JP2859749B2 - Multiplex transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplex transmission apparatus in which a plurality of communication nodes are connected to a multiplex transmission line, and the plurality of communication nodes communicate with each other through the multiplex transmission line.

[0002]

2. Description of the Related Art Recently, in the field of automobiles, the number of electrical components such as switches, sensors, and actuators has increased along with the development of electronics, and thus the wiring harnesses connecting the electrical components have become increasingly large and complicated. Is a problem. Therefore, a multiplex transmission system in which one transmission line is shared by a large number of electrical components has been receiving attention. In particular,
Communication nodes for the various electrical components and communication nodes for anti-lock brake control (ABS), automatic transmission control (EAT), four-wheel steering control (4WS), engine control (EGI), etc. are each connected to a multiplex transmission path. As a result, a time division multiplex transmission network is formed. Each communication node has a communication chip for multiplex transmission and a CPU connected to the multiplex transmission line via the communication chip, and transmits and receives data to and from other communication nodes via the multiplex transmission line.

When a failure such as disconnection or short-circuit occurs in a multiplex transmission line composed of, for example, a twisted pair line, communication between nodes becomes impossible. The failure of the multiplex transmission line itself can be detected by, for example, a circuit disclosed in JP-A-61-224596. on the other hand,
If an abnormal condition occurs in any of the communication nodes and the CPU goes out of control, the function of the communication node is impaired, so that it is necessary to perform some fail-safe processing. Therefore, it is not enough to detect the failure of the multiplex transmission line itself as described above, and it is also necessary to always diagnose whether or not each communication node is abnormal.
Conventionally, important communication nodes, particularly a plurality of communication nodes that perform ABS control, etc., are dealt with by duplicating the CPU of each node so that each of the plurality of communication nodes has a failure diagnosis function. I was

Conventionally, a monitoring node (hereinafter, referred to as a TMS node) called a total managing system (TMS) is connected to a multiplex transmission line, and the operation state of all other communication nodes is monitored by the TMS node. Sometimes it was adopted. It is also conceivable that the TMS node monitors the total traffic volume of the communication on the multiplex transmission line irrespective of the communication node from which the communication data is transmitted.

[0005]

As described above, the conventional multiplex transmission apparatus employs a configuration in which the CPUs of a plurality of communication nodes are duplicated for failure diagnosis. However, there is a problem that the entire multiplex transmission apparatus becomes large. Further, when a TMS node having a function of monitoring the total amount of traffic is separately provided, the system efficiency of the entire multiplex transmission device is deteriorated.

It is an object of the present invention to reduce the cost, reduce the size, and increase the system efficiency of a multiplex transmission apparatus as a whole while realizing fault diagnosis of a plurality of communication nodes and monitoring the traffic volume of communication on a multiplex transmission path. It is in.

[0007]

In order to achieve the above object, a solution of the present invention is to provide a communication node with a CP.
It is noted that when U goes out of control, the traffic volume of the communication node becomes abnormally large, and a single monitoring node monitors the traffic volume of each communication node on the multiplex transmission path to diagnose the failure of each communication node. Is adopted. Specifically, the present invention relates to a plurality of communication nodes respectively connected to a multiplex transmission line and communicating with each other through the multiplex transmission line, and a traffic volume of communication on the multiplex transmission line for each of the plurality of communication nodes. A single monitoring node that monitors each communication node and determines that the communication node is abnormal when the traffic amount of any communication node exceeds the maximum traffic amount preset for each communication node. Is adopted.

[0008]

According to the present invention, the maximum traffic amount is preset for each of a plurality of communication nodes connected to the multiplex transmission line. The monitoring node
It monitors whether the traffic volume of each communication node on the multiplex transmission line exceeds the maximum traffic volume. When there is no abnormality in the communication node, the traffic amount of the communication node does not exceed the maximum traffic amount of the communication node. However, when an abnormality occurs in a certain communication node, the traffic amount of the communication node becomes abnormally large and exceeds the maximum traffic amount. The monitoring node determines that the communication node whose traffic volume exceeds the maximum traffic volume is abnormal.

[0009]

FIG. 1 is a block diagram showing an embodiment of a multiplex transmission apparatus according to the present invention. As shown in FIG. 1, a number of communication nodes such as a node A10 and a node B20 are connected to a multiplex transmission line 1 composed of, for example, a twisted pair line, thereby forming a time-division multiplex transmission network. Each of the communication nodes 10, 20,... Has a communication chip and a CPU, and can transmit / receive data to / from another communication node through the multiplex transmission line 1. The TMS node 30 is further connected to the multiplex transmission line 1. The TMS node 30 similarly has a communication chip and a CPU, and can transmit and receive data to and from the communication nodes 10, 20,. However, the TMS of the present embodiment
The node 30 does not monitor the total traffic volume of the communication on the multiplex transmission path 1 without distinguishing from which communication node the communication data is transmitted as described above. Communication nodes 10, 20, ...
For each of the communication nodes, the traffic volume of the communication on the multiplex transmission path 1 is monitored for each communication node, and when the traffic volume of one of the communication nodes exceeds the maximum traffic volume preset for each communication node, It is determined that there is an abnormality in the node.

FIG. 2 is an explanatory diagram showing the structure of a frame F which is a unit of communication data in the multiplex transmission device. As shown in the figure, one frame F is, for example, SD
(Start Delimiter) code, priority code,
Each field includes a frame ID code, a data length, data 1 to data N, and a check code. A node that intends to execute transmission transmits a frame to which a frame ID code indicating that the node is the transmission source is added. At this time, the fields of data 1 to data N whose length is displayed in the data length field include data relating to a plurality of nodes. Each of the other nodes recognizes the start of the frame by receiving the SD code, knows whether or not the frame is a frame addressed to itself based on the frame ID code, and starts receiving if the frame is addressed to itself. Then, the end of the frame is recognized by receiving the check code. As described above, the communication nodes 10 and 2
, And communication between all nodes including the TMS node 30 is advanced.

Next, the operation of the above multiplex transmission apparatus will be described. Each of the communication nodes 10, 20,... Transmits the frame F at a frequency according to its own operation characteristics. In the case of a car, for example, a communication node that performs EGI control always receives new data from various sensors and sequentially transmits corresponding data. In other words, a transmission frame always exists on the multiplex transmission line 1 for the communication node that controls the EGI control. On the other hand, for example, for a communication node that controls ABS control, the traffic volume of the communication node on the multiplex transmission line 1 increases only when the brake is depressed. As described above, the traffic amount on the multiplex transmission line 1 is constant or changes every moment when viewed from each communication node. However, unless there is an abnormality in the communication node, each communication node 10, 20,. Traffic volume T ₁₀ ,
T _20, ... is the maximum amount of traffic is set in advance with respect to the communication node _T max10, T max20, there can be no exceed .... However, a certain communication node, for example, node A1
If the CPU goes out of control at 0, the traffic amount _T10 of the communication node ₁₀ becomes abnormally large and exceeds the maximum traffic amount _Tmax10 . Therefore, TMS node 3
. 0, each traffic node 10, 20,...
.., And prepares for fail-safe processing.

FIG. 3 is a flowchart showing the operation of the TMS node 30. As shown in the figure, the TMS node 30 first measures the traffic volume of the communication on the multiplex transmission line 1 for each of the communication nodes 10, 20,. As described above, the frame F on the multiplex transmission path 1 is given the frame ID code indicating the transmission source. TM
The S node 30 measures the traffic amount of each communication node while identifying the transmission source of the frame F on the multiplex transmission path 1 based on the frame ID code. Corresponding to this, the maximum traffic volume in consideration of the operation characteristics is preset for each communication node, and the TMS node 30
Remembers this. In step S2, it is checked whether or not the measured traffic amount for each communication node has exceeded the maximum traffic amount (threshold). When there is no abnormality in the communication node, the transmission frame of the communication node does not exceed the maximum traffic volume of the communication node.
However, when an abnormality occurs in a certain communication node, the traffic amount of the communication node becomes abnormally large and exceeds the maximum traffic amount of the communication node. The TMS node 30 determines that there is an abnormality in the communication node in step S3 for the communication node whose traffic amount exceeds the maximum traffic amount, and further gives a system down command to the communication node in step S4. It executes fail-safe processing.

As described above, according to this embodiment, the failure diagnosis of these communication nodes is collectively executed by the TMS node 30 without duplicating the CPUs of the plurality of communication nodes 10, 20,. Therefore, the cost and size of the entire multiplex transmission device can be reduced. Further, the TMS node 30 is connected to each communication node 1
Since both the failure diagnosis function of 0, 20,... And the traffic amount monitoring function are provided, the system efficiency of the entire multiplex transmission apparatus is increased. Since the TMS node 30 measures the traffic volume for each communication node, it is also possible to sequentially calculate the total traffic volume for all communication nodes by summing up the traffic volume, and execute control based on the total traffic volume. It is also possible.

[0014]

As described above, according to the present invention, a configuration is adopted in which a single monitoring node diagnoses a failure of each communication node by monitoring the traffic volume of each communication node on the multiplex transmission line. Unlike the conventional case, the failure diagnosis of each communication node can be realized without having each of the plurality of communication nodes have a failure diagnosis function, and the cost and size of the entire multiplex transmission device can be reduced. it can.
Further, since the monitoring node has both the failure diagnosis function of the communication node and the traffic amount monitoring function, the system efficiency of the entire multiplex transmission device is increased.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment of a multiplex transmission apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a structure of a frame which is a unit of communication data in the multiplex transmission apparatus of FIG.

FIG. 3 is a flowchart illustrating an operation of a TMS node in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Multiple transmission line 10 ... Node A (communication node) 20 ... Node B (communication node) 30 ... TMS node (monitoring node) F ... Frame

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-81145 (JP, A) JP-A-55-138946 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04L 12/28 H04L 12/48

Claims (1)

(57) [Claims] A plurality of communication nodes respectively connected to a multiplex transmission line and communicating with each other through the multiplex transmission line;
The traffic volume of communication on the multiplex transmission path is monitored for each of the plurality of communication nodes for each communication node, and when the traffic volume of any of the communication nodes exceeds the maximum traffic volume preset for each communication node. And a single monitoring node that determines that the communication node has an abnormality.