Safe Human-Robot Interaction Using Variable Stiffness, Hyper-Redundancy, and Smart Robotic Skins

In service robotics, safe human-robot interaction (HRI) is still an open research topic, requiring developments both in hardware and in software as well as their integration. In UMAY1 and MEDICARE-C2projects, we addressed both mechanism design and perception aspects of a framework for safe HRI. Our first focus was to design variable stiffness joints for the robotic neck and arm to enable inherent compliance to protect a human collaborator. We demonstrate the advantages of variable stiffness actuators (VSA) in compliancy, safety, and energy efficiency with applications in exoskeleton and rehabilitation robotics. The variable-stiffness robotic neck mechanism was later scaled down and adopted in the robotic endoscope featuring hyper-redundancy. The hyper-redundant structures are more controllable, having efficient actuation and better feedback. Lastly, a smart robotic skin is introduced to explain the safety support via enhancement of tactile perception. Although it is developed for a hyper-redundant endoscopic robotic platform, the artificial skin can also be integrated in service robotics to provide multimodal tactile feedback. This chapter gives an overview of systems and their integration to attain a safer HRI. We follow a holistic approach for inherent compliancy via mechanism design (i.e., variable stiffness), precise control (i.e., hyper-redundancy), and multimodal tactile perception (i.e., smart robotic-skins)

Structural and magnetic properties of lithium ferrite (LiFe5O8) thin films: Influence of substrate on the octahedral site order

Structural properties of lithium ferrite [LiFe5O8, (LFO)] thin films are investigated as a function of substrate-induced strain and growth temperature. Through x-ray diffraction and Raman spectroscopy analysis we find LFO films grown on isostructural MgAl2O4 (MAO) are closer to bulk single crystal behavior, whereas the films remain coherently strained on lattice matched MgO substrate. Film texture and surface morphology are enhanced with better lattice match, indicating different growth modes on different substrates. Raman spectra reveal enhanced disorder of Li and Fe ions at the octahedral sites on MgO substrate contrasting with the relatively high degree of octahedral site ordering on MAO. (C) 2011 American Institute of Physics. [doi:10.1063/1.3533908

Microstructure and magnetic behavior of (Mg/Ni) co-doped ZnO nanoparticles

Zn0.95-xMgxNi0.05O nanoparticles were synthesized using sol-gel technique by varying x values from 0.01 to 0.05 in step of 0.01. The annealing temperature was optimized and 4% Ar-H-2 gas was used for the annealing process to obtain single phase Zn0.95-xMgxNi0.05O samples. The possible lost weights of samples in a wide temperature range for Zn0.95-xMgxNi0.05O samples were investigated by differential thermal analysis and thermo gravimetric analysis. X-ray diffraction of Zn0.95-xMgxNi0.05O samples exhibited single phase with annealing process under 4% Ar-H-2 gas at 450 degrees C. A structural distortion was revealed by replacing Zn2+ by Mg2+ and Ni2+ due to the ionic radius difference which gave rise to a decrease in the crystallite size. The SEM images showed cluster shape distribution in quasi-spherical particles and were almost observed in all frames with agglomeration. Magnetization measurements were conducted at room temperature for all samples under the DC magnetic field for magnetization curves (M vs. H). The magnetization curves of Mg and Ni-doped ZnO systems exhibited a ferromagnetic behavior at room temperature

Band Gap Engineering of Mg Doped ZnO Nanorods Prepared by a Hydrothermal Method

The effect of band gap on the structure, magnetic, and optical properties of Zn1-xMgxO nanorods synthesized by hydrothermal method using varying x-values from 0.00 to 0.05 with 0.01 step increment is studied. The structural phases of Zn1-xMgxO samples are determined by X-ray diffraction tool. The Rietveld analysis is performed for the selected Zn0.95Mg0.05O sample and all samples' phases are found as single phase. The concentration-dependent of lattice parameters, cell volumes, microstrain, and dislocation density, locality of the atoms and their displacement, and bond length in Zn1-xMgxO structures are detailed. Electron Spin Resonance (ESR) measurements are performed and analyzed through concentration dependence of the g-factor and the line-widths of pike to pike (Delta H-PP) of ESR spectra. A ferromagnetic behavior of the Zn0.95Mg0.05O nanorods is observed. The optical band gaps (E-g) of Zn1-xMgxO nanorods are obtained by the data taken from Ultraviolet-Visible (UV-VIS) diffuse reflectance spectroscopy. It is found that the E-g-values increased with increasing amount of Mg elements in the structure

The Temperature Effect on Structural and Magnetic Properties of Zn0.95FE0.05O Nanoparticles

Zn0.95Fe0.05O solutions were prepared by sol-gel synthesis using 2,4-pentanedionate and acetate precursors which were dissolved into the solvent and chelating agent. The nanoparticles were annealed at various temperatures (400, 450, 500, 550, and 600 C-ay) and times to reveal the temperature effect on structural and magnetic properties. The thermal behaviors of the xerogels were analyzed using differential thermal analysis and thermogravimetric analysis to determine the heat treatment temperatures. The crystal structure and particle morphology were characterized by X-ray diffraction method and scanning electron microscope measurement tools. Quantum design physical properties measurement system was used to examine the magnetic properties of synthesized nanoparticles. The temperature and applied field dependences of magnetization of nanoparticles were recorded by using a vibrating sample magnetometer. Zero-field cooling and field-cooling conditions for magnetization as a function of temperature were performed at the magnetic field of 0.5 kOe. The structure, particle size, particle morphology, and magnetic properties of nanoparticles with different doping ratio, temperature, and time of annealing process were presented

Negative Magnetization and Superconductivity in the (LaPt2Asx (x=1, 2) and BaPt2As2 Compounds

We have investigated the electrical and magnetic properties of the compounds LaPt2As, LaPt2As2, and BaPt2As2 prepared by conventional solid-state reaction, in the temperature range of 5-300 K, up to the field of H = 9 T. The zero-field cooled magnetization (M-ZFC) and field cooled magnetization (M-FC) split into two branches at the bifurcation temperatures due to large thermal hysteresis effects. A huge diamagnetic magnetization has been manifested on the M-ZFC branches in both samples. We describe different possible scenarios of the negative magnetization-like behavior. First, this huge diamagnetic signal may arise from some local nano-sized ferromagnetic clusters subjected to the negative internal field, which is originated from the local distortions in the electronic structure due to the inhomogeneous Pt atoms distributions. The second is suggested as an alternative model, so that the present phenomenon was not a true negative magnetization, the observed negative magnetization, in fact, is relative change in the magnetization. It may arise from the freezing spins at lower temperatures. The magnetic analysis reveals the development of superconductivity with a filamentary character at temperatures below 10 K for the sample LaPt2As and 22 K for the sample LaPt2As2. In order to prove the observed superconductivity, their critical current density, J(c)(H), and the normalized pinning force, F-p/(Fp,max), are obtained as a function of the applied field, and the types of flux pinning centers are identified using the conventional Beans and Dew-Hughes models. We report the resistivity data in the same temperature interval. The resistivity curves are fitted to the form rho(T) = rho(0) + rho T-1(alpha) + rho(2)exp (- T-o/T) over the entire range of the measurement temperatures. The last term presents a magnon-assisted inter-band electron-phonon electron scattering mechanism. In addition, we observe an anomaly around 115 K in LaPt2As2 associated with the charge density (CDW) phase transition

Effects of Annealing Temperature on Microstructure and Magnetic Properties of Ni0.05Zn0.95Fe2O4 Nanoparticles

The magnetic behavior of Ni0.05Zn0.95Fe2O4 nanoparticles synthesized by the sol-gel technique route was clarified To figure out the influence of annealing temperature on the structure of Ni0.05Zn0.95Fe2O4 particles, x-ray diffraction (XRD) tool was used and revealed spinel cubic structure without any secondary phases. The particle formation and sizes were obtained using scanning electron microscope (SEM). Elemental composition of the nanoparticles was also provided by an energy-dispersive x-ray analysis tool (EDX). The magnetic behaviors of the synthesized powders annealed at varying temperatures were determined by vibrating sample quantum design PPMS measurement system tool. The M-H curves of the samples showed that the samples had S-shape but they reached no saturation state at the presence even at 30 kOe

Low Field Magnetic and Electric Transport Properties of LaFeAsO and Oxygen Deficiency of LaFeAsOx

We report the magnetization and electrical resistivity measurements of LaFeAsO and oxygen deficiency LaFeAsOx prepared by solid-state reaction. Superconductivity at around 35 K and a giant diamagnetic contribution at a higher temperature have been observed in LaFeAsOx, while the parent LaFeAsO is non-superconducting. However, after subtracting the paramagnetic background magnetic contribution, the parent compound exhibits a very small superconductivity at low temperatures below T-c similar to 35. The ZFC/FC (zero-field and field cooled magnetization) curves for both samples exhibit apparent irreversibility. The susceptibility increases significantly at low fields. All these behaviors seem to be explained by considering the system consisting of micro-scale weak poly-crystallite magnets owing to the dipolar magnetic interactions among them and individual localized nanoscale magnetic regions within crystallites. Furthermore, we have obtained the critical current density and the pinning force as a function of the applied field using the conventional Beans model. We conclude that the observed superconductivity has a filamentary character based on the implication of the superconductivity properties analyses

Zincir moleküler sıvıların yüzey geriliminin bulk özellikleri ile ilişkilendirilmesi

ÖZET ZİNCİR MOLEKÜLER SIVILARIN YÜZEY GERİLİMİNİN BULK ÖZELLİKLERİ İLE İLİŞKİLENDİRİRLMESİSon yıllarda yüzey gerilimi araştırmaları, kaplama, yapışma, terleme ve köpürme gibi hem endüstriyel uygulamaları hem de fiziksel birçok olayın tanımlanması ve anlaşılmasında önemli bir rol oynamaktadır. Bu konuda deneysel ve teorik olarak birçok çalışmalar yapılmaktadır [1-4]. Bu çalışmada S-S teorisi üzerine geliştirmiş olduğumuz yüzey gerilimi modeli anlatılacaktır [5]. Bu çalışmanın bir amacı S-S teorisinden bulk için elde edilen verilerini modelimizde kullanarak yüzey gerilimi verilerini tahmin etmek sistem parametrelerini hesaplamaktır. Bu çalışmanın diğer amacı yüzey gerilimi modelimizde ortaya çıkan parametrelerin zincir uzunluğuna göre davranışını incelemektir. Modelimizde kesikli ara yüzey modeli (discrete interface model) [5] temel alınarak S-S teorisi parametreleri cinsinden sistemin Helmholtz enerjisi yazıldı ve buradan yüzey gerilimi bağıntısını elde edildi. Çalışmamızda kullanılan hidrokarbonlar n = 11, 16, 24, 78 ve 150 zincir uzunluğuna sahip lineer polietilen hidrokarbonlardır ve bunların deneysel yüzey gerilimi verileri Gregory ve Dee [6] tarafından yayınlanan makaleden alınmıştır. Modelimiz ile birlikte öngördüğümüz yüzey derinlik faktörü b, bir zincir molekülün yüzeyde kalan segmentlerinin sayısı x, yüzey segmentlerinin etkileşmedikleri (bağ yapmadıkları) koordinasyon sayısı zs ve yüzeydeki segmentlerin serbestlik dereceleri cs gibi nicelikler zincir uzunluğuna göre ve birbirlerine göre değişimleri incelendi. Örneğin zs= 1 için x değeri zincir uzunluğu arttıkça eksponansiyel artığını ve 4.93 değerine doyuma ulaştığı görülmektedir. Oysaki yüzey derinlik faktörü b değeri ise x'nin tersine hareket etmektedir yani eksponansiyel olarak azalmaktadır ve sonsuz zincir uzunluklarında b değeri 1.41'ye asimptot olmaktadır. Çalışmamız diğer yüzey gerilimi çalışmalarının sonuçları ile uyum içerisindedir. [5, 6] Modelimiz yüzey fiziği alanında kullanılması açısından umut verici ve teşvik edicidir. Bu çalışmanın uzantısı olarak mevcut veriler çerçevesinde modelin diğer farklı yapısal hidrokarbonlar ile polimer malzemelere genelleştirilmesi ve yapı ilişkisi çalışılabilir. Ayrıca tek katman kabul ettiğimiz yüzeyin gradyentine bakılarak yüzey katmanındaki işgal edilen molekül veya boşluk yoğunlaşması incelenebilir. Temmuz 2004 Cihat BOYRAZABSTRACTLINKING THE BULK PROPERTIES OF SURFACE TENSION OF CHAIN MOLECULAR LIQUIDS In recent years, investigations on surface tension play very important roles in description and understanding of many physical processes such as coating, adhesion, wetting and foaming as industrial applications. Theoretical and experimental several studies are employed in this topic. [1-4]The surface tension model based on S-S theory that we have developed in this thesis will be explained [5]. One purpose of this study is to estimate the surface tension data and calculate the system parameters in our model using data obtained for bulk from S-S theory. The other purpose of this study is to examine the behaviors of chain length parameters in our surface tension model. In our model based on discrete interface model, the Helmholtz free energy of the system [5] was written in terms of the S-S theory parameters, and from Helmholtz free energy the expression of surface tension was obtained. The hydrocarbons used in our study, chain lengths n=11, 16, 24, 78, and 150, are linear polyethylene hydrocarbons and their surface tension data are taken from the article published by Gregory ve Dee [6]In our model, the surface depth factor b, the number of segments on the surface of a chain moleculex, the number of noninteracting coordinations of surface segments zs, and degrees of freedom of these segments on the surface cs were investigated according to chain lengths of these segments and the variations of these dependent on quantities each other.For example, for zs=1 x values increase exponantially as the length of chain values increase and it is observed to saturate for the value of 4.93. However, the surface depth factor, b, behaves inversely againstx. That is, it decreases exponentially and the value of b becomes unvarying at 1.41 for the infinite chain lengths.Our result is in good agreement with the result of other studies. This model especially in the area of surface physics advancing are promising and promoting for the future studies. As an extension of this thesis, with the perspective of the existing data, this model can be applied onto other different hydrocarbons and polymer matters and studied structural relation. In addition, from the gradient surface study which we accept as an only single layer, the density of molecules or the density of holes can be explored.Temmuz 2004 Cihat BOYRA

Effect of substrate on the atomic structure and physical properties of thermoelectric Ca3Co4O9 thin films

The incommensurately layered cobalt oxide Ca3Co4O9 exhibits an unusually high Seebeck coefficient as a polycrystalline bulk material, making it ideally suited for many high temperature thermoelectric applications. In this paper, we investigate properties of Ca3Co4O9 thin films grown on cubic perovskite SrTiO3, LaAlO3, and (La0.3Sr0.7)(Al0.65Ta0.35)O-3 substrates and on hexagonal Al2O3 (sapphire) substrates using the pulsed laser deposition technique. X-ray diffraction and transmission electron microscopy analysis indicate strain-free growth of films, irrespective of the substrate. However, depending on the lattice and symmetry mismatch, defect-free growth of the hexagonal CoO2 layer is stabilized only after a critical thickness and, in general, we observe the formation of a stable Ca2CoO3 buffer layer near the substrate-film interface. Beyond this critical thickness, a large concentration of CoO2 stacking faults is observed, possibly due to weak interlayer interaction in this layered material. We propose that these stacking faults have a significant impact on the Seebeck coefficient and we report higher values in thinner Ca3Co4O9 films due to additional phonon scattering sites, necessary for improved thermoelectric properties