计及弯曲刚度的印刷运动薄膜横向振动控制研究

研究了不同边界条件下,计及弯曲刚度的轴向运动薄膜横向振动的主动控制问题.建立计及弯曲刚度的印刷运动薄膜的计算模型.利用有限差分法,对轴向运动薄膜的振动微分方程进行离散,推导出轴向运动矩形薄膜横向振动控制系统的状态方程.采用次最优控制法,对不同边界条件下轴向运动矩形薄膜横向振动进行主动控制研究.计算结果表明:采用次最优控制法能够在短时间内迅速、有效地降低运动薄膜的振动强度,并使之衰减趋近于0.作动器作用在固定位置点处时,对运动薄膜施加控制后,四边简支边界条件下的控制效果好.作动器作用在不同位置点处时,两种边界条件下中心点处的控制效果最好.计算证明次最优控制法能够有效地抑制印刷过程中计及弯曲刚度的轴向运动薄膜的横向振动,从而提高印刷套印精度,保证精密印刷质量.     

压电曲壳结构的形状控制和优化设计

研究了使用最少和最合理的压电片布置,以及最合理的多点输入电压,对曲壳类结构实施最佳的形状控制.首先,采用HS-ANS法,构造能够克服剪切自锁、梯形自锁和厚度自锁的压电曲壳结构实壳单元.然后,利用遗传算法的组合优化,对作动器的数目和位置进行设计,进一步利用遗传算法的数值优化,对各作动器的作用电压值进行优化,并给出一般计算过程.最后的算例表明,给出的实壳单元和优化设计方法,可以非常有效地实现对曲壳类结构的形状控制.     

船舶机械减隔振技术与计算方法研究综述

针对船舶机械系统，介绍了隔振方法和吸振方法：包括浮筏隔振系统、动力吸振器的概念、应用背景和研究现状；同时介绍了被动控制、主动控制的概念和发展情况.梳理了新型智能材料和新型结构形式，介绍了“准零刚度”隔振器、声学黑洞结构、智能材料作动器、主动和半主动吸振器等控制元件的概念、使用工况和发展，概述了主动控制的控制方法.讨论了机械减隔振系统建模、计算、试验的理论数值方法.最后总结和展望了船舶机械减隔振系统的发展方向.     

压电堆叠作动器的对称性求解

研究了压电堆叠作动器的对称性,并给出了系统存在的守恒量和对称性解.以轴向运动的压电堆叠作动器为研究对象,根据其结构特点,选取位移和磁链作为广义坐标,运用能量方法,建立了压电堆叠作动器的Lagrange(拉格朗日)方程.引入位移和磁链广义坐标的无限小群变换,分别研究了压电堆叠作动器的Noether对称性和Lie对称性,给出了广义Noether恒等式、广义Killing方程、广义Noether定理和Lie定理,计算了压电堆叠作动器存在的Noether对称性和Lie对称性的生成元,并给出了相应系统存在的守恒量.最后,利用得到的守恒量,给出了压电堆叠作动器对称性解,并计算了在控制电压变化的情况下位移和速度的动态响应曲线.     

气-液横向流动下悬臂柱体结构涡激振动机理研究北大核心CSCD

针对潜艇侦查望远镜举升水面时产生的涡激振动现象,该文建立了悬臂柱体结构受气-液两种不同横向流作用下的涡激振动理论模型.研究了两种流体不同的分布比和密度比对柱体结构涡激振动行为的影响规律.基于Galerkin法和Runge-Kutta法,得到了柱体结构涡激振动响应的数值结果.研究表明,柱体结构的涡激振动锁频区随着流体分布比的增大而增大,自由端最大幅值随着流体分布比的增大先增大后减小.当分布比为0.5附近时,振幅出现极大值,该极大值随着流体密度比的减小呈现明显的增大趋势.此外,柱体的动力学行为随着流体分布比的变化呈现出周期和多周期等振动模式.该研究可为潜艇侦查望远镜结构的设计与分析提供理论指导意义.     

群对称桁架振动设计的半正定模型与降维问题(英)

桁架振动优化设计可描述为：在给定振动系统最低频率的约束条件下,设计用材最省的桁架结构. 本文针对具有某种结构对称性的桁架,利用有限群描述这一特性,在已有桁架设计的半正定规划模型基 础上,运用最近提出的矩阵代数方法对半正定规划问题的决策变量和数据进行降维,给出了构造有限群 表示的两个充分条件,并实现了一类群对称桁架振动优化设计的半正定模型降维.基于问题的实际背景, 我们又考虑了一个具有八根弹性棒的桁架设计实例,进一步说明在实际问题中根据群对称构造群表示以 及对应不可约表示的具体方法.     

六维系统环形桁架天线的非线性动力学分析

随着科技的发展,大尺度、低重量、易收拢、高精度等特点是未来天线的主要发展方向.环形桁架天线在发射时整体处于收拢状态,升空后按指令有顺序展开,节省了航天器的空间.此外,环形桁架天线可根据需求设计展开口径的大小.所以,环形桁架天线是目前较为理想的天线结构形式.由于自身结构特点以及复杂的空间环境因素,天线在运行时易产生大幅度的非线性振动,严重影响卫星的稳定运行.因此,将环形桁架天线简化成等效圆柱壳模型,并建立其动力学方程.采用理论分析和数值模拟研究了六维系统环形桁架天线的非线性动力学特性.利用规范型理论化简系统方程分析未扰系统和扰动系统的非线性动力学行为,利用能量相位法验证环形桁架天线系统具有Shilnikov型多脉冲混沌运动,利用数值模拟验证理论分析.并通过数值模拟研究了热激励对环形桁架天线系统非线性振动的影响.     

智能空间刚架的模糊自抗扰振动抑制研究

智能空间刚架作为太空望远镜支撑架是一种新型智能空间结构.为抑制刚架系统在运动过程中产生的振动,"文章提出了一种基于自抗扰控制的非线性模糊自抗扰控制理论,并设计出模糊自抗扰控制器.首先采用有限元方法计算出空间刚架的质量矩阵、阻尼矩阵和刚度矩阵,进而建立系统模型并设计出自抗扰控制器以实现对系统振动的抑制.基于普通自抗扰控制器,利用模糊推理在线整定控制器中非线性状态误差反馈的参数.该控制器不依赖于被控对象的精确数学模型,具有良好的控制性能,同时参数的在线自整定简化了调参难度.仿真实验验证了所提方法的有效性.     

线性主动结构及模态(Ⅱ)——离散系统及梁

在“线性主动结构及模态(Ⅰ)”中给出了主动结构的基本概念及模态的若干属性的基础上,对主动离散系统及主动梁的属性做了进一步的讨论,包括稳定性和正交性,并用具体实例对模态做了解释．将伴随结构概念在梁结构中推广,具体讨论了两种配置的主动梁,它们分别代表离散传感和作动及分布传感和作动的配置,并给出了用主动梁振型和伴随主动梁振型表示的正交性条件．用实例给出了同位和非同位主动刚度梁的特征值随反馈大小的变化．     

横向流激励下绳索的扩张和回转运动

基于横向流激励下绳索的微段受力分析,建立了横向流体对绳索作用力的解析表达.借助坐标变换,将绳索的运动表示为扩张和回转两部分.在此基础上,分析了小垂跨比绳索的流激振动问题,对无伸张态临界流速、平衡解稳定性、重力对绳索运动的影响等问题进行了讨论.     

Optimal scanning control of flexible structures in two-dimensional space

A class of optimal control problems for hyperbolic systems in two-dimensional space is considered. An approach is proposed to damp the undesirable vibrations in the structures by pointwise moving force actuators extending over the spatial region occupied by the structure. A class of performance indices is introduced that includes functions of the state variable, its first and second-order space derivatives and first-order time derivative evaluated at a preassigned terminal time, and a suitable penalty term involving the control forces. A maximum principle is given for such general scanning control problem that facilitates the determination of the unique optimal control. A solution method is developed for the active vibration control of plates of general shape. The implementation of the method is presented and the effectiveness of a single moving force actuator is investigated and compared to a single fixed force actuator by a specific numerical example.     

集成结构振动主动控制和抑制

采用一种新的压电板单元,建立了含有分布压电传感元件和执行元件的集成结构的有限元动力模型。研究了这种集成结构在常增益负速度反馈控制规律作用下,振动的主动控制与抑制的问题,并提出了集成结构振动主动控制和抑制的一般方法。最后,提供了数值示例,说明本文提出方法的有效性。     

Finite volume analysis of adaptive beams with piezoelectric sensors and actuators

This paper presents a finite volume (FV) formulation for the free vibration analysis and active vibration control of the smart beams with piezoelectric sensors and actuators. The governing equations based on Timoshenko beam theory are discretized using the finite volume method. For the purpose of forced vibration control of beam structures, the negative velocity feedback controller is designed for the single-input, single-output system. To achieve the best effect, the piezoelectric sensors and actuators are coupled with the host structure in different positions and then the performance of the designed control system is evaluated for each position. In the test examples, first the shear locking free feature of the present formulation is demonstrated. This has been performed by doing static and natural frequency analysis of some reference models. Then, the capability of the proposed method for the prediction of uncontrolled forced vibration response and active vibration control of a beam structure is studied.     

Extreme optics and the search for Earth-like planets

In this paper I describe a new and exciting application of optimization technology. The problem is to design a space telescope capable of imaging Earth-like planets around nearby stars. Because of limitations inherent in the wave nature of light, the design problem is one of diffraction control so as to provide the extremely high contrast needed to image a faint planet positioned very close to its much brighter star. I will describe the mathematics behind the diffraction control problem and explain how modern optimization tools were able to provide unexpected solutions that actually changed NASA’s approach to this problem. The author was supported by a grant from the ONR (N00014-98-1-0036).     

Parametric optimization of a four-link close-chain manipulator with active and passive actuators

We investigate the problem of optimization of motion laws and design parameters of a four-link manipulator with a closed-chain kinematic structure. The manipulator performs cyclic transfer operations in a horizontal plane under the action of active and passive (springs and dampers) actuators. As a minimization criterion, we take a quadratic (with respect to control moments of forces) functional. An algorithm is proposed for constructing a suboptimal solution of the formulated problem based on parametrization of the generalized coordinates of the manipulator with a family of given functions and on the use of numerical procedures of mathematical programming.     

Nonlinear Analysis and Optimum Design of Guyed Masts

In this paper the nonlinear analysis and design optimization of guyed masts is addressed. The mast is modeled as a 3D truss and is supported by catenary cable elements that have nonlinear elastic behavior. For nonlinear static analysis, an innovative procedure is proposed that divides the structure into linear and nonlinear parts and analyzes them separately. The proposed method satisfies the equilibrium and compatibility by establishing and solution of a set of nonlinear equations. The optimization problem employs the sizes of members, initial cable tensions and the positions of anchor on the ground and tie level of cables on the mast as design variables. To facilitate the optimization solution, a compatible sensitivity analysis procedure is proposed. Sensitivities of objective function, displacement and strength constraints in the mast and cables, subjected to a variety of load combinations including dead, wind and ice loads are calculated. Numerical examples are provided to show the nonlinear analysis procedure and the applicability of the algorithm to optimum design of practical guyed masts.     

Hybrid optimization procedure applied to optimal location finding for piezoelectric actuators and sensors for active vibration control

This paper presents an efficient hybrid optimization approach using a new coupling technique for solving the constrained optimization problems. This methodology is based on genetic algorithm, sequential quadratic programming and particle swarm optimization combined with a projected gradient techniques in order to correct the solutions out of domain and send them to the domain’s border. The established procedures have been successfully tested with some well known mathematical and engineering optimization problems, also the obtained results are compared with the existing approaches. It is clearly demonstrated that the solutions obtained by the proposed approach are superior to those of existing best solutions reported in the literature. The main application of this procedure is the location optimization of piezoelectric sensors and actuators for active control, the vibration of plates with some piezoelectric patches is considered. Optimization criteria ensuring good observability and controllability based on some main eigenmodes and residual ones are considered. Various rectangular piezoelectric actuators and sensors are used and two optimization variables are considered for each piezoelectric device: the location of its center and shape orientation. The applicability and effectiveness of the present methodological approach are demonstrated and the location optimization of multiple sensors and actuators are successfully obtained with some main modes and residual ones. The shape orientation optimization of sensors observing various modes as well as the local optimization of multiple sensors and actuators are numerically investigated. The effect of residual modes and the spillover reduction can be easily analyzed for a large number of modes and multiple actuators and sensors.     

GLOBAL CONVERGENCE AND IMPLEMENTATION OF NGTN METHOD FOR SOWING LARGE-SCALE SMRSE NONLINEAR PROGRAMMING PROBLEMS

1. IntroductionConsider the following NLP problemwhere the function f: Re --+ RI and gi: Re - R', j E J are twice continuously dtherentiable.In particular, we discuss the cajse, where the nUmber of variables and the nUmber of constraintsin (1.1) are large and second derivatives in (1.1) are sparse.There are some methods whiCh can solve largesscale problems, e.g. Lancelot in [2] andTDSQPLM in [9]. But they can not take adVantage of sparse structtire of the problem. A newefficient meth…     

Optimal control of an elastically connected rectangular plate–membrane system

The optimal control of an elastically connected rectangular plate–membrane system by point-wise actuators is considered. Problems of the type are of significant practical interest in most real mechanical structures widely used in aeronautical, civil, naval, and mechanical engineering. An index of performance is formulated, which consists of a modified energy functional of the two coupled structure at a specified time and penalty functions involving the point control actuators. Necessary conditions of optimality are derived in the form of independent integral equations which lead to explicit expressions for the point-wise actuators. The results are applied to a specific problem, and numerical results are given that reveal the effectiveness of the proposed control mechanism.