一类永磁同步电动机的TSM控制器设计

基于永磁同步电动机精确的数学模型,针对永磁同步电动机绕组相电流和转速强耦合特性,依据中继切换控制机制和有限时间收敛的终端滑动模态控制机制,考虑了永磁同步电动机的有限时间跟踪问题。给出了其终端滑模控制器的设计方案。在所设计的控制作用下,闭环系统将在有限时间内达到平衡状态。并且保证了闭环系统所有信号的有界性和平衡点的全局稳定性,以及系统在有限时间内精确地跟踪给定的参考信号。最后对一具体的永磁同步电动机模型进行了数值仿真,仿真结果表明在所设计的终端滑模控制器作用下,系统的跟踪误差在有限时间内达到零,验证了所提算法的正确有效性。     

基于视窗分析模型的我国高校科研效率评价

本文分别取窗宽为1-5,应用视窗分析模型对我国各省市高校在2003-2007年的科研效率进行动态分析。通过比较不同窗宽的分析结果,发现随着窗宽的增加,我国各省市高校的TE和PE呈递减变化,SE呈无规律变化;科研效率在不同年份对窗宽的敏感程度不同;选择不同的窗宽会使得研究者对科研效率的长期变化趋势得出大相径庭的结论。对于"如何确定理想的窗宽",从理论上提出新的分析方法,研究确定理想的窗宽,建立适合于我国高校科研效率动态分析的更合理的视窗分析模型。与传统DEA模型的分析结果进行对比,发现两者之间存在很大的偏差。这进一步说明了建立理想窗宽的视窗分析模型,对我国高校科研效率进行动态分析是很有必要的,此视窗模型的分析结果更符合科研工作的实际情况。     

Consistency of performances in the Tkatchev release and re-grasp on high bar

The Tkatchev on the high bar is a release and re-grasp skill in which the gymnast rotates in a direction during flight opposite to that of the preceding swing. Since the release window is defined as the time during which the gymnast has appropriate linear and angular momentum to ensure the bar can be re-grasped, it was speculated that the release windows for this skill would be smaller than for dismounts that are less constrained. One senior male gymnast competing at national standard performed 60 Tkatchev trials. A four-segment planar simulation model of the gymnast and high bar was used to determine the release windows in 10 successful and 10 unsuccessful performances of the Tkatchev recorded using a Vicon motion analysis system. Model parameters were optimized to obtain a close match between simulations and recorded performances in terms of rotation angle (1°), bar displacements (0.01 m), and release velocities (1%). Each matched simulation was used to determine the time window around the actual point of release for which the model had appropriate release parameters to complete the Tkatchev successfully. The release windows for the successful trials were small compared with those of dismounts. The unsuccessful trials were associated with later release and later timing of the actions at the shoulders and hips.     

The effects of surface traction characteristics on frictional demand and kinematics in tennis

The interaction between footwear and surfaces influences the forces experienced by tennis players. The purpose of this study was to investigate traction demand and kinematic adaptation during tennis-specific movements with changes in traction characteristics of surfaces. We hypothesised that players would increase the utilised coefficient of friction (horizontal to vertical ground reaction force ratio) when the shoe surface combination had a high coefficient of friction and flex their knee after contact to facilitate braking. Eight participants performed two separate movements, side jump out of stance and running forehand. Ground reaction force was measured and three-dimensional kinematic data were recorded. Clay surface and cushioned acrylic hard court (low vs. high shoe–surface friction) were used. The peak utilised coefficient of friction was greater on clay than the hard court. The knee was less flexed at impact on clay ( ? 5.6 ± 10.2°) and at peak flexion ( ? 13.1 ± 12.0°) during the running forehand. Our results indicate that tennis players adapt the level of utilised friction according to the characteristics of the surface, and this adaptation favours sliding on the low friction surface. Less knee flexion facilitates sliding on clay, whereas greater knee flexion contributes to braking on the hard court.     

探析高校图书馆管理中的另类法则

将企业管理中的南风法则、共生效应、破窗理论运用到高校图书馆管理工作实践中,有助于图书馆管理者辨识和诊断图书馆管理中存在的问题。南风法则的以柔制胜、共生效应中的协同合作、破窗理论对于细节的重视均给高校图书馆管理工作以启示:图书馆需要温情管理,图书馆应谋求共生共存、和谐发展,图书馆要注重提高组织防微杜渐的意识和能力。     

Adaptive backstepping sliding mode control for nonlinear systems with input saturation

An adaptive backstepping sliding mode control is proposed for a class of uncertain nonlinear systems with input saturation.A command filtered approach is used to prevent input saturation from destroying the adaptive capabilities of neural networks (NNs).The control law and adaptive updating laws of NNs are derived in the sense of Lyapunov function,so the stability can be guaranteed even under the input saturation.The proposed control law is robust against the disturbance,and it can also eliminate the impact of input saturation.Simulation results indicate that the proposed controller has a good performance.     

基于均匀核的柯西密度估计

非参数核密度估计具有良好的性质,有固定窗宽和变窗宽两种形式,由于渐近方差收敛率相同,而渐近偏度存在差异,固定窗宽和球估计量的偏度为h2,Ambramson估计量为h4,本文提出了固定窗宽核密度估计量的一个性质,并计算基于均匀核的柯西密度Ambramson估计量的期望发现刚好是无偏的。     

基于RBF神经网络和积分型高阶滑模控制的永磁同步电机位置伺服系统

本文主要研究永磁同步电机伺服系统的位置跟踪问题。根据矢量控制原理,针对d轴电压,设计了一阶滑模控制器,将使d轴电流在有限时间到达0。针对q轴电压,基于滑模控制理论,设计了积分型高阶滑模控制器。由于系统中存在不确定性参数,设计了基于神经网络的q轴电压滑模控制器。理论分析表明,在所设计的控制器作用下,可以保证位置系统的精确跟踪控制。仿真结果表明了该控制方案具有较好的收敛性和抗干扰性能。     

基于MSP430的智能语音广告窗控制系统设计

基于TI公司MSP430系列16位低功耗单片机设计了智能语音广告窗控制系统,主要介绍了系统硬件设计原理和软件流程。该系统工作稳定、信价比高、可扩展性强,将会有很好的市场价值。     

基于B/S模式的电费信息管理系统的设计与实现

本文分析了电费管理系统开发策略,提出用Powerbuilder开发基于B/S模式的管理系统,并设计了此系统的功能模块及所使用的关键技术.