Study On Effects Of The Gap Between LIM And RP And Track Irregularity On System Dynamic Response For Linear Metro

:The linear metro vehicle is powered by linear induction motors (LIMs), supported and oriented by wheels. The propulsion and braking of vehicles are provided by the vehicle-borne LIMs which interact, through an air gap, with the LIM reaction plate (RP) fixed on the track system and runs parallel to the running rails. The efficient function of a LIM requires the air gap between the LIM and its RP to be maintained a certain proper distance, normally ranging from 8mm and 12mm. Track irregularities and the variety of the height of the RP have great influence on the air gap between LIM and RP. Therefore, an investigation into the alteration characteristics of the air gap and the track irregularity condition of an operating linear metro line, and an analysis of the vehicle-track system vibration, based on the measured data is of great significance.In this study, Firstly, the static and dynamic alteration characteristics, statistical characteristics and the track irregularity condition are analyzed, based on the air gap and track irregularity measured Guangzhou Metro Line 4. Then, by means of the dynamic model developed in the research, the effects of the air gap and track irregularity on the dynamic responses of the LIM vehicle-track system are examined. Finally, the reasonable gap between the carriage and platform edge of linear metro station is discussed.The main contents of the presented paper are as follows.(1) Based on the static measured data of the height of the RP of Guangzhou Metro Line 4, the alteration characteristics of the RP are obtained and the resulting reason is discussed.(2) Based on the dynamic measured data of the air gap between LIM and RP of Guangzhou Metro Line 4, the alteration characteristics, statistical characteristics and frequency domain characteristics of the air gap are obtained. Compared with the static measured data, a measuring method combining the static and dynamic measuring method for the air gap are proposed.(3) Based on the measured data of track irregularities of Guangzhou Metro Line 4, the track irregularity status and quality are obtained. The results show that, the track irregularity is maintained on good condition. All the peaks of the geometric vertical irregularities are under the limit value of Grade one (12mm), which demonstrates the changing caused by track irregularities can be effectively controlled. The comparison of the track irregular profiles of Guangzhou Metro Line 4 and of FRA Track Classes 4,5 and 6 shows that, the track irregular peak of Guangzhou Metro Line 4 is close to that of FRA Track Classes 5, and the Track Quality Index (TQI) of f Guangzhou Metro Line 4 is better than that of FRA Track Classes 6.(4) By means of the dynamic model, the effects of the air gap and track irregularity on the dynamic responses of straight sections are examined, and the frequency domain characteristics of vehicle-track vibration are analyzed. The results show that, the vertical electromagnetic force has little influence on the vibration displacement of track structures and car body acceleration, however has great influence on the vibration acceleration of track structures, and the influence of the vertical electromagnetic force on wheel/track force is within 10kN. The limit value of the vertical irregular peak is proposed. From a security point of view, the vertical irregular peak should be control under 12mm, and for the work efficiency of LIM motor the value should be control under 4mm.(5) By means of the dynamic model, the effects of the air gap and track irregularity on the dynamic responses of curved sections and the curving performance of LIM vehicle are examined. Based on the analysis, a Theoretical formula of the alteration of the air gap is presented, which can be used to analyze the effects of alignment parameters on the air gap.(6) By means of the dynamic model, the reasonable gap between the carriage and platform edge of linear metro station is discussed. The results show that, in the straight section, the present gap applied in Guangzhou Line 4 can be reduced about 20-25 mm, set as 75-80mm; in the curved section, the present gap can be reduced about 15 mm and the curve radius on curved platform should be 1000m. the proposed method for computing vehicle gauge can accurately evaluate the dynamic lateral movement of the vehicle, which provide a more reliable basis for selecting the reasonable gap between the vehicle and platform accordingly.