LonWorks field bus technology in train monitoring system (1)

1. introduction

With the continuous development of science and technology and in various industry sectors are widely used, there is growing evidence that a particular industry or a wider area of uniform technical standards are increasingly important and becomes a restriction or promotion of industry technology development of an extremely important factor.

In the railway system in the same issue, if there are no uniform standards, various vehicle systems manufacturers often along their way in the development of a proprietary, non-compatible interface products, to limit the buyer can only use their systems, products and technology competition, the constraints on the development of related technologies. The past quite a long time, the railway system train network communication technology is in a State of non-standards, to a large extent restricted the train network monitoring system for technical development. In 1999, for international train communication network, developed two on appropriate standards: IEC (International Electrotechnical Commission) the train communication network law and IEEE (United States of electrical and electronics engineers) for the train network communication protocol. The latter's content scope includes the former, it provides for two types of train communications network: the model t and L type. T-type i.e. TCN network (TCN), L-free topology twisted-pair for the channel regulations》by LonWorks communication network. Reference to the above two big international standard, combined with the domestic realities of railway traction, in 2002, China's Ministry of railways has also developed a corresponding People's Republic of China railway industry standards – train communication network. This standard also defines two types of train communications network: the model t and L type. At present, the domestic application of train communication network is concentrated mainly in the L-type network. In the railway system in the adoption of open standards for IEEE will guarantee many manufacturers product interoperability, which can help to promote supply chain in each link of competitiveness, speed up technology development.

2. technical characteristics of the network control

LonWorks (Local Operating Networks) is a United States Echelon Corporation 1991 launch of fieldbus technology, it can be a good solution in the control network design, composition, installation and maintenance of a large number of issues appear in.

LonWorks network control technology features:

(1) open: open network protocols, on any user equality;

(2) interoperability: LonTalk LonWorks communication protocol ISO (International Organization for Standardization) defined by the OSI open interconnection model.

Any manufacturer's products can achieve interoperability;

(3) communication media: practically include all available communication media, including twisted-pair and power line, optical fiber, coaxial cable, radio waves, infrared, etc., but also in the same network can have a variety of communications media;

(4) network architecture: can be a master-slave, peer-based or client/server mode;

(5) network topology: a star, bus, ring and freedom;

(6) communication rate: up to 1.25Mb/s, effective communication distance to 130m.

Use twisted pair, 78Kb/s rate linear communication distance up to 2700m;

(7) LonWorks network communication uses object-oriented design methods: LonWorks network communication technology called a "network variables" that enables the design of network traffic reduced to parameter is set to increase the reliability of the communication;

It is precisely because of the LonWorks technology fully meet the future requirements for measurement and control system, at present, its use has spread all over the world in 56 countries and areas of industry, building, transport, energy and other automation field.

3.LonWorks technology applications

3.1 railways train communication network standards on the provisions of the L-network

Standard in the "applies to connect a basic operating unit (a single vehicle or vehicle combination of fixed) or a set of basic operation of the unit of electronic devices, the transfer time is too short, time is not required to determine the event-driven message data transmission", mainly used in the train monitor system.

As the train monitoring system monitor objects relatively fixed and train marshalling of particularity, the standard also provides the most common network topologies and network of bus, as shown in Figure 1.

3.2 train network monitoring system overview

In many applications, the main train network monitoring system is implemented on all vehicles in the operation of train equipment running monitoring and, if required, to be controlled device remote control operation.

These vehicles are often relatively fixed equipment, including air conditioning controller, auxiliary power inverter, smoke and fire alarms, access control, alarm, hotbox antiskid, train power supply controllers, etc., almost all required on electronic devices. System on these devices monitor control variables, both analog and digital. Because the number of train of hanging often exceeds 18, the entire system of monitoring object number, network traffic is relatively large. In addition, because the train marshalling behavior may change in the network monitoring system must also be set according to the setting for the car number and formation on the entire network for dynamic configuration to accommodate the different train marshalling. System design, in addition to the generic node design, because many train equipment using the traditional micro-control technology, but also keep the original RS-232/485 serial communication mode, the system to establish communication with these devices, you must install the protocol conversion node. Therefore, the overall system design and implementation is more complex.

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