| The wheel/rail traffic system in which linear induction motor (LIM) trains operate is powered by linear motors, and the trains are still supported and oriented by wheel/rail systems. It is so called LIM wheel/rail system. This traffic system has the better terrain adaptability due to the good capacity of gradeability, the ability to pass over sharp curves and demand of small tunnel section, particularly suitable for application in the modern cities with constrained underground resources, crowed buildings and large terrain variation. Moreover, the traction and the braking force are produced by the interaction between the linear motor stators (induction coil) installed on the bogies and the reaction plate (rotor) laying on the track, which can significantly alleviate the damage on the surface of wheel and rail. It is a new form of wheel/rail traffic system, and will have a wide application prospect. But, it also has many problems waiting for further solution.The LIM wheel/rail traffic system has the typical feature that the air gap (8-12mm normally) between the induction coil hung under bogie and the reaction plate fixed on track board is changing randomly when the train operates. The characteristics of track, the variation of wheel and rail profiles and the mounting tolerances of the reaction plates have effects on the size of the air gap, which directly affects the traction efficiency of the LIM and the coupling dynamic characteristics of the vehicle-track system, or even cause scratches between the induction coils and reaction plates, which endangers the traffic safety. Particularly, the LIM wheel/rail traffic system has unique dynamic performances due to the interaction between wheel/rail relation and the induction-coil/reaction-plate relation. Therefore, the investigation into the coupling dynamic interaction mechanism of the LIM metro vehicle-track system has the important theoretical significance and engineering application value for the stability, comfort and safety of the operating vehicles, as well as the structural design and optimization of the vehicle/track, and thier maintenances.This paper work is supported by the National Science Foundation of China (No. 51105318), Innovation Team of Education Department (No. IRT1178, No. SWJTU12ZT01) and Sichuan Province Science and Technology Support program (No.2011GZ0090). The main research contents of this paper are shown as follows:(1) Based on the railway vehicle-track coupling dynamic theory, a system dynamic model of a LIM metro vehicle coupled with a slab track is established to research the curving performance of the LIM metro vehicle. And also this research carrys out an invetgation into the influence of the geometry state of wheel/rail on the LIM vehicle dynamic performance as well as the impact of reaction plate mounting tolerances on the LIM vehicle service performance.(2) In the dynamic model, multi body system (MBS) is used to simulate the railway vehicle system, which consists of 1 carbody,2 bogie frames,4 wheelsets and 2 induction coils of electric motors. The induction coil is simulated by the Eular beam, which is connected to the bogie frame with equivalent linear spring-damper elements. The track system is considered as a flexible structure system, which included rails, reaction plates and slabs. The rail and the reaction plate are, respectively, modeled by using discretely supported Euler beams, and the slab is modelled with 3D solid elements. The equivalent linear spring-damper elements are used to simulate the fasteners between the rail and the slab, the connections between the reaction plate and the slab, the slab and the subgrate.(3) In order to understand the curving performance of the LIM metro vehicle, a complete dynamic electrical-mechanical subsystem model is established, including modeling the interaction of the induction coil and the reaction plate, which has been not founf to be reported in the previous researches. Also the present model considers the effect of the air-gap variation of the liniear induction motor on its electromagnetic force, due to the excitations of the wheel/rail irregularities (wavy wheel polygons, rail corrugation and weld geometric irregularity), when the vehicle operates.(4) The paper has a discussion on the effect of the mounting tolerance of the reaction plate on the dynamic behavior of the vehicle and the track. As a critical indicator, the mounting tolerance effect of the reaction plate was not considered in the previous research on the LIM vehicle-track coupling dynamic system.The following four aspects are in detail investigated by using the LIM metro vehicles-slab track coupling system dynamic model.(1) Study on the curving dynamic behavior of the linear motor metro vehicle. Using the present model analyzes the wheel-rail interaction force, the electromagnetic force of the LIM, and the air gap variation of the LIM, and the effect of the curved track radius, the vehicle speed, the superelevation of outer rail, the gauge widening and other parameters on the curving dynamic behavior of the linear motor metro vehicle. It is found that the characteristics of the motor air gap variation and the vehicle curving dynamic performance. The results can be used as the guidance about for the parameters design and optimization of the urved track for the LIM trains operation and the maintenance of the reaction plates.(2) Analysis on the effects of wheel/rail geometry state on the dynamic behavior of the linear motor metro vehicle. The relationship between the mileage and the wear loss is emphatically analyzed, combining with the wheel-rail wear data measured from the sites, and the wear characteristics of the linear motor vehicle wheel tread and the rail are obtained. It is found that, after a certain mileage of the vehicle operation, the concave wear occurred on the wheel tread, and rail angle wear generated, the wear increased with the increasing of running mileage. The analysis considers the effect of the wheel wear and the rail wear on the dynamic behavior of the linear motor vehicle in both the straight and curve segments at different running speeds, with the combination of two kinds of wheel-rail surface states:the worn wheel and the standard rail, and the standard wheel and the worn rail. The analysed dynamic behavior index includes the wheel-rail interaction forces, the wheelset acceleration, the air-gap variation, the derailment coefficient, the rate of wheel load reduction, etc.(3) Investigation into the effects of the wheel/rail longitudinal geometry state on the dynamic behavior of the linear motor vehicle. Combining with the measured data of wheel out of roundness, rail welding joint irregularity and rail corrugation, the present work conducts an investigation into the effects of the wheel out of roundness, the rail welding joint irregularity and the rail corrugation on the dynamic behavior of the linear motor vehicle in a straight line section at different vehicle speeds. The investigated dynamic behavior index includes the wheel-rail interaction forces, the wheelset acceleration, the air-gap variation, the derailment coefficient, the rate of wheel load reduction, etc.(4) Discussions on the effects of the mounting tolerance of the induction plate on the dynamic behavior of the inear motor metro vehicle.1) Effects of the mounting tolerance variation of the induction plate on the dynamic behavior of the linear motor vehicle at different speeds without track irregularity excitation.2) Effects of the mounting tolerance variation of the induction plate on the dynamic behavior of the linear motor vehicle at different speeds according to the measured rail welding joint irregularity data.3) Effects of the mounting tolerance variation of the induction plate on the dynamic behavior of the linear motor vehicle at different speeds according to the measured rail corrugation data. The discussed dynamic indexes are the same as the previous. This paper proposes the suggestions to control the geometrical irregularities at the rail welding joints and the rail corrugation amplitudes in the maintenance work. |
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