Papers by Author: Xiao Yang Chen

Abstract: Friction force is present in most microelectromechanical systems (MEMS), since they have a large ratio of surface area to their volume. To improve the performance and reliability of MEMS devices, it is necessary to full understand the effect of friction which exists in the majority of MEMS. The model of electrostatic tangential force for MEMS’s moving plates is established based on the rule of energy conservation, further it is revised considering the edge effects by the conformal mapping method for smooth and opening holes plates. Three types of the electrostatic tangential resistance, which are the unrevised theoretical value and revised theoretical value and simulation value, were compared. The effects of microscale and applied voltage and holes are investigated, and the electrostatic tangential resistance between two charged moving plates with respect to each other is analyzed. It is found that the three types of the electrostatic tangential resistance will be increased with the rate of the plate width over the gap of two plates or the applied voltage increasing. And the opening holes did not significantly reduce the value of the electrostatic tangential resistance because of the presence of edge effects. The revised analytic results are larger than the ones not revised, and the former are close to results of ANSYS simulation.

Abstract: Ordinarily, water fire monitor extinguishing systems are applied to protect large space places from fire. To intellectualize them and improve the water usability and extinguishing efficiency, it is necessary to realize the closed-loop control of the landing position of the water jet out from the monitors in order to let the water jet reach the fire point as fast as possible. According to the characteristics of the adjusting mechanism of fire monitors, combing with the new theoretical model for their water jet track, the closed-loop control procedure is simulated. The results show that the water jet can reach the ignition point after only several adjustments. The effective control procedure simulation paves a sound basis for the closed-loop control of the landing position of the water jet out from water fire monitors.

Abstract: Aiming at the problem of analyzing for the dynamic performances of the spindle bearings running at an extreme ultra-high-speed in high-speed electric spindles, a model is built by taking the inertia effects and EHL at the extreme ultra-high-speed into account. Based on the system simulation about a bearing on the movements of every ball, the contact areas states and the lubrication states between balls and both ring raceways, the thermal state inside the bearing and so on, the internal state performances such as the movements and the inertia forces of all the balls, the contact forces and the lubrication films and the temperatures in the contact areas between balls and both ring raceways are analyzed in some different working conditions and configurations. The simulation results showed that the main factors affecting the state performances of a bearing running at an extreme ultra-high-speed are the inertia effects of the balls and the overheating in the contact areas between the balls and both ring raceways, which indicates that it can be improved by adopting the ball material with smaller mass density and the structure with a smaller ball diameter and more ball elements.

Abstract: This work reports on strength behaviour of polysilicon thin film flexure hinge. In order to develop a microscopic modelling of thin film flexure hinge for microstructures, in situ test benches have been designed and fabricated. The experiment demonstrated that a deviation between the macroscopic theory value and experimental result. A model similar to that used for rotational stiffness in macroscopic steel is used to fit testing data for polysilicon film flexure hinge. The dynamic characteristic and fatigue behaviour of the thin film flexure hinge were also investigated. The hinge was excited by an integrated electro-thermal microactuator that could be self-heated and driven. Resonant frequency of the polysilicon flexure hinge test benches is 6.5 Hz, and the maximum operating frequency reached 1KHz. When a cyclic loading of 1μN.μm was exerted to the micromachining flexure hinge, the limit stress alternation number exceed 1.0×108. When the stress alternation number exceeded 1.0×109, the polysilicon beam of microactuator would lost its elastic character. If the micro hinge operated at high temperature (exceed 200/), the lifetime would decreased. If the working temperature were too high, the micro hinge would be burned out.