...), messages of one or two periods are transmitted. Note that the process is repeated after time Tx. The shortest transmission cycle is unified for all ECUs, and each ECU knows in advance the type (data content) of the message of the shortest cycle transmitted by another ECU.

FIG. 5 is a time chart showing how messages are transmitted and received by a certain ECU (eg ECU 1). In the figure, (a) shows the message transmission and reception of this time,
(B) shows the next message transmission / reception.

As shown in FIG. 5A, a message group β of the ECU 2, a message group α of the ECU 1, and a message group γ of the ECU 3 are sent on the bus 10 in the order shown. The message group α is, for example, the messages x1, x
2, x3, x4, of which at least message x1 (first message) is a message of 4 ms period. Following the 4 ms period message, another period message is transmitted. The same applies to other message groups β and γ (at least messages y1 and z1 are 4 ms.
It is a periodic message).

In the present embodiment, only the message with the shortest cycle (further, the earliest among them) is the monitoring target.
From U1, the message y1 is received at time T11, the message x1 is transmitted at time T12, and the message z1 is further received at time T13. In this case, the message x1 is sent and the messages y before and after it are sent.
The time intervals between the reception of 1 and z1 are A and B, respectively,
Adjust the time difference between A and B.

Specifically, the shift of the transmission timing of the message x1 between the reception timings of the messages y1 and z1 is calculated based on the above A and B. Then, as shown in FIG. 5B, at the next message transmission, the transmission timing of the message x1 is changed so as to eliminate the time difference between A and B. Actually, the message x1 is transmitted at time Ta. The method of adjusting the transmission timing is as described above. As a result, transmission and reception of each message group can be performed evenly.

FIG. 6 is a flow chart showing the processing for adjusting the transmission timing. The process of FIG. 6 is performed by each of the ECUs 1 to 3 and the like, and the ECUs monitor messages. For example, if the ECU 1 executes the processing of FIG.
CU2, 3 etc. correspond to other ECUs.

First, at step 201, all shortest cycle messages from other ECUs are set to be receivable. Thereafter, in step 202, it is determined whether or not the shortest cycle message is received from another ECU, and if it is received, the time at which the reception interrupt occurs (reception time Tr1) is stored in step 203. In step 204, it is determined whether or not it is the transmission timing of its own shortest cycle message, and if it is not the transmission timing, the process returns to step 202.

At the transmission timing, the routine proceeds to step 205, where the shortest cycle message is transmitted and the transmission time Ts is stored. In the following step 206, a message having another transmission cycle to be transmitted together with the shortest cycle message is transmitted at the current transmission timing (similarly, if there is another shortest cycle message). Then step 2
In 07, it is again determined whether or not the shortest cycle message is received from the other ECU, and if it is received, the time at which the reception interrupt occurs (reception time Tr2) is stored in step 208. Finally, in step 209, the transmission timing of the next shortest cycle message is set to “((Tr2-Tr1)
/ 2) -Ts ".

As described above, according to the present embodiment, the time interval between the messages having the shortest cycle is properly maintained. Therefore, similar to the first embodiment, it is possible to suppress message collision and efficiently perform message transmission / reception. In this case, in particular, collisions can be suppressed even when there are messages with different transmission cycles.

There may be a case where the timing of data transmission and the timing of data reception before and after that are defined in advance. Specifically, when the amount of data for transmission temporarily increases (for example, when data transmission of multiple cycles overlaps at one time), the time from the reception of the previous data to the reception of the latter data is longer. It may be good to lengthen. In such a case, instead of adjusting them evenly, it is advisable to adjust the timing of the next data transmission so as to be as specified in advance.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an outline of a vehicle control system according to an embodiment of the invention.

2A and 2B are time charts showing how messages are transmitted and received.

FIG. 3 is a flowchart showing a transmission timing adjustment process.

FIG. 4 is a time chart showing a setting example of a message transmission cycle.

5A and 5B are time charts showing how messages are transmitted and received.

FIG. 6 is a flowchart showing a transmission timing adjustment process.

[Explanation of symbols]

1-3 ... ECU, 10 ... bus.

Claims (6)

[Claims] 1. An in-vehicle communication control system in which a plurality of control devices are communicably connected to each other on a network, and each control device sends data at a predetermined cycle. An in-vehicle communication control system, which monitors data received from another control device and adjusts the timing of the next data transmission so that the timing of data transmission and the timing of data reception before and after the data transmission are equal. 2. The in-vehicle communication control system according to claim 1, wherein when data received from another control device before and after data transmission is found, reception is monitored only for the found received data. 3. The vehicle-mounted communication control system according to claim 1, wherein the transmission cycle of all data in each control device is the same. 4. An in-vehicle communication control system, wherein each control device transmits a plurality of data having different transmission cycles, and the transmission periods are set to be an integral multiple of the shortest period, wherein the control device. Is, when sending the data of the shortest cycle, also send the data of other cycles that are synchronized with it,
3. The vehicle-mounted communication control system according to claim 1, further comprising monitoring the transmission / reception of the data of the shortest cycle and adjusting the timing of the next data transmission when the data is transmitted. 5. The data reception time before and after the data transmission is stored each time, and the timing of the next data transmission is adjusted at a timing of 1/2 of the difference between the times. In-vehicle communication control system. 6. When the timing of data transmission and the timing of data reception before and after that are defined in advance, instead of adjusting the timings evenly, the next The vehicle-mounted communication control system according to claim 1, wherein the timing of data transmission is adjusted.