基于反馈线性化的多变量模糊迭代控制器设计

针对一类多变量非线性控制对象的轨迹跟踪问题,设计一种模糊迭代学习控制器,利用模糊控制器动态调节迭代学习律增益矩阵参数,通过反馈线性化算法和信息融合技术降低模糊控制器输入变量维数,实现多变量非线性系统轨迹跟踪控制.结果表明:与固定增益型迭代学习控制器相比,采用模糊迭代学习控制器学习速度提高,控制稳定性改善,两自由度机械臂的轨迹跟踪控制仿真结果也验证模糊迭代学习控制器的优越性.     

Equivalent linearization of non-linear soil-structure systems

The concept of equivalent linearization, in which the actual nonlinear structure is replaced by an equivalent linear single-degree-of-freedom (SDOF) system, is extended for soil-structure systems in order to consider the simultaneous effects of soil-structure interaction (SSI) and inelastic behavior of the structure on equivalent linear parameters (ELP). This is carried out by searching over a two-dimensional equivalent period–equivalent damping space for the best pair, which can predict the earthquake response of the inelastic soil-structure system with sufficient accuracy. The super-structure is modeled as an elasto-plastic SDOF system whereas the soil beneath the structure is considered as a homogeneous half-space and is replaced by a discrete model. An extensive parametric study is carried out for a wide range of soil-structure systems subjected to a suite of 59 ground motions. The effect of SSI on ELP is studied through introducing a set of non-dimensional key parameters, which define the soil-structure system. It is shown that ELP of soil-structure systems result from a trade-off between SSI effect and nonlinear behavior of the structure. The contribution of each of these two factors depends on the characteristics of the soil-structure system which, in turn, are defined by the introduced non-dimensional key parameters. Moreover, the reliability of the predicted response of soil-structure systems and its sensitivity to deviation from optimal ELP is studied in detail, which sheds light on the consequences of using improper pairs of ELP for interacting systems in the framework of performance-based design of structures. Copyright © 2012 John Wiley & Sons, Ltd.     

不同土层地震反应计算程序对比分析

目前在中、美两国场地土层地震反应分析中,应用比较广泛的计算软件为ESE和SHAKE,两者均采用频域等效线性化方法处理非线性的土层动本构关系。本文采用上述软件分别对三种典型场地进行计算,分析两者差别及造成差别的原因。研究结果表明,SHAKE软件在深软场地时,计算反应谱和加速度峰值均与实际统计结果差别较大,不适合工程应用。ESE软件计算结果比较合理。     

Response prediction,experimental characterization and P‐spectra design of frames with viscoelastic–plastic dampers

Viscoelastic–plastic (VEP) dampers are hybrid passive damping devices that combine the advantages of viscoelastic and hysteretic damping. This paper first formulates a semi‐analytical procedure for predicting the peak response of nonlinear SDOF systems equipped with VEP dampers, which forms the basis for the generation of Performance Spectra that can then be used for direct performance assessment and optimization of VEP damped structures. This procedure is first verified against extensive nonlinear time‐history analyses based on a Kelvin viscoelastic model of the dampers, and then against a more advanced evolutionary model that is calibrated to characterization tests of VEP damper specimens built from commercially available viscoelastic damping devices, and an adjustable friction device. The results show that the proposed procedure is sufficiently accurate for predicting the response of VEP systems without iterative dynamic analysis for preliminary design purposes. A design method based on the Performance Spectra framework is then proposed for systems equipped with passive VEP dampers and is applied to enhance the seismic response of a six‐storey steel moment frame. The numerical simulation results on the damped structure confirm the use of the Performance Spectra as a convenient and accurate platform for the optimization of VEP systems, particularly during the initial design stage. Copyright © 2016 John Wiley & Sons, Ltd.     

On the accuracy of simplified methods for the analysis of isolated bridges

To foster the use of seismic isolation in structures, existing guidelines strive to formulate design methods which are simple and accessible to non‐specialized engineers. On the other hand, not all of the simplifying provisions adopted by the norms can be said to have been adequately tested to provide a consistent level of accuracy. The study attempts, in particular, to elucidate three aspects related to the methods of analysis for linear or linearized isolated bridges on which little or no advice can be found in the norms. The first one is about the way one has to account for the fact that damping matrices of isolated bridges are never of proportional type. The present study demonstrates, through a number of typical applications, that classical modal analysis, using real modes and the diagonal terms of the modal damping matrices, still provide a fully acceptable approximation. The second and third aspects are related to the use of linearization expressions extended to the analysis of hyperstatic bridges. Parametric analyses conducted in the study show that none of the formulas in current use gives satisfactory results for both the displacement and the force responses, a requirement for a reliable design of an isolated bridge. How to use the equivalent linear parameters, and in particular the isolators equivalent damping ratios, in the context of a modal analysis, is treated next. This problem is seldom if ever mentioned in the norms where at most a formula is given for constructing modal damping ratios based on the damping ratios of the isolators. A rational, approximate procedure is discussed in this paper, applicable to all types of structures with non‐proportional damping, which in the case of bridges can be shown to reduce to the expression provided in the Japanese bridge design guidelines. Copyright © 2001 John Wiley & Sons, Ltd.     

随机变量经非线性变换后统计性质的确定

扩展卡尔曼滤波应用于非线性系统的状态估计时，首先要对系统的动力方程进行线性化，这样就给状态的估计带来一定的误差。文中通过对非线性变换的函数进行级数展开，获得了非线性变换后随机变量的真实均值和协方差的表达式，并得到一阶线性化的形式；然后提出了一种精度更高的变换算法，并从理论上证明了该变换算法较之线性化的做法能够更好地逼近非线性变换后的真实均值和协方差，数值试验也证明了这一点。     

滞变—摩擦基底隔震系统的随机地震反应分析

本建立了滞变－摩擦基底隔震系统在地震作用下的运动微分方程，并将地震地面运动模拟成均值为零的两次过滤Ｇａｕｓｓ白噪声过程。使用等效线性化方法求解了这种隔震系统的地震反应统计特征，并分析了这种隔震系统参数的变化对其反应统计特征的影响。     

基于单位四元数描述的单像空间后方交会

在3维空间里,四元数可以非常方便地表示空间方位、空间向量间的旋转、平移和缩放等关系.将四元数理论引入到摄影测量领域,用单位四元数对坐标旋转矩阵进行描述,提出了一种采用单位四元数描述航摄像片位置与姿态的单张像片空间后方交会新方法.该方法与传统方法相比,在平差时避免了频繁的三角函数运算,不仅收敛速度快,而且精度高.     

Earthquake response analysis of the Hualien soil–structure interaction system based on updated soil properties using forced vibration test data

This paper presents results of the earthquake response analysis on a large‐scale seismic test (LSST) structure which was built at Hualien in Taiwan for an international cooperative research project. The analysis is carried out using a computer program which has been developed based on axisymmetric finite element method incorporating dynamic infinite elements for far‐field soil region and a substructured wave input technique. The non‐linear behaviour of the soil medium is taken into account using an iterative equivalent linearization procedure. Two sets of the soil and structural properties, namely the unified and the FVT‐correlated models, are utilized as the initial linear values. The unified model was provided by a group of experts in charge of the geotechnical experiments, and the correlated model was obtained through a system identification procedure using the forced vibration test (FVT) results by the present authors. Three components of ground accelerations are artificially generated through an averaging process of the Fourier amplitude spectra of the ground accelerations measured near the test structure, and they are used as the control input motions for the earthquake analysis. It has been found that the earthquake responses predicted using the generated control motions and with the FVT‐correlated model as the initial linear properties in the equivalent linearization procedure compare very well with the observed responses. Copyright © 2001 John Wiley & Sons, Ltd.     

Stochastic analysis of the linear equivalent response of bridge piers with aseismic devices

The dynamic response of bridge piers with aseismic devices to earthquake excitation is evaluated by the stochastic equivalent linearization technique. The seismic acceleration is schematized through a Gaussian stationary random process. The pier is considered linear elastic, the span is idealized as a rigid mass, the restoring force of the device is represented through a non-linear differential model. The study of the complex modes of the linearized system gives an interpretation of the mechanical behaviour, leads to a formally elementary solution and highlights some phenomena which are typical of the hysteretic systems, particularly of those marked by weak hardening. Even though the solution is limited to the stationary field, it brings out several noteworthy considerations about the effective non stationary behaviour of the structure. Copyright © 1999 John Wiley & Sons, Ltd.