考虑关节摩擦的空间机器人动力学建模与参数辨识

研究了考虑关节摩擦影响的空间机器人系统的动力学建模与参数辨识问题．采用单向递推组集方法和虚功率原理建立了含有关节摩擦的多体系统动力学方程,推导了关节摩擦对系统动力学方程的贡献,采用基于腕力传感器信号和最小二乘法的辨识方法进行了系统惯性参数的辨识．数值仿真结果验证了数学模型的正确性与辨识方法的有效性．     

基于滑模理论的建筑结构分散稳定控制

基于大系统分散控制思想,将大尺度高阶建筑结构系统分解为多个子结构系统;子结构之间的相互耦合作用视为有界广义力,得到以状态方程形式的子结构模型。利用滑模理论的抗摄动条件,设计具有全局稳定的子结构滑动模态轨迹,利用子结构系统局部状态实现全局稳定的控制力条件,并以参数ρi实现各子结构间的调节,建立稳定的分散控制格式。在控制算法中采用了准滑模控制方法,克服变结构滑动模态中的抖振影响。利用本文方法,对20层钢结构基准模型在地震激励下的控制进行设计并数值仿真,验证了该方法的有效性。     

多种群遗传算法在PBX本构模型参数识别中的应用

利用多种群并行结构对标准遗传算法SGA进行并行化处理,引入移民算子和精华种群形成多种群遗传算法MPGA,并设计了自适应交叉和变异概率对算法的收敛速度进行改进。结合ABAQUS软件和改进的多种群遗传算法,建立了材料本构模型参数识别方法。采用该方法对PBX炸药黏弹性损伤本构模型参数进行了模拟识别,并同基于标准遗传算法的参数识别方法进行了比较。结果证明,基于改进多种群遗传算法IMPGA的方法对克服算法未成熟收敛有显著的效果,识别结果更稳定。同时该方法的收敛速度更快,寻优能力更强,适合复杂非线性问题的优化,此方法可以被应用到其他材料本构模型的参数识别中。     

Investigation of the numerical accuracy of shallow water flow estimation based on the ensemble Kalman filter using the SUPG FEM

ABSTRACT

The shallow water equation is employed as the governing equation to simulate flow behaviour in shallow water flow regions. The SUPG and the backward Euler methods, respectively, were employed for discretisation in space and time. In this paper, we carry out investigations on the numerical accuracy of shallow water flow estimation based on the ensemble Kalman filter using the SUPG FEM, and show the results of numerical experiments. The open channel model was employed as the numerical example in this study. The extended Kalman filter is generally employed to solve parameter identification problems. However, linearisation of the governing equation is carried out to apply parameter identification: it is known to be difficult to carry out computation reliably if problems that include a high degree of non-linearity need to be solved. On the other hand, linearisation of the governing equation is not carried out in the ensemble Kalman filter, so there is potential for the unknown parameter to be simultaneously identified in the computation of the data assimilation. The distribution of the unknown kinematic viscosity coefficient was therefore also investigated.     

Dynamic simulation of liquid-filled flexible multibody systems via absolute nodal coordinate formulation and SPH method

A new computation method is proposed to study the coupled dynamics of a partially liquid-filled flexible multibody system, where the liquid is modeled by using the Smoothed Particle Hydrodynamics (SPH) method and the flexible bodies are described by using the Absolute Nodal Coordinate Formulation (ANCF). Extra virtual particles are introduced and embedded in the liquid neighboring the rigid or flexible boundaries in order to prevent field particles from penetrating the boundary and force them to follow the deformation of flexible boundary. The interaction forces between the liquid and the flexible multibody system are transmitted by the virtual particles. The domain decomposition is used to improve the efficiency of interaction detection in SPH computation. A predictor-corrector scheme is used to solve the governing equations of liquid discretized by SPH particles. The generalized-alpha method based on sparse matrix storage skill is used to solve a huge set of dynamic equations of the multibody system. The OpenMP+OpenACC based parallel computation skills are embedded in the iteration processes to speed up the computation efficiency. Finally, three numerical examples are given to validate the proposed computation method.     

基于分离式建模的砖石古塔动力性能与响应分析

为研究砖石古塔的动力特性及地震响应机制,以渭南慧照寺塔为对象,采用块体-灰浆分区离散方法,分别建立刚性地基条件与考虑地基-结构相互作用条件下古塔的数值模型,计算比较了塔体的动力特性;并分别按9度小震、中震和大震输入El-Centro波、Taft波和兰州人工波,计算了结构的位移和加速度反应,与相互作用系统进行比较。结果表明,考虑土-结构相互作用后,古塔结构的一阶自振频率降低5.7%,二阶频率降低45%;El-Centro波和Taft波作用下,位移和加速度响应显著增大,大震作用时,与不考虑土-结构相互作用对比,主拉应力峰值显著增加,古塔从灰浆开裂发展为砖与灰浆同时开裂;兰州人工波作用下,考虑土-结构相互作用后,主拉应力和结构开裂变形反而降低。研究结果可为古塔抗震计算与性能评估提供参考。     

具有可变均压槽的气体静压推力轴承性能研究

具有可变均压槽的气体静压推力轴承,是作者提出的一种新结构轴承.本文建立了这种新结构轴承的性能计算方法,用有限差分法耦合求解气体静压推力轴承的雷诺方程和弹性薄片的变形控制方程,得到轴承的各项性能参数,并通过试验加以对比验证,计算结果与试验具有较好的一致性.结果表明该新型气体静压推力轴承的设计方案能够提高轴承的刚度.     

精细积分时域平均法和随机扩阶系统法

讨论含随机参数结构的动力响应的计算问题,发展了精细积分时域平均法（ＴＡＰＩＭ）,它可以用来计算确定性系统受到随机激励时的动力响应;结合随机扩阶系统方法与随机有限元法,将ＴＡＰＩＭ方法应用于计算随机参数结构的动力响应,取得了较好的结果。结出了数值算例,结果表明随机扩阶系统法,随机有限元法与精细积分时域平均法的结合是计算 随机参数结构动力响应的有效方法。     

基于子结构的非线性参数系统动力反演方法研究

研究了输入、输出不完备情况下的非线性参数系统动力反演问题.将子结构技术与分解算法相结合,引入广义逆,无需迭代.直接求得待识别参数的极小范数最小二乘解,反演获得未知输入荷载.本文从理论上论证了该方法的收敛性和严格的适用条件,为有限测点条件下非线性参数系统的动力反演问题提供了一个较好的解决方法.与全量补偿算法相比,计算效率大大提高,具有广泛的工程实际应用前景.数值算例表明该方法具有很好的参数识别精度及荷载反演效果.     

一种土的非线性弹性本构模型参数的反演方法

旨在提出一种土的非线性弹性本构模型参数反演的方法。以现今普遍实行的地基载荷试验为基础,依据遗传算法的组合优化理论,采用正演计算和遗传算法优化相结合的方式,建立了土层非线性弹性本构模型参数反演的方法;并依据某黄土场地地基载荷试验数据,实施了黄土土层非线性弹性本构模型参数反演的全过程。计算结果表明,所建立的方法可以实现土层非线性弹性本构模型中相互关联的多个参数的组合优化,并在对初始值要求较低的情况下,可以获得良好的参数反演精度。从而为土的变形特性分析和土与其中及相邻结构的共同作用分析,提供了较好的土体本构模型参数的确定方法。     

An improved time integration scheme based on uniform cubic B-splines and its application in structural dynamics

A time integration algorithm for structural dynamic analysis is proposed by uniform cubic B-spline functions. The proposed algorithm is successfully used to solve the dynamic response of a single degree of freedom(SDOF) system, and then is generalized for a multiple-degree of freedom(MDOF) system. Stability analysis shows that, with an adjustable algorithmic parameter, the proposed method can achieve both conditional and unconditional stabilities. Validity of the method is shown with four numerical simulations.Comparison between the proposed method and other methods shows that the proposed method possesses high computation accuracy and desirable computation efficiency.     

Controlling Hopf�CHopf interaction bifurcations of?a?two-degree-of-freedom self-excited system with?dry?friction

The feedback control problem of designing Hopf?CHopf interaction bifurcations into a dry friction system at a pre-specified parameter point is addressed. A new bifurcation criterion without using eigenvalues is established to preferably determine the control gains. Numerical simulation shows that the torus solution of Hopf?CHopf interaction bifurcation can be created in the friction system at a desired parameter location.     

Powell’s optimal identification of material constants of thin-walled box girders based on Fibonacci series search method

A dynamic Bayesian error function of material constants of the structure is developed for thin-walled curve box girders. Combined with the automatic search scheme with an optimal step length for the one-dimensional Fibonacci series, Powell’s optimization theory is used to perform the stochastic identification of material constants  of the thin-walled curve box. Then, the steps in the parameter identification are presented. Powell’s identification procedure for material constants of the thin-walled curve box is compiled, in which the mechanical analysis of the thin-walled curve box is completed based on the finite curve strip element (FCSE) method. Some classical examples show that Powell’s identification is numerically stable and convergent, indicating that the present method and the compiled procedure are correct and reliable. During the parameter iterative processes, Powell’s theory is irrelevant with the calculation of the FCSE partial differentiation, which proves the high computation efficiency of the studied methods. The stochastic performances of the system parameters and responses are simultaneously considered in the dynamic Bayesian error function. The one-dimensional optimization problem of the optimal step length is solved by adopting the Fibonacci series search method without the need of determining the region, in which the optimized step length lies.     

混合驱动水下滑翔机水动力参数辨识

与传统水下滑翔机相比,混合驱动水下滑翔机可以分别利用头部的浮力驱动单元和机身尾部的螺旋桨推进单元进行驱动从而实现不同形式的运动,具备低功耗、长航程、良好机动性等特点,具有广泛的应用前景. 准确的动力学模型以及精确的水动力参数是实现混合驱动水下滑翔机控制系统设计以及精确导航的基础. 在混合驱动水下滑翔机动力学模型已知的前提下获得准确的水动力参数是本文主要研究的问题. 本文以天津大学研制的混合驱动水下滑翔机“海燕” 作为研究对象,提出一种在有限航行参数条件下,基于大数据统计分析的计算流体力学(computational fluid dynamics, CFD) 和参数辨识相结合来获取混合驱动水下滑翔机的水动力参数的方法. 即首先建立滑翔机的动力学模型,推导出稳态数据与所求水动力参数的关系;然后采用CFD 的方法得到其升力系数,根据大量稳态纯滑翔实验数据,结合大数据统计分析,辨识出其剩余水动力参数;最后,根据混合驱动模式下的实验数据辨识出与螺旋桨相关的参数,从而得到其整套的水动力参数. 该方法不仅结合了CFD 方法具有获取复杂外形结构航行水动力的特点,而且可以有效利用大量现场实验数据,因而能够更加准确地辨识其实际运动. 通过运动仿真与试验对比,验证了该辨识方法的正确性和有效性,对滑翔机的研究具有指导意义.      

基于POD-RBF代理模型的迭代更新反演方法

针对常规的水工大坝等大型工程结构参数反演需要耗费大量有限元正分析机时的问题,建立了具有较好反演精度和泛化性能的POD-RBF代理模型和快速迭代更新反演算法。基于有限元分析获得足量数据样本,利用POD提取本征向量,并使用RBF方法进行插值得到有限元模型的代理模型;同时结合粒子群算法的全局寻优能力和高斯-牛顿法的快速局部收敛优势,建立了一种新的高效率迭代反演方法,并应用于混凝土大坝分区弹性模量反演。结果表明,该方法适用于大坝等大体积混凝土结构的力学参数反演。同时,相较于传统的单一反演方法,该方法在反演效率和反演精度两方面均显示出优势。     

基于磁流变阻尼器的多单体组合隔震结构模糊控制研究

提出了一种新的组合结构振动控制体系——多单体组合隔震结构,建立了力学模型及运动方程。基于瞬时最优控制算法,将控制力表达成阻尼力的形式,用磁流变阻尼器充当控制器,运用模糊控制方法对其进行控制。通过计算机仿真分析,并运用LQR控制与之进行对比。研究结果表明,这种组合隔震结构体系的控制效果明显,各结构的地震响应都有明显降低。采用模糊控制不需要建立精确的计算模型,并能达到与LQR控制相接近的控制效果。用磁流变阻尼器充当控制器减少了能量输入,在结构2与结构3之间安装弹簧-阻尼器使控制更容易实现。     

部分输入未知条件下结构动力复合反演的分解算法

在充分利用部分输入已确知而部分输入未知的激励特性的基础上，提出了结构动力复合反演的分解算法，该算法从源头上消除了迭代过程中参数识别与荷载反演的相互影响，降低了问题的计算规模。对于线性参数系统，该算法不经过任何迭代计算即可一次性完成结构参数识别及荷载反演。将其与松弛法结合，可解决非线性参数系统的识别问题，与文献[4]的方法比较，其收敛速度有显著提高。     

Bayesian system identification and chaotic prediction from data for stochastic Mathieu-van der Pol-Duffing energy harvester

In this paper, the approximate Bayesian computation combines the particle swarm optimization and sequential Monte Carlo methods, which identify the parameters of the Mathieu-van der Pol-Duffing chaotic energy harvester system. Then the proposed method is applied to estimate the coefficients of the chaotic model and the response output paths of the identified coefficients compared with the observed, which verifies the effectiveness of the proposed method. Finally, a partial response sample of the regular and chaotic responses, determined by the maximum Lyapunov exponent, is applied to detect whether chaotic motion occurs in them by a 0–1 test. This paper can provide a reference for data-based parameter identification and chaotic prediction of chaotic vibration energy harvester systems.     

基于贝叶斯方法的模态参数识别的不确定度分析

振动模态分析和模态参数识别是动态测试的一个重要研究方向。模态参数在模型的修正、响应的预测、系统的健康检测及控制等方面有着重要的作用。但动态测试的不确定度分析,尤其是模态参数的不确定度的研究还十分缺乏。本文主要基于贝叶斯方法,通过傅立叶变换(FFT)建立时域数据和频域数据之间的对应关系。根据共振频带内的多个模态的响应数据得到相对应的模态参数,优化得到模态参数的最佳估计值,评定模态参数识别的不确定度。在固支梁的模态实验中,加速度传感器采集环境激励中的振动数据,运用贝叶斯法进行处理得到模态参数的最佳估计值。在此基础上,通过模态参数的最佳估计值,以及仪器的检定报告数据,结合合成不确度分析方法,系统分析了模态参数识别的不确定度。     

进口受控非定常来流同振荡叶栅相互作用的Euler方程数值解

将 Dcnton 的四角点有限面积格式用于求解变换坐标系下的非定常 Euler 方程组,在振荡叶片附近局部子域构造了一种按等差级数分布的动态网格,从而节省了计算时间,对于本方法的正确性进行了初步检验并与相应的实验进行了对比,在进口总压简谐振荡的束流条件下,计算了零安装角平板叶栅和53°安装角双凸叶栅扭转振荡的非定常流场,结果表明,进口受控扰动同振荡叶栅之间的相互作用在有压力梯度的情况下可以定性地改变叶栅的气动阻尼。