柔性单桩变形机理分析及沉降和承载力计算

在讨论桩的受力和变形机理的基础上 ,利用土力学理论和位移协调条件推导出了柔性单桩承载力和沉降计算公式。并通过一个工程实例 ,对所提出的计算公式进行了验证     

Computational Schemes for Flexible,Nonlinear Multi-Body Systems

This paper deals with the development of computational schemes for the dynamic analysis of flexible, nonlinear multi-body systems. The focus of the investigation is on the derivation of unconditionally stable time integration schemes for these types of problem. At first, schemes based on Galerkin and time discontinuous Galerkin approximations applied to the equations of motion written in the symmetric hyperbolic form are proposed. Though useful, these schemes require casting the equations of motion in the symmetric hyperbolic form, which is not always possible for multi-body applications. Next, unconditionally stable schemes are proposed that do not rely on the symmetric hyperbolic form. Both energy preserving and energy decaying schemes are derived that both provide unconditionally stable schemes for nonlinear multi-body systems. The formulation of beam and flexible joint elements, as well as of the kinematic constraints associated with universal and revolute joints. An automated time step selection procedure is also developed based on an energy related error measure that provides both local and global error levels. Several examples of simulation of realistic multi-body systems are presented which illustrate the efficiency and accuracy of the proposed schemes, and demonstrate the need for unconditional stability and high frequency numerical dissipation.     

SGCMGs驱动的挠性航天器有限时间自适应鲁棒控制

针对挠性航天器系统中同时存在单框架控制力矩陀螺群(Single gimbaled control moment gyroscopes, SGCMGs) 摩擦非线性、电磁干扰力矩、惯量摄动以及外部干扰等问题, 提出了一种有限时间自适应鲁棒控制(Finite-time adaptive robust control, FTARC) 方法. 针对系统中存在未知参数的情况, 分别设计自适应更新律, 使得控制器的设计不依赖参数信息, 同时减小外部干扰对系统的不利影响. 应用Lyapunov稳定性理论证明了闭环系统姿态角误差和姿态角速度误差可在有限时间内收敛到原点附近的邻域内. 仿真结果表明, 所提控制律可实现挠性航天器姿态快速机动, 并获得甚高指向精度.     

大采高采煤机挡矸装置的改进设计

分析了传统的大采高采煤机挡矸装置的结构原理、技术特点及存在的问题,提出了改进设计并进行了仿真分析。通过增加油缸数量、加强加厚顶护板、将刚性连接改为柔性连接、增设分流集流阀等手段,实现了对挡板的动态调节和支护,有效地提高了挡矸装置的可靠性和采煤机的开采效率。仿真结果表明,改进后的挡矸装置受力更均匀,挡板能承受的力更大。     

基于非线性PID的柔性两轮机器人运动控制

柔性两轮机器人是一种不稳定、非线性、强耦合系统。该系统的突出特点是在机器人的腰部装有柔性的机体结构,能够更好地模拟人和动物的生物动力学特性,具有更好的仿生性质,同时,系统的控制难度显著增大,为使机器人能够平衡直立运动,且具有较强的鲁棒性,提出了非线性PD的姿态平衡控制方法,实现了机器人的姿态平衡,并同时设计了PID航向差动控制结构驱动左右轮电机,使机器人能够完成直线行进、自旋、环绕等多种运动平衡模式。实验结果表明,机器人具有优良的平衡能力和机动性能,从而验证了方法的有效性。     

Highly reliable a‐IGZO TFTs on a plastic substrate for flexible AMOLED displays

We have successfully reduced threshold voltage shifts of amorphous In–Ga–Zn–O thin‐film transistors (a‐IGZO TFTs) on transparent polyimide films against bias‐temperature stress below 100 mV, which is equivalent to those on glass substrates. This high reliability was achieved by dense IGZO thin films and annealing temperature below 300 °C. We have reduced bulk defects of IGZO thin films and interface defects between gate insulator and IGZO thin film by optimizing deposition conditions of IGZO thin films and annealing conditions. Furthermore, a 3.0‐in. flexible active‐matrix organic light‐emitting diode was demonstrated with the highly reliable a‐IGZO TFT backplane on polyimide film. The polyimide film coating process is compatible with mass‐production lines. We believe that flexible organic light‐emitting diode displays can be mass produced using a‐IGZO TFT backplane on polyimide films.     

Semi‐Global Output Feedback Stabilization for a Class of Uncertain Nonlinear Systems

This paper addresses the problem of semi‐global stabilization by output feedback for a class of nonlinear systems whose output gains are unknown. For each subsystem, we first design a state compensator and use the compensator states to construct a control law to stabilize the nominal linear system without the perturbing nonlinearities. Then, combining the output feedback domination approach with block‐backstepping scheme, a series of homogeneous output feedback controllers are constructed recursively for each subsystem and the closed‐loop system is rendered semi‐globally asymptotically stable.     

Feedback predictive control for constrained fuzzy systems with Markovian jumps

In this paper, a feedback model predictive control method is presented to tackle control problems with constrained multivariables for uncertain discrete‐time nonlinear Markovian jump systems. An uncertain Markovian jump fuzzy system (MJFS) is obtained by employing the Takagi‐Sugeno (T‐S) fuzzy model to represent a discrete‐time nonlinear system with norm bounded uncertainties and Markovain jump parameters. To achieve more generality, the transition probabilities of the Markov chain are assumed to be partly unknown and partly accessible. The predictive formulation adopts an on‐line optimization paradigm that utilizes the closed‐loop state feedback controller and is solved using the standard semi‐definite programming (SDP). To reduce the on‐line computational burden, a mode independent control move is calculated at every sampling time based on a stochastic fuzzy Lyapunov function (FLF) and a parallel distributed compensation (PDC) scheme. The robust mean square stability, performance minimization and constraint satisfaction properties are guaranteed under the control move for all admissible uncertainties. A numerical example is given to show the efficiency of the developed approach. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

小口径离轴抛物面反射镜挠性支撑设计分析

关于反射镜支撑稳定性优化设计问题,离轴抛物面反射镜作为空间光学遥感器的重要光学元件,面形精度直接影响遥感器性能。针对反射镜所处环境,组件一阶频率要求高,设计了一种反射镜背部中心单点挠性支撑结构,并利用拓扑优化技术对反射镜进行了轻量化设计。为了结构设计的合理性,采用有限元技术对反射镜组件进行了模态分析、结构强度分析、谐响应分析及热环境分析。分析结果表明:反射镜在重力作用下最大面形误差RMS=1.16nm;在±10℃温度载荷作用下最大面形误差RMS=11.46nm;反射镜组件一阶频率为574.19Hz。使挠性支撑结构具有良好的静、动态特性和热尺寸稳定性,满足反射镜面形要求。     

不锈钢薄板等离子电弧加热柔性成形试验研究

介绍了等离子电弧加热金属薄板柔性成形的特点,分析了等离子电弧柔性成形的机理.通过实验,得出了扫描次数、电弧电流、扫描速度、电弧高度、薄板厚度等参数对弯曲变形的影响规律.该规律对于提高弯曲效率、改善表面质量具有一定的指导意义.