Abstract : With the continuous development of rail transit and the increasing number of subway vehicles deployed year by year, the performance and safety issues of subway trains in operation have attracted great attention from subway vehicle operators at home and abroad. Installing subway vehicle operation recorders on subway vehicles has become essential. This article introduces a new technology—a non-contact detection method—and its application in current domestic subway vehicles. Keywords : Subway vehicle; Hall sensor; Non-contact detection; Recorder 1 Overview Due to differences in design standards and manufacturing processes among various subway vehicle manufacturers, coupled with differences in production eras, electromagnetic interference between subway vehicles and the subway system is unavoidable. Severe interference can cause subway vehicle malfunctions and accidents, resulting in certain economic losses. Simultaneously, the electromechanical and signaling equipment of the subway vehicles themselves are also susceptible to malfunctions due to changes in the natural environment, affecting the quality and aging of components. Furthermore, improper human operation can also cause subway vehicle malfunctions and accidents. All these malfunctions require a complete, real-time subway vehicle operation recorder to scientifically analyze and collect evidence of the subway vehicle's operational status, thereby arriving at reasonable and accurate conclusions. Especially after a major accident, the subway vehicle operation recorder has certain legal reference value (requiring certification by relevant authoritative institutions). It can comprehensively record relevant information about vehicle operation, such as recording all triggered states and parameters during continuous changes within 20 hours. Currently, most subway trains in operation in China are not equipped with subway vehicle operation recorders. In the event of a major malfunction or accident, the driver can press the emergency button (emergency button). At this time, the relevant key information is "permanently" recorded in the memory of the subway vehicle's computer control unit. The stored information is brief, partial, and limited to a few minutes before and after the incident, and cannot record complete data about the train, such as the driver's working situation at the time: manual operation positions, various buttons, indicator lights, circuit breakers, switches, and equipment I/O, etc. This brings certain difficulties to the analysis of malfunctions and accidents. Currently, subway vehicle operators at home and abroad attach great importance to this, believing that installing subway vehicle operation recorders on subway vehicles will help improve the level of scientific management and accurately assess the performance of subway vehicle equipment and the true cause of accidents. Abroad, the installation of operation recorders on subway vehicles is a new concept proposed in the 1990s. It was reported that in 1999, the Institute of Electrical and Electronics Engineers (IEEE) specifically described subway vehicle operation recorders in a relevant technical document. For example, German expert W. Jochim suggested that the operation recorder should record the following four types of data: (1) the status of the onboard equipment of the corresponding signal system, such as whether the equipment is connected, fault conditions, etc. (2) the status of the corresponding train, such as which driver's console is used, shift change time, etc. (3) real-time information on train operation, such as time, distance traveled, speed, etc. (4) information related to the operation and monitoring process, such as door opening and closing, service braking, emergency braking, etc. In response to these suggestions, engineering and technical personnel in relevant countries began to study this aspect. For example, the KW R6 operation recorder designed by the German company DEVAT is based on the development of new vehicles and uses network principles to collect various signals from the vehicle. The development costs for both software and hardware are relatively high, making it unsuitable for retrofitting existing vehicles. In China, there is no precedent for this application in either newly designed or currently used vehicles. This design scheme is a bold concept developed through research. After joint discussions with Beijing Ximahong Instrument Co., Ltd. and Shanghai Zhanji Technology Development Co., Ltd., and after testing, its feasibility has been proven. The developed vehicle operation recorder is practical and economical. 2. Design of the Vehicle Operation Recorder Generally, recorders collect parameters such as voltage, current, pressure, and temperature. Voltage and current are the most frequently collected parameters. These are measured using transformer units (which can only measure 50 Hz sinusoidal AC) and shunt units (the measured signal cannot be isolated). However, these sensors no longer meet the higher requirements of modern electronic measurement technology in terms of measurement accuracy, medium and high frequencies, and response time. For example, they are insufficient for measuring 0-100 Hz AC/DC voltage, current signals, switching signals, and any waveform. If we want to update or modify existing equipment (such as subway cars, industrial inverters, etc.), it is absolutely impossible to use traditional measurement methods (each measured signal needs to be installed, removed, and the wires of the measured signal need to be modified), and such project modifications are extremely risky. Therefore, we must apply advanced measurement methods that not only meet the design and required measurement requirements, but also are risk-free and meet the technical reliability requirements. We use digital ID encoding technology, advanced power semiconductor electronic devices, and computer hardware and software to develop this system. 2.1 Design Principles According to the principles of electromagnetic fields, when AC or DC current flows through a conductor, an alternating, permanent electromagnetic field is generated around it, and the magnitude of the electromagnetic field is proportional to the current flowing through it. By utilizing the changes in the electromagnetic field, we can detect changes in current and voltage. 2.1.1 Selection of Hall Sensor The GUN3033 Hall sensor chip has superior electrical performance and is a new generation of electronic control circuit detection element that can be isolated from the main circuit circuit being measured, combining all the advantages of traditional sensors. It can measure not only AC and DC signals, but also instantaneous peak signals. It boasts strong overload capacity and a wide measurement range, and is particularly reliable for monitoring and detecting large currents. It is widely used in industrial inverters, medical AC frequency converters, vehicle testing, and proximity detection. 2.1.2 Selection of the Encoder/Decoder: The UM 3758108 is an integrated transceiver chip, serving as the digital communication interface. It features long-distance (up to several kilometers) communication capabilities, enabling point-to-multipoint information transmission. It offers high reliability and strong anti-interference capabilities, and is widely used in defense communications and industrial automation control. Its most significant feature is that communication between transceiver modules can be completed without software protocols, with a maximum addressing capability of 1024, thus enabling 1024 monitoring points and saving on software and hardware development costs between the upper and lower units. 2.2 Digital Acquisition Unit Design The HW-1 digital acquisition unit uses the same UM 3758108 compiler-integrated transceiver chip. A CD4520 binary counter generates BCD codes to periodically change the address of the UM 3758108, addressing 1024 different ID sensors. Simultaneously, the computer is clocked to achieve address and clock synchronization. 2.3 ID Sensor Design We modularized the GUN3033 Hall sensor chip, the UM 3758108 compiler-integrated transceiver chip, and the IC, developing analog and digital ID sensors. The analog ID sensor uses an A/D converter, and the digital ID sensor uses a compiler. As shown in Figure 1, analog signals and switch signals are automatically detected, with their outputs controlled at: voltage 5V, current 20mA. The requirements for the detected signal source are: an electric field strength of ±6 Gs and a current of at least 5mA. 2.4 System Design Scheme A remote data acquisition system consisting of ID sensors, an HW-1 digital data acquisition unit, and a portable PC is shown in Figure 2. This is a scheme mainly applied to the retrofitting of existing subway trains, which differs significantly from network-based designs due to their higher costs. This design, however, has relatively low costs, high safety and reliability, and after debugging, basically meets the design requirements. It can also be applied to other fields. Analog or digital signals output from various sensors (voltage, current, pressure, temperature, etc.) enter the HW-1 digital data acquisition unit. The ID sensors and the HW-1 digital data acquisition unit are connected by a three-core shielded cable (positive, negative, and D digital line), with a transmission distance exceeding 1 km, transmitting the address code and data of each ID sensor. The ASCII characters "A" to "Z" are used for switch signal transmission, and "0" to "9" are used for analog signal transmission. The data is then transmitted to a portable computer (which the user can provide) via an RS232 serial interface. This system allows users to monitor the operating points of 100 devices, such as subway vehicles, recording the I/O operation points of various devices and up to a week's worth of data. The system is very easy to operate. This project is specifically designed for Shanghai Metro vehicles while also meeting the needs of other users. 2.5 Software Design The software development platform is the Win98 system, using communication controls from VB6 programming, and a specially developed ActiveX control. It can convert ASCII codes into binary codes and save them as a dynamic database file (Metro.db). This can be used to analyze the characteristics of each signal. For example, if the input value of the seven switch signals (ID01 to ID07) of a certain IC-01 encoder is "1000001" at a certain moment ("1" represents high level, "0" represents low level), the result will display the character "A" in the application software window. If we want to analyze the display of the ID01 sensor within 5 seconds, as shown in Figure 3, the application software data receiving window displays the five characters "ADFF3". We analyze the high or low levels of the first four switch signals and the last analog signal of the ID01 sensor, and display their curves through graphical software. 3. Project Application Introduction As shown in Figure 4, the subway vehicle operation recorder can detect various signals, such as position, buttons, indicator lights, switches, and equipment I/O. First, determine the detection nature (digital/analog) of the ID sensors at different addresses to facilitate addressing and data transmission of the HW-1 digital acquisition unit. Then, it starts working, sending information to the PC, where the application software completes data storage and establishes a dynamic database. 4. Conclusion The system design scheme of the subway vehicle operation recorder is unique and creative. At present, the development of operation recorders in China is still in its early stages, with each system having its own characteristics and methods for design requirements, and there are no standards to refer to. For subway vehicle operation recorders, their design must meet the requirements of vehicle operation, as well as reliability and cost-effectiveness. The various parameters of the operation recorder must be continuously improved to ultimately satisfy users. Therefore, the market prospects for subway vehicle operation recorders are limitless.