FEEDBACK CONTROL OPTIMIZATION FOR SEISMICALLY EXCITED BUILDINGS

A feedback control optimization method of partially observable linear structures via stationary response is proposed and analyzed with linear building structures equipped with control devices and sensors. First, the partially observable control problem of the structure under horizontal ground acceleration excitation is converted into a completely observable control problem. Then the It6 stochastic differential equations of the system are derived based on the stochastic averaging method for quasi-integrable Hamiltonian systems and the stationary solution to the Fokker-Plank-Kolmogorov （FPK） equation associated with the It6 equations is obtained. The performance index in terms of the mean system energy and mean square control force is established and the optimal control force is obtained by minimizing the performance index. Finally, the numerical results for a three-story building structure model under E1 Centro, Hachinohe, Northridge and Kobe earthquake excitations are given to illustrate the application and the effectiveness of the proposed method.     

结构形状优化设计数值方法的研究和应用

本文论述了连续体结构形状优化设计数值方法的研究和应用进展,讨论了结构模型化、灵敏度分析、优化方法改进、优化实用软件开发以及同CAD技术相结合等问题,介绍了在结构优化设计软件MCADS中采用的方法,并通过工程实例说明了结构形状优化设计的应用及其价值。     

An efficient method for structural optimization

Based on the dual theory of nonlinear mathematical programming and the second order Taylor series expansions of functions, an efficient algorithm for structural optimum design has been developed. The main advantages of this method are the generality in use, the efficiency in computation and the capability in identifying automatically the set of active constraints. On the basis of the virtual work principle, formulas in terms of element stresses for the first and second order derivatives of nodal displacement and stress with respect to design variables are derived. By applying the Saint-Venant's principle, the computational efforts involved in the Hessian matrix associated with the iterative expression can be significantly reduced. This method is especially suitable for optimum design of large scale structures. Several typical examples have been optimized to test its uasefulness.     

计及气动和隐身约束结构综合优化的并行子空间优化方法

通过分析基于响应面的并行子空间优化算法的特点指出并行子空间优化算法学科级优化的作用在于向系统级优化响应面提供性能优良的设计点.在此基础上,建立了不要求学科级优化的改进的并行子空间优化算法,进一步降低了设计优化的计算量,解决了分析模块与优化模块间的接口困难.依据该算法建立了结构、气动和隐身一体化设计优化框架,实现了某无人机机翼计及气动和隐身约束的结构综合优化.     

The automatic control of boundary-layer transition — Experiments and computation

In recent years there has been an increasing interest in the control of boundary-layer transition through the use of wall suction. In the current work suction is provided through one or more suction panels situated close to the leading edge of a plate. Experiments show that boundary-layer pressure fluctuation measurements can be used to identify the position of transition. Transition can be maintained at a desired location with minimum power consumption by employing an automatic adaptive feedback control loop which regulates the suction flow rates of two independent suction panels. This can be expressed as a constrained optimization problem. To allow the suction flow rates to be updated, a modified least mean squares algorithm is used within the control loop. Experimental measurements show that the control algorithm allows fast and stable convergence towards the optimum suction distribution for a double suction panel configuration. Numerical simulations have also been performed. The two-dimensional boundary layer was calculated allowing the viscous boundary layer to interact with the inviscid outer flow. Following linear stability theory the spatial growth rates are calculated by solving an Orr-Sommerfeld type eigenvalue problem, with the streamwise location of transition predicted via thee ^N -method. Applying the same optimization strategy as in the experiments, good qualitative agreement between computations and experiments was found. The optimization algorithm has been applied to computer models where the relation between suction flow rates and transition location is described by an empirical analytical function. This shows that the controller can in principle be applied to systems with more than two suction panels.Nomenclature b transition location with zero suction - d desired transition location - e(k) error signal - k iteration index - p rms pressure - p _ref reference rms pressure - r sum of the reference pressure - u streamwise velocity - u _e external velocity - inviscid external velocity - A wave amplitude - F( ) cost function - I identity matrix - N maximum amplification factor - P projection matrix - R Reynolds number - Re Reynolds number based on the boundary-layer thickness - R matrix of weights - Tu turbulence level - vector of suction flow rates - v normal velocity - v _wall suction velocity at the surface - x streamwise coordinates - x _m microphone location - x _T(k) measured transition location - y normal coordinate - y(k) sum of the measured pressures - w(k) noise - plate length - r +i _i - free stream velocity - * displacement thickness - gradient vector - Lagrange multiplier - controller gain - disturbance stream function - disturbance amplitude - wave frequency = complex wave number     

考虑设计规范的海洋平台结构选型优化

针对具体海洋环境条件和生产要求，对导管架平台结构进行选型优化——拓扑布局与构件尺寸的联合优化，充分考虑设计规范的要求，建立多设计准则、多约束条件和多荷载工况的设计模型，其中环境荷载包括：风、浪、流、海冰从不同方向对平台的作用。通过结构选型优化获得最佳的结构拓扑布局形式，在降低平台造价的同时，设计出满足结构的稳定特性、安全寿命等多种设计准则的新型平台结构。     

包含两类变量的离散变量桁架结构拓扑优化设计

建立了包含截面和拓扑两类变量的离散变量结构拓扑优化设计的数学模型,该模型考虑了截面变量与拓扑变量间的耦合关系,反映了拓扑优化问题的组合优化本质,可以较好地解决"极限应力"、"最优解的奇异性"等困扰结构拓外优化设计的问题．同时采用相对差商法进行离散变量桁架结构拓扑优化,直接求解包含两类变量的离散变量结构拓扑优化设计数学模型,收到了比较满意的效果．     

用二级控制法对二维连续体进行形状优化

二级控制的意思是在自然设计变量和有限元网格节点之间加入设计单元，建立自然设计变量控制关键点坐标，关键点控制有限元网格节点，共两层控制关系。后一层控制关系借助有限元形函数描述设计单元，并引入相应的参数坐标，从而实现敏庋分析、结构形状变化的控制和网格的变动控制。本文使用二级控制理论有效地解决了二维连续体结构形状优化的一些困难，将形状优化问题处理成序列二次规划问题求解。使用MSC／PCL语言在MSC／Patran＆Nasntran平台上实现了优化模块的二次开发。本文设计思路的可行性和程序的有效性通过若干算例得到证实。     

船舶碰撞的研究方法和进展

本文简要评述船舶碰撞的研究进展和发展趋势．介绍了船舶碰撞研究的内容和方法（包括理论的和实验的）．本文重点阐述实船试验方法，包括实尺试验的基本步骤，实尺试验的输入参数选择和试验地点选择．最后提出了综合性意见，并介绍了国内在碰撞研究方面已做的工作和将要做的工作．     

螺旋槽干气密封微尺度流动场的近似计算及其参数优化

应用PH线性化方法、迭代法,近似求解了螺旋槽内稳态微尺度流动场的非线性雷诺方程,求得了气体动压和速度分布的解析解。继而利用多目标优化方法构建了气膜刚度与泄漏量之比的协调函数,并对该目标函数进行了近似求解,获得了最佳的螺旋槽几何参数值。