|Title:||Vibration attenuation for high-speed trains using magnetorheological (MR) dampers|
|Subject:||Hong Kong Polytechnic University -- Dissertations|
High speed trains -- Vibration
Railroad trains -- Vibration
Vibration -- Control
|Pages:||xvii, 194 pages : color illustrations|
|Abstract:||The past two decades witness the rapid expansion of high-speed rail. However, as the rail service experiences a step-change increase inoperating speeds, the vehicle vibration response, especially in the lateral direction, become more important. The subject of vibration mitigation for high-speed train has been under studied for many years. Modern control theory and advanced actuator technology enables the train suspension to consider a wide variety of innovative possibilities. More recently, magnetorheological (MR) damper emerges as a promising semi-active actuator for vibration control for high-speed trains. This research focuses on advanced secondary suspension for high-speed train using MR dampers in the interest of lateral ride comfort improvement. Firstly, an experimental study on incorporating MR damper in a secondary suspension is conducted. The rail vehicle in tests is full-scale carriage of high-speed train CRH3 electric multiple unit (EMU). Three types of MR dampers with different control force range are designed, fabricated, and incorporated into the EMU secondary suspension, to account for the lateral vibration mitigation. The integrated vehicle is tested at speeds in a wide range, with random track irregularities. The performance of the MR suspension is tuned by a driven current switching between passive-off and passive-on states. The dynamic behaviour of the integrated vehicle system and the ride comfort at each state is evaluated, and thus the potential of the MR suspension is demonstrated. Secondly, according to the previous rolling-vibration experiment results, a new type of MR damper with more suitable control force range is selected to replace the lateral damper of high-speed train secondary suspension. The dampers are equipped with strain gauge for force sensing and LVDT for displacement motion sensing. The modelling of the new dampers is conducted. A viscoelastic-plastic (VEP) based model which is only current dependent is employed to represent the dynamic characteristics of the MR dampers. However, the dynamics of the MR dampers obtained through a MTS test system shows that the damper response is related not only to the applied current (or magnetic strength), but to the frequency and displacement amplitude, or rather the velocity amplitude. Therefore, an enhanced model that consists of ten parameters is ultimately formulated to characterize the inherent nonlinear hysteresis of the MR dampers. In addition, since the governing equations explicitly contain the applied current to the damper, the inverse model which expresses the relationship between the command current and the desired damper force can be devolved directly from the forward model. Thirdly, the effectiveness of negative stiffness superimposed with simple damping models for vehicle vibration mitigation is interpreted by examining the negative stiffness component incurred in the skyhook damping. The negative stiffness tends to increase the damper motion, thereby facilitating the energy dissipation. Therefore, it is straightforward to impose a negative stiffness component into a vehicle system in an effort to mitigate the unwanted vibration of the car body. A negative stiffness with viscous damping and friction damping is emulated by the MR damper respectively. It is should be noted that, the MR damper is a semi-active device that cannot produce fully active control forces. The lower force bound of the MR damper is identified, and then compiled to the damper controller to emulate the unclipped negative stiffness and the clipped negative stiffness, respectively. Then, a fifteen degree-of-freedom model for the high-speed train EMU is established in MATLAB SIMULINK. The model consists of four wheelsets and two trucks which are characterized by lateral and yaw motions respectively, and a car body represented by lateral, yaw and roll motions. The model is used to reproduce the lateral vibration response of the car body of the vehicle subjected to the random track irregularities. Three suspensions, i.e., passive suspension with existing hydraulic dampers, MR suspension with emulated negative stiffness with viscous damping (NSV, or semi-active skyhook damping) and MR suspension with emulated negative stiffness with friction damping (NSF), are integrated with the vehicle model, and evaluated for the vibration mitigation performance. The simulation result shows that, the suspensions with negative stiffness component show significant capability inincreasing damper motions.|
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