轴向运动弦线横向振动的线性反馈控制

研究轴向运动弦线和作动器组成的耦合系统的横向振动控制。此系统被作动器分成未控和受控两部分,通过作用在作动器上的控制力对受控部分的横向振动进行控制。采用能量方法获得反馈控制规律,得到两种控制力,并用半群理论证实受控弦线横向振动的渐近稳定性和指数稳定性。在初始扰动和激励力作用下,通过数值仿真证实控制规律的有效性。     

轮带系统横向振动的行波消去法

考虑作动器中张紧轮质量的影响,研究轴向运动弦线和作动器所组成的耦合系统的横向振动控制。此系统被作动器分成受控和未控两部分,在频域内利用Green函数法求解出系统的响应,采用行波消去法设计出控制律。在初始条件和激励作用下,利用Durbin拉氏变换数值反演法将受控系统的振动响应转化到时域内,并利用Matlab进行数值仿真。算例结果表明:在脉冲激励和正弦激励作用下,系统振动在3秒内分别减小到0和未受控制时的1/5,验证了控制律的有效性。     

大型客机后缘襟翼操纵与非对称控制

针对大型客机后缘襟翼操纵与非对称控制的复杂结构及运动机构动力学仿真问题,通过零部件模态综合法建立刚柔混合多体动力学模型,替代传统的有限元法,综合考虑结构柔性、关节轴承摩擦、滑轮架摩擦、机翼盒段变形协调支持边界影响,实现了大型客机后缘襟翼在空中多状态/多工况载荷综合作用下的仿真分析．总体上看,仿真计算的各作动器驱动载荷变化规律与试飞结果一致,驱动载荷最大值误差小于10 %．受内襟翼靠近机身部分的翼面风洞测压数据及机身变形支持边界等不确定因素影响,初始启动和襟翼小偏度时各作动器操纵载荷仿真结果与试飞结果相对误差偏大．通过数值仿真,进行后缘襟翼单作动器脱开故障的非对称控制需求及其交联装置动态冲击过程分析,仿真结果表明内外襟翼交联装置可以有效减小后缘襟翼单作动器脱开故障非对称变形影响．     

密集模态挠性结构传感器/作动器的优化配置

在适当的假设条件下,推导出了压电作动器产生的弯矩与输入电压的关系式及压电传感器输出电压与输入弯矩的关系,进而得到H型密集模态挠性板模型的状态空间表达式,并由此模型出发,采用一种基于能量的传感器/作动器的优化配置策略,该准则可以很自然地研究整个动态模型的可控性和可观性,进而确定传感器/作动器的位置。针对H型密集模态挠性板振动主动控制的数值仿真表明了该准则的有效性。     

层叠式PVDF压电作动器及圆柱壳的振动主动控制

设计了一个层叠式PVDF压电作动器用于壳结构的振动控制。考虑压电层、粘接层、壳体耦合关系,推导了表面局部粘贴层叠式PVDF压电作动器的圆柱壳的振动控制方程,给出了作动力与压电层和粘接层层数、厚度之间的关系以及作动力与作动器粘贴位置之间的关系。针对一端固定、另一端自由的圆柱壳,进行了振动控制仿真。结果表明层叠式PVDF压电作动器作动力与作动器层数近似成线性关系,增大作动器层数能有效增大作动力,在低控制电压下能显著抑制圆柱壳振动,作动器周向不完全粘贴时,在径向产生的径向作动力对壳体横向振动控制非常有利。说明了层叠式PVDF压电作动器是一种可用于壳体结构振动并具有良好作动效果的作动器。     

一种新型压电作动器的设计及其特性研究

提出了一种新型压电作动器,这种作动器由一片压电片粘贴在一个弓型梁金属底座上构成.对其变形放大原理进行了理论分析,实验测定了这种压电作动器自由状态下输出变形随驱动电压变化曲线.推导了约束状态下该作动器的输出作动弯矩与驱动电压的关系式;实验测得了约束状态下其中点位移响应幅频特性曲线.实验结果表明本文设计的新型压电作动器与传统压电片作动器相比具有较大的变形输出,具有较宽的稳定工作频率范围,而所需的驱动能量与传统压电片作动器相同,同时在使用上具有可预制、安装方便、可拆卸、对结构表面适应性好等优点.     

主动控制用大输出力电磁作动器优化设计

采用将电磁作动器集成至气囊隔振器内部的方式能够很好地实现宽频隔振与线谱控制,但由于气囊内的空间有限,作动器在有限的空间内其体积要尽可能小的同时,还要输出足够大的主动控制力,这对主动控制用大输出力电磁作动器的优化设计提出了更高的要求。建立了电磁作动器的理论模型与漏磁模型;采用ANSYS有限元软件中的优化模块对电磁作动器进行了优化设计,并获得了符合结构尺寸与主动控制输出力要求的作动器;分析了电磁作动器的可控输出力与最大磁饱和密度随电流变化的关系。仿真结果表明,设计的电磁作动器在满足空间尺寸的前提下,通入6A交变电流时其输出的主动控制力能够达到646N,满足设计指标,有助于作动器的研制。     

磁致伸缩作动器的电-磁-机耦合动力特性

基于磁致伸缩材料的本构关系模型,结合磁致伸缩作动器结构动力学模型建立了可描述磁致伸缩作动器的电-磁-机耦合动力特性的运动方程.方程中考虑了作动器工作时磁致伸缩材料的弹性模量随着应力和磁场的改变而发生的变化,磁致伸缩材料的这种特性使得作动器系统表现出具有时变刚度的参数振动特性.通过对此参数振动方程进行数值求解,得到磁致伸缩作动器的参数频响特性,并研究了激励电流幅值以及作动器负载质量对作动器频响特性的影响.     

振动控制作动器的数目和位置优化设计

提出一种确定作动器的数目和优化设计作动器位置的方法。以独立模态最优控制方法为基础,将模态控制力和作动器作动力处理为随机变量,建立了模态控制力能量的自相关矩阵和作动器作动力能量的自相关矩阵。进一步通过作动力能量的自相关阵包含的能量确定了作动器的数目,在此基础上,建立了基于控制系统作动力消耗能量最小,优化设计控制系统的作动器最优位置。通过数值算例证明了该方法的有效性。     

基于层叠式平面DE作动器的柔性薄壁结构振动控制研究

为了降低单层平面DE作动器的控制电压,提出了一种层叠式平面DE作动器,并开展了基于层叠式平面DE作动器的柔性薄壁结构振动主动控制研究。结合介电弹性体(DE)材料的力电耦合模型,基于哈密顿变分原理,建立了含层叠式平面DE作动器的柔性悬臂梁系统振动控制微分方程。基于比例反馈控制策略,利用不同层数的层叠式平面DE作动器对悬臂梁系统进行了振动主动控制的仿真研究。结果表明,层叠式平面DE作动器对柔性薄壁结构具有良好的振动控制效果,同时相比于单层平面DE作动器,控制所需电压可以降低30%以上,从而为DE作动器的低电压驱动应用提供了一条可行的技术途径。     

Design of an Active Noise Control System Using a Distributed Actuator

A distributed acoustic actuator for active noise control, consisting of a piezoelectric PVDF film, bonded at each side of a carrier structure, is simulated and built. The piezoelements are driven in anti-phase, resulting in a bending motion of the actuator, and thus in the necessary out-of-plane displacement for sound radiation. An analytical model for the acoustic actuator is derived, relating the actuator's displacement to the applied voltage, taking into account the influence of the piezoelectric film on the actuator's stiffness. The model is used to optimise the specifications for the piezoelectric film and the carrier structure, resulting in the highest sound power output in a frequency range from 30–500 Hz. An analytical model for the behaviour of a double panel partition is derived. The analytical model is combined with the model for the acoustic actuator, describing an actively controlled double panel partition with a distributed acoustic actuator integrated in the cavity. A controller is added to the system to control the sound power transmitted through the double panel partition. Simulation results show that a substantial increase of transmission loss can be achieved in the low frequency region (30–500 Hz) with this configuration. This revised version was published online in July 2006 with corrections to the Cover Date.     

自适应结构多工况下强度控制的研究

对自适应超静定桁架结构的强度控制问题进行了研究，把模型从单一工况推广到了多工况，实现了理论的完整性，定义了结构工作状态系数， 分析了作动器的联入对结构强度的影响，利用超静定桁架的耦合特性和作动器的调节功能，把强度控制问题转化为数学规划问题，方法简单有效。     

Spherical-symmetric steady-state response of piezoelectric spherical shell under external excitation

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“Equivalent” Electromechanical Coefficient for IPMC Actuator Design Based on Equivalent Bimorph Beam Theory

This paper addresses an “equivalent” electromechanical coupling coefficient that may be used in designing Ionic Polymer Metal Composite (IPMC) actuators. The coefficient is not a material constant and derived from equivalent bimorph beam model. The collective effect of the membrane thickness and operating voltage on the coefficient is demonstrated by using a design of experiment (DOE) of three and five levels of the two factors, respectively. Experiments and linear finite element analyses with MD.NASTRAN at DOE points are performed. The tip displacement and the coupling coefficient are reported and their response surface (RS) approximations as function of the thickness and voltage are constructed. Experiments and RS predictions indicate that actuator thickness and applied voltage are two interacting major factors for maximum tip displacement. The equivalent coupling coefficient is primarily driven by the thickness of actuator moreover voltage appears to contribute as the thickness increases. The initial curvature of the strips before electrical excitation is also shown to be a factor for “equivalent” coupling coefficient, it is not, however sufficient to explain the variation in the experimental data. A correction factor approach is proposed and applied to the straight beam tip displacement RS that filters out experimental variation. A corrected RS enables including the pre-imposed initial curvature as design parameter along with the actuator thickness and the operating peak voltage when predicting the tip displacement and the equivalent coupling coefficient.     

弹性板振动的多模态主动控制

采用多对压电片对板振动的多阶模态进行主动控制。为了改善结构振动控制的效果，本文对选用结构振动能量和控制信号能量作为控制目标函数的LQR控制算法作了初步研究。首先，按能量准则推导了控制目标函数中权系数矩阵(Q矩阵和R矩阵)的理论计算公式，为权系数矩阵的选取提供了一定的理论依据。然后，运用该算法，在研究了单对压电片进行振动主动控制的基础上．本文深入分析了压电层合板振动的多阶模态控制的问题，用Matlab进行系统仿真，得到了压电层合板受到初始位移激励下板中心点的位移和控制电压大小随时间变化的曲线。数值模拟的结果表明，该方法能达到更有效控制结构振动和减小控制能量消耗的目的．进一步验证了该方法能达到有效控制结构振动和减小控制能量消耗的目的。     

PI force feedback control for large flexible structure vibration with active tendons

Active tendon, consisting of a displacement actuator and a collocated force sensor, was first presented by Preumont and his co-workers to attenuate the vibration of large flexible space structures, and the control algorithm adopted by them was integral force feedback. This paper presents a new proportional-integral （PI） force feedback algorithm to achieve larger damping ratios for the structure without the requirement of structure model. Stability of the control system is shown, and simulations of a structure similar to JPL-MPI demonstrate the effectiveness of the proposed algorithm for vibration control of space structures.     

Thermally induced fracture of a smart functionally graded composite structure

Discussed is the fracture behavior of a cracked smart actuator on a substrate under thermal load. The actuator is made of piezoelectric material with functionally graded material (FGM) properties. Integral transform method is used to reduce the problem to the solution of a set of singular integral equations and is solved numerically. This paper is completed by including graphical plots of the thermal flow, stress and electric displacement intensity factors around the crack for different crack positions and material gradients. Directions of crack initiation are also predicted by using the energy density criterion.     

A 3D Displacement Control by Digital Image Correlation for the Multiaxial Testing of Materials with a Stewart Platform

A Digital Image Correlation technique is proposed to control a quasi-static 6 degrees of freedom testing machine. This machine is based on a hexapod architecture, allowing displacements of several tens of centimeters and degrees, and with force capacities of several tens of kN and kN.m. The control technique is based on the measurement of the set of actuator lengths, from images of the end-effector of the machine. A firstattempt is shown with a single camera. Thoughrelevant, the results present too high uncertainties for the aimed applications. Several cameras are then used to improve the 3D rigid body motion displacement measurement of the end-effector. Thecamera positions are free, with an automatic calibration method assessing the needed coefficients for the control. The set of actuator lengths is then searched by global minimization of the difference between the current image and the reference image of each camera (i.e., the minimization is not performed independently for each camera). The algorithm is implemented on Graphical Processing Units to achieve computation times lower than 50 ms. An in-depth experimental validation of the whole setup is performed. For an actuator length range of 200 μm, the actuator length uncertainties are around 0.4 μm with 3 cameras. The errors of displacement of the end-effector are less than 2 μm, partially due to the validation setup itself.     

Development, modeling and deflection analysis of hybrid micro actuator with integrated thermal and piezoelectric actuation

Micro actuators are irreplaceable part of motion control in minimized systems. The current study presents an analytical model for a new Hybrid Thermo Piezoelectric micro actuator based on the combination of piezoelectric and thermal actuation mechanisms. The micro actuator structure is a double PZT cantilever beam consisting of two arms with different lengths. The presented micro actuator uses the structure of electrothermal micro actuator in which polysilicon material is replaced by PZT. Also the voltage and poling directions are considered in the lengthwise of PZT beams. As a result, the piezoelectric actuation mechanism is based on d ₃₃ strain coefficient. The tip deflection of micro actuator is obtained using Timoshenko beam theory. Analytical results are compared with FEM results along with other reported results in the literature. The effects of geometrical parameters and PZT material constants on actuator tip deflection are studied to provide an efficient optimization of HTP micro actuator.     

Solid body motion prediction using a unit quaternion-based solver with actuator disk

A six-Dof motion solver based on unit quaternions and an actuator disk model are implemented for ship hydrodynamics predictions. The six-Dof module is tested using the water entry phenomenon of a free falling sphere. The displacement history and impacting forces are analyzed. A KCS (KRISO container ship) model with the allowances of sinkage and trim is then simulated and validated. The actuator disk model is used to replace a real propeller. The open-water test of a KP458 propeller is first carried out to obtain the thrust and torque coefficients, using both the multi-run and single-run approaches. Oblique Towing Tank (OTT) tests using the actuator disk are conducted at last and the results agree well with the experiments. These models can be used for simulating six-Dof motions and captive model tests of ships.