In Communication Based Train Control (CBTC), the on-board controller plays a key role. It ensures that the train is positioned accurately, always in the safe speed control range, and makes the two-way communication between the train and the ground real-time and efficient. Because of the effect of urban rail traffic environment, the train is adhering to dust. In the past, more attention has been paid to the cleaning and dust removal of the car body, and the influence of dust on the operation of on-board equipment is usually neglected. Taking the train on Hangzhou Metro Line 1 as an example, this paper analyses the hazards and causes of dust on the working status of on-board controller, hoping that it can be used for urban rail. Tao construction provides some help. With the increasing complexity of the density of rail transit network and the increasing speed of traffic, it is urgent to build a safe, stable and economically viable signal system. Train control system can fully guarantee the safety of driving and improve the efficiency of operation, which is very important. In the Communication-based Train Control system, train control equipment is mainly composed of microprocessors and other VLSI chips. It is different from the railway signal equipment, which has long been based on safety relay, because its devices do not have asymmetric fault characteristics. China is a country with serious environmental pollution.
Dust pollution is more severe than other countries. Dust pollution is a common cause of electrical contact failure of electromechanical components. Protecting processors and chip circuits exposed to dust at all times from dust hazards will further improve the reliability of train control system and reduce the probability of failure.
Hangzhou Line 1 adopts the “B” type tramway produced by Alstom and a domestic car factory. A total of six carriages are equipped with an on-board controller at both ends of the cab. Each vehicle controller consists of a mobile communication system (MR), a query host (TI), two sets of ATP/ATO cages, two analog accelerometers, two digital accelerometers, three safety relays and connectors (for interface with the train system). The main body of the on-board controller is composed of two sets of automatic train protection and running cage.
The two cages are equipped with two Ethernet switching and expander boards, three main processor boards, two main processor external memory boards, four input/output boards, one mobile wireless host and query power board, one cage module power supply unsafe relay board, one safety relay board and one query transponder converter board. The cage is mainly responsible for determining the position of the train, supervising the speed of the train, ensuring the proper necessary braking sequence, managing the train control mode, and controlling the train according to the information provided by the ZC beside the track. It can be seen that the key to the stability of the on-board controller lies in the normal operation of two sets of automatic train protection and operation (ATP/ATO) cages. However, the boards in the cage are all printed circuit boards covered with microprocessors and other VLSI chips. The electrification of the board will affect the charge distribution around the board and the deposition of the dust, which will attach the adsorbed dust to it. The corrosion of dust particles on the contact surface of electronic board is galvanic corrosion, which is more likely to occur in humid environment with higher humidity. The relatively closed humid environment in metro tunnels is conducive to the formation of such corrosion. The main dust matter in the closed tunnel is composed of friction debris deposited for a long time in the tunnel, carbon brush powder residue from pantograph of train and civil remnants of subway. Because the electronic board can not be completely sealed, the dust will inevitably enter the equipment through the voids on the electrical equipment through the movement of train airflow, and selectively deposit on the contact surface of the electronic board due to the electromagnetic and thermal fields inside the equipment. At present, the electroplating process of PCB is unavoidable for the existence of micro-holes on the surface of contact coatings. In the wet environment, because the wetting contact surface of dust will form a water film, the water-soluble salts in the particles on the contact surface will dissolve in water, thus forming electrolyte, which will corrode the products and spread to the surface of micro-holes. High contact resistance will break the connection when it is serious. In addition, there are some rough surfaces on the surface of PCB during production, resulting in the existence of local pores or relatively low concave parts, which will absorb water due to capillary force, and accelerate the breakage of electronic board due to the corrosion of dust solution. The insoluble components in the dust particles may scratch the surface of the coating, even make the base metal exposed and corroded, or form leakage current between the two conductors, resulting in the failure of the related circuit of the system. Due to the above-mentioned hazards caused by dust on equipment, it will inevitably increase the hidden danger of vehicle controller operation and eventually cause failure. If the circuit of the board card in the on-board processor is abnormal, the corresponding board will form a fault alarm, which will make the individual operation mode of the train unavailable, and the board card in operation will suddenly stop working, even lead to the emergency braking of the train, affecting the normal operation of the line.
With the development of electronic technology, the unit area or volume power density of electronic components and equipment is increasing day by day, while the power of electronic equipment is increasing, the volume of electronic equipment is gradually shrinking, and the heat dissipation problem caused by it has become the focus of common concern of businessmen and researchers. According to the relevant research, the main failure of electronic instruments and equipment is the damage caused by overheating.
The inefficiency of electronic instruments and equipment increases exponentially with the increase of temperature, and more serious. There is also a 10-degree-of-freedom rule in some devices, that is, the failure rate of electronic devices will more than double with the increase of environmental temperature by 10-degree-of-freedom. The closed humid environment of Metro is worse than that of land. With the increase of temperature, the damage rate will be more serious and the service life of equipment will be affected. Dust contains many fibers. Fibers can be divided into natural fibers and chemical fibers.
Fibers have strong adhesion. Under the influence of static electricity of electronic equipment, dust particles are wrapped on board and card. As time goes on, the heat dissipation of electronic components on board is seriously affected. For example, abnormal heat dissipation of processing board will affect its working stability.
Sex, the on-board system will determine its failure. The occasional board alarm in the actual operation of the train, to a certain extent, is caused by poor heat dissipation. Urban national highway traffic and social development are closely related, which determines the overall development of a country. It is necessary to carry out urban rail transit construction. But through the above discussion, it is not difficult to find that the current train controller is generally facing dust hazards, and the harm caused by dust is enormous, not only will affect the service life of equipment, but also will hinder the operation of urban rail. Based on this problem, we must take effective measures, adhere to the principle of prevention-oriented and comprehensive management, and do a good job in prevention and daily maintenance. We should correct our thinking, thermostatic element correct our daily working attitude, clarify the practical significance of train dust treatment. In the normal cleaning process, we should not only do a good job of car body cleaning and dust removal, but also carry out a comprehensive cleaning treatment of on-board equipment to ensure that the train is clean and uniform from inside to outside, and strictly inspect, so as to avoid the phenomenon of harmful radiation. At the same time, effective heat dissipation treatment should be carried out to keep the equipment components in the normal temperature range. In addition, the main content of maintenance and maintenance is reliability. According to the actual situation, appropriate maintenance methods should be selected, including regular, state, after-the-event maintenance and regular scrapping. Make detailed maintenance plan, record carefully, present maintenance report and maintenance cost through statistical tables, effectively avoid abnormal train operation problems. In recent years, urban construction has risen rapidly, and urban rail transit has also made far-reaching development. Urban subway and light rail projects have sprung up in large numbers. In the construction of automatic control system, since we need to strengthen technological innovation and improve the design, we should also pay attention to the details to ensure the normal operation of equipment. Dust is small but always around us, so it is necessary to improve the awareness of the hazards of dust on urban rail transit vehicle control equipment.
Thus in the design and use of on-board equipment to better ensure its efficiency, reduce the occurrence of failures, improve the quality of subway service, better provide people with high-speed and convenient way of travel.