Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2007. / Thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering Science (Mechanical) at the University of Stellenbosch. / ENGLISH ABSTRACT: This thesis examines the development of a specialized, high-speed bearing in order to reduce vibration levels, reduce cutting times and increase blade stability during diamond sawing. The sawing process is required to be smooth, straight and unhindered – a task which is made difficult by the extreme hardness of the diamond as well as unseen grains which could potentially ruin the cut by deflecting the blade. This has an adverse effect on the quality of the cut and the yield obtained from the stone. The current equipment used for diamond sawing is very basic and a significant improvement can be made in terms of quality and sawing speed with the addition of an improved bearing. An aerostatic bearing was designed in order to achieve lower vibration levels and increased spindle speeds. A speed of 18 500 rpm was achieved with this bearing. A numerical model of the bearing was built with the aim of predicting the bearing’s dynamic behaviour. A finite element method (FEM) analysis was done to confirm the rigid body assumption made. Experimental modal analysis (EMA) was done to determine the frequencies and damping ratios of the natural modes of the rotor. The model was seen to predict the frequencies of the modes to within 6%. This model would be used for future design work to ensure that the frequencies of these modes are designed outside of the operating speed range of the aerostatic bearing. Tests were done to compare the vibration levels between the conventional machine and the aerostatic machine during sawing. The overall RMS acceleration was reduced by 70% on the housing of the aerostatic machine and by 50% on the diamond clamp. / AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek die ontwikkeling van ‘n gespesialeerde, hoë-spoed laer om vibrasie en sny tye te verminder, asook om lem stabilitiet te verhoog in die diamant sny proses. Die sny proses moet glad, reguit en akkuraat wees, maar dit is nie altyd moontlik nie as gevolg van die variasie in hardheid van die diamant asook die naat in die daimant wat die lem maklik kan laat afwyk. Hierdie het ‘n negative effek op die kwalitiet van die snit. Die konvensionele diamant saag masjien is baie eenvoudig en ‘n groot verbetering in die snit kwalitiet en lemspoed is moontlik as ‘n nuwe laer ontwerp en implementeer kan word. ‘n Aerostatiese laer en rotor is ontwikkel om die vibrasie te verminder en die lemspoed to verhoog. ‘n Lemspoed van 18 500 rpm was verkry met die nuwe laer. ‘n Numeriese model is ontiwkkel om die beweging van die rotor dinamies te bereken. Die Eindige Element Metode (EEM) is gebruik om te bepaal of die aanname dat die rotor rigied is, wel aanvaarbaar is. Eksperimentele Modale Analise (EMA) is gebuik om die natuurlike frekwensies en die dempingsverhoudings vir die rotor te bepaal. Die model het die frekwensies tot binne 6% van die werklike waardes bereken. Hierdie model sal in die toekoms gebruik kan word vir die ontwerp van aerostatiese laers om te verseker dat die natuurlike frekwensies buite die spoedbereik van die aerostatiese masjien val. Toetse is gedoen om die vibrasievlakke van die huidige en die aerostatise masjien te meet tydens die snyproses. Die totale WGK versnelling het met 70% op die huls van die aerostatiese masjien, en met 50% op die diamant dop, verminder.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The performance of wet cooling towers can be improved by installing spray nozzles that distribute the cooling water uniformly onto the fill whilst operating at a low pressure head. In this thesis, three commercial spray nozzles are experimentally evaluated in terms of flow and pressure loss characteristics as well as water distribution patterns. The results of the evaluation process highlight the need for spray nozzles with enhanced performance characteristics. The theory required to implement the results of the evaluation process in the design of a cooling tower is presented and discussed. A systematic approach to enhance the performance of a spray nozzle through minor alterations is applied to one of the commercial spray nozzles that was evaluated. The fluid dynamics of an orifice nozzle, such as the effect of a change in pressure head, spray angle, spray height, orifice diameter and wall thickness on drop diameter and spray distance, is experimentally investigated and a model with which a spray nozzle can be designed is finally presented. Two prototype spray nozzles show that it is possible to enhance the performance of spray nozzles and thus wet cooling towers by means of the methods presented. / AFRIKAANSE OPSOMMING: Die werkverrigting van natkoeltorings kan verbeter word deur sproeiers te installeer wat die verkoelingswater uniform versprei op die pakking teen 'n lae pomp drukhoogte. In hierdie tesis word drie kommersiële sproeiers eksperimenteel geëvalueer in terme van vloei en drukverlies eienskappe sowel as water verdelings patrone. Die resultate van die evaluasie proses beklemtoon die behoefte aan sproeiers met verbeterde werkverrigtingseienskappe. Die teorie wat benodig word om die resultate van die evaluasie proses te implementeer in die ontwerp van 'n natkoeltoring word bespreek. 'n Stelselmatige benadering om die werkverrigtings van 'n sproeier te verhoog deur klein veranderinge aan die ontwerp aan te bring, word toegepas op een van die sproeiers wat getoets is. Die vloeidinamika van 'n plaatmondstuk, soos die effek van 'n verandering in drukhoogte, sproeihoek, sproeihoogte, gatdiameter en wanddikte op druppel diameter en sproeiafstand, is eksperimenteel ondersoek en 'n model word aangebied waarmee 'n sproeier ontwerp kan word. Twee prototipe sproeiers wys dat dit moontlik is om die werkverrigting van sproeiers, en dus ook natkoeltorings, te verbeter deur die metodes wat in die tesis aangebied word, toe te pas.

Le pré-dimensionnement se situe en amont du processus de conception d'un système : à partir d'un ensemble d'exigences, il consiste à déterminer un ensemble de solutions techniques possibles dans un espace de recherche souvent très grand et structuré par une connaissance partielle et incertaine du futur système et de son environnement. Bien avant de penser au choix définitif des composants et au dimensionnement précis du système complet, les concepteurs doivent s'appuyer sur un premier cahier des charges, des modélisations des principaux phénomènes et divers retours d'expériences pour formaliser des contraintes, faire des hypothèses simplificatrices, envisager diverses architectures et faire des choix sur des données imprécises (i.e. caractérisées sous la forme d'intervalles, de listes de valeurs possibles, etc…). Les choix effectués lors du pré-dimensionnement pouvant être très lourds de conséquences sur la suite du développement, il est primordial de détecter au plus tôt d'éventuelles incohérences et de pouvoir vérifier la satisfaction des exigences dans un contexte incertain. Dans ce travail, une méthodologie de vérification des exigences basée sur l'échange de modèles ensemblistes entre donneurs d'ordre et fournisseurs est proposée. Elle s'inscrit dans le cadre d'un paradigme de conception basé sur la réduction d'incertitudes. Après un travail portant sur la modélisation des systèmes mécatroniques, une attention particulière est portée à la prise en compte d'incertitudes déterministes sur des grandeurs continues : des techniques basées sur l'analyse par intervalles telles que la satisfaction de contraintes (CSP), des calculs d'atteignabilité pour des modèles dynamiques de connaissances ou encore l'identification de modèles de comportements ensemblistes sont ainsi mis en œuvre et développés afin d'outiller la méthodologie proposée et contribuer à répondre à l'objectif d'une vérification à couverture garantie. / The pre-sizing takes place upstream to the process of designing a system: from a set of requirements, it consists in determining a set of possible technical solutions in an often very large search space which is structured by the uncertain and partial knowledge available about the future system and its environment. Long before making the final choice and the final sizing of the system components, the designers have to use specifications, models of the main phenomena, and experience feedbacks to formalize some constraints, make simplifying assumptions, consider various architectures and make choices based on imprecise data (i.e. intervals, finite sets of possible values, etc…). The choices made during the pre-sizing process often involving strong commitments for the further developments, it is very important to early detect potential inconsistencies and to verify the satisfaction of the requirements in an uncertain context. In this work, a methodology based on the exchange of set-membership models between principals and suppliers is proposed for the verification of requirements. This methodology is fully consistent with a design paradigm based on the reduction of uncertainties. After a work dedicated to the modeling of mechatronic systems, a special attention is paid to dealing with deterministic uncertainties affecting continuous values: some techniques based on interval analysis such as constraint satisfaction (interval CSP), reachability computations for knowledge dynamic models or identification of set-membership behavioral models are used and developed, so providing a set of tools to implement the proposed methodology and contribute to reach the goal of a verification with a full and guaranteed coverage.

This thesis focuses on assistive and rehabilitation technology for restoring the function of the hand. It presents three different approaches to assistive technology: one in the form of an orthosis, one in the form of a brain-computer interface combined with functional electrical stimulation and finally one totally aiming at rehabilitating the nervous system by restoring brain function using the concept of neuroplasticity. The thesis also includes an epidemiological study based on statistics from the Swedish Hospital Discharge Register and a review on different methods for assessment of hand function. A novel invention of an orthosis in form of a light weight glove, the SEM (Soft Extra Muscle) glove, is introduced and described in detail. The SEM glove is constructed for improving the grasping capability of a human independently of the particular task being performed. A key feature is that a controlling and strengthening effect is achieved without the need for an external mechanical structure in the form of an exoskeleton. The glove is activated by input from tactile sensors in its fingertips and palm. The sensors react when the applied force is larger than 0.2 N and feed a microcontroller of DC motors. These pull lines, which are attached to the fingers of the glove and thus work as artificial tendons. A clinical study on the feasibility of the SEM glove to improve hand function on a group of patients with varying degree of disability has been made. Assessments included passive and active range of finger motion, flexor muscle strength according to the Medical Research Council (MRC) 0-5 scale, grip strength using the Grippit hand dynamometer, fine motor skills according to the Nine Hole Peg test and hand function in common activities by use of the Sollerman test. Participants rated the potential benefit on a Visual Analogue Scale. A prototype for a system for combining BCI (Brain-Computer Interface) and FES (Functional Electrical Stimulation) is described. The system is intended to be used during the first period of recovery from a TBI (Traumatic Brain Injury) or stroke that have led to paresis in the hand, before deciding on a permanent system, thus allowing the patients to get a quick start on the motor relearning. The system contains EEG recording electrodes, a control unit and a power unit. Initially the patients will practice controlling the movement of a robotic hand and then move on to controlling pulses being sent to stimulus electrodes placed on the paretic muscle. An innovative electrophysiological device for rehabilitation of brain lesions is presented, consisting of a portable headset with electrodes on both sides adapted on the localization of treatment area. The purpose is to receive the outgoing signal from the healthy side of the brain and transfer that signal to the injured and surrounding area of the remote side, thereby having the potential to facilitate the reactivation of the injured brain tissue. The device consists of a control unit as well as a power unit to activate the circuit electronics for amplifying, filtering, AD-converting, multiplexing and switching the outgoing electric signals to the most optimal ingoing signal for treatment of the injured and surrounding area. / <p>QC 20130403</p>

Cette thèse se focalise sur l’application d’une approche topologique pour la modélisation des systèmes mécatroniques. Cette approche permet de dissocier la topologie et la physique afin d’avoir un modèle unifié de représentation de toute la physique d’un système mécatronique. L’approche topologique développée est codée sous le langage MGS (Modèle Général de Système). Ce langage intègre de nouveaux types de valeurs appelées les collections topologiques. Les collections topologiques permettent la représentation de l'état d'un système dynamique et elles sont manipulées par des transformations. Dans cette approche, les collections topologiques sont utilisées pour présenter la topologie du système à étudier c’est à dire la loi d’interconnexion de ses différents composants et les transformations pour spécifier la loi de comportement locale de chacune de ces composantes. Cette approche topologique est appliquée tout d’abord aux structures de barres planes et spatiales et elle est généralisée par la suite aux structures de poutres planes et spatiales. Finalement, elle est étendue à la modélisation des systèmes mécaniques plus complexes en étudiant le cas des structures piézoélectriques (stack piézoélectrique et treillis piézoélectrique) et le cas d’un réducteur simple étage à denture droite. Étant donné les bons résultats obtenus, il serait intéressant d’étendre ce travail aux systèmes mécatroniques plus complexes en intégrant l’informatique et l’automatique. / This thesis focuses on the application of a topological approach for the modeling of mechatronic systems. This approach makes it possible to separate the topology and the physics in order to have a unified representation model for all the physics of mechatronic systems. The developed topological approach is coded in the MGS language (General System Model). This language includes new types of values called topological collections. Topological collections allow the representation of the state of a dynamic system and they are manipulated by transformations. In this approach, the topological collections are used to present the topology of the studied system that is to say the interconnection law of its components and transformations are used to specify the local behavior law of each of these components. First of all, this topological approach is applied to planar and space bar structures and then generalized to planar and space beam structures. Finally, it is extended to the modeling of complex mechanical systems by studying the case of piezoelectric structures (piezoelectric stack and piezoelectric truss structure) and the case of a single stage spur gear. Since this work achieved good reliable results, it would be interesting to extend this approach to more complex mechatronic systems by integrating computers and automatic.

Les systèmes modernes sont caractérisés par l’intégration de plusieurs composants de technologies diverses interagissant dans le but d’offrir de plus en plus de fonctionnalités aux utilisateurs. La complexité croissante dans ces systèmes pluridisciplinaires dits mécatroniques nécessite la mise en place de nouveaux processus, outils et méthodes pour la conception, l’analyse et la validation de ces derniers en respectant les contraintes de coût et de délais imposés par la concurrence. Ces systèmes doivent également satisfaire des contraintes de fiabilité et surtout de sûreté de fonctionnement. Seule une intégration du processus d’analyse de sûreté de fonctionnement tout au long du processus de développement peut assurer la satisfaction de ces contraintes de manière optimale.Les travaux de cette thèse ont pour objectif de contribuer à l’intégration des analyses de sûreté de fonctionnement dans le processus d’ingénierie système basée sur SysML afin de rendre ces analyses plus rapides et plus efficaces. Pour ce faire, nous avons traité les axes suivants : la formalisation d’une méthodologie de conception basée sur SysML et qui sera le support des analyses de sûreté de fonctionnement ; l’extension du langage SysML afin de pouvoir intégrer des spécificités des systèmes mécatroniques ainsi que des aspects de sûreté de fonctionnement dans le modèle système; l’exploration automatique des modèles SysML afin d’en extraire les données nécessaires pour l’élaboration des artefacts de la SdF et la génération (semi)/automatique de ces derniers (FMEA et FTA). Nous avons également intégré la vérification formelle d’exigences de sûreté de fonctionnement.Cette méthodologie nommée SafeSysE a été appliquée sur des cas d’étude du domaine de l’aéronautique : EMA (Electro-Mechenical Actuator) et WBS (Wheel Brake System). / Modern systems are getting more complex due to the integration of several interacting components with different technologies in order to offer more functionality to the final user. The increasing complexity in these multi-disciplinary systems, called mechatronic systems, requires new appropriate processes, tools and methodologies for their design, analysis and validation whilst remaining competitive with regards to cost and time-to-market constraints.The main objective of this thesis is to contribute to the integration of safety analysis in a SysML-based systems engineering approach in order to make it more efficient and faster. To achieve this purpose, we tackled the following axes: formalizing a SysML-based design methodology that will be the support for safety analyses; providing an extension of SysML in order to enable the integration of specific needs for mechatronic systems modeling as well as safety concepts in the system model; allowing the automated exploration of the SysML models in order to extract necessary information to elaborate safety artefacts (such as FMEA and FTA) and the semi-automated generation of the latters. We have also integrated formal verification to verify if the system behaviors satisfy some safety requirements.The proposed methodology named SafeSysE was applied to case studies from the aeronautics domain: EMA (Electro Mechanical Actuator) and WBS (Wheel Brake System).

Hybrid models are those containing continuous and discontinuous behaviour. In constructing dynamic systems models, it is frequently desirable to abstract rapidly changing, highly nonlinear behaviour to a discontinuity. Bond graphs lend themselves to systems modelling by being multi-disciplinary and reflecting the physics of the system. One advantage is that they can produce a mathematical model in a form that simulates quickly and efficiently. Hybrid bond graphs are a logical development which could further improve speed and efficiency. A range of hybrid bond graph forms have been proposed which are suitable for either simulation or further analysis, but not both. None have reached common usage. A Hybrid bond graph method is proposed here which is suitable for simulation as well as providing engineering insight through analysis. This new method features a distinction between structural and parametric switching. The controlled junction is used for the former, and gives rise to dynamic causality. A controlled element is developed for the latter. Dynamic causality is unconstrained so as to aid insight, and a new notation is proposed. The junction structure matrix for the hybrid bond graph features Boolean terms to reflect the controlled junctions in the graph structure. This hybrid JSM is used to generate a mixed-Boolean state equation. When storage elements are in dynamic causality, the resulting system equation is implicit. The focus of this thesis is the exploitation of the model. The implicit form enables application of matrix-rank criteria from control theory, and control properties can be seen in the structure and causal assignment. An impulsive mode may occur when storage elements are in dynamic causality, but otherwise there are no energy losses associated with commutation because this method dictates the way discontinuities are abstracted. The main contribution is therefore a Hybrid Bond Graph which reflects the physics of commutating systems and offers engineering insight through the choice of controlled elements and dynamic causality. It generates a unique, implicit, mixed-Boolean system equation, describing all modes of operation. This form is suitable for both simulation and analysis.

Nas linhas de montagens industriais, a fim de atender os requisitos de mercado e de ciclo de vida dos produtos, os requisitos de manufatura e as novas tecnologias presentes nos equipamentos indicam a necessidade de reconfiguração e reprogramação do fluxo de processos de forma cada vez mais frequente. Atualmente, uma das opções para implantar um sistema de manufatura flexível, capaz de reagir às mudanças que ocorrem no processo de fabricação, consiste na utilização de tecnologias que forneçam maior flexibilidade, capacidade de reutilização e menor custo. Neste contexto, os robôs baseados em módulos mecatrônicos podem ser uma alternativa em relação aos manipuladores convencionais, pois apresentam uma estrutura cinemática flexível, podendo se adaptar às mudanças das linhas de produção, nas indústrias de manufatura. O presente trabalho apresenta uma proposta para o desenvolvimento de módulos mecatrônicos para a montagem de robôs manipuladores modulares, baseada em um procedimento sequencial composto das seguintes etapas: (a) elaboração do projeto mecânico modular; (b) projeto dos sistemas eletrônicos e de atuação para cada módulo; (c) definição dos agentes mecatrônicos; e (d) descrição dos modelos matemáticos e os algoritmos de comunicação entre módulos mecatrônicos. Nesta pesquisa apresenta-se um estudo no qual os módulos mecatrônicos utilizam energia de origem pneumática e são constituídos por unidades independentes utilizadas na formação de estruturas robotizadas as quais permitem a montagem de diferentes arquiteturas. Um estudo de caso é apresentado para ilustrar a construção de um robô modular cartesiano. Este robô é construído por meio de acoplamentos de módulos mecatrônicos e gerenciado pela associação dos agentes mecatrônicos presentes no sistema, os quais equacionam a cinemática da estrutura formada, planejam a trajetória a ser executada e disponibilizam informações que podem ser utilizadas para o controle, supervisão e proteção do sistema por exemplo. A arquitetura proposta permite a reconfiguração dos recursos de hardware e software, de forma que todos os módulos do robô podem ser reorganizados e/ou substituídos, dependendo da função, aplicação para as quais se destinam. / In industrial manufacturing lines, in order to meet the market requirements and life cycle of manufactured products, the manufacturing requirements and the present of new technologies in equipment, indicate the need for reconfiguration and reprogramming processes, which are becoming more frequent. Currently, one of the options to deploy a flexible manufacturing system that is capable of reacting to changes in the manufacturing process is the use of technologies that provide greater flexibility, reusability and lower cost. In this context, the robots based on mechatronic modules can be an alternative to conventional manipulators, since they have a flexible kinematic structure, which can adapt to the changes in production lines in manufacturing industries. This paper presents a proposal for the development of mechatronic modules for assembly robots modular manipulators, based on a sequential procedure consists of the following steps: (a) Develop a modular mechanical design; (b) design electronic systems and operations for each module; (c) definition of mechatronic agents; and (d) a description of mathematical models and algorithms of the communication between mechatronic modules. This research presents a study where the mechatronic modules use pneumatic energy and consist of independents units used in the formation of robotic structures, thus allowing the assembly of different architectures. In a case study, the construction of a modular Cartesian robot is presented. This robot is built by mounting the mechatronic modules and is managed by mechatronic agents present in the system (Multi-Agent System). This system obtains the kinematic equations of the formed structure, realize the path planning, and provide information that can be used for the control, like supervision and protection system for example. The proposed architecture allows reconfiguration of hardware and software resources, so that all robot modules can be rearranged and/or replaced, depending on the function or, the final application.

This thesis presents the design and development of a unique omni-directional platform known as the Omnibot which was built in the Mechatronic and Robotic Systems Laboratory at UOIT. The Omnibot's layout is novel because its drive axes do not intersect with the geometric center of the body, which is typical for omni-directional platforms using segmented omni-directional wheels. This design enables the center of mass to be lower in the design and increases the stability. A suspension system was designed for each of the four wheels to limit vibrations and to ensure contact between the wheels and operating surface. The Omnibot was built to modularly support many systems, including a robot arm, without altering the mechanical design of the frame. Two control modes were developed: local and global. Commands to drive the Omnibot can be received from either a joystick that can be directly interfaced with the controller or with commands that are sent from other systems that are either on or o of the Omnibot. Both control modes require encoder feedback to ensure commanded velocities are being executed as specified. Global control requires feedback from an indoor localization system to determine the Omnibot's pose. Early implementation of the localization system is discussed. An open source robotics software, known as Robot Operating System (ROS) was selected for implementation of the Omnibot systems. ROS serves as a middleware which allows components, such as the localization system and remote desktop, to communicate with each other through a decoupled messaging system. ROS is modular and exible, allowing for easy adaptation of future components. Test results of the Omnibot in operation are presented.

This thesis presents a novel design paradigm of mobile robots: the Hybrid Mobile Robot system. It consists of a combination of parallel and serially connected links resulting in a hybrid mechanism that includes a mobile robot platform for locomotion and a manipulator arm for manipulation, both interchangeable functionally. All state-of-the-art mobile robots have a separate manipulator arm module attached on top of the mobile platform. The platform provides mobility and the arm provides manipulation. Unlike them, the new design has the ability to interchangeably provide locomotion and manipulation capability, both simultaneously. This was accomplished by integrating the locomotion platform and the manipulator arm as one entity rather than two separate and attached modules. The manipulator arm can be used as part of the locomotion platform and vice versa. This paradigm significantly enhances functionality. The new mechanical design was analyzed with a virtual prototype that was developed with MSC Adams Software. Simulations were used to study the robot’s enhanced mobility through animations of challenging tasks. Moreover, the simulations were used to select nominal robot parameters that would maximize the arm’s payload capacity, and provide for locomotion over unstructured terrains and obstacles, such as stairs, ditches and ramps. The hybrid mobile robot also includes a new control architecture based on embedded on-board wireless communication network between the robot’s links and modules such as the actuators and sensors. This results in a modular control architecture since no cable connections are used between the actuators and sensors in each of the robot links. This approach increases the functionality of the mobile robot also by providing continuous rotation of each link constituting the robot. The hybrid mobile robot’s novel locomotion and manipulation capabilities were successfully experimented using a complete physical prototype. The experiments provided test results that support the hypothesis on the qualitative and quantitative performance of the mobile robot in terms of its superior mobility, manipulation, dexterity, and ability to perform very challenging tasks. The robot was tested on an obstacle course consisting of various test rigs including man–made and natural obstructions that represent the natural environments the robot is expected to operate on.