JP3770053B2 - Method for determining communication return in vehicle network - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication return determination method for a vehicle network.
[0002]
[Prior art]
In recent years, along with the electronic control of various devices such as automobile engines and transmissions, these devices are being equipped with control units (ECUs). Such ECUs are networked so that they can communicate with each other.
[0003]
In this case, one cable is conventionally assigned to one signal, but with such a method, the number of wire harnesses becomes enormous as the amount of data communication between each device increases, Such arrangement is very complicated.
Therefore, a serial bus system called CAN (Controller Area Network) has been proposed as one of automobile networks.
[0004]
The CAN is a system in which a plurality of ECUs are mainly connected by a communication line (CAN bus) to perform data communication with each other, and the standard is defined by ISO (International Organization for Standardization). Further, JE 1939 of SAE (American Automotive Engineering Association) also makes detailed arrangements for applying CAN to automobiles.
Incidentally, the CAN is provided with a function for detecting a communication error. The error detection method will be briefly described. The actual signal on the CAN bus is monitored in the ECU on the data transmission side. The transmission data and the data on the bus are compared, and these data match. If so, it is determined that communication has been performed correctly, and if they do not match, it is determined that a communication error has occurred.
[0005]
[Problems to be solved by the invention]
Next, the processing at the time of determining a communication error will be described. There are mainly two patterns as shown in FIGS. 8A and 8B.
First, the pattern 1 shown in FIG. 8A will be described. CAN communication is performed (step S10). If a communication error is detected at the transmission side ECU at this time, the number of errors is integrated (step S20). ). Then, until the count value of the number of errors reaches 256, the CAN communication is permitted as usual, and when the count value reaches 256, the communication of the ECU on the transmission side is stopped (step S30). Thereafter, the error count value is reset and communication is resumed after a predetermined time (step S40). Note that the communication is temporarily stopped once the number of communication errors has accumulated 256 times because of the CAN protocol.
[0006]
Here, this pattern 1 takes into account a temporary error due to, for example, a poor contact on the bus line. That is, even if the bus line is disconnected due to a contact failure and an error occurs, the contact state may be improved thereafter, and communication is resumed after a predetermined time in anticipation of such a case. If the contact state of the bus line does not return to normal, the communication is stopped after counting 256 communication errors again, and thereafter the same processing is repeated.
[0007]
Next, pattern 2 shown in FIG. 8B will be described. From step S50 to S70, the same processing as pattern 1 from step S10 to S30 is performed, and after the communication is stopped in step S70, it is left as it is. The operation of the ECU in which the error has occurred is forcibly terminated (step S80). In this case, communication is suspended until the vehicle is turned on again (power on).
[0008]
However, such conventional methods have the following problems. That is, in the case of pattern 1, it is possible to determine the return from the abnormal state of the CAN bus to the normal state, but when the CAN bus falls into a contact failure state in which it is repeatedly turned on and off periodically at a certain frequency or more, By repeating the communication stop (step S30) and error reset (step S40) of the ECU, the signal being transmitted is interrupted and the error data on the bus line increases, and communication of the line unrelated to the contact failure is performed. There is a problem of stopping. In this case, it has been confirmed by experiments that communication of all ECUs is stopped.
[0009]
On the other hand, in the case of pattern 2, when the number of communication errors reaches 256 times, the ECU communication is forcibly terminated, so that error data increases on the CAN bus as in pattern 1 above, and other ECUs However, even if the bus line returns to the normal state, such a return cannot be determined until the next key-on. Further, since communication remains stopped even when the bus line returns to a normal state, there is a problem that data important for control cannot be exchanged.
[0010]
By the way, Japanese Utility Model Publication No. 5-20027 discloses a technique in which power supply is interrupted when an error signal is detected, and power supply is resumed after a predetermined time. However, in this technique, since the power is turned on and off when an error signal is detected, there is a problem that communication of other ECUs that can normally transmit and receive is also stopped. Moreover, although techniques related to LAN are disclosed in Japanese Utility Model Laid-Open No. 5-74040 and Japanese Patent Laid-Open No. 1-129549, the above-mentioned problems are not solved at all. Note that SAE has no special provision regarding processing after communication error occurs and communication is stopped.
[0011]
The present invention was devised in view of such a problem, and is capable of performing a return determination without affecting other normal systems in the event of a temporary abnormality of a bus line, and is used for vehicle network communication. An object is to provide a return determination method.
[0012]
[Means for Solving the Problems]
Therefore, in the vehicle network communication return determination method according to the first aspect of the present invention, a plurality of control units are connected to each other through a communication line so that they can communicate with each other, and a communication error is detected in any control unit. Then, the number of errors is accumulated (first step), and when the number of errors reaches a predetermined number, it is determined that the system is in an abnormal state and communication of the control unit is temporarily stopped (first step). Step 2).
[0013]
Thereafter, the communication of the control unit is attempted after a predetermined time has elapsed since the communication was stopped (third step), and it is determined whether or not an error has occurred during the communication (fourth step). If it is determined that no communication error has occurred, normal communication is resumed assuming that the system has returned to normal.
In the vehicle network communication return determination method according to the second aspect of the present invention, when it is determined in the fourth step that a communication error has occurred, a third step is performed every predetermined time until no communication error is detected. Communication takes place.
[0014]
Moreover, in the communication return determination method for the vehicle network according to the third aspect of the present invention, the predetermined time is individually set in each control unit according to the importance of control, and in the control unit having high importance, The predetermined time is set short.
Note that, when it is determined in the second step that the number of errors has reached a predetermined number, it is preferable to reset the integrated value of the number of errors. With this configuration, when the system returns to normal, communication is resumed from the number of errors 0.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a communication return determination method for a vehicle network according to an embodiment of the present invention will be described with reference to the drawings.
First, the outline of the CAN specification and the contents defined in SAE J1939 will be described. FIG. 1 is a diagram showing an example of the entire configuration of a network, and a plurality of ECUs 1a to 1d are connected by a bus line 10. Yes. Here, for example, 1a is an engine control ECU, 1b is an automatic transmission (AT) control ECU, 1c is an ABS control ECU, and 1d is a TRC (traction control) control ECU.
[0016]
Communication data is transmitted and received in a communication frame (data frame) as shown in FIG. As shown in the figure, the data frame includes an arbitration field, a control field, a data field, and the like, and will be described below in order.
1. A description of each component of the data frame.
(1) SOF (Start Of Frame)
This is an identifier indicating the start of a frame, and is always “0”.
(2) identifier
This is an ID of the standard format, and details will be described in the section “2.1. Arbitration field” described later.
(3) SRR (Substitute Remote Request)
It is a bit for selecting either the standard frame format or the extended frame format in combination with the IDE of (4) described later.
(4) IDE (Identifier Extension bit)
This bit indicates that the extended frame format is used. When the SRR bit is “1” and the IDE bit is “1”, the extended frame format is not present. When the SRR bit is not present and the IDE bit is “0”, the standard frame is used. Indicates that the format is selected.
(5) identifier ext.
This is an ID indicating that the standard frame format is extended. Details will be described later in “2.1. Arbitration field”.
(6) RTR (Remote Transmission Request)
This bit indicates a request for remote transmission. Remote transmission refers to requesting data transmission to a certain system. When this RTR bit is “0”, normal transmission (when transmitting a data frame), and when “1”, remote transmission (remote frame transmission). Time).
(7) R1, R0
These bits are reserved for future data length expansion (reserved bits) and are currently all “0”. The data length is scheduled to be extended in combination with (8) DLC bits described later.
(8) DLC (Data Length Code)
This is data in the data field, and is a bit for setting the byte length.
(9) Data Field
It is a data field for storing transmission data. SAE J1939 recommends 8-byte data.
(10) CRC (Cyclic Redundancy Check)
This is a field for storing a check code for transmission data errors.
(11) CRC delimiter
CRC delimiter, always “1”.
(12) ACK (Acknowledgement)
This is a field for normal reception confirmation, and the transmission side stores “11”. The receiving side stores “01” if the data check result in the CRC field is normal, and “11” if there is an abnormality.
(13) EOF (End Of Frame)
This is a field (7 bits) indicating the end of transmission, and is always “1111111”.
[0017]
2. Description of PDU (Protocol Data Unit).
Next, the PDU in FIG. 2 will be described. The PDU is main information in the data frame, and (2) identifier, (5) identifier ext. And (9) Consists of Data Fields. Also, a PGN (Parameter Group Number) is determined from this data. Here, PGN is a number for identifying data, and R (reserved), DP (data page), PF (PDU format), etc. in the arbitration field (for details, see 2.1. Explanation of arbitration field below) (Data length 3 bytes).
[0018]
2.1. Arbitration field The arbitration field includes a 29-bit ID and a 3-bit control bit. FIG. 3 shows an outline of the arbitration field. Hereinafter, each part of the arbitration field will be described.
(1) Priority level is used to determine the priority level of messages. “000” has the highest priority level and “111” has the lowest priority level.
(2) Bit reserved by the spare SAE for future function expansion. Since it is not currently used, it is set to “0”.
(3) There are two data page PDU pages, which are used as selectors for the page. Used from page 0.
(4) PDU format (PF)
It is a parameter that determines the content of PDU Specific [see (7)], and is one field that constitutes PGN.
(5) SRR
Refer to item (3) in “1. Explanation of each component of data frame”.
(6) IDE
Refer to item (4) in “1. Explanation of each component of data frame”.
(7) PDU Specific (PS)
Depending on the value of PF, PS is either the destination address (DA) or the group expansion (GE).
(8) Source address The source address of the message is described. The address of each system is defined by SAE J1939.
[0019]
2.2. As shown in FIG. 4, the control field control field is composed of reserved bits (2 bits) and DLC (4 bits).
2.3. Data field A field for storing transmission data. SAE J1939 recommends a fixed data length of 8 bytes.
[0020]
Next, communication error determination in the ECUs 1a to 1d will be described. Each of the ECUs 1a to 1d is provided with a data input / output unit (CAN I / O) 2 as shown in FIG. The data input / output unit 2 includes a data transmission circuit 3, an abnormality detection circuit 4, a data transmission circuit 5, and the like, and is connected to the CPU 6.
[0021]
The transmission data from the CPU 6 is transmitted to another ECU via the data transmission circuit 3, and the bit “11” of the ACK field at this time is taken into the bus abnormality detection circuit 4.
When data is transmitted, the data transmitted from the partner ECU is returned. At this time, the occurrence of an error is determined by the presence or absence of an affirmative response. In other words, as described above, the receiving ECU returns the ACK field bit as “01” if the received data is normal, and “11” if the received data is abnormal. The abnormality detection circuit 4 can determine whether or not a communication error has occurred by monitoring these ACK bits.
[0022]
As shown in FIG. 5, in CAN, data is exchanged with two signals of H and L. In H and L, for example, as shown in FIGS. 7A and 7B, the data is a symmetric signal with opposite signs, and the difference between these signals (CAN H−CAN L) is It is input to the CPU 6. As a result, as shown in FIG. 7B, even if noise enters the signal, the noise is canceled out.
[0023]
In the vehicle network communication return determination method according to the present invention, the process when an error occurs is executed according to the flowchart shown in FIG. Such processing is executed for each of the ECUs 1a to 1d, and will be described below with attention paid to any ECU.
First, CAN communication is executed in step S1, and when a communication error is detected, the number of communication errors (CAN bus error) detected is counted in step S2 (first step).
[0024]
Then, until the communication error reaches the predetermined number of times (256 times), the communication returns to step S1 as in the conventional case, and the communication is continued. When the communication error count value becomes 256, the process proceeds to step S3, and the communication of the ECU is temporarily performed. Is canceled (second step).
Thereafter, the number of errors is reset in step S4, and in step S5, CAN communication is executed only once after a predetermined time (for example, 100 ms) has elapsed (third step). In step S6, it is determined whether or not a communication error has been detected during this communication (in this case, one error detection) (fourth step). Returning to step S4, the error mode processing (error reset, communication restart after a predetermined time, and error determination) of steps S4 to S6 is repeated thereafter. That is, in this case, the CAN communication is tried every predetermined time until the communication is normally performed.
[0025]
On the other hand, if no error is detected in step S6, it returns to step S1 assuming that the abnormal state of the communication system has returned to the normal state, and normal communication is resumed.
In addition, you may set said predetermined time to a different value in each ECU according to the importance of control. For example, in a system (systems related to engine, AT, brake control, etc.) that will hinder vehicle travel unless it recovers from an abnormal state early, the predetermined time is set to 100 ms, and the recovery from the abnormal state is somewhat delayed. However, in a system having little influence on traveling (system such as traction control and auxiliary brake), it is conceivable to set it to about 500 ms. Further, in a system that does not have a problem in traveling even if an error remains (for example, a system related to auto cruise), the predetermined time may be set to ∞ and the return determination may not be performed until the next key-on (power-on). And by setting in this way, when a plurality of ECUs simultaneously cause an error due to poor contact or the like, the ECU that is important for control can be restored with priority.
[0026]
As described above, according to the communication return determination method for the vehicle network according to the embodiment of the present invention, in the event of a temporary abnormality such as poor contact of the CAN bus, the system can be operated without affecting other normal ECUs. There is an advantage that the return to the normal state can be determined.
If a communication error is detected during the communication in step S6, the error mode process (steps S4 to S6) is repeated every predetermined time until normal communication is performed, so that the normal state of the system There is an advantage that it is possible to reliably determine the return to.
[0027]
Further, when the communication error count value reaches the predetermined value (256) in step S2, the error count integrated value is reset in step S4. Therefore, the error count becomes 0 when the system returns to normal, and the next communication error occurs. There is an advantage that it can be prepared.
The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above description, an example in which the network is constructed as a control area network (CAN) has been shown. However, in addition to this, a network in which a plurality of ECUs are connected by communication lines (bus lines) to perform data communication with each other. Can be widely applied to.
[0028]
【The invention's effect】
As described in detail above, according to the vehicle network communication return determination method of the present invention according to claim 1, the control is performed after a predetermined time has elapsed since a communication error was detected in any control unit and communication was stopped. When communication of the unit is attempted and it is determined that no communication error has occurred during this communication, normal communication is resumed assuming that the system has returned to normal. There is an advantage that the return of the system to the normal state can be determined without affecting the normal control unit.
[0029]
According to the vehicle network communication return determination method of the present invention according to claim 2, if a communication error occurs when communication of the control unit is attempted after a predetermined time has elapsed since communication was stopped, a communication error occurs. In addition to the advantage of claim 1, there is an advantage that the restoration of the system can be reliably determined.
[0030]
According to the vehicle network communication return determination method of the present invention according to claim 3, the predetermined time is individually set by each control unit in accordance with the importance of control, so that a plurality of contact failures may occur. When an error occurs simultaneously in the control unit, there is an advantage that the control unit important for control can be restored with priority.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a system to which a vehicle network communication return determination method according to an embodiment of the present invention is applied.
FIG. 2 is a diagram for explaining a data format of a system to which a vehicle network communication return determination method according to an embodiment of the present invention is applied.
FIG. 3 is a diagram for explaining a data format of a system to which a communication return determination method for a vehicle network according to an embodiment of the present invention is applied.
FIG. 4 is a diagram for explaining a data format of a system to which a vehicle network communication return determination method according to an embodiment of the present invention is applied.
FIG. 5 is a schematic diagram illustrating a configuration of a main part of a control unit to which a vehicle network communication return determination method according to an embodiment of the present invention is applied.
FIG. 6 is a flowchart for explaining a main part of a communication return determination method for a vehicle network according to an embodiment of the present invention.
FIG. 7 is a diagram for explaining a data transmission / reception method of a system to which a communication return determination method for a vehicle network according to an embodiment of the present invention is applied.
FIGS. 8A and 8B are flowcharts for explaining a communication return determination method devised in the inventive process of the present invention.
[Explanation of symbols]
1a to 1d ECU (control unit)
2 Data input / output unit (CAN I / O)
3 Data transmission circuit 4 Abnormality detection circuit 5 Data transmission circuit 6 CPU

Claims (3)

A method for determining the return of communication in a vehicle network constructed such that a plurality of control units can communicate with each other.
When a communication error is detected for any control unit, a first step of accumulating the number of errors,
When the number of errors reaches a predetermined number, a second step of determining an abnormal state and temporarily stopping communication of the arbitrary control unit;
A third step of attempting communication of the arbitrary control unit after a predetermined time has elapsed since the communication was stopped;
And a fourth step for determining whether or not an error has occurred in the communication in the third step,
When it is determined in the fourth step that a communication error has not occurred, normal communication is resumed assuming that the system has returned to normal. 2. The vehicle according to claim 1, wherein if it is determined that a communication error has occurred in the fourth step, communication is attempted every predetermined time in the third step until the communication error is no longer detected. Network communication return judgment method. 3. The method for determining communication return in a vehicle network according to claim 1, wherein the predetermined time is individually set in each control unit in accordance with the importance of control.

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