Parameter Optimization Of Subway Discrete Floating Slab Track Isolator Based On Magnetorheological Technology

With the development of the urban rail transit, the vibration induced by theinteraction of rail/wheel system do lots of harm to the surrounding environment,inhabitants and equipments. The floating slab track (FST) can reduce the vibration inhigh and middle frequencies effectively. However, the FST supported by rubbers orsteal springs belongs to passive system and the parameters of the FST system can notbe changed according to the current excitation. Also, because the natural frequency ofFST is close to low frequency excitation, the vibration isolation efficiency for thefrequencies less than20Hz is poor. And the low frequency vibration has significantimpact on human body and sensitive equipments. Therefore, it is important to use newisolator and new method to optimize the damp and stiffness of FST system based onsemi-active vibration isolation for attenuating the low frequency vibration. Both ofmagnetorheological grease (MRG) damper with variable damping andmagnetorheological elastomers (MRE) isolator with variable stiffness are based onmagnetorheological (MR) technology. Due to their rapid response speed, low operatingpower requirement, simple structure and good controllability, MRG damper and MREisolator have become one of the central research subjects in semi-active vibrationisolation fields. The theoretical analysis, numerical simulations and test are applied tostudy the dynamic model of FST system, parameter optimization methodology of FSTisolators, the simulation of FST system, the design of laboratory platform andrealization of FST system. The main content of the dissertation include the following:(1) The significance of FST vibration isolation based on MR technology in lowfrequency is expounded. The history and development of FST and MR technology athome and abroad are reviewed. Some algorithms which may be used to optimizeparameter of isolators are analyzed. Then, the main research works aimed at presentproblems in FST vibration isolation are put forward.(2) On the basis of analysis for excitation and structure of FST, the model of threedegree of freedom for discrete FST via MR technology is proposed. And the workingprinciple of MRG damper and MRE isolator are introduced. In order to provide someexperience for designing parameter optimization, simulations are done on differentexcitation, damping and stiffness.(3) The objective function and constraints of discrete FST vibration isolation are proposed. To attenuate the vertical vibration, Particle swarm optimization (PSO) isadopted for adjusting the damping and stiffness of MR isolators. And in order tobalance the global and local search ability of PSO, inertial parameter is changed by theway of linearly decreasing method and maximum entropy method. In the same time,the method of fuzzy computing is used to resolve the problem that FST may be in thestate of over rolling and pitching when the damping and stiffness both are small. Theprocedure that FST coupled with moving harmonic loads induced by metro train groupis divided into eight phase. The eight phases are classified into two states which areforced vibration and free vibration. The corresponding optimization strategy for thetwo states is presented.(4) A simulation platform of discrete FST based on MR technology has been setup and the previously mentioned parameter optimization algorithm are achieved by Mlanguage. The parameter optimization and vibration isolation of FST system aresimulated under rubber isolator, MR isolator and different excitation frequencies,respectively. Simulation results indicate that the total search time and the number ofiterations of adaptive PSO are less than PSO. The transmitted force based on MRisolator is20%of that based on rubber isolator for the excitation of12Hz frequency.The displacement and acceleration of FST based on MR isolator are also less than thatof FST based on rubber isolator. The insertion loss of the rolling and pitching angulardisplacement reaches to3.75after using MR isolator to instead of rubber isolator in thefrequency of25Hz, meanwhile, the parameters of MR isolator are optimized by themethod of fuzzy computing.(5) For the sake of parameter optimization and vibration isolation control on testbench in the future, a test bench of discrete FST system is built whose vibration signalsare collected by the hardware platform of NI PXI and software system based onLabVIEW. The bench test results show that transmitted force and acceleration of FSTsystem based on MRG damper are decreased compared with FST system based onrubbers.