Optimal shape control of functionally graded smart plates using genetic algorithms

This paper deals with optimal shape control of functionally graded smart plate containing patches of piezoelectric sensors and actuators. The genetic algorithm (GA) is designed to search for optimal actuator voltage and displacement control gains for the shape control of the functionally graded material (FGM) plates. The work extends the earlier finite element formulations of the two leading authors, so that it can be readily treated using genetic algorithms. Numerical results have been obtained to study the effect of the shape control of the FGM plates under a temperature gradient by optimising (i) the voltage distribution for the open loop control, and (ii) the displacement control gain values for the closed loop feedback control. The effect of the constituent volume fractions of zirconia, through varying the volume fraction exponent n, on the optimal voltages and gain values has also been examined.     

Active vibration control of composite plate with optimal placement of piezoelectric patches

The active vibration control of a composite plate using discrete piezoelectric patches has been investigated. Based on first order shear deformation theory, a finite element model with the contributions of piezoelectric sensor and actuator patches to the mass and stiffness of the plate was used to derive the state space equation. A global optimization based on LQR performance is developed to find the optimal location of the piezoelectric patches. Genetic algorithm is adopted and implemented to evaluate the optimal configuration. The piezoelectric actuator provides a damping effect on the composite plate by means of LQR control algorithm. A correlation between the patches number and the closed loop damping coefficient is established.     

Optimal placement of piezoelectric actuators on plate structures for active vibration control via modified control matrix and singular value decomposition approach using modified heuristic genetic algorithm

The present work deals with the optimal placement of piezoelectric actuators on a thin plate using modified control matrix and singular value decomposition (MCSVD) approach. The MCSVD is considered as the fitness function and optimal positions of the actuators are obtained by maximizing it with MHGA (modified heuristic genetic algorithm). Vibration suppression has been studied for simply supported plate with piezoelectric patches in optimal positions to suppress first specified modes using LQR (linear quadratic regulator) controller. It is observed that the positions of patches obtained with this approach give greater vibration suppression, reduced computational requirements, and provide global optimum solution only.     

分布参数结构控制中溢出抑制的并行滤波法

提出了并行滤波控制方法抑制分布参数结构主动控制中的溢出。对无穷维分布参数结构,依据有限维降阶模型设计控制器会导致系统闭环性能变差,并有可能使系统失稳。文中针对分布参数结构特性设计了滤波增广结构,对增广系统设计带观测器的状态反馈构成控制器。在给出该方法原理的基础上,提出了并行滤波控制针对被控结构摄动的鲁棒稳定界。仿真算例表明,此方法在保证受控模态控制效果的同时有效地抑制了溢出。     

Analysis of active damping in composite laminate cylindrical shells of revolution with skewed PVDF sensors/actuators

Active damping in a FRP composite cylindrical shell with collocated piezoelectric sensors/actuators is studied. The electrode on the sensors/actuators are spatially shaped to reduce spillover between circumferential modes. A three noded, isoparametric, semianalytical finite element is developed and used to model the cylindrical shell. The element is based on a mixed piezoelectric shell theory which makes a single layer assumption for the displacements and a layerwise assumption for the electric potential. The effects of location of patch of collocated piezoelectric sensors/actuators, percentage length of the shell covered with these patches, fiber angle of the laminae in the composite laminate, stacking sequence of laminae in a laminate and skew angle of the sensor/actuator piezoelectric material, on the system damping for various modes is studied.     

Optimal solid shell element for large deformable composite structures with piezoelectric layers and active vibration control

In this paper, we present an optimal low‐order accurate piezoelectric solid‐shell element formulation to model active composite shell structures that can undergo large deformation and large overall motion. This element has only displacement and electric degrees of freedom (dofs), with no rotational dofs, and an optimal number of enhancing assumed strain (EAS) parameters to pass the patch tests (both membrane and out‐of‐plane bending). The combination of the present optimal piezoelectric solid‐shell element and the optimal solid‐shell element previously developed allows for efficient and accurate analyses of large deformable composite multilayer shell structures with piezoelectric layers. To make the 3‐D analysis of active composite shells containing discrete piezoelectric sensors and actuators even more efficient, the composite solid‐shell element is further developed here. Based on the mixed Fraeijs de Veubeke–Hu–Washizu (FHW) variational principle, the in‐plane and out‐of‐plane bending behaviours are improved via a new and efficient enhancement of the strain tensor. Shear‐locking and curvature thickness locking are resolved effectively by using the assumed natural strain (ANS) method. We also present an optimal‐control design for vibration suppression of a large deformable structure based on the general finite element approach. The linear‐quadratic regulator control scheme with output feedback is used as a control law on the basis of the state space model of the system. Numerical examples involving static analyses and dynamic analyses of active shell structures having a large range of element aspect ratios are presented. Active vibration control of a composite multilayer shell with distributed piezoelectric sensors and actuators is performed to test the present element and the control design procedure. Copyright © 2005 John Wiley & Sons, Ltd.     

基于加速粒子群算法的车辆座椅悬架最优控制研究

针对传统最优线性二次型控制器中加权矩阵往往由设计者根据经验确定的问题,提出一种应用加速粒子群算法确定加权矩阵的方法。建立"车轮-车身-座椅、人体"6自由度随机振动系统模型,采用加速粒子群算法对座椅悬架进行参数优化,并对优化后系统进行最优线性二次型控制。将基于加速粒子群算法的最优线性二次型座椅悬架系统中"座椅、人体"垂向加速度与初始系统及基于常规粒子群算法和遗传算法的最优线性二次型控制系统进行对比,验证了此控制系统的有效性和优越性。     

改进型负输入整形与最优控制结合的振动抑制方法

针对诸如柔性机械臂这类柔性系统的主动振动控制问题,提出了基于改进型负输入整形和最优控制结合的振动抑制方法。以柔性机械臂为研究对象,设计最优状态反馈控制实现其旋转机动任务及柔性振动抑制。为增强柔性振动抑制效果和改善系统的运动时间,根据引入线性二次型调节器(LQR)反馈后整个闭环系统的振动频率和阻尼比设计改进型负输入整形器作为前馈控制器。将前馈控制与反馈控制相结合能发挥其各自的优点,提高系统的性能。仿真分析结果表明,所设计的混合控制策略可以有效地抑制柔性振动,且可以减少系统响应时间的延迟和加快系统响应速度。     

有约束随动系统控制策略研究

提出了一种新的有约束的复杂随动系统--小碗摆球系统,并针对该系统利用达朗伯静力学的方法进行了建模。在讨论了系统能控和能观性的基础上分别采用状态反馈的极点配置法和基于遗传算法的LQR最优控制2种方法进行了实际系统控制效果的实验对比,通过对比可知极点配置的状态反馈控制器具有更好的鲁棒性和瞬态特性,而遗传算法优化的LQR控制具有更好的稳态特性,以及更短的调节时间。同时在参数选择方面相比于极点配置试特征值的方法,遗传算法优化LQR控制控制器更有针对性,便于实际的应用操作。     

基于最小二乘支持向量机的结构地震响应时滞控制算法

针对时滞会导致控制系统效果降低、控制性能恶化甚至系统不稳定,将线性二次型控制（Linear Quadratic Regulator,LQR）与最小二乘支持向量机（Least Squares Support Vector Machines,LSSVM）进行集成,提出时滞LSSVM-LQR智能控制算法。该算法采集结构状态响应数据后,将用LQR算法计算出的结构最优控制力输入到LSSVM中,以训练并回归预测出时滞后时刻的最优控制力;由作动器对结构提供控制。基于MATLAB平台编写计算程序,并用一幢三层框架结构进行数值验证。结果表明,LSSVM-LQR算法能有效降低时滞对结构控制系统的不利影响。     

Active control of FGM shells subjected to a temperature gradient via piezoelectric sensor/actuator patches

A generic static and dynamic finite element formulation is derived for the modelling and control of piezoelectric shell laminates under coupled displacement, temperature and electric potential fields. The base shell is of functionally graded material (FGM) type, which consists of combined ceramic–metal materials with different mixing ratios of the ceramic and metal constituents. A multi‐input–multi‐output (MIMO) system is applied to provide active feedback control of the laminated shell using self‐monitoring sensors and self‐controlling actuators through a close loop. Numerical studies clearly show the influence of the positional configurations of sensor/actuator pairs on the effectiveness of static and dynamic control for the shell laminates. The effects of the constituent volume fractions on the static and dynamic responses of the shell laminate are also elucidated. Copyright © 2002 John Wiley & Sons, Ltd.     

DESIGN OF STRUCTURE CONTROL SYSTEM USING BOUNDED LQG

An approach for designing a structure and its control system for vibration suppression is presented. The control system is based on the Linear Quadratic Gaussian (LQG) and is modified to allow bounds on the actuators forces to simulate real actuators. The simultaneous design of the structure and control problem is formulated as a nonlinear optimization problem. The system is designed for minimum weight where the weight includes both the weight of the structure and the weight of the actuators. The weight of an actuator is assumed to be proportional to the bound on the maximum force that it can supply. The design variables include the cross-sectional areas of the structural members and the bounds on the actuator forces. The constraints are imposed on the closed loop frequency distribution and the time to reduce the energy of vibration to a small portion of the initial vibrational energy of the system. The structure is analyzed using a finite element approach. For illustration of the design approach, a truss structure idealized with rod elements is used.     

应变反馈式压电陶瓷微位移驱动器的研制

介绍了采用应变片测量压电陶瓷微位移驱动器位移的原理和设计思想,介绍了实验装置的结构,给出了实验结果,证明将应变片直接粘贴在压电陶瓷基体表面测量其位移的方法是可行性的;通过对压电陶瓷滞回特性的测定,提出了建立压电陶瓷的控制模型的基本思路。     

A new numerical algorithm for sub‐optimal control of earthquake excited linear structures

Exact optimal classical closed–open‐loop control is not achievable for the buildings under seismic excitations since it requires the whole knowledge of earthquake in the control interval. In this study, a new numerical algorithm for the sub‐optimal solution of the optimal closed–open‐loop control is proposed based on the prediction of near‐future earthquake excitation using the Taylor series method and the Kalman filtering technique. It is shown numerically that how the solution is related to the predicted earthquake acceleration values. Simulation results show that the proposed numerical algorithm are better than the closed‐loop control and the instantaneous optimal control and proposed numerical solution will approach the exact optimal solution if the more distant future values of the earthquake excitation can be predicted more precisely. Effectiveness of the Kalman filtering technique is also confirmed by comparing the predicted and the observed time history of NS component of the 1940 El Centro earthquake. Copyright © 2001 John Wiley & Sons, Ltd.     

基于声辐射模态有源解耦控制的溢出机理研究

基于声辐射模态有源控制,通过作动器位置布置可以使得控制过程解耦,通过对比解耦和非解耦两种控制方式,并对其控制结果进行讨论。发现解耦控制所需控制能量较小并且相对控制稳定,比非解耦控制有明显优势。并且两者在低频段都能取得良好的控制效果,在频率较高时出现不同程度的控制溢出。在解耦控制的基础上,通过分析各阶声辐射模态辐射效率特点,作动器布置对称形式与声辐射模态对称形式的对应关系,揭示了溢出的机理     

基于声辐射模态的有源解耦控制的溢出问题及控制模型

基于声辐射模态的有源解耦控制理论,从声辐射模态的四种对称形式的角度出发,讨论各组压电作动器对声辐射模态（1～8阶）伴随系数的激励特性,分析有源解耦控制的溢出问题。本文结合四组压电作动器的控制特性,将前八阶声辐射模态辐射的声功率分成四组模态声功率,建立一种新的有源解耦控制模型,使得在中频范围内控制溢出得到有效的抑制。数值仿真结果表明,新的控制模型不仅保持了在低频范围内较好的控制效果,同时避免了在中频段的控制溢出现象,实现有源解耦控制在0～1000Hz频率范围内的预期效果。     

汽车磁流变半主动悬架系统的联合模态控制

提出了带有4个磁流变可控阻尼器的汽车半主动悬架的7＋k自由度动力学模型及其闭环控制方程,基于此模型,用2个可控阻尼器对系统的两个最大的模态实施独立模态控制,而另外两个可控阻尼器则对其余的模态实施耦合模态控制,并实时地根据传感器所获得的相关信息提取系统的模态坐标,实时跟踪最大模态,切换主控模态,并对其实施独立模态控制.这种独立/耦合模态联合控制方法,可以较好地发挥独立与耦合模态控制的优点而避免其缺点.仿真实例证实了独立/耦合模态联合控制具有比单独采用独立模态控制及耦合模态控制时更好的控制效果.     

基于遗传算法的不确定压电柔性结构H_2/H_∞混合振动控制

无穷范数和2-范数是优化控制理论的两个重要系统性能指标。前者考虑可能发生振动的最坏情况,过于保守;后者考虑系统的综合性能,未考虑共振情况;将两种指标结合起来将会同时兼顾鲁棒稳定性和系统时域性能。该文考虑不确定压电柔性结构模态参数的不确定性及模型误差,建立了结构模态空间的线性分式模型,给出了一种基于遗传算法的结构混合动态输出反馈振动控制器设计方法。首先通过线性矩阵不等式得到了多个无穷范数性能指标下的控制器,然后通过遗传算法对所得到的控制器进行了系统2-范数性能优化,设计了兼顾鲁棒性和系统时域性能要求的混合动态输出反馈控制器。     

Smart piezoelectric Fibre composites

Abstract

Piezoelectric materials are capable of actuation and sensing and have found uses in applications including ultrasonic transducers, hydrophones, micropositioning devices, accelerometers, and structural actuators. A composite configuration for structural actuation having significant advantages over conventional piezoelectric actuators has been conceived, and the recent development of piezoelectric ceramic fibres < 100 μ m in diameter has enabled this concept to be realised. It is envisaged that these composites will find uses in contour control, non-destructive testing, vibration suppression, and noise control. The possibility of computer control using closed loop systems has led to these composites emerging as potential 'smart' materials and structures. Since their conception, less than a decade ago, significant advances have been made in many areas concerned with composite performance, such as fibre and matrix technology and configuration optimisation. These advances are charted, the fibre, matrix, and electrode technologies are reviewed, and the manufacture, modelling, and applications of these new piezoelectric composites, known as active fibre composites, are discussed.     

《压电层合板的振动主动控制》

利用一阶剪切变形理论推导压电层合板的抗弯刚度,由Hamilton变分原理建立压电层合板的有限元模型,采用模态叠加方法对有限元模型降阶。在应变最大处配置制动器和传感器,并采用二次线性控制的独立模态空间控制法来进行板结构的主动控制。数值算例验证了这种力学建模方法和控制方法的有效性。