CN109842456A - A kind of clock synchronizing method based on AFDX network - Google Patents
A kind of clock synchronizing method based on AFDX network Download PDFInfo
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- CN109842456A CN109842456A CN201910228060.1A CN201910228060A CN109842456A CN 109842456 A CN109842456 A CN 109842456A CN 201910228060 A CN201910228060 A CN 201910228060A CN 109842456 A CN109842456 A CN 109842456A
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- clock jitter
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Abstract
The invention discloses a kind of clock synchronizing method based on AFDX network, interchanger is to terminal broadcast synchronization request；Terminal, which will receive after synchronization request, to be replied message by the modified local time information of clock jitter as synchronizing；Interchanger receive synchronize reply message after calculate separately clock jitter with each terminal；Then local clock and the clock jitter of each terminal clock are formed into a message, is broadcast to terminal；Terminal parses the clock jitter value of each terminal and is saved from message, is then compensated using clock jitter value when messaging between terminal.The present invention solve the problems, such as AFDX network can not accurately calculate data in a network transmission time this, thus for AFDX network improve data time integrality provide technical foundation, further enhance the safety of AFDX network.
Description
Technical field
The present invention relates to avionic full-duplex switched-type Ethernet (Avionics Full-duplex Switched
Ethernet Network, abbreviation AFDX) field, the synchronous method of each nodal clock in specifically a kind of synchronous AFDX network.
Background technique
AFDX network is a kind of aeronautical data exchange network based on IEEE802.3 ethernet technology, introduces virtual chain
The concept on road (Virtual Link, VL), has the characteristics that time determinability, is now widely used for the avionics system of large aircraft
In system.
Although AFDX network has certainty, but still causing network data frame transmission time to have in the presence of delay and competition can
It can exceed that the receivable time range of practical application.And AFDX network protocol itself does not have time management and synchronizing function, institute
It, also just can not be in network can not determine Actual Elapsed Time that data frame transmits in a network in network transmission process
Critical data provides the data transport service of high time integrality.When transmitting critical data under certain application scenarios, the time is complete
Whole property is the foundation of highly important judgement message integrity.So developing a kind of clock synchronizing method based on AFDX network
Just seem particularly critical.
Summary of the invention
Goal of the invention of the invention is to provide a kind of clock synchronizing method based on AFDX network, by institute in AFDX network
There is the network clocking of device node to synchronize, the message transmission delay reached after clock synchronizes between terminal and terminal can quilt
Accurate to calculate, the communication for providing different time integrity levels as the data transmitted in AFDX network provides time reference,
To improve the safety and integrality of critical data interaction.Meanwhile the time integrality for improving network can also help to improve
The trouble isolation serviceability of AFDX network.
Goal of the invention of the invention is achieved through the following technical solutions:
A kind of clock synchronizing method based on AFDX network, during each synchronizing cycle, synchronizing process be divided into
Under several steps:
Step 1. is synchronous to all terminal broadcasts being connected on this AFDX interchanger as the AFDX interchanger of main equipment
Request message, and record the timestamp for sending synchronization request message；
The clock jitter value that step 2. was received according to a upper synchronizing cycle as the terminal from equipment is to receiving synchronization request
The timestamp of local clock is modified when message, when terminal receives synchronization request message, when by receiving synchronization request message
Timestamp be sent to AFDX interchanger as synchronizing to reply message；
Step 3.AFDX interchanger receive it is each synchronize reply message after, according to send synchronization request message when timestamp
And each timestamp synchronized in replying message calculates main equipment and each clock jitter between equipment；
Step 4. by local clock and it is all form a clock jitter message from the clock jitter value of equipment, and when by this
Clock deviation message is broadcast to all terminals in network；
Step 5. terminal parses the clock jitter value of each terminal and saves from receiving clock jitter message, is receiving industry
When message of being engaged in, the clock jitter value for sending the terminal of service message and local clock jitter value are subtracted each other as clock compensation value
It compensates, to obtain service message in the correct time of network transmission；
Step 6. is come temporarily until next synchronizing cycle, and terminal is carried out using new local clock and AFDX interchanger
Synchronous communication.
The beneficial effects of the present invention are: the present invention is solved by providing the method for synchronizing time based on AFDX network
AFDX network can not accurately calculate data this problem of transmission time in a network, to improve the time of data for AFDX network
Integrality provides technical foundation, further enhances the safety of AFDX network.
Detailed description of the invention
Fig. 1 is the flow diagram of the clock synchronizing method based on AFDX network.
Fig. 2 is the description of test of the clock synchronizing method based on AFDX network.
Specific embodiment
The present invention is described in further detail with reference to the accompanying drawing.
AFDX network is divided into two parts by the present invention: main equipment and from equipment.In AFDX network, all-network terminal is logical
It crosses AFDX interchanger and carries out data interaction.Using AFDX interchanger as main equipment, remaining ordinary terminal is used as from setting the present embodiment
It is standby.
It is same that clock synchronizing method provided by the invention based on AFDX network carries out the time as unit of a synchronizing cycle
Step, as shown in Figure 1, synchronizing process is divided into the following steps during each synchronizing cycle:
Step 1. is synchronous to all terminal broadcasts being connected on this AFDX interchanger as the AFDX interchanger of main equipment
Request message, and record the timestamp for sending synchronization request message；
The clock jitter value that step 2. was received according to a upper synchronizing cycle as the terminal from equipment is to receiving synchronization request
The timestamp of local clock is modified when message, when terminal receives synchronization request message, when by receiving synchronization request message
Timestamp be sent to AFDX interchanger as synchronizing to reply message；
Step 3.AFDX interchanger receive it is each synchronize reply message after, according to send synchronization request message when timestamp
And each timestamp synchronized in replying message calculates main equipment and each clock jitter between equipment；
Step 4. by local clock and it is all form a clock jitter message from the clock jitter value of equipment, and when by this
Clock deviation message is broadcast to all terminals in network；
Step 5. terminal parses the clock jitter value of each terminal and saves from receiving clock jitter message, is receiving industry
When message of being engaged in, the clock jitter value for sending the terminal of service message and local clock jitter value are subtracted each other as clock compensation value
It compensates, to obtain service message in the correct time of network transmission；
Step 6. is come temporarily until next synchronizing cycle, and terminal is carried out using new local clock and AFDX interchanger
Synchronous communication.
Main equipment and it can judge whether terminal reaches synchronous regime by the threshold value of configurable clock generator deviation between equipment,
If main equipment and a certain are greater than threshold value from the clock jitter between equipment, then it is assumed that main equipment with from equipment not up to synchronous shape
State；Conversely, if clock jitter is less than threshold value, then it is assumed that main equipment with from equipment reach synchronous regime.To adapt to different networks
The threshold value of environment, clock jitter can guarantee that interchanger and terminal are in AFDX network according to real network environment set
Stablize synchronous regime.
In practical AFDX communication process, if the network clock synchronization method provided in through the invention reaches when synchronizing rear
Clock deviation is smaller, and caused deviation is negligible in communication process, then the time that data are sent in a network is to connect
Receive the difference of timestamp and sending time stamp；If synchronizing rear clock jitter can not ignore, the mode of compensation can be taken to calculate end
Clock jitter between end, compensation method are as follows:
It is assumed that receiving end is from equipment clock and main equipment clock tswClock jitter be Δ t1, transmitting terminal is from equipment clock
With main equipment clock tswClock jitter be Δ t2.Then receiving end is from equipment clock trecvWith the relationship of main equipment clock are as follows: trecv
=tsw+Δt1；Transmitting terminal is from equipment clock tsendWith the relationship of main equipment clock are as follows: tsend=tsw+Δt2.It is found that transmitting terminal from
Equipment and receiving end are from the clock jitter Δ t=t between equipmentrecv-tsend=Δ t1-Δt2.Learn transmitting terminal and receiving end from
Clock jitter between equipment, the difference that receiving end can stab the deviation compensation to sending time stamp from equipment with receiving time
In, to obtain data in the correct time of network transmission.
Above method the case where there is only an interchangers suitable for network.When there are two or more exchanges in network
When machine, there are cascade relationships between interchanger and interchanger.At this point, interchanger itself is other than as main equipment, two
Master-slave equipment is also classified between cascade interchanger, the communication between master-slave equipment and the synchronous communication in single switch network
Process is identical.By synchronous communication, the local zone time of two interchangers reaches synchronous regime after some time, at this point,
The ordinary terminal and interchanger being connected with two interchangers respectively reach synchronous regime, are also synchronous shape between two interchangers
State, at this point, whole network completes synchronizing process.
In order to which the method for synchronizing time based on AFDX network described to the present invention has further understanding and understanding, with one
A embodiment is further described AFDX method for synchronizing network time.
Network topology architecture schematic diagram in AFDX in embodiment is as shown in Figure 2.(this figure is only illustrated as an example, real
There may be one or more terminals to be connected on the same interchanger in internet topology)
There are an AFDX interchanger and three terminals in the present embodiment network, AFDX interchanger is used as synchronous main equipment,
Three terminals are synchronous from equipment.
In synchronizing process, for interchanger first to three terminal broadcast synchronization request messages, three terminals receive synchronization request
It is used as to synchronize by the modified local time information of clock jitter to transmission respectively after message and reply message.Interchanger receives three
Synchronizing for terminal replies message, and calculates separately the clock jitter with three terminals, then by local clock and three terminal clocks
Clock jitter form a message, be broadcast to three terminals.Three terminals parsed from message three clock jitter values into
Row saves, and is then compensated using clock jitter value when messaging between terminal.For example, if terminal 1 sends AFDX message
To terminal 2, terminal 2 subtracts each other the clock jitter value of the terminal 1 received in synchronizing process and terminal 2 as compensation in reception message
To AFDX message, transmission time compensates value in a network.Meanwhile the clock jitter that three terminals save is also used for next
The local time stamp in replying message that synchronizes that terminal is sent in a synchronizing cycle is modified.
It, can according to the technique and scheme of the present invention and its hair it is understood that for those of ordinary skills
Bright design is subject to equivalent substitution or change, and all these changes or replacement all should belong to the guarantor of appended claims of the invention
Protect range.
Claims (1)
1. a kind of clock synchronizing method based on AFDX network, during each synchronizing cycle, synchronizing process is divided into following
Several steps:
Step 1. as main equipment AFDX interchanger to all terminal broadcast synchronization requests being connected on this AFDX interchanger
Message, and record the timestamp for sending synchronization request message；
The clock jitter value that step 2. was received according to a upper synchronizing cycle as the terminal from equipment is to receiving synchronization request message
When local clock timestamp be modified, when terminal receives synchronization request message, when will receive synchronization request message when
Between stamp be sent to AFDX interchanger as synchronizing to reply message；
Step 3.AFDX interchanger receive it is each synchronize reply message after, according to timestamp when sending synchronization request message and each
It synchronizes the timestamp in replying message and calculates main equipment and each clock jitter between equipment；
Step 4. by local clock and it is all form a clock jitter message from the clock jitter value of equipment, and it is the clock is inclined
Poor message is broadcast to all terminals in network；
Step 5. terminal parses the clock jitter value of each terminal and saves from receiving clock jitter message, disappears in reception business
When breath, the clock jitter value for sending the terminal of service message and local clock jitter value are subtracted each other and carried out as clock compensation value
Compensation, to obtain service message in the correct time of network transmission；
Step 6. is come temporarily until next synchronizing cycle, and terminal is synchronized using new local clock with AFDX interchanger
Communication.
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| CN201910228060.1A CN109842456A (en) | 2019-03-25 | 2019-03-25 | A kind of clock synchronizing method based on AFDX network |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112073981A (en) * | 2020-08-27 | 2020-12-11 | 中国航空无线电电子研究所 | Network system integrating uTTE and uAFDX communication modes |
| CN113497663A (en) * | 2021-05-28 | 2021-10-12 | 中国航空工业集团公司沈阳飞机设计研究所 | Distributed network architecture and time synchronization method thereof |
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| CN103684730A (en) * | 2012-09-07 | 2014-03-26 | 北京旋极信息技术股份有限公司 | Time synchronization method |
| US8817622B1 (en) * | 2012-06-26 | 2014-08-26 | Rockwell Collins, Inc. | Data network with aggregate flow monitoring |
| CN105680975A (en) * | 2016-03-07 | 2016-06-15 | 浙江大学 | Time synchronization method of master-slave structure multi-node network |
| CN107046450A (en) * | 2015-11-05 | 2017-08-15 | 罗伯特·博世有限公司 | Clock Simultaneous Monitoring in network based on Ethernet |
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2019
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8817622B1 (en) * | 2012-06-26 | 2014-08-26 | Rockwell Collins, Inc. | Data network with aggregate flow monitoring |
| CN103684730A (en) * | 2012-09-07 | 2014-03-26 | 北京旋极信息技术股份有限公司 | Time synchronization method |
| CN107046450A (en) * | 2015-11-05 | 2017-08-15 | 罗伯特·博世有限公司 | Clock Simultaneous Monitoring in network based on Ethernet |
| CN105680975A (en) * | 2016-03-07 | 2016-06-15 | 浙江大学 | Time synchronization method of master-slave structure multi-node network |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112073981A (en) * | 2020-08-27 | 2020-12-11 | 中国航空无线电电子研究所 | Network system integrating uTTE and uAFDX communication modes |
| CN112073981B (en) * | 2020-08-27 | 2023-12-22 | 中国航空无线电电子研究所 | Network system integrating uTTE and uAFDX communication modes |
| CN113497663A (en) * | 2021-05-28 | 2021-10-12 | 中国航空工业集团公司沈阳飞机设计研究所 | Distributed network architecture and time synchronization method thereof |
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Application publication date: 20190604 |