Passenger train fully automatic station announcement multimedia system

0 Introduction

During the journey, passengers are very concerned about the next station of the train to avoid missing the station. Especially during night driving, the train broadcasting room stops broadcasting, and the conductor only announces the station name when the train arrives, which brings a lot of inconvenience to the majority of passengers. In order to enable passengers to know their current location and the next station in time. Here is a fully automatic station announcement multimedia system, which can automatically announce the station name and the train operation status all day long, and can play videos, songs and advertisements at ordinary times. Before the train arrives at the station, it automatically introduces the famous tourist attractions, transportation and accommodation conditions of each station in a sound and picture way, which greatly facilitates passengers, improves the riding environment, and also brings better economic benefits to railway transportation.

1 Control principle and system composition

The system consists of a bottom-level single-chip microcomputer system, an upper-level PC, a carriage broadcasting system, a display system, and corresponding software (see Figure 1). The single-chip microcomputer is the lower computer. The position sensor is placed at the door, and the door switch signal is used to correct the distance error. The signals of the speed and position sensors enable the single-chip microcomputer to effectively identify and process the train's mileage and door position, thereby outputting effective control signals to the upper-level PC through the serial port. The PC analyzes the sent signal, and if it is a mileage signal, the train's mileage is calculated. 10 kilometers before arrival, the video information of the corresponding station is called from the database, and after the divider and audio amplification, it is sent to the LCD display and broadcast of each carriage, and finally the information is broadcast to passengers in the form of multimedia. If it is a door opening signal, it means that the train has arrived at the station, then the audio information of the corresponding station is called from the database to broadcast the arrival information, and the mileage of the station from the departure station in the database is set as the current train mileage, thereby automatically correcting the errors caused by the speed sensor and train sliding. The night driving broadcast is automatically turned off, and the LCD display works as usual. The workflow of station announcement is shown in Figure 2.

Figure 1 System composition

Figure 2 Workflow of station announcements [page]

2. Low-Level Hardware Design

The underlying hardware system uses the 89C51 single-chip microcomputer as the controller (see Figure 3). The position sensor uses a proximity switch and is placed at the door. The speed sensor uses the HZL260 Hall gear sensor from Nanjing Zhongxu Company, which has the characteristics of high resolution and strong anti-interference ability and can be used in all-weather and large-scale areas in my country. The control of the divider and audio amplifier is achieved by using the interface circuit chip to control the switch of the solid-state relay using photoelectric isolation.

Figure 3. Bottom-level hardware system design

The measurement of the train's travel distance is based on recording the number of turns of the wheel. The HZL260 Hall gear sensor is a combination device that biases a permanent magnet behind the Hall device and integrates them with an amplification processing integrated circuit (see Figure 4). Its function is to convert the changing magnetic signal into a digital electrical signal. It can sense the number of teeth on the ferrous metal gear and convert it into a voltage pulse signal output. A gear is installed on the axle of the train, and the sensor is fixed at a position about 2mm away from the top of the tooth. When the wheel rotates one circle, the sensor outputs a pulse signal with the same number of gear teeth. The timer/counter 0 in the microcontroller counts it, and the number of turns of the wheel can be detected, thereby calculating the mileage of the train.

Figure 4 HZL260 Hall gear sensor

3 Software Design

3.1 Low-level software design
The MCU generates a counter overflow interrupt every time the train travels 1 km. Every time the door opens at a station, an external interrupt is generated. After the MCU responds to the interrupt, it sends a message to the upper-level PC through the serial port. The program flow chart is shown in Figure 5.

Figure 5 MCU program flow chart

3.2 Upper-layer software design
3.2.1 Upper-layer software composition
The upper-layer software can be divided into five sub-modules according to different functions (see Figure 6).

Figure 6 Structure of upper-layer software[page]

1) Communication module: responsible for communication with the underlying hardware system, receiving uploaded data, and transmitting control instructions;
2) Database access module: completes access to the database and calls relevant information of each station;
3) Multimedia playback module: responsible for playing multimedia files and broadcasting information to passengers through video and audio;
4) Console management module: accepts input from managers and is responsible for the management of system software and hardware;
5) Transaction processing and scheduling module: processes data and coordinates the mutual processes of each submodule.
When data is uploaded to the underlying layer, the communication module receives the data and hands it over to the transaction processing and scheduling module. After analyzing the meaning of the data (such as determining that the train has arrived at the station), the transaction processing and scheduling module calls the database access module, searches for relevant information in the database and reads it in, then calls the multimedia playback module to play video and audio files, introduces the information of the station to be arrived to passengers in the form of sound and picture, and reports the train operation status from time to time.
3.2.2 Database design
In order to facilitate the organization and management of data, the station information is stored in the database, and the database is accessed through ADO technology, which is easy to use, fast, low in memory expenditure and small in disk footprint. Use Access to build a relational database, including train schedule and station information table. The train schedule (see Table 1) records the train number, station name, arrival time, departure time and mileage information. Since different trains may pass through the same station, the video files and audio files of each station are stored in the station information table (see Table 2). The video file is played when the train is about to arrive at the station, mainly introducing the tourist attractions, transportation and accommodation conditions of the station, and the audio file is the announcement of the station name.

When the train arrives at a station, the transaction processing and dispatching module first determines the station name arrived by comparing the train mileage with the mileage in Table 1 in the database, and then retrieves the video and audio files corresponding to the station name from Table 2 for playback.
Figure 7 is the software interface of the fully automatic station announcement system when the T8 train is about to arrive in Mianyang.

Figure 7 Upper software interface

4 Conclusion

The fully automatic train station announcement multimedia system uses the underlying single-chip system as the detection unit, the upper microcomputer as the data processing unit, and combines database and multimedia technology to remind passengers. It has opened up a new field for railway information services, greatly facilitated passengers, reduced the workload of train attendants, and eliminated the phenomenon of wrong reporting and missed reporting of stations. It is the development direction of train station announcements.

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