Interlocking structure design and assembly

Many objects in our life are not manufactured as whole rigid pieces. Instead, smaller components are made to be later assembled into larger structures. Chairs are assembled from wooden pieces, cabins are made of logs, and buildings are constructed from bricks. These components are commonly designed by many iterations of human thinking. In this report, we will look at a few problems related to interlocking components design and assembly. Given an atomic object, how can we design a package that holds the object firmly without a gap in-between? How many pieces should the package be partitioned into? How can we assemble/extract each piece? We will attack this problem by first looking at the lower bound on the number of pieces, then at the upper bound. Afterwards, we will propose a practical algorithm for designing these packages. We also explore a special kind of interlocking structure which has only one or a small number of movable pieces. For example, a burr puzzle. We will design a few blocks with joints whose combination can be assembled into almost any voxelized 3D model. Our blocks require very simple motions to be assembled, enabling robotic assembly. As proof of concept, we also develop a robot system to assemble the blocks. In some extreme conditions where construction components are small, controlling each component individually is impossible. We will discuss an option using global controls. These global controls can be from gravity or magnetic fields. We show that in some special cases where the small units form a rectangular matrix, rearrangement can be done in a small space following a technique similar to bubble sort algorithm

Heterogeneous Self-Reconfiguring Robotics

Self-reconfiguring (SR) robots are modular systems that can autonomously change shape, or reconfigure, for increased versatility and adaptability in unknown environments. In this thesis, we investigate planning and control for systems of non-identical modules, known as heterogeneous SR robots. Although previous approaches rely on module homogeneity as a critical property, we show that the planning complexity of fundamental algorithmic problems in the heterogeneous case is equivalent to that of systems with identical modules. Primarily, we study the problem of how to plan shape changes while considering the placement of specific modules within the structure. We characterize this key challenge in terms of the amount of free space available to the robot and develop a series of decentralized reconfiguration planning algorithms that assume progressively more severe free space constraints and support reconfiguration among obstacles. In addition, we compose our basic planning techniques in different ways to address problems in the related task domains of positioning modules according to function, locomotion among obstacles, self-repair, and recognizing the achievement of distributed goal-states. We also describe the design of a novel simulation environment, implementation results using this simulator, and experimental results in hardware using a planar SR system called the Crystal Robot. These results encourage development of heterogeneous systems. Our algorithms enhance the versatility and adaptability of SR robots by enabling them to use functionally specialized components to match capability, in addition to shape, to the task at hand

Chemical, mechanical, and thermal control of substrate-bound carbon nanotube growth

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 323-357).Carbon nanotubes (CNTs) are long molecules having exceptional properties, including several times the strength of steel piano wire at one fourth the density, at least five times the thermal conductivity of pure copper, and high electrical conductivity and current-carrying capacity. This thesis presents methods of CNT synthesis by atmospheric-pressure thermal chemical vapor deposition (CVD), where effective choice of the catalyst composition and processing conditions enables growth of tangled single-wall CNTs or structures of aligned multi-wall CNTs, on bare silicon, microstructured silicon, and ceramic fibers. Applying mechanical pressure during growth controls the structure of a CNT film while causing significant defects in the CNTs. This mechanochemisty approach is used to "grow-mold" CNTs into 3D-shaped microforms. A new reactor apparatus featuring a resistively-heated suspended platform enables rapid ( 100 °C/s) temperature control and versatile in situ characterization, including laser measurement of CNT film growth kinetics, and imaging of stress-induced film cracking. By thermally pre-treating the reactant mixture before it reaches the substrate platform, aligned CNTs are grown to 3 mm length in just 15 minutes.(cont.) A microchannel array is created for combinatorial flow studies of nanomaterials growth, having velocity range and resolution far exceeding those of conventional furnaces. A detailed design methodology considers compressible slip flows within the microchannels and flow leaks across the array, and the devices are fabricated by KOH etching of silicon. Initial experiments with this system demonstrate chemically-driven transitions in CNT yield and morphology along the microchannels, and flow-directed alignment of isolated CNTs and CNT strands. Applications of aligned CNTs in reinforced composites and electromechanical probes are enabled by the CNT synthesis technologies presented here, and show significant initial promise through collaborative research projects. Overall, controlling the packing density and matrix reinforcement of aligned CNTs gives material attributes spanning from those of energy-absorbing foams to stiff solids; however, significant increases in CNT length, growth rate, and packing density must be achieved to realize macroscopic fibers and films having the properties of individual CNTs. New machines can be created for studying the limiting aspects of growth reactions, for exploring new reaction regimes, and for producing exceptionally long nanostructures, looking ahead to fabrication of CNT-based materials in a continuous and industrially-scalable fashion.by Anastasios John Hart.Ph.D

Teoria multikulttuurisista teksteistä : Erik Bergmanin musiikki multikulttuurisen Euroopan ilmiönä

This dissertation is a study of musical cultural mixtures, essentially focusing on mixtures in contemporary European art music and compositions of the Finnish-Swedish composer Erik Bergman as a complex case of cultural mixtures and mixing processes. The study suggests a theoretical framework and analytical tools for interpreting and deconstructing mixtures defined as multicultural texts. In the second part of the project, the suggested tools are applied to analyse the music of Erik Bergman, whose work is considered to be a particular example of the multicultural texts, in which the initial cultural components have blended into fusion on the level of sound. The project creates various perspectives to study the subject of musical mixtures described as virtual models of cultural communication, where different cultural identities, discourses, and aesthetics are presented simultaneously. Having as its goal the identifying and highlighting of different aspects of mixtures and strategies of their modelling, the multidisciplinary project, with a primary background in musicology and semiotics, combines diverse theories and concepts, involving different branches of semiotics (from Yuri Lotman s cultural semiotics to the intertextual studies and interpretative semiotics of Umberto Eco), as well as the concept of virtual reality, temporal theories, studies of cultural identity, the theory of topics, and studies of cultural forms of sound and their conceptualisation. The research work results in the creation of a comprehensive theory that proposes background, terminology, and several tools and strategies for studying mixtures, while tracing cultural information and its transformation inside them. The theory takes into account processes of virtual cultural modelling, the role of the author and the reader, and addresses an extensive category of the multicultural texts taken as personal creations. This novel understanding of musical mixtures leads to an analysis of mixtures on the level of sound essence and sound strategies. The research also creates a new perspective on Erik Bergman s music, an author with extraordinary cultural experiences and many cultural identities speaking through his authorial voice. The analytical part of the project demonstrates how diverse strategies of modelling, cultural compositional techniques, and sound strategies work to compose (and decompose) a multicultural text.Väitöskirja on tutkielma musiikillis-kulttuurisista sekoittumista pääkohteenaan sekoittumat ( mixtures ) modernissa eurooppalaisessa taidemusiikissa ja suomenruotsalaisen säveltäjän Erik Bergmanin sävellyksissä kulttuuristen sekoittumien ja sekoittumisprosessien kompleksisena esimerkkitapauksena. Tutkielma esittelee teoreettisen viitekehyksen ja menetelmät näiden sekoittumien musiikilliselle analyysille ja tulkinnalle. Väitöskirjan toisessa osassa edellä mainittuja menetelmiä sovelletaan Erik Bergmanin musiikin analyysiin. Hänen tuotantoaan tarkastellaan musiikillisten sekoittumien erityislaatuisena esimerkkinä, jossa alkujaan kulttuuriset komponentit sulautuvat yhteen äänen tasolla. Tutkielman kontekstissa musiikilliset sekoittumat määritellään multikulttuurisiksi teksteiksi. Näitä voidaan kuvailla kulttuurisen kommunikaation virtuaalisina malleina, joissa erilaiset kulttuuriset identiteetit, diskurssit ja estetiikat esiintyvät samanaikaisesti. Tavoitteenaan identifioida ja tuoda esiin näiden sekoittumien erilaisia aspekteja ja niiden mallintamisen strategioita tämä monitieteellinen projekti, pääasiallisena taustanaan musiikkitiede ja semiotiikka, luo erilaisia perspektiivejä musiikillisten sekoittumien tutkimiseen. Siten se yhdistää useita teorioita ja käsitteitä semiotiikan erilaiset alat mukaan lukien (Juri Lotmanin kulttuurisemiotiikasta Umberto Econ intertekstuaalisiin tutkielmiin ja tulkitsevaan semiotiikkaan). Tutkielma kytkee myös toisiinsa virtuaalisen todellisuuden käsitteen, ajallisuutta koskevat teoriat, tutkimukset kulttuurisesta identiteetistä, toposteorian ja äänen kulttuuriset ilmenemismuodot ja niiden käsitteellistämisen. Väitöskirjan tulos on monipuolinen teoria, joka esittelee taustan ja terminologian sekä erilaiset menetelmät ja strategiat sekoittumien ja niiden sisältämän kulttuurisen informaation ja transformaation tutkimiselle. Teoria käsittää myös virtuaalisen kulttuurisen mallintamisen prosessit, tekijän ja lukijan roolin sekä laaja-alaisen kategorian multikulttuurisista teksteistä yksilöllisinä luomuksina. Tämä uusi näkökulma musiikillisiin sekoittumiin johtaa niiden analyysiin äänen olemuksen ja strategioiden tasolla. Tutkimus avaa myös uusia näköaloja Erik Bergmanin musiikkiin ja niihin erityislaatuisiin kulttuurisiin kokemuksiin ja moniin kulttuurisiin identiteetteihin, jotka puhuvat hänen tekijän äänellään. Tutkimusprojektin analyyttinen osa osoittaa, kuinka mallintamisen erilaiset strategiat, säveltämisen kulttuuriset tekniikat ja äänistrategiat osallistuvat multikulttuuristen tekstien rakentumiseen (ja hajottamiseen)