In order to substitute a conventional fin operated by hydraulic actuators, a smart fin actuated by piezoelectric material was attempted. A straight unimorph actuator was embedded along the spanwise direction in the hollow inner space of the fin. A hinge which was constrained except the axial rotation was located at the 1/4th chord line, and this enabled the smart fin to rotate in its rigid pitch direction. In this paper, starting from the fundamental structural analysis, the aeroelastic and aeroservoelastic stability, and structural response simulations of the smart fin control system were performed by integration of MSC.NASTRAN, ZAERO and MATLAB/Simulink. The controller was designed to ensure the flight stability and to maintain the pitch angles of the smart fin under specific flight conditions. Closed-loop control system of the smart fin was constructed and analyzed by MATLAB/Simulink.
KEYWORDS: Actuators, Data modeling, Smart materials, Linear filtering, Signal processing, Control systems, Transformers, Autoregressive models, Analog electronics, Aerospace engineering
A smart material is known to be able to generate large force in broad bandwidth in a compact size. However it needs
relatively large voltage to drive it and this makes the system bulky. In this paper, first, we introduce an improved version
of miniaturized piezo actuator driver and modeling of the dynamics of the piezo actuator, LIPCA. ARX model was used
to model the dynamics of the LIPCA. We applied rectangular waves to the LIPCA and measured its responses with a
strain gauge and a signal processing circuit. A 5th order model was obtained from the input/output data and applying
identification algorithm. Secondly, we designed a simple PID controller based on the obtained model to improve the
characteristics of the LIPCA actuator.
This paper presents an experimental study to investigate the actuation performance of LIPCA (Lightweight Piezo-
Composite unimorph Actuator) with different loading cases. High value of the manufacturing-induced compressive
stress in PZT layer of LIPCA helps avoiding potential in-service failure, however, it may cause a reduction in strain due
to the induced piezoelectric effect. High compressive prestress makes the domains aligned and constrained
perpendicular to the stress direction. Consequently, fewer domains can be reoriented to contribute to polarization and
strain output. The unimorph actuator is thus designed and operated such that the compressive stress in piezoceramic
material is large enough to avoid failure in working condition but small enough to allow larger amount of non-180o
domain switching. To compensate the high designed compressive stress state in the piezoceramic attention should be
paid on the loading configuration when the actuator is working in-service condition. Experimental results show that the
actuator should be arranged in a manner such that the stress state within the PZT wafer is in as more tension as possible
to compensate the high compressive induced stress in the piezoceramic due to the manufacturing process.
In this study, we derive an analytical solution for the simply supported and multilayered unimorph piezoelectric composite actuator as a beam model under applied voltage and external mechanical loads. The obtained solutions based on Rayleigh-Ritz technique including thermal effect and piezo-mechanical coupling effect show their convenience in various problems with different loading and boundary conditions. The von-Karman nonlinear terms in strain-displacement relations is also taken into account in the model. As a numerical illustration, model of LIPCA-C3 (LIghtweight Piezo-Composite Actuator) is analyzed. The results are compared with finite element analysis and experiment ones. Discussion on the approach and suggestions for future research activities are also presented.
KEYWORDS: Actuators, Aerodynamics, Aerospace engineering, Finite element methods, Prototyping, Control systems, Ceramics, Active vibration control, Composites, Vehicle control
There have been persistent interests in high performance actuators suitable for the actuation of control surfaces of small aircraft and helicopter blades and for active vibration control of aerospace and submarine structures that need high specific force and displacement. What is really needed for active actuation is a large-displacement actuator with a compact source, i.e., much higher strain. A lot of effort has been made to develop compact actuators with large displacement at a high force. One of the representative actuator is LIPCA actuator that was introduced by Yoon et al. The LIPCA design offers the advantages to be applied as actuator for the small aerial vehicle comparing with any other actuators. The weight is one of the main concerns for aerospace field, and since LIPCA has lighter weight than any other piezo-actuator thus it is suitable as actuator for small aircraft control surface. In this paper, a conceptual design of LIPCA-actuated control surface is introduced. A finite element model was constructed and analyzed to predict the deflection angle of the control surface. The hinge moment that produced by the aerodynamic forces was calculated to determine the optimum position of the hinge point, which could produce the deflection as high as possible with reasonable hinge moment. To verify the prediction, a prototype of SUAV (small unmanned air vehicle) control surface was manufactured and tested both in static condition and in the wind tunnel. The prediction and test results showed a good agreement on the control surface deflection angle.
In this paper, we focus on improving the performance of the piezoelectric diaphragms of micropumps. A novel circular lightweight piezoelectric composite actuator (LIPCA) with a high level of displacement and output force has been developed for piezoelectrically actuated micropumps. The actuator was designed and fabricated with oxide-based piezoelectric material in combination with carbon/epoxy fabric and glass/epoxy fabric. We used numerical and experimental methods to analyze the characteristics of the actuator. In addition, we used the developed circular LIPCA in conjunction with polydimethylsiloxane (PDMS) material and PDMS molding techniques to design, model and fabricate a valveless micropump. We then used a circular LIPCA bonded to a thin layer of PDMS as an actuator diaphragm. The actuator diaphragm can provide a comparatively high level of displacement, about twice that of conventional piezoelectric diaphragms that are commonly used in micropumps. The displacement of the diaphragm, the flow rate and the backpressure of the micropump were evaluated and discussed. With water, the pump reaches a maximum flow rate of 1.3 ml/min and a maximum backpressure of 4.1 kPa. The test results confirm that the circular LIPCA is a promising candidate for micropump application and can be used as a substitute for a conventional piezoelectric actuator diaphragm.
In this paper, we present our recent progress in LIPCA (Lightweight Piezo-Composite Actuator) application for actuation of flapping wing device. The flapping device uses linkage system that can amplify the actuation displacement of LIPCA. The feathering mechanism is also designed and implemented such that the wing can rotate during flapping. The natural flapping-frequency of the device was 9 Hz, where the maximum flapping angle was reached. The flapping test under 4 Hz to 15 Hz flapping frequency was performed to investigate the flapping performance by measuring the produced lift and thrust. Maximum lift and thrust produced when the flapping device was actuated near the natural flapping-frequency.
In this paper, we present design, manufacturing, and wind tunnel test for a small-scale expandable morphing wing. The wing is separated into inner and outer wings as a typical bird wing. The part from leading edge of the wing chord is made of carbon composite strip and balsa. The remaining part is covered with curved thin carbon fiber composite mimicking wing feathers. The expandable wing is driven by a small DC motor, reduction gear, and fiber reinforced composite linkages. Rotation of the motor is switched to push-pull linear motion by a screw and the linear motion of the screw is transferred to linkages to create wing expansion and folding motions. The wing can change its aspect ratio from 4.7 to 8.5 in about 2 seconds and the speed can be controlled. Two LIPCAs (Lightweight Piezo-Composite Actuators) are attached under the inner wing section and activated on the expanded wing state to modify camber of the wing. In the wind tunnel test, change of lift, drag, and pitching moment during wing expansion have been investigated for various angles of attack. The LIPCA activation has created significant additional lift.
KEYWORDS: Ferroelectric materials, Actuators, Active vibration control, Control systems, Aluminum, Power supplies, Structural dynamics, Switching, Circuit switching, Data acquisition
This paper presents the application of Lightweight Piezo-composite Curved Actuator (LIPCA) to suppress vibration as actuator. LIPCA is composed of a piezoelectric layer, a carbon/epoxy layer and glass/epoxy layers. When compared to the bare piezoelectric ceramic (PZT), LIPCA has advantages such as high performance, durability and reliability. In this study, performances of LIPCA are estimated in an active vibration control system. Experiments are performed on an aluminum beam by cantilever configuration. In this test, strain gages and single LIPCA are attached on the aluminum beam with epoxy resin in order to investigate their performance. Comparison of actuation force between LIPCA and bare PZT showed that performance of LIPCA was better than that of bare PZT. In addition, digital on-off control algorithm is applied into the system to exhibit performance of LIPCA as actuator in active vibration control system. The results showed LIPCA could suppress free vibration of the aluminum beam. It is possible to apply LIPCA as actuator to control vibration of dynamic structures.
The current MAVs used servomotors as actuators for the control surfaces, such as elevators and rudders. In this paper, the application possibility of conducting shape memory polymer to smart actuator has been assessed. Our final goal will be to replace the servomotor with a newly developed conducting shape memory polymer actuator. As the first step, a conducting shape memory polymer with high transition temperature and high conductivity was manufactured and its properties were measured. Second, conceptual designs of special actuating systems for control surface of micro aerial vehicle are presented. The conducting shape memory polymer was composed of shape memory polyurethane block copolymer and carbon nanotube or carbon black. Its basic thermo-mechanical and conducting properties are discussed for application as electro-active shape memory polymer actuator.
In this paper, we present our recent progress in application of LIPCA (LIghtweight Piezo-Composite Actuator) to design and demonstration of a flapping wing device. The flapping device has flexible wings actuated by the LIPCA. The device is designed such that it can create twist motion during up- and down-stroke like bird or insect wings. The motion could be generated by using LIPCA actuator pivoted to the wing. The wing can bend and twist due to bending-twist coupling of the specially designed pivot system. Experimental results show that the properly designed flapping device powered by LIPCA can create anisotropic motion that is often required for producing effective thrust and lift forces in bird or insect flight.
In this paper, material nonlinear behavior of PZT wafer (3202HD, CTS) under high electric field and tensile stress is experimentally investigated and the nonlinearity of the PZT wafer is numerically simulated. In the simulation, new definitions of the piezoelectric constant and the incremental strain are proposed. Empirical functions that can represent the nonlinear behavior of the PZT wafer have been extracted based on the measured piezo-strain under stress. The functions are implemented in an incremental finite element formulation for material nonlinear analysis. With the new definition of the incremental piezo-strain, the measured nonlinear behavior of the PZT wafer has been accurately reproduced even for high electric field.
Biomimetic wing sections actuated by piezoceramics actuator LIPCA have been designed and their actuation displacements estimated by using the thermal analogy and MSC/NASTRAN based on the linear elasticity. The wing sections are fabricated as the design and tested for evaluation. Measured actuation displacements were larger than the estimated values mainly due to the material non-linearity of the PZT wafer. The biomimetic wing sections can be used for control surfaces of small scale UAVs.
This paper describes the development of biomimetic structure systems with LIPCA (LIghtweight Piezo-Composite Actuator) and battery supported power control unit. To apply LIPCA as a biomimetic actuator for the control surface of small unmanned air vehicle, a battery supported power control unit was developed, which is composed of a lithium polymer, one step-up converter, four power switching high voltage transistors, on Schmitt triggered comparator, and control logics. A simple RC circuit is used to sample the voltage applied to the LIPCA. H-switch was applied which is composed of the four high voltage transistors to control the voltage or charge and its polarity applied to the LIPCA. From experiments, it was observed that the developed biomimetic adaptronic systems could be constructed with relatively compact and light units and could produce enough displacement and force to be used as a control surface for the elevator and the rudder of a small unmanned vehicle.
This paper is concerned with the fatigue characteristics of LIPCA (LIghtweight Piezo-Composite Actuator) device systems, composed of a piezoelectric ceramic layer and fiber reinforced light composite layers, where the PZT ceramic layer is typically sandwiched by a top fiber layer with a low CTE (coefficient of thermal expansion) and base layers with a high CTE. The advantages of the LIPCA design include the use of lightweight fiber reinforced plastic layers without compromising the generation of a high force and large displacement, and design flexibility in selecting the fiber direction and size of the prepreg layers. In addition, a LIPCA device can be manufactured without adhesive layers since epoxy resin plays role of bonding material. To investigate the degradation of the actuation performance of LIPCAs due to repeated fatigue loading, repeated loading tests up to several million cycles were performed and the actuation displacement for a given excitation voltage measured during the test. The fatigue characteristics were measured using an actuator test system consisting of an actuator-supporting jig, high-voltage actuating power supplier, and non-contact laser measuring system and evaluated.
In the present work, the existing formulation of nine-node shell element based on Hellinger-Reissner principle is expanded for electro-mechanically coupled field analysis. The electro-mechanical coupling effect of the piezoelectric material is introduced to the formulation through the constitutive relation. Based on the formulation, a linear finite element code is constructed and it is validated by several numerical tests. By using the code, linear analysis of LIPCA(LIghtweight Piezoelectric Composite Actuator) is performed to calculate actuation displacement and stress. Moreover, to improve simulation result more accurately, an experimental piezo-strain function of PZT(3203HD, CTS) wafer that is embedded in LIPCA is obtained from measured data and the function is implemented into the code by adopting incremental method. And then, the actuation displacement of LIPCA is recalculated and the result is compared with the measured data.
KEYWORDS: Actuators, Ceramics, Ferroelectric materials, Manufacturing, Laser systems engineering, Semiconducting wafers, Design for manufacturability, Epoxies, Composites, Active vibration control
This paper is concerned with the performance evaluation and comparison for several kinds of LIPCA device system. LIPCA device system is composed of a piezoelectric ceramic layer and fiber reinforced light composite layers, typically a PZT ceramic layer is sandwiched by a top fiber layer with low CTE and base layers with high CTE. To investigate the effect of lay-up structure of the LIPCA system, four kinds of actuator with different lay-up stacking sequence have been designed, manufactured, and tested. The performance of each actuator was evaluated using an actuator test system consisted of an actuator supporting jig, a high voltage actuating power supplier, and a non-contact laser measuring system. From the comparison of the performance of the LIPCA prototypes, it was found that the actuator with larger actuation moment arm length and lower total flexural stiffness can generate larger actuating displacement.
This paper deals with a fully coupled assumed strain solid element that can be used for simultaneous moiling of thin sensors and actuators. To solve fully coupled field problems, electric potential is regarded as a nodal degree of freedom in addition to three translations in an eighteen node assumed strain solid element. Therefore, the induced electric potential can be calculated for a prescribed deformation or an applied load. Since the original assumed strain solid element is free of locking, the element can be used to analyze behavior of very thin actuators without locking. Numerical examples, such as a typical bimorph actuator/sensor beam problem shows that the present element can handle fully coupled problems. Using the solid element, we have analyzed the actuation performance of THUNDER and compared the result with measured data. The comparison shows that the numerical estimation agrees well with measured displacement for simply supported boundary condition. It is also found that a particular combination of materials for layers and curvature of THUNDER improve actuation displacement.
LIPCA (LIghtweight Piezo-composite Curved Actuator) is an actuator device which is lighter than other conventional piezoelectric ceramic type actuator. LIPCA is composed of a piezoelectric ceramic layer and fiber reinforced light composite layers, typically a PZT ceramic layer is sandwiched by a top fiber layer with low CTE (Coefficient of thermal expansion) and base layers with high CTE. LIPCA has curved shape like a typical THUNDER (Thin-layer composite unimorph ferroelectric driver and sensor), but it is lighter than THUNDER. Since the curved shape of LIPCA is from the thermal deformation during the manufacturing process of unsymmetrically laminated lay-up structure, and analysis for the thermal deformation and residual stresses induced during the manufacturing process is very important for an optimal design to increase the performance of LIPCA. To investigate the thermal deformation behavior and the induced residual stresses of LIPCA at room temperature, the curvatures of LIPCA were measured and compared with those predicted from the analysis using the classical lamination theory. A methodology is being studied to find an optimal stacking sequence and geometry of LIPCA to have larger specific actuating displacement and higher force. The residual stresses induced during the cooling process of the piezo- composite actuators have been calculated. A lay-up geometry for the PZT ceramic layer to have compression stress in the geometrical principal direction has been designed.
A numerical method for the performance evaluation of LIPCA actuators is proposed using a finite element method. Fully-coupled formulations for piezo-electric materials are introduced and eight-node incompatible elements used. After verifying the developed code, the behavior of LIPCA actuators is investigated.
This paper is concerned with design, manufacturing and performance test of lightweight THUNDER using a top fiber composite layer with near-zero CTE, a PZT ceramic wafer and a bottom glass/epoxy layer with high CTE. The main point of this design is to replace the heavy metal layers of THUNDER by the lightweight fiber reinforced plastic layers without losing capabilities to generate high force and displacement. It is possible to save weight up to about 30 percent if we replace the metallic backing materials by the light fiber composite layer. We can also have design flexibility by selecting the fiber direction and the size of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use epoxy resin prepreg system. Glass/epoxy prepregs, a ceramic wafer with electrode surfaces, and a graphite/epoxy prepreg were simply stacked and cured at an elevated temperature by following autoclave bagging process. It was found that the manufactured composite laminate device had a sufficient curvature after detaching form a flat mold. From experimental actuation tests, it was observed that the developed actuator could generate larger actuation displacement than THUNDER.
This paper is concerned with the viscoelastic strain-energy hinge for solar array deployment. The original strain-energy hinge proposed by TRW for solar array deployment was made of strip measures. Due to its structural simplicity, the strain-energy hinge has been considered as an alternative to the torsional spring type deployment mechanism. However, theoretical modeling of the strain-energy hinge is extremely difficult because of its nonlinear pre- and post-buckling dynamic behavior. To investigate its dynamic characteristics, series of buckling and deployment tests on a single strain-energy hinge and a solar array structure equipped with strain-energy hinge have been conducted. The deployment test results show that there remain residual vibrations after deployment, which are resulted from the rapid deployment and the bending flexibility of the strain- energy hinge. We propose the use of viscoelastic material embedded between the layers of the strip measure to increase the passive damping. It results in less residual vibrations and smooth deployment. Experimental results show that viscoelastic strain-energy hinge ins superior to the ordinary strain-energy hinge in deployments. Based on the experiments on the single strain-energy hinge, an equivalent 1D torsional spring model is proposed. Simulation results based on the equivalent model are fairly in good agreement with experimental results.
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