Design of a Self-Orienting Solar Array for Small Low-Earth Orbit Satellites

As electronics have become increasingly smaller and more capable, small satellites called cubesats are deployed in missions that would have taken much larger spacecraft 30 years ago. To power these satellites while in orbit, a novel solar array design is proposed by which these small satellites may harvest energy. With the inspiration of a sunflower that autonomously faces the sun as it passes overhead, a solar array possessing similar characteristics is desirable. The proposed design could generate more energy during the craft\u27s time in the sunlight by continuously adjusting to face the sun. More energy gathered corresponds to an enhancement of the capability of these cubesats due to the ability to accomplish missions with greater scope than those currently in use.https://ecommons.udayton.edu/stander_posters/2254/thumbnail.jp

Development of a Self-Orienting CubeSat Solar Array

The sponsor of this conceptual design project was the Air Force Institute of Technology (AFIT) at WrightPatterson Air Force Base in Dayton, Ohio. AFIT was striving to give CubeSats more capability to conduct research, reconnaissance, and other functions. One of the major barriers for AFIT to overcome to give CubeSats more capability was the ability of the CubeSat to generate usable power while in orbit. All of AFIT’s CubeSats generated the power needed while in orbit with solar panels that are rigidly mounted to the outside of the craft. AFIT believes that a new design for the solar array used on the CubeSat will generate the power needed to increase their capabilities. The design that was deemed the most appropriate at the conclusion of this stage of the project was a design for a two degree of freedom mechanism that is attached to the solar panels to better orient them towards the sun. There are three aspects of the new design coming from this project that will make it unique. 1) Draws no direct power from the CubeSat Energy Storage to perform the movement. 2) Takes up less space on the CubeSat than competing designs. 3) Takes up less of the weight limit of the CubeSat than competing designs. The new Solar Array design should be able to orient four times more solar panel area towards the sun, as compared to the current AFIT design. There will be between 3 to 4 times more energy generation from the new design of solar array as a result, and an increase in the capabilities of the CubeSats

Flexible Fingers Based on Shape Memory Alloy Actuated Modules

To meet the needs of present-day robotics, a family of gripping flexible fingers has been designed. Each of them consists of a number of independent and flexible modules that can be assembled in dierent configurations. Each module consists of a body with a flexible central rod and three longitudinally positioned shape memory alloy (SMA) wires. When heated by the Joule eect, one to two SMA wires shorten, allowing the module to bend. The return to undeformed conditions is achieved in calm air and is guaranteed by the elastic bias force exerted by the central rod. This article presents the basic concept of the module and a simple mathematical model for the design of the device. Experimental tests were carried out on three prototypes with bodies made of dierent materials. The results of these tests confirm the need to reduce the antagonistic action of the inactive SMA wires and led to the realization of a fourth prototype equipped with an additional SMA wire-driven locking/unlocking device for these wires. The preliminary results of this last prototype are encouraging

DESIGN OF A SHAPE MEMORY ALLOY COIL ACTUATED ROBOTIC FINGER WITH COMPLIANT JOINT ANTAGONISTS

This thesis investigates the development of a 3D-printable finger with compliant joints actuated by shape memory alloy (SMA) coils. This work presents the design, manufacturing, and characterization of the compliant finger mechanism, the SMA coil actuators, and an integrated prototype from analytical and experimental methods. The compliant finger mechanism is 3D-printed using thermoplastic polyurethane. Characterization of the mechanism exhibits a hysteresis profile in the force-displacement domain. The SMA coils are designed using a static two-state model, based on the required actuation stroke at discrete force-displacement coordinates. SMA coils are manufactured and characterized to obtain the actuator profiles for the SMA. The experimental profiles for the actuator and structure are used to predict equilibrium points between the two hysteresis curves. The final assembly with an SMA coil actuating the compliant mechanism is tested, and the experimental results show the actuation stroke and bias distance match the predictions from the hysteresis analysis

DESIGN OF A SHAPE MEMORY ALLOY COIL ACTUATED ROBOTIC FINGER WITH COMPLIANT JOINT ANTAGONISTS

This thesis investigates the development of a 3D-printable finger with compliant joints actuated by shape memory alloy (SMA) coils. This work presents the design, manufacturing, and characterization of the compliant finger mechanism, the SMA coil actuators, and an integrated prototype from analytical and experimental methods. The compliant finger mechanism is 3D-printed using thermoplastic polyurethane. Characterization of the mechanism exhibits a hysteresis profile in the force-displacement domain. The SMA coils are designed using a static two-state model, based on the required actuation stroke at discrete force-displacement coordinates. SMA coils are manufactured and characterized to obtain the actuator profiles for the SMA. The experimental profiles for the actuator and structure are used to predict equilibrium points between the two hysteresis curves. The final assembly with an SMA coil actuating the compliant mechanism is tested, and the experimental results show the actuation stroke and bias distance match the predictions from the hysteresis analysis

Laser Processing and Modelling of Multiple Memory Shape Memory Alloys

Laser processing of NiTi shape memory alloys (SMA) has been identified as having great potential in surface treatment, welding, and novel performance requirement applications. However, no models have been developed to predict the amount of Ni vaporized based on various laser processing parameters. Additionally, no models have been developed to accurately predict the performance of these novel materials after laser processing. This is a cause for concern regarding efficient development and functional reliability of the laser processed SMAs. Prior to full scale implementation, a better understanding of Ni vaporization rates and the resulting mechanical performance of these materials is required. The first part of this study is concerned with a systematic investigation of the preferential vaporization of Ni during laser processing. The effect of duration and peak power of the laser pulse on the transformation temperature is studied. It was observed that the cooling rate causes segregation of compositions for compositions on the Ti-rich side of the congruency point. Deconvolution of overlapping transformation peaks allowed for approximations of overall bulk composition and Ni loss. A novel model was developed to predict the change in Ni concentration based on laser pulse duration and peak power. In the second part of this study, a novel 1D model is presented for NiTi SMAs with multiple pseudoelastic plateaus. The model is scalable for any number of plateaus present in the material. It can also be adjusted to include residual strain present after unloading the stress. The model was validated by comparing it the experimental data from Multiple Memory Material (MMM). The new model was found to closely match the experimental results. Part of this study relates to accurately characterizing the tensile properties of SMAs. The third part of this study is concerned with 2-D deformation mechanisms. The effect of texture on the bending properties of NiTi is examined. It was successfully demonstrated that the preferred bending curvature of the stress induced martensite can be predicted from the orientation of the crystallographic planes. Part of this work also relates to advancing the understanding surrounding the anisotropic and incompressible behavior of the austenite to R-phase transformation

A shape memory alloy-based biomimetic robotic hand : design, modelling and experimental evaluation

Every year more the 400,000 people are subject to an upper limb amputation. Projections foresee that this number may double by the 2050. Infections, trauma, cancer, or complications that arise in blood vessels represent the main causes for amputations. The access to prosthetic care is worldwide extremely limited. This is mainly due to the high cost both of commercially available prostheses and of the rehabilitation procedure which every prostheses user has to endure. Aside from high costs, commercially available hand prostheses have faced high rejection rates, mainly due to the their heavy weight, noisy operation and also to the unnatural feel of the fingers. To overcome these limitations, new materials, such as Shape Memory Alloys (SMAs), have been considered as potential candidate actuators for these kind of devices. In order to provide a contribution in the development of performant and easily affordable hand prostheses, the development of a novel and cost-effective five-fingered hand prototype actuated by Shape Memory Alloy (SMA) wires is presented in this work. The dissertation starts with the description of a first generation of a SMA actuated finger. Structure assemblage and performances in term of force, motion and reactiveness are investigated to highlight advantages and disadvantages of the prototype. In order to improve the achievable performances, a second generation of SMA actuated finger having soft features is introduced. Its structure, a five-fingered hand prosthesis having intrinsically elastic fingers, capable to grasp several types of objects with a considerable force, and an entirely 3D printed structure is then presented. Comparing this prototype with the most important prostheses developed so far, relevant advantages especially in term of noiseless actuation, cost, weight, responsiveness and force can be highlighted. A finite element based framework is then developed, to enable additional structure optimization and further improve the SMA finger performances. On the same time, a concentrated parameters physics-based model is formulated to allow, in the future, an easier control of the device, characterized by strong nonlinearities mainly due to the Shape Memory alloy hysteretic behavior.Jedes Jahr werden weltweit bei mehr als 400.000 Menschen Amputationen der oberen Gliedmaßen durchgeführt. Prognosen gehen davon aus, dass sich diese Zahl bis zum Jahr 2050 verdoppeln wird. Hauptursachen der Amputationen sind Infektionen, Unfälle, Krebs oder Durchblutungsstörungen. Der Zugang zu prothetischer Versorgung ist besonders in den Entwicklungsländern stark eingeschränkt. Dies liegt vor allem an den hohen Kosten sowohl der im Handel erhältlichen Prothesen als auch des Rehabilitationsprozesses, den jeder Prothesenträger durchlaufen muss. Neben den hohen Kosten haben kommerziell erhältliche Handprothesen aufgrund ihres hohen Gewichts, des lauten Betriebes und auch des unnatürlichen Gefühls hohe Ablehnungsraten. Um diese Einschränkungen zu überwinden, wurden neue Materialien, wie z.B. Formgedächtnislegierungen (SMAs), als potenzielle Materialien für den Antrieb von Prothesen untersucht . Um einen Beitrag zur Entwicklung von leistungsfähigen und erschwinglichen Handprothesen zu leisten, wird in dieser Arbeit die Entwicklung eines neuartigen und kostengünstigen Fünf-Finger-Handprototyps vorgestellt, der durch Drähte aus Formgedächtnislegierungen aktiviert wird. Die Doktorarbeit beginnt mit der Beschreibung der ersten Generation eines SMA-aktivierten Fingers. Zuerst wird der Aufbau und das Wirkungsprinzip des SMA Fingers erläutert und die Leistungs- und Bewegungsfähigkeit des Systems untersucht sowie Vor- und Nachteile des Prototyps dargestellt. Anschließend, um die erreichbare Leistungsfähigkeit zu verbessern, wird eine zweite Generation von SMA-gesteuerten Fingern vorgestellt, die eine vollständig in 3D gedruckte Struktur aufweisen. Diese Fünffinger-Handprothese mit inhärent elastischen Fingern ermöglicht nicht nur das Greifen unterschiedlich geformter Objekte sondern auch das Heben und Halten schwerer Gegenstände. Dieser neuartige Prototyp wird mit den wichtigsten bisher entwickelten Prothesen verglichen und die relevanten Vorteile insbesondere in Bezug auf geräuschlose Ansteuerung, Kosten, Gewicht, Reaktionszeit und Kraft hervorgehoben. Abschließend wird ein Finite-Elemente-Modell entwickelt, mit Hilfe dessen die Fingerstruktur weiter optimiert und die Leistungsfähigkeit des SMA-Fingers noch verbessert werden kann. Zusätzlich wird ein Konzentriertes-Parameter-Modell formuliert, um, in der Zukunft, eine leichtere Regelung des Systems zu ermöglichen. Dieses ist notwendig, da der SMA-Finger starke Nichtlinearitäten aufweist, die auf das hysteretische Verhalten der Formgedächtnislegierung zurückzuführen sind

Shear-promoted drug encapsulation into red blood cells: a CFD model and μ-PIV analysis

The present work focuses on the main parameters that influence shear-promoted encapsulation of drugs into erythrocytes. A CFD model was built to investigate the fluid dynamics of a suspension of particles flowing in a commercial micro channel. Micro Particle Image Velocimetry (μ-PIV) allowed to take into account for the real properties of the red blood cell (RBC), thus having a deeper understanding of the process. Coupling these results with an analytical diffusion model, suitable working conditions were defined for different values of haematocrit