255 research outputs found
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Mechatronics of holonomic mobile base for compliant manipulation
No full texttextIn order to operate safely and naturally in human-centered environments, robots need to respond compliantly to force and contact interactions. While advanced robotic torsos and arms have been built that successfully achieve this, a somewhat neglected research area is the construction of compliant wheeled mobile bases. This thesis describes the mechatronics behind Trikey, a holonomic wheeled mobile base employing torque sensing at each of its three omni wheels so that it can detect and respond gracefully to force interactions. Trikey's mechanical design, kinematic and dynamic models, and control architecture are described, as well as simple experiments demonstrating compliant control. Trikey is designed to support a force-controlled humanoid upper body, and eventually, the two will be controlled together using whole-body control algorithms that utilize the external and internal dynamics of the entire system.Mechanical Engineerin
Motivation and Design Considerations of a Compliant Mobile Base for Human-Centered Robots
No full textAbstract – Robotics is a growing field that has received tremendous support and focus in recent years. Backed by government and industry interests, robots now have the potential to move beyond traditional manufacturing setting into human-centered environments. Therefore, safety emerges as one of the most fundamental requirements in designing Human-Centered Robots (HCRs). To attain HCRs with high mobility and safe behaviors, we designed and built a torque-controlled omni-directional mobile base, Trikey 2012, at the Human-Centered Robotics Lab in Mechanical Engineering Department. Our design focused on reducing backlash, friction, uneven load distribution, and difficult assembly steps to create a high performance compliant mobile base for HCRs. I
Base Force/Torque Sensing for Position based artesian Impedance Control
No full textIn this paper, a position based impedance controller
(i.e. admittance controller) is designed by utilizing
measurements of a force/torque sensor, which is mounted at the
robot’s base. In contrast to conventional force/torque sensing
at the end-effector, placing the sensor at the base allows to
implement a compliant behavior of the robot not only with
respect to forces acting on the end-effector but also with
respect to forces acting on the robot’s structure. The resulting
control problem is first analyzed in detail for the simplified
one-degree-of-freedom case in terms of stability and passivity.
Then, an extension to the Cartesian admittance control of
a robot manipulator is discussed. Furthermore, it is shown
how the steady state properties of the underlying position
controller can be taken into account in the design of the
outer admittance controller. Finally, a simulation study of the
Cartesian admittance controller applied to a three-degrees-offreedom
manipulator is presented
Manipulation
No full textI would like to thank my advisor, Luis Sentis, for his support and guidance. His passion for robotics drove me to pursue the research described in this thesis. I also thank Benito Fernández for mentoring and working with me throughout my time at UT, and for serving as my second reader. My primary collaborators on the Trikey project have been Pius Wong and Frank Lima, and I am grateful to them for their efforts and their company. I must also acknowledge Nick Paine and Josh Petersen, who have contributed significantly to bringing the base to where it is today, and who have answered many of my hardware and software questions. My other HCRL labmates, including Matt Gonzales, Sehoon Oh, Mike Slovich, and Chris Slaughter have all also helped out in one way or another. I thank Lonny Stern for organizing RoboTech Velocity Prep, and the Del Valle High School students who participated in the program and helped build and name the first prototype of Trikey. I still think the name should have been ”Omnilicious,” but majority rules. I acknowledge Meka Robotics for building Trikey’s electronics, and I thank everyone who helped host Luis and I during our visit. Robby Kelbley and Benjamin Valenti, especially, have been incredibly patient and competent with debugging our software and hardware issues. Finally, I am grateful to all of my classmates and friends at UT who have enriched my experience here, and to my parents and sister for their love and support. v Mechatronics of Holonomic Mobile Base for Complian
Kinematically Optimal Catching a Flying Ball with a Hand-Arm-System
No full textA robotic ball-catching system built from a multi- purpose 7-DOF lightweight arm (DLR-LWR-III) and a 12 DOF four-fingered hand (DLR-Hand-II) is presented. Other than in previous work a mechatronically complex dexterous hand is used for grasping the ball and the decision of where, when and how to catch the ball, while obeying joint, speed and work cell limits, is formulated as an unified nonlinear optimization problem with nonlinear constraints. Three different objective functions are implemented, leading to significantly different robot movements. The high computational demands of an online realtime optimization are met by parallel computation on distributed computing resources (a cluster with 32 CPU cores). The system achieves a catch rate of > 80% and is regularly shown as a live demo at our institute
Non-Linear Base-Station Processing within a 3GPP Compliant Framework
No full textMIMO mobile systems, with a large number of antennas at the base-station side, enable the concurrent transmission of multiple, spatially separated information streams, and therefore, enable improved network throughput and connectivity both in uplink and downlink transmissions. Traditionally, such MIMO transmissions adopt linear base-station processing, that translates the MIMO channel into several single-antenna channels. While such approaches are relatively easy to implement, they can leave on the table a significant amount of unexploited MIMO capacity and connectivity capabilities. Recently-proposed non-linear base-station processing methods claim this unexplored capacity and promise substantially increased network throughput and connectivity capabilities. Still, to the best of the authors' knowledge, non-linear base-station processing methods not only have not yet been adopted by actual systems, but have not even been evaluated in a standard-compliant framework, involving of all the necessary algorithmic modules required by a practical system. In this work, for the first time, we incorporate and evaluate non-linear base-station processing in a 3GPP standard environment. We outline the required research platform modifications and we verify that significant throughput gains can be achieved, both in indoor and outdoor settings, even when the number of base-station antennas is much larger than the number of transmitted information streams. Then, we identify missing algorithmic components that need to be developed to make non-linear base-station practical, and discuss future research directions towards potentially transformative next-generation mobile systems and base-stations (i.e., 6G) that explore currently unexploited non-linear processing gains
Tecnologías middleware para el desarrollo de servicios en entornos de computación ubicua
No full textEn esta Tesis doctoral realizamos contribuciones en el campo de la definición de tecnologías middleware para el desarrollo de servicios en entornos de computación ubicua.
En primer lugar, abordamos el problema del descubrimiento de servicios, que permitirá que de forma automática un dispositivo descubra los servicios ofrecidos por otros dispositivos que le rodean. Aunque existen propuestas en este sentido, no cubren todas las necesidades que imponen estos nuevos entornos de computación, por lo que hemos definidio un nuevo mecanismo de descubrimiento: Pervasive Discovery Protocol (PDP).
En sengudo lugar, proponemos el uso de la tecnología de agentes móviles como middleware para el desarrollo de servicios en entornos ubicuos. Los agentes se caracterizan por estar orientados a realizar tareas, por ser autónomos, por su capacidad de cooperar y si poseen la característica de movilidad, por ser capaces de moverse a sistemas remotos para realizar sus tareas, minimizando el coste de las comunicaciones. Estas características se adaptan a las restricciones que imponen la computación ubicua. En esta línea, contribuimos a la adaptación del estándar de agentes FIPA para su funcionamiento en estos entornos, y en concreto, nos centramos en el Directory Faciliator (DF). Estas propuestas nos han llevado a participar de forma activa en el comité técnico FIPA Ad-Hoc.
_________________________________________________In this Ph.D. dissertation, we contribute to the definition of middleware technologies for the development of services in pervasive computing environments. First, we broach the problem of service discovery, that allow devices to automatically discover the services offered by other devices in their surroundings. Although other proposais exist, we think none of them fulfils the needs of these new environments, so we have defined a new discovery mechanism: the Pervasive Discovery Protocol (PDP). PDP is a new protocol designed for local scopes, fully distributed, where requests and replys are both multica,sted, and where each device stores in a local cache the advertisements listened so far and shares this information with the devices arround it. PDP manages to reduce the number of
messages transmited per service request while obtaining high service discovery ratios, and besides it makes devices with greater availability time to answer flrst, so minimizing the battery dram of the more power-constrained ones.
Secondly, we propose the use of mobile agents technology as the middleware for the development of services in a pervasive computing nvironment. Agents are characterized by their autonomous and goal-oriented behaviour, their ability to cooperate with other agents and, if mobile, they are able to move to remote systems to carry out their task, so minimizing the communication cost. These characteristics fit well into the restrictions that pervasive computing impose. We
also aim to adapt the FIPA standard to these environments; specifically, we concentrate in the yellow pages service, the so called Directory Facilitator (DF). In our solution, we define a new agent, the Service Discovery Agent (SDA), that uses an underlaying implementation of our service discovery protocol, PDP, to make
efficient searches of remote services, removing the mechanism of DFs federation defined by FIPA. These proposais have been presented and discussed in the FIPA Ad-Hoc Technical Commitee, after what we were invited to take part and are now an active member of it
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Methodology for creating human-centered robots : design and system integration of a compliant mobile base
No full texttextRobots have growing potential to enter the daily lives of people at home, at work, and in cities, for a variety of service, care, and entertainment tasks. However, several challenges currently prevent widespread production and use of such human-centered robots. The goal of this thesis was first to help overcome one of these broad challenges: the lack of basic safety in human-robot physical interactions. Whole-body compliant control algorithms had been previously simulated that could allow safer movement of complex robots, such as humanoids, but no such robots had yet been documented to actually implement these algorithms. Therefore a wheeled humanoid robot "Dreamer" was developed to implement the algorithms and explore additional concepts in human-safe robotics. The lower mobile base part of Dreamer, dubbed "Trikey," is the focus of this work. Trikey was iteratively developed, undergoing cycles of concept generation, design, modeling, fabrication, integration, testing, and refinement. Test results showed that Trikey and Dreamer safely performed movements under whole-body compliant control, which is a novel achievement. Dreamer will be a platform for future research and education in new human-friendly traits and behaviors. Finally, this thesis attempts to address a second broad challenge to advancing the field: the lack of standard design methodology for human-centered robots. Based on the experience of building Trikey and Dreamer, a set of consistent design guidelines and metrics for the field are suggested. They account for the complex nature of such systems, which must address safety, performance, user-friendliness, and the capability for intelligent behavior.Mechanical Engineerin
Cooperative control of relay based cellular networks
No full textPhDThe increasing popularity of wireless communications and the higher data
requirements of new types of service lead to higher demands on wireless networks.
Relay based cellular networks have been seen as an effective way to meet users’
increased data rate requirements while still retaining the benefits of a cellular
structure. However, maximizing the probability of providing service and spectrum
efficiency are still major challenges for network operators and engineers because of
the heterogeneous traffic demands, hard-to-predict user movements and complex
traffic models.
In a mobile network, load balancing is recognised as an efficient way to increase
the utilization of limited frequency spectrum at reasonable costs. Cooperative
control based on geographic load balancing is employed to provide flexibility for
relay based cellular networks and to respond to changes in the environment.
According to the potential capability of existing antenna systems, adaptive radio
frequency domain control in the physical layer is explored to provide coverage at
the right place at the right time.
This thesis proposes several effective and efficient approaches to improve
spectrum efficiency using network wide optimization to coordinate the coverage
offered by different network components according to the antenna models and
relay station capability. The approaches include tilting of antenna sectors,
changing the power of omni-directional antennas, and changing the assignment of
relay stations to different base stations. Experiments show that the proposed
approaches offer significant improvements and robustness in heterogeneous traffic
scenarios and when the propagation environment changes. The issue of predicting
the consequence of cooperative decisions regarding antenna configurations when
applied in a realistic environment is described, and a coverage prediction model is
proposed. The consequences of applying changes to the antenna configuration on
handovers are analysed in detail. The performance evaluations are based on a
system level simulator in the context of Mobile WiMAX technology, but the
concepts apply more generally
Um Sistema para o projeto e fabricação de peças mecânicas a distância via internet aderente à norma ISO 14649 (STEP-NC)
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia MecânicaCom o rápido avanço da tecnologia da informação associada à tecnologia da fabricação, os ambientes de manufatura mudaram significativamente nas últimas décadas. A usinagem de alta velocidade, usinagem de ultra-precisão e usinagem de múltiplos eixos tem melhorado a produtividade e a qualidade da manufatura. Além disso, a tecnologia da internet introduziu a e-manufatura (isto é, projetado por qualquer um em qualquer lugar, fabricado por qualquer um em qualquer lugar). A chave para o sucesso da e-manufatura consiste em um fluxo de dados compatíveis e sem brechas na cadeia CAD-CAPP-CAM-CNC. Apesar do avanço nas tecnologias de manufatura, a linguagem que as máquinas de comando numérico utilizam nos dias de hoje (código G # norma ISO 6983) ainda baseia-se nas movimentações da extremidade das ferramentas e no status da máquina, fazendo com que muitas informações acerca do produto sejam perdidas, tornando difícil ou impossível o compartilhamento de tais informações em diferentes áreas da empresa. O padrão ISO 14649 (STEP-NC) fornece um modelo de informações de alto nível referentes ao produto, como por exemplo o uso de features para a modelagem de peças e operações de fabricação, e este padrão tem sido apontado como uma ferramenta adequada para superar os problemas acima mencionados. Assim, para um mercado onde é bastante comum a elevada variabilidade das peças sendo produzidas, a alteração nas features que compõem a peça é mais rápida e fácil do que a alteração do código G para a usinagem da peça, e desta forma capacita-se as empresas a responderem mais rapidamente à mudança no projeto das peças, além de contribuir para acelerar a tomada de decisões referentes à fabricação das peças. Uma outra vantagem do uso de STEP-NC é que a sua estruturação proporciona que organizações de manufatura venham a compartilhar informações de maneira transparente via Internet. Tendo em vista o contexto acima, no presente trabalho foi desenvolvido um protótipo de um sistema computacional CAD/CAPP/CAM voltado à manufatura remota de peças mecânicas de característica prismática utilizando a Internet como meio de comunicação, sendo completamente aderente ao padrão ISO 14649. No sistema desenvolvido foram disponibilizadas inúmeras features para o usuário remoto, incluindo não apenas superfícies com características prismáticas, mas também elementos curvos como fundos abaulados de cavidades. Um dos módulos do sistema verifica se a peça criada pelo usuário é válida do ponto de vista de fabricabilidade com as ferramentas disponíveis. Além disso, o sistema identifica se a peça pode ser fabricada em uma máquina de comando numérico de três eixos, e no caso de impossibilidade o sistema informa o usuário o que causou a não-fabricabilidade. Finalmente, o sistema gera automaticamente o arquivo físico no formato STEP (padrão ISO 10303 parte 21), o qual é disponibilizado para o usuário via Internet, podendo ele efetuar uma simulação gráfica dos movimentos das ferramentas usinando a peça, tendo o arquivo físico como entrada. Até o momento não foi desenvolvido nenhum sistema computacional que disponibilize tal arquivo gratuitamente na Internet, e consequentemente o sistema desenvolvido neste trabalho contribui para uma maior disseminação do padrão STEP-NC, além do fato que o arquivo gerado poderá ser utilizado em máquinas CNC reais compatíveis com o formato STEP parte 21.With the rapid advancement of information technology associated with manufacturing technology, manufacturing environments have changed significantly in recent decades. High speed machining, ultra-precision machining, and multi-axis machining have improved manufacturing productivity and quality. In addition, Internet technology has introduced e-manufacturing (i.e., designed by anyone anywhere, manufactured by anyone anywhere). The key to the success of e-manufacturing consists of compatible data stream with no gaps in the CAD-CAPP-CAM-CNC chain. Despite advances in manufacturing technologies, the language that are used by numerical control machines today (i.e. G-code - ISO 6983 standard) is still based on the movements of the end of the tools and on the machine status, causing the loss of much information about the product, making it difficult or impossible to share such information in different areas of the company. The ISO 14649 (STEP-NC) standard provides a model of high-level information about the product, such as the use of features for the modeling parts and manufacturing operations, and this standard has been recommended as a suitable tool to overcome the aforementioned problems. Thus, for a market where it is quite common the high variability of parts being produced, the change in features that compose the part is faster and easier than changing the G code for machining the part, and thus companies are enabled to respond more quickly to the change in part design, besides helping to accelerate decision-making related to the manufacture of parts. Another advantage of using STEP-NC is that its structure enables manufacturing organizations to share information seamlessly via the Internet. Given the above context, in the present research work a prototype CAD/CAPP/CAM computer system was developed for the remote manufacture of mechanical prismatic mechanical parts using the Internet as a means of communication, completely compliant with the ISO 14649 standard. In the developed system many features are provided to the remote user, including not only surfaces with prismatic features, but also curved elements like general cavities. One of the modules of the system verifies whether the part created by the user is valid from the standpoint of manufacturability with the tools available. In addition, the system identifies whether the part can be manufactured in a numerical control machine with three axes, and if that is not feasible, the system informs the user the cause of non-manufacturability. Finally, the system generates automatically the physical STEP file (ISO 10303 Part 21), which is provided to the user via the Internet, and he can perform a graphic simulation of the movement of the tools machining the part, having the physical file as input. So far no computer system was developed that provides such a file for free on the Internet, and therefore the system developed in this work contributes to a further spread of the STEP-NC standard, plus the fact that the generated file can be used in real CNC machines compatible with the STEP part 21 format
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