Against the deficiencies of traditional time domain and frequency domain analysis in detecting wheel-rail （W-R） system hidden risks which wheel flats generate, the time-frequency characteristics of W-R shock caused ...Against the deficiencies of traditional time domain and frequency domain analysis in detecting wheel-rail （W-R） system hidden risks which wheel flats generate, the time-frequency characteristics of W-R shock caused by wheel flat are analyzed and the vehicle-rail dynamic model with wheel flat is investigated. The 10 degrees of freedom （DOF） vehicle model is built up. 90-DOF rail model is constructed. The wheel flat excitation model is built up. The vehicle-track coupling dynamic model including wheel flat excitation is set up through nonlinear Hertzian contact theory. The vertical accelerations of axle box are calculated at different speeds and flat sizes based on the vehicle-track coupling dynamic model with wheel flat. Frequency slice wavelet transform （FSWT） is employed to analyze time- frequency characteristics of axle box accelerations to detect the W-R noncontact risks, which the traditional time domain or frequency domain method does not analyze. The results show that the small flat size and high running speed lead to high frequency W-R impact. Large flat size and high running speed result in momentary loss of W-R contact, and there exist security risks between wheel and rail. The conclusion that the phase of axle box accelerations is same to W-R forces lays a theoretical foundation of monitoring W-R contact safety from axle box acceleration instead of traditional W-R force detection.展开更多
文摘针对舞台上的演员、道具、布景的移动或变换问题,对同类产品的运动形式、全向轮底盘系统、转台支撑系统、车轮减震系统、控制系统等方面进行了研究,对四轮式全向轮式驱动底盘的运动速度和轨迹进行了分析,提出了一种基于全向轮、ARM Cortex-M4内核嵌入式处理芯片以及CAN总线的舞台平面智能移动设备,提出了推力轴承结合万向轮系的转台支撑结构以及线轨结合螺旋弹簧的车轮减震结构,利用Keil u Vision 5作为开发环境编译程序控制驱动电机的转速,利用SolidWorks三维建模功能进行了外形设计,利用SolidWorks的Motion分析功能先后对舞台设备在给定路径下的反向和正向运动进行了仿真分析。研究结果表明,该舞台移动设备能够灵活多变地实现任意给定的平面运动轨迹,并实现较高的空间利用率,运动平稳、可靠性高。
基金supported by the National Natural Science Foundation of China(No.51305358,61134002)
文摘Against the deficiencies of traditional time domain and frequency domain analysis in detecting wheel-rail （W-R） system hidden risks which wheel flats generate, the time-frequency characteristics of W-R shock caused by wheel flat are analyzed and the vehicle-rail dynamic model with wheel flat is investigated. The 10 degrees of freedom （DOF） vehicle model is built up. 90-DOF rail model is constructed. The wheel flat excitation model is built up. The vehicle-track coupling dynamic model including wheel flat excitation is set up through nonlinear Hertzian contact theory. The vertical accelerations of axle box are calculated at different speeds and flat sizes based on the vehicle-track coupling dynamic model with wheel flat. Frequency slice wavelet transform （FSWT） is employed to analyze time- frequency characteristics of axle box accelerations to detect the W-R noncontact risks, which the traditional time domain or frequency domain method does not analyze. The results show that the small flat size and high running speed lead to high frequency W-R impact. Large flat size and high running speed result in momentary loss of W-R contact, and there exist security risks between wheel and rail. The conclusion that the phase of axle box accelerations is same to W-R forces lays a theoretical foundation of monitoring W-R contact safety from axle box acceleration instead of traditional W-R force detection.
