JP2012129771A - Communication node, communication system and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent out-of-synchronization between communication nodes.SOLUTION: The communication node performs communication using a time division multiple access system where the length of a frame to be transmitted/received can be changed. The communication node comprises: a data length detecting unit detecting the length of the frame on the basis of the frame received from another communication node; a data length determining unit determining whether the length of the frame detected by the data length detecting unit is equal to or smaller than a first threshold or equal to or larger than a second threshold; and a timing correcting unit that corrects a transmission/reception timing when the data length determining unit determines that the data length detected by the data length detecting unit is equal to or smaller than the first threshold or equal to or larger than the second threshold. The timing correcting unit corrects the transmission/reception timing in consideration that the frame has not been received.

Description

  The present invention relates to a communication system mounted on a vehicle, for example.

  In many cases, a vehicle-mounted network is configured in a vehicle to perform various controls in the vehicle. The in-vehicle network is realized by connecting many electronic control units (ECUs), sensors, actuators, and the like to the LAN. Hereinafter, electronic control devices, sensors, actuators, and the like connected to the in-vehicle network are referred to as communication nodes. The communication node is installed at various positions in the vehicle. Communication nodes are connected by communication lines or electric wires.

JP 2003-304213 A

  For example, an in-vehicle network is configured by connecting a plurality of communication nodes to a data bus. In some in-vehicle networks, a plurality of communication nodes communicate with each other by a time division multiple access method in which a transmission / reception frame length can be varied. The time division multiple access method in which the transmission / reception frame length can be made variable is sometimes called a variable time division multiple access method (Flexible TDMA (Time Division Multiple Access)).

  The in-vehicle network includes CAN (Controller Area Network) and LIN (Local Interconnect Network). The vehicle-mounted network may include a device that performs communication according to FlexRay (registered trademark).

  For example, in an in-vehicle network that performs communication according to FlexRay, scheduling related to transmission and reception between communication nodes is performed in advance. In the in-vehicle network, messages to be transmitted and received are determined according to time. For example, the message includes information indicating the measurement value of the meter. Each communication node performs communication according to the scheduling. In an in-vehicle network that performs communication according to FlexRay, each communication node is synchronized. For example, it may be reset at a predetermined cycle and synchronized again. Therefore, the timing for transmitting and receiving signals is the same between different communication nodes.

  However, signals transmitted and received between communication nodes may be affected by noise. When signals transmitted / received between communication nodes are affected by noise, there may be a difference in transmission / reception timing between different communication nodes. For example, a signal to be received in a certain slot may not be received in the certain slot.

FIG. 1 shows an example of a communication system. The communication node 10 _1, the communication node 10 ₂ is connected via a communication bus 15.

Figure 2 shows a communication node 10 _1, an example of transmission timings of signals by the communication node 10 _2. According to FIG. 2, the communication node 10 ₁ is provided with a slot 1, send in slot 3. The communication node 10 ₂ transmits in slot 2.

  FIG. 3 illustrates frame collisions that can occur due to noise effects.

Communication is started according to the scheduling shown in FIG. The communication node 10 ₁ transmits the data a1 by slot 1. The data a1 are to be received by the communication node 10 _2. Communication node 10 ₂ awaits the data a1 in slot 1. However, there are cases where data a1 transmitted by the communication node 10 ₁ is affected by noise. Due to the influence of the noise, the communication node 10 ₂ may at the timing to receive the slot 1 can not receive the data a1. For example, the communication node 10 ₂ can not receive the data a1 at the timing to receive the slots 1, there are cases where postponed until slot 2. If postponed until slot 2, the communication node 10 _2, the slot 2, has been scheduled to transmit data b1, can not transmit data b1 in slot 2, delayed until the slot 3. Slot 3, the communication node 10 ₁ is a timing to transmit the data a2. If the timing of the data b2 is transmitted by the communication node 10 ₂ I slipped into the slot 3, and the data b2, data a2 transmitted by the communication node 10 ₁ collides.

  As described above, a shift in timing of transmission / reception between different communication nodes occurs, resulting in loss of synchronization. As a result of continuing communication in a state where synchronization has been lost, there is a risk of signal collision.

  The present invention has been made in view of the above points, and is to reduce loss of synchronization between communication nodes.

This communication node
A communication node that performs communication according to a time division multiple access method that can change the length of a frame to be transmitted and received,
A data length detector for determining the length of the frame based on the frame received from another communication node;
A data length determination unit that determines whether the length of the frame detected by the data length detection unit is equal to or less than a first threshold value or equal to or greater than a second threshold value;
Timing correction for correcting transmission / reception timing when the data length determination unit determines that the data length detected by the data length detection unit is equal to or less than the first threshold value or equal to or greater than the second threshold value. And
The timing correction unit corrects transmission / reception timing on the assumption that the frame has not been received.

This communication system
A communication system in which each communication node communicates in accordance with a time division multiple access scheme that can vary the length of a frame to be transmitted and received,
Each communication node
A data length detector for determining the length of the frame based on the frame received from another communication node;
A data length determination unit for determining whether the length of the frame detected by the data length detection unit is equal to or less than a first threshold value or equal to or greater than a second threshold value;
Timing correction for correcting transmission / reception timing when the data length determination unit determines that the data length detected by the data length detection unit is equal to or less than the first threshold value or equal to or greater than the second threshold value. And
The timing correction unit corrects transmission / reception timing on the assumption that the frame has not been received.

This method
A method in a communication node that performs communication according to a time division multiple access method that can vary the length of a frame to be transmitted and received,
A data length detection step for obtaining a length of the frame based on a frame received from another communication node;
A data length determination step for determining whether the length of the frame detected by the data length detection step is less than or equal to the first threshold or greater than or equal to the second threshold;
Timing correction for correcting the transmission / reception timing when it is determined by the data length determination step that the data length detected by the data length detection step is not more than the first threshold value or not less than the second threshold value. Steps and
The timing correction step corrects the transmission / reception timing on the assumption that the frame has not been received.

  According to the disclosed embodiment, loss of synchronization between communication nodes can be reduced.

It is a figure which shows an example of a communication system. It is a figure which shows an example of communication scheduling. It is explanatory drawing which shows the case where a frame collision arises. It is a block diagram which shows an example of the communication system according to a present Example. It is a block diagram which shows an example of the communication node according to a present Example. It is a functional block diagram which shows an example of the communication node according to a present Example. It is explanatory drawing which shows an example of operation | movement of the communication node according to a present Example. It is explanatory drawing which shows an example of operation | movement of the communication node according to a present Example. It is explanatory drawing which shows an example of operation | movement of the communication node according to a present Example. It is a flowchart which shows an example of operation | movement of the communication node according to a present Example.

Next, the form for implementing this invention is demonstrated, referring drawings based on the following Examples.
In all the drawings for explaining the embodiments, the same reference numerals are used for those having the same function, and repeated explanation is omitted.

<Example>
<Communication system>
FIG. 4 shows an outline of a communication system according to the present embodiment.

The communication system includes a communication node 100 _n (n is an integer satisfying n> 0). FIG. 4 shows a case where n = 4 as an example. The value of n can be changed as appropriate. The communication node 100 _n may be realized by an electronic control unit or the like. The electronic control unit may be for system control. The communication node 100 _n is mounted on a moving body such as a vehicle, for example. In this embodiment, as an example, a case where it is mounted on a vehicle will be described.

The communication nodes 100 _n are connected by a communication bus 150. The communication nodes 100 _n can communicate with each other by a predetermined communication protocol via the communication bus 150. The topology of the communication protocol is not limited to the bus type shown in FIG. 4, but may be a star type. Also, a hybrid type in which a bus type and a star type are combined may be used. In the communication protocol, scheduling is performed to preset information to be communicated and a time to be communicated between the communication nodes 100 _n . In other words, the communication node 100 _n transmits information that should be transmitted in a preset transmission time frame according to the scheduling. The preset transmission time frame may be called a slot. The communication system differs from a general communication system in that information to be transmitted is transmitted within a preset transmission time frame. This is because, in a general communication system, only a time during which communication is possible is set. The communication protocol includes FlexRay.

In addition, communication is performed between the communication nodes 100 _n according to the variable time division multiple access method. In the variable time division multiple access method, a transmission time frame is secured for a communication node having data to be transmitted. The transmission time frame is also called a slot. Further, the transmission time frame is set to the minimum for a communication node having no data to be transmitted. Hereinafter, the minimum transmission time frame to be set for a communication node having no data to be transmitted is referred to as a “minimum transmission time frame”. A communication node that generates data to be transmitted due to a predetermined event makes a transmission request. A transmission time frame is set by the transmission request. By setting the transmission time frame to be variable, synchronization is established between the communication nodes. In addition, a multi-master method may be applied to the communication system. In the multi-master system, any communication node can communicate when the bus is free.

  In this communication system, a minimum value (hereinafter referred to as “first threshold”) and a maximum value (hereinafter referred to as “second threshold”) of data to be transmitted and received between communication nodes are set in advance. The The first threshold is a value less than the second threshold. In this communication system, in addition to the first threshold value and the second threshold value, a minimum value of the length of data to be transmitted / received between communication nodes is set in advance. Hereinafter, the minimum value of the length of data to be transmitted and received between communication nodes is referred to as “minimum transmission data length”. Hereinafter, the length of data to be transmitted / received between communication nodes is referred to as “data length”. The data length may be a frame length. The frame may include one or more slots.

<Communication node>
The communication node 100 _n performs at least one of signal transmission and reception between the communication node 100 _n connected to the communication node 100 _n.

The communication node 100 _n determines whether the data length of data from another communication node is equal to or less than the first threshold value or equal to or greater than the second threshold value. When the communication node 100 _n determines that the data length of the data from the other communication node is equal to or less than the first threshold value or equal to or greater than the second threshold value, the data from the other communication node is abnormal. to decide. The first threshold is preferably the frame header length. The second threshold value is preferably the maximum value of the data length transmitted in the communication system. This is because the detection accuracy of abnormal frames can be improved.

When the communication node 100 _n determines that the data length of data from another communication node is equal to or smaller than the first threshold, the communication node 100 _n determines the slot according to the number of minimum transmission data length corresponding to the data length of the data To proceed.

On the other hand, if the communication node 100 _n determines that the data length of data from other communication nodes is _equal to or greater than the second threshold value, the communication node 100 _n determines that the slot has received data having a data length corresponding to the second threshold value To proceed.

When the communication node 100 _n determines that the received data is abnormal, the communication node 100 _n advances the slot number in units of the minimum transmission data length, or advances the process on the assumption that data having a data length corresponding to the second threshold is received. can do. For this reason, even when abnormal data is received, the operation can be performed in the same manner as when no abnormality has occurred, so that the slot shift between communication nodes can be reduced.

Figure 5 shows this first communication node 100 _n. FIG. 5 mainly shows a hardware configuration.

This communication node 100 _n has an MPU (Micro-Processing Unit) 102. MPU102 communicates node 100 _n overall control.

The communication node 100 _n includes a communication module 104. The communication module 104 performs a communication module of another communication node 100 _n, a communication. For example, communication is performed according to a communication protocol.

The communication node 100 _n includes a storage unit 106. The storage unit 106 stores a program for causing the MPU 102 to function as the communication node 100 _n . Further, the storage unit 106 stores a first threshold value and a second threshold value of the data length. The storage unit 106 stores the minimum transmission data length.

  The MPU 102, the communication module 104, and the storage unit 106 are connected to each other via a bus 50.

<Communication node functions>
FIG. 6 shows the function of the communication node 100 _n . FIG. 6 mainly shows functions executed by the MPU 102.

The communication node 100 _n has a decoding unit 1022. The decoding unit 1022 receives a frame from another communication node received by the communication module 104. The decoding unit 1022 decodes the input frame. The decoding unit 1022 inputs the decoded frame to the data length determination unit 1024.

The communication node 100 _n includes a data length determination unit 1024. The data length determination unit 1024 is connected to the decoding unit 1022. The data length determination unit 1024 obtains the data length based on the decoded frame to be input by the decoding unit 1022. The data length determination unit 1024 determines that the data length of the decoded frame to be input by the decoding unit 1022 is based on the first threshold value and the second threshold value to be stored by the storage unit 106. It is determined whether it is below the threshold or above the second threshold.

  FIG. 7 shows an example of the operation of the data length determination unit 1024.

  When the data length determination unit 1024 determines that the data length of the decoded frame to be input by the decoding unit 1022 is equal to or less than the first threshold (1), the data length determination unit 1024 determines that the decoded frame is abnormal. .

  When the data length determination unit 1024 determines that the data length of the decoded frame to be input by the decoding unit 1022 is equal to or greater than the second threshold (3), the data length determination unit 1024 determines that the decoded frame is abnormal. .

  When the data length determination unit 1024 determines that the data length of the decoded frame to be input by the decoding unit 1022 is greater than the first threshold and less than the second threshold (2), the decoded frame Is determined to be normal.

  When the data length determination unit 1024 determines that the decoded frame is abnormal, the timing correction unit 1026 indicates information indicating that the decoded frame is abnormal and the data length of the decoded frame. Enter information.

The communication node 100 _n includes a timing correction unit 1026. The timing correction unit 1026 is connected to the data length determination unit 1024.

  The timing correction unit 1026 determines transmission / reception timing based on information indicating that the decoded frame to be input by the data length determination unit 1024 is abnormal and information indicating the data length of the decoded frame. to correct. For example, the timing correction unit 1026 corrects the transmission / reception timing on the assumption that a frame determined to be abnormal has not been received. Specifically, the slot number to be transmitted and the slot number to be received are corrected.

<When the data length is equal to or less than the first threshold>
FIG. 8 shows an example of correction of transmission / reception timing when the data length is equal to or smaller than the first threshold.

  In the example shown in FIG. 8, the frame indicated by (1) is received. The data length of the received frame is not more than the first threshold value.

  In the conventional transmission node, the frame indicated by (1) is regarded as normal, and as indicated by (2), after the frame indicated by (1) is received, the slot corresponding to the next number is received. The frame was transmitted and received. However, since the frame indicated by (1) may be noise, the frame indicated by (1) includes a frame to be originally transmitted and a frame transmitted by the slot corresponding to the next number. There was a possibility of a collision.

As shown in (3), this communication node 100 _n determines how many minimum transmission data lengths are included in the received frame when a frame whose data length is equal to or smaller than the first threshold is received. Then, the slot number is advanced by the number of the minimum transmission data length included in the received frame. By advancing the slot number by the number of the minimum transmission data length included in the reception frame, the transmission / reception timing can be corrected in slot units. In the example shown in FIG. 8, since the received frame includes three minimum transmission data lengths, the slot number is advanced by 3. Therefore, a frame to be transmitted or received after the received frame is transmitted or received by the slot of number 4.

<When the data length is greater than or equal to the second threshold>
FIG. 9 illustrates an example of transmission / reception timing correction when the data length is equal to or greater than the second threshold.

  In the example shown in FIG. 9, the frame indicated by (1) is received. The data length of the received frame is greater than or equal to the second threshold.

  In the conventional transmission node, the frame indicated by (1) is regarded as normal, and as indicated by (2), after the frame indicated by (1) is received, the slot corresponding to the next number is received. The frame was transmitted and received. However, since the frame indicated by (1) may be affected by noise, the frame indicated by (1) may collide with a frame transmitted from another communication node. .

  In this communication node, as shown in (3), when a frame having a data length equal to or larger than the second threshold is received, the data length of the received frame is regarded as the second threshold. By regarding the data length of the received frame as the second threshold value, the transmission / reception timing can be corrected in slot units. In the example shown in FIG. 9, a frame to be transmitted after the received frame is transmitted by the slot of number 2.

<Operation of communication system>
FIG. 10 shows an example of the operation of the communication system. FIG. 10 shows the operation of the communication node included in the communication system.

  In this communication system, scheduling is performed, and information to be communicated and time to be communicated are set in advance.

The communication node 100 _n is from another communication node, receives the data (step S1002). For example, the communication module 104 receives data transmitted by other communication nodes according to scheduling.

The communication node 100 _n obtains the data length. For example, a frame received by the communication module 104 is input to the decoding unit 1022. The decoding unit 1022 decodes the received frame and inputs it to the data length determination unit 1024. The data length determination unit 1024 obtains the data length based on the decoded frame from the decoding unit 1022.

The communication node 100 _n, the data length obtained in step S1004 it is determined whether the abnormality. For example, the data length determination unit 1024 determines whether the data length is less than or equal to the first threshold value or greater than or equal to the second threshold value. When the data length is equal to or smaller than the first threshold value or equal to or larger than the second threshold value, it is determined that the data length is abnormal. On the other hand, if the data length is longer than the first threshold and less than the second threshold, it is determined that the data length is normal.

  When it is determined that the data length is normal (step S1006: NO), normal operation is continued (step S1008). Transmission / reception timing is not corrected, and communication according to scheduling is continued.

If the data length is determined to be abnormal (step S1006: YES), the communication node 100 _n corrects the reception timing of data. For example, when a frame whose data length is equal to or less than the first threshold is received, the timing correction unit 1026 determines how many minimum transmission data lengths are included in the received frame, and the minimum included in the received frame The slot number is advanced by the number of transmission data lengths. For example, when a frame whose data length is equal to or greater than the second threshold is received, the timing correction unit 1026 regards the data length of the received frame as the second threshold.

  The timing correction unit 1026 inputs information indicating the corrected slot to the communication module 104. The communication module 104 controls the transmission / reception timing according to the corrected slot number input by the timing correction unit 1026.

  In this embodiment, the minimum transmission data length may be set in advance. In addition, when data having a data length equal to or smaller than the first threshold is received as the minimum transmission data length, the data length may be stored. By storing the data length when data having a data length equal to or smaller than the first threshold is received, the timing can be corrected without setting the minimum transmission data length.

This communication node
A communication node that performs communication according to a time division multiple access method that can change the length of a frame to be transmitted and received,
Based on a frame received from another communication node, a data length detection unit as a data length determination unit for obtaining the length of the frame;
A data length determination unit that determines whether the length of the frame detected by the data length detection unit is equal to or less than a first threshold value or equal to or greater than a second threshold value;
Timing correction for correcting transmission / reception timing when the data length determination unit determines that the data length detected by the data length detection unit is equal to or less than the first threshold value or equal to or greater than the second threshold value. And
The timing correction unit corrects transmission / reception timing on the assumption that the frame has not been received.

further,
A storage unit for storing a frame length determined by the data length determination unit to be equal to or less than the first threshold;
The timing correction unit corrects the synchronization timing based on the frame length stored in the storage unit.

further,
The first threshold is a header length of the frame, and the second threshold is a maximum value of a data length transmitted / received in the communication system.

further,
The timing correction unit includes the storage included in the frame detected by the data length detection unit when it is determined that the length of the frame detected by the data length detection unit is equal to or less than a first threshold. The timing is corrected by advancing the slot number by the number of frames stored in the section.

further,
The timing correction unit, when it is determined that the length of the frame detected by the data length detection unit is greater than or equal to a second threshold, the length of the frame detected by the data length detection unit is The timing is corrected by assuming the second threshold value.

This communication system
A communication system in which each communication node communicates in accordance with a time division multiple access scheme that can vary the length of a frame to be transmitted and received,
Each communication node
A data length detector for determining the length of the frame based on the frame received from another communication node;
A data length determination unit that determines whether the length of the frame detected by the data length detection unit is equal to or less than a first threshold value or equal to or greater than a second threshold value;
Timing correction for correcting transmission / reception timing when the data length determination unit determines that the data length detected by the data length detection unit is equal to or less than the first threshold value or equal to or greater than the second threshold value. And
The timing correction unit corrects transmission / reception timing on the assumption that the frame has not been received.

This method is a method in a communication node that performs communication according to a time division multiple access method that can vary the length of a frame to be transmitted and received,
A data length detection step for obtaining a length of the frame based on a frame received from another communication node;
A data length determination step for determining whether the length of the frame detected by the data length detection step is equal to or less than a first threshold value or equal to or greater than a second threshold value;
Timing correction for correcting the transmission / reception timing when it is determined by the data length determination step that the data length detected by the data length detection step is not more than the first threshold value or not less than the second threshold value. Steps and
The timing correction step corrects the transmission / reception timing on the assumption that the frame has not been received.

  Although the present invention has been described above with reference to specific embodiments and modifications, each embodiment and modification is merely illustrative, and those skilled in the art will recognize various modifications, modifications, alternatives, and substitutions. You will understand examples. For convenience of explanation, an apparatus according to an embodiment of the present invention has been described using a functional block diagram, but such an apparatus may be implemented in hardware, software, or a combination thereof. The present invention is not limited to the above-described embodiments, and various variations, modifications, alternatives, substitutions, and the like are included without departing from the spirit of the present invention.

10 ₁ , 10 ₂ Communication node 15 Communication bus 100 _n (n is an integer of n> 0) Communication node 102 MPU (Micro-Processing Unit)
1022 Decoding unit 1024 Data length determination unit 1026 Timing correction unit 104 Communication module 106 Storage unit 150 Communication bus

Claims (7)

A communication node that performs communication according to a time division multiple access method that can change the length of a frame to be transmitted and received,
A data length detector for determining the length of the frame based on the frame received from another communication node;
A data length determination unit that determines whether the length of the frame detected by the data length detection unit is equal to or less than a first threshold value or equal to or greater than a second threshold value;
Timing correction for correcting transmission / reception timing when the data length determination unit determines that the data length detected by the data length detection unit is equal to or less than the first threshold value or equal to or greater than the second threshold value. And
The communication node, wherein the timing correction unit corrects transmission / reception timing on the assumption that the frame is not received. The communication node according to claim 1,
A storage unit for storing a frame length determined by the data length determination unit to be equal to or less than the first threshold;
The timing correction unit is a communication node that corrects synchronization timing based on a frame length stored in the storage unit. In the communication node according to claim 1 or 2,
The communication node, wherein the first threshold is a header length of a frame, and the second threshold is a maximum value of a data length transmitted and received in the communication system. The communication node according to claim 2, wherein
The timing correction unit includes the storage included in the frame detected by the data length detection unit when it is determined that the length of the frame detected by the data length detection unit is equal to or less than a first threshold. A communication node that corrects timing by advancing the slot number by the number of frames stored in the section. The communication node according to claim 1,
The timing correction unit, when it is determined that the length of the frame detected by the data length detection unit is greater than or equal to a second threshold, the length of the frame detected by the data length detection unit is A communication node that corrects timing by assuming that it is a second threshold value. A communication system in which each communication node communicates in accordance with a time division multiple access scheme that can vary the length of a frame to be transmitted and received,
Each communication node
A data length detector for determining the length of the frame based on the frame received from another communication node;
A data length determination unit that determines whether the length of the frame detected by the data length detection unit is equal to or less than a first threshold value or equal to or greater than a second threshold value;
Timing correction for correcting transmission / reception timing when the data length determination unit determines that the data length detected by the data length detection unit is equal to or less than the first threshold value or equal to or greater than the second threshold value. And
The said timing correction part is a communication system which correct | amends transmission / reception timing on the assumption that the said frame was not received. A method in a communication node that performs communication according to a time division multiple access method that can vary the length of a frame to be transmitted and received,
A data length detection step for obtaining a length of the frame based on a frame received from another communication node;
A data length determination step for determining whether the length of the frame detected by the data length detection step is equal to or less than a first threshold value or equal to or greater than a second threshold value;
Timing correction for correcting the transmission / reception timing when it is determined by the data length determination step that the data length detected by the data length detection step is not more than the first threshold value or not less than the second threshold value. Steps and
The timing correction step corrects transmission / reception timing on the assumption that the frame is not received.

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