The Implementation Of A Measuring Instrument For Velocity Of High Temperature Superconducting Maglev Vehicle

While high temperature superconducting maglev vehicle is going at high speed, as one of the bases of control , the velocity must be real-timely detected. So the design of the speed detectors is explained in the paper.At first, according to the environment of the vehicle running, the photoelectric testing is chosen after the analysis of many methods. It is a very effective test method because not only the interference of sensor in the strong magnetic field is shielded, but also it is real-time by the light high-speed travelling on measuring.Four projects of testing and their overall structure designs are pointed out. Considering the cost of design, the device on the vehicle is realized by reflection rays of infrared led or laser mounted on it, and the device on the ground is achieved by radiation rays of infrared led or laser mounted on the vehicle. It is faster for testing signals into pulse signals than into digital signals, suitable for low-consumption, low-cost and small size design.The device on the vehicle is composed of power, sensor board, the main board and communication board. As the component of sensor board, the silicon photoelectric cell transforms radiation-ray from the track mark into electrical signal, which is amplified by operation amplifier into voltage signal reshaped by the pulse shaping circuit. The pulse signals are measured into speed value by the main board. The communication board expands single-chip microcomputer's Universal Asynchronous Receiver-Transmitter (UART) to three UARTs for communication interfaces such as RS232, wireless and 485 buses to exchange data between system and peripherals. The communication of system is based on the service procedure of UART interruption, which drives the chip of expanding UART.The device on the ground is composed of power, array of sensors, the main board and communication board, yet the light source is mounted on the vehicle .As photoelectric switch lain along with the track, the photoelectric triode transforms radiation-ray from the vehicle into high voltage signal reshaped by the pulse shaping circuit in the main board. So far as the pulse measurement is concerned, the main board on the ground is similar to the main board on the vehicle .Additionally, compared to the communications board on the vehicle, there is a little difference about the design of thecommunications board on the ground.The software is composed of modules such as the dynamic display, pulse counting and pulse capture and communications of system. The module of dynamic display is used for refreshing speed value. Both of models to measure speed are realized in the software. One is pulse counting, the other is pulse capture.While the whole system is debugged, it is working well. The effective distance of measuring device on vehicle is from 5mm to 25mm. Through the simulation tests, if the space of track mark is 0. lm, the instrument can measure the speed ranged from 0 to 600km/h with an accuracy of ±0. lm/s.