In order to function safely in a dynamic environment with humans and obstacles, robots require active compliance control with force feedback. In these applications the control law typically includes full dynamics compensation to decouple the joints and cancel out nonlinearities, for which a high-fidelity model of the robot is required. In the case of a 3D-printed robot, components cannot be easily modeled due non-uniform densities, inconsistencies among the 3D printers used in manufacturing, and the use of different plastics with mechanical properties that are not widely known. To address this issue, this thesis presents an adaptive control framework which modifies the model parameters online in order to achieve satisfactory tracking performance. The inertial properties are estimated by adapting with respect to functions of the unknown parameters. This is achieved by rewriting the robot dynamics equations as the product of a matrix of known nonlinear functions of the joint states and a vector of constant unknowns. The result is a nonlinear system linearly parameterized in terms of the of the unknowns, which can be estimated using adaptation laws derived from Lyapunov stability theory. The proposed control system consists of an outer-loop impedance controller to regulate deviations from the nominal trajectory in the presence of disturbances, and an inner-loop force controller to track the joint torques commanded by the outer-loop. The proposed system is evaluated on an early prototype consisting of a 3DOF leg, and two actuator test setups for the low-level controller. / Master of Science / In order to function safely in a dynamic environment with humans and obstacles, a robot must be able to actively control its interaction forces with the outside environment. In these applications a high-fidelity model of the robot is required. In the case of a 3D-printed robot, the components in the robot cannot be easily modeled due non-uniform densities, inconsistencies among the 3D printers used in manufacturing, and the use of different plastics with mechanical properties that are not widely known. To address this issue, this thesis presents an adaptive control framework which actively modifies the model parameters in order to achieve satisfactory tracking performance. In this work, the equations of motion of the robot are manipulated in such a way that the unknown quantities are separated from the known quantities. The unknowns are updated in real time using adaptive laws derived from Lyapunov stability theory. The proposed control system consists of a high-level torque controller to regulate deviations from the nominal trajectory, and a low-level force controller to track the joint torques commanded at the high-level. The proposed system is evaluated on an early prototype of the robot consisting of a 3 degree of freedom leg, and two actuator test setups for the low-level controller.

A three-rotational degree of freedom attitude control system has been developed for the NASA Jet Propulsion Laboratory’s INSPIRE Project by the Texas Spacecraft Laboratory at The University of Texas at Austin. Using 3D plastic printing manufacturing techniques, a cold gas thruster system was created in order to detumble and maintain the attitude of two 3U CubeSats traveling through interplanetary space. A total of four thruster units were produced, including two engineering designs and two flight units. The units feature embedded sensors and millisecond level thrust control while using an inert, commercially-available refrigerant as a propellant. The thrust, minimum impulse bit, and specific impulse performance of the cold gas units was characterized using a ballistic pendulum test stand within a microtorr vacuum chamber. A heating element was used to change the temperature conditions of the propellant and determine the relationship between temperature and performance. The flight units were delivered in January of 2014 and the INSPIRE satellites are expected to launch in the upcoming year. / text

<p>Metal 3D printing typically requires high energy laser or electron sources. Recently, 3D printing using metal filled filaments becomes available which uses PLA filaments filled with metal powders (such as copper, bronze, brass, and stainless steel). Although there are some studies on their printability, the detailed study of their sintering and characterizations is still missing.</p> <p>In this study, the research is focused on 3D printing of bronze filaments. Bronze is a popular metal for many important uses. The objectives of this research project are to study the optimal processing conditions (like printer settings, nozzle, and bed temperatures) to print bronze metal filament, develop the sintering conditions (temperature and duration), and characterization of the microstructure and mechanical properties of 3D printed specimens to produce strong specimens.</p> <p>The thesis includes three components: (1) 3D printing and sintering at selected conditions, following a design of experiment (DOE) principle; (2) microstructure and compositional characterizations; and (3) mechanical property characterization. The results show that it is feasible to print using bronze filaments using a typical FDM machine with optimized printing settings. XRD spectrums show that there is no effect of sintering temperature on the composition of the printed parts. SEM images illustrate the porous structure of the printed and sintered parts, suggesting the need to optimize the process to improve the density. The micro hardness and three-point bending tests show that the mechanical strengths are highly related to the sintering conditions. This study provides important information of applying the bronze filament in future engineering applications.</p>

This diploma thesis deals with the surface modification of 3D printed metallic materials. The research part presents the most used methods of additive manufacturing and their process parameters influencing the quality of printed components. Defects arising during these processes and the techniques used to eliminate them are also described. In the experimental part of the work, the optimization of electrochemical polishing parameters was performed. The aim was to modify the rough surface of the components and thus prevent the formation of defects on the surface. The mechanical properties were investigated by means of three-point bending under static and dynamic loading. Fractographic analysis was performed on the quarry surfaces.

No description available.

The primary motivation behind this research was to determine whether 3D printed lenses printed out using the non-planar technique can help achieve better beam intensity for a 60 GHz printed-circuit-board based radar and consequently improve radar efficiency. Non-planar printing is a new development in the 3D printing industry. In the non-planar printing method, the printer is moving simultaneously in all X, Y and Z-axis. This process prints with curved layers, which helps achieve a smoother surface. For this, a newly developed version of the Slic3r, specifically called non-planar Slic3r, was used. The modelled lens was imported into this Slic3r software. The G-Code was generated, and using it, non-planar lenses were printed along with planar lenses for comparison purpose. The lenses printed out using the non-planar technique were not perfectly smooth as was thought initially. Both planar and non-planar lenses measurements were taken in a watchful environment, and the measurements were later compared. The comparison of measurements showed that the non-planar lens did not show any noticeable gain in the intensity over planar lenses. The conclusion, however, is limited to the frequency range around 60 GHz, and in the case of higher frequencies, the result may change

No description available.

No description available.

Composite materials have a wide range of applications in civil and structural engineering due to their advantages in mechanical properties and higher strengths over the base materials alone. Polymer-concrete composites are particularly attractive for use in industrial and infrastructure applications from combining the higher mechanical properties of the concrete in tension and the high tensile strength and ductile properties of the polymeric materials. However, these materials tend to be more expensive that typical concrete composites. This thesis explores the mechanical properties of two different polymer-concrete composites and their effectiveness in civil and structural applications: polymer concrete for rapid repair and 3D printed plastic-concrete composite members for energy absorption. The North Atlantic Treaty Organization (NATO) requires that emergency repair of military runways should be completed within 4 hours. In coordination with Luna Innovations Incorporated, a polymer concrete was developed by Luna for use as a rapid repair material for military runways to meet this requirement through its rapid heat curing. Its mechanical properties including its compressive and flexural strength, bond strength in various orientations, workability, modulus of elasticity, and coefficient of thermal expansion were tested and compared against another rapid repair material. The Tri-Service Pavements Working Group Manual recommendations for rigid repair materials were used as the requirements in determining whether the polymer concrete was an adequate rapid repair material. The polymer concrete formulation that was down-selected for further testing met these requirements for all tests except for the coefficient of thermal expansion. This was due to the resin itself having a high volumetric expansion when exposed to greater temperatures. As the polymer concrete is still under development, future tests are to be performed to determine the impact of the higher expansion on the surrounding runways. Additionally, inspired from naturally forming nacre found in some seashells, a 3D printed plastic-concrete beam structure was developed and tested in flexure to determine its energy absorption capabilities. The nacreous structure allows the material to experience a strain-hardening behavior, thus allowing for energy dissipation in the beam as it deflects from further applied load. It is theorized that the energy absorption capabilities would be suitable for withstanding the effects of dynamic loadings in structures, such as earthquake and blast loads. Multiple beam structures were developed and tested to determine the impact of percent-polymeric material and layout had on the energy dissipation. Overall, the specimens with more polymer in the cross-section demonstrated larger load vs. crack mouth displacement curves and fracture energy. These specimens demonstrated a higher toughness as well, making them more suitable for use in structural applications. As the project is still in development, future tests and analysis must be performed to determine their strength properties and feasibility as a structural material. The results of this thesis highlight the benefits of novel polymer composites in industrial and infrastructure applications, such as improved rapid setting characteristics and significantly enhanced mechanical and energy absorbing performance. Future work is needed to optimize these performance metrics, such as freeze thaw cycling, fatigue, and durability tests for the polymer concrete and analysis of moment capacity for the bioinspired nacreous composites. / Master of Science / Composite materials have a wide range of applications in civil and structural engineering due to their advantages in mechanical properties and higher strengths over the base materials alone. Polymer concrete composites are not as widely used due to their greater initial costs. However, they are very attractive in industrial and infrastructure applications because of the improved behavior in tension. This thesis explores the mechanical properties of two different polymer-concrete composites and their effectiveness in civil and structural applications: polymer concrete for rapid repair and 3D printed plastic-concrete composite members for energy absorption. The North Atlantic Treaty Organization (NATO) requires that emergency repair of military runways should be completed within 4 hours. In coordination with Luna Innovations Incorporated, a polymer concrete was developed by Luna for use as a rapid repair material for military runways to meet this requirement through its rapid heat curing. Its mechanical properties were tested and compared against another rapid repair material. The polymer concrete formulation that was down-selected for further testing met the requirements of the military for all tests performed except for the coefficient of thermal expansion. As the polymer concrete is still under development, future tests are to be performed to determine the impact of the higher expansion on the surrounding runways. Additionally, inspired from naturally forming nacre found in some seashells, a 3D printed plastic-concrete beam structure was developed and tested in bending to determine its energy absorption capabilities. The nacreous structure allows the material to experience a strain-hardening behavior, thus allowing for energy dissipation in the beam as it deflects from further applied load. It is theorized that the energy absorption capabilities would be suitable for withstanding the effects of earthquake and blast loads in structures. Multiple beam structures were developed and tested to determine the impact of percent-polymeric material and layout had on the energy dissipation. Overall, the specimens with more polymer in the cross-section demonstrated greater energy absorption capabilities. As the project is still in development, future tests and analysis must be performed to determine their strength properties and feasibility as a structural material. The results of this thesis highlight the benefits of novel polymer composites in industrial and infrastructure applications, such as improved rapid setting characteristics and significantly enhanced mechanical and energy absorbing performance. Future work is needed to optimize these performance metrics, such as freeze thaw cycling, fatigue, and durability tests for the polymer concrete and analysis of moment capacity for the bioinspired nacreous composites.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2016-08-29T14:56:34Z No. of bitstreams: 2 Dissertação - Anderson Almeida Dias - 2016.pdf: 2267814 bytes, checksum: ee86b1492eb772ffa46bd1de1e5e9e4b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-08-29T14:56:55Z (GMT) No. of bitstreams: 2 Dissertação - Anderson Almeida Dias - 2016.pdf: 2267814 bytes, checksum: ee86b1492eb772ffa46bd1de1e5e9e4b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-08-29T14:56:55Z (GMT). No. of bitstreams: 2 Dissertação - Anderson Almeida Dias - 2016.pdf: 2267814 bytes, checksum: ee86b1492eb772ffa46bd1de1e5e9e4b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-06-03 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / This manuscript describes development of batch injection analysis (BIA) cells using a 3D printer as well show the fabrication of pencil draw electrode on paper platform. Bia cells were employed on wall-jet configuration coupled with amperometric system. Bia systems were used to detect a product reaction obtained by paper-microreactor and determine ethanol in whiskey samples. Fabrication process using 3D printer was simple, fast (lower than four hours) and cost effectiveness (ca. $ 3.43 and 1.07 to the 1st and 2nd generation of Bia system, respectively). The 1st generation of Bia cell was production to be couple with commercial screen printed electrodes (SPEs) by DropSens (DropSens, DPR 710 model) and 2nd generation have support to put home-made electrodes. Both Bia cells, present a specific compartment to be coupled the micropipette. Paperbased microreactors (MOPs) were used with the 1st generation of Bia cell and the system was employed to measure glucose through the generation of hydrogen peroxide by the reaction of glucose with glucose oxidase and amperometric detection of H2O2 generated in the reaction at a potential of -0.25 V vs. Ag. In the same way of Bia cell, MOPs fabrication process is simpler, faster and cheaper (ca. $ 0.02 cent each). In general, the system shows a good linear response for concentration range between 1 to 10 mmo L-1. The limit of detection (LD) and quantification (LQ) found were 0.11 mmol L-1 and 0.38 mmol L-1, respectively. Besides, the measure of glucose using five different MOPs presented a good repeatability (RSD between 1.5 to 2.8%) and reproducibility (RSD = 0.66%). The 2nd generation of Bia cell was coupled with copper working electrode modified thermally and chemically. This cell was employed to determine the presence of ethanol in whisky sample using 1 mol L-1 NaOH as supporting electrolyte and potential of 0.45 V vs Ag / AgCl. The modified-electrode shows optimum stability to measure seventy minute of consecutive injection with RSD lower than 4.7%. A good linear response was obtained when concentration of ethanol ranged from 2.5 to 25% (v/v). The LD achieved was ca. 0.07% (v/v). Besides the Bia cells experiments, this work describes the fabrication process of alternative electrodes by hand drawing pencil on paper platform. Initially, the geometry of sensing electrodes was drawn using a graphic software and printed on paper surface. During printing process, toner lines were deposited on paper to delimit the electrode area. Then, the desire layout was draw using a pencil and laminated using benchtop laminator. This last step is necessary to make the electrical insulation. Fabrication process of alternative electrodes was simple, fast (~ 20 minutes) and cost effectiveness (ca. $ 0,023). Characterization of paper electrodes was made by cyclic voltammetry with potassium ferrocyanide (5 mmol L-1) in KCl solution (0.5 mol L-1). Besides, showed good peak separation (ΔEp) ca. 238 mV and excellent reproducibility. The RSD was lower than 2.25% to five different electrodes. / Esta dissertação apresenta o desenvolvimento de células para análise por injeção em batelada (BIA, do inglês “batch injection analysis”) mediante uso de uma impressora 3D assim como a fabricação de eletrodos utilizando uma técnica de escrita direta em papel. As células BIA foram utilizadas com detecção eletroquímica, visando a análise de um produto de reação realizada em microrreatores de papel e, também, de etanol em amostras de uísque. As células BIA, fabricadas no laboratório por meio de uma impressora 3D, apresentaram baixo custo (cerca de R$ 12,00 e R$ 3,75 para 1° e 2° geração respectivamente), fabricação rápida (cerca de 4 horas e 1 hora e 40 minutos para 1° e 2° geração respectivamente) e robustez. Ambas as células BIA foram utilizadas com detecção amperométrica (DA) e apresentam configuração wall-jet. A 1° geração BIA possui suporte para eletrodos serigrafados (SPEs) comerciais da DropSens e pipeta eletrônica e a 2° geração BIA possui suporte para eletrodos convencionais construídos no laboratório e pipeta eletrônica. Os microrreatores à base de papel (MOPs) foram vinculados à 1° geração da célula BIA, este sistema foi utilizado para quantificação de glicose a partir da geração de peróxido de hidrogênio mediante a reação da glicose com glicose oxidase, e detecção do H2O2 gerado com SPEs de carbono modificado com azul da prússia (DropSens, modelo DPR 710) em um potencial de -0,25 V versus Ag. A confecção dos MOPs é simples, rápida (2 horas e 30 minutos) e de baixo custo (cerca de R$ 0,06 a unidade). Para a fabricação dos microrreatores a base de papel, primeiramente foi realizada a modificação química da superfície do papel. Para, em seguida, efetuar a imobilização covalente da enzima. Os ensaios realizados utilizando os MOPs vinculados a 1° geração da célula BIA com detecção amperométrica (BIADA) apresentaram linearidade para faixa de concentração entre 1 e 10 mmol L-1 (R² = 0,990), alta repetitividade (DPR entre 1,5% e 2,8%) e elevada reprodutibilidade (DPR = 0,66%) para 5 microrreatores. Os limites de detecção e quantificação obtidos foram de 0,11 mmo L-1 e 0,38 mmol L-1 respectivamente. A 2° geração da célula BIA foi acoplada com eletrodo de trabalho (ET) de cobre modificado por tratamento químico / térmico e utilizada para verificação de adulteração em uísques através da quantificação de etanol utilizando NaOH 1 mol L-1 como eletrólito suporte e potencial de 0,45 V versus Ag/AgCl. Os ensaios utilizando a 2° geração da célula BIA-DA apresentaram linearidade para faixa de concentração entre 2,5 e 25 % v/v de etanol (R² = 0,998) e elevada estabilidade (DPR = 4,7%) para aproximadamente 70 minutos de injeções consecutivas. O limite de detecção obtido para o etanol foi de 0,07% (v/v). Os eletrodos em plataforma de papel foram produzidos através da pintura direta com lápis. Para a fabricação destes dispositivos, primeiramente o layout dos eletrodos são impressos no papel para definir a área do desenho dos eletrodos. Em seguida os eletrodos são pintados com lápis, depois os dispositivos são plastificados com polaseal com o objetivo de isolar os contatos e delimitar a área dos eletrodos. A confecção destes eletrodos é rápida (~ 20 minutos) e de baixo custo (R$ 0,082 a unidade). Os eletrodos foram caracterizados utilizando voltametria cíclica com ferrocianeto de potássio 5 mmol L-1 solubilizado em KCl 0,5 mol L-1. Estes dispositivos apresentaram elevada reprodutibilidade (DPR = 2,25%) para 5 eletrodos distintos.