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In 1991, Echelon Corporation of the United States introduced the LonWorks (Local Operating Networks) network, referred to as the L0N network, which marked the new era of control system networks. LonWorks is a complete, fully open, interoperable, mature and low-cost distributed control network technology. Many manufacturers and users have adopted Lon Works technology in their control network solutions. To date, more than 2,500 companies worldwide have used LonWorks technology to produce a wide range of LonWorks products to meet the needs of modern buildings, factories, transportation systems, urban infrastructure (water, electricity, gas, etc.), and home environments. The distributed control network requirements of the automation system. In 1995, the LonWorks control network was identified by the United States as part of the building automation control network standard. At present, the world's largest building control companies, such as Honeywell, Andover, Sybil, Johnson, Langeer, and Sacheville, are using LonWorks technology to transform their products, and have become a world technology trend. The market development of the previous LONWORKS products focused on the competition with the traditional PLC/IPC fieldbus. However, in the industrial environment where Profibus, Interbus, and CAN buses are prevalent, there is obviously not much competition. As a result, LONWORKS has made significant progress in buildings and isolated industrial sites such as dyeing machines. Many engineering examples show that with careful design, the building can be equipped with only a single LONWORKS network, allowing HVAC (heating, ventilation and cooling), electrical lighting, solar shielding and safety functions, and open control devices to interoperate on the network. 
In contrast, the application prospects of LONWORKS in the industrial field have not been recognized by everyone and have encountered many difficulties. The reason is that everyone accepted the principle of distributed intelligent control. However, LONWORKS is leading the RS485-based traditional field communication cabling technology with its excellent stability and flexible free topology cabling technology. LONWORKS can meet special requirements smartly and economically. The ability to provide developers with the basis for a solution in the form of a functional profile. There are functional profiles for many devices such as engines, pumps, frequency converters, PLCs, valves, sensors, etc.
Because the application prospect of LONWORKS in the industrial field has not been recognized by everyone, it has been greatly developed in the building automation industry. As for the control of electromechanical equipment in building automation, LONWORKS does not have a big advantage, which is the traditional PLC/IPC world. PLC/IPC firmly occupies the traditional industrial machinery/industrial equipment control base with its versatility, reliability and low cost advantages. This is why LONWORKS has not been able to develop much after years of competing with PLC/IPC on the industrial scene. However, LONWORKS, after all, is technically leading the industry in today's industrial automation systems (PLC/IPC fieldbus) with its peer-to-peer design and smart distributed field devices. With the development of industrial automation and network technology, the network requirements for the traditional PLC are getting higher and higher, and the new term “industrial Ethernet†also appears. But also has the tendency to replace the field bus.
Although there are many ways to form a control network, flat, peer-to- peer (P2P) architecture is the best for automated control. Compared with any other hierarchical architecture, the P2P architecture no longer has a single point of failure that is inherent in the hierarchical architecture. In the traditional architecture, information from a certain device is passed to the target device and must first be transmitted to the central device or gateway. Therefore, communication between every two non-central devices includes an extra step, or the possibility of a failure. In contrast to the design of the P2P architecture, it allows direct communication between the two devices, which avoids the possibility of failure of the central controller and eliminates the bottleneck effect. In addition, in the P2P design, the failure of the device may be more likely to affect only one device, rather than potentially affecting many devices as in a non-flat, non-peer-echelon architecture. From Figure 2, we can see the quality of the traditional master-slave communication network and the P2P communication network through monitoring. 
The communication of devices in the LonWorks network is implemented using a network standard language called LonTalk. The LonTalk protocol consists of various underlying protocols that allow different devices on the network to intelligently communicate with each other. The communication service provided by the LonTalk protocol enables applications in the device to send and receive messages with other devices on the network without knowing the network topology or the name, address, or other device functions of the network. The LonWorks protocol can optionally provide end-to-end message validation, message validation, and priority transmission to provide for a limited number of transaction processing. Support for network management services enables remote network management tools to interact with other devices over the network, including reconfiguration of network addresses and parameters, downloading applications, reporting network problems, and applications that start/stop/reset devices. LonTalk - that is, the LonWorks system - can communicate on any physical medium, including power lines, twisted pair, wireless (RF), infrared (IR), coaxial cable, and fiber optics.
And the so-called interoperability means that each device in the network can turn digital serial data into another device through the network according to the information it needs to publish. Data transfer usually involves one sender of information, one or more recipients. There must be some form of connection between the sender and the receiver so that the data can be transferred in a series of on-off states. All devices connected to a particular channel must have compatible transceivers operating at the same rate so that interoperability can be achieved. But interoperable networks are not achievable by traditional master-slave communication networks (peer-to-peer). The transfer of serial data between network devices requires a set of communication protocols. The protocols usually exist in each network in the form of embedded software or firmware code. Device. Devices that contain this protocol code and some type of operational intelligence are called network nodes. It consists of a Neuron neural chip, sensing and control equipment, a transceiver (used to establish the physical connection between the Neuron chip and the transmission), and a power supply.
The LonTalk communication protocol is the core of the LONWORKS technology, which provides a set of communication services so that applications in the device can send and receive messages over the network to other devices without having to know the network topology, name, address, or other device functions. LONTALK protocol can selectively provide end-to-end message confirmation, message confirmation, and priority transmission to set transaction time. It is a layered, packet-based, peer-to-peer communication protocol, like the Ethernet and Internet protocols involved. However, the LONTALK protocol is designed for the specific requirements of the control system rather than the data processing system. Each packet consists of a variable number of bytes, is of variable length, and contains application layer information as well as addressing and other information. Each device on the channel monitors each packet transmitted on the channel to determine if it is a recipient. If yes, then processing to determine whether to include the information needed for the node application or whether it is a network management packet. LonTa1k protocol is a direct object-oriented network protocol, that is, network nodes realize the connection between network nodes. When the network variable defined as the output changes, the value of the network variable can be automatically sent out, so that all the variables defined as the input node receive its change in order to activate the corresponding processing process (event-triggered type). Standard network variables enable different manufacturers' products to translate and transmit data correctly by establishing standard data transfer modes, facilitating interchangeability and interoperability of devices. In addition, because the network variable is limited in length, up to 31B, it provides four types of message services: response mode, request/response mode, non-response retransmission mode, and non-response mode.
To simplify network configuration and management, logical addresses can be assigned to nodes. Logical addresses allow users to associate a name and physical device with a node. Logical addresses in the control network using LONTALK are defined during network configuration. All logical addresses have two parts. The first part is the ID of the specified domain. This designated domain is a collection of nodes and they can interoperate with each other. The second part of the logical address specifies a single node in the domain with a unique 15-bit node address.
For the PLC to intervene in the LONWORKS network to achieve real-time monitoring of the PLC data/status, the application program of the gateway node must be used to operate the PLC.
This article takes the part of the LONWORKS system of Delta PLC in the intelligent building control system of a large square in Shanghai as an example to introduce the network variables and command format of the communication between the gateway node and the PLC. In this system, the electromechanical equipment is the central air conditioner. In the cabinet, the PLC adjusts the opening of the fresh air valve according to the return air temperature through the PID to achieve the purpose of controlling the room or unit room temperature. Wind cabinet network schematic see Figure 3. 
1. The network variable nviConfig configures the network variable nvoDR[0~7] read-only analog (AI)
nvoXR[0~7] read-only digital (DI)
nviMW[0~12] Write only digital (DO)
nviDW[0~31] only write analog (AO)
2, preparation of network variables nviConfig input format: XXXXXXXXXXX
Instruction operation number: set value (1) instruction: R read the set value, set the set value;
(II) Operation number: 00 Communication format setting,
01~08nvoDR[0~7] Connection Setting 09~16nvoXR[0~7] Connection Setting 17~29nvoMW[0~12] Connection Setting 30~61nvoDW[0~31] Connection Setting (III) Setting Value: Communication Format setting BBBBB_TT (BBBBB baud rate such as 0960, _ space, TT communication seconds interval as 01)
(D) connection settings: SSIIAAAA (SS device number such as 01, II instructions such as 02, AAAA address such as 1AFF)
3, the connection of read-only analog and read-only digital automatically read the device at the interval of communication seconds to refresh, write only the amount of digital and only write analog variable network variables automatically sent to the device. Since the LONTALK protocol specifies that the gateway node's application already contains the logical address of the gateway node, it exists as a name in the application of the gateway node. Therefore, the communication part of the gateway node to the PLC does not need to take into account the PLC's communication address, but only the general default PLC address.
In Figure 4, the variable is defined as read-only. In the communication protocol of Delta PLC, the address corresponding to D0 is H1000, then the address corresponding to D100 is H1064, and so on. Since the gateway address of the LONTALK protocol has been determined in the application program of the gateway node, then the communication between the gateway node and the PLC becomes a standard unified program, and only the default communication address of the PLC can be used, as shown in Figure 4. The communication addresses of the PLCs shown in Figure 5 and Figure 6 are all unified to 1. 
From Fig. 3, the on-site monitoring is realized by the text display TP04G, and the remote monitoring is realized through the LONWORKS gateway node. This forms a distributed intelligent control system. The remote host computer exchanges data with the LON gateway at the end. The gateway node determines whether the data packet is suitable for the gateway according to the data packet received from the channel. If yes, the gateway node application program then sends the data to the PLC. Remote monitoring.
Although the LON distributed intelligent control system does not require the end PLC to provide the address, the address setting function of the text display and the PLC greatly facilitates the program writer and the on-site debugging personnel. The use of this function is briefly described as follows: DEL04M is provided by the TP04G. DRIVER, this function is suitable for multi-address applications of DELTA PLC. We know that in the manufacture of standard equipment, we need standardized procedures to simplify on-site commissioning and facilitate the management of program files. Then, in the process of networking standard equipment, it is necessary to change the address of the PLC in order to achieve the purpose of network control. If a traditional PLC program is implemented, a standard device has a set of programs. Very inconvenient program management. Use the text display's DELTAMx function to just change the text's communication address in the text's system menu, and the text program needs to be set to the corresponding address in the PLC's D1121.
The perpetual calendar function provided by the text display provides convenience for the regular on/off function of the air conditioning system. The PLC can control the timing of the fan through the perpetual calendar. The realization of the network function provides convenience for the managers of the building electromechanical equipment. The management personnel can give orders to the electromechanical equipment located anywhere in the building through the network, and can also check the operating status of the electromechanical equipment at any location through the LON network at any time. Realized intelligent control of buildings.
LonWorks technology has gradually become the basic specification of the district/building intelligent system. The LonWorks network is very easy to interconnect with other networks, such as the Internet network, which can achieve remote operation and control. LonWorks' open, interoperable, mature and low-cost features have led many manufacturers and users to adopt LonWorks technology in their control network solutions. In addition, for the end user, the initial investment in the project is greatly reduced, system management is simple, and adding new features is very simple. It can be inferred that LonWorks control network technology will be more and more important for people to promote. PLC as a general and reliable industrial controller is still widely used in the industrial field, and more and more network requirements in the civil market today, I believe that increasingly powerful PLC network function will also be more and more into people's In everyday life.
Conclusion With its high reliability/universality and powerful network communication capabilities, PLC is a good combination of industrial equipment and civil systems. The integrated building monitoring system displays the operating status of industrial equipment in real time. The operator can know at a glance the condition of any equipment in the building and can control any equipment at any time. Greatly reduced management costs and increased automation. Therefore, it has great application prospects.
Delta PLC Network Application Based on LONWORKS Building Automation
Introduction With the development of society, people are increasingly demanding living and office conditions, and community monitoring/smart building automation systems have become the current direction of development. The traditional industrial control system has gradually gained the approval of the civil industry with its high reliability and stability. The network has become an indispensable part of people's daily life, and the network expansion function of the industrial control system is also increasingly used in building control. This article describes the application of PLCs commonly used in building control in traditional industrial control systems.
Figure 1 Network diagram of LONWORKS
Figure 2 Comparison of Network Organizations
Figure 3 wind cabinet network schematic
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