| Since 1997, totally six rounds of speed-up campaign have been conducted in our country to improve railway service capacity, ushering in a new era marked by a EMU speed of 300 to 350 km/h. Electric traction has many virtues such as low energy consumption, less pollution, traction, etc., so it is generally adopted in EMU. Usually, electric locomotive is powered through pantograph-catenary system, which are coupled as a pantograph system and catenary system by sliding contact. Pantograph moves with vehicle, sliding on catenary and carrying current. In the process, it is necessary to remain a constant contact pressure of 70N or so. Vibration amplitude of pantograph head and contact wire increases along with locomotive speed-up, and it may bring about pantograph contact pressure fluctuation, bad quality in current carrying, or in the worst way, contact line of catenary may be off the pantograph head, resulting in transient overvoltage which will do great harm to pantograph-catenary system and locomotive power system and badly affect safety in operation of the train. Therefore, it is of great significance to study the principles, methods and means of the pantograph-catenary system for maintaining a good pantograph-catenary vibration performance under high-speed operation conditions.There are many factors which may affect vibration performance of pantograph-catenary system, mainly involving structural parameters of pantograph & catenary arch and their interactions, such as catenary suspension stiffness, contact line slope, catenary suspension type, contact wire material, pantograph lifting force, contact wire uplift, contact wire pre-sag, skateboards material, pantograph imputed quality and locomotive speed, etc. Therefore, system performance could be improved mainly in two aspects, that is, pantograph and catenary. For example, it could be done by changing the type of catenary, increasing leads tension, reducing material density of contact line and pantograph, or optimizing pantograph size parameters. In China, most high-speed trains run on the existing railway lines whose catenary is built according to standards in effect, and any change to catenary type or parameters means huge cost for barely satisfactory optimization of pantograph parameters. In that case, active control, semi-active control technology should be introduced into the catenary system for improved current carrying performance.The thesis of principles and measures to improve performance of pantograph-catenary system in such a case that high-speed trains run on existing lines is mainly discussed. Therefore, a dynamical model of coupled pantograph-catenary system is established and simplified, and will be a basis for further research; a plan of raised pantograph rolling head is presented and the principles of its current carrying improvement is discussed; a semi-active control model of pantograph-catenary system based on semi-active control over pantograph is established, and the impact of semi-active control of pantograph-catenary system on its current carrying performance is studied; the impact of active control of pantograph-catenary on its current carrying performance is studied; a VR-based simulation platform of pantograph-catenary system using active control is established. The main contents are as follows:1. Establishment and simplification of a dynamical model of coupled pantograph-catenary system. With help of some relevant literatures, catenary components are simplified as beams, pantograph as mass-spring-damper structure, and a dynamical model of coupled pantograph-catenary system is given according to law of energy conservation. In order to facilitate research, catenary is simplified as a variable stiffness spring coupled with pantograph. Thus, the binary and ternary simplified dynamical models of coupled pantograph-catenary system are given.2. Semi-active control of pantograph based on semi-active control theory. Dynamical models of active & semi-active control of pantograph-catenary based on semi-active control over pantograph, and impacts on vibration performance of pantograph-catenary system are studied under control strategies such as sliding mode variable structure control, optimal control and fuzzy control.3. Research on MR damper-based semi-active control over pantograph. The dynamical model of MR damper is established, with it, the dynamic model of MR damper-based semi-active control over pantograph is given, and a computer simulation model of SIMULINK software based on fuzzy control strategy to study its impact on the performance of pantograph is also given.4. Characteristics of the rolling head of pantograph. Based on comprehensive analysis on pantograph-catenary contact force, the contact resistance theory, the impulse theory, friction, wear theory and other aspects is studied, and the analyze of impact of rolling pantograph head on current carrying quality, electrical performance and mechanical properties of the pantograph-catenary system is processed.5. Research on active control of catenary. A finite element model of catenary is established, and overall mass & stiffness matrixes are calculated with Ansys software. And independent mass and stiffness matrixes are obtained with a self-made computer program, named by KMExtract. Finally, a dynamical equation of catenary system is established. To facilitate system simulation and controller design, the equation is simplified changed into a state equation by using model reduction method. Then, LQR controller for the system is designed, simulation analyses are conducted on catenary dynamic system before and after active control is implemented.6. The active control and simulation of high speed pantograph-catenary system integrated VR technology with fuzzy control strategy. Based on the dynamical model of semi-active control of pantograph-catenary system based on semi-active control over pantograph, computer simulation models are established with application software, and three-dimensional virtual scene of running train and pantograph subsystem is established with three-dimensional modeling software and motion engine. Finally, three-dimensional virtual scene is combined with the computer simulation model of pantograph-catenary system with socket network communication technology, to bring about a simulation platform of VR-integrated fuzzy active control of pantograph-catenary system, which has a strong sense of immersion and good interactivity, and gives its users a live experience in impact of fuzzy control on vibration performance of pantograph-catenary system as if they had experienced it by themselves. |
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