Multilayer Piezoelectric Actuator Research Articles

A comparative study of piezoelectric unimorph and multilayer actuators as stiffness sensors via contact resonance

Piezoelectric bar-shaped resonators were proposed to act as hardness sensors in the 1960s and stiffness sensors in the 1990s based on the contact impedance method. In this work, we point out that both multilayer and unimorph (or bimorph) piezoelectric actuators could act as stiffness/modulus sensors based on the principle of mechanical contact resonance. First, the practical design and the performance of a piezoelectric unimorph actuator–based stiffness sensor were presented. Then the working principle of piezoelectric multilayer actuator–based stiffness sensors was given and verified by numerical investigation. It was found that for these two types of resonance-based sensors, the shift of the resonance frequency due to contact is always positive, which is different from that of the contact impedance method. Further comparative sensitivity study indicated that the unimorph actuator–based stiffness sensor is very suitable for measurement on soft materials, whereas the multilayer actuator–based sensor is more suitable for hard materials. Both multilayer (or bar-shaped) and unimorph (bimorph) piezoelectric actuators can be used as stiffness/modulus sensors based on the mechanical contact resonance.

Displacement characteristics of a piezoactuator-based prototype microactuator with a hydraulic displacement amplification system

In this study, a new piezoactuator-based prototype microactuator is proposed with a hydraulic displacement amplification system. A piezoactuator is used to deflect a diaphragm which displaces a certain volume of hydraulic fluid into a smaller-diameter piston chamber, thereby amplifying the displacement at the other end of the piston. An electro-mechanical model is implemented to estimate the displacement of a multilayer piezoelectric actuator for the applied input voltage considering the hysteresis behavior. The displacement characteristics of the proposed microactuator are studied for triangular actuation voltage signal. Results of the experiments and simulation of the displacement behavior of the stacked piezoactuator and the amplified displacement of the prototype actuator were compared. Experimental results suggest that the mathematical model developed for the new piezoactuator-based prototype actuator is capable of estimating its displacement behavior accurately, within an error of 1.2%.

Formulation of a simple distributed-parameter model of multilayer piezoelectric actuators

A multilayer piezoelectric actuator is a promising linear vibrator. In this article, a simple distributed-parameter analytical model of piezoelectric actuator, which can model vibration characteristics of piezoelectric actuator–based applications, is formulated. Based on the physical analysis of piezoelectric actuator, a simplification is proposed, justified and applied to fundamentals of thickness-extension-mode piezoelectricity. This simplification subtly enables piezoelectric actuator to be effectively modelled as a whole and allows for a formulation of a simple analytical model. Compared with other modelling methods in the literature, the proposed model with a small number of easily accessible parameters is easy to handle and extend with little compromised accuracy. The effectiveness of the proposed model has been validated by a three-dimensional finite element analysis model of piezoelectric actuator developed in commercial software ANSYS.

Feasibility Study of a Hybrid Ice Protection System

A key design factor impacting the use of electrical power to drive aircraft systems and subsystems is energy efficiency. With the design of an all-electric, hybrid ice protection system, energy consumption can be reduced to a large extent. The hybridization is achieved through an intentional partitioning of the ice at the stagnation line by melting via surface heating and ice shedding in the unheated regions of the airfoil surface via an electromechanical deicing system based on piezoelectric multilayer actuators. To further reduce energy consumption, the adhesion forces between the ice and the airfoil surface can be reduced using an ultrasmooth, nanostructured surface with water- and ice-repellent properties that encourages ice shedding. Experimental investigations, performed in a laboratory-scale icing wind tunnel for a small-scale configuration, reveal that the hybrid approach for ice protection reliably sheds the ice accreted on the airfoil surface. Compared with an all-thermoelectric system for ice protection investigated in the same icing wind tunnel facility using identical test conditions, the hybrid approach was demonstrated to reduce power consumption up to 91%. Beyond the laboratory tests, numerical simulations of the hybrid strategy analogous to the one used for the experiments are performed. The time history of the residual ice shapes aft of the heated region is simulated using the ice accretion prediction software LEWICE2D for a wet-running anti-icing subsystem. Finite element analyses of the effects of the piezoelectric actuators are then performed using Abaqus to investigate the ice-shedding capability in the unheated regions of the airfoil surface. The numerical results show that the variation in the different ice shapes affects the stiffness of the model. It becomes obvious that the critical threshold for ice shedding, that is, the stiffness that determines whether residual ice delaminates from the airfoil surface, is affected to a minor extent by the interfacial area and predominantly by the thickness of the ice layer. Further, the simulation results correlate well with experimental results obtained in the icing wind tunnel. It can be concluded that reliable operation of the hybrid system for ice shedding can be guaranteed when using a harmonic sweep excitation able to excite the structure at its resonance.

Self-sensing control of piezoelectric positioning stage by detecting permittivity

Piezoelectric displacement contains hysteresis and creep properties. Therefore, a displacement sensor is indispensable in precise positioning devices; however, the additional space and cost are problems. On the other hand, self-sensing methods that utilize the piezoelectric actuator itself as the displacement sensor have been proposed. With these self-sensing methods, precise positioning becomes possible without an additional displacement sensor. We developed a self-sensing method utilizing the non-hysteresis relationship between the permittivity change and the piezoelectric displacement. Furthermore, a differential current measurement method using two piezoelectric elements with a bimorph actuator could improve the positioning accuracy. In this study, we examine the control of a positioning stage using two multilayered piezoelectric actuators by applying the differential current measurement method for self-sensing control. The results indicate that the differential current measurement method is effective for precise positioning control. The positioning errors due to hysteresis decreased from 0.8μm to 0.1μm for a 10μm displacement range. In addition, permittivity feedback control could compensate for the creep property.

Shear Wave Wavefront Mapping Using Ultrasound Color Flow Imaging.

A wavefront reconstruction method for a continuous shear wave is proposed. The method uses ultrasound color flow imaging (CFI) to detect the shear wave's wavefront. When the shear wave vibration frequency satisfies the required frequency condition and the displacement amplitude satisfies the displacement amplitude condition, zero and maximum flow velocities appear at the shear wave vibration phases of zero and π rad, respectively. These specific flow velocities produce the shear wave's wavefront map in CFI. An important feature of this method is that the shear wave propagation is observed in real time without addition of extra functions to the ultrasound imaging system. The experiments are performed using a 6.5 MHz CFI system. The shear wave is excited by a multilayer piezoelectric actuator. In a phantom experiment, the shear wave velocities estimated using the proposed method and those estimated using a system based on displacement measurement show good agreement.

MoP-19 FABRICATION OF PIEZOELECTRIC MULTILAYER THIN-FILM ACTUATORS

We proposed a novel fabrication method of multilayer thin-film piezoelectric actuators composed of 500 nm-thick Pb(Zr,Ti)O_3 (PZT) layers by a single sputtering deposition process. This method enables the fabrication of multilayered piezoelectric thin films with separated intermediate electrodes on SOI substrates without photolithography. We successfully improved, for the first time, the effective transverse piezoelectric properties utilizing the multilayer thin-film structure with increasing a number of PZT layers. We also confirmed that the multilayer thin-film structure enhanced the dielectric properties with increasing a number of PZT layers.

Reliability analysis of ultrasonic power transducers

Ultrasonic power transducers are commonly used in applications like cleaning, plastics welding or sonochemistry. Typically, the design of transducers for new applications is a tedious iterative process of design, prototype construction and tests. The transducers must fulfill the needs and restrictions of the specific application, as otherwise the transducer might be oversized or fail during operation. While reliability has been studied worldwide intensively in the case of piezoelectric multilayer actuators—driven by car industry which now uses such actuators in their fuel injection systems—nearly no literature is available for the reliability of ultrasonic power transducers. As well, manufacturers seldom present data about aging or lifetime of their components. To enhance the knowledge about typical failure mechanisms of ultrasonic power transducers under different load conditions, our contribution—as a first step—reports on a theoretical study on the reliability of common known ultrasonic transducers and gives some examples of typical failures and their influence on the characteristics of the transducer.

Determination of the True Operational Range of a Piezoelectric Actuator

Piezoelectric multilayer actuators are technologically important devices used in numerous positioning and force generation applications. During operation, the actuator displacement and force are nonlinearly coupled to the applied electric field, which is often ignored during material characterization. In this study, a novel experimental arrangement is presented that acts like a virtual linear spring, allowing for characterization of the full operational range as a function of applied electric field as well as the true blocking force and impedance matching system stiffness. The macroscopic measurements are contrasted to previous experimental techniques, providing insight into the effect of path dependence on the blocking force.

Electromechanical response of multilayer piezoelectric actuators for fuel injectors at high temperatures

This paper studies the electromechanical response of multilayer piezoelectric actuators from room to high temperatures for fuel injector applications. A phenomenological model of depolarization at high temperatures was proposed, and the temperature dependent piezoelectric coefficients were obtained. The nonlinear electromechanical fields of the multilayer piezoelectric actuators due to the depolarization at high temperatures were then calculated by the finite element method. In addition, experimental results on the electric field induced strain at high temperatures were presented to validate the predictions.

Development of a Compact Deformable Mirror Using Push-Pull Actuators

A small deformable mirror which realizes concave shape as well as convex shape has been developed. In addition, this deformable mirror was developed to realize long term stability. For this purpose, a new push-pull actuator using two multilayered piezoelectric actuators aligned inline was designed. In this process, a practical method for simulating the property of piezoelectric actuator in the finite element method was proposed. From the experimental results, it was confirmed that newly developed deformable mirror has the ability to make complex profiles. Furthermore, efficiency of proposed simulation method was also confirmed.

Controlled ultrasonic micro-dissection of thin tissue sections

In order to obtain sufficient quantities of pure populations of cells or a single cell from surrounding tissue for analytical investigation, we have developed an ultrasonic microdissection system. The system utilizes a vision-based method for detecting the contact between the microdissection needle tip and a target surface. A multilayer stack piezoelectric actuator is employed to generate ultrasonic vibrations for histological isolation. Automated micro-dissection is also realized using visual feedback and vision-based control. Experimental results on tumor tissue sections show that the system has a high dissection accuracy and efficiency and is able to realize dissecting arbitrary shapes in specified locations on a tissue sample. Furthermore, effects in variations of vibration amplitude and frequency of ultrasonic micro-dissection as well as needle insertion depths on micro-dissection accuracy and speed were evaluated.

Design of Star-Shaped Flextensional Stator for Ultrasonic Motor

When a driving voltage opposite to the piezoelectric polarity is applied on the flextensional stator, it will generate the normal force, of which the operating voltage range of piezoelectric actuators will decrease. This paper presents a novel stator design for producing the normal force in which the driving voltage has the same piezoelectric polarity, which is based on the structure of two multilayer piezoelectric actuators clamped in a star-shaped shell. To obtain the two close resonance frequencies of flexural and translation modes, a genetic algorithm combined with the finite element analysis is employed to find the optimal dimensions for the geometry of the stator. The importance of each design parameter is evaluated through a proposed sensitivity analysis method. A prototype resulting from the optimal design was fabricated and the experimental results are given to show that the stator can generate, in practice, the required coupling resonance mode between 35.15 kHz and 36.49 kHz.

OS0703 高温における燃料インジェクター用多層圧電アクチュエータの電気力学応答

OS0703 高温における燃料インジェクター用多層圧電アクチュエータの電気力学応答

Characterization of a piezoelectric valve for an adaptive pneumatic shock absorber

This paper describes a pneumatic valve based on a multilayer piezoelectric actuator and Hörbiger plates. The device was designed to operate in an adaptive pneumatic shock absorber. The adaptive pneumatic shock absorber was considered as a piston–cylinder device and the valve was intended to be installed inside the piston. The main objective for the valve application was regulating the gas flow between the cylinder’s chambers in order to maintain the desired value of the reaction force generated by the shock absorber. The paper describes the design constraints and requirements, together with results of analytical modelling of fluid flow verified versus experimentally obtained data. The presented results indicate that the desired performance characteristics of the valve were obtained. The geometrical constraints of the flow ducts were studied and the actuator’s functional features analysed.

Memory characteristics of hysteresis and creep in multi-layer piezoelectric actuators: An experimental analysis

In this paper we provide an experimental characterization of creep and hysteresis in a multi-layer piezoelectric actuator (PEA), taking into account their relationships in terms of memory structure. We fit the well-known log-t model to the response of the PEA when driven by piecewise-constant signals, and find that both the instantaneous and the delayed response of the PEA display hysteretic dependence on the voltage level. We investigate experimentally the dependence of the creep coefficient on the input history, by driving the PEA along first-order reversal curves and congruent minor loops, and find that it displays peculiar features like strict congruence of the minor loops and discontinuities. We finally explain the observed experimental behaviors in terms of a slow relaxation of the staircase interface line in the Preisach plane.

Design of a Semi-Oval Shaped Ultrasonic Motor

A low voltage drive linear ultrasonic motor with a semi-oval shaped stator is proposed in this paper. In the stator, two multilayer piezoelectric actuators are clamped in the holder of the stator by pre-stressing to excite a semi-oval ring. The semi-oval shaped stator is designed to have normal vibration and tangential vibration modes, thus these two orthogonal mechanical vibration modes of the stator can be excited to generate elliptical motion at the contact point of the stator. In design of the motor, ANSYS finite element analysis software was used in this study to accomplish the design and analysis. A prototype motor was fabricated and measured. For single phase signal driving, typical output of the prototype is a no-load speed of 88 mm/s and maximum thrust force of 1.96 N at a voltage of 16 Vp. For two sine wave signals driving, typical output of the prototype is a no-load speed of 106 mm/s and maximum thrust force of 3.33 N at a voltage of 16 Vp.

Characteristics of the Linear Piezoelectric Motor with Semi-Elliptical Stator

A novel design of the semi-elliptical motor based on a double-mode type ultrasonic motor is proposed and analyzed in this paper. Due to the simplification, the semi-elliptical piezoelectric motor can be considered as an improvement of the elliptical piezoelectric motor which we have proposed in the past. The composite structure of the stator in the motor is formed by two multilayer piezoelectric actuators clamped in a semi-elliptical elastic body. In the simulation, finite element modeling of the motor is performed. The geometry of the stator has been computed with the help of the finite element analysis. Then, the dimensions of the stator's structure were determined by making the two resonance frequencies close to each other. In the experiments, the impedance and the displacement response are measured and discussed for understanding the characteristics of the linear piezoelectric motor with a semi-elliptical stator. The motor achieved maximum moving speed of 96 mm/s and the maximum output force of 0.64 N when applying a sine wave of 14Vr driving voltage at 21.2 kHz, while the maximum moving speed of 132 mm/s and the maximum output force of 0.88 N can be achieved if applying two signal driving method of the same voltage.

Robust H∞ Control of Hysteresis in a Piezoelectric Stack Actuator1

This paper describes an H∞ control method for controlling hysteresis in a piezoelectric stack actuator. The actuator used is a high-performance monolithic multilayer piezoelectric stack actuator. The proposed control method involves the use of a capacitor in series with the piezoelectric actuator to provide a measured output voltage which is proportional to the charge on the piezoelectric actuator. The controller is designed based on a model of the hysteresis nonlinearity constructed using experimental data. The parameters in the nonlinear model of the system are obtained from the measurements on the piezoelectric actuator circuit. Our focus in this paper is to develop a tracking controller based on a charge output of the piezoelectric actuator system and to reduce the hysteresis nonlinearity. The paper considers a robust H∞ tracking controller to control the piezoelectric actuator based on an uncertain system model. Experimental results show that the hysteresis can be significantly reduced and the measured output can closely track a 5 Hz sawtooth reference input signal when the H∞ controller is used.

A novel piezohydraulic aerospace servovalve. Part 1: design and modelling

Servovalves are compact, accurate and high-bandwidth modulating valves widely used in aerospace, defence, industrial and marine applications. However, manufacturing costs are high due to high part count and tight tolerances required, particularly in the first stage of the valve, and due to manual adjustments required as part of the set-up process. In this research, a novel servovalve concept is investigated that has the potential to be more cost-effective. In particular, for the first time, a piezoelectric first-stage actuator is developed to move a servovalve spool using the deflector jet principle; this is especially suited to aerospace actuation requirements. In the new valve, the conventional electromagnetic torque motor is replaced by a multilayer bimorph piezoelectric actuator. The bimorph deflects a jet of fluid to create a pressure differential across the valve spool; hence the spool moves. A feedback wire is used to facilitate proportional spool position control via mechanical feedback. The bimorph is directly coupled to the feedback wire and is immersed in hydraulic fluid. A high-order non-linear model of the valve has been developed and used to predict valve static and dynamic characteristics and is described in this article. This makes use of stiffness constants derived analytically for the bimorph-feedback wire assembly and cross-referenced to finite element analysis predictions. The model of the flow force acting on the deflector is an approximation of the force characteristic found from computation fluid dynamic analysis. The measured characteristics of the prototype valve are in good agreement with the simulation results and prove that the operational concept is viable.