CN108023799B - Airborne dual-redundancy CAN bus communication method - Google Patents
Airborne dual-redundancy CAN bus communication method Download PDFInfo
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- CN108023799B CN108023799B CN201711110829.7A CN201711110829A CN108023799B CN 108023799 B CN108023799 B CN 108023799B CN 201711110829 A CN201711110829 A CN 201711110829A CN 108023799 B CN108023799 B CN 108023799B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L12/40052—High-speed IEEE 1394 serial bus
- H04L12/40078—Bus configuration
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L12/40169—Flexible bus arrangements
- H04L12/40176—Flexible bus arrangements involving redundancy
- H04L12/40182—Flexible bus arrangements involving redundancy by using a plurality of communication lines
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L12/40169—Flexible bus arrangements
- H04L12/40176—Flexible bus arrangements involving redundancy
- H04L12/40195—Flexible bus arrangements involving redundancy by using a plurality of nodes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L2012/40208—Bus networks characterized by the use of a particular bus standard
- H04L2012/40215—Controller Area Network CAN
Abstract
The invention belongs to the computer communication technology and discloses an airborne dual-redundancy CAN bus communication protocol. The invention defines and explains the airborne dual-redundancy CAN bus communication protocol. The dual-redundancy CAN bus communication protocol is characterized by being based on a dual-redundancy CAN communication system configuration. The communication protocol defines a dual redundancy message format, a dual redundancy identifier structure, a health status message data format. Based on the protocol, the CAN bus node application layer prepares the message to be sent, generates two redundant copies by the sending node and sends the two redundant copies on two channels respectively, and the two redundant copies are transmitted on two buses simultaneously. The received messages are compared and filtered by the receiver and then submitted to the upper layer application, and the protocol is transparent to the application layer, so that the reliability and the real-time performance of the system level of the airborne CAN bus network CAN be realized.
Description
The technical field is as follows:
the invention belongs to the technical field of computer communication, and relates to an airborne dual-redundancy CAN bus communication method.
Background art:
the standard CAN bus protocol (ISO 11898) is an industrial control field fieldbus standard, which is advantageous in terms of reliability, real-time performance, and low cost.
The standard CAN protocol provides a built-in fault tolerance mechanism that enables detection and recovery of transient errors on the communication link. Although the failure rate of the CAN bus messages is low, the CAN bus messages have better performance than other current buses, so that the CAN bus CAN be selected by an onboard system. Under certain extreme conditions, however, communication inconsistencies, unpredictability, or channel blockage may occur.
In addition, a system formed by the CAN bus may have a plurality of modes of physical faults, and some of the fault modes may have little influence on the system and some may cause the system or the nodes not to work normally. In actual applications, the probability of occurrence of these inherent limitations or physical failures varies depending on the application environment and the like. Especially under an airborne environment with high requirements on reliability and real-time performance, two faults, namely a permanent fault of a link and an uncertain transmission experiment, are difficult to tolerate.
The airborne application field provides a dual-redundancy CAN bus system configuration, which CAN effectively reduce the probability of communication system failure caused by the occurrence of the above faults. The invention provides a communication method aiming at a dual-redundancy CAN bus system configuration, which realizes effective management of dual-redundancy CAN bus communication.
The invention comprises the following contents:
the invention defines an airborne dual-redundancy CAN communication message format, a dual-redundancy identifier structure and a health state message data format based on the configuration of a dual-redundancy CAN communication system of a physical communication link.
An airborne dual-redundancy CAN bus communication method is characterized in that the method defines an airborne dual-redundancy CAN communication message format, a dual-redundancy identifier structure and a health state message data format based on a dual-redundancy CAN communication system configuration of a physical communication link; the method comprises the following steps:
a sending action: the application layer generates and sends two identical data to each message, the two data are recorded as a first sending data and a second sending data, the first sending data is submitted to a first channel for transmission, and the second sending data is submitted to a second channel for transmission;
a receiving act: in the receiving process, the CAN bus node receives data from two channels, wherein the data of the two channels are respectively a first part of received data and a second part of received data; from the aspect of time dimension, if the first part of received data arrives at the receiving node before the second part of received data, submitting the first part of received data to the application; if the second part of received data arrives at the receiving node before the first part of received data, submitting the second part of received data to the application;
the dual-redundancy CAN communication message format used by the method is compatible with the CAN2.0B standard message format of 29-bit extended frames, and 1-8 Bytes data CAN be transmitted in a single frame;
in the dual redundancy identifier structure used in the method, the function of each identifier bit is described as follows:
h) the LCC indicates the message sending priority level and supports different channel codes which are independent; the LCC occupies the 28 th to 26 th bits of the identifier domain;
i) the method comprises the steps that function coding identification Source FID indicates information of a message Source system, FID numbers are uniformly distributed by the whole system, and Source FID occupies 25 th to 19 th bits of an identifier;
j) reserving a reserved bit RSD for the identifier; RSD occupies identifier bit 18;
k) the local LCL indicates the physical transmission range of the message, and the LCL bit occupies the 17 th bit of the identifier;
l) private bit PVT indicates the special message bit, PVT occupies the 16 th bit of the message;
m) the data object code DOC indicates message target system information; the DOCs are uniformly distributed by the whole system, and occupy the 15 th to 2 nd bits of the identifier;
n) Redundant Channel Identifier (RCI) indicates redundant information bits of the message, and the RCI occupies 1-0 bit of the identifier;
the dual-redundancy CAN communication protocol also defines a CAN node health status message structure, and respectively defines NB _ RST 1, REC 1, TEC 1, NB _ RST 2, REC 2 and TEC 2 function description bits, wherein each function bit is described as follows:
NB _ RST 1: number of soft resets (USHORT) of the BUS A protocol processor;
REC 1: BUS A receives a value of an error counter (UCHAR);
TEC 1: BUS A sends the value of the error counter (UCHAR);
NB _ RST 2: number of soft resets (USHORT) of the BUS B protocol processor;
REC 2: BUS B receives a value of an error counter (UCHAR);
TEC 2: BUS B sends the value of the error counter (UCHAR).
A logic communication channel LCC based on a dual redundancy identifier structure, which is used for defining a message logic communication channel to manage CAN bus communication load; defining different priorities for the messages according to the value of the LCC bit, wherein the value is distributed according to the importance degree of the channel to the whole system;
the method defines the logical communication channel as follows:
h) exceptional event channel EEC: LCC encoding 000, the channel for fast and high priority message transmission, the channel for one-to-many communication;
i) normal operation channel NOC: LCC coding 010, the channel is used for periodic or aperiodic data transmission, the channel is used in one-to-many communication;
j) node service channel NSC: LCC encodes 100, which provides point-to-point communication for "client/server" type services.
k) User-defined channel UDC: LCC codes 101, the channel is used for transmitting CAN extension frames which are not suitable for being transmitted by other channels;
l) test and maintenance channel TMC: LCC code 110 to support test and maintenance functions;
m) CAN basic frame compatible channel FMC: LCC code 111, which is adapted to CAN application layer based on CAN basic frame, such as CANaerospace;
n) the channel marked "reserved" is used as a complement and cannot be used for other purposes.
The invention has the advantages that:
1) the CAN bus has high communication reliability;
2) the CAN bus communication real-time performance is good;
3) the protocol is transparent to the application layer;
4) the node health state real-time reporting capability is achieved;
5) the system cost is low.
Drawings
Fig. 1 is a dual-redundancy CAN bus message identifier structure.
Fig. 2 is a dual redundancy protocol health status message data format.
The specific implementation mode is as follows:
the invention provides a dual-redundancy CAN bus communication method aiming at an airborne dual-redundancy CAN communication system. The communication method defines a dual-redundancy message format, a dual-redundancy identifier structure and a health state message data format, a CAN bus node application layer prepares a message to be sent, and a sending node generates two redundant copies and sends the two redundant copies on two channels respectively to be transmitted on two physical buses. The receiving node compares and filters the received messages and submits the messages to the application, and the method is transparent to the application layer. As long as a normally working communication link exists, the CAN bus message CAN be normally sent to the destination node, and the reliability of CAN bus communication is effectively improved. The CAN bus message CAN not be delayed to arrive due to the blockage of a certain communication link, and the real-time performance of CAN bus communication is effectively improved.
The dual-redundancy message format used by the dual-redundancy CAN bus communication method is compatible with the message format of a CAN2.0B standard 29-bit extended frame, and CAN transmit data of 1-8 Bytes in a single frame.
In the dual-redundancy identifier structure, the identifier field in the can2.0b specification is further divided into several sub-fields to support message identification, routing and data integrity check. The CAN message identifier field is shown in fig. 1.
The dual-redundancy identifier structure used by the dual-redundancy CAN bus communication method is shown in fig. 1, and the functions of each identifier bit are described as follows:
a) a Logical Communication Channel (LCC) indicates a message transmission priority level and supports different channel codes independent of each other. LCC occupies the 28 th to 26 th bits of the identifier field. The value of LCC bit has decisive effect on the priority of message, and the value is uniformly distributed by the system design;
b) a function encoding identification (Source FID) indicates information of a message Source system, FID numbers are uniformly distributed by the whole system, and the Source FID occupies 25 th to 19 th bits of an identifier;
c) reserved bits (RSD) are reserved for the identifier, which occupies bit 18 of the identifier. The RSD is only defined as a service message type bit (SMT) bit when the point-to-point communication is carried out, and is used for indicating the direction of data flow between the client and the server and is not used in other communication modes;
d) the local bit (LCL) indicates the physical transmission range of the message, and the LCL bit occupies the 17 th bit of the identifier. The position of 1 indicates that the message is only transmitted in the network where the sending node is located, and the gateway cannot transmit the messages to other networks;
e) private bits (PVT) indicate dedicated message bits, PVT occupies message bit 16. For identifying messages for dedicated use, the message at position "1" indicates that the message is not publicly described and is only for dedicated use. Without special use, the position is usually "0";
f) the Data Object Code (DOC) indicates message target system information. The DOCs are uniformly distributed by the whole system, and occupy the 15 th to 2 nd bits of the identifier;
g) the Redundant Channel Identifier (RCI) indicates redundant information bits of the message, and the RCI occupies 1-0 bit of the identifier. The 1 st bit of RCI is defined as a message ID sequence number (ISn) bit in point-to-point communication, which is used to indicate the number of redundant message IDs and distinguish different message instances of the same message ID that are sent successively. The sender should accumulate the message ID serial number before sending out the message each time, and the receiver distinguishes and filters the redundant message according to the message ID serial number. The 0 th bit of the RCI is defined as a Redundant Device Identification (RDI) bit to indicate point-to-point message numbers of the same ID issued by different nodes in the same network. In this case, the RDI in the message ID sent out by one device is always set to 0, and the RDI in the message ID sent out by the other device is always set to 1.
Based on the LCC domain with the dual-redundancy identifier structure, a user CAN define a message logic communication channel to manage CAN bus communication load, and communication reliability and real-time performance are improved. Different priorities are defined for the messages according to the value of the LCC bit, and the value is distributed according to the importance degree of the channel to the whole system. The logical communication channel assignments are shown in table 1.
TABLE 1 logical communication channel assignment
The dual-redundancy CAN bus communication method defines logic communication channels as follows:
a) exceptional Event Channel (EEC): LCC codes 000, the channel is used for fast and high priority message transmission, and the message transmission of the channel is prior to other message transmission. These events typically require immediate action to be taken. The channel is used for one-to-many communication;
b) normal Operating Channel (NOC): LCC coding 010, the channel is used for periodic or aperiodic data transmission, the channel is used in one-to-many communication;
c) node Service Channel (NSC): LCC encodes 100, which provides point-to-point communication for "client/server" type services. These services may be connectionless communications or connection-oriented communications;
d) user Defined Channel (UDC): LCC codes 101, the channel is used to transmit CAN extension frames which are not suitable for transmission by other channels, and other subdomain structures outside the LCC at the channel message position CAN be customized;
e) test and Maintenance Channel (TMC): LCC code 110 to support test and maintenance functions;
f) CAN basic frame compatible channel (FMC): LCC codes 111, which channel is suitable for CAN application layer (e.g., CANaerospace) based on CAN basic frames. Other sub-domains outside the LCC at the channel message can be customized;
g) the channel marked "reserved" is used as a complement and cannot be used for other purposes.
In order to correctly reflect the health status of two redundancy communication links in dual redundancy communication, the dual redundancy CAN communication protocol also supplementarily defines a CAN node health status message structure, as shown in fig. 2.
The CAN node health status message structure bit function is described as follows:
NB _ RST 1: number of soft resets (USHORT) of the BUS A protocol processor;
REC 1: BUS A receives a value of an error counter (UCHAR);
TEC 1: BUS A sends the value of the error counter (UCHAR);
NB _ RST 2: number of soft resets (USHORT) of the BUS B protocol processor;
REC 2: BUS B receives a value of an error counter (UCHAR);
TEC 2: BUS B sends the value of the error counter (UCHAR).
Claims (2)
1. An airborne dual-redundancy CAN bus communication method is characterized in that the method defines an airborne dual-redundancy CAN communication message format, a dual-redundancy identifier structure and a health state message data format based on a dual-redundancy CAN communication system configuration of a physical communication link; the method comprises the following steps:
a sending action: the application layer generates and sends two identical data to each message, the two data are recorded as a first sending data and a second sending data, the first sending data is submitted to a first channel for transmission, and the second sending data is submitted to a second channel for transmission;
a receiving act: in the receiving process, the CAN bus node receives data from two channels, wherein the data of the two channels are respectively a first part of received data and a second part of received data; from the aspect of time dimension, if the first part of received data arrives at the receiving node before the second part of received data, submitting the first part of received data to the application; if the second part of received data arrives at the receiving node before the first part of received data, submitting the second part of received data to the application; the receiving node compares and filters the received message and submits the message to the application, and the method is transparent to the application layer;
the dual-redundancy CAN communication message format used by the method is compatible with the CAN2.0B standard message format of 29-bit extended frames, and CAN transmit data of 1-8 Bytes in a single frame;
in the dual redundancy identifier structure used in the method, the function of each identifier bit is described as follows:
a) the LCC indicates the message sending priority level and supports different channel codes which are independent; the LCC occupies the 28 th to 26 th bits of the identifier domain;
b) the method comprises the steps that function coding identification Source FID indicates information of a message Source system, FID numbers are uniformly distributed by the whole system, and Source FID occupies 25 th to 19 th bits of an identifier;
c) reserving a reserved bit RSD for the identifier; RSD occupies identifier bit 18;
d) the local LCL indicates the physical transmission range of the message, and the LCL bit occupies the 17 th bit of the identifier;
e) private bit PVT indicates the special message bit, and PVT occupies the 16 th bit of the message;
f) the data object code DOC indicates message target system information; the DOCs are uniformly distributed by the whole system, and occupy the 15 th to 2 nd bits of the identifier;
g) the Redundant Channel Identifier (RCI) indicates a redundant information bit of the message, and the RCI occupies 1-0 bit of the identifier;
in order to correctly reflect the health states of two redundancy communication links in dual-redundancy communication, the dual-redundancy CAN communication protocol further defines a CAN node health state message structure, and defines NB _ RST 1, REC 1, TEC 1, NB _ RST 2, REC 2, and TEC 2 function description bits respectively, and each function bit is described as follows:
NB _ RST 1: number of soft resets (USHORT) of the BUS A protocol processor;
REC 1: BUS A receives a value of an error counter (UCHAR);
TEC 1: BUS A sends the value of the error counter (UCHAR);
NB _ RST 2: number of soft resets (USHORT) of the BUS B protocol processor;
REC 2: BUS B receives a value of an error counter (UCHAR);
TEC 2: BUS B sends the value of the error counter (UCHAR);
a logic communication channel LCC based on a dual redundancy identifier structure, which is used for defining a message logic communication channel to manage CAN bus communication load; different priorities are defined for the messages according to the value of the LCC bit, and the value is distributed according to the importance degree of the channel to the whole system.
2. The method of claim 1 wherein said CAN bus communication system is a dual-redundancy CAN bus communication system,
the method defines the logical communication channel as follows:
a) exceptional event channel EEC: LCC encoding 000, the channel for fast and high priority message transmission, the channel for one-to-many communication;
b) normal operation channel NOC: LCC coding 010, the channel is used for periodic or aperiodic data transmission, the channel is used in one-to-many communication;
c) node service channel NSC: LCC code 100, which provides point-to-point communication for "client/server" type services;
d) user-defined channel UDC: LCC codes 101, the channel is used for transmitting CAN extension frames which are not suitable for being transmitted by other channels;
e) test and maintenance channel TMC: LCC code 110 to support test and maintenance functions;
f) CAN basic frame compatible channel FMC: LCC codes 111, the channel is suitable for CAN application layer based on CAN basic frame, the CAN application layer is CANaerospace;
g) the channel marked "reserved" is used as a complement and cannot be used for other purposes.
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| CN103490959A (en) * | 2013-10-10 | 2014-01-01 | 北京航天发射技术研究所 | Dual-redundancy CAN bus fault detection method |
| CN103490966A (en) * | 2013-10-10 | 2014-01-01 | 北京航天发射技术研究所 | Dual-redundancy CAN bus data receiving and processing method |
| CN103516571A (en) * | 2013-07-22 | 2014-01-15 | 浙江中控研究院有限公司 | System architecture and method for ensuring data communication reliability by means of double CAN buses |
| CN105743755A (en) * | 2016-04-19 | 2016-07-06 | 上海君协光电科技发展有限公司 | Dual-redundant CAN bus communication system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103516571A (en) * | 2013-07-22 | 2014-01-15 | 浙江中控研究院有限公司 | System architecture and method for ensuring data communication reliability by means of double CAN buses |
| CN103490959A (en) * | 2013-10-10 | 2014-01-01 | 北京航天发射技术研究所 | Dual-redundancy CAN bus fault detection method |
| CN103490966A (en) * | 2013-10-10 | 2014-01-01 | 北京航天发射技术研究所 | Dual-redundancy CAN bus data receiving and processing method |
| CN105743755A (en) * | 2016-04-19 | 2016-07-06 | 上海君协光电科技发展有限公司 | Dual-redundant CAN bus communication system |
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