Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Minimally Invasive Surgery (MIS) in human beings is performed by making small incisions in the abdominal region of the patient and inflating the abdominal cavity with CO2. This procedure enables the surgeon to manipulate long rigid surgical instruments inside the patient in order to perform the surgery. Unfortunately the current methods of insertion and assembly of MIS instruments limit the surgeon to only five (of a possible seven) Degrees of Freedom (DOF). Along with this, the surgeon’s movements are mirrored (called the Fulcrum effect) and scaled around the point of incision. Minimally invasive surgical robots attempt to alleviate these drawbacks by eliminating the Fulcrum effect, as well as improving dexterity and accuracy. These robots’ abilities to improve the surgeon’s hand-eye coordination, enables the surgeon to perform surgeries using their natural movements with reduced fatigue. As a result of this, the risk to both patient and surgeon is reduced. Existing MIS robotic systems are extremely expensive and large, and as a result they are not widely used. In this thesis a new, lower cost, seven DOF robotic manipulator is further developed. The thesis focuses on the external three DOF Secondary Slave Manipulator (SSM) and combines it with the Primary Slave Manipulator (PSM) that was developed by a previous Masters student. Tests done on the SSM showed that the manipulator has a minimum resolution of 0.7 ± 0.2 mm (mean ± standard deviation) on the shoulder joint’s yaw rotation and 0.5 ± 0.2 mm in pitch rotation. The linear actuator used for insertion has a minimum resolution of 0.2 ± 0.2 mm. A strength test was also conducted and showed that the manipulator is easily capable of producing a 10 N actuation force as required during Minimally Invasive Robotic Surgery (MIRS) procedures. In conclusion the complete system has potential as a viable alternative to the existing systems due to its accuracy and lower cost. Future work will include the development of a user interface and control system for the complete robot. / AFRIKAANSE OPSOMMING: Minimaal Indringende Chirurgie (MIC) op mense word uitgevoer deur klein insnydings in die pasiënt se buik te maak en dan die abdominale holte met CO2 te vul. Dit stel die chirurg in staat om lang, onbuigbare instrumente binne die pasiënt te manipuleer om sodoende die operasie uit te voer. Die manier waarop die MIC instrument ontwerp is en die pasiënt binnegaan, laat egter slegs vyf vryheidsgrade toe, terwyl die chirurg self sewe vryheidsgrade in sy handbewegings het. Verder veroorsaak hierdie instrumente ook dat die chirurg se aksies in spieëlbeeld vertolk word (Fulcrum effek) en geskaleer is. Chirurgiese robotika poog om hierdie nadele teen te werk deur die Fulcrum effek te verwyder, en ook om handvaardigheid en akkuraatheid te bevorder. Die robot se potensiaal om die chirurg se hand-oog koӧrdinasie te verbeter, maak dit moontlik vir die chirurg om op ’n meer natuurlike en gemaklike manier te werk te gaan en bring minder vermoeienis mee. Dit verminder die risiko’s vir beide die pasiënt en die chirurg. Bestaande robotiese stelsels is egter baie duur en groot, en word dus nie meer algemeen gebruik nie. In hierdie tesis word ‘n nuwe sewe-vryheidsgraad robotiese manipuleerder ontwikkel. Die tesis fokus op die eksterne drie-vryheidsgraad Sekondêre Slaaf Manipuleerder (SSM) en kombineer dit met die Primêre Slaaf Manipuleerder (PSM) wat deur ʼn vorige Meestersstudent ontwikkel is. Toetse wat uitgevoer is op die SSM het getoon dat dit ’n minimum resolusie van 0.7 ± 0.2 mm (gemiddeld ± standaard afwyking) op die skouer se afwyking en 0.5 ± 0.2 mm om die onderskeie skouer aslyne toon. Die linieêre aktueerder wat vir inlassing gebruik word het ’n minimum resolusie van 0.2 ± 0.2 mm. ’n Sterktetoets is uitgevoer en het getoon dat die manipuleerder maklik die nodige 10 N krag soos benodig in Minimaal Indringende Robotiese Chirurgie (MIRC) prosedures kan lewer. Ter afsluiting, die volledige stelsel het die potensiaal as lewensvatbare alternatief tot die bestaande stelsels vanweë die akkuraatheid en laer koste verbonde. Toekomstige navorsing kan moontlik die ontwikkeling van ʼn gebruikerkoppelvlak en beheerstelsel vir die volledige robot insluit.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In percutaneous procedures, where the surgeon inserts a needle into a target in the patient, it is challenging to access the target at the rst attempt. Repeated needle insertion attempts are highly undesirable, as they lead to increased theatre time, patient haemorrhage and radiation exposure. The proposal of this thesis was to develop a low-cost system to aid surgeons with the process of positioning and orientating the needle prior to insertion. The proposed system uses a stereo pair of images produced by a standard C-arm uoroscope. By applying computer vision techniques, such as triangulation, the desired needle position and orientation are determined from the set of images. An articulated manipulator is used to position and orientate the needle. The surgeon makes selections on the images, via a graphical user interface (GUI), to indicate the desired position and orientation of the needle. Following these selections, an algorithm determines the necessary angles for the manipulator. The surgeon then positions the manipulator accordingly. Results from tests on a phantom showed the system to be repeatable and accurate to 2 mm. This is less accurate than similar, existing systems which, reported accuracies of 0:25 and 1:21 mm. However, 2 mm accuracy is considered adequate as it allows a range of percutaneous procedures to be performed such as needle biopsy, regional anaesthesia, brachytherapy and percutaneous nephrolithotomy (PCNL). Tests on both a phantom kidney and a porcine kidney indicated that the system can function in a real percutaneous procedure and with an anatomical target. The total cost to develop the prototype system was R15 000. The accuracy of the proposed system and the time to gain access to the target indicate that the system can be a bene cial aid to surgeons when performing percutaneous procedures. As minimal X-ray imaging is required, patients will also be spared excessive radiation exposure and theatre time. / AFRIKAANSE OPSOMMING: In perkutane prosedures, waar die chirurg 'n naald in 'n teiken op die pasiënt invoeg, is dit moeilik om met die eerste probeerslag toegang tot die teiken te bekom. Herhaalde pogings om die naald in te voeg is hoogs ongewens, aangesien dit tot verlengde teatertyd, bloeding by pasinte sowel as stralingsblootstelling lei. 'n Laekostestelsel is ontwikkel om chirurge by te staan met die proses om die naald voor invoeging te plaas en te oriënteer. Die stelsel gebruik 'n paar stereobeelde wat deur 'n standaard-C-arm- uoroskoop voortgebring word. Met behulp van rekenaarsigtegnieke, soos triangulasie, word die gewenste naaldposisie en -oriëntasie uit die stel beelde bepaal. 'n Geartikuleerde manipuleerder word gebruik om die naald te plaas en te oriënteer. Die chirurg voer die vereiste invoerdata deur middel van 'n gra ese gebruikerskoppelvlak (GGK) in, waarna 'n algoritme die vereiste hoeke vir die manipuleerder bepaal. Die chirurg plaas dan die manipuleerder dienooreenkomstig. Die resultate van toetse op 'n fantoom toon dat die stelsel herhaalbaar en tot op 2 mm akkuraat is. Dit is minder akkuraat as soortgelyke, bestaande stelsels, wat 'n akkuraatheid van 0:25 mm en 1:21 mm onderskeidelik aangemeld het. Tog kan akkuraatheid van 2 mm as voldoende beskou word, aangesien dit 'n verskeidenheid perkutane prosedures moontlik maak, soos naaldbiopsies, regionale anestesie, bragiterapie en perkutane nefrolitotomie (PCNL). Toetse op 'n fantoomnier dui daarop dat die stelsel wél in 'n werklike perkutane prosedure kan funksioneer. Toetse op 'n varknier toon dat die stelsel wél ook met 'n anatomiese teiken kan werk. Die totale koste om die prototipe te ontwikkel was R15 000. Die akkuraatheid van die voorgestelde stelsel en die tydsduur om toegang tot die teiken te bekom, dui daarop dat die stelsel 'n nuttige hulpmiddel kan wees vir chirurge wat perkutane prosedures uitvoer. Aangesien minimale Xstraalbeelding vereis word, sal dit pasiënte ook oormatige stralingsblootstelling en verlengde teatertyd spaar.

Cette thèse se concentre sur les interactions émotionnelles en robotique autonome. Le robot doit pouvoir agir et réagir dans un environnement naturel et faire face à des perturbations imprédictibles. Il est donc nécessaire que le robot puisse acquérir une autonomie comportementale à savoir la capacité d'apprentissage et d'adaptation en ligne. En particulier, nous nous proposons d'étudier quels mécanismes introduire pour que le robot ait la capacité de se constituer une perception des objets de son environnement qui puisse être partagée par celle d'un partenaire humain. Le problème sera de faire apprendre à notre robot à préférer certains objets et à éviter d'autres objets. La solution peut être trouvée en psychologie dans ce que l'on appelle "référencement social" ("social referencing") qui consiste à attribuer une valeur à un objet grâce à l'interaction avec un partenaire humain. Dans ce contexte, notre problème est de trouver comment un robot peut apprendre de manière autonome à reconnaître les expressions faciales d'un partenaire humain pour ensuite les utiliser pour donner une valence aux objets et permettre leur discrimination.Nous nous intéresserons à comprendre comment des interactions émotionnelles avec un partenaire peuvent amorcer des comportements de complexité croissante tel que le référencement social. Notre idée est que le référencement social aussi bien que la reconnaissance d'expressions faciales peut émerger d'une architecture sensori-motrice. Sans connaissance de ce que l'autre est, le robot devrait réussir à apprendre des tâches "sociales" de plus en plus complexes. Nous soutenons l'idée que le référencement social peut être amorcé par une simple cascade d'architectures sensori-motrices qui à la base ne sont pas dédiées aux interactions sociales.Cette thèse traite de plusieurs sujets qui ont comme dénominateur commun l'interaction sociale. Nous proposons tout d'abord une architecture capable d'apprendre à reconnaître de manière autonome des expressions faciales primaires grâce à un jeu d'imitation entre une tête expressive et un expérimentateur.Les interactions avec le dispositif robotique commençeraient par l'apprentissage de 5 expressions faciales prototypiques. Nous proposons ensuite une architecture capable de reproduire des mimiques faciales ainsi que leurs différents niveaux d'intensité. La tête expressive pourra reproduire des expressions secondaires par exemple une joie mêlée de colère. Nous verrons également que la discrimination de visages peut émerger de cette interaction émotionnelle à l'aide d'une rythmicité implicite qui se crée entre l'homme et le robot. Enfin, nous proposerons un modèle sensori-moteur ayant la capacité de réaliser un référencement social. Trois situations ont pu être testées: 1) un bras robotique capable d'attraper et de fuir des objets selon les interactions émotionnelles venant du partenaire humain. 2) un robot mobile capable de rejoindre ou d'éviter certaines zones de son environnement. 3) une tête expressive capable d'orienter son regard dans la même direction que l'humain tout en attribuant des valeurs émotionnelles aux objets via l'interaction expressive de l'expérimentateur.Nous montrons ainsi qu'une séquence développementale peut émerger d'une interaction émotionnelle de très bas niveau et que le référencement social peut s'expliquer d'abord à un niveau sensori-moteur sans nécessiter de faire appel à un modèle de théorie de l'esprit. / My thesis focuses on the emotional interaction in autonomous robotics. The robot must be able to act and react in a natural environment and cope with unpredictable pertubations. It is necessary that the robot can acquire a behavioral autonomy, that is to say the ability to learn and adapt on line. In particular, we propose to study what are the mechanisms to introduce so that the robot has the ability to perceive objects in the environment and in addition they can be shared by an experimenter. The problem is to teach the robot to prefer certain objects and avoid other objects. The solution can be found in psychology in the social referencing. This ability allows to associate a value to an object through emotional interaction with a human partner. In this context, our problem is how a robot can autonomously learn to recognize facial expressions of a human partner and then use them to give a emotional valence to objects and allow their discrimination. We focus on understanding how emotional interaction with a partner can bootstrap behavior of increasing complexity such as social referencing. Our idea is that social referencing as well as the recognition of facial expressions can emerge from a sensorimotor architecture. We support the idea that social referencing may be initiated by a simple cascade of sensorimotor architectures which are not dedicated to social interactions. My thesis underlines several topics that have a common denominator: social interaction. We first propose an architecture which is able to learn to recognize facial expressions through an imitation game between an expressive head and an experimenter. The robotic head would begin by learning five prototypical facial expressions. Then, we propose an architecture which can reproduce facial expressions and their different levels of intensity. The robotic head can reproduce expressive more advanced for instance joy mixed with anger. We also show that the face detection can emerge from this emotional interaction thanks to an implicit rhythm that is created between human partner and robot. Finally, we propose a model sensorimotor having the ability to achieve social referencing. Three situations have been tested: 1) a robotic arm is able to catch and avoid objects as emotional interaction from the human partner. 2) a mobile robot is able to reach or avoid certain areas of its environment. 3) an expressive head can orient its gaze in the same direction as humans and addition to associate emotional values to objects according tothe facial expressions of experimenter. We show that a developmental sequence can merge from emotional interaction and that social referencing can be explained a sensorimotor level without needing to use a model theory mind.

Contrairement aux robots conventionnels, les robots continuums ne possèdent ni de liaisons discrètes, ni de corps rigides. Leur courbure est continue, similaire à celle des trompes ou des tentacules animales. Le développement de ce type de robots pour les applications médicales soulève plusieurs problèmes : optimisation de la conception, modélisation cinématique, choix des capteurs et commande en temps réel. Les techniques actuelles pour la modélisation des robots continuums ne tiennent pas compte les incertitudes inhérentes au système. La prise en compte de ces incertitudes est d'une importance cruciale pour la certification de tels robots utilisés pour les gestes chirurgicaux. Dans cette thèse, nous considérons un micro robot continuum à 3 actionneurs. Ce robot a été développé au laboratoire LISSI pour le traitement des anévrismes de l'aorte abdominale par chirurgie mini-invasive. Dans ce type de chirurgie, il est important de disposer d'un modèle cinématique garanti du robot continuum prenant en compte différents types d'incertitudes. Pour traiter ce problème, nous utilisons les techniques d'analyse par intervalles. Ces techniques permettent de résoudre des problèmes d'optimisation globale sous contraintes tout en prenant en compte des incertitudes aussi bien aléatoires que systématiques. La contribution de cette thèse porte sur la proposition d'un modèle cinématique d'un robot continuum prenant en compte des incertitudes liées à différents facteurs comme les erreurs d'arrondis, les erreurs paramétriques et les erreurs dues aux hypothèses de modélisation. Tout d'abord, nous développons les modèles géométriques direct et inverse du robot continuum sous forme de solutions de formes fermées. Ces solutions sont utilisées pour caractériser les différentes propriétés du robot comme la manipulabilité. Pour calculer la cinématique inverse garantie et optimale, nous appliquons une version améliorée de l'algorithme par séparation et évaluation (Branch and Bound). En considérant l'orientation du robot, la cinématique inverse est ramenée à la formulation et à la résolution par intervalles d'un problème d'optimisation sous contraintes. Les approches proposées sont validées par des simulations. Les résultats de cette thèse constituent un cadre général pour la modélisation garantie de la classe des robots continuums dont la forme est décrite par des actionneurs en flexion continue / Unlike conventional robots, continuum robots do not contain any rigid link or any rotational joint but present a continuous bending in the structure through smooth motion. Development of this class of robot for their medical application presents a common set of problems : optimization of design, kinematic modeling, sensing choice, and their control in real time. Existing techniques for the modeling of continuum robots do not take system uncertainties into account. A proper handling of these uncertainties becomes of crucial importance for the certification of such robots used as medical devices. For our research, we consider a continuum robot that has been developed for the treatment of aortic aneurysm by Minimal Invasive Surgery (MIS), in LISSI Lab. In the context of MIS, it is very important to develop a guaranteed kinematic model of robot taking into account the different types of un-certainties. To handle this problem, we use the techniques of interval analysis. These techniques are capable of performing the global optimization and solving CSPs while taking into account the different uncertainties ; no matter, whether these uncertainties are random or systematic. Contribution of this thesis is proposal of a continuum robot's kinematic model that can take system uncertainties due to different factors such as rounding errors, parametric errors, and errors due to modeling assumptions. Initially, we develop the forward and inverse kinematics of the continuum robot in closed-form formulas. These derived formulas are used for the characterization of different properties of the robot such as manipulability. To find optimized guaranteed kinematics, we retained and applied an enhanced version of branch and bound algorithm. The inverse kinematics was formulated and resolved as a constrained optimization problem for robot's orientation. The proposed approaches are validated through simulations. The results of this thesis give rise to a general framework that is valid to handle the system uncertainties for the entire class of continuum robot that are shaped by continuously bending actuators

Range-based localization is a widely used technique for position estimation where distances are measured to anchors, nodes with known positions, and the position is analytically estimated. It offers the benefits of providing high localization accuracy and involving simple operation over multiple deployments. Examples are the Global Positioning System (GPS) and network-based cellular handset localization. Range-based localization is promising for a range of applications, such as robot deployment in emergency scenarios or monitoring industrial processes. However, the presence of clutter in some of these environments leads to a severe degradation of the localization accuracy due to non-line-of-sight (NLOS) signal propagation. Moreover, current literature in NLOS-mitigation techniques requires that the NLOS distances constitute only a minority of the total number of distances to anchors. The key ideas proposed in the dissertation are: 1) multi-hop localization offers significant advantages over single-hop localization in NLOS-prone environments; and 2) it is possible to further reduce position errors by carefully placing intermediate nodes among the clutter to minimize multi-hop distances between the anchors and the unlocalized node. We demonstrate that shortest path distance (SPD) based multi-hop localization algorithms, namely DV-Distance and MDS-MAP, perform the best among other competing techniques in NLOS-prone settings. However, with random node placement, these algorithms require large node densities to produce high localization accuracy. To tackle this, we show that the strategic placement of a relatively small number of nodes in the clutter can offer significant benefits. We propose two algorithms for node placement: first, the Optimal Placement for DV-Distance (OPDV) focuses on obtaining the optimal positions of the nodes for a known clutter topology; and second, the Adaptive Placement for DV-Distance (APDV) offers a distributed control technique that carefully moves nodes in the monitored area to achieve localization accuracies close to those achieved by OPDV. We evaluate both algorithms via extensive simulations, as well as demonstrate the APDV algorithm on a real robotic hardware platform. We finally demonstrate how the characteristics of the clutter topology influence single-hop and multi-hop distance errors, which in turn, impact the performance of the proposed algorithms.

This thesis proposes that a baggage handling system (BHS) environment can be defined and coupled to a whole life cycle cost (WLCC NPV) model. The results from specific experiments using the model can be used as the basis by which to commercially compare BHS flight build types of any capacity, and BHS geographical location. The model examined the three flight build types(i): Fully automatic build2; (ii) Semi-automatic build, and(iii); Manual build. The model has the ability to calculate a bag flow busy hour rate, and to replicate the baggage flow characteristics observed within real BHS operations. Whole life cycle costs (WLCC NPV) results are produced, and these form the basis by which the comparison of BHS types is made. An overall WLCC NPV scatter diagram was produced, which is a summation of each of the test sensitivities. The assumptions and limitations of the analysis are provided. It is proposed that the results, conclusions and recommendations shall be of value to airports, airlines, and design consultants.

The subject of the thesis is the design and implementation of a modular control system environment, which could be used in robotics. Both autonomous and guided robots are supported. The higher-level software com- ponents like localization, steering, decision making, etc. are effectively sepa- rated from the underlying hardware devices and their communication protocols in the environment. Based on the layered design, hardware-independent algo- rithms can be implemented. These can run on different hardware platforms just by exchanging specific device drivers. Written in C++ using standard libraries, the final software is highly portable and extensible. Support for new platforms and hardware modules can be implemented easily. The whole sys- tem was tested on two robots and the particular instances of the systems built using this development environment are included in the solution and partially described in the thesis.

<p>Robotic-assisted surgery (RAS) is one of the most significant advancements in surgical techniques in the past three decades. It provides benefits of reduced infection risks and shortened recovery time over open surgery as well as improved dexterity, stereoscopic vision, and ergonomic console over laparoscopic surgery. The prevalence of RAS systems has increased over years and is expected to grow even larger. However, the major concerns of RAS are the technical difficulty and the system complexity, which can result in long learning time and impose extra cognitive workload and stress on the operating room. Human Factor and Ergonomics (HFE) perspective is critical to patient safety and relevant researches have long provided methods to improve surgical outcomes. Yet, limited studies especially using objective measurements, have been done in the RAS environment. </p> <p> </p> <p>With advances in wearable sensing technology and data analytics, the applications of physiological measures in HFE have been ever increasing. Physiological measures are objective and real-time, free of some main limitations in subjective measures. Eye tracker as a minimally-intrusive and continuous measuring device can provide both physiological and behavioral metrics. These metrics have been found sensitive to changes in workload in various domains. Meanwhile, electroencephalography (EEG) signals capture electrical activity in the cerebral cortex and can reflect cognitive processes that are difficult to assess with other objective measures. Both techniques have the potential to help address some of the challenges in RAS.</p> <p> </p> <p>In this study, eight RAS trainees participated in a 3-month long experiment. In total, they completed 26 robotic skills simulation sessions. In each session, participants performed up to 12 simulated RAS exercises with varying levels of difficulty. For Research Question I, correlation and mixed effect analyses were conducted to explore the relationships between eye tracking metrics and workload. Machine learning classifiers were used to determine the sensitivity of differentiating low and high workload with eye tracking metrics. For Research Question II, two eye tracking metrics and one EEG metric were used to explain participants’ performance changes between consecutive sessions. Correlation and ANOVA analyses were conducted to examine whether variations in performance had significant relationships with variations in objective metrics. Classification models were built to examine the capability of objective metrics in predicting improvement during RAS training. </p> <p> </p> <p>In Research Question I, pupil diameter and gaze entropy distinguished between different task difficulty levels, and both metrics increased as the level of difficulty increased. Yet only gaze entropy was correlated with subjective workload measurement. The classification model achieved an average accuracy of 89.3% in predicting workload levels. In Research Question II, variations in gaze entropy and engagement index were negatively correlated with variations in task performance. Both metrics tended to decrease when performance increased. The classification model achieved an average accuracy of 68.5% in predicting improvements.</p> <p> </p> <p>Eye tracking metrics can measure both task workload and perceived workload during simulated RAS training. It can potentially be used for real-time monitoring of workload in RAS procedure to identify task contributors to high workload and provide insights for training. When combined with EEG, the objective metrics can explain the performance changes during RAS training, and help estimate room for improvements.</p>

[pt] Motores de passo são os motores mais utilizados em aplicações de controle de posicionamento em malha aberta. Entretanto, as limitações desta forma de atuação têm fomentado o desenvolvimento de novas técnicas que incorporem o controle em malha fechada. Motores de passo possuem boa relação entre torque e custo, tornando-os atraentes para aplicações em manipuladores robóticos. Mas as técnicas tradicionais de controle de manipuladores elétricos, que normalmente assumem o uso de motores de corrente contínua, apresentam baixo desempenho quando aplicadas a motores de passo, mesmo com o uso de sensores de posição. A forma mais comum de controle em malha fechada de motores de passo exige um encoder diretamente acoplado ao eixo do motor, formando um sistema colocado. No entanto, o projeto de muitos motores de passo não permite este acoplamento. Nesses casos, é necessário instalar os encoders na estrutura do manipulador, separados dos atuadores, caracterizando um sistema nãocolocado, que tipicamente apresenta problemas de estabilidade. Este trabalho propõe uma técnica de controle que recebe a realimentação de um encoder, não diretamente acoplado ao motor, e gera uma sequência de pulsos para o driver do motor de passo. Esse trem de pulsos é calculado de modo a não exigir acelerações excessivas, e assim prevenir a perda de passo do motor. O modelo de um sistema robótico usando este controlador é desenvolvido e simulado em Simulink/MATLAB. Um manipulador robótico de seis graus de liberdade acionado por motores de passo é especialmente projetado e construído para validar a técnica de controle apresentada, controlado por um microcontrolador PIC18F2431. O manipulador desenvolvido é modelado, e sua dinâmica analisada através de simulações. Os experimentos comprovam a eficiência da técnica de controle proposta, resultando em uma precisão absoluta na extremidade do manipulador de 1,3mm e repetibilidade 0,5mm . / [en] Stepper motors are used in most applications in open loop. However, the limitations of this type of control have encouraged the development of new techniques for closed loop control. Stepper motors have a good relationship between torque and cost, making it attractive for applications in robotic manipulators. But the limitation of traditional control deteriorates the performance of the manipulator. The most common form of closed loop control of stepper motors require an encoder directly coupled to the motor shaft. However, this is not always practical. In some cases, it is necessary to control the position of some system component that can’t be precisely known from the position of the motor. This work proposes a control technique that receives feedback from an encoder, not directly coupled to the motor shaft, and generates a sequence of pulses to the stepper motor driver. This pulse train is done so as not to require excessive accelerations, and thus prevent the loss of step. The model of a system using this controller is built using Simulink/MATLAB. A robotic manipulator of six degrees of freedom, using stepper motors, is designed and built to validate the presented control techniques, implemented on a PIC18F2431 microcontroller. The obtained absolute accuracy is 1,3mm and repeatability 0,5mm , proving the efficiency of the proposed control technique.

Avanços positivos nas pesquisas em veículos agrícolas autônomos (VAA\'s) e de robôs agrícolas móveis (RAM\'s) têm sido conquistados nos últimos anos. Entretanto, um número limitado de trabalhos tem proposto sistemas robustos baseados em arquiteturas robóticas capazes de realizar operações múltiplas e idependentes, bem como adaptar-se às mudanças ambientais no campo. Por outro lado, em outras áreas de pesquisa, um número representativo de arquiteturas baseadas em comportamentos tem sido proposto para guiagem e para navegação autônomas de robôs móveis em ambientes não estruturados e/ou não explorados. No presente trabalho, uma arquitetura robótica baseada em comportamentos é desenvolvida para guiagem e navegação de RAM\'s e VAA\'s. Regras difusas são utilizadas para compor e coordenar comportamentos primitivos e comportamentos complexos. O desenvolvimento inclui: a implementação e a simulação da arquitetura em um mini-robô; a avaliação e a caracterização de sensores para o módulo perceptivo da arquitetura; e a aplicação de um método de análise baseado em um modelo matemático para auxiliar a composição de uma rede de comunicação digital baseada no protocolo CAN para sistemas de controle robóticos. Experimentos foram realizados para avaliar os comportamentos implementados e para avaliar a capacidade de operação da plataforma robótica em um ambiente agrícola simulado. Os resultados mostraram a viabilidade da abordagem proposta. A modularidade da arquitetura com a utilização de controladores difusos descentralizados simplificou a implementação da arquitetura. O processo de arbitragem difuso mostrou-se um método simples e viável para implementar a coordenação de comportamentos e para compor comportamentos complexos. A avaliação e caracterização de sensores, em especial de um sensor ultrassônico, permitiram a determinação de condições operacionais para a utilização desses sensores em VAA\'s ou em RAM\'s. A aplicação do modelo matemático para a rede permitiu a análise de desempenho da rede CAN para diferentes equipamentos e sob diferentes parâmetros de configuração para aplicação em um RAM. / Positive advances on AVV (Agricultural Autonomous Vehicle) and MAR (Mobile Agricultural Robot) research are noticed in recent years. However, a limited number of works have proposed reliable systems based on a robotic architectures that are able to perform multiple and independent operations, as well as to self-adapt under changing environmental conditions in the field. In other hand, in other research areas a considerable number of behavior-based architectures have been proposed for mobile robot for autonomous guidance and navigation in unstructured and/or in unexplored environments. At this work, a robotic behavior-based architecture is developed for guidance and navigation of AAV and MAR. Fuzzy rules are used to compose and coordinate the primitive and the complex behaviors. The development includes: the implementation and the simulation of the proposed architecture on a mini-robot; the evaluation and characterization of sensors for the perceptive module of the architecture; and the application of an analysis method based on a mathematical model to assist the composition of a digital communication networks based on the CAN protocol for robot control systems. Experiments have been performed to evaluate the implemented behaviors and to evaluate the operation ability of the robotic platform on a simulated agricultural environment. The results show the feasibility of the proposed approach. The modularity of the architecture by using decentralized fuzzy controllers simplifies the implementation of the robotic architecture. The fuzzy arbitration process is an easy and a feasible method to implement the behavior coordination and to compose complex behaviors. The sensors evaluation and characterization, in particular of an ultrasonic sensor, have allowed establishing operational conditions for using them in AAV or in a MAR. The application of the network mathematical model has allowed the performance analysis of the CAN-based networks under differentiated equipment and configuration parameters for applications in a MAR.