Piezoelectric material based sensors are widely used in applications such as automobiles, aircraft, and industrial systems. In past decade, attention has been focused on synthesizing composites that can provide multifunctional properties, i.e., same material exhibits two or more properties. In this group of composites, magnetoelectric materials are particularly interesting as they provide the opportunity of coupling magnetic and electric field. Another class of composite materials that are being actively pursued is piezoresistive materials. Piezoresistivity refers to change in resistance with applied stress and these materials are promising for enhancing the sensitivity of current generation pressure sensors based on silicon. In this study, we focus on two composites systems: ferrite / Terfenol-D / nickel — lead zirconate titanate (magnetoelectric); and lanthanum strontium manganate (LSMO) — carbon nanotube (CNT) – silicon carbonitride (SiCN) (piezoresistive). Recently, Islam et al. have reported a magnetic field sensor based on a piezoelectric transformer with a ring- dot electrode pattern. In this thesis, this design was further investigated by synthesizing Terfenol-D / PZT laminate. The fabricated sensor design consists of a ring-dot piezoelectric transformer laminated to a magnetostrictive disc and its working principle is as follows: When a constant voltage is applied to the ring section of the piezoelectric layer at resonance, a stress is induced in the dot section. Then, if an external magnetic object is introduced in the vicinity of the dot section, the effective elastic stiffness is increased, altering the resonance frequency (fr). The variation of resonance frequency and magnitude of output voltage with applied magnetic field was characterized and analyzed to determine the sensitivity. The sensor showed a shift of ~1.36Hz/Oe over the frequency range of 137.4<fr<144.2 kHz with increasing magnetic bias from 1<Hdc<6kOe. Next, in order to overcome the need of magnetic DC bias in current magnetoelectric composites, a metal – ceramic core-shell composite structure was investigated. Metal-ceramic composite particles were synthesized at room temperature and their magnetic properties were investigated. The particles constitute a core-shell structure where the core is nickel-metal, while the shell is manganese zinc ferrite (MZF). Coprecipitation was used for synthesis of MZF nanoparticles comprising the shell, whereas nickel was synthesized by hydrazine assisted reduction of nickel ions in aqueous media. A core shell structure was then obtained by hetero-coagulation to form a shell of MZF around the nickel particles. Electron microscopy and x-ray diffraction confirmed nickel cores coated by MZF shells. Magnetization studies of MZF nano-particles revealed that they were not super-paramagnetic at room temperature, as expected for such particle sizes of 20nm in size. Sintered composites of metal-ceramic particles core-shell exhibited a magnetostriction of 5ppm. Lastly, the thesis investigates the piezoresistive properties of LSMO – CNT – SiCN composites that were synthesized by the conventional ceramic sintering technique. Recent investigations have shown that CNTs and SiCN have high piezoresistive coefficient. DSC/TGA results showed that pure CNTs decompose at temperatures of ~600°C, however, SiCN was found to sustain the sintering temperature of 1300°C. Thus, LSMO – SiCN composites were used for the final analysis. A fractional resistivity change of 4% was found for LSMO — 12.5 vol% SiCN composites which is much higher compared to that of unmodified LSMO. / Master of Science

No description available.

<p>Force control is introduced to robots to solve the problem in machining applications due to the fact that the robot compliance might cause deviation between actual and desired robot path. Also large tolerances in the casting process as well as positioning errors from the clamping create deviations for which the force control technology can adept. Force control has also shown successful in automatic learning of paths along non linear surfaces.</p><p>This study investigates the possibility of introducing robots equipped with force control at Volvo Aero Corporation in order to robotize polishing and deburring processes. These are today performed by manual labor. This study investigates more specifically the ABB Force Control machining application package. The polishing process has shown to be very complex and today’s version of the ABB force control package cannot give sufficiently robust results to be recommended for implementation. The major issue is the non-existing compliance of tool orientation needed to adapt to casting and positioning deviations due to varying work piece dimensions. The deburring process has however shown to be easier to handle, and a robot cell and methodology is proposed in this report.</p>

This thesis work is about further developing an existing capacitive MEMS sensor for in situ TEM nanoindentation developed by Nanofactory Instrument AB. Today, this sensor uses a parallel plate capacitor suspended by springs to measure the applied force. The forces are in the micro Newton range. One major issue using with this measurement technique is that the tip mounted on one of the sensor plates can move out of the TEM image when a force is applied. In order to improve the measurement technique electrostatic feedback has been investigated. The sensor’s electrostatic properties have been evaluated using Capacitance-Voltage measurements and a white light interferometer has been used to directly measure the displacement of the sensor with varying voltage. Investigation of the sensor is described with analytical models with detailed treatment of the capacitive response as function of electrostatic actuation. The model has been tested and refined by using experimental data. The model showed the existence of a serial capacitor in the sensor. Moreover, a feedback loop was tested, by using small beads as load and by manually adjusting the voltage. With the success of controlling the feedback loop manually, it is shown that the idea is feasible, but some modifications and improvements are needed to perform it more smoothly.

Force control is introduced to robots to solve the problem in machining applications due to the fact that the robot compliance might cause deviation between actual and desired robot path. Also large tolerances in the casting process as well as positioning errors from the clamping create deviations for which the force control technology can adept. Force control has also shown successful in automatic learning of paths along non linear surfaces. This study investigates the possibility of introducing robots equipped with force control at Volvo Aero Corporation in order to robotize polishing and deburring processes. These are today performed by manual labor. This study investigates more specifically the ABB Force Control machining application package. The polishing process has shown to be very complex and today’s version of the ABB force control package cannot give sufficiently robust results to be recommended for implementation. The major issue is the non-existing compliance of tool orientation needed to adapt to casting and positioning deviations due to varying work piece dimensions. The deburring process has however shown to be easier to handle, and a robot cell and methodology is proposed in this report.

<p>This thesis work is about further developing an existing capacitive MEMS sensor for in situ TEM nanoindentation developed by Nanofactory Instrument AB. Today, this sensor uses a parallel plate capacitor suspended by springs to measure the applied force. The forces are in the micro Newton range. One major issue using with this measurement technique is that the tip mounted on one of the sensor plates can move out of the TEM image when a force is applied. In order to improve the measurement technique electrostatic feedback has been investigated. The sensor’s electrostatic properties have been evaluated using Capacitance-Voltage measurements and a white light interferometer has been used to directly measure the displacement of the sensor with varying voltage. Investigation of the sensor is described with analytical models with detailed treatment of the capacitive response as function of electrostatic actuation. The model has been tested and refined by using experimental data. The model showed the existence of a serial capacitor in the sensor. Moreover, a feedback loop was tested, by using small beads as load and by manually adjusting the voltage. With the success of controlling the feedback loop manually, it is shown that the idea is feasible, but some modifications and improvements are needed to perform it more smoothly.</p>

No description available.

We introduce a sensor which uses phase shifted dual diffraction gratings in order to increase the detectable range of motion when using phase sensitive diffraction for optical detection of displacement in probe microscopy. The modified FIRAT structure is comprised of a micro-machined bridge structure with integrated diffraction gratings for use in optical detection. With this new design and modified geometry/fabrication process, we will demonstrate force sensing structures with improved displacement detection range and dynamic response. The structure is based upon a previous implementation of force sensor modified for use in AFM imaging. It is built upon a transparent substrate and the bridge / grating serve as an integrated electrostatic actuator. The previously introduced an AFM sensor structure, with integrated actuator, can feasibly obtain Pico Newton force resolution along with increased bandwidth. The advantages of the integrated phase-sensitive diffraction grating and electrostatic actuator over other cantilever based implementations are well developed, yet the FIRAT structure suffered from limited displacement detection range of about ë/4 (167.5 nm for ë = 670 nm), its dynamics were dominated by squeeze film damping and the stiffness was not suitable for many imaging applications. This limitation in range was not due to the device physical structure or actuator, but was inherent to the optical detection scheme used. Modifications to the previous structure design, and sensor detection scheme, are implemented in order to increase the detectable range of the sensor implementation, reduce damping and stiffness, and custom tailor our devices to imaging applications

abstract: The flow of liquid PDMS (10:1 v/v base to cross-linker ratio) in open, rectangular silicon micro channels, with and without a hexa-methyl-di-silazane (HMDS) or poly-tetra-fluoro-ethylene (PTFE) (120 nm) coat, was studied. Photolithographic patterning and etching of silicon wafers was used to create micro channels with a range of widths (5-50 &#956;m) and depths (5-20 &#956;m). The experimental PDMS flow rates were compared to an analytical model based on the work of Lucas and Washburn. The experimental flow rates closely matched the predicted flow rates for channels with an aspect ratio (width to depth), p, between one and two. Flow rates in channels with p less than one were higher than predicted whereas the opposite was true for channels with p greater than two. The divergence between the experimental and predicted flow rates steadily increased with increasing p. These findings are rationalized in terms of the effect of channel dimensions on the front and top meniscus morphology and the possible deviation from the no-slip condition at the channel walls at high shear rates. In addition, a preliminary experimental setup for calibration tests on ultrasensitive PDMS cantilever beams is reported. One loading and unloading cycle is completed on a microcantilever PDMS beam (theoretical stiffness 0.5 pN/ µm). Beam deflections are actuated by adjusting the buoyancy force on the beam, which is submerged in water, by the addition of heat. The expected loading and unloading curve is produced, albeit with significant noise. The experimental results indicate that the beam stiffness is a factor of six larger than predicted theoretically. One probable explanation is that the beam geometry may change when it is removed from the channel after curing, making assumptions about the beam geometry used in the theoretical analysis inaccurate. This theory is bolstered by experimental data discussed in the report. Other sources of error which could partially contribute to the divergent results are discussed. Improvements to the experimental setup for future work are suggested. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2014

Les origines des Primates font l’objet d’importantes controverses. La radiation initiale des premiers Primates ainsi que leurs liens phylogénétiques précis au sein des Euarchonta (le clade incluant les Primates, Scandentia, Dermoptères et Plesiadapiformes) sont débattus. De plus, l’interprétation fonctionnelle et évolutive de certains caractères morphologiques qui définissent les Primates est incertaine. Parmi eux, se trouvent l’acquisition de capacités de préhension manuelle et pédale, avec un pied spécialisé dans la saisie et un gros orteil opposable, ainsi que des ongles remplaçant les griffes sur les phalanges distales. De ce fait, le morphotype ancestral des Primate est très étudié, bien que l’arborealité et la petite taille de nos premiers ancêtres soient consensuelles. Le but de cette thèse était de revisiter certains aspects encore flous des origines des Primates, en se concentrant sur les mécanismes de préhension de la main et du pied, à travers une approche interdisciplinaire mêlant éthologie, biomécanique, anatomie comparée et analyse phylogénétique. Un réexamen du genre Plesiadapis (Plésiadapiforme) conduit au questionnement de l’hypothèse récente concernant les relations phylogénétiques des premiers primates. De plus, une étude quantitative des postures manuelles et pédales en relation au type de support utilisé lors de la locomotion, suivie d’une analyse morphologique des métapodes et phalanges de mains et pieds, ont été conduites sur différentes espèces de Primates et non-Primates. Les résultats furent ensuite couplés de façon intégrative afin de relier les caractères morphologiques à leur fonction, tout en évaluant leur importance phylogénétique. Les résultats de ces travaux permettent de proposer des hypothèses alternatives concernant deux caractères clés chez les Primates, comme la fonction initiale des ongles : liés plutôt à une capacité sensorielle que mécanique ; ainsi que concernant le scenario environnemental qui a pu conduire à l’évolution de leurs capacités de préhension pédale : supports fins verticaux et non la niche de fines branches. Également, un nouveau type de capteur de force spatialement résolu a été créé dans l’optique de mieux caractériser les contraintes biomécaniques en jeu lors de la locomotion arboricole. Ce dernier a des applications dans différents domaines, comme la robotique. / Primate origins are subject to important controversies. The initial radiation of first Primates and their precise relationships within Euarchontans (the clade including Primates, Scandentians, Dermopterans, and Plesiadapiformes) are still debated. Moreover, the functional and evolutionary interpretation of some of the morphological characters that define Primates is still uncertain. Among them are the acquisition of manual and pedal prehensile abilities, with a specialized grasping foot bearing an opposable hallux, and nails instead of claws on the distal phalanges. Thus, the ancestral morphotype of Primates is under active investigation, despite the consensus on the arboreality and small size of our early ancestors. This PhD dissertation aimed at revisiting some blurry aspects of primate origins focusing on hand and foot grasping mechanisms, through an interdisciplinary approach blending ethology, biomechanics, comparative morphology and phylogenetics. A reappraisal of the genus Plesiadapis (Plesiadapiformes) led to question a recent hypothesis on early Primates’ phylogeny. In addition, a quantitative analysis of manual and pedal postures relatively to substrate type used during locomotion, followed by a morphological study of hand and foot metapodials and phalanges were also conducted on series of primate and non-primate species. The results were analyzed in an integrative way to relate morphological features to functional attributes, along with assessing their phylogenetic importance. Among many results, this work allowed proposing alternative hypotheses regarding two key characters of primates, the primary function of nails: more linked to sensitivity than to a mechanical advantage; and the environmental scenario that may have driven the evolution of hallucal grasping capabilities: small vertical substrates instead of the fine branch niche. Moreover, in an effort to better understand biomechanical constraints at play during arboreal locomotion, a novel spatially-resolved force sensor was created, which has potential applications in various fields such as robotics.