Shape memory polymer (SMP) is one of smart polymers which exhibit shape memory effect upon external stimuli. Reinforcements as carbon fiber had been used for making shape memory polymer composite (CF-SMPC). This study investigated a possibility of designing self-deployable structures in harsh space condition using CF-SMPCs and analyzed their shape memory behaviors with constitutive equation model.CF-SMPCs were prepared using woven carbon fabrics and a thermoset epoxy based SMP to obtain their basic mechanical properties including actuation in harsh environment. The mechanical and shape memory properties of SMP and CF-SMPCs were characterized using dynamic mechanical analysis (DMA) and universal tensile machine (UTM) with an environmental chamber. The mechanical properties such as flexural strength and tensile strength of SMP and CF-SMPC were measured with simple tensile/bending test and time dependent shape memory behavior was characterized with designed shape memory bending test. For mechanical analysis of CF-SMPCs, a 3D constitutive equation of SMP, which had been developed using multiplicative decomposition of the deformation gradient and shape memory strains, was used with material parameters determined from CF-SMPCs. Carbon fibers in composites reinforced tensile and flexural strength of SMP and acted as strong elastic springs in rheology based equation models. The actuation behavior of SMP matrix and CF-SMPCs was then simulated as 3D shape memory bending cases. Fiber bundle property was imbued with shell model for more precise analysis and it would be used for prediction of deploying behavior in self-deployable hinge structure.
Recently, piezocomposite generating elements (PCGEs) have been proposed for improving the electricity generation
performance of piezoceramic wafers. The residual stress in the PZT layer after curing is one of the main reasons for
PCGE's enhanced performance, and the outer epoxy-based composites protect the brittle PZT layer. In this work, we
propose a d33-mode PCGE that can be used for energy harvesting. The piezoelectric coefficient d33 of the generating
element was used as a measure of the electricity generating performance. We fabricated several PCGEs and conducted
energy harvesting experiments to verify the concept of the d33-mode coefficient of generating element.
We introduce a design for a magnetic force exciter that applies vibration to a piezo-composite generating element
(PCGE) for a small-scale windmill to convert wind energy into electrical energy. The windmill can be used to harvest
wind energy in urban regions. The magnetic force exciter consists of exciting magnets attached to the device's input
rotor, and a secondary magnet that is fixed at the tip of the PCGE. Under an applied wind force, the input rotor rotates to
create a magnetic force interaction to excite the PCGE. Deformation of the PCGE enables it to generate the electric
power. Experiments were performed to test power generation and battery charging capabilities. In a battery charging test,
the charging time for a 40 mAh battery is approximately 1.5 hours for a wind speed of 2.5 m/s. Our experimental results
show that the prototype can harvest energy in urban areas with low wind speeds, and convert the wasted wind energy
into electricity for city use.
Energy can be reclaimed and stored for later use to recharge a battery or power a device through a process called energy
harvesting. Piezoelectric is being widely investigated for use in harvesting surrounding energy sources such as sun,
wind, tides, indoor lighting, body movement or machine vibration, etc. This paper introduces a wind energy harvesting
device using a Piezo-Composite Generating Element (PCGE). The PCGE is composed of layers of carbon/epoxy, PZT
ceramic, and glass/epoxy cured at an elevated temperature. In the prototype, The PCGE performs as a secondary beam
element. One end of the PCGE is attached on the frame of the device. The fan blade rotates in the direction of the wind and hits the PCGE's tip. When the PCGE is excited, the effects of the beam deformation allow it to generate electric power. In wind tunnel experiments, the PCGE is excited to vibrate at its first natural frequency and generates the power up to 8.5 mW. The prototype can harvest energy in urban regions with minor wind movement.
We have studied a biomimetic swimmer inspired by the motility mechanisms of bacteria such as E. coli theoretically and
experimentally. Even though E. coli uses one or several rotating helical filaments to swim, a single rotating helical
filament swimmer is considered in this work. The performance of this swimmer was estimated by modeling the dynamics of a swimmer in viscous fluid. The model has an ellipsoidal cell body propelled by a helical filament. We applied the resistive force theory on this model to calculate the linear swimming speed and the efficiency of the model. A parametric study on the swimming velocity was performed. To validate the theoretical results, a biomimetic swimmer was fabricated and an experiment setup was prepared to measure the swimming speed in silicone oil. In addition, we have studied the flow patterns surrounding the filament with a finite element simulation to understand the mechanism of propulsion.
The purpose of this study is improvement of a fish robot actuated by four light-weight piezocomposite actuators
(LIPCAs). In the fish robot, we developed a new actuation mechanism working without any gear and thus the actuation
mechanism was simple in fabrication. By using the new actuation mechanism, cross section of the fish robot became 30%
smaller than that of the previous model. Performance tests of the fish robot in water were carried out to measure tail-beat
angle, thrust force, swimming speed and turning radius for tail-beat frequencies from 1Hz to 5Hz. The maximum swimming
speed of the fish robot was 7.7 cm/s at 3.9Hz tail-beat frequency. Turning experiment showed that swimming direction
of the fish robot could be controlled with 0.41 m turning radius by controlling tail-beat angle.
This paper describes an approach to increase the flapping frequency of a previously developed flapper actuated by Lightweight Piezo-
Composite Actuator (LIPCA) to mimic the flapping frequency of Allomyrina Dichotoma of which flapping frequency is typically
30Hz. To achieve this purpose, the dynamic characteristics of the LIPCA and modification of a four-bar linkage have been studied.
The parametric study showed that an appropriate combination of linkage lengths can provide a better moment transmission for a given
flapping angle amplification, thus the flapping frequency could be increased. A newly designed four-bar linkage system was
fabricated based on the parametric study and then tested to verify the possibility. The test results showed that the optimal flapping
frequency of the modified flapper was measured to be about 15 Hz, which is about 50% increases compared to that of the previous
flapper. The modified flapper could also produce 3.02 gram force in vertical direction with 97 degree of flapping angle at the optimal
frequency.
KEYWORDS: Digital image correlation, Scanning electron microscopy, Electron microscopes, Veins, Cameras, 3D metrology, Natural surfaces, Composites, 3D image processing, CCD cameras
In the present study, a digital image correlation method has been applied to measure the elastic modulus of a beetle wing
membrane. Specimens were prepared by cutting beetle wing carefully with a size of 3.0 mm in width and 5.0 mm in
length. We used a scanning electron microscope for exactly measuring the membrane thickness of a beetle wing
membrane. The specimen was attached to a designed fixture to induce a uniform displacement using a micromanipulator.
We measured the applied load and the corresponding displacement by a load cell with a maximum capacity of 5 N and
by an ARAMIS system based on the digital image correlation method respectively. The measured thickness of a beetle
wing varied from point to point of the wing part and the elastic modulus was different according to the loading direction.
In conclusion, we successfully measured the elastic modulus of a beetle wing with an ARAMIS system based on the
digital image correlation method.
Nowadays active vibration suppression of flexible manipulators is important in many engineering applications, such as
robot manipulators and high-speed flexible mechanisms. The demand for short settling time and low energy
consumption of the vibration suppression has necessitated the consideration to optimal control. For a wide range of
operating conditions, the fixed optimal parameters determined for a control algorithm might not produce the highest
performance. Hence, a self-tuning optimal control method for a flexible manipulator should be used to enhance the
performance. This method can tune itself to the optimal parameters on the basis of the initial maximum responses of the
controlled system. In this study, the multi-objective genetic algorithm is used to search for optimal parameters with
regard to positive position feedback, thereby minimizing the settling time and energy consumption multi-objective
functions. The experimental results reveal that the energy consumption can be reduced significantly while the settling
time is still slightly increased.
We have analyzed and experimentally examined the flapping performances in terms of aerodynamic force generation,
flapping frequency and flapping angle of the two flappers actuated by the original LIPCA and the compressed LIPCA,
respectively. The flapping tests for two wing shapes were conducted at three different wing rotation angles and various
flapping frequencies to search for the optimum flapping frequency, at which the maximum aerodynamic force was
achieved, and investigate the effect of wing shape and wing rotation angle on the force generation of the flapper. The
aerodynamic forces were calculated by subtracting the inertia forces measured in the vacuum from the total forces
measured in the air. For the CFD simulation, we established the corresponding kinematical equations of the wing by
examining the high-speed camera images taken from front and top at the same time. The experimental results showed we
could improve the flapping angle 18.2 % and the average vertical aerodynamic force 24.5 % by using the compressed
LIPCA.
In this study, a high performance peristaltic micropump has been developed and investigated. The micropump has three
cylinder chambers which are connected through micro-channels for high pumping pressure performance. A circular-shaped
mini LIPCA has been designed and manufactured for actuating diaphragm. In this LIPCA, a 0.1mm thickness
PZT ceramic is used as an active layer. As a result, the actuator has shown to produce large out of plane deflection and
consumed low power. During the design process, a coupled field analysis was conducted to predict the actuating
behavior of a diaphragm and pumping performance. MEMS technique was used to fabricate the peristaltic micropump.
Pumping performance of the present micropump was investigated both numerically and experimentally. The present
peristaltic micropump was shown to have higher performance than the same kind of micropump developed else where.
This paper presents an experiment and parametric study of a biomimetic fish robot actuated by the Lightweight Piezocomposite
Actuator (LIPCA). The biomimetic aspects in this work are the oscillating tail beat motion and shape of
caudal fin. Caudal fins that resemble fins of BCF (Body and Caudal Fin) mode fish were made in order to perform
parametric study concerning the effect of caudal fin characteristics on thrust production at an operating frequency range.
The observed caudal fin characteristics are the shape, stiffness, area, and aspect ratio. It is found that a high aspect ratio
caudal fin contributes to high swimming speed. The robotic fish propelled by artificial caudal fins shaped after
thunniform-fish and mackerel caudal fins, which have relatively high aspect ratio, produced swimming speed as high as
2.364 cm/s and 2.519 cm/s, respectively, for a 300 Vp-p input voltage excited at 0.9 Hz. Thrust performance of the
biomimetic fish robot is examined by calculating Strouhal number, Froude number, Reynolds number, and power
consumption.
Currently a carbon/glass fiber, piezoelectric-ceramic composite, LIPCA, is being investigated for use in micro
aerial vehicles, micropumps, vibration control systems, and a number of bio-inspired robotic devices. Many of these
applications help demonstrate the growing trend in miniaturization that drives innovative developments in products
ranging from pacemakers to cell phones. When designing products for our ever shrinking world not only must the size of
the principal components of the system be taken into consideration but also the components of the system that afford
functionality as a bi-product of their inclusion. To this end we are referring to the mechanical or electrical systems that
provide these devices with the necessary energy to perform their tasks. In order to make efficient use of LIPCA in the
previously mentioned applications, the ability to forecast power consumption is essential. In the present investigation, a
method of modeling the power consumption of piezoelectric devices is presented and evaluated over a range of
frequencies and voltages. Effects of variation in actuator dimension, driving voltage, and frequency are presented.
Accuracy of the model is assessed and factors leading to inaccuracies are identified.
In this paper, the pumping performance of a piezoelectric micropump is simulated with the commercial finite element
analysis software COMSOL Multiphysics 3.2a. The micropump, which was developed in our previous work, is
composed of a four-layer lightweight piezocomposite actuator, a polydimethylsiloxane (PDMS) pump chamber, and two
diffusers. The piezoelectric domain, the structural domain and the fluid domain are coupled in the simulation. The water
flow rates are numerically predicted for geometric parameters of the micropump. This study confirms that the micropump is optimally designed to obtain its maximum pumping performance.
In this study, the actuation displacement and blocking force of the LIPCA (Lightweight Piezo-Composite Actuator)
under various combination of the external compressive load and prescribed voltage have been numerically and
experimentally examined. For numerical analysis, the full three-dimensional model of the LIPCA including two end-tabs
in the simply supported configuration was used and the measured nonlinear behavior of the bare piezoceramic wafer
(3203HD, CTS) was implemented in the geometrically nonlinear finite element analysis. The central out-of-plane
displacement of the LIPCA was measured while applying various electric fields and compressive loads at the same time.
Dummy weights were added at the center of the LIPCA until the LIPCA cannot produce additional central actuation
displacement for a given excitation voltage and the sum of the dummy weight was regarded as the blocking force. The
numerical results acquired by geometrical/material nonlinear finite element analysis and the measured data showed a
good agreement even for high electric field and compressive load. The investigation showed that the actuation
displacement and blocking force of the LIPCA were significantly increased by pre-applied compressive load. At the
same electric field, the actuation displacements of the LIPCA under nearly buckling load could be about two times larger
than those without compressive load. The results also indicate that the positive voltage should be better applied to the
actuator than the negative voltage. Therefore, the high negative electric field, which causes the polarization switching in
the piezoceramic wafer, can be avoided in applications. At +150V, the blocking force of the compressed actuator under
near buckling load was also increased around 26% higher than that of the actuator without compressive load.
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.
This paper presents an improved version of the insect-mimicking flapping-wing mechanism actuated by LIPCA (Lightweight Piezo-Composite Actuator). As the previous version, the actuation displacement of the actuator is converted into flapping-wing motion by a mechanical linkage system that functioned as displacement amplifier as well. In order to provide feathering motion, the wing is attached to the axis through a hinge system that allows the wing rotation at each end of half-stroke, due to air resistance. In this improved version, the total weight has been reduced to the half of the previous one. The device could produce about 90 degree of flapping angle when it operated at around 10 Hz, which was the natural flapping-frequency. Several flapping tests under different parameter configurations were conducted in order to investigate the characteristic of the generated lift. In addition, the smoke-wire test was also conducted, so that the vortices around the wing can be visually observed. Even though the present wing has smaller wing area, it could produce higher lift then before.
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.
This paper presents the actuation performance of a conducting shape memory polyurethane (CSMPU) actuator. We introduced a concept of shape memory polyurethane activated by electric power in 2004, while conventional shape memory polyurethanes are activated by external heat source. A conducting shape memory polyurethane actuator was manufactured by adding carbon nano-tube to conventional shape memory polyurethane. The main problem of the previous CSMPU was bad dispersion of carbon nano-tubes in polyurethane. In this paper, we have tried to find manufacturing method to solve the dispersion problem. With a lot of elaborative works, we have developed conducting shape memory polyurethane actuator with good electrical performance. The actuation performance of the developed conducting shape memory polyurethane actuator was measured and assessed.
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.
We have tried to apply electroactive shape memory polymer to smart actuator. Electroactive shape memory can be achieved by applying an electric field to shape memory polymer without any thermal heating as conventional shape memory polymers. For it, electrically conducting shape memory composites were prepared by incorporating carbon nanotube into polymer matrix. A segmented polyurethane block copolymer composed of 4,4'-methylene bis (phenylisocyanate), polycaprolactone, and 1,4-butanediol was synthesized to be used as shape memory polymer, and carbon nanotube was used after surface-modification by an acid. It was found that nanotube-reinforced composites could show high electrical conductivity with increased modulus at only several weight percentages of nanotube, and electroactive shape recovery effect more than 80% could be obtained. Consequently, electric field-stimulated shape memory could be demonstrated through combined composites of polyurethane and nanotube.
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.
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.
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 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.
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.
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