Silicon and Polymer Components for Microrobots

This dissertation presents the characterization and implementation of the first microfabrication process to incorporate high aspect ratio compliant polymer structures in-plane with traditional silicon microelectromechanical systems (MEMS). This discussion begins with in situ mechanical characterization of microscale polymer springs using silicon-on-insulator-MEMS (SOI-MEMS). The analysis compares microscale samples that were tested on-chip with macroscale samples tested using a dynamic mechanical analyzer. The results describe the effect of the processing steps on the polymer during fabrication and help to guide the design of mechanisms using polymers. Characterization of the dielectric breakdown of polymer thin films with thicknesses from 2 to 14 μm between silicon electrodes was also performed. The results demonstrate that there is a strong dependence of the breakdown field on both the electrode gap and shape. The breakdown fields ranged from 250 V/μm to 635 V/μm, depending on the electrode geometry and gap, approaching 10x the breakdown fields for air gaps of the same size. These materials were then used to create compliant all-polymer thermal and electrostatic microactuators. All-polymer thermal actuators demonstrated displacements as large at 100 μm and forces as high as 55 μN. A 1 mm long electrostatic dielectric elastomer actuator demonstrated a tip displacement as high as 350 μm at 1.1 kV with a electrical power consumption of 11μW. The actuators are fabricated with elastomeric materials, so they are very robust and can undergo large strains in both tension and bending and still operate once released. Finally, the compliant polymer and silicon actuators were combined in an actuated bio-inspired system. Small insects and other animals use a multitude of materials to realize specific functions, including locomotion. By incorporating compliant elastomer structures in-plane with traditional silicon actuators, compact energy storage systems based on elastomer springs for small jumping robots were demonstrated. Results include a 4 mm x 4 mm jumping mechanism that has reached heights of 32 cm, 80x its own height, and an on-chip actuated mechanism that has been used to propel a 1.4mg projectile over 7 cm

System-Level Analysis of Autonomous UAV Landing Sensitivities in GPS-Denied Environments

This paper presents an analysis of the navigation accuracy of an fixed-wing Unmanned Aerial Vehicle (UAV) landing on a aircraft carrier. The UAV is equipped with typical sensors used in landing scenarios. Data from the Office of Naval Research is used to accurately capture the behavior of the aircraft carrier. Through simulation, the position and orientation of both the UAV and carrier are estimated. The quality of the UAV’s sensors are varied to determine the sensitivity of these estimates to sensor accuracy. The system’s sensitivity to GPS signals and visual markers on the carrier is also analyzed. These results allow designers to choose the most economical sensors for landing systems that provide a safe and accurate landing

Strongly correlated wave functions for artificial atoms and molecules

A method for constructing semianalytical strongly correlated wave functions for single and molecular quantum dots is presented. It employs a two-step approach of symmetry breaking at the Hartree-Fock level and of subsequent restoration of total spin and angular momentum symmetries via Projection Techniques. Illustrative applications are presented for the case of a two-electron helium-like single quantum dot and a hydrogen-like quantum dot molecule.Comment: 9 pages. Revtex with 2 GIF and 1 EPS figures. Published version with extensive clarifications. A version of the manuscript with high quality figures incorporated in the text is available at http://calcite.physics.gatech.edu/~costas/qdhelproj.html For related papers, see http://www.prism.gatech.edu/~ph274c

Multiple Word Meaning and Semantic Organization in Aphasia

TB

The multidimensional nature of pathologic vocal quality

Although the terms "breathy" and "rough" are frequently applied to pathological voices, widely accepted definitions are not available and the relationship between these qualities is not understood. To investigate these matters, expert listeners judged the dissimilarity of pathological voices with respect to breathiness and roughness. A second group of listeners rated the voices on unidimensional scales for the same qualities. Multidimensional scaling analyses suggested that breathiness and roughness are related, multidimensional constructs. Unidimensional ratings of both breathiness and roughness were necessary to describe patterns of similarity with respect to either quality. Listeners differed in the relative importance given to different aspects of voice quality, particularly when judging roughness. The presence of roughness in a voice did not appear to influence raters' judgments of breathiness; however, judgments of roughness were heavily influenced by the degree of breathiness, the particular nature of the influence varying from listener to listener. Differences in how listeners focus their attention on the different aspects of multidimensional perceptual qualities apparently are a significant source of interrater unreliability (noise) in voice quality ratings

Stretchable capacitive tactile skin on humanoid robot fingers - first experiments and results

A stretchable tactile sensor skin has been demonstrated on the dorsal side of a robotic hand for the first time. The sensors can detect normal pressures on the same scale as human skin but also in excess of 250 kPa and withstand strains in excess of 15%. Using tactile information from the sensors mounted on a glove worn by a humanoid robot's hand, obstacle detection and surface reconstruction tasks were successfully completed in order to demonstrate the performance of the sensors under applied strains and pressure

Hacia una teoría unificada de la producción y la percepción de la voz

At present, two important questions about voice remain unanswered: When voice quality changes, what physiological alteration caused this change, and if a change to the voice production system occurs, what change in perceived quality can be expected? We argue that these questions can only be answered by an integrated model of voice linking production and perception, and we describe steps towards the development of such a model. Preliminary evidence in support of this approach is also presented. We conclude that development of such a model should be a priority for scientists interested in voice, to explain what physical condition(s) might underlie a given voice quality, or what voice quality might result from a specific physical configuration.En la actualidad quedan por contestar dos cuestiones importantes relacionadas con la voz, a saber: (1) cuando la cualidad de la voz cambia, ¿qué alteración en el mecanismo vocal es la responsable?; y (2) si se produce un cambio en el sistema de producción de la voz, ¿qué cambio puede esperarse en la cualidad de voz percibida auditivamente? Sostenemos que la única respuesta posible a estas preguntas reside en un modelo de voz integrado que una producción y percepción, y describimos pasos hacia el desarrollo de tal modelo. Presentamos evidencias preliminares para respaldar esta propuesta. Concluimos que el desarrollo de semejante modelo debería ser una prioridad para los científicos interesados en la voz con el fin de explicar qué condición o condiciones físicas podrían subyacer a una cualidad de voz determinada, o qué cualidad de voz podría derivar de una configuración física específica

Centre-of-mass separation in quantum mechanics: Implications for the many-body treatment in quantum chemistry and solid state physics

We address the question to what extent the centre-of-mass (COM) separation can change our view of the many-body problem in quantum chemistry and solid state physics. It was shown that the many-body treatment based on the electron-vibrational Hamiltonian is fundamentally inconsistent with the Born-Handy ansatz so that such a treatment can never respect the COM problem. Born-Oppenheimer (B-O) approximation reveals some secret: it is a limit case where the degrees of freedom can be treated in a classical way. Beyond the B-O approximation they are inseparable in principle. The unique covariant description of all equations with respect to individual degrees of freedom leads to new types of interaction: besides the known vibronic (electron-phonon) one the rotonic (electron-roton) and translonic (electron-translon) interactions arise. We have proved that due to the COM problem only the hypervibrations (hyperphonons, i.e. phonons + rotons + translons) have true physical meaning in molecules and crystals; nevertheless, the use of pure vibrations (phonons) is justified only in the adiabatic systems. This fact calls for the total revision of our contemporary knowledge of all non-adiabatic effects, especially the Jahn-Teller effect and superconductivity. The vibronic coupling is responsible only for removing of electron (quasi)degeneracies but for the explanation of symmetry breaking and forming of structure the rotonic and translonic coupling is necessary.Comment: 39 pages, 11 sections, 3 appendice