Vibration energy harvesting devices have been widely used to power many electronic self-sustainable devices. The aim of this study is to introduce an alternative design to an existing electromagnetic energy harvesting devices to improve the power production of the unit. This thesis presents a multiple degree of freedom compared design and it has demonstrated higher power efficiency over a wider range of frequencies. The power outputs for both the previous single degree of freedom and the current designs are compared and the developed models are validated against their experimental values. Finally, the numerical model is used to find an optimal arrangement to produce the maximum power for the unit.

This thesis is an experimental study of shear effect of a two-degree-of-freedom cylinder in fluid flow in terms of different mass ratio. This study is done using an elastic cylinder of high natural frequency, and the free stream velocity is 0.2m/s to 1.5m/s. The results show that as mass ratio increases, the motion of cylinder becomes more stable and small, and the frequency response of cylinder self-excited is bigger than vortex-shedding response when spring constant is bigger enough. Thus it is not easy to observe the vortex-shedding frequency variation with respect to various velocities by dint of cylinder vibration. When it come to the shear effect, the effect of shear flow could decreases the drag force, and increases the lift force. Orbits of cylinder vibration is not symmetric; the displacement is more significant on low velocity side.

Piezoelectric effect was discovered in the 19th century, but the applications of piezoelectric effect were realized until the 20th century. In this paper, piezoelectric actuators, which are made based on piezoelectric effect, are employed to establish a three-degree-of-freedom micro-manipulator. The mechanism of this micro-manipulator is designed as a parallel-type mechanism. The kinematics of the micro-manipulator is also analyzed. In addition, a remote control framework is implemented with a control system and this achievement can be a demonstration for future feasibility of application of this micro-manipulator to robotic systems.

Vibration energy harvesting devices have been widely used to power many electronic self-sustainable devices. The aim of this study is to introduce an alternative design to an existing electromagnetic energy harvesting devices to improve the power production of the unit. This thesis presents a multiple degree of freedom compared design and it has demonstrated higher power efficiency over a wider range of frequencies. The power outputs for both the previous single degree of freedom and the current designs are compared and the developed models are validated against their experimental values. Finally, the numerical model is used to find an optimal arrangement to produce the maximum power for the unit.

Thesis (M.S.)--Mississippi State University. Department of Mechanical Engineering. / Title from title screen. Includes bibliographical references.

A six degree-of-freedom model for a tailless supersonic aircraft (TSA) concept was developed using MATLAB and Simulink. Aerodynamic data was provided through the computational fluid dynamics analysis of Techsburg, Inc. A three degree-of-freedom model of the configuration's longitudinal dynamics was completed first. Elevator control power was derived from the dynamic response requirements for pitch chosen by Techsburg. The propulsion model utilized General Electric F-414-400-like turbofan engines because an engine deck was readily available. Work on the six degree-of-freedom dynamic model began with determining the necessary rolling and yawing moment coefficients necessary to meet the rest of the chosen dynamic response requirements. These coefficients were then used to find the corresponding all-moving tip deflections. The CFD data showed that even at small all-moving tip deflections the rolling moment coefficient produced was much greater than the amount of yawing moment coefficient produced. This result showed that an additional roll effector was needed to counteract excess rolling moment at any given all-moving tip deflection and trim the aircraft. An angle of attack and pitch rate feedback controller was used to improve the longitudinal dynamics of the aircraft. Because this configuration lacked a vertical tail, a lateral-directional stability augmentation system was vital to its success. The lateral-directional dynamics were improved to Level 1 flying qualities through use of a modified roll/yaw damper. The modified controller fed yaw rate back to both the all-moving tips and roll effector. The six degree-of-freedom model was augmented with actuator dynamics for the elevator, roll effector, and all-moving tips. The actuators were modeled as first order lags. The all-moving tip actuator time constant was varied to determine the effect of actuator bandwidth on the lateral-directional flying qualities. After the actuator dynamics were successfully implemented, the six degree-of-freedom model was trimmed for both standard cruise and engine-out situations. The eccentuator concept from the DARPA Smart Wing program was selected as a possible conceptual design for the all-moving tip actuation system. The success of the TSA six degree-of-freedom dynamic model proved that morphing all-moving tips were capable of serving as effective control surfaces for a supersonic tailless aircraft. / Master of Science

M.A.Sc. Thesis / Most conventional seismic design intends for key structural members to yield in order to limit seismic forces, leading to structural damage after a major earthquake. To minimize this structural damage, self-centering systems are being developed. But how to estimate the peak seismic displacement of a self-centering system remains a problem for practical design. This thesis addresses this need by presenting a parametric study on the seismic displacement demands of single-degree-of-freedom (SDOF) systems with flag-shaped hysteresis considering 13,440,000 nonlinear time history analyses. Ground motion records that represent seismic hazards in active seismic regions with stiff soil and rock site conditions are used. The influences of the four independent parameters that define a flag-shaped hysteresis are presented in terms of median displacement ratios, facilitating the design-level estimation of nonlinear displacement demands on self-centering systems from the spectra displacements of elastic systems. The influence of initial period on self-centering systems is similar to its influence on traditional systems with elastoplastic hysteresis, but a much lower linear limit can be adopted for self-centering systems while achieving acceptable peak displacements. Supplemental energy dissipation suppresses the peak displacement but additional energy dissipation becomes less effective as more is added. The effect of nonlinear stiffness is small as long as it is positive and close to zero, but a negative nonlinear stiffness can lead to unstable response. Self-centering systems located on rock sites usually have smaller displacement demands than those on stiff soil sites. When the damping ratio is increased or decreased, the displacement ratios do not necessarily decrease or increase consistently. A tangent stiffness proportional damping model is considered, leading to a significant increase in displacement demands but similar overall trends. Based on the observations, regression analysis is used to develop a simplified equation that approximates the median inelastic displacement ratios of self-centering systems for design. / Thesis / Master of Applied Science (MASc)

No description available.

No description available.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: There are several ports around the world currently experiencing problems with moored vessel motions. Extreme vessel motions are mainly caused by long waves, which can become trapped inside a harbour basin. The extreme motions can cause downtime in port operations and in some instances cause mooring lines to break. Methods and procedures currently available to measure motions of moored vessels require vessel specific information as input. The implementation of these methods is seen as impractical to implement on every vessel visiting the port and require the physical measurement of some points on the vessel and/or the placement of some kind of measurement device on the vessel. A new Six Degree of Freedom (6DOF) motion measurement system for a moored vessel is presented in this document. The system analyses a video image sequence from one camera. The method estimates the 3D rigid motion for an object of known size by using a Pose from Orthography and Scaling with ITerations (POSIT) algorithm. The object for which the motion is estimated is located on the deck of the vessel and within the camera field of view. Geometric rigid body calculations allow for the calculation of camera perspective rotations and translation of an object on the vessel. Further geometric calculations allow for converting camera perspective motions to the 6DOF object motions. The primary objective of this study was to validate and verify the motions obtained from two proof-of-concept tracking systems. For evaluation purposes, the validation was done by using a small scale physical model set-up in a hydraulics laboratory and using a known method as reference. The Keoship system from the Council for Scientific and Industrial Research (CSIR) is currently one of the most accurate small scale vessel motion measurement systems and was used as reference. The first method tested was the tracking of a 2D LED rectangle mounted on the vessel. This method tracked a 2D object and was primarily used as a stepping stone to measure movement of a 3D object. The second method tracked a 3D object on the vessel. Each tracking method was tested for four different wave conditions with each condition additionally repeated twice as repeatability tests, resulting in a total of 12 tests for each tracking method. When comparing the 2D LED tracking and 3D Object tracking data to data measured with the Keoship system, results show that in general, the 3D Object tracking data compared better to the Keoship data. Tests under controlled conditions enabled a direct estimation of the absolute accuracy of the two developed methods. The verification and accuracy test results, indicated that the 2D LED tracking system should not be pursued further. The results also indicated that for prototype motions exceeding 0.6 m (i.e. storm events) the 3D Object tracking system would have an accuracy close to the maximum allowable accuracy criterion of 0.1 m. This makes the system viable at its current proof-of-concept stage for further development which would enable rapid deployment during a storm event in a prototype situation. / AFRIKAANSE OPSOMMING: Daar is verskeie hawens regoor die wêreld wat tans bewegings probleme op gemeerde skepe ervaar. Hierdie buitensporige bewegings word veroorsaak deur lang periode golwe wat binne die hawe bekkens vasgekeer word. Dit kan daartoe lei dat hawe bedrywighede tot stilstand kom en in ernstige gevalle ook veroorsaak dat meringslyne breek. Huidige metodes vir die meet van skeepsbewegings op vasgemeerde skepe, vereis skeep spesifieke inligting as inset. Die toepassing van hierdie metodes op elke skip wat die hawe besoek, word as onprakties beskou, aangesien dit die fisiese meting van sekere punte op die skip behels. In sekere gevalle is dit selfs nodig om meet toestelle op die skip te plaas. In hierdie dokument word ‘n nuwe metode aangebied om die ses grade van vryheid bewegings vir ‘n vasgemeerde skip te meet. Hierdie stelsel analiseer ‘n video beeld reeks van een kamera. Die metode bereken die 3D rigiede beweging van ‘n voorwerp, waarvan die grootte bekend is. ’n ‘Pose from Orthography and scaling with Iterations’ (POSIT) algoritme word hiervoor gebruik. Die voorwerp waarvoor beweging gemeet word is op die dek van die skip en in kamera sig. Rigiede geometriese voorwerp berekeninge word gebruik om die rotasie en translasie vanuit ‘n kamera perspektief te bereken. Verdere geometriese berekeninge maak dit moontlik om die bewegings vanuit die kamera perspektief te omskep in die ses grade van vryheid bewegings van die voorwerp. Die hoof doelwit van hierdie ondersoek was om die gemete bewegings van twee beweging stelsels te valideer en te verifieer. Die validasie en verifiëring was in ‘n hidrolise laboratorium met ‘n klein skaal model opstelling getoets. ‘n Meet metode van skeepsbeweging op klein skaal wat reeds bekend is, is gebruik as ‘n verwysingsraamwerk waarteen die metings vergelyk kan word. Die Keoship stelsel van die Wetenskaplike Nywerheids Navorsings Raad (WNNR) is tans een van die mees akkurate klein skaal skeepsbeweging meet stelsels, en was as verwysing gebruik. Die eerste bewegings metode is getoets op ‘n 2D reghoek vervaaridig uit ligstralede diodes. Hierdie metode het die 2D voorwerp gevolg en is hoofsaaklik gebruik as ‘n boublok om die beweging van ‘n 3D voorwerp te volg. Die tweede metode het die beweging van ‘n 3D voorwerp op ‘n skip gevolg. Vir elke meet metode was daar vier verskillende golf toestande. Elke golf toestand was ook ‘n verdere twee keer herhaal vir herhaalbaarheids doeleindes. Saam met die herhaalbaarheids toetse was daar in totaal, 12 toetse vir elkeen van die twee metodes gedoen. Met die Keoship metode as verwysing, bewys hierdie toetse dat die 3D metode beter resultate lewer as die 2D metode. Toetse onder beheerde toestande, het dit moontlik gemaak om die absolute akkuraatheid van albei sisteme wat ontwikkel was, te evalueer. Verifikasie en akuraatheids toetse het aangedui dat verdere ontwikkeling van die 2D metode gestuit moet word. Die resultate het ook aangedui dat die 3D metode ‘n akuraatheid baie na aan die maatstaf van 0.1 m sal hê wanneer prototipe bewegings 0.6 m oorskrei (b.v. gedurende ‘n storm). Dit sal die oplossing lewensvatbaar maak by die huidige bewys van konsep fase vir die verdere ontwikkeling wat vinnige ontplooiing gedurende ‘n storm sal moontlik maak.