Fully automatic batching system has been frequently used in various industries, such as: metallurgy, non-ferrous metals, chemical industry, building materials, food and other industries. It is the first part of the production of finished products, especially the continuous supply of materials required by the industry, the process control of the ratio directly affects the quality of the finished product, which is a prerequisite for the enterprise to achieve the best economic benefits. Although the different process characteristics of each industry have different requirements for dosage control, but its high reliability, sophistication, prescriptive, maintenance-free, scalable factory automation FA pursues the same goal.

System Function

Based on the above objectives, we designed and manufactured a set of fully automated multi-species mixing batching and weighing of the three electric integrated production line for an enterprise. The dynamic weighing scale, through the CC-Link field bus, together with PLC, HMI/IPC seamlessly form a trinity of metering and feeding system, in which the industrial control machine is connected to the factory ERP/MIS through HUB and Ethernet TCP/IP. the whole batching process is carried out strictly in accordance with the selected recipe ratio and process, and there are multi-stage alarm records to complete the mixing of different raw materials to feed and logistic control, realizing the integration of management and control, and optimizing the production and distribution of different materials. It realizes the integration of management and control, and optimizes the performance and efficiency of process control.

Third, CC-Link Overview

CC-Link is Mitsubishi Electric to high-performance, low-cost, multi-vendor support as the goal of the second generation of open fieldbus launched in 1996, is the control and communication link short, in November 2000, CC-Link Association was established, specifically responsible for the popularization and development of CC-Link in the world.

CC-Link is an open fieldbus with outstanding performance, wide range of applications, easy to use, cost-saving and other outstanding advantages. CC-Link adopts twisted-pair cable as the connecting medium for the master-slave structure, supports up to 64 slaves, and adopts the broadcast polling method to reach the maximum speed of 10 Mbps. PLC or computer as the master of CC-Link with AJ65SBT-RPT repeater can reach a maximum distance of up to 13 Mbps. PLC or computer as CC-Link master with AJ65SBT-RPT repeater can reach up to 13.2 kilometers. The maximum cyclic data capacity of the network bus is 2048 points and 512 words; the maximum instantaneous data transmission is 960 bytes.CC-Link has complete RAS functions such as reservation station function, automatic refresh function, plug-and-play function, and hot standby of master station, detachment of sub-station, station on-line reply, monitoring and testing, etc. In the use of CC-Link, the hardware switch setting, wiring (3-core shielded wires) CC-Link is very convenient and easy to use in terms of hardware switch setting, wiring (3-core shielded cable), and system configuration (parameter setting is sufficient).

At present, CC-Link supports up to 360 kinds of devices, such as: remote I/O, sensors, weighing controllers, regulators, solenoid valves, inverters, touch panels and so on. CC-Link is supported by more than 220 manufacturers, such as Panasonic, Yamato, Yokogawa, Siemens, SMC, DIGITAL, NEC, etc. CC-Link is also the only Asian product that can compete with European and American fieldbus standards.

Four, batching configuration

This automatic dosage system adopts Mitsubishi Electric's MELSEC-A2SHPLC as the main controller, with Mitsubishi GOT touch screen as the lower human-machine interface (HMI), measurement control by 12 sets of Shanghai Daiwa Weighing Company's CFW automatic dosage system (ConstantFeedWeigher) composition. They are connected by CC-Link fieldbus to realize data acquisition and control to ensure the reliability and real-time of the system. The upper computer part selects Advantech IPC610 industrial computer as the monitoring station, with MSWindowsNT4.0forworkstation operating system and SystantFeedWeigher monitoring software CitectVersion5.30 as the running environment, and the system software has a wealth of process operation, monitoring, communication, alarms, management, trending, logging, and human-machine dialog and other functions and has a strong diagnostic capability. has strong diagnostic ability. The hardware and software of the system is the organism of the control system, the above configuration ensures the system integrity, consistency, compatibility and completeness, adapts to the long-term stable operation in the industrial environment, and has the ability of electricity, magnetism and vibration anti-interference, which meets the safety requirements.

1, the lower computer structure and composition

In this project the 12 sets of CFW is mainly used to complete the raw material flow control, in which the CFC-200 meter, it is a set of regulation and arithmetic as one of the multi-functional metering controller, which is the embodiment of Japan's Daiwa system of outstanding metering instrumentation design technology, with sufficient anti-jamming performance, diversified interfaces, self-diagnostic functions, self-tuning PI adjustment function and other features, and with the Mitsubishi A540 With Mitsubishi A540 current vector type frequency converter and SEW high-performance motor, forming a complete mechatronic products, to ensure the accuracy of measurement and control (3 ‰ accuracy), to ensure that the 12 CFW each other instantaneous flow rate ratio is constant.

The lower computer selects CC-Link fieldbus control mode, with Mitsubishi MELSEC-APLC a total of two CC-Link dual-machine redundancy structure, which has advanced, high-speed, reliable, large-capacity features, of which PLC1 is the main control, PLC2 for the backup redundancy, when the communication failure occurs, it can be practiced between the main and backup PLC non-perturbative switching. Since the 12 CFWs are distributed in a decentralized way, CC-Link bus is chosen to connect the Daiwa weighing controller directly to the PLC. The lower human-machine interface (HMI) is Mitsubishi Electric LCD touch screen GOT to ensure that the process data are correctly and timely in the upper PC monitoring station and touch screen to get a double response and display, even if the upper failure or failure, it does not affect the entire process control. Although the monitoring screen of the touch screen is not as rich as the upper HMI, it basically covers the monitoring and operation of the whole system.

The automatic feeder (CFW) is connected to the CC-Link fieldbus as a remote device slave.

The PLC control software is written in symbolic ladder diagram, and gives full consideration to the system resources to reduce the cycle scanning time and improve the real-time controllability. PLC1 is the CC-Link master, and the master module controls the slave's operation and data refreshing, because the A2SHPLC supports the CC-Link instruction, which makes it easier to make the network configuration and the data processing, and the data exchanges between master and slave are automatically linked and updated in the running program. In the running program, the data exchange between master and slave is automatically linked and updated, and the master CPU only needs to exchange the device information with the slave through the RDGET and RDPUT statements. The CC-Link instruction can replace the FROM/TO instruction to handle the data access without caring about the address of the buffer memory.

The communication between the upper and lower computer uses Modbus communication protocol (RS485 mode), the network structure is master-slave structure, the communication medium is twisted pair wire, it is the early cited development of Modicon, which is widely used in the industrial control field and is the de facto industrial network standard. It supports 21 function codes and can communicate with different products from many other manufacturers in the factory. Modbus protocol used in this system is encapsulated in RTU format, which can transmit information at a higher baud rate.

2, batching details

Automatic batching machine is to CitectV5.3032 bit industrial control software for the development and operation of the platform, Citect is based on the WindowsNT platform for distributed control system SCADA software, which provides users with great application flexibility and system prescriptive, in the field of industrial automation has a wide range of applications, is one of the outstanding automation software.

Citect built-in a Cicode real-time multi-tasking SCADA program language, using the rich function library it provides, can flexibly develop complex applications, which is one of the characteristics of its superiority over other SCADA software. The automatic dosage system adopts a tree structure, with a variety of screen call means, in order to facilitate the operation of the use. The system screen is divided into menu homepage, dosage overview monitoring, equipment monitoring, recipe management, trend group record, alarm group record, report, operation log, debugging maintenance, help and other screens. In order to ensure the safe and reliable operation of the system, the automatic dosage system provides three kinds of privileges: operator, administrator and engineer to ensure the safety mechanism of the system. In the development of this batching automatic dosage system, combining the actual process conditions and making full use of Citect's specialties, it mainly accomplishes the functions of recipe setting, process selection and switching, process interlocking, process starting, sequential stopping, fault stopping, process alarming, flow rate and dosage control, and cumulative statistics, and so on.

Citect adopts a C/S structure and connects to the factory ERP/MIS as an input/output server (I/Oserver) via an Ethernet link (TCP/IP protocol). Citect provides common methods to realize Windows-based data exchange between applications and I/Os, such as DDE/NetDDE, OPC, ODBC/SQL, COM/DCOM, CTAPI and so on. Citect provides DDE/NetDDE, OPC, ODBC/SQL, COM/DCOM, CTAPI and other common methods to exchange data between Windows-based applications and I/O. The historical data in this dosage system is accessed by ODBC/SQL to the database server MicrosoftSQLServer 7.0, and for the real-time data exchange, considering the instability and limitation of DDE and OPC, the CTAPI interface provided by Citect is chosen, which is suitable for multiple data exchanges and is more flexible to be used, and avoids code redundancy in the applications, and improves the performance of the data exchange. It avoids code redundancy in each application and improves memory utilization. It provides interfaces to external applications (VB, VC, etc.) with DLL functions, so that user applications can directly operate Citect's Tag variables and support remote operation via TCP/IP. application, very simple. It allows users to monitor real-time data and query historical data through any workstation on the internal corporate network.

V. Conclusion

To sum up, the control system composed of CC-link automatic feeding system CFW with PLCPC and industrial control software has the characteristics of advanced, prescriptive, short implementation cycle, low cost, etc. It can seamlessly combine different types of products from different companies into one, and based on the integrated network platform technology, it realizes the need for security, transparency and economy. One of the fieldbus and industrial control software is the mainstream and hotspot of the development of automation field in the next few years, and it is believed that it will be used more and more in various industries.