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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
311

DISCRETE COMPLIANT MOTION PLANNING SYSTEM FOR ROBOTIC ASSEMBLY

Yang, Fan January 2009 (has links)
This dissertation focuses on compliant motion planning designed for robotic assembly. A Discrete Complaint Motion Planner (DCMP) reacts to detected discrete contact state transitions and issues compliant motion command to the underlying continuous robot system. It consists of a Qualitative Contact Model, a Compliant Motion Strategy Planner (CMSP) and a Compliant Motion Command Planner (CMCP).How to model and characterize a contact state is a major issue. In this dissertation, contact states are described using the qualitative configuration representation called Feature Interaction Matrix (FIM). A FIM encodes not only the contact information but also the relative configuration between two polyhedral parts. This FIM-based qualitative contact state model has several contributions: 1) an optimization-based approach is developed to verify the hypothetical states in FIM; 2) penetration check for hypothetical contact states through constraint satisfaction is simple and fast; 3) spatial adjacency can be easily determined using convex cone techniques; 4) a generate-and-test method is proposed to expand qualitative states in FIM; 5) compliant motion parameters are derived by an optimization method.The qualitative contact states and how they are connected is modeled with an adjacency graph/sub-graph, where nodes represent qualitative contact states and spatially adjacent contact states are connected by arcs. Each arc represents a desired contact state transition. The CMSP receives contact state transition event from an on-line estimator, then computes/checks the assembly strategy and issues the next desired contact state transition to the CMCP. The compliant motion strategy is computed using graph-search techniques with the automatic construction of the adjacency graph/sub-graph. The CMSP integrate hypotheses generation, hypotheses verification, spatial adjacency and graph search algorithms.When the next desired contact state transition is received, the CMCP computes the compliant motion parameters that are issued to the underlying continues robot system to achieve the desired contact state transition. The generation of motion parameters is defined as an optimization problem and an algorithm is developed to solve it.The DCMP in this dissertation considers both 3D translational and 3D rotational motions. Experiments are carried out to demonstrate the feasibility of the approach for the automatic assembly of polyhedral parts.
312

Knowledge creation within an innovative unit : A case study of Robotic Mowers

Hadmark, Julia, Nilsson, Elin January 2008 (has links)
Problem Knowledge is becoming ever more vital in today’s economy and organisations are realising the need to act on the advantages it provides. Knowledge is complex and contradictory, making it difficult to be created and managed by organisations. Purpose The purpose of this research is to see how knowledge is created and subsequently managed within an environment characterised by progress and innovation, and to identify the most problematic areas in knowledge creation processes as well as suggest improvements. Method Overall, qualitative methods were used in this study. In-depth interviews were conducted with management level within three product development units, two of these were only used for support to the third and main case, Robotic Mowers. Issues of trustworthiness and ethical implications were confronted in order to provide the most advantageous method to conduct the study. Result Knowledge creation at Robotic Mowers originates from both external and internal sources. The most important external source and activity to create knowledge are suppliers/consultants and the most important internal sources is the use of tests. Further, the unit has a highly informal approach to the creation of knowledge and the management of it. Support to knowledge creation is mainly found in cultural aspects. Conclusion The unit’s knowledge creation is dependent on informal and unstructured interaction among group members and to external parties. Overall, low managerial control is exercised and the group has developed a strong culture that enhances informal ways of knowledge creation and its management. The main problem of knowledge creation is that the group fails to realise a long-term need, which is revealed through inadequate efforts in trying to turn tacit knowledge into explicit knowledge.
313

Lyapunov-based Control Approaches for Networked Single and Multi-agent Systems with Communication Constraints

Sheng, Long 25 November 2010 (has links)
Networked control systems (NCSs) are feedback control systems with the feedback control loops closed via network. The origin of the term NCSs is from industrial systems where the plant and controller are often connected through networks. The applications of NCSs cover a wide range of industries, for example, manufactory automation, domestic robots, aircraft, automobiles and tele-operations. The research activities in NCSs are focused on the following three areas: control of networks, control over networks and multi-agent systems. Control of networks is mainly concerned with the problem of how to efficiently utilize the network resource by controlling and routing the network data flows. Control over networks is mainly concerned with the design of feedback control strategies of control systems in which signals are transmitted through unreliable communication links. Multi-agent systems deal with two problems: how the topology of the network connections between each component influences global control goals and how to design local control law describing the behavior of each individual to achieve the global control goal of the whole systems. The objective in this thesis is to deal with control over networks and multi-agent systems. The most challenging problem in the control over networks field is that the unreliable communication channels can degrade system performance greatly. The main unreliable properties of networks are delays and packet loss. In order to deal with this problem, a Lyapunov-based method has been used to design the sampled-data stabilization control strategy for a networked single system by choosing proper delay and packet loss dependent Lyapunov functional candidates. Linear matrix inequality techniques have been used to find the sufficient and necessary conditions for the controller design. Furthermore, the consensus formation control problem of multiple robotic vehicle systems has been investigated. The consensus-based design scheme has been applied to the formation control of multiple wheeled mobile-robot group with a virtual leader. A novel delay-dependent Lyapunov functional candidate has been constructed to investigate the convergence of the system states. The proposed control strategy is experimentally implemented for multiple wheeled mobile robots under neighbor-to-neighbor information exchange with group communication delays involved. In conclusion, through the simulation results and experimental validations, the proposed new Lyapunov-based control methods can effectively deal with the networked control systems discussed in this thesis.
314

Robot based 3D welding for jet engine blade repair and rapid prototyping of small components

Thukaram, Santosh Kumar 22 November 2010 (has links)
Aero engines are made up of a large number of blades which are subject to wear and damage. They are expensive and must be repaired wherever possible. Engines also have small components which are required in small numbers that need to be developed rapidly. The first part of this research work focuses on developing a robust automated blade repair method using robotic welding. Optimal weld parameters were developed for build-up of edges having different thicknesses. Samples with varying Current and varying travel speed were produced and their micro hardness values were compared. Blade profiles were welded upon. The second part involves a methodology for producing small components using rapid prototyping (RP) techniques. This part involves use of 3D robotic welding for layered manufacturing. Tensile samples produced using the metal RP method were tested and results were found to be well above the minimum cast specifications for the given material.
315

A robotic microscope for 3D time-lapse imaging of early stage axolotl salamander embryos

Crawford-Young, Susan J. 27 April 2007 (has links)
A robotic microscope was designed using a microcontroller to take time-lapse digital photographs of developing salamander embryos. The microcontroller operated three stepper motors to control three-axis movement accurately, and two six mega-pixel digital cameras to capture through-focus time-lapse digital pictures of six views of Ambystoma mexicanum embryos (axolotl, a salamander). The device is designed to take images every five minutes for 80 hours of early development, from fertilization to stage 20, when the neural tube closes to form the brain and spinal column. Techniques to enhance the embryo images were investigated including image fusion to get in-focus views from a stack of images. In the early embryo surface epithelial cells differentiate to form neural tissue and external skin tissue. Observing the whole embryo surface at cellular level will give a better idea of the stress and strain each cell undergoes and what physical forces are involved in cell differentiation.
316

A Proactive Risk-Aware Robotic Sensor Network for Critical Infrastructure Protection

McCausland, Jamieson 17 December 2013 (has links)
In this thesis a Proactive Risk-Aware Robotic Sensor Network (RSN) is proposed for the application of Critical Infrastructure Protection (CIP). Each robotic member of the RSN is granted a perception of risk by means of a Risk Management Framework (RMF). A fuzzy-risk model is used to extract distress-based risk features and potential intrusion-based risk features for CIP. Detected high-risk events invoke a fuzzy-auction Multi-Robot Task Allocation (MRTA) algorithm to create a response group for each detected risk. Through Evolutionary Multi-Objective (EMO) optimization, a Pareto set of optimal robot configurations for a response group will be generated using the Non-Dominating Sorting Genetic Algorithm II (NSGA-II). The optimization objectives are to maximize sensor coverage of essential spatial regions and minimize the amount of energy exerted by the response group. A set of non-dominated solutions are produced from EMO optimization for a decision maker to select a single response. The RSN response group will re-organize based on the specifications of the selected response.
317

Robot based 3D welding for jet engine blade repair and rapid prototyping of small components

Thukaram, Santosh Kumar 22 November 2010 (has links)
Aero engines are made up of a large number of blades which are subject to wear and damage. They are expensive and must be repaired wherever possible. Engines also have small components which are required in small numbers that need to be developed rapidly. The first part of this research work focuses on developing a robust automated blade repair method using robotic welding. Optimal weld parameters were developed for build-up of edges having different thicknesses. Samples with varying Current and varying travel speed were produced and their micro hardness values were compared. Blade profiles were welded upon. The second part involves a methodology for producing small components using rapid prototyping (RP) techniques. This part involves use of 3D robotic welding for layered manufacturing. Tensile samples produced using the metal RP method were tested and results were found to be well above the minimum cast specifications for the given material.
318

Development of a Robotic Device for the Physical Training of Human Upper Extremity

Ramos, Jorge Adrian 03 October 2013 (has links)
This thesis focuses on the development of a robotic device to be used in parallel with observational learning techniques for facilitating the recovery of the upper limb in post-stroke patients. It has been shown in the existing observational learning literature that observational practice for the execution of goal-directed single arm movements can engage the mirror neuron system and motor areas involved in learning motor actions. On the other hand, robotic-based therapy protocols have proven successful in which participants are able to learn the required perception-action skill. However, robotics have not been overly successful in the generalization of learning to other tasks and this is an essential aspect on improving performance on Activities of Daily Life (ADL). Observational learning of motor skills has been shown to produce transfer across limbs and generalization across muscle groups in the same limb, as well as transfer to perceptual tasks. Therefore, our long-term hypothesis is that a combination of interactive robotics and action observation techniques might offer a greater benefit regarding transfer to ADLs in comparison to pure robotic training. The results from this research broaden the theoretical understanding of observational learning and drive the future development of rehabilitation protocols using the combination of robotic and observational learning techniques. We hypothesize that if the application of these techniques, for non-stroke individuals, yield benefits for the learning of motor/skill actions, then such paradigm will serve as a foundation in the future development of methods for facilitating the recovery of upper limb function after stroke.
319

A robotic microscope for 3D time-lapse imaging of early stage axolotl salamander embryos

Crawford-Young, Susan J. 27 April 2007 (has links)
A robotic microscope was designed using a microcontroller to take time-lapse digital photographs of developing salamander embryos. The microcontroller operated three stepper motors to control three-axis movement accurately, and two six mega-pixel digital cameras to capture through-focus time-lapse digital pictures of six views of Ambystoma mexicanum embryos (axolotl, a salamander). The device is designed to take images every five minutes for 80 hours of early development, from fertilization to stage 20, when the neural tube closes to form the brain and spinal column. Techniques to enhance the embryo images were investigated including image fusion to get in-focus views from a stack of images. In the early embryo surface epithelial cells differentiate to form neural tissue and external skin tissue. Observing the whole embryo surface at cellular level will give a better idea of the stress and strain each cell undergoes and what physical forces are involved in cell differentiation.
320

Configurable Robot Base Design For Mixed Terrain Applications

Bayar, Gokhan 01 August 2005 (has links) (PDF)
Mobile robotics has become a rapidly developing field of interdisciplinary research within robotics. This promising field has attracted the attention of academicy, industry, several government agencies. Currently from security to personal service mobile robots are being used in a variety of tasks. The use of such robots is expected to only increase in the near future. In this study, it is aimed to design and manufacture a versatile robot base. This base is aimed to be the main driving unit for various applications performed both indoors and outdoors ranging from personal service and assistance to military applications. The study does not attempt to individually address any specific application, indeed it is aimed to shape up a robotic module that can be used in a wide range of application on different terrain with proper modification. The robot base is specifically designed for mixed terrain applications, yet this study attempts to provide some guidelines to help robot designers. The manufactured robot base is tested with tracks, wheels, and with both tracks and wheels, results are provided as guidelines to robot designers. Last but no the least, this study aims to obtain the know-how of building functional and flexible robots in Turkey by facilitating local resources as much as possible.

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