Measurement and control network data transmission mode based on data flow

Abstract

The invention relates to a measurement and control network transmission mode based on data flow. The method is mainly applied to a measurement and control system, and data collected by the measurement and control system is classified into a plurality of data streams according to purposes or sources. And re-packaging and packaging the received data according to classification at the switching node of the transmission network, and then issuing the data at a preset frequency. And each access port of the switch selects a data packet related to subscription from the published data stream according to the data stream subscription of the access equipment, and sends the data packet to the access equipment, thereby completing data transmission. According to the invention, the mode that the traditional Ethernet carries out data packet exchange based on an IP address is changed, and a real-time data transmission channel between a data source and a data processing / recording node is established in a data stream mode. Data in one data stream can come from a plurality of data source nodes, and one data source node can also provide data for a plurality of data streams. Therefore, the data processing / recording node does not care about the source of the data any more, and only needs to reserve the data flow as required.

Description

Technical Field

[0001] The present invention belongs to the field of data communication, and specifically relates to a method for implementing data transmission in a measurement and control network based on data streams for data transmission in a measurement and control system. Background Art

[0002] Due to the widespread application of Ethernet technology, the vast majority of data transmission networks use Ethernet to complete data transmission. Therefore, Ethernet has gradually become the mainstream architecture of data transmission networks. Building a data transmission network using Ethernet has the advantages of low cost, easy implementation, and wide availability of related components. However, for an application scenario where a measurement and control system has multiple data output devices simultaneously outputting to a system recording / processing device, the uncertainty of transmission delay brought by traditional Ethernet not only results in low efficiency but also poses a risk of data loss.

[0003] Currently, data transmission in a measurement and control system basically forms a star network through an Ethernet switch to connect multiple data output nodes and transmission target nodes (such as recording nodes, data processing nodes, etc.). The data output nodes directly send data to the target nodes through the switch, or the data output nodes output data in a broadcast manner, and then the target nodes receive this data. In such an environment, many times, multiple output nodes need to send data to the same target node at the same time, which will generate routing competition, leading to a significant decrease in transmission efficiency. When the total amount of data output is large, data loss may even occur.

[0004] The present invention realizes parallel transmission of multiple output nodes to the target node by means of data stream scheduling and the transmission target node pre-ordering the required data streams, avoiding routing competition, and thus completing efficient data transmission within the measurement and control system. Summary of the Invention

[0005] The nodes of the data transmission network in a measurement and control system can be divided into three categories. One is the data output node, such as a data acquisition node, an image recording node, etc. The second is the data processing / recording node, and the third is the switching node. According to the characteristics of the measurement and control system, the data output node outputs data to the data processing / recording node, there is no communication between the output nodes, and the data transmission is unidirectional and the data output volume is constant. Accordingly, the present invention divides all the data output by all data output nodes into different data streams in advance according to the data requirements of the data processing / recording nodes in the measurement and control system. The data output nodes divide the output data into different data streams according to this division and output them. At the same time, the data processing / recording nodes pre-order one or more data streams according to the required data. When the data reaches the switching node, the switching node schedules the data streams to one or more data processing / recording nodes according to the pre-orders of each data processing / recording node.

[0006] First, according to the measurement parameters, sampling rate, and data processing and monitoring requirements within the measurement and control system, before the system runs, the collected data is divided into multiple data streams according to the processing and monitoring requirements. At the same time, based on the requirements for data transmission delay in real-time monitoring and data processing, the data publishing frequency of the switch, or the transmission frequency, is determined. The collected data is then transmitted at the determined frequency, and the transmission bandwidth occupied by each data stream is determined according to the sampling rate of each parameter in each data stream. In addition, a dedicated data buffer is allocated for each data stream in the switching node.

[0007] During the operation of the measurement and control system, the switching node receives the data sent by each data output node in real-time and in parallel and stores it in the buffer. Then, according to the definition of the data stream, the data received from all output nodes is allocated to the relevant data stream buffers. Finally, the data is taken out from each buffer in turn according to the allocated transmission bandwidth, packed, and sent to all data processing plants / recording nodes. In this way, during the entire process of data processing and publishing in the switching node, there is no routing competition or transmission conflict, realizing real-time data communication. Without considering line delay, the data transmission delay index is determined and related to the data publishing frequency.

[0008] The key points for implementing data exchange in the measurement and control system using the above method are as follows: The underlying transmission uses the general Ethernet protocol; The switching node receives the data output by each data output node in real-time and in parallel; The switching node repackages and publishes the data according to the data stream definition according to the processing / monitoring requirements; The processing / monitoring node obtains the data required by this node from the data published by the switching node; The frame rate of data publishing and sending needs to meet the requirements for data transmission delay in processing / monitoring.

[0009] The following is an example to illustrate the specific implementation steps of the present invention.

[0010] Taking a simplified data acquisition system consisting of 4 data acquisition devices, an eight-port switch, 3 data monitoring devices, and a recording device as an example, all data acquisitions use 16-bit analog-to-digital conversion. Among them, the acquisition parameters of data acquisition device 1 are 40, the sampling rate is 10KHz, the acquisition parameters of data acquisition device 2 are 2, the sampling rate is 1MHz, the acquisition parameters of data acquisition device 3 are 130, the sampling rate is 1Hz, and the acquisition parameters of data acquisition device 4 are all 100, and the sampling rate is 50Hz. In addition, the transmission delay index of the system is not greater than 20 milliseconds. In this example, it is assumed that monitoring device 1 needs to monitor the data output by acquisition device 1, monitoring device 2 needs to monitor the first acquisition parameter of acquisition device 2 and all acquisition parameters of acquisition device 4, and monitoring device 3 needs to monitor the second parameter of data acquisition device 2 and all parameters of acquisition devices 1 and 3. The recorder needs to receive the data output by all acquisition devices for recording. The specific implementation steps are as follows: 1) First, according to the monitoring plan, the definition of the data flow can be determined: Data flow 1: All data output by data acquisition device 1; Data flow 2: All sampled data of the first parameter of data acquisition device 2; Data flow 3: All sampled data of the second parameter of data acquisition device 2; Data flow 4: All data output by data acquisition device 3; Data flow 5: All data output by data acquisition device 4; 2) Determine the relevant parameters of data transmission. According to the transmission delay index, the data publishing frequency can be selected as 100Hz. Data flow 1 needs to occupy a transmission bandwidth of 6.4Mb, and the content of each publication is 400 data (data of 10 samplings of all 40 parameters); data flow 2 needs to occupy a transmission bandwidth of 16Mb, and the content of each publication is 1000 samplings of the first parameter; data flow 3 needs to occupy a transmission bandwidth of 16Mb, and the content of each publication is 1000 samplings of the second parameter; data flow 4 needs to occupy a transmission bandwidth of 20.8Kb, and the content of each publication is 130 data (only the data of the first sampling of all 130 data is published for the first time per second, and the rest of the publications are filled with padding words); data flow 5 needs to occupy a transmission bandwidth of 8Mb, and the content of each publication is 100 data (the data of the first sampling of all 100 data is published for the first time per second, filled with padding words for the second publication, the data of the second sampling of all 100 data is published for the third time, filled with padding words for the fourth publication, and so on); 3) Set the data subscription. Monitoring device 1 subscribes to data flow 1; monitoring device 2 subscribes to data flow 2 and data flow 5; monitoring device 3 subscribes to data flow 1, 3, and 5; the recorder and the uplink port of the switch subscribe to all data flows; 4) After the measurement and control system starts running, all data acquisition devices start collecting data and output the collected data to the switch in real time; 5) The switch receives the data output by all acquisition devices in real time and in parallel, and stores the received data into the corresponding data stream buffer according to the definition of the data stream in 1) above; 6) The switch publishes the output data in a broadcast manner through Ethernet at a frequency of 100 Hz. Each time, it broadcasts and sends to all ports of the switch in the order of the data stream numbers and the published content defined in 3) above; 7) Each port of the switch selects the data of the data stream required by the access device from the published data according to the data stream subscription of the access device, and sends the data after packaging to the access device; 8) Repeat the above steps 5) to 7) until the switch is powered off and terminated.

Claims

1. A measurement and control network transmission method based on data flow, characterized in that: Taking advantage of the characteristics of the measurement and control system transmission network, the data output by all data output nodes in the system is transmitted in parallel to the target node in the form of data stream publication.

2. The data stream according to claim 1, wherein The data output by the nodes in the measurement and control system is classified into multiple categories according to their uses. At the switch node, the received network data packets are repackaged into network packets according to the data classification and sent as multiple data streams at a fixed frequency.

3. The data stream publishing method according to claim 1, wherein Set the switch data stream publication frequency according to the data transmission delay requirements of the measurement and control system, and publish the repackaged network packets described in claim 2 to each port of the switch at this frequency.

4. The data stream publication method according to claim 1, wherein each port of the switch selects the required data packets according to the subscription of the data streams related to the devices connected to the port and sends them to the connected devices.