JP2857655B2 - Vehicle data transmission system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle data transmission system comprising a plurality of electronic control units mounted on a vehicle such as an automobile and a common communication line interconnecting the electronic control units.

[0002]

2. Description of the Related Art When a plurality of electronic control units (hereinafter, referred to as "ECUs") are connected by a common communication line (hereinafter, referred to as a "network bus") and data are mutually transmitted, each of the ECs is required.
The transmission right is circulated between U in a predetermined order, and the transmission right is obtained.
A method (token passing method) that allows only a CU to send data to a network bus has been conventionally known.

In such a token-passing type data transmission system, in consideration of the fact that if transmission fails, it is highly likely that retransmission will immediately fail again, the transmission right goes around once and the next transmission right A retransmission is performed when a message is obtained (Japanese Patent Publication No. 1-578).
No. 56, hereinafter referred to as "first prior art").

[0004] Further, a data transmission apparatus has been proposed in which retransmission is performed a predetermined number of times when transmission fails, and the predetermined number of times can be changed by another control device (Japanese Patent Application Laid-Open No. Sho 62-159939). (Hereinafter referred to as "second conventional technology").

[0005]

According to the first prior art, even if retransmission is performed immediately and transmission is successful (for example, a failure due to noise during transmission), retransmission is not performed. Since this is a round of rights, there is still room for improvement to complete the transmission promptly.

According to the second prior art, a predetermined number of retransmissions set by another control device are immediately performed, but the control device itself does not set the number of retransmissions. It was difficult to respond quickly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to appropriately perform retransmission when transmission fails and to improve the data transmission efficiency of the entire system by balancing with the smooth circulation of transmission rights. It is an object of the present invention to provide a vehicular data transmission system capable of performing the following.

[0008]

According to the present invention, a plurality of control devices mounted on a vehicle are connected by a network bus, and a transmission right is circulated among the plurality of control devices. In the vehicle data transmission system for transmitting a message, the plurality of control devices respectively specify transmission / reception means for transmitting / receiving data, transmission failure detection means for detecting data transmission failure, and a type of the transmission failure. Specifying means, wherein the transmitting / receiving means includes
Acknowledgment from receiver for failed transmission
Or if a transmission error is detected
The number of retransmissions of the data is set accordingly, and retransmission is performed only the number of times not exceeding the number of retransmissions.

Preferably, the transmitting / receiving means transfers the transmission right to another control device when the number of transmission failures exceeds the number of retransmissions.

[0010]

Preferably, the number of retransmissions is set to be larger when a transmission error is detected than when no acknowledgment is received from the receiving side.

[0012]

When the data transmission fails, the type of the transmission failure is specified, and the specified type of the failure is acknowledged by the receiving side.
If a fixed response could not be obtained or a transmission error was detected
The number of data retransmissions is set depending on whether the retransmission has been performed, and retransmission is performed a number of times not exceeding the number of retransmissions.

When the number of transmission failures exceeds the number of retransmissions, the transmission right is transferred to another control device.

[0014]

The number of retransmissions is set to be greater when a transmission error is detected than when no acknowledgment is obtained from the receiving side.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of a vehicular control system according to one embodiment of the present invention.
1 to 5 are mutually connected via a network bus 6. The ENG control ECU 1 controls the operation of the engine according to the accelerator pedal operation of the driver of the vehicle. The MISS control ECU 2 controls the automatic transmission according to the driving state of the vehicle. The TCS control ECU 3 controls the automatic transmission. An ECU that detects the slip state of the driving wheels of the vehicle and controls the output torque of the engine, and a suspension control ECU 4 controls the suspension (active suspension) according to the driving state of the vehicle.
U, the brake control ECU 5 is an ECU that detects the locked state of the wheels and performs brake control. These ECUs 1
5 to 5 need to mutually monitor control parameters and operating parameters detected by sensors, and are connected via a network bus 6 to mutually transmit and receive necessary data.

FIG. 2 is a block diagram showing the configuration of the ENG control ECU 1. A central processing unit (hereinafter referred to as "CPU") 101 includes a plurality of sensors 11 and actuators 12 such as fuel injection valves via an input / output interface 104.
It is connected to the. The CPU 101 has a bus line 107
(Random Access Memory) 102 via the
M (Read Only Memory) 103 and a communication control IC (Inte
grated Circuit) 105. Communication control I
C105 is connected to the network bus 6 via the bus interface 106.

The CPU 101 determines a control parameter based on the detection value of the sensor 11 according to a program stored in the ROM 103, and drives the actuator 12. The RAM 102 is used for, for example, temporarily storing data being calculated. The communication control IC controls transmission of a message to the network bus and reception of a message from the network bus.

FIG. 3 is a diagram showing a specific configuration of the bus interface 106 and the network bus 6. The network bus 6 includes twisted pair wires 6b and 6c terminated by a terminating resistor 6a.

The first transmission terminal of the communication control IC 105 is connected to the base of the transistor 119 via the resistor 115. The emitter of the transistor 119 is connected to the power line V
SUP, and the collector is connected via the resistor 116 to the inverting input of the comparator 111 and one of the twisted pair lines 6.
b.

The second transmission terminal of the communication control IC 105 is connected to the base of the transistor 120 via the resistor 117. The emitter of the transistor 120 is connected to the ground, and the collector is connected via a resistor 118 to the comparator 11.
One non-inverting input and the other twisted pair line 6c.

The non-inverting input of the comparator 111 is a resistor 1
The power supply line VSUP is connected to the power supply line VSUP via the reference numeral 12 and also connected to the inverting input of the comparator 111 via the resistor 113. The inverting input of the comparator 111 is connected to ground via a resistor 114, and the comparator 1
The output of 11 is connected to the receiving terminal of the communication control IC 105.

In the circuit of FIG. 3, resistors 116 and 11
8 is about 30Ω, resistors 112 and 114 are about 2 kΩ,
The resistance 113 is about 200Ω, and the termination resistance 6a is about 100Ω.

Pulse signals having phases opposite to each other are output to the first and second transmission terminals of the communication control IC. The first transmission terminal is at a low level (low) and the second transmission terminal is at a high level (high). At this time, both the transistors 119 and 120 are turned on, one twisted pair line 6b is high, and the other twisted pair line 6c is low. When the first transmission terminal is high and the second transmission terminal is low, the transistors 119 and 120 are both turned off, and one twisted pair line 6b is low and the other twisted pair line 6c is high. In this way, a signal is transmitted on the network bus 6.

In response to the high / low state of one twisted pair line 6b, the output of the comparator 111 changes to low / high, and the signal on the network bus 6 is received.

The ECUs 2 to 5 are basically configured similarly to the ECU 1. Therefore, when one ECU sends out a signal in which one twisted pair line 6b goes low (6c goes high), and another ECU sends out a signal going high, the signal on the twisted pair line 6b goes high. Because
In this embodiment, the state in which the twisted pair line 6b is high (6c is low) is dominant (dominant), and the opposite state is recessive (inferior).

Next, a method of data transmission between the ECUs will be described. In this embodiment, a token passing method is adopted. This method is arbitrated CSMA / CD
(Carrier Sense Multiple Access / Collision Detecti
This method is advantageous in that it is advantageous in terms of electrical delay on the bus as compared with the (on) method, and that the maximum message delay time is easily obtained, thereby facilitating the design of a network system.

FIG. 4 is a diagram showing the format of a message used for data transmission in this embodiment. FIG. 4A shows the format of a data message for transmitting a token and data. b) shows the format of a token message for transmitting only the token. In the following description, the ECUs 1 to 5 that constitute the network system are called nodes.

In FIG. 4A, the field F1 (S
OM) is a field indicating the start of the message,
The bits consist of dominant bits. All nodes constituting the network system are used for synchronization.

The field F2 (TA) is a 4-bit field indicating the address (token address) of the token destination node. The node address is, for example, E
Values 0 to 4 are set corresponding to CUs 1 to 5, respectively.

Field F3 (CTL) is a field indicating the type of message (token message or data message).

A field F4 (DATA UNIT) is a data unit, and includes a DN (Destination Node) field indicating an address of a node to receive the message and a DLC (Da) indicating a byte length of the DATA field.
ta Length) field, I which constitutes the data identifier
It consists of a D (Identifier) field and a DATA field containing information to be transmitted.

The field F5 (FCS) is given by the following equation (1)
Consisting of a 16-bit error detection character string (CRC character string) obtained by using
(Cyclic Redundancy Check) field. A 1-bit recessive bit delimiter (separator) is inserted between the fields F5 and F6.

Generator polynomial = X ¹⁶ + X ¹² + X ⁵ +1 (1) Field F6 (DACK) is a field for a node that has normally received data to make a reception acknowledgment (acknowledge), and is a 2-bit acknowledge. Consists of slots. The transmitting node transmits the acknowledgment slot as a recessive bit, is designated as a node to receive, and all the nodes that have normally received data perform a reception acknowledgment by overwriting the two dominant bits. A two-bit recessive bit delimiter is inserted between the fields F6 and F7.

A field F7 (TACK) is a field for a node that has normally received the token to make a reception acknowledgment, and is composed of a 2-bit acknowledge slot as in the field F6. The transmitting node transmits the acknowledgment slot as a recessive bit, and the node that has received the token performs a reception acknowledgment by overwriting the two dominant bits. Field F
A 2-bit recessive bit delimiter is inserted between 7 and F8.

The field F8 (EOM) is a field indicating the end of the message, and is composed of 6 recessive bits.

The token message shown in FIG.
The configuration is such that fields F4 to F6 of the data message are deleted, and a delimiter is inserted between fields F3 and F7.

Next, a token circulation method will be described.

The node that has acquired the token must transfer the token together with the transmission data if the node has transmission data, or only the token if there is no transmission data to the next node. The node to which the token is transferred is the node corresponding to the token address indicated in the field F2 (TA) of the message. Normally, the token address is initially set to an address obtained by adding the value 1 to the address of the own node, and the message is transmitted by increasing the token address until an acknowledgment response is obtained. However,
In this embodiment, when the address of the own node is the value 15,
The token address is 0.

When the node corresponding to the token address receives the token, it responds with an acknowledgment by overwriting the acknowledge slot in field F7 (TACK) with two dominant bits. The acknowledgment is overwritten and the message is successfully returned in field F8 (EO
At the point of time up to M), the node that sent the token completes the token transfer, and the receiving node acquires the token.

Next, a method for detecting a transmission failure will be described.

Broadly speaking, there is no error during transmission, but the acknowledgment is not overwritten in the acknowledgment slot in the field F6 (DACK), or the error is detected during transmission. , The failure is detected at the sending node.

On the other hand, errors detected during transmission include monitoring detection, CRC detection, bit stuff error detection, and message format check detection.

The detection by monitoring is an error when the data transmitted by the transmitting node does not match the data on the bus. However, field F
The monitoring of the acknowledge slot of F6 and F7 and the following one recessive bit is prohibited.

The detection by the CRC is performed in the field F5 (F
If an error is detected by the CRC character of (CS), it is regarded as an error, and is performed by a node other than the transmitting node.

A bit stuff error is an error when the same logic is detected continuously beyond 5 bits, and is detected by a node other than the transmitting node. However, fields F6 (DACK), F7 (TA
CK), F8 (EOM) and delimiter are excluded from the detection target.

The detection by the message format check is an error when an illegal logic occurs in the fixed bit field (F3, F8, delimiter), and is detected by a node other than the transmission node.

When the above-described error during transmission is detected, an error message (6 dominant bits) is immediately transmitted from the detected node. Therefore,
Even when an error is detected in a node other than the transmission node, the transmission node can recognize occurrence of the error.

FIG. 5 is a flowchart showing a control procedure by the communication control IC 105 when transmission is completed (when an error message is generated or when message transmission is completed).

In step S1, it is determined whether or not an error has occurred during transmission, and if not, it is determined whether or not token transfer has been completed (whether or not there is a TACK) (step S2). As a result, when the token transfer is completed, first and second counters CT (to be described later)
1, CT2 is reset (step S10), and this process ends. If no error has occurred during transmission, but the transfer of the token has not been completed, the process proceeds to step S3, and it is determined whether or not data transmission has been successful (whether or not there is DACK). As a result, when the data transmission is successful, a token transfer process is performed (step S
9) The first and second counters CT1 and CT2 are reset (step S10), and the process ends.

If the answer to step S3 is negative (NO), that is, if no error occurred during transmission but token transfer and data transmission failed (acknowledgement response TACK, DA
If there is no CK), the process proceeds to step S4, and the first
Is incremented by one, and it is determined whether or not the count value is equal to a first predetermined value C1 (for example, 2) (step S5). At first, since CT1 <C1, retransmission processing of the message for which transmission failed is performed (step S8), and this processing ends. After that, there is no confirmation response, and when CT1 = C1, the process proceeds from step S5 to step S9, where the token is transferred to another node to reset the counters CT1 and CT2 (step S1).
0), this process ends.

If the answer to step S1 is affirmative (YES), that is, if an error has occurred during transmission, the second counter C
T2 is incremented by 1 (step S6), and it is determined whether or not the count value is equal to a second predetermined value C2 (for example, 5) larger than the first predetermined value C1 (step S7). At first, since CT2 <C2, retransmission processing of a message that failed to be transmitted is performed (step S8), and this processing ends. After that, an error occurred during transmission,
When CT2 = C2, steps S9 and S10 are executed, and the process ends.

According to the processing shown in FIG. 5, when transmission fails, retransmission is performed at most (C1-1) times when there is no acknowledgment, and at most (C1-1) when an error occurs during transmission.
2-1) The retransmission is performed only once, and if the transmission still fails, the token is transferred to another node.

Here, since C2> C1, the maximum number of retransmissions is larger when there is an error during transmission than when there is no acknowledgment. This is because if there is no acknowledgment, there is a high possibility that the node to be received does not exist, and it is highly likely that the node will fail even if retransmission is performed. This is because the possibility of success in retransmission due to the change is considered.

If the failure continues, the token is transferred to another node so that the token can be smoothly circulated.

As described above, according to the present embodiment, retransmission is performed a number of times according to the cause of transmission failure, and if transmission still fails, the token is transferred to another node. The number of retransmissions is reduced, and smooth circulation of tokens becomes possible. As a result, the data transmission efficiency of the entire transmission system can be improved.

[0058]

As described in detail above, according to the vehicle data transmission system of the first aspect, when data transmission fails, the type of transmission failure is specified, and the specified type of failure is identified by the receiving side. The number of retransmissions of data is set depending on whether an acknowledgment from is not obtained or the case where a transmission error is detected, and retransmission is performed only as many times as the number of retransmissions is not exceeded. If no acknowledgment is received from the receiving side, there is a high possibility that there is no node to receive, and there is a high possibility that retransmission will fail again. On the other hand, when a transmission error is detected, a situation in which retransmission is likely to succeed due to a change in the external environment or the like is reflected in the setting of the number of data retransmissions. Therefore, the reliability and speed of data transmission can be ensured, and the number of unnecessary retransmissions can be reduced.

According to the vehicle data transmission system of the present invention, when the number of transmission failures exceeds the number of retransmissions, the transmission right is transferred to another control device, so that the transmission right can be smoothly circulated. Thus, the data transmission efficiency of the entire transmission system can be improved.

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating a configuration of an electronic control device that configures the system of FIG. 1;

FIG. 3 is a diagram showing a specific configuration of a bus interface of FIG. 2;

FIG. 4 is a diagram showing a configuration of a message transmitted and received between electronic control devices.

FIG. 5 is a flowchart showing a processing procedure when data transmission is completed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine control electronic control unit 6 Network bus 101 Central processing unit (CPU) 105 Communication control IC 106 Bus interface

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-107704 (JP, A) JP-A-2-34084 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04Q 9/00 311 H04Q 9/00 321

Claims (3)

(57) [Claims] 1. A vehicle data transmission system for transmitting a message by connecting a plurality of control devices mounted on a vehicle via a network bus and circulating a transmission right between the plurality of control devices. Each of the control devices includes a transmission / reception unit for transmitting / receiving data, a transmission failure detection unit for detecting data transmission failure, and a specification unit for specifying a type of the transmission failure, wherein the transmission / reception unit
The identified transmission failure is acknowledged by the receiver.
If no transmission error or transmission error is detected.
A data transmission system for a vehicle, wherein the number of retransmissions of the data is set in accordance with the number of retransmissions, and the retransmission is performed a number of times not exceeding the number of retransmissions. 2. The vehicular data transmission system according to claim 1, wherein said transmission / reception means transfers the transmission right to another control device when the number of transmission failures exceeds the number of retransmissions. . 3. The method according to claim 1, wherein the number of retransmissions is an acknowledgment
When transmission errors are detected rather than when
2. The vehicle according to claim 1, wherein the number is set to be larger.
Data transmission system.