Design and fabrication of a high performance multilayer piezoelectric actuator with bending deformation

A new bending mode multimorph actuator was designed and fabricated successfully by a multiple screen printing process. Unlike the conventional bimorph actuator in which the bend occurs in the thickness direction, the bend in the multimorph actuator occurs in the widthwise direction because of synchronistical deformation of each single monolithic layer in the multilayer structure. The theoretical analysis and experimental measurements were conducted to study the performance of this type of actuator, and a comparison was made with the conventional bimorph actuator. Larger displacement, higher resonance frequency, and much larger blocking force could be achieved with the multimorph actuator than with a bimorph actuator of similar dimensions. The multimorph actuator presented in this paper provides a valuable alternative for actuator applications beyond those available with the popular bimorph and longitudinal multilayer actuators.     

A multilayer inplane bending piezoelectric actuator for dual-stage head-positioning control system

A novel multilayer in-plane bending piezoelectric actuator, called a multilayer split-morph, was designed and fabricated by thick-film screen-printing technology for a dual-stage head-positioning actuator system in a hard disk drive. The design, operation and theoretical principles have been described. The electromechanical performance of the fabricated actuators has been evaluated. The actuation stroke of the actuator is in inverse proportion to the thickness of the piezoelectric layer. The highest displacement/voltage sensitivity of 0.154µmV^-1 is achieved in a trapezoidal multilayer split-morph with a thickness of 35 m in each piezoelectric layer. The corresponding fundamental resonance frequency of the sway mode is high at 47 kHz in the trapezoid actuator with dimensions of 10.14 mm length, 3.08 mm and 1.54 mm widths of the two parallel sides of the trapezoid. The multilayer split-morph was designed to integrate directly onto a modified suspension load beam. With the combined attractive performances indicated above, the batch fabricated multilayer split-morph can provide a low-cost but promising solution for achieving very high track densities in a hard disk drive by implementing a high performance dual-stage head-positioning actuator system.     

Longitudinal-bending mode micromotor using multilayer piezoelectric actuator

Longitudinal-bending mode ultrasonic motors with a diameter of 3 mm were fabricated using stacked multilayer piezoelectric actuators, which were self-developed from hard lead zirconate titanate (PZT) ceramic. A bending vibration was converted from a longitudinal vibration with a longitudinal-bending coupler. The motors could be bidirectionally operated by changing driving frequency. Their starting and braking torque were analyzed based on the transient velocity response. With a load of moment of inertia 2.5 x 10(-7) kgm2, the motor showed a maximum starting torque of 127.5 microNm. The braking torque proved to be a constant independent on the motor's driving conditions and was roughly equivalent to the maximum starting torque achievable with our micromotors.     

一种弯曲型压电堆作动器的设计及在振动控制中的应用

提出了一种弯曲型压电堆作动器并将其应用于悬臂梁主动振动控制中。新型作动器由一个压电堆和一个 型金属底座和一个预压螺钉组成。该作动器的通过底座对压电堆纵向变形的约束而使底座弯曲变形产生作动弯矩。推导了新型作动器的输出作动弯矩计算公式,并将其应用于悬臂梁振动控制中,采用热弹比拟方法结合状态空间理论建立了带新型压电作动器的悬臂梁振动控制系统状态空间方程。分别应用正位置反馈（Positive position feedback,PPF）和神经网络预测（Neural network predictive,NNP）控制方法设计了主动振动控制系统。闭环仿真结果表明,采用本文提出的新型压电堆作动器控制悬臂梁的一弯模态位移响应,应用PPF控制其幅值可降低57%,应用NNP控制其幅值可降低92%。     

Tracking control of a multilayer piezoelectric actuator using a fiber bragg grating displacement sensor system

This paper provides a fiber Bragg grating (FBG) sensor system which can measure the point-wise, out-of-plane displacement to examine the position-tracking control problem of a multilayer piezoelectric actuator (MPA). An FBG filter-based wavelength-optical intensity modulation technique is used in this study. A nominal system model is identified experimentally from the responses excited by random signals measured by an FBG displacement sensor that are simultaneously compared with those obtained from a laser Doppler vibrometer. To further investigate the sensing ability of the proposed system in a feedback control problem, control strategies including robust Hα control, proportional-integralderivative control, and pseudoderivative feedback control are implemented. The characteristics of the step responses for each controller are examined. The experimental results show that the proposed sensor system is capable of performing the system identification and can serve as a feedback control sensor which has a displacement sensitivity of 5 mV/nm.     

Effect of electric cyclic loading on fatigue cracking of a bending piezoelectric hybrid composite actuator

Fatigue damage development in bending piezoelectric hybrid composite actuators with different lay-up configurations under electrical loading cycles is addressed in this work with the aid of an acoustic emission (AE) technique. Electric cyclic fatigue tests have been performed up to 10⁷ cycles on the fabricated bending piezoelectric hybrid composite actuators. The applied electric loading range is from ?150 voltage to +150 voltage. To confirm the fatigue damage onset and its pathway, the source location and distributions of the AE behavior over the fatigue range are analyzed. In conclusion, electric cyclic loading leads to piezoelectric fatigue damage such as trans- and intergranular micro-damage and long path main cracking on the surface of the PZT ceramic layer, thereby degrading the displacement performance. However, this fatigue damage and cracking do not result in final failure of the bending piezoelectric hybrid composite actuator loaded up to 10⁷ cycles. In particular, investigation of the AE behavior and the linear AE source location reveals that the onset time of the fatigue damage varies considerably depending on the existence of a GFRP protecting bottom layer.     

Finite element analysis of a multilayer piezoelectric actuator taking into account the ferroelectric and ferroelastic behaviors

Ferroelasticity and ferroelectricity are the non-linear behaviors exhibited by piezoceramics, especially in the case of high electric field or stress. Many studies have focused on the role of ferroelastic and ferroelectric switching in fracture of actuators. However, engineering reliability analyzes are carried out with tools like finite element software that do not take into account these non-linear phenomena. To overcome such a problem, a simplified phenomenological constitutive law describing the non-linear behavior of piezoceramics has been developed and implemented in the commercial software ABAQUS. This finite element tool is used to study the effects of applied voltage on the electroelastic field concentrations ahead of electrodes in a multilayer piezoelectric actuator. The study lies on the experimental observations made by Shindo et al. [Y. Shindo, M. Yoshida, F. Narita, K. Horiguchi, Electroelastic field concentrations ahead of electrodes in multilayer piezoelectric actuators: experiment and finite element simulation, J. Mech. Phys. Solids 52 (2004) 1109–1124]. Electroelastic analysis on piezoceramics with surface electrode showed that high values of stress and electric displacement arose in the neighborhood of the electrode tip. Thus, the strain, stress and electric displacement concentrations were calculated and the numerical results showed that ferroelectric switching arose in the area of the electrode tip, causing a change in remnant polarization and remnant strain.     

Kinked crack in a bending trapezoidal plate

The interaction problem of a kinked crack and the edges of a bending trapezoidal plate which takes the effects of transverse shear deformation into account is presented. The research method is based upon the complex potential technique of Muskhelishvili using conformal mapping. Furthermore, for the analysis of the moment intensities at the tips of the kinked crack, the concept of dislocation distribution is applied. The integral equations for the stress disturbance problem along the line that is the presumed location of the kinked crack are then obtained as a system of singular integral equations with simple Cauchy kernels. As a consequence, the variation of moment intensity factors at the crack-tips is also illustrated.     

Microdisplacement characteristics and microstructures of functionally graded piezoelectric ceramic actuator

In this work, we report a functionally gradient piezoelectric ceramic actuator with sandwiched structure prepared by the powder metallurgical method. The functional gradients of piezoelectric activity and dielectric activity vary inversely across the thickness of the actuator. Such functional gradients are obtained by interdiffusion reaction between a high piezoelectric composition [Pb(Zr,Ti)O₃/PZT] and a high dielectric composition (PbNi_1/3Nb_2/3O₃/PNN). The bending displacement at the free end of the PNN/PZT functionally graded piezoelectric ceramic actuator was approximately 20 m when 1.4-kV/mm electric field was applied. The grain morphology and compositional distribution across the actuator section and the microstructures of the sandwiched layer were investigated by scanned electron microscopy equipped with energy-dispersive spectroscopy, transmission electron microscopy, and selected area electron diffraction patterns, respectively.     

弯振复合型超声驱动器振动特性研究

为了避免模态复合型超声驱动器中普遍存在的频率简并问题,作者在前期研究中提出了一种新型的弯振复合型超声驱动器。该驱动器采用压电金属复合梁两个正交弯振模态的复合在两个驱动足处激励出椭圆轨迹振动。本文对该驱动器的振动特性进行深入研究,旨在获得驱动区域质点的真实运动轨迹。首先,建立了矩形截面梁在弯振复合模态下末端区域质点振动轨迹的数学模型;然后,借助有限元瞬态分析,对驱动足振动轨迹进行仿真,实现对所建立振动轨迹数学模型的验证。振动轨迹方程和仿真结果均表明：两个驱动足表面质点振动轨迹均为三维的椭圆,垂直于驱动器轴线的平面内的椭圆振动更适合用于致动输出。最后,分析了该驱动器存在的不足之处,提出了一种改进方案,采用对称设置压电陶瓷片实现两个驱动足振动特性的一致;通过瞬态分析在两个驱动足处得到了一致的振动轨迹,改进的样机实现了输出特性的显著提高。     

A hysteresis model for a stacked-type piezoelectric actuator

The hysteresis nonlinearity in piezoelectric materials brings difficulties in controlling the systems. In order to mitigate the effect of hysteresis, such nonlinearity needs to be characterized and modeled under different load circumstances. For this purpose, the actuator is modeled in terms of a mass-spring-damper system utilizing the stop operator as one of the operators of the Prandtl-Ishlinskii (PI) model. Merging the structural model with the nonlinear hysteresis model, we observe that the results demonstrate better correspondence to the measured output compared to that of the classical PI model for a wide range of working conditions, i.e., different input frequency and amplitude.     

Performance improvement of a piezoelectric bimorph actuator by tailoring geometry

This article illustrates performance improvement of a piezo-bimorph actuator by tailoring its geometry. We have analytically presented that a piezo-bimorph actuator with a tapered surface provides superior performance for out-of-plane bending compared to a rectangular surface while having equal mass and equal primary capacitance. Equal capacitance ensures equal input electrical energy and bandwidth for both the cases below its first resonant frequency. We have analytically derived performance measuring attributes of such an actuator considering high electric field, and shown the performance improvement quantitatively. We have also presented finite element solutions to compare with the analytical solutions. Some results are validated with the earlier published experimental results.     

Buckling analysis of trapezoidal composite sandwich plate subjected to in-plane compression

The results of the stability analysis of simply supported layered isosceles trapezoidal plate subjected to axial in-plane compression are presented. The layup configuration is confined to symmetric laminates. The solution has been obtained by means of the Galerkin orthogonalisation method combined with the proposed method of the coordinate system transformation. The results of the analytical solution are compared with the verifying FEM calculation. The computed results in the form of graphs of the buckling force as a function of material and geometrical parameters of the panel are included.     

Vibration analysis of cubic rotary-linear piezoelectric actuator

Cubic design of a stator in a rotary-linear piezoelectric actuator is sophisticated and interesting, but the vibration theory of the cubic stator remains unclear when using the finite element method (FEM). In this paper, we analyze the vibration behavior of the cubic stator by applying the energy method, which distinguishes the component of mechanical energy. By changing the design of the stator (especially the length in the direction of the through-hole axis), we clarify how the vibration modes are in accordance at one equal frequency in cubic shape. The behavior of the vibration modes is discussed using conventional vibration theory of a beam and a plate.     

High-displacement piezoelectric actuator utilizing a meander-line geometry II. Theory

For pt.I see ibid., vol.38, no.5, p.454-60 (1991). A simple electromechanical model of the meander-line actuator is developed. The model consists of a voltage-actuated force source, which is the result of the piezoelectric properties of the bars that make up the actuator, in parallel mechanically with a stiff spring that models the compression-expansion response of the piezoelectric bars. This parallel combination is in series mechanically with a second spring. This series connection is subjected to large bending moments that cause the stiffness of this second spring to be much less than the stiffness of the spring in parallel with the force source. The addition of stiffeners to the actuator can significantly reduce these bending moments and thus increase the stiffness of this second spring. As a result, the force generation capability of the actuator is significantly increased without affecting its displacement capability.     

The dynamic behavior of a surface-bonded piezoelectric actuator with a bonding layer

The performance of smart structures depends on the dynamic electromechanical behavior of piezoelectric actuators and the bonding condition along the interface, which connects the actuators and the host structures. This paper provides a theoretical study of the influence of material parameters of the bonding layer on the coupled electromechanical characteristics of piezoelectric actuators, which are subjected to high frequency electric loads. A one-dimensional actuator model with a bonding layer, which undergoes a shear deformation, is proposed. Analytical solutions based on the integral equation method are provided. Detailed numerical simulation is conducted to evaluate the effect of the bonding layer under different loading frequencies. The results indicate that the properties of the bonding layer, the loading frequency, the material combination and the geometry of the actuator have a significant effect on the load transfer between the actuator and the host medium.     

Performance evaluation of a valveless micropump driven by a ring-type piezoelectric actuator

Presented in this paper is the study of the performance evaluation of a valveless micropump driven by a ring-type piezoelectric actuator. The application of this micropump is to circulate fuel inside a miniaturized direct methanol fuel cell (DMFC) power system. A theoretical model based on the theory of plates and shells is established to estimate the deflection and the volume change of this micropump without liquid loading. Both finite-element method (FEM) and experimental method are applied to verify this model. Using this model, the optimal design parameters such as the dimensions and the mechanical properties of the micropump can be obtained. Furthermore, various system parameters that will affect the performance of the micropump system with liquid loading are identified and analyzed experimentally. It is expected that this study will provide some vital information for many micropump applications such as fuel delivery in fuel cells, ink jet printers, and biofluidics.     

Investigation on the electrophoretic deposition of a FGM piezoelectric monomorph actuator

In this paper, a FGM monomorph actuator was fabricated and its properties were also investigated. The procedure of fabricating such an actuator using electrophoretic deposition (EPD) was first established. The important processing parameters, such as zeta potential, were determined. The phase composition and microstructure of the deposits were examined using XRD and SEM. Smooth gradient microstructure was observed over the cross section and no significant defects and sharp interface was observed. The displacement of a monomorph, with dimension of 15.0 mm in length, 3.0 mm in width and 0.3 mm in thickness, was measured to be 4.16 m under 100 V with low loss using photonic sensor. Both the microstructure and the electromechanical properties of the FGM monomorph actuator have indicated that EPD technique is a promising fabrication method for high performance components.     

Finite element bending analysis of multilayer plates

The development of a general quadratic multilayer plate element is presented for the analysis of arbitrarily layered curved plates. In the formulation, each layer of the multilayer plate can have different orthotropic properties and can deform locally. Examples of bending problems are presented which demonstrate the applicability of the formulation.