Pair Of Piezoelectric Actuators Research Articles

Dynamic Control of Contractile Force in Engineered Heart Tissue

Here, we demonstrate a technique to control afterload while monitoring contractile force exerted by EHTs. We developed an apparatus that can regulate EHT boundary conditions using real-time feedback control. The system is comprised of a pair of piezoelectric actuators that can strain the scaffold and a microscope that can measure EHT force and length. Closed loop control allows dynamic regulation of effective EHT boundary stiffness. When controlled to switch instantaneously from auxotonic to isometric boundary conditions, EHT twitch force immediately doubled. Changes in EHT twitch force as a function of effective boundary stiffness were characterized and compared to twitch force in auxotonic conditions. EHT contractility can be regulated dynamically through feedback control of effective boundary stiffness. The capacity to alter the mechanical boundary conditions of an engineered tissue dynamically offers a new way to probe tissue mechanics. This could be used to mimic afterload changes that occur naturally in disease, or to improve mechanical techniques for EHT maturation.

Optimal Voltage Distribution on PZT Actuator Pairs for Vibration Damping in Beams with Different Boundary Conditions

In recent decades, many studies have been conducted on the use of smart materials in order to dampen and control vibrations. Lead zirconate titanate piezoceramics (PZT) are very attractive for such applications due to their ability of delivering high energy strain in the structure. A pair of piezoelectric actuators can actively dampen the resonances of the structure, but the damping effectiveness strongly relies on its location. Damping effectiveness can be substantially increased if the structure is fully covered with PZT actuator pairs and the voltage distribution on each pair is optimized. In this way, each actuator pair contributes to the vibration attenuation and only the driving voltage’s sign, distributed on each actuator pair, needs to be identified for each resonance. This approach is here applied to the case of Euler–Bernoulli beams with constant cross-section and the optimal voltage distribution is investigated for several boundary conditions. The theoretical model results were corroborated with finite element simulations, which were carried out considering beams covered by ten PZT actuator pairs. The numerical results agree remarkably well with the theoretical predictions for each examined case (i.e., free-free, pinned-pinned, and fixed-fixed).

A novel approach to reduce fan rotor blades stress in case of resonance due to inlet flow distortion by means of piezoelectric actuators

Resonant vibration condition involves a drop in the life-cycle of the components and is one of the main causes of high cycle fatigue failure (HCF) in turbomachinery blades. As a consequence vibration damping techniques play a key role for turbomachinery designers. Even though resonant vibration conditions can be identified by means of the Singh’s Advanced Frequency Evaluation (SAFE) diagram at the design level, not all resonant conditions can be avoided. Among these methods, systems of piezoelectric (PZT) actuators can be tuned to actively damp the vibrations caused by resonant excitations. In this work, an analytical model was developed to identify the optimal voltage distribution that maximises the reduction in blade stress. The model considers the flexural–torsional–extensional deformations coupling due to the pre-twisting, non-constant cross-section and inertial loads of the rotating blades. A typical case was examined to demonstrate the effectiveness of the proposed method, which involved vibration induced by inlet flow distortion in an axial fan stage coupled with a three-strut front frame. A decoupled approach based on Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) simulations was used to evaluate the aerodynamic loads and to numerically validate the optimal voltage distribution on the PZT actuator pairs. The results show that the proposed method alleviates the effects of the resonant response to an inlet flow distortion on a fan integrally bladed disc (blisk) and the optimal voltage distribution predicted by the model is the one that achieves the highest blade stress mitigation.

Dynamic Modeling and Analysis of a Rotating Piezoelectric Smart Beam

In active vibration control study, piezoelectric actuators and sensors are bonded on the surface of a beam. They can change the frequency and modal characteristics of the system. This paper presents an analysis of the frequency response to a rotating piezoelectric smart beam. Hamilton’s principle along with the assumed mode method are employed to derive the governing equations of the first-order approximate coupling model for the piezoelectric smart beam. The coupling is taken into account as the second-order coupling effect of the axial elongation caused by the transverse displacement of the beam. Then, the equations are transformed into a dimensionless form after identifying the necessary parameters. The dimensionless natural frequencies of the piezoelectric smart beam corresponding to the bending and stretching vibrations are obtained through a numerical simulation, with comparison made of those of the beam with no actuator or sensor. Furthermore, the implication is investigated of the structural parameters and bond location on the piezoelectric actuators and sensors. Besides, the common case of a smart beam bonded with multiple pairs of piezoelectric actuators and sensors is studied, and the effects of the first natural frequency and tip deformation are analyzed. The research provides a theoretical reference for the optimization of structural parameters and location of piezoelectric actuators and sensors, thereby preventing the resonance when the excitation frequency is approximately equal to the natural frequency of the beam.

Active vibration control of a beam instrumented with MWCNT/epoxy nanocomposite sensor and PZT-5H actuator, robust to variations in temperature

Multi walled carbon nano tube (MWCNT)/epoxy nanocomposite strain sensor and piezoelectric actuator pair are used in active vibration control (AVC) of a smart cantilevered beam. Due to different coefficients of thermal expansion of MWCNT and epoxy, the resistance of carbon nanotube/epoxy based strain sensor changes nonlinearly with change in temperature. The temperature dependence of CNT based strain sensor is modelled by fitting a polynomial curve on the experimentally obtained characterization data of CNT/epoxy strain sensor. Using augmented constitutive equations of piezoelectricity, finite element model of smart cantilevered beam instrumented with collocated nanocomposite strain sensor and PZT-5H actuator is derived. Effect of temperature on PZT-5H actuator is also considered in derivation of the control law. Active vibration control of the first mode of a smart cantilevered beam instrumented with collocated CNT based strain sensor and PZT-5H actuator is performed at ambient temperature and at temperature slightly away from the ambient temperature for two cases: (1) without considering the temperature dependence of CNT composite strain sensor in Kalman observer and (2) considering the temperature dependence of CNT composite strain sensor in Kalman observer. Simulations are also performed to visualize the behaviour of smart beam when the beam is subjected to a temperature impulse. This paper suggests a novel AVC strategy using MWCNT/epoxy strain sensor and PZT-5H actuator patch that is robust to variations in temperature.

Shared inductor hybrid topology for weight constrained piezoelectric actuators

This paper presents a new circuit topology designed to minimise the weight of the control circuit required to actuate multiple piezoelectric actuators. It can independently set the phase and bias voltage on each piezoelectric actuator through the use of a single inductor. This is highly desirable in weight constrained applications such as unmanned aerial vehicles as the ferroelectric material required for the inductor is heavy. Furthermore, the circuit topology can also use the same inductor to generate the high bias voltage required to drive the actuators. The full system has been verified in PSpice and a pair of piezoelectric actuators have been successfully driven using off the shelf components.

S1620204 同一平面内を高速位置決めするXYステージの基礎特性

A highly precise positioning actuator for a Scanning Prove Microscopy (SPM) and a magnetic recording evaluation system has been developed. The positioning actuator call the Nano-Motion Actuator (NMA) that is consisted of a displacement amplifier mechanism and a stacked piezoelectric element. In this paper, we propose a new two dimensional positioning actuator call the Nano-Motion Stage (NMS) that is composed of two pair of piezoelectric actuators, parallel links with square support spring and a positioning stage. The control performance and the positioning accuracy are verified. Furthermore, the influence of the tracking actuator on the transient response and the out-of-plane moments of the precise positioning stage with a stacked piezoelectric element has been discussed.

High-speed discrimination and sorting of submicron particles using a microfluidic device.

The size- and fluorescence-based sorting of micro- and nanoscale particles suspended in fluid presents a significant and important challenge for both sample analysis and for manufacturing of nanoparticle-based products. Here, we demonstrate a disposable microfluidic particle sorter that enables high-throughput, on-demand counting and binary sorting of submicron particles and cells using either fluorescence or an electrically based determination of particle size. Size-based sorting uses a resistive pulse sensor integrated on-chip, whereas fluorescence-based discrimination is achieved using on-the-fly optical image capture and analysis. Following detection and analysis, the individual particles are deflected using a pair of piezoelectric actuators, directing the particles into one of two desired output channels; the main flow goes into a third waste channel. The integrated system can achieve sorting fidelities of better than 98%, and the mechanism can successfully count and actuate, on demand, more than 60,000 particles/min.

REJECTION OF HARMONIC AND TRANSIENT DISTURBANCES OF A SMART STRUCTURE WITH PIEZOELECTRIC ACTUATORS

Light flexible structures are easily prone to vibrate due to external forces or due to forces generated in the inner structure. This situation is common in machinery or mechanical structures with rotational devices. The unwanted vibration of such structures can be compensated with the addition of piezoelectric actuators for active vibration control (AVC). The rejection of harmonic disturbances is frequently done with controllers based on the internal model principle. The goal of this research is to reduce the effect of harmonic disturbances with known (measured) time-varying frequencies acting on a system as well as to increase the damping of the system for the transient response (first mode of vibration). The experimental setup is made up of a slender aluminium flexible beam, a pair of piezoelectric actuators, an accelerometer and two DC motors, as well as the data acquisition and signal conditioning equipment. The harmonic disturbance is generated by DC motors. The control design utilizes an augmented description of the plant. The plant including the disturbance is modelled as a polytopic linear parameter-varying (pLPV) system. An observer-based gain-scheduling controller is calculated based on quadratic stability and the stability is guaranteed for the specified range of variation of the scheduling parameters, also restriction in the performance is introduced in the sense of the H 2 -norm. Experimental results show very good disturbance cancellation.

Free Vibration of Cross Ply Laminated Beams with Multiple Distributed Piezoelectric Actuators

ABSTRACTAnalytical solution is obtained for the free vibration of cross-ply laminated beams with multiple distributed extension piezoelectric actuators. The piezoelectric actuators are bonded at local position on the beam surface. The beam structure can contain one pair or two pairs or n pairs of piezoelectric actuators and it can be symmetric or unsymmetric about its mid-plane. The equations of motion and associated boundary conditions are derived for the beam model using Hamilton's principle. The state-space approach is used to find accurate natural frequencies and mode shapes for arbitrary combinations of boary conditions. The exact analytical solutions obtained are illustrated numerically in a number of figures revealing the influences of varying some parameters for the symmetric and unsymmetric cross-ply laminated beam for different type of piezoelectric actuators cases. The first order shear deformation beam theory (FOBT) is used to present the effect of actuators position and length on the nondimensional frequencies when one pair and two pairs of piezoelectric actuators are bonded at a local position on the beam surface.

Dynamics and vibrations of structures with bonded piezoelectric strips subjected to mechanical and unsteady aerodynamic loads

This article presents an analysis of the dynamics of damaged structures with bonded piezoelectric strips executing flexural oscillations generated by mechanical loads, piezoelectric actuators or unsteady aerodynamic loads. These oscillations can be used to detect the presence of cracks for structural health monitoring. The proposed method of crack detection uses pairs of piezoelectric strip sensors bonded on the opposite sides of the structure and is based on the fact that the presence of a crack causes a difference between the strains measured by the two sensors of a pair. The structural analysis presented in this article uses a non-linear model for the cracks and a finite-element formulation for the piezoelectric strips coupled with the structure. A panel method is used to determine the unsteady aerodynamic loads acting on the oscillating wing structure. This study includes the dynamic analysis in the frequency domain of a cracked plate undergoing forced flexural vibrations in a range of frequencies generated by a pair of piezoelectric actuators. The dynamic analysis in the time domain is also performed for the oscillating structures with piezoelectric strips subjected to mechanical or unsteady aerodynamic loads. It was found that this method is quite effective in detecting cracks in the wing structures subjected to oscillatory aerodynamic loads.

보의 진동제어를 위한 압전 액추에이터의 길이변화 효과 연구

This paper presents an approach to define an optimal piezoactuator length to actively control structural vibration. The optimal ratio of the piezoactuator length against the beam length when a pair of piezoceramic actuator and accelerometer is used to suppress unwanted vibration with direct velocity feedback(DVFB) control strategy is not clearly defined so far. It is well known that DVFB control can be very useful when a pair of sensor and actuator is collocated on structures with a high gain and excellent stability. It is considered that three different collocated Pairs of piezoelectric actuators (20, 50 and 100 mm long) and accelerometers installed on three identical clamped-clamped beams(<TEX>$30{\times}20{\times}1mm$</TEX>). The response of each sensor-actuator pair requires strictly positive real(SPR) property to apply a high feedback gain. However the length of the piezoactuator affects the SPR property of the sensor-actuator response. Intensive simulation and experiment show the effect of the actuator length variation is strongly related with the frequency range of the SPR property. Thus an optimal length ratio was suggested to obtain relevant performance with a good stability under the DVFB strategy.

Sliding‐mode control of a three‐degrees‐of‐freedom nanopositioner

AbstractThis paper presents the sliding‐mode control of a three‐degrees‐of‐freedom nanopositioner (Z, θx, θy). This nanopositioner is actuated by piezoelectric actuators. Capacitive gap sensors are used for position feedback. In order to design the feedback controller, the open‐loop characteristics of this nanopositioner are investigated. Based on the results of the investigation, each pair of piezoelectric actuators and corresponding gap sensors is treated as an independent system and modeled as a first‐order linear model coupled with hysteresis. When the model is identified and the hysteresis nonlinearity is linearized, a linear system model with uncertainty is used to design the controller. When designing the controller, the sliding‐mode disturbance (uncertainty) estimation and compensation scheme is used. The structure of the proposed controller is similar to that of a proportional integral derivative controller. Thus, it can be easily implemented. Experimental results show that 3‐nm tracking resolution can be obtained. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

Dynamics of Structures with Piezoelectric Sensors and Actuators for Structural Health Monitoring

The dynamic analysis of structures with piezoelectric sensors and actuators is used in this paper to establish a method for crack detection in aerospace structures. Piezoelectric strips used as sensors and actuators are bonded on both sides of a thin structure which executes flexural oscillations. The differential voltage outputs of the piezoelectric sensors are used to detect the presence of cracks in the structure. The structural analysis uses a finite element formulation for the piezoelectric strips coupled with the structure and a nonlinear model for the cracks. This paper presents first the results of the dynamic analysis in the frequency domain of healthy and cracked plates undergoing forced flexural vibrations generated by a pair of piezoelectric actuators submitted to an oscillatory voltage excitation. The peaks in the differential voltage output obtained in the case of a cracked plate at several frequencies during the frequency sweep were found to be indicative measures for the presence of a crack in the structure. The results of the dynamic analysis in the time domain have also shown that this method has a good sensitivity in detecting cracks in the structures.

Generation of prescribed strain waves in an elastic bar by use of piezoelectric actuators driven by a linear power amplifier

The problem of generating prescribed strain waves in an elastic bar by means of a pair of piezoelectric actuators driven in phase by a linear power amplifier was considered theoretically and experimentally. The power amplifier was characterized by its DC voltage gain and 3 dB cut-off frequency unloaded, and by its output resistance and inductance. With the assumption of one-dimensional (1D) wave propagation in the bar, including the actuator region, a linear difference equation was derived for the required input voltage to the power amplifier in terms of the strain associated with the prescribed wave. This difference equation was solved numerically for a bell-shaped strain wave and for a single-period sine strain wave. After identification of the linear power amplifier, two tests were carried out with the aim to generate the two strain waves in an aluminium bar instrumented with semi-conductor strain gauges. Very good agreement was obtained between the implemented and required input voltages, output voltages and output currents of the power amplifier, and good agreement was achieved between the implemented and prescribed strain waves.

Piezoelectric generation of extensional waves in a viscoelastic bar by use of a linear power amplifier: Theoretical basis

A system consisting of a linear power amplifier driving a piezoelectric actuator pair attached to a long viscoelastic bar is analysed. Coupled piezoelectric theory is used, and allowance is made for the dynamics of the amplifier and of the actuators. Formulae are derived for the relation between the input voltage to the amplifier and the normal force associated with extensional waves generated in the bar and for the load impedance constituted by the actuator-bar assembly. It is established that the mechanical work performed on the external parts of the bar at the actuator/bar interfaces is at most equal to the electrical energy supplied by the amplifier. The results are applied to a three-parameter viscoelastic bar and to an elastic bar, and the effects of the cut-off frequency, without load, and the output impedance of the amplifier are examined. For the elastic bar, sharp response minima occur at frequencies that are integral multiples of the inverse transit time through the actuator region. For the viscoelastic bar, the corresponding minima are less sharp and deep. The input voltage to the amplifier required to produce a desired output wave at the actuator/bar interfaces can be determined provided that the spectrum of this wave is not too broad.

Optimal positioning of piezoelectric actuators on a smart fin using bio-inspired algorithms

In this paper a novel approach is developed for optimization of piezoelectric actuators in vibration suppression. A scaled model of a vertical tail of F/A-18 is developed in which piezoelectric actuators are bounded to the surface. The frequency response function (FRF) of the system is then recorded and maximization of the FRF peaks is considered as the objective function of the optimization algorithm to enhance the actuator authority on the mode, which assigns the optimal placement of the pair of piezoelectric actuators on the smart fin. Six multi-layer perceptron neural networks are employed to perform surface fitting to the discrete data generated by the finite element method (FEM). Invasive weed optimization (IWO), a novel numerical stochastic optimization algorithm, is then employed to maximize the FRF peak which in due reduces the vibration of the smart fin. Results indicated an accurate surface fitting for the FRF peak data as well as the optimal placement of the piezoelectric actuators for vibration suppression.

능동음향진동제어를 위한 센서와 액추에이터의 동위치화 연구

The problem considered in this paper is about the collocation of sensor and actuator for the active control of sound and vibration. It is well-known that a point collocated sensor-actuator pair offers an unconditional stability with very high performance when it is used with a direct velocity feedback (DVFB) control, because the pair has strictly positive real (SPR) property. In order to utilize this SPR characteristics, a matched piezoelectric sensor and actuator pair is considered. but this pair suffers from the in-plane motion coupling problem with the out-of-plane motion due to the piezo sensor and actuator interaction. This coupling phnomenon limits the stability and performance of the matched pair with DVFBcontrol. As a new alternative, a point sensor and distributed piezoelectric actuator pair is also considered, which provides SPR property in all frequency range when the pair is implemented on a clamped-clapmed beam. The use of this sensor-actuator pair is highly expected for the applications to more practical active control of sound and vibration systems with the DVFB control strategy.

Robust design of piezoelectric actuators for structural control

A robust design methodology is presented for the control of flexible structures by the use of piezoelectric actuators. The finite element modeling and analysis of the piezoelectric media are carried out via Hamilton's principle. Finite element equations are utilized for the piezoelectric control of flexible structures subject to dynamic disturbances. Various configurations of piezoelectric actuator pairs mounted on cantilever beam structures are considered for illustration purposes. The dimensions as well as the locations of the actuator pairs are assumed to be design variables varying within certain limits. Taguchi methodology is employed to these piezoelectrically controlled structures as a robust design technique in order to investigate the effects of the design variables on the control performance. Within the ranges considered in this study, it is concluded that the piezoelectric actuator pairs with larger sizes usually perform better in attenuating the structural vibrations. For the actuator pair location, the actuator pairs close to the fixed end result in better performance characteristics.

ACTIVE POSITION CONTROL OF A FLEXIBLE SMART BEAM USING INTERNAL MODEL CONTROL

The problem of controlling the position at the tip of a flexible cantilever beam to follow a command signal is considered, by using a pair of piezoelectric actuators at the clamped end. The beam is lightly damped and so the natural transient response is rather long, and also since the sensor and actuator are not collocated, the plant response is non-minimum phase. Two control strategies were investigated. The first involved conventional PID control in which the feedback gains were adjusted to give the fastest closed-loop response to a step input. The second control strategy was based on an internal model control (IMC) architecture. The control filter in the IMC controller was a digital FIR device designed to minimize the expectation of the mean square tracking error. In practice, such smart beams could be exposed to temperature fluctuations and changes in geometry. The effect of these variations on the stability was studied and it is shown that the need for robustness to such variations leads to a limitation in the performance of an IMC controller. The improvement in the stability robustness by incorporating control effort weighting into the cost function being minimized was investigated, as was the incorporation of modelling delay in the design of the IMC control filter. The IMC controller designed for the beam was found to have much reduced settling times to a step input compared with those of the PID controller while maintaining good robustness to changes in temperature. However, the extremely low damping of the experimental beam made it difficult to implement an accurate plant model in practice.