CN112187605B - Method for calculating PROFIBUS-DPV0 bus load rate - Google Patents
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04L47/00—Traffic control in data switching networks
- H04L47/10—Flow control; Congestion control
- H04L47/215—Flow control; Congestion control using token-bucket
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- 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
- H04L12/40006—Architecture of a communication node
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L47/00—Traffic control in data switching networks
- H04L47/10—Flow control; Congestion control
- H04L47/13—Flow control; Congestion control in a LAN segment, e.g. ring or bus
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Abstract
The invention discloses a method for calculating the load rate of a PROFIBUS-DPV0 bus, which comprises the following steps: calculating the byte quantity of the data link layer according to the type of the state message of the data link layer; calculating the byte quantity of the data exchange message according to the type of the data exchange message; calculating the byte quantity of the token message according to the type of the token message; calculating the average load rate by the accumulated sum of the byte quantities of the 3 messages; calculating the highest load rate according to the communication rate of the bus in a certain period of time; and calculating the PROFIBUS-DPV0 bus load rate of the whole network segment according to the ratio of the average load rate to the highest load rate. The calculation method of the invention comprises the bus load occupied by the transmission of the PROFIBUS-DPV0 data exchange message, and also comprises the bus load occupied by the transmission of the data link layer state message and the token message, and the calculation accuracy is high.
Description
Technical Field
The invention relates to the technical field of power plant Process field bus cycle data communication (Process Fieldbus-DPV0, PROFIBUS-DPV0 for short) network communication, in particular to a method for calculating the load rate of a PROFIBUS-DPV0 bus.
Background
PROFIBUS-DP (centralized peripheral) generally refers to data exchange between distributed peripherals (Devices) and a master station (DCS or PLC, etc.), which communicates with distributed field Devices (remote I/O, actuators, drivers, or lower networks, etc.) via standard PROFIBUS-DP dedicated cables and controls data exchange. PROFIBUS-DPV0 is the most basic DP version, defining cyclic data communication between master and slave stations of class 1. All data exchange is carried out according to a fixed time interval period, and the class 1 Master station (Master) circularly reads Input information of a slave station (slave) and circularly sends related Output information Output to the slave station. In summary, the PROFIBUS-DPV0 bus load rate is an important measure of the communication quality of field bus cycle data in a power plant process.
The PROFIBUS-DPV0 message mainly comprises diagnosis, parameterization, configuration, data exchange and other messages. The parameterized messages mainly specify the relationship between the master station and the slave station and specify the operation mode of the slave station, and mainly comprise communication parameters, function setting, device parameters, ID numbers and the like, and the messages are automatically generated during configuration. When the abnormality occurs, the PPROFIBUS-DP provides a convenient and powerful diagnostic information message so as to analyze the fault. Data exchange messages are the most used of all messages, since the only transfer between the master and slave is the transfer of data exchange messages for the majority of the time. The PROFIBUS-DPV0 bus load rate mainly comprises link layer state messages, data exchange messages and token message type 3 message load rates, wherein the link layer state messages are composed of diagnosis, parameterization and configuration.
Patent document 1 (publication No. CN 102111286A: published: 2011 6/29) discloses a method for monitoring the operation state of the whole network in a network structure of a control local area network, in which a network management node calculates the network load in a time period according to the number of data frames sent by each node; the network load is calculated by the following formula: the network load (the number of bits per frame data x the sum of the number of data frames sent by all network nodes in N time periods)/(N x time period x bus standard bit rate), however, this calculation method does not involve the bus load occupied by the transmission of PROFIBUS-DPV0 link layer status messages, data exchange messages and token message type 3 messages.
Disclosure of Invention
In view of the above technical problems, an object of the present invention is to provide a method for calculating a bus load rate of PROFIBUS-DPV0, where the method includes a bus load occupied by transmission of a PROFIBUS-DPV0 data exchange packet, and also includes a bus load occupied by transmission of a data link layer status packet and a token packet.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for calculating the load rate of a PROFIBUS-DPV0 bus comprises the steps of calculating the byte quantity of three messages, namely a data link layer state message, a data exchange message and a token message, on a PROFIBUS-DPV0 bus segment respectively; calculating the average load rate by the accumulated sum of the byte quantities of the three messages; calculating the highest load rate according to the communication rate of the bus in a certain period of time; finally, calculating the PROFIBUS-DPV0 bus load rate of the whole network segment according to the ratio of the average load rate to the highest load rate; the calculation of the PROFIBUS-DPV0 bus load rate of each network segment comprises the following steps:
s100: calculating the byte quantity of the status messages of the PROFIBUS-DPV0 data link layer according to the number of the status messages of the data link layer;
s200: calculating the byte quantity of the PROFIBUS-DPV0 data exchange messages according to the number of the data exchange messages;
s300: calculating the byte quantity of the PROFIBUS-DPV0 token message according to the number of the token messages;
s400: acquiring the actual byte quantity on the bus in a certain period of time by using a PROFIBUS message recording instrument, and calculating the average load rate of PROFIBUS-DPV0 through the accumulated sum of the byte quantities;
s500: calculating the highest load rate of PROFIBUS-DPV0 according to the bus communication rate in a certain period of time;
s600: and calculating the PROFIBUS-DPV0 bus load rate of each network segment according to the ratio of the average load rate to the highest load rate.
The byte quantity of the PROFIBUS-DPV0 data link layer state message is calculated based on the following formula (1):
BSD1＝u×6 (1)
wherein, BSD1Is the byte quantity of the PROFIBUS-DPV0 data link layer state message, and u indicates the number of the data link layer state messages.
The byte amount of the PROFIBUS-DPV0 data exchange message is calculated based on the following formula (2):
wherein, there is n on DP bus1,n2,…nkK slave stations, the I/O byte of each slave station is I1、O1，I2、O2,…Ik、Ok；BSD2The data exchange message byte quantity of PROFIBUS-DPV0 is that the master station repeatedly visits all the slave stations in sequence; y is the number of the global control messages; and in a certain period of time t, the master station repeatedly visits all the slave stations p times in sequence, and the number of the global control messages is y.
The byte quantity of the token message of the PROFIBUS-DPV0 is calculated based on the following formula (3):
BSD4＝l×3 (3)
wherein, BSD4The byte quantity of the token message of PROFIBUS-DPV0 and the number of the instruction board messages.
The method comprises the following steps of obtaining the actual byte quantity on a bus in a certain period of time by using a PROFIBUS message recording instrument, and calculating the average load rate B of PROFIBUS-DPV0 based on the following formula (4) through the accumulated sum of the byte quantities:
B＝BSD1+BSD2+BSD4 (4)。
the maximum load rate of the PROFIBUS-DPV0 is calculated based on the following equation (5):
wherein t refers to a certain period of time, and K refers to the bus communication rate on a certain network segment.
The PROFIBUS-DPV0 bus load rate of each network segment is calculated based on the following formula (6):
wherein β is the PROFIBUS-DPV0 bus load rate for each segment.
The prior art has no method for directly calculating the load rate of the PROFIBUS-DPV0 bus. The method for calculating the bus load rate of the PROFIBUS-DPV0, provided by the invention, not only comprises the bus load occupied by the transmission of the PROFIBUS-DPV0 data exchange messages, but also comprises the bus load occupied by the transmission of the data link layer state messages and the token messages, and has high calculation accuracy. In addition, the calculation method is suitable for PROFIBUS-DPV0 network communication of any power plant DCS control system, and is strong in universality. Through practical verification, the calculation result of the load rate of the PROFIBUS-DPV0 bus obtained by the calculation method meets the specification of the load rate of the data communication bus in the test procedure DL/T659-2016 of the distributed control system of the thermal power plant in the section 6.9.2: under busy working conditions, the load rate of the data communication bus is not more than 30%, and the practical verification effect is obvious.
Drawings
FIG. 1 is a flow chart of a method for calculating the bus load factor of PROFIBUS-DPV0 according to the present invention.
Fig. 2 is a frame structure diagram of the PROFIBUS data link layer.
FIG. 3 is a frame format diagram of the PROFIBUS-DPV0 data link layer.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific examples.
The method for calculating the PROFIBUS-DPV0 bus load rate is used for calculating the PROFIBUS-DPV0 bus load rate of each network segment in the PROFIBUS-DPV0 network so as to evaluate whether the network division of the PROFIBUS-DPV0 network of the power plant is reasonable or not. An actual PROFIBUS-DPV0 network may include multiple network segments, each of which may include 1 master node and multiple slave nodes, where the master node sequentially sends request messages to the slave nodes and receives response messages from the slave nodes.
As shown in fig. 1, the method for calculating the bus load rate of the PROFIBUS-DPV0 of each network segment in the PROFIBUS-DPV0 network provided by the invention comprises the following steps:
s100: calculating the quantity of bytes of the status report of the PROFIBUS-DPV0 data link layer according to the quantity of the status report of the data link layer;
s200: calculating the byte quantity of the PROFIBUS-DPV0 data exchange message according to the type of the data exchange message;
s300: calculating the byte quantity of the PROFIBUS-DPV0 token message according to the number of the token messages;
s400: acquiring the actual byte quantity on the bus in a certain period of time by using a PROFIBUS message recording instrument, and calculating the average load rate of PROFIBUS-DPV0 through the accumulated sum of the byte quantities;
s500: calculating the highest load rate of PROFIBUS-DPV0 according to the communication rate of the bus in a certain period of time;
s600: and calculating the PROFIBUS-DPV0 bus load rate of each network segment according to the ratio of the average load rate to the highest load rate.
The above steps of the present invention will be described in detail with reference to fig. 2 and 3.
S100: and calculating the byte quantity of the data link layer according to the type of the state message of the data link layer.
According to the characteristic of the format of the data link layer status message frame SD1 in fig. 2, the start delimiter SD occupies 1 byte, the data unit includes 3 bytes in total of the destination address DA, the source address SA and the function code FC, the frame check sequence FCs occupies 1 byte, and the trailer ED occupies 1 byte, so the data link layer status message frame SD1 amounts to 6 bytes. When the number of the data link layer status messages is detected to be u by the message recording instrument, the byte quantity of the data link layer status message SD1 is
BSD1＝u×6
S200: calculating the byte quantity of the data exchange message according to the type of the data exchange message;
according to the characteristic of the format of the data exchange message frame SD2 in FIG. 2, the start delimiter SD occupies 1 byte and has the data lengthLE takes 1 byte, data length repetition LEr takes 1 byte, start delimiter repetition SDr takes 1 byte, the data unit includes destination address DA, source address SA, 3 bytes of function code FC plus input and output bytes of the slave node, frame check sequence FCs takes 1 byte, tail ED takes 1 byte, so the data exchange packet frame consists of 9 bytes, input and output bytes of the slave node, and a global control packet of length 13 bytes. When passing through the message recording instrument, n is detected on the DP bus1,n2,…nkThe k slave nodes have I/O bytes corresponding to each slave node1、O1，I2、O2,…Ik、Ok. And in a certain period of time t, the master equipment node repeatedly visits all the slave stations for p times in sequence. If the number of the global control messages is y, the byte amount of the data exchange SD2 message is
S300: calculating the byte quantity of the token message according to the type of the token message;
according to the feature of the format of the token message frame SD4 in fig. 2, the start delimiter SD occupies 1 byte, and the data unit includes 2 bytes in total including the destination address DA and the source address SA, so that the token message frame amounts to 3 bytes. When the number of the token messages is detected to be l by the message recording instrument, the byte quantity of the token message SD4 is
BSD4＝l×3
S400: acquiring the actual byte quantity on the bus in a certain period of time by using a special PROFIBUS message recording instrument, and calculating the average load rate by the accumulated sum of the byte quantities;
the average load rate of the PROFIBUS-DPV0 is determined based on the following equation (4):
B＝BSD1+BSD2+BSD4 (4)
s500: calculating the highest load rate according to the bus communication rate in a certain period of time;
data from FIG. 3The frame structure, 1 data frame, consists of 11 bits in total of 1 start bit ST, 8 data bits, 1 parity bit and 1 stop bit SP. When the communication rate of the bus segment is K, 1 bit time is
The time occupied by 1 data frame is
For a certain time t, the theoretical amount of bytes is determined based on the following equation (5):
s600: and calculating the PROFIBUS-DPV0 bus load rate of each network segment according to the ratio of the average load rate to the highest load rate.
The PROFIBUS-DPV0 bus load rate is determined based on the following equation (6):
wherein, beta is the PROFIBUS-DPV0 bus load rate of the network segment, BSD1Is the data link layer status message byte quantity, BSD2Is the amount of bytes of the data exchange message, BSD4Is the token message byte quantity, t is the time, and K is the bus communication rate on a certain network segment.
[ examples ]
The network segment communication rate in this embodiment is 500Kbit/s, and includes 1 PROFIBUS-DPV0 master node and 16 PROFIBUS-DPV0 slave nodes, the input/output (I/O) byte amount of each slave node is 11 bytes, and the recording time t is 10 s. The corresponding SD2 message byte amount in a master-slave polling time is shown in Table 1.
When the special PROFIBUS message recording instrument is used, the byte amount of the data link layer state message SD1 is B when the number of the data link layer state messages detected is 1669SD1＝6×1669＝10014
TABLE 1
Corresponding SD2 message byte amount in master-slave polling time
When the number of the token messages is 13302, the byte amount of the token message SD4 is BSD4Average load factor B of 39906-3 × 13302-BSD1+BSD2+BSD4＝10014+70385+39906＝120305
Maximum load factor
When the rate K is 500Kbit/s, the bus load rate is:
the foregoing is a preferred embodiment of the present invention, and it should be noted that it is obvious to those skilled in the art that various modifications can be made without departing from the principle of the present invention, and these modifications should be construed as the protection scope of the present invention.
Claims (1)
1. A method for calculating the bus load rate of PROFIBUS-DPV0 is characterized by comprising the following steps: respectively calculating byte quantities of a data link layer state message, a data exchange message and a token message on a PROFIBUS-DPV0 bus segment; calculating the average load rate by the accumulated sum of the byte quantities of the three messages; calculating the highest load rate according to the communication rate of the bus in a certain period of time; finally, calculating the PROFIBUS-DPV0 bus load rate of the whole network segment according to the ratio of the average load rate to the highest load rate; the calculation of the PROFIBUS-DPV0 bus load rate of each network segment comprises the following steps:
s100: calculating the byte quantity of the status messages of the PROFIBUS-DPV0 data link layer by adopting a formula (1) according to the number of the status messages of the data link layer;
BSD1＝u×6 (1)
wherein, BSD1The byte quantity of the status messages of the PROFIBUS-DPV0 data link layer is U, and the number of the status messages of the data link layer is indicated by u;
s200: calculating the byte quantity of the PROFIBUS-DPV0 data exchange messages by adopting a formula (2) according to the number of the data exchange messages;
wherein, there is n on DP bus1,n2,…nkK slave stations, the I/O byte of each slave station is I1、O1，I2、O2,…Ik、Ok；BSD2The data exchange message byte quantity of PROFIBUS-DPV0 is that the master station repeatedly visits all the slave stations in sequence; y is the number of the global control messages; in a certain period of time t, the master station repeatedly visits all the slave stations p times in sequence, and the number of the global control messages is y;
s300: calculating the byte quantity of the PROFIBUS-DPV0 token message by adopting a formula (3) according to the number of the token messages;
BSD4＝l×3 (3)
wherein, BSD4The byte quantity of the PROFIBUS-DPV0 token message, and the number of the instruction board messages;
s400: acquiring the actual byte quantity on the bus in a certain period of time by using a PROFIBUS message recording instrument, and calculating the average load rate B of PROFIBUS-DPV0 by adopting a formula (4) through the accumulated sum of the byte quantities;
B＝BSD1+BSD2+BSD4 (4)
s500: calculating the highest load rate of PROFIBUS-DPV0 by a formula (5) according to a certain period of time and bus communication speed;
wherein t refers to a certain period of time, and K refers to the bus communication rate on a certain network segment;
s600: calculating the PROFIBUS-DPV0 bus load rate of each network segment according to the ratio of the average load rate to the highest load rate, which is shown in a formula (6);
wherein β is the PROFIBUS-DPV0 bus load rate for each segment.
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