PZT Actuator Research Articles

Effect of stress on the phase transition and optimizing electric-induced strain behavior of Bi0.5Na0.5TiO3-SrTiO3 lead-free co-fired multilayer piezoactuators

A series of (1-x)Bi1/2Na1/2TiO3-xSrTiO3+0.05 wt% MnO2 lead-free multilayer piezoactuators was prepared using a tape casting method, and the field-induced strain performance, temperature stability, electric fatigue and load characteristics were evaluated to assess potential practical applications. In contrast to traditional PZT ceramics, the fabrication of BNT bulk ceramics into multilayer piezoactuators provides significantly decreased strain (S)-electric field (E) characteristics as a result of internal compressive residual stress. The inactive edge distance, sintering temperature and layer thickness were all found to affect the compressive residual stress of the actuator. Through reconstructing the material composition and structure of BNT-ST actuators, active strain (0.168 %, 2 kV/mm), total strain (>0.15 %, E ≤ 2.5 kV/mm) and blocking stress (42.6 MPa) were realized in BNT-based cofired multilayer actuators, displaying a better performance than commercial PZT actuators. These results indicate that environmental-friendly BNT-based lead-free multilayer piezoactuators are promising candidates with regard to practical applications.

Hybrid control of piezoelectric flexible manipulator based on Volterra filtered-xLMS algorithm

To suppress the nonlinear vibration of the flexible manipulator during motion, this article presents a hybrid control strategy based on a servo motor and a piezoelectric actuator. The dynamic model of the piezoelectric flexible manipulator is established first. To realize the trajectory tracking, a proportional derivative control method is used to schedule the control torque. Because the Volterra filter can approximate the nonlinear system model, a Volterra filtered-xLMS algorithm based on a second-order Volterra filter structure is proposed, by which the active nonlinear vibration control of flexible link is realized. Simulation results show that the proposed Volterra filtered-xLMS algorithm can not only make use of the advantages of the classical filtered-xLMS algorithm but also solve the problem of effective modeling of nonlinear secondary path. The proposed hybrid control strategy based on Volterra filtered-xLMS algorithm and proportional derivative control algorithm can improve the position accuracy of joint and effectively suppress the vibration response of the nonlinear flexible link. A piezoelectric flexible manipulator with PZT (lead zirconate titanate) sensor and actuator is designed to demonstrate the validity and efficiency of the proposed method by experiments. Experiment results demonstrate that the attenuation time of vibration response is reduced from 5 s to 1.5 s, the vibration response at the first-order frequency is reduced by 60%, and the proposed methodology has an important advantage in application of active vibration control of piezoelectric flexible manipulator.

PZT Actuators’ Effect on Vibration Control of the PRRRP 2-DOF Flexible Parallel Manipulator

Thanks to their advantages over rigid ones, interest for lightweight parallel manipulator was increased. Besides, structural flexibility effects at high operational speeds are more significant. Thus, developing an appropriate model for the assessment of the dynamic properties of flexible mechanisms and linkages to gain effective vibration control will raise high demand. Therefore, this paper represents the dynamic and kinematic modeling using the assumed mode method and first-type Lagrange equations of the 2-DOF planar parallel manipulator with two flexible links. To truly predict vibrations of the manipulator without any major simplifying assumptions, nonlinear dynamic modeling, which thoroughly attempts to represent the flexible behavior of the links, is considered. As a result, an active damping approach is being studied with PZT actuators. The results show that this approach is effective in damping the vibrations of the links that give accurate trajectory control.

Direct-Write Piezoelectric Transducers on Carbon-Fiber-Reinforced Polymer Structures for Exciting and Receiving Guided Ultrasonic Waves.

Advancements in the structural health monitoring (SHM) technology of composite materials are of paramount importance for early detection of critical damage. In this work, direct-write transducers (DWTs) were designed for the excitation and reception of selective ultrasonic guided waves and fabricated by spraying 25- [Formula: see text]-thick piezoelectric poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TRFE)] coating with a comb-shaped electrode on carbon fiber-reinforced polymer (CFRP) plates. The characteristics and performance of the ultrasonic DWTs were benchmarked with the state-of-the-art devices, discrete lead zirconate titanate (PZT) ceramic transducers surface-mounted on the same CFRP plates. The DWTs exhibited improved Lamb wave mode excitation (A0 or S0 mode) relative to the discrete PZT transducers. Moreover, high signal-to-noise ratio was obtained by effectively canceling other modes and enhancing the directivity with the periodic comb-shaped electrode design of the DWTs, despite the smaller signal amplitudes. The enhanced directivity overcompensates for lower amplitude attenuation, making DWT a good candidate for locally monitoring critical stress hot spot regions in the CFRP structure prone to early damage initiation. It is shown that pairing a DWT sensor with a discrete PZT actuator could further achieve balanced performance in both wave mode selection and signal amplitudes, making this combination really attractive for ultrasonic SHM.

Investigations on axially compressed composite cylindrical shells with surface bonded PZT

Smart materials integrated with thin walled structures can be used to achieve the desired shape, stiffness, damping and other mechanical properties of structures in response to the induced changes in temperature, electric or magnetic field in these, without causing any significant change in the mass as is required in aerospace applications. In this paper, the effects of surface bonded piezo ceramic (PZT-Lead Zirconate Titanate) actuation patches to enhance the strength of thin composite cylindrical shells have been studied experimentally and numerically under the actuation of PZT. The study reveals that it is feasible to minimize the effects of the local imperfections and increase the strength closer to the theoretical buckling strength. However, it has been found that even with the currently available PZTs with minimum thickness, the strength of the tested shell increases owing to the added stiffness of the PZT than due to the actuation. Furthermore, with thinner PZTs of thickness of the order 0.01 times the thickness of the shell and with high actuation force, improvements in the shell capacity is possible by the application of voltage. In addition, the actuation of PZT can be used to decrease the radial buckling deformation for any given load. Importantly, the effect of PZT actuation would increase if the initial imperfections are large leading to larger reductions in the ultimate strength of the shell. Finally, a numerical procedure is established to corroborate the experimental results and also for arriving at an optimum PZT configuration.

Displacement amplification and differential actuation in piezo driven nanopositioners

We study a novel piezo-driven nanopositioning mechanism in the horizontal plane. For each horizontal axis, we employ two externally leverage mechanisms with flexure hinges to provide bilateral displacement of the output stage as well as amplified displacement with respect to strokes of two piezo stack actuator. The bilateral amplified motion is achieved by differential actuation of the PZT stack pair of each axis. We also designed a housing structure for the nanopositioner with holes and trenches for safe and neat wiring. It also provides proper installation on the optical table and allows incorporation of auxiliary parts to hold and and align capacitive displacement sensors for precise measurements. We designed wedge mechanisms that together with the housing and the nanopositioner structure allow proper alignment of PZT stacks during installation as well as preloading them. Experiments were carried out to identify the ranges of displacements for the output stage as well as the inputs of the leverage mechanism, using Laser-Doppler-Vibrometry and capacitive sensors. We also developed a simple rigid-link-ideal-hinge kinematic model for the leverage mechanism, which was consistent with the experimental results under no external load conditions. However, due to the external loads and elasticity, large deviations exist between the experimental results and the predicted values by the model. The discrepancy revealed a non-reciprocal property of the individual leverage mechanism and the need to employ more accurate flexure hinge models. Experiments show that the proposed nanopositioner amplifies the input stroke of the PZT stacks by a factor around 12 in the differential actuation mode. Compared to the conventional non-differential actuation modes, the differential one provides almost twice stroke for the output stage as well as more linear input–output characteristics. In addition, the proposed structure considerably filters out the off-axis input displacements of the PZT actuators and provides very small parasitic displacements at the output stage. Both channels exhibit almost identical dynamic responses in time and frequency domains, indicating highly symmetric fabrications of the nanopositioner and auxiliary parts for the installation of actuators and sensors.

Finite Element Analysis and Fabrication of an Ultrasonic Milling System

Ultrasound has been adapted in several industrial and manufacturing applications. In this study, an ultrasonic milling system, which can vibrate a rotating tool, was designed and fabricated. Firstly, a lead zirconate titanate (PZT) was designed using finite element analysis, and the obtained peak impedance value of 47.2 ㎑ agreed well with the fabricated PZT value of 48.0 ㎑. Additionally, an aluminum waveguide with two PZT actuators was analyzed, whose impedance characteristic was predicted to be 43.8 ㎑. Consequently, a milling waveguide was fabricated using the analysis results. The impedance value of the fabricated waveguide was measured to be 42.7 ㎑, which was consistent with the finite element analysis result with an error of 2.6 %. The rotational speed and power output were measured to be 10,001 rpm and 122.6 W. Thus, the developed milling waveguide can be applied to the milling process of high-hardness metals.

Integration of buried piezoresistive sensors and PZT thin film for dynamic and static position sensing of MEMS actuator

We developed a lead zirconate titanate (PZT) thin film actuator integrated with buried piezoresistors for the dynamic and static deformation sensing of a PZT MEMS actuator. We demonstrated the fabrication of sol-gel deposited PZT thin film devices combined with buried piezoresistors and proved, for the first time, the process compatibility of these materials. Dopant concentration measured by secondary ion mass spectrometry (SIMS) analysis confirms that the piezoresistor was successfully buried into the device. Motion detection of the fabricated MEMS cantilever actuated by the PZT thin film was successful and consistent with optical measurement as well as design values. From these results, we can conclude that our PZT actuator and piezoresistive sensors can be monolithically integrated. The fabrication process developed here can be used for high-stability piezoelectric MEMS actuators with feed-back control of position.

Use of smart intelligent sensor & actuator mechanical materials (PVDF / PZT) in developing MIMO mathematical model of the smart structure and its use to control the active vibrations using discrete sliding mode control theory with output samples

A multi-input, multi-output based modelling of intelligent flexible mechanical aluminium structures using smart materials with Euler-Bernoulli beam theory & state space techniques is being presented with multi-sensor data fusion concepts. An aluminium cantilever beam of rectangular cross section with known specifications is considered for the modelling purposes. To start with, from the fundamental principles of E-B theory, a Lagrange equation of motion is obtained both for the regular beam element as well as for the PZT & PVDF sensor actuator pair. Following which, a dynamic equation of motion of the smart intelligent structure developed using the smart materials consisting of PZT& PVDF is obtained. The dynamic equation is transformed into a state space model with 2 i/o’s using the concepts of state space theory in control engineering. The model is developed considering the first 2 modes of vibration, which are the most dominant modes in the vibration theory. The developed state space model is used for active vibration control. An external force of 1 N is applied at the end of the smart flexible multivariable multimodel cantilever beam after which the beam is subjected to vibrations. A Discrete Sliding Mode Control (DSMC) based controller on the o/p samples is designed and put in loop with the plant, after which the plant vibrations decays to zero in no time. The mathematical model of the DSMC controller is used to control the vibrations of the plant using the concept of destructive interference. The mathematical model of the DSMC controller can be used to control the vibrations of the plant using the concept of destructive interference.

Development of mathematical model for smart intelligent flexible structures using smart intelligent sensor & actuator materials using Timoshenko beam theory & its control using POF

In this research paper, the multivariable modelling of intelligent flexible aerospace structures using smart materials with Timoshenko beam theory & state space techniques with multi-sensor data fusion concept & its control using POF strategy is presented in n this research article. Finite Element Method is used in the analysis also. An aerospace aluminum cantilever beam of rectangular cross section with known specifications is considered for the modelling purposes. To start with from the fundamental principles of Timoshenko beam theory, a Lagrange equation of motion is obtained both for the regular beam element as well as for the PZT & PVDF sensor actuator pair. Following which, a dynamic equation of motion of the smart intelligent structure developed using the smart materials consisting of PZT & PVDF is obtained. Smart materials have got some special properties that react to the changes in their environmental conditions. This means that some of their special properties can be changed by using an external condition, such as temperature, light, pressure, electricity, voltage, pH, or chemical compounds, which could be considered as the special characteristics and this change is reversible, which can be repeated many times. The dynamic equation is transformed into a state space model with 2 inputs and 2 outputs using the concepts of state space theory in the advanced control engineering. The model is developed considering the first 2 modes of vibration, which are the most dominant modes in the vibration theory. The developed state space model is used for active vibration control. The effect of shear is considered in modelling here, which is neglected in case of Euler – Beam theory, thus giving an accurate beam model. An external force of 1 N is applied at the end of the smart flexible multivariable multimodel cantilever beam after which the beam is subjected to vibrations. A POF controller can be designed and put in loop with the plant, after which the plant vibrations decays to zero in no time. The mathematical model of the POF controller can be used to control the vibrations of the plant using the concept of destructive interference. The work done can also be compared with others to show the authenticity or the profoundness of the methodology that is being developed by us.

Multivariable modelling of intelligent flexible mechanical structures using smart materials with FEM, Euler-Bernoulli beam theory, state space & multi-sensor data fusion techniques

In this research paper, the multivariable modelling of intelligent flexible mechanical structures using smart materials with Euler-Bernoulli beam theory & state space techniques is being presented with multi-sensor data fusion concept. To start with from the fundamental principles of E-B theory, a Lagrange equation of motion is obtained both for the regular beam element as well as for the PZT & PVDF sensor actuator pair. Following which, a dynamic equation of motion of the smart intelligent structure developed using the smart materials consisting of PZT& PVDF is obtained. Smart materials have got some special properties that react to the changes in their environmental conditions. This means that some of their special properties can be changed by using an external condition, such as temperature, light, pressure, electricity, voltage, pH, or chemical compounds, which could be considered as the special characteristics and this change is reversible, which can be repeated many times. The dynamic equation is transformed into a state space model with 2 inputs and 2 outputs using the concepts of state space theory in the advanced control engineering. The model is developed considering the first 2 modes of vibration, which are the most dominant modes in the vibration theory. The developed state space model is used for active vibration control. An external force of 1 N is applied at the end of the smart flexible multivariable multimodel cantilever beam after which the beam is subjected to vibrations. A Periodic Output Feedback controller can be designed and put in loop with the plant, after which the plant vibrations decays to zero in no time. The work done can also compared with others to show the authenticity or the profoundness of the methodology that is being developed by us.

Vibrating-lens-assisted laser drilling

Laser ablation is a viable technology for the manufacture of deep holes in a variety of industrial applications. Therefore, approaches need to be sought that increase the efficiency of these processes. In the current work, a hybrid processing method that utilizes superimposed vibrations to increase the depth of the produced holes will be addressed. The rationale for using vibrations is to change the energy distribution of the laser beam during the process. To this end, the traditional and the vibrating-lens methods were studied from the energy distribution standpoint at locations along the sensitive direction of the laser beam in drilling processes. Comparing the fluence with the ablation threshold of the laser beam to remove the material, the reasons why the vibrating-lens method is more effective in drilling deep holes were explained through theoretical analysis. Then, a new structure for the generation of lens vibrations along the sensitive direction using a PZT actuator for vibrating-lens assisted picosecond laser processing based on simulations was designed. Finally, different parameters were used to drill holes in stainless steel by the traditional and the vibrating-lens assisted methods, considering the frequency of the vibrations, dwell time and defocusing distance. The results have shown that the vibrating-lens method can improve the depth of the holes up to 60 % compared to the traditional method at the same dwell time. Therefore, it improves the efficiency of the deep hole drilling process.

Design and Experimental Analysis of Composite Material with Piezoelectric Layer

The main objective of this work is to analyze the active vibration control using smart sensors and actuators in a laminated E-Glass/epoxy cyanate composite beam. The cantilevered composite beam has piezoelectric ceramic patches as smart sensors and actuators. Hand layup technique for vibration suppression is done on the fabricated E-Glass/Epoxy-cyanate composite laminated beam. Experimental modal testing is performed to achieve vibration suppression on the flexible composite beam bonded with seven circular type piezoelectric actuator elements and seven circular type sensor elements. The complete vibration suppression utilizes a data acquisition system, a real-time control system, and a functional generator, in addition to the composite beam with PZT sensor and actuator. The data acquisition hardware consists of model NI 9233 (4 channel +5 V 24 Bit IEPE Analog input I2VA 1-to earth ground).

Intelligent Manipulator with Flexible Link and Joint: Modeling and Vibration Control

This paper presents a finite-element (FE) model of a manipulator with a flexible link and flexible joint as well as embedded PZT actuators and proposes a corrected rebuilt reduced model (CRRM) to make its dynamic characteristics more consistent with reality and facilitate control design. The CRRM considers the holding torque of the manipulator driving motor and eliminates the response divergence induced by a fault of the mass matrix of the FE model. In order to reduce the dimensions and maintain the precision of the model, an iterated improved reduction system (IIRS) method is adopted. Additionally, a LQR controller is designed based on the output function of the improved model. The simulation results demonstrate that the CRRM is consistent with reality and the active controller has good performance in suppressing vibration of the manipulator with both the flexible link and the flexible joint.

High precision displacement-measuring interferometer based on phase modulation technique and modulation index effect elimination

A high precision displacement-measuring interferometer based on a phase modulation technique was developed. A PZT actuator was utilized to drive a mirror of a Michelson interferometer by applying a sinusoidal voltage to the PZT controller. The path difference between two arms of the interferometer was modulated leading to modulation in the phase of the interference signal with a frequency of 3 kHz. The first and second harmonics of the interference signal were detected at the modulation index of 2.63 rad, a special value when the values of the first and second orders of Bessel function are equal. The displacement was determined by the ratio of the first and second harmonic in which the effects of modulation index instability and intensity fluctuation were neglected. The phase modulation interferometer using a PZT actuator has no amplitude modulation effect compared with other modulation interferometers using EOM (electro-optics modulator) or modulation the injection current of a laser diode. Moreover, the direction of the displacement that was ambiguous of the traditional interferometers was clarified in a real time. A measurement precision of 60 nm was obtained using the phase modulation interferometer.

Investigation of in-plane wave motion in a Fibre Metal Laminate using PVDF foil sensors

Structural Health Monitoring (SHM) via Guided Ultrasonic Waves (GUW) has been the subject of research for years and has already been described in detail for purely isotropic and purely anisotropic materials. Fibre Metal Laminates (FML) combine isotropic metal layers with anisotropic fibre composite layers to a laminate. They are mainly used in the aerospace industry to reduce mass while optimizing stiffness and strength properties. On the other hand, the combination of different materials leads to high differences in the acoustic impedance at the interfaces, which in turn leads to the question to what extent these materials can be monitored via GUW. This research investigates the applicability of polyvinylidene fluoride (PVDF) foil sensors for the detection of GUW in the interior of an Aluminium Glass Fibre laminate. Preliminary analytic investigations based on new adaptions of the partial-wave method gave insight into general GUW characteristics along fibre-metal interfaces and within an FML plate waveguide. Analytic and transient finite element simulation results were used to predict displacement fields. Composition and dimension of fabricated FML plates as well as excitation frequency were chosen based on these predictions, particularly maximizing dominance of the in-plane displacement components. For manufacturing the FML specimen with embedded PVDF sensors, a cold-curing epoxy resin was used to prevent the temperature-sensitive sensors from being destroyed or depolarized during production. After the design and application of a PZT actuator on the laminate, GUW were excited with particular attention to the frequencies in which a particularly dominating in-plane displacement field was assumed. Laser-Doppler Vibrometry (LDV) was used for measurements of the GUW's out-of-plane component.

A novel design and fabrication of a micro-gripper for manipulation of micro-scale parts actuated by a bending piezoelectric

In this study, a novel micro-gripper using a piezoelectric actuator was designed and improved by the design of experiments (DOE) approach. Using a bending PZT actuator connected to the micro-gripper by a rigid wedge can be considered as a novel approach in this field. Almost all of the similar grippers in this category were former actuated by a piezo-stack which has some limitations and difficulties like fabrication in MEMS proportions. The basic design was borrowed from compliant mechanisms that are suitable for MEMS application and easy to manufacture in micro-scale because of the intrinsic integration characteristic. Since stress concentration is common in flexure hinge compliant mechanisms, our focus was to consider strength as an important factor in our design. Finite element analysis tools were used to implement the DOE based on two criteria; minimizing stress concentration and maximizing the output displacement in the micro-gripper structure as much as possible with the consideration of the total size of the gripper. The experiment was performed to validate the simulation results and experiment results agreed well with the simulation one. The slight geometrical discrepancy in significant portions of structure like flexure hinges partially contributes to the accumulated error between the simulation and the experiments.

A PZT Actuated 6-DOF Positioning System for Space Optics Alignment

Due to limitations in the fabrication technology, the large aperture space optical mirror is always spliced into several small segments rather than fabricated monolithically. To guarantee the imaging quality of the system, each segment needs to be aligned at micron-level precision with millimeter-level range. For this purpose, a PZT actuated six-axis high-precision positioning system, which consists of three serially connected parallel mechanisms is proposed in this article. Compared with previous 6-DOF positioning solutions, such as a Stewart platform, the proposed design features a relatively compact structure and straightforward kinematics. To realize long stroke and fine resolution simultaneously, bridge-type amplifiers are employed to enhance the stroke of the PZT actuation, and the flexure hinges are utilized to eliminate friction and backlash. The performance of the amplifier under two kinds of external loads are analyzed so that the amplifiers could be designed according to the application conditions. Furthermore, it can be found that the displacement sensors must be employed at the output end of the actuation module to eliminate the input coupling that commonly exists in the compliant mechanisms. The feasibility of the design is validated by finite-element analysis and experiment study. The maximum stroke is 2.1 mm in the Z -axis, and the finest resolution is 0.5 μ m in X - and Y -axis.

Synergetic approach in attitude control of very flexible satellites by means of thrusters and PZT devices

The interaction between angular motion and flexible vibrations can heavily affect the stability of the spacecraft. Many control strategies have been developed for solving this issue. Some of them are focused on the attitude dynamics while a different approach consists in facing the problem from the structural point of view, trying to actively damp the vibrations induced by the attitude control, using smart material (like piezoelectric) devices.In this research, an approach unifying the two aspects is proposed. The satellite is modeled as a flexible multibody system, in which the two sets of actuators (attitude and structural devices) are commanded by means of a common sliding mode control algorithm. In such a way, the two systems are not considered as competitors (each one trying to cancel the disturbing effects caused by the other one), but they are cooperating for the common goal of acquiring a desired attitude in a given time without residual oscillations. This synergetic approach is first developed in a numerical environment, then it is tested by means of a free-floating platform equipped with flexible appendages, designed and built as a multilayer composite material with a net of embedded PZT patches (sensors and actuators). The overall navigation and control loop is based on the information coming from the Inertial Measurement Unit and from the PZT sensors, which are filtered and sent to the Synergetic controller, with the goal of reaching a desired attitude. The output of the Synergetic controller consists in both the thrusters firing sequence and the PZT actuators voltage difference required to reach the goal. The experimental results are compared with the ones obtained by more classic approaches (attitude and structural control computed independently), commenting both advantages and drawbacks of the different approaches.

Heat transfer enhancement of turbulent channel flow using a piezoelectric fan

This study experimentally investigated the flapping dynamics of a piezoelectric (PE) fan in channel flow and the resultant wall heat-removal performance enhancement. The PE fan consisted of a rigid PZT (Lead zirconate titanate) actuator and a flexible PET (Polyethylene terephthalate) blade. The PE fan in absence of electric excitation or air flow was chosen as the baseline data configuration. The mid-span of the PE fan was illuminated by a laser sheet, and the instantaneous profiles of the PE fan were captured by a high-speed camera system; the structure boundary detection algorithm and fast Fourier transform algorithm were used to identify the flapping amplitude and frequency. The time-averaged heat transfer performance across the channel wall with constant heat flux boundary condition was spatially resolved by the temperature sensitive paint measurement. The piezoelectric fan displayed the largest flapping amplitude at the fundamental resonant frequency of 43 Hz. The amplified flapping amplitude and the increased frequency were achieved with the elevation of the Reynolds number, and correspondingly the resultant heat transfer performances were improved. At a low Reynolds number of 1.37×104, the piezoelectric fan blade flapped synchronously with the PZT actuator, while the flapping amplitude was considerably intensified to 0.72 times the blade length under excitation voltage of fundamental resonant frequency, resulting in a 30% augmentation in the local Nusselt number. At a high Reynolds number of 1.91×104, the flapping frequency was locked to its flutter frequency 64.5 Hz, regardless of the excitation voltage frequency. The flapping amplitude and the resultant heat transfer performance were found to be insensitive to the excitation voltage frequency at a Reynolds number of 1.91×104, although the maximum local heat transfer was enhanced by 46% at an excitation voltage frequency 43 Hz.