1. Urban track
1.1 Status Quo of Urban Rail Transit
In recent years, with the implementation of the reform and opening-up policy and the realization of the goal of economic construction, China’s national economy has experienced vigorous development. The economic development will be accompanied by greater urbanization and will promote the establishment and development of cities. Urban population in 2000 which reached 460 million. At present, about 40 cities are classified as big cities with a population of more than 1 million, of which more than 3 million have a population of more than 3 million. Due to the changes in the regional bureau of the city’s economy and the increasing concentration and radiation effects of big cities, the number of urban migrants has greatly increased, residents travel more frequently, the contradiction between urban transportation needs has become more prominent, and at the same time, with the process of industrialization and the economy With the rapid pace of construction, people’s work pace is getting faster and faster, and the concept of time is stronger. Therefore, punctual, safe and fast delivery methods are needed to meet people's travel needs. Therefore, the safety of rail transit is very important, and the signal system is an important part of completing the inseparable orbital traffic operation .
1.2 Forms and Characteristics of Rail Transit
In general, large cities, especially the capital, provincial capitals and municipalities are political, economic and cultural center of the country or region, the number of people in and out of the city every day office workers and commercial activities and a variety of mobile staff is very large, in order to convey Such a large number of travelers should divide their regions, sub-regions, and sub-roads into different sections. According to the needs of passenger flow, in conjunction with the overall urban planning , environmental protection and other requirements should be considered, and a reasonable selection of the corresponding urban rail transit system. The urban rail transit system is divided into underground railways, modern trams, monorail traffic, and small subways according to the spatial location of the rail buildings in the city, the amount of traffic they can meet, the mode of operation, the track structure, and the management methods. Tracks of the new system.
1.3 Underground Railway
Underground railways, referred to as subways, are the general term for urban high-speed railways, which are the majority of buildings on the ground, and are used as a means of large-capacity rail transit. They are particularly suitable for the construction of urban urban areas and old urban areas. It is characterized by underground passage in the city, which does not occupy surface and above-ground space, has little operational interference, and has a large capacity for transportation. It can transport 30,000 to 60,000 people per hour , but the cost is relatively high. In 1863 , the first subway in the world was opened in London and its total length was 6km . October 1969, Beijing built the first country in the subway, that the first phase of Beijing Subway put into trial operation, but also our own design, the first underground railway construction. At present, the Beijing Metro has a total length of 41.6km and has 30 operating stations. The daily average passenger volume is 1.25 million. At the same time , the Beijing Subway's full-load rate and bicycle operations rank first in the world.
1.4 Modern trams
Modern trams use rails as a vehicle-oriented transport rail transit system. It is based on passenger transportation. It is a modern, high-level passenger transport system developed on the basis of old trams. It has a transmission capacity of 10,000 to 30,000 passengers per hour . It is a medium-traffic urban transport passenger transport system with high-speed and high-speed. Acceleration performance, low noise, low vibration, low impact on the surrounding environment, saving power, energy saving, can be unmanned, at the same time construction costs are cheaper, operating costs are smaller. France is one of the first countries in the world to have modern trams. In Nantes, France, the city has a population of about 450,000 . In 1984 , a modern tram line that runs through the city from east to west was built. The total length of the line is 10.6 km , and the average operating speed is up to 24 km/h . The amount is close to 20 million people. In our country Shanghai , we also use the modern tram traffic system, which is the light rail Pearl line, put into operation in 1998 . Currently, 320 countries have among the urban rail transit system in the world, with a tram (streetcar including modern and old-style tram) up to 84%.
1.5 Monorail Traffic
Monorail traffic refers to the mode of transportation in which a rubber tire-based vehicle operates on a single track. According to the different support methods can be divided into two kinds of straddle type and suspension type. Monorail has the following characteristics: safe operation, run fast, easily on steep slopes, with small radius curves, little pollution and less support, low construction cost, short construction period features. However, when monorail traffic passes through urban landscape areas, downtown areas, and residential areas, passengers are always a little worried; other transportation facilities cannot be interchanged; and when it crosses other elevated traffic facilities, a higher elevated structure must be built: the structure of the ballast devices is complex, The operating time is also long; emergency situations such as vehicle failures require evacuation time. Small and new Metro transportation system, all in the 1980s and 1990s developed a new rail transit system, with advanced technology, low construction cost characteristics. Many places in the world have been built to varying degrees.
2. Signal system
2.1 Characteristics and advantages of urban rail transit signals
The characteristics and advantages of the rail transit signal system include: high technology intensity, rapid replacement and replacement; low investment, quick results, and high efficiency; penetration of railway transportation departments and rail transportation departments, and full-course network-wide service for rail transportation; by rail transit All kinds of real-time information generated by the signal are transmitted at high speed and with high accuracy. The logic of the control command is closely related to the safety and reliability. The rail transit signal is an important area of ​​modern information technology in urban rail transit. Train operation control and command automation for train dispatching are key technologies for the development of railway signals and represent the development trend of urban rail traffic information and control technology. With the rapid development of China’s rail transit construction, today’s urban track signal system technology has been integrated with advanced technologies such as communications, signals, and computers, and has been developed in the direction of digitization, intelligence, and comprehensive automation. Its level of development has become the modernization of urban rails in China. One of the important signs of construction.
Studying the development direction of rail transit signals will also help the railway industry's transportation capabilities and competitiveness.
Rail traffic signal equipment is one of the basic equipment for rail transportation. It is like the eyes and ears of people and the central nervous system. It is responsible for the transmission and monitoring of the information on the use of on-line driving equipment, the real-time status of train operations, and the command and control of transportation dispatch. The main functions of the railway signal are to ensure the safety of rail traffic, expand the capacity of the route, improve the efficiency of transportation organizations, and improve the working conditions of employees.
This paper also analyzes the status quo, technical characteristics and development of China’s signal technology in signal display, station signal interlocking, locomotive signal and train operation control, traffic dispatching and commanding, rail transit hub signals, and signal infrastructure equipment under China’s traditional transportation model. The traffic signal system adapts to the development direction of speeding up development.
2.2 Urban Rail Traffic Signal System
Urban rail traffic signal system usually consists of automatic train control system (Automatic Train Control, referred to as the ATC) composition, ATC system consists of three subsystems:
- Automatic Train Supervision (Automatic Train Supervision, abbreviated ATS)
- the automatic train protection subsystem (Automatic Train Protection, referred to as ATP)
- automatic train operation system (Automatic Train Operation, short ATO)
The three subsystems form a closed-loop system through an information exchange network, which combines ground control with on-board control, and local control and central control, to form a safety equipment-based set of traffic command, operation adjustment, and train driving automation functions. Automatic train control system.
2.3 Train Automatic Control System Classification
1 , according to the way of blocking cloth points: can be divided into fixed and mobile. In the fixed blocking mode, the control mode can be divided into the speed code mode (step type) and the target distance code mode (curve type).
2 , according to locomotive signal transmission: can be divided into continuous and point type.
3 , according to the location of each system equipment can be divided into: control center subsystems, station and trackside subsystems, vehicle equipment subsystems, yard subsystems.
2.4 Fixed Occlusion ATC System
The fixed occlusion ATC system refers to the automatic occlusion method based on the traditional orbital circuit. The occlusion zone is determined by the traction calculation according to the line conditions, and once fixed, it will be fixed. The train is divided into the sections with minimum occlusion intervals, and the ATC system realizes automatic control of train command and train operation based on this characteristic. The fixed occlusion ATC system can be further divided into a speed code mode and a target distance code mode.
2.5 speed code mode
Such as Beijing Subway and Shanghai Metro Line 1 were introduced in the UK and the US Westinghouse company GRS ATC systems fall into this category ATC system, which is a product of 70 to 80 years, the technology is mature, low cost, but the block section The design of the length is limited by the most unfavorable line conditions and the lowest train performance, which is not conducive to improving the line transportation efficiency. The fixed block speed code mode ATC is based on the ordinary audio track circuit. The track circuit transmits a small amount of information. Corresponding to each blocked area, only one information code can be transmitted. The control mode can be divided into two types: entrance control and exit control. Can be divided into two kinds of insulated and non-insulated track circuits.
Taking the export protection mode as an example, the information transmitted by the track circuit is the exit speed command code specified by the section. When the exit speed of the train is greater than the speed specified by the exit command code of this section, the onboard equipment is implemented on the train. Punishment braking to ensure the safety of train operations. Because the train monitoring adopts the export inspection method, in order to ensure the safe tracking and operation of the train, a complete block is needed as the safety protection distance of the train, which limits the further improvement and exertion of the line passing capacity. Companies that can provide such products include: UK WSL Corporation, American GRS Corporation, French ALSTOM Corporation, German SIEMENZ Corporation, etc.
2.6 Target Distance Code Mode (curve type)
The target distance code mode generally uses an audio digital track circuit or an audio track circuit plus a cable loop or an audio track circuit plus a transponder, and has a large amount of information transmission and a strong anti-interference ability. Through the audio digital track circuit sending device or transponder to provide information such as target speed, target distance, line status (curve radius, ramp, etc.) to the onboard equipment, the onboard equipment calculates a target suitable for train operation in conjunction with fixed vehicle performance data. The distance speed pattern curve (which eventually forms a curve control method) ensures that the train runs in order under the target distance speed pattern curve. Not only enhances the comfort of train operation, but also shortens the minimum safety interval for train tracking operation to a safety distance, which is conducive to improving the passing ability of the line. Such as Shanghai Metro Line 2 USS company introduced the United States, France ALSTOM company to introduce the Pearl Line and Guangzhou Metro Line 1, Line 2 introduction of the German company Siemens ATC systems fall into this category.
3 Mobile Occlusion ATC System
The ATC system of the mobile blocking method usually uses media such as wireless communications, ground cross sensing loops, and waveguides to transmit information to the train-controlled vehicle equipment. The train safety interval distance is calculated based on the maximum allowable vehicle speed, current parking point position, and line information. The information is updated cyclically to ensure that the train receives the instantaneous information without interruption.
The mobile occlusion ATC system is a two-way data communication device between the train and the ground , so that the ground signal device can obtain the continuous position information of each train, and calculate the operating permission of each train from this, dynamically update and send it to the train. Received operating authority and its own operating status, calculated the speed curve of the train running, to achieve accurate fixed-point parking, to achieve a fully protected train two-way operation mode, more conducive to the full use of the line through the ability to.
The mobile ATC system has not yet been applied in China. Foreign companies that can provide such systems include Alcatel’s ATC system with cross sensing cables as the transmission medium, and applications such as the “Ceche Line†in Vancouver, Canada, and the KCRC Western Railway in Hong Kong . The technology is relatively mature, but the cable between the cross-induction rails brings inconvenience to the daily maintenance of the line; the Harmonics mobile blocking application based on spread-spectrum radio communication is applied to the BART line in San Francisco , and its system structure and system application are not yet mature; Alstom The company's mobile obstruction based on waveguide transmission information is being installed and debugged in the test section of the northwestern Singapore line.
3.1 Signal System Basic Functions
3.1.1 Automatic train monitoring subsystem
The ATS system consists of a control center, a station, a parking lot, and on-board equipment. The ATS system completes automatic monitoring of train operations with the support of the ATP system and achieves the following basic functions:
( 1 ) Through ATS station equipment, it is possible to collect and track and control the basic information of train operations, such as track occupancy status, route status, train operation status, and signal equipment failure provided by on-track and on-board ATP .
( 2 ) According to the interlock table, the plan operation diagram and the train position, an output route control command is automatically generated, transmitted to the station interlocking device, and the train route and the train stop time are set.
( 3 ) Train identification tracking, transmission and display functions. The system can automatically complete the tracking of the train identification number (service number, destination number, and body number) in the mainline section. The train identification number can be automatically generated by the central ATS or manually set and modified by the dispatcher, and can also be transported by train to the ground. The communication sends information such as an identification number to the ATS .
( 4 ) Comparison of train plans and real-time operating charts and computer-aided dispatching functions. According to the actual deviation of the train operation, the adjustment plan can be automatically generated for the dispatcher to refer to or automatically adjust the train stop time and control the departure time.
( 5 ) In the case of degraded processing in the ATS central failure situation, the dispatcher manually intervenes to set the approach and adjusts the train operation. The ATS station completes the automatic approach or automatic signal control based on the train identification number, and the station manually enters the route. control.
( 6 ) Compilation and management of basic train diagrams of trains are completed under computer assistance and have strong human intervention capabilities. Through the terminal located in the depot, it provides vehicle depot management and traffic personnel with necessary information for the preparation of vehicle operation plans and driving plans.
( 7 ) The train running display screen and the dispatcher's display can monitor the track section, turnouts, traffic signals, and on-line trains, and can provide equipment failure alarms and fault source prompts on the work station.
( 8 ) It can provide simulation and demonstration functions on the central special equipment for training and visits. Can automatically run the report statistics, and display and print as required.
( 9 ) Combine with computer interlocking equipment in station control mode to place some or all of the signals in automatic mode.
( 10 ) Provide necessary information to the communication wireless, broadcast, and passenger guidance systems.
3.1.2 Train Automatic Protection Subsystem ( ATP )
The ATP system is composed of ground equipment and on-board equipment. It supervises trains to run at a safe speed to ensure that once the train exceeds the prescribed speed, the brakes are immediately applied to implement the following functions:
( 1 ) Automatically continuously detect the position of the train and send the necessary information such as speed, distance, and line conditions to the train to determine the maximum safe speed of the train. Provides train speed protection, provides common braking or emergency braking when the train is overspeed, guarantees the safety interval between the preceding and following trains, and meets the design driving interval and return interval during forward driving. ATP protection can be applied to trains operating in the reverse direction .
( 2 ) Ensure that the train is correctly approaching and the train is running safely. Ensure that there is a sufficient safety distance between different trains on the same track, and wait to prevent the side of the train from colliding.
( 3 ) Preventing the train from running at a high speed and ensuring that the speed of the train does not exceed the allowable speed specified by the line, turnout, and vehicles.
( 4 ) Provide safe and reliable information for the opening of train doors.
( 5 ) Determine the direction of code transmission of the corresponding track circuit according to the running direction of the on-track section provided by the interlocking equipment.
( 6 ) Any vehicle-to-ground communication disruption and unintended movement of the train (including degeneracy), interruption of any train integrity circuit, train overspeed (including temporary speed limit), onboard equipment failure, etc. will all produce a safety brake.
( 7 ) Realize the interface with ATS and related exchange information.
( 8 ) System self-diagnosis, fault alarm, and record.
( 9 ) Record and display information such as actual speed, recommended speed, target speed, and target distance of the train. With manual or automatic wheel wear compensation.
3.1.3 Automatic Train Subsystem ( ATO )
The ATO subsystem is a device that controls the automatic operation of trains. It is composed of on-board equipment and ground equipment. Under the protection of the ATP system, automatic operation of the train operation, automatic speed adjustment, and train door control are implemented according to the ATS instructions.
( 1 ) Automatically complete the control of starting, towing, cruising, coasting, and braking of the train, tracking operations and folding operations at a higher speed, ensuring that the design interval and travel speed are achieved.
( 2 ) Car-to-ground communication is carried out at the entrance of the ATS monitoring area and in the parking areas of each station (including the return line and the parking line), and the relevant information of the train is transmitted to the ATS system so that the ATS system can monitor the online train.
( 3 ) Control the train to run according to the operation diagram, achieve the purpose of energy saving and automatic adjustment of the train operation.
( 4 ) When the ATO autopilots, it achieves fixed stop control, comfort control and energy saving control at the station platform.
( 5 ) The door can be automatically controlled according to the position of the parking platform and the parking accuracy.
( 6 ) Combine with ATS and ATP to achieve automatic train driving, manned or unmanned driving.
3.2 Signal System Operation Mode
1 , ATS automatic monitoring mode
Under normal circumstances, the ATS system automatically monitors the operation of the online train, and automatically delivers the train route command to the interlocking equipment. Under the safety protection of the ATP , the train is driven by the driver according to the specified operation schedule. Control center traffic dispatchers only need to supervise the running status of trains and equipment. Before the class starts every day, the dispatcher of the control center selects the driving chart / timetable of the day and confirms or makes necessary modifications as the basis of the driving command on the day.
2 , dispatcher manual intervention mode
The dispatcher can issue relevant driving orders through the workstations to manually intervene on the entire train operation. Adjusting the train operation plan includes implementing “deductionâ€, “stopping the station stopâ€, changing train access, and increasing or decreasing trains.
3 , the train entering and leaving the yard scheduling mode
The vehicle dispatcher compiles the vehicle operation plan and on-site driving plan based on the train chart / timetable of the day and transmits it to the control center. The depot signal attendant sets the appropriate approach according to the vehicle operation plan to meet the requirements of the train entry and exit sections.
4 , the