Model and control of tendon actuated robots

The use of tendons for the transmission of the forces and the movements in robotic devices has been investigated from several researchers all over the world. The interest in this kind of actuation modality is based on the possibility of optimizing the position of the actuators with respect to the moving part of the robot, in the reduced weight, high reliability, simplicity in the mechanic design and, finally, in the reduced cost of the resulting kinematic chain. After a brief discussion about the benefits that the use of tendons can introduce in the motion control of a robotic device, the design and control aspects of the UB Hand 3 anthropomorphic robotic hand are presented. In particular, the tendon-sheaths transmission system adopted in the UB Hand 3 is analyzed and the problem of force control and friction compensation is taken into account. The implementation of a tendon based antagonistic actuated robotic arm is then investigated. With this kind of actuation modality, and by using transmission elements with nonlinear force/compression characteristic, it is possible to achieve simultaneous stiffness and position control, improving in this way the safety of the device during the operation in unknown environments and in the case of interaction with other robots or with humans. The problem of modeling and control of this type of robotic devices is then considered and the stability analysis of proposed controller is reported. At the end, some tools for the realtime simulation of dynamic systems are presented. This realtime simulation environment has been developed with the aim of improving the reliability of the realtime control applications both for rapid prototyping of controllers and as teaching tools for the automatic control courses.

Process for reinforcing SLS parts by epoxy resin

[ES]The purpose of this paper is to report on the use of a combination of selective laser sintering (SLS) and vacuum casting to create plastic composites made by additive manufacturing.

Kryoelektronenmikroskopie von Proteinen: 3D-Struktur (12 A) des Hämocyanins der Schnecke Haliotis

Zusammenfassung:Die Quartärstruktur des respiratorischen Proteins Hämocyanin (Isoform HtH1) aus der marinen Schnecke Haliotis tuberculata wurde vermittels Kryoelektronen-mikroskopie und 3D-Rekonstruktion untersucht. Das Molekül ist zylinderförmig, hat einen Durchmesser von ca. 35 nm und besteht aus einer Zylinderwand und einem internen Kragenkomplex. Dieser wiederum besteht aus einem Collar und einem Arc.Die kryoelektronenmikroskopischen Aufnahmen von in glasartigem Eis fixierten HtH1-Molekülen brachte eine enorme Verbesserung der Anzahl der zur Verfügung stehenden Ansichtswinkel gegenüber den negativkontrastierten Molekülen, die auf Karbonfilm präpariert waren.Die 3D-Rekonstruktion des HtH1 mittels Aufnahmen bei drei verschiedenen Defo-kuswerten verbesserte die Auflösung noch einmal deutlich gegenüber den Rekon-struktionen, die aus Aufnahmen bei einem festen Defokuswert gemacht wurden, und zwar auf 12 Å. Das Molekül besitzt eine D5-Symmetrie.Aus dieser bisher genausten Rekonstruktion eines Molluskenhämocyanins aus EM-Bildern ließen sich folgende neue Strukturdetails ableiten:· Ein Untereinheitendimer konnte als Repeating Unit im Dekamer des HtH1 beschrieben werden.· Das Untereinheitendimer konnte aus der 3D-Dichtekarte isoliert werden. Es be-steht eindeutig aus 16 Massen, die funktionellen Domänen entsprechen. Zwei dieser Massen bilden den Collar, zwei den Arc und 12 das Wandsegment.· Die gegenläufige Anordnung der beiden Untereinheiten innerhalb dieses Unte-reinheitendimers konnten bestätigt und auf zwei Möglichkeiten eingeschränkt werden.· Die Zahl der alternativen Anordnungen der 16 funktionellen Domänen (HtH1-a bis HtH1-h) im Untereinheitendimer konnten von 80 auf 2 eingeengt werden.· Es konnte über molekulares Modellieren mithilfe einer publizierten Kristallstruk-tur eine 3D-Struktur fastatomarer Auflösung der funktionellen Domäne HtH1-g berechnet werden.· Die funktionelle Domäne HtH1-g konnte als Domänenpaar plausibel in die 3D?Dichtekarte des Untereinheitendimers eingepasst werden, und zwar in die beiden Massen des Arc.Aus der elektronenmikroskopisch gewonnenen Dichtekarte wurde mit Hilfe des

Modellazione CAD e ricostruzione virtuale di autobus pubblicitario d'epoca

L’oggetto della presente tesi è sviluppare la ricostruzione virtuale di un autobus pubblicitario progettato negli anni 50, un simbolo del design italiano legato allo sviluppo industriale del secondo dopoguerra. La tesi si sviluppa inizialmente con un’attività di ricerca e documentazione legata all'autobus, con particolare attenzione alla raccolta di immagini e disegni progettuali d’epoca, punto di partenza per la ricostruzione virtuale del mezzo. Si procede quindi alla modellazione CAD della carrozzeria cercando di replicare in modo quanto più dettagliato l’originale. Dal modello ottenuto, sono stati ricavati due prototipi di diverse dimensioni e materiali: un primo di dimensioni ridotte, realizzato tramite la tecnica del rapid prototyping, ed un secondo di dimensioni maggiori, in ureol fresato. Successivamente si procede ad uno studio preliminare di ricostruzione del mezzo con lo scopo di analizzare le principali problematiche di un’eventuale futura costruzione e messa in strada del mezzo. Tale studio parte dalla normativa vigente sulla costruzione e sulle norme di circolazione degli autobus, comprendente sia le leggi italiane sia comunitarie, riguardanti le caratteristiche dimensionali, prestazionali e di sicurezza che qualsiasi autobus con licenza di circolazione deve rispettare. Quindi verrà compiuta la scelta del telaio base da utilizzare tra quelli proposti dai maggiori costruttori europei e verrà realizzato il modello CAD anche del telaio con l’obiettivo di collegarlo alla carrozzeria e ottenere così il modello completo in tutte le sue parti. Per realizzare la scocca, verranno prese in esame le soluzioni costruttive più utilizzate dai progettisti di autobus, e viene svolto un breve studio riguardo i materiali utilizzabili a tale scopo. Sulla base di tali considerazioni si procederà alla modellazione della stessa. In ultimo si procede ad un preliminare studio fluidodinamico attraverso l’analisi CFD, e ad un preliminare studio del comportamento meccanico della struttura reticolare che sostiene la carrozzeria.

Design and Control of Robotic Hands

The application of dexterous robotic hands out of research laboratories has been limited by the intrinsic complexity that these devices present. This is directly reflected as an economically unreasonable cost and a low overall reliability. Within the research reported in this thesis it is shown how the problem of complexity in the design of robotic hands can be tackled, taking advantage of modern technologies (i.e. rapid prototyping), leading to innovative concepts for the design of the mechanical structure, the actuation and sensory systems. The solutions adopted drastically reduce the prototyping and production costs and increase the reliability, reducing the number of parts required and averaging their single reliability factors. In order to get guidelines for the design process, the problem of robotic grasp and manipulation by a dual arm/hand system has been reviewed. In this way, the requirements that should be fulfilled at hardware level to guarantee successful execution of the task has been highlighted. The contribution of this research from the manipulation planning side focuses on the redundancy resolution that arise in the execution of the task in a dexterous arm/hand system. In literature the problem of coordination of arm and hand during manipulation of an object has been widely analyzed in theory but often experimentally demonstrated in simplified robotic setup. Our aim is to cover the lack in the study of this topic and experimentally evaluate it in a complex system as a anthropomorphic arm hand system.

Analisi della correlazione tra i parametri di processo e le prestazioni dei materiali polimerici ottenuti tramite fused deposition modeling

Questa tesi si propone di realizzare una caratterizzazione del polimero ABS ottenuto con tecnica Fused Deposition Modeling in modo da ottenere dati utili alla realizzazione di parti strutturali tramite rapid prototyping.

Energy harvesting from piezoelectric devices embedded in a 3D printed wing

This thesis work has been carried out at Clarkson University in Potsdam NY, USA and involved the design of a low elongation wing, consisting of parts made by polylactide (PLA) using the fused deposition model (FDM) technology of Rapid Prototyping, then assembled together in a thin aluminum spar. The aim of the research is to evaluate the feasibility of collecting electrical energy by converting mechanical energy from the vibration of the wing flutter. With this aim piezoelectric stripes were glued in the inner part of the wing, as well as on the aluminum spar, as monomorphic configuration. During the phases of the project, particular attention was given to the geometry and the materials used, in order to trigger the flutter for low flow velocity. The CAD software SolidWorks® was used for the design of the wing and then the drawings were sent to the Clarkson machine shop in order to to produce the parts required by the wing assembly. FEM simulations were performed, using software MSC NASTRAN/PATRAN®, to evaluate the stiffness of the whole wing as well as the natural vibration modes of the structure. These data, in a first approximation, were used to predict the flutter speed. Finally, experimental tests in the Clarkson wind tunnel facility were carried out in order to validate the results obtained from FEM analysis. The power collected by the piezoelectrics under flutter condition was addressed by tuning the resistors downstream the electronic circuit of the piezoelectrics.

Getting in touch-3D printing in Forensic Imaging

With the increasing use of medical imaging in forensics, as well as the technological advances in rapid prototyping, we suggest combining these techniques to generate displays of forensic findings. We used computed tomography (CT), CT angiography, magnetic resonance imaging (MRI) and surface scanning with photogrammetry in conjunction with segmentation techniques to generate 3D polygon meshes. Based on these data sets, a 3D printer created colored models of the anatomical structures. Using this technique, we could create models of bone fractures, vessels, cardiac infarctions, ruptured organs as well as bitemark wounds. The final models are anatomically accurate, fully colored representations of bones, vessels and soft tissue, and they demonstrate radiologically visible pathologies. The models are more easily understood by laypersons than volume rendering or 2D reconstructions. Therefore, they are suitable for presentations in courtrooms and for educational purposes.

Anisotropic Mechanical Properties of ABS Parts Fabricated by Fused Deposition Modelling

In recent years, layered manufacturing (LM) processes have begun to progress from rapid prototyping techniques towards rapid manufacturing methods, where the objective is now to produce finished components for potential end use in a product (Caulfield et al., 2007). LM is especially promising for the fabrication of specific need, low volume products such as replacement parts for larger systems. This trend accentuates the need for a thorough understanding of the associated mechanical properties and the resulting behavior of parts produced by layered methods. Not only must the base material be durable, but the mechanical properties of the layered components must be sufficient to meet in-service loading and operational requirements, and be reasonably comparable to parts produced by more traditional manufacturing techniques. This chapter presents the details of a study completed to quantitatively analyze the potential of fused deposition modelling to fully evolve into a rapid manufacturing tool. The project objective is to develop an understanding of the dependence of the mechanical properties of FDM parts on raster orientation and to assess whether these parts are capable of maintaining their integrity while under service loading. The study examines the effect of fiber orientation, i.e. the direction of the polymer beads relative to the loading direction of the part, on a variety of important mechanical properties of ABS components fabricated by fused deposition modeling. Tensile, compressive, flexural, impact, and fatigue strength properties of FDM specimens are examined, evaluated, and placed in context in comparison with the properties of injection molded ABS parts.

Semi-Automated Creation of Converged iTV Services: From Macromedia Director Simulations to Services Ready for Broadcast

While sound and video may capture viewers' attention, interaction can captivate them. This has not been available prior to the advent of Digital Television. In fact, what lies at the heart of the Digital Television revolution is this new type of interactive content, offered in the form of interactive Television (iTV) services. On top of that, the new world of converged networks has created a demand for a new type of converged services on a range of mobile terminals (Tablet PCs, PDAs and mobile phones). This paper aims at presenting a new approach to service creation that allows for the semi-automatic translation of simulations and rapid prototypes created in the accessible desktop multimedia authoring package Macromedia Director into services ready for broadcast. This is achieved by a series of tools that de-skill and speed-up the process of creating digital TV user interfaces (UI) and applications for mobile terminals. The benefits of rapid prototyping are essential for the production of these new types of services, and are therefore discussed in the first section of this paper. In the following sections, an overview of the operation of content, service, creation and management sub-systems is presented, which illustrates why these tools compose an important and integral part of a system responsible of creating, delivering and managing converged broadcast and telecommunications services. The next section examines a number of metadata languages candidates for describing the iTV services user interface and the schema language adopted in this project. A detailed description of the operation of the two tools is provided to offer an insight of how they can be used to de-skill and speed-up the process of creating digital TV user interfaces and applications for mobile terminals. Finally, representative broadcast oriented and telecommunication oriented converged service components are also introduced, demonstrating how these tools have been used to generate different types of services.