A sensorless drive system for controlling temperature-dependent hysteresis in piezoelectric actuators

A novel drive system is described which improves the operational characteristics of piezoelectric actuators. Electronic controls to increase the range of movement across a wide temperature range usually need a temperature sensor for maximum effect. This paper describes a novel system that uses the polarization characteristics of the piezoelectric ceramic to reverse polarize the ceramic without a temperature measurement. Significant improvements in the operating temperature range for devices such as locks or valves are achieved.     

压电倾斜镜迟滞非线性建模及逆补偿控制

自适应光学系统中的压电倾斜镜通常是用来实时校正大气湍流引起的波前畸变,但压电倾斜镜的响应都有较大的非线性迟滞效应,大大降低了倾斜镜的到位精度,并且影响系统稳定性,制约了倾斜校正系统的带宽,因此需要对迟滞现象进行建模,通过建立的模型进行补偿。本文通过引入迟滞算子,使用贝叶斯正则化训练算法训练BP神经网络来构建压电倾斜镜迟滞模型,以中国科学院光电技术研究所自主研制的压电倾斜镜为对象开展了实验研究。最后的实验结果表明,通过BP神经网络构建的压电倾斜镜迟滞模型具有较准确的辨识能力,其中,X方向的迟滞大小由6.5%降低到了1.3%,Y方向的迟滞大小由7.1%降低到了1.6%。     

压电宏纤维致动器的双极性非对称迟滞建模及补偿控制

提出了一种双极性非对称改进PI(Bipolar Asymmetric Improved PI,BAIPI)模型描述压电宏纤维(Marco Fiber Composite,MFC)的迟滞特性,BAIPI模型利用经典Prandtl-Ishlinskii(PI)迟滞模型Play算子加权叠加描述MFC的对称迟滞特性,然后叠加一系列不同权重、不同阈值的双边死区算子描述MFC的双极性非对称特性。实验辨识结果表明:BAIPI模型对MFC致动器的建模误差从PI迟滞模型的16.8%降为4.2%。在基于BAIPI逆模型的前馈补偿下,MFC致动的柔性梁构件跟踪等幅、变幅三角波轨迹的实测位移与期望跟踪位移基本重合,补偿后等幅三角波实测位移与理想位移之间的线性度为2.36%。因此,所提出BAIPI迟滞模型及补偿方法显著提高了MFC致动器的定位驱动和跟踪精度。     

振动控制中压电作动器非线性的补偿方法研究

在周期振动的自适应控制中,压电作动器的非线性特性会产生高次谐波,激发高阶模态振动。为抑制压电作动器的高次谐波激励,同时结合自适应振动控制的特点,提出一种新的作动器非线性补偿方法。该方法将作动器的非线性与结构的动态特性部分融合,用正交多项式从输入输出信号中拟合静态非线性及其逆变换,计算过程简单,数值稳定性高。在控制通道中,通过逆变换对控制信号进行预处理,使得补偿后的输入输出具有线性系统的特征,而输入输出之间的相位差完全由自适应算法进行补偿。实验结果表明,所给出的补偿方法能够抑制高次谐波,并改善了振动控制效果。     

Feedback control of vibrating plates using piezoelectric patch sensors and actuators

An analysis of the solutions for various feedback control laws applied to vibrating simply supported plates is evaluated. The control is carried out via a piezoelectric patch sensor and patch actuator. By considering an integral equation formulation, which is equivalent to the differential equation formulation, the analytical results are investigated. The conversion is accomplished by introducing an explicit Green’s function. The feedback controls implemented include displacement, velocity, and a combination of these. A numerical comparison of eigenvalues is presented to illustrate the efficacy of the method and to contrast the effects of the controls. The results presented in the study can be used for benchmarking solutions based in numerical or approximation approaches.     

Shape control of smart composite plate with non-rectangular piezoelectric actuators

Quasi-static shape control of a smart structure may be achieved through optimizing the applied electric fields, loci, shapes and sizes of piezoelectric actuators attached to the structure. In this paper, a finite element analysis (FEA) software has been developed for analyzing static deformation of smart composite plate structures with non-rectangular shaped PZT patches as actuators. The mechanical deformation of the smart composite plate is modeled using a 3rd order plate theory, while the electric field is simulated based on a layer-wise theory. The finite element formulation is verified by comparing with experimentally measured deformation. Numerical results are obtained for the optimum values of the electric field in the PZT actuators to achieve the desired shape using the linear least square (LLS) method. The numerical results demonstrate the influence of the shapes of actuators.     

压电作动器的迟滞非线性建模和实时补偿控制仿真

压电作动器的迟滞非线性不同程度的影响了作动器的性能,降低了系统的稳定性,甚至使得系统不稳定,尤其在振动主动控制应用中,要求系统具有极强的实时性,否则由于相位滞后控制效果将会受到严重影响.在研究了各种迟滞非线性模型和补偿算法的基础上,采用PI迟滞算子对压电作动器建立一个纯现象的模型来准确描述其迟滞现象,参数的线性不等式约束保证了求解的唯一性和模型的可逆性.在此基础上利用PI逆模型设计补偿器来补偿迟滞非线性.仿真结果证明了控制算法的正确性和有效性,并有效抑制了迟滞的影响,保证了理想的跟踪精度.     

Numerical modelling of piezoelectric actuators exposed to hydrogen

Modern fuel injectors have been developed based on piezoelectric stack actuators. Performance and durability of actuators in a hydrogen environment are important considerations in the development of hydrogen injectors. 2D plane stress and 3D models for analysis of coupled diffusion and thermo-electromechanical response of actuators are presented. Chemical potential, electric field and temperature gradients are taken as driving forces for hydrogen transport. The explicit Euler finite difference method is used to solve the nonlinear diffusion governing equation. The finite element method is used for time-dependent analysis of fully coupled mechanical, electric and thermal fields. The diffusion process and thermo-electromechanical deformations are coupled through the dependence of piezoelectric properties on hydrogen concentration. Experimental results for the piezoelectric coefficient d ₃₃ of PZT ceramics exposed to different hydrogen concentrations are used. A comparison of a fully coupled 2D model with 2D and 3D models with reduced coupling is made to examine the significance of coupling and computational efficiency. Selected numerical results are presented for time histories of hydrogen concentration, temperature and stroke of an idealized actuator unit cell to obtain a preliminary understanding of the performance of actuators exposed to hydrogen.     

Finite element analysis on deflection control of plates with piezoelectric actuators

A finite element model for the deflection control of plates with piezoelectric actuators is presented. This model contains an actuator element, an adhesive interface element and an eight-node isoparametric plate element. The actuator element developed here is based on first-order shear deformation theory. An analytical solution is also derived in comparison with results using the finite element model. The analyses articulate separate response of the plate; actuators and the adhesive give the flexible meshing advantage of solving the- smart structure problem with any type of boundary conditions and geometry configuration.     

A new method for finding the first‐ and second‐order eigenderivatives of asymmetric non‐conservative systems with application to an FGM plate actively controlled by piezoelectric sensor/actuators

In this paper, a new method for computing eigenvalue and eigenvector derivatives of asymmetric non‐conservative systems with distinct eigenvalues is presented. Several approaches have been proposed for eigenderivative analysis of systems with asymmetric and non‐positive‐definite mass, damping and stiffness matrices. The proposed formulation that is developed by combining the modal and algebraic methods neither have the complications of modal methods in calculating the complex left and right eigenvector derivatives nor suffer from numerical instability problems usually associated with algebraic methods. The method is applied to a functionally graded material (FGM) plate actively controlled by piezoelectric sensor/actuators. In this system, the feedback signal applied to each actuator patch is implemented as a function of the electric potential in its corresponding sensor patch. The use of this closed‐loop controlling system leads to a non‐self‐adjoint system with complex eigenvalues and eigenvectors. A finite element model is developed for static and dynamic analysis of closed‐loop controlled FGM plate. The first‐ and second‐order approximations of Taylor expansion are used to estimate the corresponding changes in the plate modal properties due to change in design parameters (the displacement feedback gains and the piezoelectric layer thickness in each S/A pair). Copyright © 2008 John Wiley & Sons, Ltd.     

Comparison of strain gage and interferometric detection for measurement and control of piezoelectric actuators

The capability of controllable and repeatable positioning in the subnanometer range is fundamental not only for scanning probe microscope applications, but also for nanotechnology in general. Up to now, piezoceramic actuators have been used for this purpose. However, these actuators are far from being ideal transducers. For precise metrological applications, as well as for general use in scanning probe microscopy, some method has to be implemented to correct creep and nonlinearity of piezoceramic materials. In the present study, two different position measuring systems have been implemented—one based on strain gage detection and the other on interferometry. The corresponding results are presented and the performance of both setups compared.     

Finite element modelling and vibration control study of active plate with debonded piezoelectric actuators

A finite element model for a piezoelectric plate with edge debonded actuators is presented. This model is employed to investigate the effect of edge debonding on actuation authority, natural frequencies and vibration control performance. The regions of the plate with the piezoelectric patches are modelled such that each layer undergoes rotation due to shear deformation independently. The necessary constraints for continuity of displacements at the interfaces of the layers are imposed. The plate with edge debonded actuators is idealized by dividing it into debonded regions and healthy regions. A finite element procedure for imposing the constraints regarding continuity of displacements at the interfaces of the adjacent regions is developed and is implemented using MATLAB. Experiments are conducted for finding the actuation authority and natural frequencies of the plate with debonded actuators. It has been found that the developed model has predicted the mechanics of actuator debonding properly. The investigations have revealed the fact that the edge debonding of actuators will result in considerable degradation in actuation authority and vibration control performance.     

Solid freeform fabrication of piezoelectric sensors and actuators

The last two decades have witnessed the proliferation piezoelectric composite transducers for an array of sensor and actuator applications. In this article, a concise summary of the major methods used in composite making, with special emphasis on Solid Freeform Fabrication (SFF), is provided. Fused Deposition of Ceramics (FDC) and Sanders Prototyping (SP) are two SFF techniques that have been utilized to make a variety of novel piezocomposites with connectivity patterns including (1-3), (3-2), (3-1), (2-2) and (3-3). The FDC technique has also been used to prototype a number of actuators such as tube arrays, spiral, oval, telescoping, and monomorph multi-material bending actuators. It has been demonstrated that SFF technology is a viable option for fabricating piezocomposite sensors and actuators with intricate geometry, unorthodox internal architecture, and complex symmetry. The salient aspects of processing of such composite sensors and actuators are summarized, and structure-processing-property relations are elaborated on.     

A new method of sulfur vapor pressure control and its application to the V-S system

A new apparatus for obtaining partial pressure of sulfur was devised by using liquid sulfur and carrier gas of nitrogen. This successfully works in the range of ～10^?4 to ～1 atm of Ps₂ at any temperature higher than about 400°C up to about 1000°C. As an application of it, the equilibrium study of V-S system was done at 800°C. Two phases V₃S₄ and V₅S₈, each having homogeneity range, were found while no existence of the V₂S₃ phase could be detected thermodynamically and X-ray crystallogrpahically at this temperature. The standard free energy of following reaction, $\text{VS}{}_{\mathrm{<mtext>4</mtext><mtext>3</mtext>}}\text{+}\text{2}\text{15}$$\text{S}{}_2\text{=}\text{VS}\text{8}\text{5}$, was calculated by considering the transition-Ps₂ and the activities and · ΔG° (1073K) = ?1150 cal·mole^?1was obtained with an estimated uncertainty of ± 100 cal to the above reaction.     

板振动的无需次级通道建模的分散式前馈控制方法研究

本文针对板的振动,提出了一种无需次级通道建模的分散式前馈控制方法。该前馈控制方法不需要结构的物理信息,并且能够控制板在非共振频率处的线谱振动。采用压电片和加速度计分别作为执行和传感元件,建立了简支板振动主动控制的理论模型和实验系统。提出了分散式前馈控制策略,并分析了无需次级通道建模的分散式前馈控制算法的稳定性。提出了一种内模滤波器将加速度信号转变为速度信号,并补偿抗混叠滤波器和平滑滤波器的频率响应,使执行器和传感器保持同位配置。通过仿真和实验验证了该算法的有效性。     

Modelling and analysis of piezoelectric actuators in anisotropic structures

Summary In this paper, we examine the coupled electromechanical behaviour of a piezoceramic actuator bonded to a finite elastic medium under inplane mechanical and electric loading. The purpose of the current work is to study the suitability of using a simple actuator model to simulate the load transfer between actuators and the host medium. The actuator is characterized by an electroelastic line model with the poling direction being perpendicular to its length. The solution of this electromechanically couple problem is provided by solving singular integral equations in terms of an interfacial shear stress and conducting finite element analysis. The results show that the transfer of the actuation energy between the actuator and the host structure can be effectively simulated using the developed theoretical model. Typical examples are provided to show the effects of the geometry, the material combination and anisotropy upon the load transfer. The study is further extended to treat the interfacial debonding between the actuator and the host material.     

Electromechanical coupling and output efficiency of piezoelectric bending actuators

Electromechanical coupling mechanisms in piezoelectric bending actuators are discussed in this paper based on the constitutive equations of cantilever bimorph and unimorph actuators. Three actuator characteristic parameters, (e.g., electromechanical coupling coefficient, maximum energy transmission coefficient, and maximum mechanical output energy) are discussed for cantilever bimorph and unimorph actuators. In the case of the bimorph actuator, if the effect of the bonding layer is negligible, these parameters are directly related to the transverse coupling factor lest. In the case of the unimorph actuator, these parameters also depend on the Young's modulus and the thickness of the elastic layer. Maximum values for these parameters can be obtained by choosing proper thickness ratio and Young's modulus ratio of elastic and piezoelectric layers. Calculation results on four unimorph actuators indicate that the use of stiffer elastic material is preferred to increase electromechanical coupling and output mechanical energy in unimorph actuators.     

Integrated optimization of structure and control for piezoelectric intelligent trusses with uncertain placement of actuators and sensors

The finite element modeling of truss structures with piezoelectric members is presented. Based on the approach of independent modal space control, the controllability and observability indices of the system related to the positions of actuators/sensors are demonstrated. Consequently, the effective damping response time is evaluated. The object of the optimization model is to minimize a specified performance index of the intelligent truss subjected to constraints on the natural frequency and the amplitude of displacement response as well as the applied voltages under a given disturbance. Structural sizing variables, control parameters and actuator/sensor placements are treated as the independent design variables. Coding, the calculation of fitness and the optimization procedure of Genetic Algorithms are discussed so as to solve the integrated optimization with two different types of design variable space: discrete and continuous. Numerical examples are presented to show the effectiveness and usefulness of integrated optimization of structure and control for piezoelectric intelligent trusses.The authors would like to thank for the support by Natural Science Foundation of China under grant 10072050 and the Doctorate Creation Foundation of Northwestern Polytechnical University under grant 200236.     

Optimal location of piezoelectric actuators for active vibration control of thin axially functionally graded beams

Up to now, optimal location for active control studies concern principally multilayers or homogeneous structures. In the case of functionally graded materials, very few papers exist and they only concern cross section variations. In this way, this paper deals with the optimization of piezoelectric actuators locations on axially functionally graded beams for active vibration control. For this kind of structures, the free vibration problem is more complicated as the governing equations have variable coefficients. Here, the eigenproblem is solved using Fredholm integral equations. The optimal locations of actuators are determined using an optimization criterion, ensuring good controllability of each eigenmode of the structure. The linear quadratic regulator, including a state observer, is used for active control simulations. Two numerical examples are presented for two kinds of boundary conditions.     

Finite element piezothermoelasticity analysis and the active control of FGM plates with integrated piezoelectric sensors and actuators

 An efficient finite element model is presented for the static and dynamic piezothermoelastic analysis and control of FGM plates under temperature gradient environments using integrated piezoelectric sensor/actuator layers. The properties of an FGM plate are functionally graded in the thickness direction according to a volume fraction power law distribution. A constant displacement-cum-velocity feedback control algorithm that couples the direct and inverse piezoelectric effects is applied to provide active feedback control of the integrated FGM plate in a closed loop system. Numerical results for the static and dynamic control are presented for the FGM plate, which consists of zirconia and aluminum. The effects of the constituent volume fractions and the influence of feedback control gain on the static and dynamic responses of the FGM plates are examined. Received: 13 March 2002 / Accepted: 5 March 2003 The work described in this paper was supported by a grant awarded by the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. CityU 1024/01E).