Study On Irregularity Measurement System For High-speed Maglev Track

The "National Comprehensive Three-dimensional Transportation Network Planning Outline" proposes to study and promote the planning of high-speed maglev layout between mega-cities and test line construction,so that the construction of high-speed maglev trunk lines is ready in China,and the train operating speed will be increased to600km/h or higher.The geometric state of maglev track directly affects the stability,safety and comfort of train operation,so the importance and urgency of long-distance maglev track inspection and maintenance are gradually become prominent.However,because the high-speed maglev has not been applied widely in the past 20 years,relevant researches mainly focus on the vehicle system,while few researches on track inspection and maintenance.Moreover,the high-speed maglev track is a long stator primary of synchronous linear traction motor,which is very different from the track of traditional wheel-rail system,and the speed of maglev train is higher,so the relevant research results of wheel-rail system can not be directly applied.In order to meet the urgent needs of track inspection for the development of high-speed maglev,this paper invented a high-speed maglev track irregularity measurement system,and studied the signal processing and mileage detection methods,aiming to make technical reserves for the implementation of long trunk lines in the future.The main research contents are as follows:The structural characteristics,irregularity and its calculation method of high-speed maglev track are studied,and the differences between the track irregularities of the highspeed maglev and that of the wheel-rail system is compared and analyzed.It is pointed out that the high-speed maglev track irregularity includes vertical irregularity and guidance irregularity,which is characterized by the combination of segmented straightlines.It is mainly manifested in four forms: long wave irregularity,short wave irregularity,slope-change and dislocation.A calculation method of determining the long wave irregularity by calculating the end coordinates of track beam by spatial straight line fitting is proposed,which is used to quantitatively evaluate the track smoothness.A high-speed maglev track irregularity measurement method with measuring equipment mounted on operating trains is studied,and the measurement signal fusion processing flow based on the inertial reference method,the mileage detection method suitable for the onboard independent operation,and the auxiliary strategy to ensure the accuracy of irregularity measurement are proposed.Among them,for the irregularity measurement accuracy and its auxiliary strategy,the maximum error introduced in the case of sensor installation dislocation and guidance irregularity measurement without gyroscope is simulated and analyzed.An auxiliary strategy based on track design alignment is proposed,and the alignment design data is directly used as the low-frequency component of carrier attitude to ensure the measurement accuracy;In view of the special case of non-gyroscope in the guidance irregularity measurement,based on the above strategy and using the characteristics of segmented straight-line combination of track irregularity,a smoothing method based on segmented straight line fitting is proposed to reduce the influence of the the high-frequency component of carrier attitude on the meansurement accuracy of guidance irregularity;For mileage detection,a non-contact mileage measurement and positioning method combining a relative position sensor and an absolute positioning sensor is proposed,which makes full use of the characteristics of high-speed maglev track’s stator cogging structure and positioning marker plate laid along the line;In addition,a new method of mileage deviation correction is proposed,which combines the mileage reference points obtained by the absolute positioning sensor and track joint recognition,and groups the mileage data according to the beam span length to make the deviation correction respectively.The signal processing method of high-speed maglev track irregularity measurement is studied.Aiming at the the measured value mutation of the displacement meter caused by the track joint,clearance of functional parts and stator cogging structure,an adaptive threshold denoising algorithm based on improved empirical mode decomposition is proposed.The algorithm can remove the measurement noise of the displacement meter and retain the track joint characteristic data for mileage correction.At the same time,according to the requirements of 200 m long wave irregularity measurement,a spatial filter with low cut-off frequency,narrow transition bandwidth and low computational complexity is designed based on interpolation impulse response technology and coefficient sparse design method,and the simulation results meet the measurement requirements.An onboard high-speed maglev track irregularity measurement system and two compact mileage sensors,the composite relative position sensor and the eddy current reflection type absolute positioning sensor,are invented.The system adopts a split structure design,and the two measurement equipment are respectively installed at the front end of the suspension electromagnet on both sides of the head vehicle’s end.They run with the train and can independently supply power and detect mileage.The relative position sensor combines a set of electromagnetic induction coils and two photoelectric switches to obtain mileage,speed and direction by recognizing the stator cogging and the outside cable.The absolute positioning sensor uses photoelectric switch to provide trigger for reading the positioning marker plate on the track side,and four sets of electromagnetic induction coils simultaneously read the four-digit mileage code value of the marker plate based on the principle of eddy current reflection.The combination of the two sensors realizes mileage detection and meets the requirements of the onboard track irregularity measurement system.Based on the above,the irregularity measurement simulation experiment and line experiment were carried out,experiments verify the effectiveness of the irregularity processing algorithm and the accuracy of the system.The detection wavelength can reach200 m and the irregularity measurement accuracy can reach 0.5mm.The performance tests of relative position sensor and absolute positioning sensor were also carried out,both positiong sensors can adapt to the running speed of 200km/h,and their performance is not affected by vehicle suspension,guidance fluctuation and attitude change,indicating that they meet the requirements of on-board system for mileage detection.