CN106992879A - A kind of computational methods of CAN load factor - Google Patents
A kind of computational methods of CAN load factor Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
- H04L41/14—Network analysis or design
- H04L41/142—Network analysis or design using statistical or mathematical methods
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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
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
- H04L41/14—Network analysis or design
- H04L41/145—Network analysis or design involving simulating, designing, planning or modelling of a network
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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
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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
- H04L2012/40267—Bus for use in transportation systems
- H04L2012/40273—Bus for use in transportation systems the transportation system being a vehicle
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Abstract
The invention discloses a kind of CAN load factor, including：Judge the type of each CAN message, and determine therefrom that the length of each potential field in CAN message data frame；The length of each potential field in CAN message data frame based on determination, determines each CAN message data flow length；Emulate each CAN message filling bit length；The CAN message filling bit length of CAN message data flow length and calculating based on determination transmits bit stream length to determine that each CAN message is actual；Judge each CAN message transmission types, and determine therefrom that the value in the transmission cycle of CAN message；Different modes is selected according to each CAN message length to determine the total inorganic nitrogen of each CAN message occupancy；The total inorganic nitrogen that each CAN message takes in the network segment is summed, to draw the CAN load factor of the whole network segment.The computational methods of the present invention are the bus load taken comprising CAN message data stream transmitting, and comprising the shared bus load of filler transmission, the accuracy of calculating is high.
Description
Technical field
Patent of the present invention is related to automobile controller LAN (Controller Area Network, abbreviation CAN) network and led to
Believe technical field, and in particular to a kind of computational methods of CAN load factor.
Background technology
With car networking, vehicle intellectualized development, the electric system applied on automobile increasingly increases.With
Transinformation content increases in CAN network, and total inorganic nitrogen is dramatically increased, when total inorganic nitrogen is too high, will cause priority
Low message transmissions time delay is long, in addition occur lose message situation, it is bad in network communications environment, for example once in a while by
During to electromagnetic interference, because erroneous frame increases and causes the risk of network blockage to significantly increase.So now must be by the CAN nets
Network is divided into multiple subnets.If however, subnet is designed to that excessively, the cost per unit of gateway will be increased, and information passes through net
Extra message transmissions time delay will be brought when closing forwarding.To sum up, CAN network total inorganic nitrogen is vehicle Network Topology Design
Important restrictions condition.
It is well known that network topology belongs to conceptual phase, it is the basis of follow-up all-network design.If network is opened up
Flutter design unreasonable, changed in vehicle development later stage network topology, then network service matrix design, each ECU can be brought to lead to
Believe the great variety of the work such as Software for Design, or even do over again completely, so Network Topology Design must make every effort to accurate, and CAN nets
The risk of the more high then project later stage change network topology of the accuracy that network total inorganic nitrogen is calculated is smaller.
Bit stream in CAN communication message is encoded using non-return-to-zero (NRZ) method.I.e. in the whole position time, bit level will
It is " dominant ", otherwise it is " recessiveness ".The characteristics of this coding is to realize that simple and expense is low, and it has the disadvantage to work as continued presence
During multiple identical informations, because synchronizing information is lacked clocking error will be caused to accumulate.CAN message is defined for this ISO 11898
Frame starting (SOF), the method filled by position of arbitration field, controlling filed, data fields and CRC sequence encodes.No matter
When, it is just automatic that a complement code is inserted in bit stream as long as CAN transmitters detect the position for having 5 continuous discre values in bit stream
Position.When there is more continuous discre value in CAN message data flow, bit stream is actually transmitted in CAN network after message filling
Digit it is more than the digit of CAN message data flow, the bus load that takes also increases when message is transmitted.
(the publication number of patent document 1：CN102111286A；Publication date：On June 29th, 2011) one kind is disclosed in control office
Management node is according to each node in the method that the running status of whole network is monitored in the net network structure of domain, the computational methods
The data frame number of transmission calculates the network load in a time cycle；The network load is calculated by below equation
Arrive：Network load=(the data frame number that is sent within N number of time cycle of digit × all-network node per frame data it
With)/(N × time cycle × bus standard bit rate), but the computational methods are not involved with CAN message data stream transmitting
When, the shared bus load of filler transmission.
(the name of document of non-patent literature 1：Commercial car CAN network total inorganic nitrogen forecasting research based on mathematical statistics, comes
From the Chinese automobile Engineering society nd Annual Meeting collection ＞ of ＜ 2016) and (name of document of non-patent literature 2：Offroad vehicle CAN network bus
Load factor simulation study, from ＜ offroad vehicle technology branch Annual Conference collection of thesis ＞ in 2016) CAN load can be achieved
The prediction of rate, and consider during prediction the shared bus load of filler transmission.However, the institute of non-patent literature 1
State method analysis sample come from the existing 5 sections of different brands of in the market commercial car product CAN network random test
Data, it, which analyzes sample, has certain limitation, i.e., for the commercial car for the 5 sections of brands chosen, and this method predicts the outcome
Deviation between measured result is smaller, and for other brands commercial car, this method predict the outcome with measured result it
Between deviation can increased.Non-patent literature 2 is using CAN network simulation software CANoe to the total of offroad vehicle CAN network message
Linear load rate has carried out full digital trigger technique research, and its simulation object is certain specific defined network topology of vehicle and communication square
Battle array.Need to re-establish full digital trigger technique model when simulation object changes, i.e., the emulation mode is with strong points, versatility is
It is not enough.
The content of the invention
For above-mentioned technical problem, the present invention provides a kind of computational methods of CAN load factor, and the computational methods are bag
The bus load that data stream transmitting containing CAN message takes, and include the shared bus load of filler transmission.
The technical solution adopted by the present invention is：
Embodiments of the invention provide a kind of computational methods of CAN load factor, for each net in CAN network
The total inorganic nitrogen of section is calculated, and the calculating of the total inorganic nitrogen of each network segment comprises the following steps：
S100：Judge the type of each CAN message in the network segment, and determine therefrom that the length of each potential field in CAN message data frame；
S200：The length of each potential field in CAN message data frame based on determination, determines each CAN message data flow length；
S300：Emulate the filling bit length of each CAN message；
S400：The CAN message filler determined based on the step S200 CAN message data flow length determined and step S300
Length transmits bit stream length to determine that each CAN message is actual；S500：Judge each CAN message transmission types, and determine therefrom that CAN
The value in the transmission cycle of message；
S600：Different modes is selected according to each CAN message length to determine the total inorganic nitrogen of each CAN message occupancy；
S700：The total inorganic nitrogen that each CAN message takes in the network segment is summed, to show that the CAN of the whole network segment is total
Linear load rate.
Alternatively, each CAN message data flow length is determined based on following formula (1)：
Wherein, LmFor CAN message data flow length, unit is position；LiFor i-th of potential field length of CAN message data frame,
Unit is bit；
The actual transmission bit stream length of each CAN message is determined by following formula (2)：
#L=Lm+Lstuff (2)
Wherein, L is the length of the actual transmission bit stream of CAN message, and unit is bit；LstuffFor the length of CAN message filler
Degree, unit is bit.
Alternatively, the emulation of the filling bit length of each CAN message is comprised the following steps in step S300：
S301：The potential field of CAN message frame in the communication matrix file of the network segment, which is defined, to form CAN message data flow simultaneously
It is stored in two-dimensional array MEG1；
S302：CAN message data flow fill rule as defined in CAN protocol in MEG1 is filled to form CAN reports
Text filling bit stream is simultaneously stored in 2-D data MEG2；
S303：The CAN message data flow length for subtracting MEG1 with MEG2 CAN message filling bit stream length tries to achieve CAN reports
Text filling bit length.
Alternatively, step S301 is specifically included：
(1) SOF, SRR, IDE, RTR, R0, R1 for taking the fixed position information that begins in CAN message frame are added into empty CAN to report
In literary data flow；
(2) CAN that the ID and DLC of message are read from the communication matrix file of the network segment and is added after being handled through step (1)
In message data stream；
(3) the defined signal in CAN message data fields chooses random number from its span, and reserved bit is defined as
1, and related content is added in the CAN message data flow after being handled through step (2)；
(4) CRC sequences are calculated according to CRC algorithm and added in the CAN message data flow after being handled through step (3).
Alternatively, the operation (1) in step S301 is repeated to (4) 1000 times, to form 1000 emulation CAN messages
Data flow；
In step S303, to the filler of 1000 CAN messages obtained by 1000 emulation CAN message data flows
The mathematic expectaion of the emulation data of length is solved, using solving result as the CAN message of emulation filling bit length.
Alternatively, step S500 is specifically included：
S501：If certain CAN message transmission types is preiodic type, cycle C that sends of the CAN message is equal to the message
The transmission cycle；
S502：If certain CAN message transmission types is event mode, the CAN message sends cycle C and takes 1s；
S503：If certain CAN message transmission types is preiodic type after event, the transmission cycle C of the CAN message is equal to should
The transmission cycle of CAN message；
S504：If certain CAN message transmission types is cycle+event mode, the transmission cycle C of the CAN message is by following
Formula (3) is determined：
Wherein, C is the transmission cycle of CAN message, and unit is s, c1For the transmission of the CAN message defined in communication matrix
Cycle, unit is s, c2In transmission cycle when being sent for the CAN message because of event generation, estimated by 1s.
Alternatively, step S600 is specifically included：
When CAN message length is less than or equal to 8 byte, determine that the bus that CAN message takes is born using following formula (4)
Load rate：
Wherein, Busload is the total inorganic nitrogen of CAN message, and Baud is CAN network traffic rate, and unit is bit/s, L
For the length of the actual transmission bit stream of CAN message, unit is bit, and C is the transmission cycle of CAN message, and unit is s；
When CAN message length is more than 8 byte, the bus load that CAN message takes is determined using following formula (5)
Rate：
Wherein, Busload is the total inorganic nitrogen of CAN message, and Baud is CAN network traffic rate, and unit is bit/s,
ML is CAN message length, and unit is byte, and lg is the length of the actual transmission bit stream of the CAN network single frames message of 8 bytes, list
Position is bit, and C is the transmission cycle of CAN message, and unit is s.
Alternatively, the CAN load factor of the whole network segment is determined based on following formula (6)：
Wherein, Busload (T) is the CAN load factor of the whole network segment, BusloadiFor i-th report of the whole network segment
The CAN load factor of text, n is the quantity of the CAN message of the whole network segment.
Prior art generally have ignored the shared bus load of filler transmission when calculating CAN load factor, lead
Cause there is larger deviation between CAN load factor result of calculation and measured result, add project development later stage network and set
Count the event risk and cost risk of change tape.A small number of CAN load factor computational methods are although it is contemplated that filler transmission
Shared bus load, but its accuracy associates larger with specific vehicle, and versatility is not enough.The CAN that the present invention is provided
The computational methods of total inorganic nitrogen are the bus load taken comprising CAN message data stream transmitting, and transmit institute comprising filler
The bus load of occupancy, the accuracy of calculating is high.In addition, the CAN network that the computational methods are applied to any vehicle communicates, it is general
Property is strong.Verified by real vehicle, the deviation ＜ between the CAN load factor result of calculation and measured result of this computational methods ±
1%, network design quality is effectively improved, while reducing the development time, development cost is reduced, practical function is notable.
Brief description of the drawings
Fig. 1 is the flow chart of the computational methods of the CAN load factor of the present invention.
Fig. 2 is the schematic diagram of CAN standard frame formats.
Fig. 3 is the schematic diagram of CAN Extended Superframe Formats.
Fig. 4 is CAN message position filling exemplary plot.
Fig. 5 is that CAN message fills bit length simulated program flow chart.
Fig. 6 transmits exemplary plot for the CAN long messages of target complete address connection management.
Embodiment
To make the technical problem to be solved in the present invention, technical scheme and advantage clearer, below in conjunction with accompanying drawing and tool
Body embodiment is described in detail.
The computational methods for the CAN load factor that the present invention is provided are used to bear the bus of each network segment in CAN network
Load rate is calculated, and whether reasonable divides to assess the CAN network segments of vehicle.The CAN network segments number of vehicle determined based on vehicle,
Generally 1-10, depending on the traffic between the quantity and each ECU of ECU in the vehicle.Each network segment has different names
Claim, such as power CAN, chassis CAN, comfortable CAN.The CAN network of each vehicle can include multiple network segments, and each network segment can be with
Including multiple nodes, each node can send a plurality of message, can also receive message from other nodes.
As shown in figure 1, the method calculated the total inorganic nitrogen of each network segment in CAN network that the present invention is provided
It may include following steps：
S100：Judge the type of each CAN message in the network segment, and determine therefrom that the length of each potential field in CAN message data frame；
S200：The length of each potential field in CAN message data frame based on determination, determines each CAN message data flow length；
S300：Emulate the filling bit length of each CAN message；
S400：The CAN message filler determined based on the step S200 CAN message data flow length determined and step S300
Length transmits bit stream length to determine that each CAN message is actual；
S500：Judge each CAN message transmission types, and determine therefrom that the value in the transmission cycle of CAN message；
S600：Different modes is selected according to each CAN message length to determine the total inorganic nitrogen of each CAN message occupancy；
S700：The total inorganic nitrogen that each CAN message takes in the network segment is summed, to show that the CAN of the whole network segment is total
Linear load rate.
This above steps is described in detail below with reference to Fig. 2 to Fig. 6.
S100：Judge the type of each CAN message in the network segment, and determine therefrom that the length of each potential field in CAN message data frame
According to the difference of identifier field length, CAN message data frame is divided into two classes：Standard frame and extension frame.Two kinds of CAN reports
Literary data frame is comprising 7 predefined potential fields, respectively frame starting (SOF), arbitration field, controlling filed, data fields, cyclic redundancy
Verify field (CRC), response (ACK) and frame end (EOF).Two kinds of CAN message data frame formats only arbitrate field difference, other
All same.CAN standard frame formats are as shown in Fig. 2 CAN Extended Superframe Formats are as shown in Figure 3.
Every field length definition is shown in Table 1 in two kinds of CAN message data frames, and wherein data fields are by the transmission data in data frame
Composition, its length is determined by the data length code (DLC) in controlling filed, can be 0~8 byte, 8 are contained per byte
Position.
Every field length definition in 1 two kinds of CAN message data frames of table
S200：The length of each potential field in CAN message data frame based on determination, determines each CAN message data flow length
Each CAN message data flow length is determined based on following formula (1)：
Wherein, LmFor CAN message data flow length, unit is position；LiFor i-th of potential field length of CAN message data frame,
Unit is position, and value is defined referring to upper table 1.
S300：Emulate the filling bit length of each CAN message
Defined according to ISO 11898, frame starting (SOF), arbitration field, controlling filed, data fields and the cyclic redundancy of CAN message
The method that verification sequence is filled by position is encoded.No matter when, as long as CAN transmitters, which are detected in bit stream, 5 continuous identifications
The position of value, it is just automatic that a complementing bits is inserted in bit stream.Filling example in CAN message position is as shown in Figure 4.Intend the CAN reports of transmission
Literary data flow be 010000000000111110001111 (totally 24), then use position filling after bit stream for
010000010000011111010001111 (totally 27).
In the field encoded using position filling mode, the value of some is constant all the time, is shown in Table 2.
Constant in the potential field for the method coding that table 2 is filled using position
After the definition of the communication matrix of each network segment of CAN network is completed, identifier (ID), the data length code of each message
(DLC) reserved bit and in data fields is constant, only the defined signal in message data and CRC
(CRC) sequence is variable, and its data flow is different with transmission information difference.According to each network segment communicating matrix, obtained by emulation
Each message filling bit length is obtained, simulated program flow is as shown in Figure 5.Flow shown in Fig. 5 is the present invention to the CAN in certain network segment
The flow chart of the calculating of the total inorganic nitrogen of message.The total inorganic nitrogen of other network segments in CAN network may be based on shown in Fig. 5
The flow gone out is obtained.
As shown in figure 5, after opening the CAN communication matrix file of certain network segment, first counting the CAN message quantity that the network segment is defined
And be stored in after variable Nm, then the filling bit length of every message is tried to achieve one by one.
The beginning condition setting of emulation is I=1, and J=0, I is the I frame CAN messages in certain network segment, and J is simulation times.
I frame CAN message datastream functions are initially formed, the function of the function is：Defined according to the potential field of message frame
Form CAN message data flow and be stored in two-dimensional array MEG1, specifically include：
(1) by the empty CAN message number for taking the fixed position information (SOF, SRR, IDE, RTR, R0, R1) that begins to add initialization
According in stream.
(2) message ID and DLC and the CAN message data added after being handled through step (1) are read from communication matrix file
In stream.
(3) the defined signal in message data chooses random number from its span, and reserved bit is defined as 1,
And add related content in the CAN message data flow after being handled through step (2).The data fields definition of every message not phase
Together, the 1st byte of such as certain message data is engine speed, and 2-3 bytes are actual torque, and remaining byte is without fixed
Justice, then engine speed and actual torque are defined signal.
(4) CRC sequences are calculated according to CRC algorithm and added in the CAN message data flow after being handled through step (3).
By above-mentioned steps (1) to (4), the data flow of the CAN message can be formed.
To improve accuracy of simulation, 1000 emulation is carried out for every message, that is, has repeated above-mentioned steps (1) extremely
(4), after every progress is once emulated, J plus 1, that is, assigns J=J+1, then judges whether the J values after assignment again are more than
1000, simulated program is continued executing with if it is not greater, then returning, if it is greater, then forming I frames CAN message filling bit stream
Function, the function of the function is：CAN message data flow fill rule as defined in CAN protocol in MEG1 is filled shape
Bit stream is filled into CAN message and is stored in 2-D data MEG2.So, by 1000 emulation, 1000 emulation CAN can be formed
Message data stream.
I frames CAN message filling bit length subfunction is finally calculated, the function of the function is：Filled out with MEG2 CAN message
The CAN message data flow length that bit stream length subtracts MEG1 is filled, and solves the mathematic expectaion of 1000 emulation data and is used as the CAN
Message fills bit length.In this way, completing to fill the 1st frame CAN message in the network segment emulation of bit length, afterwards, I=is assigned
I+1, when I is less than Nm, continues simulation flow, to be emulated to every frame CAN message filling length in the network segment, when I is more than
During Nm, the network segment CAN communication matrix file is closed, terminates the emulation of the filling bit length to each CAN message of the network segment.
S400：The CAN message filler determined based on the step S200 CAN message data flow length determined and step S300 Length transmits bit stream length to determine that each CAN message is actual
Each actual transmission bit stream length of CAN message is determined by following formula (2)：
#L=Lm+Lstuff (2)
Wherein, L is the length of the actual transmission bit stream of CAN message, and unit is position；LmFor the length of CAN message data flow, list
Position is position (bit)；LstuffFor the length of CAN message filler, unit is position.
S500：Judge each CAN message transmission types, and determine therefrom that the value in transmission cycle C of CAN message
Conventional CAN message transmission types have 4 kinds, are respectively：Preiodic type and cycle+thing after preiodic type, event mode, event
Part type.
1) C is equal to the transmission cycle of the message if message transmission types are preiodic type.
If 2) message transmission types be event mode (including request when send and trigger when send two kinds), because event with
Function is defined related and occurred at random, it is difficult to prediction, and its transmission frequency is relatively low in advance, to CAN load effect
Less, so sending cycle C equal to empirically determined 1s calculating by message when calculating.
If 3) message transmission types are preiodic type after event, it is equal to the message by maximum computation of Period, the i.e. C of sending
The transmission cycle.
If 4) message transmission types are cycle+event mode, the calculating such as formula (3) in the transmission cycle (C) of CAN message
It is shown.
Wherein, C is the transmission cycle of CAN message, and unit is s, c1For the transmission of the CAN message defined in communication matrix
Cycle, unit is s, c2In transmission cycle when being sent for the CAN message because of event generation, estimated by 1s.
S600：Different modes is selected according to each CAN message length to determine the total inorganic nitrogen of each CAN message occupancy
(1) when CAN message length is less than or equal to 8 byte, it can be transmitted using single frames CAN message, single frames CAN message
Total inorganic nitrogen calculate as shown in formula (4).
Wherein, Busload is the total inorganic nitrogen of CAN message, and Baud is CAN network traffic rate, and unit is bit/s, L
For the length of the actual transmission bit stream of CAN message, unit is bit, and C is the transmission cycle of CAN message, and unit is s.
(2) when CAN message length is more than 8 byte, the referred to as long message of CAN network.Long message can not use a list
Only CAN data frames encapsulation, it is necessary to be split as several small packets, then passed one by one to it using single data frame
Send.And recipient allows for receiving these single data frames, then parse each packet and reformulate raw information.
Split into data fields of the single CAN data frame packets containing 8 bytes.Due to the single data of those reformulation long messages
Frame is had to be recognized one by one, can correctly recombinated, therefore the first byte of data fields is defined as sequence of data packet
Numbering, i.e., one CAN data frame can only at most transmit the raw information of 7 bytes.
In order to transmit a multipacket message, it is necessary to set up virtual link between sending node and receiving node.This is virtual
Connection management is divided into two kinds：Specify destination address connection and the connection of target complete address.Because the connection of target complete address is not required to
The management function of data traffic control and connection closed is provided, it is simple and easy to apply, so the extensive use in vehicle.
In the connection management of target complete address, if some node will broadcast a long message, it first has to transmission one
Bar air announcements message (TP.CM_BAM), which is used to set up, to be connected, and it is long that the message includes the numbering for the long message that will be broadcasted, message
Degree and the bag number that it is encapsulated by subpackage, the resource distributed accordingly so as to receiving node needed for reception message and reconstructed file.Then
Data transfer message (TP.DT) can be used to send the data of correlation.
CAN long messages transmission example is as shown in Figure 6 in the connection management of target complete address.Sending node, which is sent out, send parameter
Group # is 65260 message, and the message length is that 17 bytes are transmitted, it is necessary to be packed as 3 bags, then sends 1 first
TP.CM_BAM messages set up connection, then retransmit 3 packets that 3 TP.DT messages transmission are split, as transmit length
For the information of 17 bytes, need to send the CAN message that 4 length are 8 bytes altogether.
The present invention is calculated such as formula (5) institute using the total inorganic nitrogen of the CAN long messages of target complete address connection management
Show.
Wherein, Busload is the total inorganic nitrogen of CAN message, and Baud is CAN network traffic rate, and unit is bit/s,
ML is CAN message length, and unit is byte, and lg is the length of the actual transmission bit stream of the CAN network single frames message of 8 bytes, list
Position is bit, and C is the transmission cycle of CAN message, and unit is s.
S700：The total inorganic nitrogen that each CAN message takes in the network segment is summed, to show that the CAN of the whole network segment is total
Linear load rate
The CAN load factor of the whole network segment can be determined based on following formula (6)：
Wherein, Busload (T) is the CAN load factor of the whole network segment, BusloadiFor i-th report of the whole network segment
The CAN load factor of text, n is the quantity of the CAN message of the whole network segment.
【Embodiment】
Network segment communicating speed in the present embodiment is 250Kbit/s, and its CAN communication matrix is shown in Table 3, wherein each CAN message
Data fields content it is defined, without reserved bit.Wherein " S " represents to send, and " R " represents to receive.
The network segment CAN communication matrix of table 3
As shown in Table 3,3 messages, respectively M1, M2 and M3, the CAN of the network segment are had in the network segment of the present embodiment
The calculation procedure of load factor is as follows：
1. judging each CAN message type, and determine therefrom that every field length in CAN message data frame.
Message M1 is standard frame, and it is 12 that it, which arbitrates field,；Message M1 length is 6 bytes, and its data fields is 48.
Message M2 is extension frame, and it is 32 that it, which arbitrates field,；Message M2 length is 8 bytes, and its data fields is 64.
Message M3 is extension frame, and it is 32 that it, which arbitrates field,；Message M3 length is 30 bytes, because message length (30 byte)
More than 8 bytes, so needing to use host-host protocol to be split as some small packets, the length of each packet is 8 words
Section.For M3, this step calculates the length of the small data packets after splitting, and its data fields is 64.
The potential field length of each message is shown in Table 4 in the network segment of the present embodiment.
Each message potential field length in the network segment of table 4
2. calculate each CAN message data flow length.
Available, the message M1 data flow length L using above-mentioned formula (1)m=92；Message M2 data flow length Lm=
128；The data flow length L of small data packets after message M3 fractionationsm=128.
3. each CAN message filling bit length of emulation.
The emulation of bit length simulated program is filled according to above-mentioned steps S300 CAN message to try to achieve：Message M1 filling bit length
Spend Lstuff=13；Message M2 filling bit length Lstuff=19；The filling bit length L of TP messages after message M3 fractionationsstuff
It is worth for 20.
4. calculating the actual transmission bit stream length of each CAN message, the length is CAN message data flow length and filling bit length
Sum.
Available, the message M1 actual transmission bit stream length L=105 according to above-mentioned formula (2)；Message M2 actual transmission
Bit stream length L=147；The actual transmission bit stream length average of TP messages after message M3 fractionations is the CAN nets of 148, i.e. 8 bytes
The length lg=148 of the actual transmission bit stream of network single frames message.
5. judging each CAN message transmission types, and determine therefrom that the value in the transmission cycle (C) of CAN message.
Message M1 transmission types are event+preiodic type, and the transmission cycle of its CAN message is calculated using above-mentioned formula (3).Its
Middle C1=1000ms=1s, C2=1s,
Message M2 transmission types are preiodic type, then C=20ms=0.02s.
Message M3 transmission types are preiodic type after event, then C=100ms=0.1s.
6. different CAN load factor calculation formula are selected according to CAN message length.
Message M1 message length is less than or equal to 8 bytes, calculates its total inorganic nitrogen using above-mentioned formula (4), its bus
Load factor Bussload1For：
Message M2 message length is less than or equal to 8 bytes, calculates its total inorganic nitrogen using above-mentioned formula (4), its bus
Load factor Bussload2For：
Message M3 message length is more than 8 bytes, calculates its total inorganic nitrogen using above-mentioned formula (5), its bus load
Rate Bussload3For：
7. the total inorganic nitrogen summation that each CAN message takes in pair network segment, is loaded with the CAN for drawing the whole network segment
Rate.
Understood according to above-mentioned formula (6), the CAN load factor Bussload of the whole network segmentTFor message M1, M2 and M3
Total inorganic nitrogen sum, i.e. BussloadT=0.08%+2.87%+3.47%=6.42%.
Described above is the preferred embodiment of the present invention, it is noted that for those skilled in the art
For, on the premise of principle of the present invention is not departed from, some improvements and modifications can also be made, these improvements and modifications
It should be regarded as protection scope of the present invention.
Claims (8)
1. a kind of computational methods of CAN load factor, it is characterised in that for the bus to each network segment in CAN network
Load factor is calculated, and the calculating of the total inorganic nitrogen of each network segment comprises the following steps：
S100：Judge the type of each CAN message in the network segment, and determine therefrom that the length of each potential field in CAN message data frame；
S200：The length of each potential field in CAN message data frame based on determination, determines each CAN message data flow length；
S300：Emulate the filling bit length of each CAN message；
S400：Bit length is filled based on the step S200 CAN message data flow length determined and step the S300 CAN message determined
To determine the actual transmission bit stream length of each CAN message；
S500：Judge each CAN message transmission types, and determine therefrom that the value in the transmission cycle of CAN message；
S600：Different modes is selected according to each CAN message length to determine the total inorganic nitrogen of each CAN message occupancy；
S700：The total inorganic nitrogen that each CAN message takes in the network segment is summed, born with the CAN for drawing the whole network segment
Load rate.
2. the computational methods of CAN load factor according to claim 1, it is characterised in that each CAN message data
Length is flowed to determine based on following formula (1)：
Wherein, LmFor CAN message data flow length, unit is position；LiFor i-th of potential field length of CAN message data frame, unit
For bit；
The actual transmission bit stream length of each CAN message is determined by following formula (2)：
#L=Lm+Lstuff (2)
Wherein, L is the length of the actual transmission bit stream of CAN message, and unit is bit；LstuffFor the length of CAN message filler, list
Position is bit.
3. the computational methods of CAN load factor according to claim 2, it is characterised in that to each in step S300
The emulation of the filling bit length of CAN message comprises the following steps：
S301：The potential field of CAN message frame in the communication matrix file of the network segment defines to form CAN message data flow and store
In two-dimensional array MEG1；
S302：CAN message data flow fill rule as defined in CAN protocol in MEG1 is filled and to form CAN message and fills out
Fill bit stream and be stored in 2-D data MEG2；
S303：The CAN message data flow length for subtracting MEG1 with MEG2 CAN message filling bit stream length is tried to achieve CAN message and filled out
Fill bit length.
4. the computational methods of CAN load factor according to claim 3, it is characterised in that step S301 is specifically included：
(1) SOF, SRR, IDE, RTR, R0, R1 that the fixed position information that begins is taken in CAN message frame are added into empty CAN message number
According in stream；
(2) CAN message that the ID and DLC of message are read from the communication matrix file of the network segment and is added after being handled through step (1)
In data flow；
(3) the defined signal in CAN message data fields chooses random number from its span, and reserved bit is defined as 1, and
Related content is added in the CAN message data flow after being handled through step (2)；
(4) CRC sequences are calculated according to CRC algorithm and added in the CAN message data flow after being handled through step (3).
5. the computational methods of CAN load factor according to claim 4, it is characterised in that
The operation (1) in step S301 is repeated to (4) 1000 times, to form 1000 emulation CAN message data flows；
In step S303, to the filling bit length of 1000 CAN messages obtained by 1000 emulation CAN message data flows
The mathematic expectaions of emulation data solved, using solving result as the CAN message of emulation filling bit length.
6. the computational methods of CAN load factor according to claim 1, it is characterised in that step S500 is specifically included：
S501：If certain CAN message transmission types is preiodic type, transmission cycle C of the CAN message is equal to the transmission of the message
Cycle；
S502：If certain CAN message transmission types is event mode, the CAN message sends cycle C and takes 1s；
S503：If certain CAN message transmission types is preiodic type after event, the transmission cycle C of the CAN message is equal to the CAN
The transmission cycle of message；
S504：If certain CAN message transmission types is cycle+event mode, the transmission cycle C of the CAN message presses following formula
(3) determine：
Wherein, C is the transmission cycle of CAN message, and unit is s, c1For the transmission cycle of the CAN message defined in communication matrix,
Unit is s, c2In transmission cycle when being sent for the CAN message because of event generation, estimated by 1s.
7. the computational methods of CAN load factor according to claim 1, it is characterised in that step S600 is specifically included：
When CAN message length is less than or equal to 8 byte, the bus load that CAN message takes is determined using following formula (4)
Rate：
Wherein, Busload is the total inorganic nitrogen of CAN message, and Baud is CAN network traffic rate, and unit is bit/s, and L is
The length of the actual transmission bit stream of CAN message, unit is bit, and C is the transmission cycle of CAN message, and unit is s；
When CAN message length is more than 8 byte, the total inorganic nitrogen that CAN message takes is determined using following formula (5)：
Wherein, Busload is the total inorganic nitrogen of CAN message, and Baud is CAN network traffic rate, and unit is bit/s, and ML is
CAN message length, unit is byte, and lg is the length of the actual transmission bit stream of the CAN network single frames message of 8 bytes, and unit is
Bit, C are the transmission cycle of CAN message, and unit is s.
8. the computational methods of CAN load factor according to claim 7, it is characterised in that the CAN of the whole network segment
Load factor is determined based on following formula (6)：
Wherein, Busload (T) is the CAN load factor of the whole network segment, BusloadiFor i-th message of the whole network segment
CAN load factor, n is the quantity of the CAN message of the whole network segment.
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