自适应桁架结构天线形状最优控制

给出了两种含压电作动杆的自适应桁架抛物面天线的形状最优控制方法,分别以天线表面点相对原设计抛物面和最佳吻合抛物面(BFP)的光程差为精度指标,建立了同时考虑精度和能耗的综合控制目标。控制考虑杆件轴力与作动电压限制,以作动电压为被控量。利用桁架力学量及天线精度与作动电压的关系,将控制问题精确表达为显式数学规划问题。理论分析和仿真结果均说明基于BFP的控制方法在天线精度和能量消耗方面的优越性,最后通过仿真算例讨论了结构受载形式和电压限设定对天线形状控制能力的影响。     

位移约束下智能桁架的强度最优控制

针对智能桁架结构,提出了在考虑多点位移约束的情况下,使结构工作应力处于最佳状态的规划法最优控制模型。当结构位移约束起主要作用时,模型可在保证位移约束的前提下,同时尽可能提高结构的承载能力;当结构位移并不重要时,仍可用该模型来提高结构的承戴能力。对于复杂结构,为了提高控制效果,可以调整为了满足位移条件而需要的作动器数目及布置方案。文中给出了数值算例,说明该方法的调控能力。     

压电复合材料层合板自适应结构的振动控制

本文针对板壳型自适应结构,研究了压电材料作为作动器的自适应结构的振动控制。利用四节点压电复合材料层合板单元进行自适应结构的有限元动力分析;采用模态控制方法,将结构的各阶模态的阻尼比作为控制目标,并以此计算出各压电片的控制电压,达到控制结构振动的目的。算例给出了数值计算的结果。     

大型索网天线机电耦合动力学建模与主动变形控制

索网天线因其折叠收纳比高、质量轻以及口径大等优点,成为众多空间任务的首选天线形式,但反射面精度较低限制了大型索网天线的在轨性能指标。在索网天线竖向张力索中加入压电陶瓷堆(PZT)作动器,通过主动控制提高反射面的形面精度。首先,将张紧的索网天线分为含有作动器的主动索单元和不含作动器的被动索单元,通过压电本构方程、几何方程和哈密顿原理推导出主动索单元的动力学模型,并与被动索单元一起组装得到索网天线的机电耦合动力学模型。然后,根据天线反射面的初始形面误差和所建立的天线机电耦合动力学模型,基于模型预测控制(MPC)方法计算出各作动器的控制输入电压曲线。最后,以一个10m口径的索网天线为算例,验证本文所建立的模型和控制方法的有效性。     

层合结构压电器件的机电耦合响应

压电传感嚣和致动器都可以看成是由压电材料层和非压电(弹性)材料层交替铺设而成。对于这类任意铺设的层合板悬臂梁结构,推导出了表示力学变形与外加电场之间耦合效应的解析表达式。进而,又推导出了两类(一类为单层压电-弹性层。另一类为双层压电-弹性层)层合型悬臂梁结构机电耦合性能的解析公式。在该机电耦合模型中,包括了两个压电常数d211和d222。最后。通过比较解析解、实验值以及有限元计算结果,发现它们吻合得很好。     

Robust adaptive control of nonholonomic systems with uncertainties

Robust adaptive control of nonholonomic systems in chained form with linearly parameterized and strongly nonlinear disturbance and drift terms is dicussed. The novelty of the proposed method is a combined use of the state-scaling and the back-stepping procedure.     

Neural network-based adaptive control of a class of uncertain nonlinear systems

I.ProblemF0muIationandAssumptionsConsiderthenonlinearsystemfwhereeeR-isthestate,andavailableformeasurement,'.ERistheinput,geRistheoutput.hisasmoothfunctiononR-withh(0)=O,andthevectorfieldsI',g"aresmo0thonR-withg'(x)*O,VxeR--andI'(O)-O.ForcIarity0fexpositi…     

Fluid‐structure coupling of linear elastic model with compressible flow models

Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure.     

作动器参数对结构性能的影响和调整受力状态的实施策略模拟

基于规划法研究了作动器各参数对自适应超静定桁架性能的影响。该规划法能够使结构工作状态更合理化。这一方法能够改善自适应结构的工作状态因而提高承载能力。以此为基础，研究了具有作动器的组合杆的有关参数诸如变形上限、刚度和承载力上限对于控制效果的影响。从而为作动器的合理选择提供了理论根据。对于调整作动器变形以控制结构强度的实施策略进行了模拟和分析。该策略包括3部分：1．模拟和分析了“加载、调控、卸载”重复循环直至调控的完成；2．不同作动器按比例同时放大变形直到调控实现；3．多次加载、调控同一次加载、调控结构的等价性。研究表明本文提出的使结构工作状态合理化的调控过程是安全、可靠和灵活的。     

时变通信延迟下的无人机编队鲁棒自适应控制

在时变通信延迟下研究了无人机群编队的鲁棒自适应控制问题。对于无人机编队系统中存在外部扰动和模型不确定性的情况,通过选取包含位置跟踪误差和速度跟踪误差的辅助变量,提出了一种适用于时变通信延迟的鲁棒自适应编队控制策略。提出了自适应律对无人机质量、外界扰动的上界等未知参数进行估计,并且利用Lyapunov稳定性理论分析了闭环系统的渐近稳定性,给出了系统渐近稳定所需要满足的条件。数值仿真结果表明,所提出的控制方法既能抑制外界扰动和模型不确定性对控制器的影响,同时队形跟踪和队形保持的稳态误差分别小于0.1 m和0.05 m。     

考虑控制延时影响的相邻建筑结构的离散变结构振动控制方法

研究了基于离散变结构控制算法的考虑控制延时影响的相邻建筑结构体系地震反应半主动控制的基本设计和计算方法。首先,建立了相邻结构体系的力学模型及连续运动状态方程,并将其离散化成标准离散状态方程形式。其次,简要地讨论了离散变结构控制器的设计方法,包括切换平面的选择及离散趋近率的构成．最后,应用本文方法对主楼12层,裙房5层的实例结构进行了数值仿真分析,结果表明,该控制方法不仅能有效抑制相邻结构地震反应的鞭梢效应,而且在控制延时存在的情况下,仍能保证系统的减震性能和稳定性。     

Outer synchronization of uncertain small-world networks via adaptive sliding mode control

The outer synchronization of irregular coupled complex networks is investigated with nonidentical topological structures. The switching gain is estimated by an adaptive technique, and a sliding mode controller is designed to satisfy the sliding condition. The outer synchronization between two irregular coupled complex networks with different initial conditions is implemented via the designed controllers with the corresponding parameter update laws. The chaos synchronization of two small-world networks consisting of N uncertain identical Lorenz systems is achieved to demonstrate the applications of the proposed approach.     

压电智能结构模糊自学习控制(FSLC)

将模糊逻辑与学习控制的基本思想相结合,根据控制系统的动态输出特性,采用模糊控制对学习控制律中的参数进行实时校正,实现系统的动态学习过程,提出了一种适用于压电智能结构振动控制的模糊自学控制方法FSLC（FuzzySelf-LearningContr01）。分别采用三维8节点实体单元（Solid45）和耦合单元模拟主结构和压电致动器／传感器,基于ANSYS参数化语言编写了压电智能结构振动控制分析的有限元程序。通过数值仿真证明了模糊自学习控制方法能有效控制压电结构的振动,并提高了自学习控制的收敛速度和获得了很好的控制效果。     

Dynamics and control of a self-sustained electromechanical seismographs with time-varying stiffness

This paper is concerned with the nonlinear dynamics and vibration control of an electromechanical seismograph system with time-varying stiffness. The instrument consists of an electrical part coupled to mechanical one and is used to record the vibration during earthquakes. An active control method is applied to the system based on cubic velocity feedback. The electromechanical system is subjected to parametric and external excitations and modeled by a coupled nonlinear ordinary differential equations. The method of multiple scales is used to obtain approximate solutions and investigate the response of the system. The results of perturbation solution have been verified through numerical simulations, where different effects of the system parameters have been reported.     

基于指数收敛的四旋翼无人机鲁棒自适应飞行控制

针对四旋翼无人机鲁棒自适应飞行问题,提出了一种基于指数收敛的控制方法。考虑到四旋翼系统的欠驱动、强耦合等非线性特性,采用线性化反馈控制策略实现对其轨迹追踪飞行能力的基本控制;针对线性化反馈控制易受系统内外部未知干扰等影响,采用基于指数收敛干扰观测器组合控制设计,实现四旋翼飞行的鲁棒与自适应控制;线性反馈及状态观测器控制系统基于指数收敛稳定。进行了仿真分析,结果表明,干扰观测器对四旋翼系统中存在的未知干扰具有很好的估计能力,所设计的基于指数收敛控制系统,结构简单,且具有较强的干扰抑制能力和较高的系统稳定性,满足四旋翼无人机的鲁棒及自适应飞行能力要求。     

Improving the CBS‐based partitioned semi‐implicit coupling algorithm for fluid‐structure interaction

We detail in this work 2 simple but effective alternatives to improve the characteristic‐based split–based partitioned semi‐implicit coupling algorithm for fluid‐structure interaction. The basic idea lies in introducing the end‐of‐step velocity into the implicit stages of the 2 algorithms integrating different splits. The algorithm built upon the second‐order pressure split is further stabilized via the pressure gradient projection with particular emphasis on the extremely low mass ratio. The smoothed finite element method is exploited for spatial discretization of fluid and solid equations. Even without any accelerators, both the semi‐implicit solvers incorporating fixed‐point iterations engender visible improvements versus the previously published data for several benchmarks.     

STUDY ON COUPLING MODEL OF SEEPAGE-FIELD AND STRESS-FIELD FOR ROLLED CONTROL CONCRETE DAM

IntroductionRCCDisbuiltwithconcreterolledandcompactedlayeruponlayer.Therefore,thereisonehorizontalconstructioninterfacebetweentwoconterminouslayers.Iftheconterminouslayersarenotcementedclosely ,theconstructioninterfaceswillbecomeweakpartsofRCCDthatinfluencethestrengthandstabilityofRCCD .Ontheotherhand ,theanti_seepageabilityofconstructioninterfacesisthedeterminantofanti_seepagecharacteristicsofthewholeRCCD .Whenadamisconstructedandfilledbywater,seepage_fieldcomesintobeinginthedambody ,w…     

空间机器人执行器自适应分散容错控制算法设计

针对执行器发生部分失效故障的漂浮基空间机器人系统,提出了一种自适应H_∞分散容错控制算法。利用拉格朗日第二类方程建立了系统的动力学模型。根据分散原理将系统分解为以基座或臂杆为单元的多个子系统,并将表示执行器控制能力的有效因子融入到每个子系统,使得单个子系统的执行器故障不会影响相邻执行器的正常运行。通过对每个故障子系统设计形式一致的自适应容错算法实现对整个系统的容错控制。仿真结果表明,与现有某非奇异终端滑模容错算法相比,本文算法具有更快的跟踪速度和更高的跟踪精度。     

Variable structure control of indefinite-dimensional systems

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Synchronization in a fractional-order dynamic network with uncertain parameters using an adaptive control strategy

This paper studies synchronization of all nodes in a fractional-order complex dynamic network. An adaptive control strategy for synchronizing a dynamic network is proposed. Based on the Lyapunov stability theory, this paper shows that tracking errors of all nodes in a fractional-order complex network converge to zero. This simple yet practical scheme can be used in many networks such as small-world networks and scale-free networks. Unlike the existing methods which assume the coupling configuration among the nodes of the network with diffusivity, symmetry, balance, or irreducibility, in this case, these assumptions are unnecessary, and the proposed adaptive strategy is more feasible. Two examples are presented to illustrate effectiveness of the proposed method.