Research On The Position And Speed Measurement System Based On Light Source Coding For Ultra High-speed Flying Train

Flying train is a future transportation with broad application prospects,which runs in the near vacuum pipeline and uses the maglev technology,to make the speed reach more than 1000 km/h.The position and velocity measurement device can furnish the fundamental position,velocity and different data for the operation-control and traction machine of the flight train,to make sure safety.However,the existing position and speed measurement technologies can not well adapt to flying train’s special working conditions such as ultra-high speed,strong magnetic field and near vacuum.So,the author’s group,entrusted by China Aerospace Science and Industry Corporation,proposes a new position and speed measurement scheme based on principles of optics and suitable for the flying train in the future.Considering the special working conditions of the flying train,a highly real-time and strong anti-electromagnetic interference capability absolute position and speed measurement system is proposed in this paper,which mainly includes the absolute position coding light source installed on the train and the signal receiving modules arranged on the running line.Around this system,the following works have been carried out.1.In terms of the system scheme,for improving the reliability and realizing multiple redundancy,multiple sets of light sources are installed on the train to ensure that receiving modules can receive more than one set of coding information during operation.In order to provide the evaluation index for the experiments,the whole line measurement,positioning accuracy and other issues are analyzed in detail,and the index calculation models are abstracted.2.In terms of coding,Manchester code is used to make the m-sequence code with synchronous code track become the absolute position code of true single code track.On this basis,in order to ensure the accurate code reading of the processor,two synchronous trigger reading mechanisms based on the edge and level are proposed and verified by functional simulation.3.In terms of hardware,(1)the noise equivalent model of each component of the photoelectric detection circuit is established respectively,and the output noise is calculated based on this model.Then the feature relation of the whole output noise of the circuit affected via a range of parameters is acquired in accordance to the cascade effect.According to this function relation,a low-noise photoelectric detection circuit sensitive to weak light signal is established.(2)on the basis of the multiple redundancy mechanism,a FPGA decoding circuit is designed to obtain the absolute position by looking up the ROM table.In addition,by observing the response of photoelectric detection circuit detecting high frequency modulated optical signal,the system’s adaptability in high-speed operation is verified.4.In terms of security,the FPGA fault diagnosis algorithm is designed independently to improve the self-checking ability of the system.Finally,the experimental platform of rail vehicle is constructed to affirm the key techniques of software and hardware of the proposed position and velocity measurement scheme.The precision of the proposed system approaches 20 mm in the position measurement of the rail vehicle,and it has a certain ability to resist the interferences of the train gesture changes.The independently designed fault diagnosis algorithm can correctly detect the damage on the receiving module and its lens.The experimental results show that the proposed position and speed measurement system based on laser coding has many advantages,including the signal transmission using fibre-optical,high-precision absolute position information measurement and multiple redundant reliable measurement,which can be applied to the flying train.