1 Introduction
With the rapid improvement and promotion of computer control in industrial production, the DCS control system does not meet the needs of modern industrial production, and the FCS fieldbus control system replaced will play a strong strength and will be different. The programmable device of the product is connected to a single layer or multi-layer network, allowing them to communicate with each other to implement decentralized control and centralized management. Therefore, PROFIBUS-DP has become an indispensable component of the control system, and is one of the key points of design and maintenance in the control system. The powerful redundant configuration as a special application of PROFIBUS-DP is more capable of playing a pivotable role in certain industries.
2, PROFIBUS-DP characteristics
PROFIBUS-DP is to connect intelligent field devices and automation systems through a standard communication protocol to achieve interoperability. Its appearance promotes the digitization and networking of field devices, and greatly enhances field control functions to make the process control system have openness, and become a control system such as measurement, control and process diagnosis. PROFIBUS-DP is a control system based on the underlying control network, open, digitization, and multipoint communication. The fieldbus system mainly has the following features compared to the traditional DCS system.
(1) Signal transmission digitization, standard unified open;
(2) Interchangeability and interoperability, and the instruments produced by different manufacturing plants can be interconnected;
(3) Control dispersion, the on-site control instrument does not only have testing functions, but also operations and control functions, so that the control circuit is completely dispersed;
(4) A communication line is connected to multiple control equipment or instruments, reducing installation costs, shortening engineering duration, easy to maintain, strong adaptability, high system reliability, strong anti-interference ability, high precision.
3, hardware and software composition
PROFIBUS is not dependent on the manufacturer, and the open fieldbus, all kinds of automation equipment can exchange information through the same interface. PROFIBUS-DP is a high-speed low cost communication for communication with decentralized I / O. Using PROFIBUS-DP can replace a large number of switches and analog signal transmission, which is particularly suitable for communication between PLC and on-site-level distributed I / 0 devices.
3.1 Hardware
(1) Bus connector
The PROFIBUS-DP standard recommended bus station and the bus interconnect use 9-pin D-shaped connector. The socket of the D-shaped connector is connected to the bus station, and the plug of the D-shaped connector is connected to the bus cable. The wiring of the connector is shown in Table 1.
(2) Both the bus terminals at both ends of the data lines A and B should be connected to the bus terminal
The pull-down resistor of the bus terminal is connected to the data reference potential DGND; the pull-up resistor is connected to the positive voltage VP (see Figure 1). When there is no data on the bus on the bus, the two resistance energy guarantees that there is a determined idle potential on the bus, and select whether to use by the switch.
3.2 software
(1) Communication protocol PROFIBUS ~ DP can use flexible topology, support star, tree, annular structure, and redundant communication links. ,
(2) Electronic equipment data file (GSD)
In order to integrate PROFIBUS products produced by different manufacturers, manufacturers must provide functional parameters of these products in GSD files, ie electronic equipment database files (such as I / O points, diagnostic information, baud rate, time monitoring, etc.). The standard GSD data expands the communication to the operator control level. Use the configuration tools made according to the GSD file to integrate equipment produced by different vendors in the same bus system. GSD files can be divided into three parts:
. The general specification includes manufacturers and equipment names, hardware and software versions, baud rates, monitoring time intervals and bus plugs designated signals;
. Specifications related to the DP master, including various parameters, such as allowing the number of slaves, upload / loading capabilities;
. The specifications associated with DP from, including the number of slave input / output channels, types, and diagnostic data.
4, application
The following is a coke oven as an example, how to implement control is described in detail on the PROFIBUS-DP redundant configuration, see Figure 2.
4.1 Redundant Safety Configuration System
The 7M coke oven uses redundant CPU configuration + ET200M + ETI200L + Y-Link to form a PLC distributed I / 0 system. Standards such as other encoders and inverters are integrated into redundant PLC systems via Y-Link.
4.1.1 Main Station Configuration
The CPU of the 7M coke oven is used in the Siemens S7-417H redundant system. Create a project in STEP7, select SIMATIC-H Station in the Station option under the Insert menu, add a new $ 7-400h station. The specific configuration steps are as follows:
(1) Double-click Hardware to open the hardware configuration at a $ 7-400H station.
(2) Add a UR2H rack.
(3) Configure the Yan Sangfang Evil CPU and have not determined the address of the PROFIBUS-DP master on the CPU 2.
(4) Add the synchronization sub-template to the IF1 and IF2 slots.
(5) Add an Ethernet card and configure the MAC network address. Communicate with the HMI system WinCC software interface via Ethernet.
(6) Configure the hardware of the rack 0 copy, paste, copy the rack 1 and adjust the network parameters, such as the MAC address of the Ethernet, etc., two racks appear in the hardware configuration, see Figure 3.
(7) System parameters Set the template parameter assignment in the fault tolerance station and the template parameters in the S7-400 standard station have no difference. For the central processor unit, simply set the hardware configuration diagram parameters of the CPU S7-400h on the CPUO (CPU on the rack 0), the set value will be automatically assigned to the CPUL (CPU on the rack 1). If the CPU0 and CPUL do not form a ring network, then the two parameters are exactly the same, otherwise, the settings of the following parameter CPU1 will be different from the CPU0.
. MPI address of CPU
. Integrated PROFIBUS-DP interface station address and diagnostic address
. Template in the I / O address area
The data consistency must not be guaranteed in the process image in the I / O address area to be completely in the process image or in the process image.
The CPU system parameter setting is as follows:
1 Click the CYCLE / CLOCKMEMORY option bar to set the CPU loop processing parameter. Recommended Settings: Scan loop monitor time is set as much as possible (the default is 150ms), the process input image is as small as possible (slightly larger than the actual input point number), the I / O access error occurs when the I / O access error occurs, only The case used to input errors and output errors.
2 Set the number of packets in the diagnostic buffer in the Diagnostics / Clock option bar to set the number of packets to the diagnostic buffer to set a larger value, such as 1000.
3 Monitoring time of the module In the "STARTUP" option bar, you can specify the module monitoring time, depending on the configuration of the fault tolerant station. If the monitoring time is too short, the CPU will enter W # 16 # 6547 event in the diagnostic buffer. The transmission time of the parameters depends on the following factors:
· The transfer rate of the bus system (high transmission rate = "transmission time is short);
. The size of the parameters and system data block (parameter length = "transmission time is long);
. Load on the bus system (slave "=" transmission time long) recommended: 600 (corresponding to 60 seconds).
4CPU Self-Test Cycle In the HParameter option bar, configure the cycle of the self-test after the CPU. Optional range is 10 ~ 60000 min. Recommended setting: Use the default value 90min.
4.1.2 Configuring ET200M from station
The I / O module uses the PROFIBUS-DP remote communication, and it is implemented with ET200M. Specific steps are as follows:
(1) Click the DP bus "Master: DPMASTERSYSTEM (1)", under the hardware directory PROFIBUS-DP, select an IM1 53-2 site, double-click to add an ET200M station.
(2) Set the address of the ET200M station.
(3) Add I / O modules on the ET200M station. See Figure 4 after the slave configuration is configured.
4.1.3 Y-Link
Since the design uses a redundant system, the DP communication of the control-level device in the field must be implemented using Y-Link. The configuration Y-Link coupler steps are as follows:
(1) Click the DP bus master: DPMASTERSYSTEM to select IM157 under DP / PALINK of the hardware directory, and double-click to add a station.
(2) Set the Y-Link station address.
(3) Select Set Y-LII to - a DP / DP coupler.
(4) Add a single bus interface to the PROFIBUS bus after Y-Link, such as: MasterDrive et al. Field devices such as inverters, encoders, etc. need to install the corresponding GSD files, and the configuration completed interface is shown in Figure 4.
4.2 Application
Siemens $ 7-417H Strong redundant system powerful extension and communication capabilities, easy-to-real distributed structure makes it a preferred solution in the field of high-end performance control, has been widely used in automated production lines, mechanical manufacturing, warehousing industry, architecture System automation and steel industry.
5, conclude
Through the specific application of the 7M coke oven, the superiority of PROFIBUS-DP technology is fully embodied. PROFIBUS-DP technology not only reduces the equipment to ask a large number of hard-wire connection and equipment failure points, but the workload of operation is more secure, and the amount of work maintained by the user is also greatly reduced, and the subsequent cost of investment equipment is saved. It is the industrial site control. The direction of electrical automation development of level equipment is the trend of network development, and it is also an inevitable result of the development of information technology.
Editor in charge: GT, read full text
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