LPD200A HITACHI controller module

LPD200A HITACHI controller module

LPD200A HITACHI controller module

Xiamen Cigarette Factory was approved by the State Tobacco Administration to establish a CO2 expanded tobacco production line to meet the market demand. After negotiation, Xiamen cigarette factory CO2 expansion tobacco automatic system uses ControlNet network as the main control network, and the network structure is redundant double network, safe and reliable operation, real-time strength, easy to expand; The system design is reasonable. Perfect function, easy to operate. This system is one of the successful applications of ControlNet redundancy network in cigarette industry, and has reached the advanced level of cigarette control systems at home and abroad. The network has been running successfully for more than two years with stable performance and has achieved good social and economic benefits. The AB control network adopted by the system is introduced as follows:

2AB Overview of the control network

AB control network adopts a new communication mode, that is, Producer/Consumer mode. This mode allows all nodes on the network to access the same data from a single data source at the same time. It is used for information transmission in applications with strict requirements on time, which is a high-speed deterministic network. It allows the transmission of time-sensitive packets but does not impact the time-sensitive packets. As a high-speed communication link between controllers and I/O devices, it integrates the capabilities of various existing networks. The network has the following advantages [1] :

① Synchronization of all nodes in the network, high information throughput, high speed and high efficiency, so as to achieve accurate synchronization control and high real-time network control.

② On the same link, multiple controllers are used to control independent I/O.

③ Nodes can be divided into different priorities to meet different real-time requirements.

(4) CRC check and other check measures are provided for each frame of information, and the bit error rate of data transmission is low.

⑤ Nodes with serious faults can be automatically removed from the network to ensure the normal operation of the network.

It acts as a high-speed communication link between controller I/O devices, combining the capabilities of existing I/O and DH+ links. It can fully meet the production requirements of cigarette enterprises.

Network structure and characteristics of 3CO2 expanded tobacco production line

Xiamen Cigarette Factory adopts the distributed measurement and control management system, with one central control room and four sub-sites (see Figure 1). The PLC stations communicate with each other through ControlNet network, and the four PCS in the central control room communicate with the server through Ethernet. The site measurement and control is completed by PLC, and the data monitoring and analysis are undertaken by the workstation computer. Each sub-station operates independently. Sharing information resources through the Internet; The central control room can monitor the operation of each sub-station and implement optimal scheduling. The main control network ControlNet redundancy network hangs four 1756-L55M13 PLCS, respectively control the cold end, hot end, feed end and discharge end four sub-stations. According to the different conditions of each sub-station, the PLC also through DeviceNet[2] to connect a number of FLEX I/O and frequency converter; Cold end and hot end PLC also through DH+ network with a certain number of model 1747-K524 SLC, used to monitor the combustion fur

nace, compressor and other independent and dispersed equipment. The three-layer network structure is commonly used in cigarette industry. The first layer of information layer uses Ethernet, which is used for data collection, historical data query and program maintenance in the whole factory. The second layer of automation control uses the ControlNet network for real-time I/O control and packet transmission. The third layer is the equipment layer, which is used for low cost and high efficiency information integration of the underlying equipment.

The ControlNet network features high throughput, resource sharing, coaxial or optical transmission medium, support for redundant media, and flexible architecture. When the communication speed is 5Mb/s, the minimum network refresh time can be up to 2ms, the number of addressable nodes is 99, and the transmission distance of coaxial cable can be up to 3km(30km when using the repeater of optical fiber medium). This communication speed and distance are more than adequate for the application of cigarette industry, coaxial cable or optical fiber can be selected according to the distance or the actual situation of the plant.

The ControlNet network is a high-speed deterministic redundant network. When one network cable is interrupted, the other network cable will work immediately without any impact on communication and control, ensuring safe production.

ControlNet network configuration and programming is simple, through the ControlLogix Gateway, it can realize the data exchange between Ethernet (Ethernet), DeviceNet (device network), RIO (remote IO), DH (data highway) networks. This flexible connection makes it easy to expand and upgrade. If the tobacco factory needs to add other equipment, it only needs to add PLC, and the original system does not need to be changed. For example, the frequency converter or soft starter of the control motor connected to the DeviceNet can directly send commands to the device through the touch screen or by the PLC to control the operation of the device, and can read data from the device, monitor the state of the device, easy to operate.

The ControlNet network supports master-slave communication, multi-master communication, peer-to-peer communication, and any mixture of these communications. The input data and peer-to-peer communication data can be broadcast through multiple channels. The communication form can be configured and applied flexibly, and the performance of the network can be improved. While time-critical control information can be transmitted, other non-time-critical information can also be transmitted. Within each network refresh cycle, time-critical information must be transmitted. This ensures the timeliness and reliability of the control. When editing the Tag on some AB applications (e.g. Panelbuilder32), there are scheduled and unscheduled options for selecting the delivery of information.

4 Communication Mode

The ControlNet network is a new "producer/customer" communication mode based on open network technology. It allows all nodes on the network to access the same data simultaneously from a single data source. The advantages of this producer/customer network are as follows: ① improve efficiency. Once a data source sends data, multiple nodes can receive data at the same time. Packets are identified by the directory. ② Accurate synchronization. More devices can be added to the network without increasing network traffic, and data from all nodes can arrive at the same time.

(1) Characteristics of traditional source/destination network mode

① Multiple data packets are needed to transmit the same information to multiple devices;

② The time of data arriving at different destinations is different;

(3) Generate additional network traffic, affecting network performance;

④ Different networks are used for packet sending and time-intensive I/O data.

(2) Characteristics of producer/customer network mode

① Multiple nodes can receive data from a single producer (data source);

(2) The nodes can be synchronized (multi-channel broadcast);

③ The optimized bandwidth potential can be used to enhance the system function;

④ Use the same network for programming and I/O information transmission.

5. Application and maintenance of AB control network in expanded tobacco production line of Xiamen Cigarette Factory

Xiamen cigarette factory control network from operation to now more stable. There has been a single network disconnection fault, because of the redundant double network, the production has not been affected. The fault was caused by the misoperation of disconnecting one of the nodes. After maintenance, it soon returned to normal.

The ControlNet network of expansion tobacco production line of Xiamen Cigarette Factory is bus type, and there is a mid-end resistor at each end of the network. The transmission medium is coaxial cable, and the cable has five layers of shielding. The use of coaxial cable makes maintenance easier. The configuration software used by ControlNet is RSNETWORX, which provides a graphical view of the network (see Figure 2) with the ability to configure the network both online and off-line. This software is essential for configuring and maintaining the control network.

When A network fault occurs, first observe the PLC 1756-CNB network card communication indicators. If the communication indicators of network A and network B alternately flash red and green, it indicates that the communication is abnormal. If only network B is faulty, it can be directly disconnected, which will not affect the network communication and normal production. Disconnect the faulty network segment by segment check until the breakpoint is found. If no problem is found in the hardware check, RSNETWORX can be started to check whether the network configuration is correct. If not, the original backup network configuration program can be downloaded to the PLC again.

6 Summary

In general, the ControlNet network is an advanced network control system platform, is a large scale, simple expansion, safe and stable, advanced technology PLC redundancy control network, can ensure the continuous production and safe production of tobacco factory, can fully meet the needs of the cigarette industry.

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