As micro-electromechanical systems (MEMS) and smart technologies have been more matured, applications for wider fields are more available. Piezoelectric materials have the property of electromechanical energy conversion, which can convert vibration energy into electrical energy. In this paper, a general concept of the piezoelectric energy conversion is first given. Then, a simple modeling design and analysis for a special transverse mode of the piezoelectric generator called mode 31 is presented. With regard to analytical method, the piezoelectric equivalent circuit model is able to illustrate the important parameters that influence the process how the piezoelectric element generates electrical energy. We may adjust unimorph voltage by controlling the deflection of cantilever beam. And the output power is taken as the indicated parameters for the generator. The energy conversion efficiency of the generator depends on the operation frequency. By using this way, the piezoelectric power generator may be widely applied to environment with both low-frequency and high-frequency vibration range.

Mechanical energy exists all over the place in our living, and vibration is the most common way of mechanical performance. Micro-electromechanical systems, the application which integrate techniques and combine different field of research, make it possible to convert vibration into electrical energy by using piezoelectric materials; moreover, it become a small piezoelectric power generator. The thesis set up an equivalent circuit model based on the principle of piezoelectric and cantilever mechanics for experimenting the model¡¦s exactness; consequently, model shows that resonant frequency has no effect on generate electricity when amplitude was fixed. The thesis attempts to change the shape of unimorph for enhancing its power generation. By using different sharp of unimorph, the experiment demonstrate that power generation have direct ratio with frequency at amplitude of 5mm. Moreover, different shapes of the unimorph at frequency of 16Hz have different power output; the disparity among power output might up to 1.78 times.

Piezoelectrics offer high actuation authority and sensing over a wide range of frequencies. A Macro-Fiber Composite is a type of piezoelectric device that offers structural flexibility and high actuation authority. A challenge with piezoelectric actuators is that they require high voltage input; however the low power consumption allows for relatively lightweight electronic components. Another challenge, for piezoelectric actuated aerodynamic surfaces, is found in operating a relatively compliant, thin structure (desirable for piezoceramic actuators) in situations where there are relatively high external (aerodynamic) forces. Establishing an aeroelastic configuration that is stiff enough to prevent flutter and divergence, but compliant enough to allow the range of available motion is the central challenge in developing a piezocomposite airfoil. The research proposed here is to analyze and implement novel electronic circuits and structural concepts that address these two challenges. Here, a detailed theoretical and experimental analysis of the aerodynamic and electromechanical systems that are necessary for a practical implementation of a piezocomposite airfoil is presented. First, the electromechanical response of Macro-Fiber Composite based unimorph and bimorph structures is analyzed. A distributed parameter electromechanical model is presented for interdigitated piezocomposite unimorph actuators. Necessary structural features that result in large electrically induced deformations are identified theoretically and verified experimentally. A novel, lightweight electrical circuitry is proposed and implemented to enable the peak-to-peak actuation of Macro-Fiber Composite bimorph devices with asymmetric voltage range. Next, two novel concepts of supporting the piezoelectric material are proposed to form two types of variable-camber aerodynamic surfaces. The first concept, a simply-supported thin bimorph airfoil, can take advantage of aerodynamic loads to reduce control input moments and increase control effectiveness. The structural boundary conditions of the design are optimized by solving a coupled fluid-structure interaction problem by using a structural finite element method and a panel method based on the potential flow theory for fluids. The second concept is a variable-camber thick airfoil with two cascading bimorphs and a compliant box mechanism. Using the structural and aerodynamic theoretical analysis, both variable-camber airfoil concepts are fabricated and successfully implemented on an experimental ducted-fan vehicle. A custom, fully automated low-speed wind tunnel and a load balance is designed and fabricated for experimental validation. The airfoils are evaluated in the wind tunnel for their two-dimensional lift and drag coefficients at low Reynolds number flow. The effects of piezoelectric hysteresis are identified. In addition to the shape control application, low Reynolds number flow control is examined using the cascading bimorph variable-camber airfoil. Unimorph type actuators are proposed for flow control in two unique concepts. Several electromechanical excitation modes are identified that result in the delay of laminar separation bubble and improvement of lift. Periodic excitation to the flow near the leading edge of the airfoil is used as the flow control method. The effects of amplitude, frequency and spanwise distribution of excitation are determined experimentally using the wind tunnel setup. Finally, the effects of piezoelectric hysteresis nonlinearity are identified for Macro-Fiber Composite bimorphs. The hysteresis is modeled for open-loop response using a phenomenological classical Preisach model. The classical Preisach model is capable of predicting the hysteresis observed in 1) two cantilevered bimorph beams, 2) the simply-supported thin airfoil, and 3) the cascading bimorph thick airfoil. / Ph. D.

Wireless sensors are an emerging technology that has the potential to revolutionize the monitoring of simple and complex physical systems. One of the biggest challenges with wireless sensors technology is power management and hence cost. A wireless sensor system incapable of managing its power consumption either by maintaining long battery life and/or harvesting from its surroundings, is simply not cost effective. Prolonging or eliminating the battery entirely would reduce the cost of battery replacement and maintenance. A viable family of materials for this purpose is piezoelectric materials because of their inherent ability to convert vibrations into electrical energy. Currently, a wide variety of piezoelectric materials are available and the appropriate choice for harvesting energy depends on their characteristics and properties. In addition to the material choice, energy harvesting circuitry is needed to efficiently convert and filter the signal from the piezoelectric device into a form that can be used by a load (battery). This thesis addresses the theoretical and experimental use of a type of pre-stressed PZT-5A Unimorph called a Thunder® to actively convert mechanical vibrations into useable power. Two types of devices of Thunder diaphragms are used: (1) a composite made of stainless steel, plain polyimide, a piezoelectric layer, plain polyimide, and copper; (2) and a second composite made with the same materials except that micro nickel inclusions are suspended into the polyimide layer. The first type produced a maximum average power of 2,585μW (~2.6mW) with a power density of 1411μW/cm2 (~1.4mW). The maximum total energy was 541,114μJ (~0.54J). The second type produced a maximum average power of 3,800μW (~3.8mW) with a power density of 2,073μW/cm2 (~2mW/cm2). The maximum total energy produced 1,187,939μJ (~1.19J). Based on these energy calculations, it was found that a plain polyimide diaphragm could theoretically charge a 1000mA-hr battery in a range from 3.32 hours to 32.32 hours depending on the energy harvesting circuit while nickel polyimide diaphragm could charge it in a range from 3.38 hours to 20.01 hours. These results show that THUNDER can effectively generate power from a steady sinusoidal source at frequencies below 10 Hz for the charging of batteries or for directly powering a device.

Epoxy composite laminated piezoelectric stress-enhanced actuators (ECLIPSE) have been developed for potential applications by the United States Air Force and others. This class of actuators offers several advantages over other unimorph actuators such as lighter weight, design flexibility, and short production time. Anisotropic differential thermal expansion is utilized in the design of the actuators to achieve large out-of-plane curvature and place the brittle piezoelectric ceramic in residual compression. The numerous composite material choices and configurations can be used to control characteristics of the actuator such as radius of curvature and force output. ECLIPSE actuators were characterized during this study. They were made from layers of Kevlar 49/epoxy composite and a lead zirconate titanate ceramic (PZT) plate. All ECLIPSE actuators tested were built with a PZT plate with the same dimensions and material, but had different layup configurations. By changing the stacking order of the composite and PZT material, characteristics of the actuator were altered. The performance of each ECLIPSE actuator was compared. The maximum achievable displacement of each actuator was measured by cyclically applying an electric field at low frequency between zero and the maximum electric field allowable for the piezoelectric material. The frequency was also increased to a resonance condition to characterize the fatigue behavior of these actuators. In addition, the force output of various actuators was measured with a four-point bending apparatus. The experimental data was compared to a classical lamination theory model and an extended classical lamination theory model. These models were used to predict actuator behavior as well as to calculate the stress and strain distribution through the thickness of the actuator.

Abstract Many electrical devices already surround us in our everyday life. Some devices monitor car performance and traffic while others exist in handheld devices used by the general public. Electrical devices also control manufacturing processes and protect workers from exposure to hazardous working environment. All these devices require electricity to operate. This exponential growth of low power electronic devices in industry, healthcare, military, transportation and in portable personal devices has led to an urgent need for system integrated energy sources. Many energy harvesting technologies have been developed to serve as a power source in close proximity to the electrical device itself. Solar and magnetic energy harvesters are the most common solutions when conditions are suitable. A more recent technique, called piezoelectric energy harvesting, has raised significant interest among scientists and in industry. Through piezoelectric (ceramic) material mechanical energy can be harvested and converted to electrical energy. This method requires accurate analysis of the kinetic energy experienced by the piezoelectric material so that the mechanics can be suitably designed. At the same time the mechanical design has to protect the piezoelectric material from intense forces that might cause cracks, while still transmitting the kinetic energy efficiently. These requirements usually mean a specific energy harvest design for each ambient energy source at hand. This thesis is focused on energy harvesting from low frequency compressions using piezoelectric ceramic materials. The objective was to manufacture, measure and implement structures that could sustain the forces experienced under the heel of a foot and maximize the harvested energy amount and efficiency. Two different construction designs were developed and optimised with an iterative process. The kinetic energy impulse under the heel part of the foot was studied by measuring the electrical output of the harvester during walking and then analysed with modelling software. The results were used to create a walking profile for a computer controlled piston to study the input energy phase, speed and force influence on the amount of the harvested energy and the efficiency of the harvesting process. Finally, the functionality of the concept was tested in a real environment with an energy harvester inserted inside a running shoe. The developed harvester showed the highest energy density reported in this frequency region. / Tiivistelmä Monet elektroniset laitteet ympäröivät meitä jokapäiväisessä elämässä. Ne tarkkailevat auton toimintaa tai liikennettä ja toiset toimivat aina mukana kulkevissa kannettavissa laitteissa. Töissä ne valvovat valmistusprosesseja tai varoittavat työntekijöitä vaarallisista työolosuhteista. Kaikki nämä laitteet tarvitsevat sähköä toimiakseen. Pienitehoisten elektronisten laitteiden eksponentiaalinen kasvu teollisuudessa, terveyssektorilla, puolustusteollisuudessa, kulkuneuvoissa sekä kannettavassa kulutuselektroniikassa on johtanut suureen tarpeeseen kehittää järjestelmiin integroituja energialähteitä. Monia energiankeräystekniikoita on kehitetty toimimaan elektronisten laitteiden läheisyydessä. Aurinkopaneelit ja magneettiset energiankeräysmenetelmät ovat yleisimpiä ratkaisuja, jos olosuhteet antavat siihen mahdollisuuden. Pietsosähköinen energiankeräys on uudempi tekniikka, joka on herättänyt kasvavaa huomiota tutkimusyhteisössä sekä teollisuudessa. Pietsosähköisen materiaalin avulla mekaaninen energia voidaan muuntaa suoraan sähköiseksi energiaksi. Tässä tekniikassa kineettinen energia tulee analysoida tarkasti mekaniikka suunnittelua varten, jotta se saadaan kohdistettua tehokkaasti pietsosähköiseen materiaaliin. Lisäksi mekaniikan tulee suojata materiaalia voimilta, jotka voivat johtaa murtumiin. Näistä vaatimuksista johtuen jokainen ulkoinen energialähde vaatii yleensä yksilöllisen energiankeräysrakenteen. Tämä väitöstyö keskittyy pietsosähköisten keraamien hyödyntämiseen energiankeräyksessä matalataajuisista mekaanisista voimista. Tarkoituksena oli suunnitella, valmistaa, mitata ja asentaa rakenteita, jotka kestävät kantapäähän kohdistuvia voimia kävelyn ja juoksun aikana sekä maksimoida talteen saatava energia ja hyötysuhde. Kaksi erilaista rakennetta suunniteltiin, valmistettiin ja optimoitiin energiankeräystä varten. Kantapäähän kohdistuva kineettinen energia analysoitiin mallinnusohjelmistolla ja mittaamalla sähköinen vaste energiakeräys rakenteesta. Tuloksien avulla suunniteltiin kävelyprofiilia imitoiva mekaaninen männän liike, jonka avulla tutkittiin kohdistettavan voiman nopeuden, vaiheen ja suuruuden vaikutusta energiankeräyksen hyötysuhteeseen ja saatavaan tehoon. Viimeisenä energiankeräysrakenteen toimivuutta testattiin oikeassa ympäristössä asentamalla se juoksukenkään. Kehitetyllä pietsosähköisellä energiakeräimellä saavutettiin korkeimmat raportoidut energiatiheydet käytetyllä taajuusalueella.

The design and implementation of a morphing unmanned aircraft using smart materials is presented. Articulated lifting surfaces and articulated wing sections actuated by servos are difficult to instrument and fabricate in a repeatable fashion on thin, composite-wing micro-air-vehicles. Assembly is complex and time consuming. A type of piezoceramic composite actuator commonly known as Macro Fiber Composite (MFC) is used for wing morphing. The actuation capability of this actuator on fiberglass unimorph was modeled by the Rayleigh-Ritz method and quantified by experimentation. Wind tunnel tests were performed to compare conventional trailing edge control surface effectiveness to an MFC actuated wing section. The continuous surface of the MFC actuated composite airfoil produced lower drag and wider actuation bandwidth. The MFC actuators were implemented on a 0.76 m wingspan aircraft. The remotely piloted experimental vehicle was flown using two MFC patches in an elevator/aileron (elevon) configuration. Preliminary testing has proven the stability and control of the design. Flight tests were performed to quantify roll control using the actuators. Force and moment coefficients were measured in a low-speed, open section wind tunnel, and the database of aerodynamic derivatives were used to analyze control response. / Master of Science

Numerous vibrating electromechanical systems lack a rigid connection to the inertial frame. An artificial inertial frame can be generated by a shaker, which compensates for vibrations. In this article, we present an encapsulated and perforated unimorph bending plate for this purpose. Vibrations can be compensated up to the first eigenfrequency of the system. As basis for an efficient system simulation and optimization, a new three-port multi-domain network model was developed. An extension qualifies the network for the simulation of the acoustical behavior inside the capsule. Network parameters are determined using finite element simulations. The dynamic behavior of the network model agrees with the finite element simulation results up to the first resonance of the system. The network model was verified by measurements on a laboratory setup, too. Furthermore, the network model could be simplified and was applied to determine the influence of various parameters on the stabilization performance of the plate transducer. The performance of the piezoelectric bending plate for position stabilization had been in addition investigated experimentally by measurements on a macroscopic capsule.

The master’s thesis deals with the proposal of microactuator based on SMART material. The thesis opens with the comparison of SMART materials which are suitable for actuator construction from the point of view of a reaction on stimulation in form of deformation. Subsequent part of the thesis is the report theory of piezoelectric effect, it also describes direct and indirect effects and it concerns about the description of piezoelectric materials. The thesis focuses on several principles of piezoactuators and motors. The last part of the thesis includes modeling and simulation of piezoelectric material in program ANSYS 13.0 and dimensioning geometric of actuator with evaluation of impact of parameters on final motion.

This thesis contributes to the state of the art in integrated design of insect-scale piezoelectric actuated flapping wing vehicles through the development of novel theoretical models for flapping wing aerodynamics and piezoelectric actuator dynamics, and integration of these models into a closed form design process. A comprehensive literature review of available engineered designs of miniature rotary and flapping wing vehicles is provided. A novel taxonomy based on wing and actuator kinematics is proposed as an effective means of classifying the large variation of vehicle configurations currently under development. The most successful insect-scale vehicles developed to date have used piezoelectric actuation, system resonance for motion amplification, and passive wing pitching. A novel analytical treatment is proposed to quantify induced power losses in normal hover that accounts for the effects of non uniform downwash, wake periodicity and effective flapping disc area. Two different quasi-steady aerodynamic modelling approaches are undertaken, one based on blade element analysis and one based on lifting line theory. Both approaches are explicitly linked to the underlying flow physics and, unlike a number of competing approaches, do not require empirical data. Models have been successfully validated against experimental and numerical data from the literature. These models have allowed improved insight into the role of the wing leading-edge vortex in lift augmentation and quantification of the comparative contributions of induced and profile drag for insect-like wings in hover. Theoretical aerodynamic analysis has been used to identify a theoretical solution for the optimum planform for a flapping wing in terms of chord and twist as a function of span. It is shown that an untwisted elliptical planform minimises profile power, whereas a more highly tapered design such as that found on a hummingbird minimises induced power. Aero-optimum wing kinematics for hovering are also assessed. It is shown that for efficient flight the flapping velocity should be constant whereas for maximum effectiveness the flapping velocity should be sinusoidal. For both cases, the wing pitching at stroke reversal should be as rapid as possible. A dynamic electromechanical model of piezoelectric bending actuators has been developed and validated against data obtained from experiments undertaken as part of this thesis. An expression for the electromechanical coupling factor (EMCF) is extracted from the analytical model and is used to understand the influence of actuator design variables on actuator performance. It is found that the variation in EMCF with design variables is similar for both static and dynamic operation, however for light damping the dynamic EMCF will typically be an order of magnitude greater than for static operation. Theoretical contributions to aerodynamic and electromechanical modelling are integrated into a low order design method for propulsion system sizing. The method is unique in that aside from mass fraction estimation, the underlying models are fully physics based. The transparency of the design method provides the designer with clear insight into effects of changing core design variables such as the maximum flapping amplitude, wing mass, transmission ratio, piezoelectric characteristics on the overall design solution. Whilst the wing mass is only around 10% of the actuator mass, the effective wing mass is 16 times the effective actuator mass for a typical transmission ratio of 10 and hence the wing mass dominates the inertial contribution to the system dynamics. For optimum aerodynamic effectiveness and efficiency it is important to achieve high flapping amplitudes, however this is typically limited by the maximum allowable field strength of the piezoelectric material used in the actuator.