Piezocomposite Actuators Research Articles

Aerodynamic Modeling and Design Optimization of a Variable-Camber Piezocomposite Rotor

Multirotor vehicles typically use either complex mechanisms to vary blade pitch angle or speed control to vary thrust and torque to attain stability and maneuverability. Alternatively, thrust and torque can be varied by morphing the blades without the use of complex mechanisms and without varying the rotor speed. This method could be faster to change thrust, more efficient, and it may require fewer mechanical components. This paper presents an experimentally validated aerodynamic model with an empirical static-aeroelastic correction to predict the thrust and torque coefficient of a mechanism-free rotor with Macro-Fiber Composite actuators. A variable-camber piezocomposite rotor prototype is experimentally tested on a static-thrust setup. The experiment is used to identify the so-called unknown coefficients of the model (e.g., related to the shape of the blade induced by the piezoelectric device) and to identify a correction to account for flow-induced deformations. Using the identified model, several parametric analyses are conducted to predict thrust and torque coefficients as a function of rotor speed and the electrical excitation of the piezocomposite actuators. In addition, the model is used for design optimization, leading to several optimal designs based on a limited parameter space. Three different objective functions are used: maximizing thrust, minimizing torque, and maximizing thrust-to-torque ratio. The operational aerodynamic characteristics of these designs are also presented.

Low-Frequency ultrasonic tomography of Corrosion-induced damage patterns on naturally corroded solid reinforcing bar rock bolts

A combined non-destructive guided ultrasonic wave measuring approach and low-frequency ultrasonic tomography technique on cylindrical surfaces is developed to investigate corrosion-induced damage patterns in naturally corroded 60-year-old solid rebars. The main goal of low-frequency tomographic imaging simulations is for differential detection of general and localized pitting corrosions on cylindrical surfaces of solid steel bars. The modified damage probabilistic reconstruction algorithm for cylindrical surfaces is also adopted to simulate naturally general and localized pitting corrosion patterns. To increase the ray density or resolution of images, a regular array of accelerometer sensors with high-density spatial distributions around the cylindrical surface of steel bars is installed for a fixed piezocomposite actuator. As such, an efficient sensor deployment method can be applied with the trilateration technique to achieve effective coverage and connectivity properties between accelerometer sensors. Stochastic signal processing which is elicited from the Hilbert-Huang Transform (HHT) signal method is also employed to analysis low-frequency tomography time domain algorithms. Finally, optical surface profilometry approaches, and static state tensile testings, together with scanning electron microscopy (SEM) are adopted to confirm the effectiveness of non-destructive and tomography imaging techniques. The results show that the guided wave signals with excitation frequency of less than 10 kHz can be precisely employed to identify the general and localized pitting corrosion distributions on the cylindrical surfaces of steel bars and qualitatively reconstruct them using low-frequency ultrasonic tomography simulations. This research study also demonstrates that the low-frequency ultrasonic tomography simulations can be effectively applied in corrosion pattern uncertainty modelling.

Modeling and Flight Control of Small UAV with Active Morphing Wings

In recent research works, morphing wings were studied as an interesting field for a small unmanned aerial vehicle (UAV). The previous studies either focused on selecting suitable material for the morphing wings or performing experimental tests on UAVs with morphing wings. Though, the dynamic modeling of active flexible morphing wings and their involved interactions with the aerodynamics of the UAV body are challenging subjects. Using such a model to control a small UAV to perform specific maneuvering is not investigated yet. The dynamic model of UAV with active morphing wings generates a multi-input multi-output (MIMO) system which rises the difficulty of the control system design. In this paper, the aeroelastic dynamic model of morphing wing activated by piezocomposite actuators is established using the finite element method and modal decomposition technique. Then, the dynamic model of the UAV is developed taking into consideration the coupling between the wing and piezocomposite actuators, as well as the dynamic properties of the morphing actuators with the aerodynamic wind disturbances. A model predictive control (MPC) is designed for the MIMO control system to perform specific flight maneuvering by tracking desired trajectories of UAV altitude and yaw angle. Additionally, the MPC achieves constrained behavior of pitch and roll angles to get satisfactory UAV motion. Also, the behaviors of the UAV control system using MPC are evaluated after adding Dryden wind turbulence to the UAV outputs. Finally, a UAV flight simulation is conducted which shows that the control system successfully rejects the applied disturbances and tracks the reference trajectories with acceptable behavior of pitch and roll angles.

HYIMFO: Hybrid method for optimizing fiber orientation angles in laminated piezocomposite actuators

Numerous engineering applications employ composite materials due to the advantages that the combination of their components can provide. Fiber-reinforced composites are a particular group of composites which allows designing optimized structures by tailoring the orientation of the fiber. For this reason, new additive manufacturing technologies have been developed nowadays. These tools allow the manufacturing of fiber-reinforced structures designed by using optimization algorithms. Consequently, there are several works in recent literature determining the optimized fiber orientation in composite structures, where the methods based on gradient stand out due to their better efficiency. There are two main approaches to determine the fiber orientation by using gradient-based methods, Continuous Fiber Angle Optimization (CFAO), where the angle is the design variable and commonly present local minima problems, and Discrete Fiber Angle Interpolation Models, which consider candidate angles a priori and by using weighting functions choose one of them as the optimized angle. This work proposes a method named HYMFO, which uses a combination of both approaches. To verify the efficiency of the method, two design problems of Laminated Piezocomposite Actuators (LAPA) are solved by using several mesh discretizations with the discrete methods DMO, HPDMO, BCP, and NDFO, the continuous method SPIMFO and the newly proposed hybrid method. Therefore, the method is not evaluated with the traditional problem of maximizing the stiffness in structural design. A new fiber orthogonality regularization is presented, facilitating the appearance of continuous paths in fiber distribution by imposing a specified maximum angle between adjacent fibers. A comparative analysis based on the performance of the structure and the computational cost is carried out to determine the most appropriate method for each situation.

Flutter Optimization of a Wing–Engine System with Passive and Active Control Approaches

In the present study, the flutter performance of a composite thin-walled beam wing–engine system is optimized by implementing two different control approaches: 1) passive open-loop and 2) active closed-loop control. Sequential quadratic programming and genetic algorithm methods are applied in the optimization process. In the passive control method, variable stiffness is acquired by constructing laminates of thin-walled beam with curvilinear fibers having prescribed paths. The goal is to exploit the desirable fiber paths with improved flutter performance to determine an optimized wing–engine aeroelastic configuration. In the active control strategy, piezo-composite actuators and the linear quadratic Gaussian algorithm are used to improve the flutter characteristics. A novel optimization strategy based on the total energy of the aeroelastic system is introduced and applied in both passive and active control strategies. The minimum total aeroelastic energy is an indication of ideal optimization variables, which leads to optimum flutter performance. The governing equations are formulated based on Librescu’s thin-walled beam theory and Hamilton’s principle. An unsteady aerodynamic model based on incompressible indicial aerodynamics is applied. The governing equations of motion are solved using a Ritz-based solution methodology. Numerical results demonstrate a 16 and 46% improvement in the flutter speed of the wing–engine system using the proposed passive and active control approaches, respectively. The presented results provide valuable information concerning the design of advanced lightweight and high-aspect-ratio aircraft wings with mounted engines in terms of favorable aeroelastic performance characteristics.

New Efficient Technique for Finite Element Modeling of Macro Fiber Composite Piezoelectric Materials

A lot of interest to simulate piezocomposite actuators with finite element method has been increased recently. However, there are still open questions regarding the modeling methodology, accuracy, and computational time cost. In this work, a new technique for modeling macro fiber composite piezoelectric actuator by finite element analysis is proposed. The presented technique models the piezocomposite actuator as a simple monolithic piezoceramic material with just two electrodes along its longitudinal extremes instead of using the actual large number of electrodes which results in very fine finite element mesh with high computational time cost. The proposed technique is validated successfully by comparing its results with those of the actual detailed model as well as with the published experimental results and manufacturer’s data.

Active flutter control of thin walled wing-engine system using piezoelectric actuators

In the present study, control of a Thin Walled Beam (TWB) wing-engine system is examined applying piezoelectric actuators to enhance the performance of aeroelastic response. The composite piezoelectric governing equations of motion including the structure and electric effects are derived applying Hamilton's principle. Piezoelectric composite plate equations are added to the composite host wing-engine governing system of equations. The incompressible aerodynamic model based on Wagner's function is applied and the Ritz based solution methodology is employed. As a passive control approach, the effects of piezoelectric fiber angles are studied on the time domain response of the high-aspect-ratio wing-engine system. The linear quadratic Gaussian (LQG) control algorithm is applied as a closed-loop active control strategy to enhance the flutter response characteristics of the composite wing-engine system. Numerical results firstly, demonstrate the effectiveness of the active control strategy based on piezocomposite actuator on suppressing the flutter response of the composite wing-engine system and secondly, prove the effect of piezocomposite actuator location and fiber angle orientation on the closed-loop control performance.

Optimization of Locations and Fiber Orientations of Piezocomposite Actuators on Flexible Wings for Aeroelastic Control

AbstractSmart piezoelectric fiber composite materials have the potential to improve the aerodynamic properties and aeroelastic responses of flexible wings. Aeroelastic control performance significa...

Active aeroelastic control of aircraft wings with piezo-composite

Active control of swept smart aircraft wings in an incompressible flow are examined. The wing structure is modeled as a composite thin-walled beam featuring fiber-reinforced host structure and piezo-composite actuators. The nonclassical effects, such as twist-bending elastic coupling, warping inhibition, transverse shear and rotatory inertia are incorporated. The unsteady incompressible aerodynamics are derived based on the concept of indicial functions, applicable to arbitrary small motion in the time domain. The influence of directionality property both of the host structure and piezo-actuators on improving aeroelastic performance are specifically investigated. The potential for active aeroelastic control via the actuation couplings due to the anisotropic piezoelectric properties is highlighted. A number of conclusions are outlined at the end.

Integrated design of laminated composite structures with piezocomposite actuators for active shape control

An integrated design approach of laminated composite structures actuated by piezocomposite materials is presented for active shape control. The primary purpose is to maximize static shape control authority of a piezo-actuated laminated plate by simultaneously optimizing the substrate laminates and the actuators. The design variables include thickness, ply angles of the substrate plate and locations, PZT fiber orientations of the actuators. Frequency constraints are implemented to obtain acceptable solutions. General genetic algorithm (GA) and NSGA-II are used to obtain the optimal designs. The results indicate that enhanced control authority must be achieved by simultaneously optimizing the substrate laminates and actuators. The bending-twisting coupling effect of the composites and anisotropic actuation effect of the piezocomposite actuators are conducive to produce improved static control performance. More shape control authority is available due to the presence of more actuators. Larger deformation can be produced with a low mass of the host composites without constraints but the structure would be too flexible. A series of Prato-optimal results can be obtained by considering trade-off between shape control authority and mass of the whole structure while considering constraints. Reasonable, practical designs can be obtained by imposing frequency constraints in the integrated design.

Optimized dynamic design of laminated piezocomposite multi-entry actuators considering fiber orientation

Laminated piezocomposite actuators (LAPA) are structures composed of piezoelectric and non-piezoelectric materials layers. Due to several parameters and the multiphysics domain involved in the design of LAPA, simple forms are commonly found in industrial applications. However, its design can be systematized by using the topology optimization method (TOM) that permits the solution of complex problems. The design of LAPA with TOM has traditionally considered the optimization of piezoelectric materials over an isotropic substrate, yet some previous researches suggest that LAPA including fiber-reinforced composite layers can increase the performance of these transducers. In addition, works dealing with fiber-based composite focus on static or harmonic analysis with sinusoidal excitations, although other signal inputs are used in practice. In fact, the design of fiber-based LAPA in transient regime has not been assessed before. Thus, a methodology is proposed here to design LAPA with TOM. The actuator is electrically excited with a combined waveform: a sine wave treated as a harmonic problem and a step excitation addressed as a transient problem. Both waves have the same frequency, however they are not applied at the same time. This approach allows the development of a multi-entry actuator since it generates the same level of output displacement independently of the type of excitation input. Consequently, the optimization problem is formulated with the purpose of distributing the material in all layers, the polarization sign in piezoelectric layers and the fiber orientation angle in composite layers, in which the objective function simultaneously seeks for the maximization of the vibration amplitude at certain points of the actuator and its response speed. Eight-node shell elements taking into account the piezoelectric effects are used in the finite element method (FEM) and the “layer wise theory is adopted to model the laminated structure. The Generalized-α method is used to solve the transient problem. In order to optimize the material distribution and the polarization sign, the classical SIMP and PEMAP-P models are used respectively, while to optimize the fiber orientation angles in the composite material, a novel self-penalizable interpolation model is proposed. This optimization problem is solved by using the sequential linear programming (SLP) technique with the CVX solver and the sensitivity analysis is performed with the adjoint method. Discrete signal processing concepts are applied to solve the adjoint problem involving specific points of curves obtained by time integration methods in transient analysis. Numerical techniques are implemented to avoid TOM instabilities. Finally, the potential of this approach is demonstrated with two numerical examples.

Feedback tracking control for dynamic morphing of piezocomposite actuated flexible wings

Aerodynamic properties of flexible wings can be improved via shape morphing using piezocomposite materials. Dynamic shape control of flexible wings is investigated in this study by considering the interactions between structural dynamics, unsteady aerodynamics and piezo-actuations. A novel antisymmetric angle-ply bimorph configuration of piezocomposite actuators is presented to realize coupled bending-torsional shape control. The active aeroelastic model is derived using finite element method and Theodorsen unsteady aerodynamic loads. A time-varying linear quadratic Gaussian (LQG) tracking control system is designed to enhance aerodynamic lift with pre-defined trajectories. Proof-of-concept simulations of static and dynamic shape control are presented for a scaled high-aspect-ratio wing model. Vibrations of the wing and fluctuations in aerodynamic forces are caused by using the static voltages directly in dynamic shape control. The lift response has tracked the trajectories well with favorable dynamic morphing performance via feedback tracking control.

Optimal unimorph and bimorph configurations of piezocomposite actuators for bending and twisting vibration control of plate structures

Optimal configuration of anisotropic piezocomposite actuators is investigated for vibration control of flexible structures. Actuation effects of the actuators in unimorph and antisymmetric angle-pl...

Modeling and Design of a Full-Scale Rotor Blade with Embedded Piezocomposite Actuators

An optimization methodology for the design of a full-scale rotor blade with an active twist in order to enhance its ability to reduce vibrations and noise is presented. It is based on a 3D finite-element model, the planning of experiments, and the response surface technique to obtain high piezoelectric actuation forces and displacements with a minimum actuator weight and energy applied. To investigate an active twist of the helicopter rotor blade, a structural static analysis using a 3D finite-element model was carried out. Optimum results were obtained at two possible applications of macrofiber composite actuators. The torsion angle found from the finite-element simulation of helicopter rotor blades was successfully validated by its experimental values, which confirmed the modeling accuracy.

Stiffness control of cylindrical shells under axial compression using piezocomposite actuators—An experimental investigation

ABSTRACTThe present study explores the modification and control of prebuckling stiffness of cylindrical shells for their potential use in smart structures. The effects of surface-bonded microfiber composite actuator patches on cylindrical shells subjected to axial compression are studied experimentally. The actuators are placed such that the distance separating them is less than the observed axial and circumferential buckling wavelengths. Strain gauge sensors are used to measure the axial strains at discrete locations on the cylindrical shell. Experimental results indicate that the actuation effect can reduce the local strains as well as improve the overall stiffness of the structure. The results obtained in this study potentially have a significant impact in space applications.

Experimental study on control fins of a small flying vehicle using piezo-composite actuators

A camber morphing control fin design and an all-moving control fin design using piezo-composite unimorph actuators are presented in this paper. The control fin of a small flying object is usually actuated using a servo motor system with an electromagnetic motor. Much research has been conducted to solve the structural complexity of servo actuation systems to convert the rotation of a servo motor to a linear actuation motion. To simplify this structural complexity, several types of smart actuators have been developed, such as bimorph or unimorph actuators with piezoelectric material layers and shape memory alloy actuators. In this study, a camber morphing type control fin and an all-moving type control fin actuated using piezo-composite actuators are designed to evaluate their ability to simplify the structural complexity of the gear transmission and electromagnetic servo motor system or hydraulic actuator system. Within the skin of the control fin, a piezo-composite actuator is mounted and the other end inserted in a slot of the control fin. As the piezo-composite actuator is excited by an electric field, the pitch angle of the control fin is changed. Experimental testing for the pitch rotation angle of a control fin in a 450 V electric field showed the deflection angle of the camber morphing control fin was 1.4° and the rotational angle of the all-moving control fin was 5.4°, which is obtained from the rotation angle magnification linkage structural system.

Modelling and investigation of a piezo composite actuator application

This work presents a proposal of modelling and investigation of advanced piezo composite MFC actuator application in one–dimensional flexural vibrating systems. The presented method of analysis of the considered system is based on the discrete–continuous mathematical model and the approximate Galerkin method. Characteristic YV that describes relation between the beam's deflection and applied voltage was calculated. The next step of the work was the analysis of influence of the piezoelectric macro fibre composite's properties on the obtained characteristic of the system. The main aim of this work is to propose a mathematical algorithm of the process of modelling and analysis of systems under consideration that can be very useful in designing process. Obtained results can be used to optimise designed systems for example by selecting geometrical and material parameters of the systems elements including the glue layer between the transducer and mechanical subsystem.

Integrated Localized MicroCooling Using High-Displacement Piezoelectric Actuators

RF communication and radar systems present an extreme thermal management challenge. These systems are comprised of tightly packaged, high-power components requiring a controlled temperature to meet performance and reliability parameters. In these systems, there is little space available for macro-scale air flow or other traditional cooling methods. In addition, heat generating components are typically microscale semiconductor devices fabricated on integrated circuit substrates buried deeply within the system. Localized cooling using integrated microsystems may provide a solution to these thermal management issues. One approach is the integration of miniature synthetic air jets near the heat generating components. Synthetic jets are generated using oscillating piezoelectric actuators that force air through a small nozzle at high flow rates and in close proximity to the heat generating component. The resulting jets provide vorticity within the fluid, leading to enhanced mixing with the surrounding lower temperature environment and a subsequent increase in the heat transfer coefficient. The US Army AMRDEC has been developing and operating microactuator test beds, utilizing high-displacement actuator architectures, including THUNDER and Lightweight Piezo-Composite Actuator (LIPCA) approaches, to reduce actuator size while maintaining sufficient flow rates and vorticity. This investigation has modeled and fabricated potential high-displacement miniature actuators, as well as predicted and characterized resulting jet parameters and heat transfer coefficients utilizing these actuators. This paper will present actuator designs, fabrication process, and cooling results using these high-displacement piezoelectric actuators as the drive element.

Increment thrust of fish robot by using Compressed Unimorth Piezoelectric Composite Actuator

In this work, we have presented a fish robot actuated by four compressed light-weight piezo-composite actuators. Swimming speed, thrust, and drag of the fish robot were experimentally examined to verify effect of the applied compressive force on force actuation, consequently on swimming speed of fish robot. The swimming speed of the fish robot was measured for four different tail fin areas. The drag of the fish robot was estimated by experiment and computational fluid dynamics (CFD) simulation. For drag measurement, we have presented an apparatus to measure relatively small drag by using a high speed camera. The measured drag agreed well with the calculated one by the CFD. We have also suggested a thrust measurement apparatus, where we can ignore effect of vibratory motion of the system. The thrust of the fish robot was increased about 11% due to the applied compressive force on the piezoceramic actuators. However, the drag of the fish robot was also increased due to increment of the cross section area.

소형 무인 비행체 조종면 작동용 압전 복합재료 작동기 연구

본 논문은 기존의 유/공압 및 전기식 모터를 대체할 수 있는 경량, 고성능 지능소자 구동기를 설계/제작하고 이를 소형 무인비행체의 조종익 시스템에 적용 가능성을 연구한 것이다. 또한 압전 복합재료 작동기에 대한 성능평가를 수행하였으며, 유니모프 및 바이모프 형태의 작동기를 제작하여 각각의 작동 특성을 확인하였다. 이와 같은 성능시험 평과 결과를 통해 바이모프 형태의 작동기가 하중 유무와 무관하게 선형적인 받음각 변화를 가짐을 알 수 있었다. 이러한 지능소자 구동 시스템은 소형 로봇, 유도무기 및 MAV, UAV의 조종익 제어 시스템으로 사용될 수 있는 가능성을 확인하였다. The purpose of the present study is to develop lightweight and simple smart actuators in order to replace conventional hydraulic/pneumatic actuators, and to apply the developed actuators to the actuation systems of a small unmanned air vehicle. This research describes the procedures of design, manufacturing of the piezo-composite actuator, and the performance evaluation. From the test results of the developed devices, we found the possibility of piezo-composite actuator could be used as a control surface of a small UAV system. We have designed and manufactured two kinds of piezo-composite actuators, unimorph actuator and bimorph actuator. The manufactured actuators were evaluated through the performance testes. It was found that the bimorph type actuator showed more linear angle change for the same excitation voltage variation than unimorph type. It is expected that piezo-composite actuator has a possibility to be used not only as a control surface of small unmanned flying vehicle but also as a control surface actuator of a guided missile fin through the miniaturization of power supply and control system.