Please read the abstract in the section 00front of this document / Dissertation (MEng)--University of Pretoria, 2009. / Mechanical and Aeronautical Engineering / unrestricted

Gripdon är vanliga i många branscher. De kan exempelvis lyfta och transportera föremål såsom lådor och bilar. Gripdon kan hittas i olika storlekar, tillräckligt stora för att transportera en bil eller tillräckligt små för att sortera även piller. Normalt är gripdon anpassade till en specifik uppgift. Gripdonets form är beroende av föremålet som det ska hantera. Normalt är föremålet enhetligt i form och vikt. Utmaningen här är att projekts gripdon ska kunna hantera föremål av olika storlekar och vikter. Gripdonet som utvecklades för detta projekt kommer att transportera föremål som väger någonstans från 3 kg till 28 kg. Det erforderliga omfånget av dimensioner är som följer: höjd 200–600 mm, djup 300–1 000 mm och längd 300–1 000 mm. Förutom de olika storlekarna krävdes även att gripdonet ska förflytta föremål med tillfredställande hastighet. Initialt skulle griparen vara fäst vid manipulatorn ABB IRB 4600. Denna modell kan transportera upp till 40 kg, därför borde det utvecklade gripdonet ha en viktgräns på 12 kg. Många olika lösningar studerades för att hantera utmaningen. Den valda lösningen baserades på att ha två linjära enheter drivna av servomotorer. De linjära enheterna är synkroniserade och rör sig i motsatta riktningar. Det finns linjära enheter som möjliggör synkroniserad motsatt rörelse men de tillgängliga modellerna skulle avsevärt sakta ned och skulle inte vara väsentligt olika i vikt eller pris jämfört med den konstruerade enheten. Griparens konstruktion är baserad på det maximala kontaktområdet med lådan för att öka friktionen mellan gripdon och kartongen. Griparens form är utformad för att undvika att deformera metallen och att gripdonet inte behövs repareras under lång tid. Konstruktionens kanter är konstruerade med plåtfästen för att försäkra att gripdonet inte böjer sig. Griparens uppskattade vikt är betydligt högre än de ursprungliga förväntningarna. Därför skulle IRB 4600, 40 kg manipulatorn behöva ersättas av en modell som kan bära den uppskattade vikten (cirka 250 kg=). / Gripers are common in many industries; they can lift and transport a variety of objects such as boxes and cars, for example. Gripers can be found in a full spectrum of sizes; large enough to transport a car or small enough to sort the smallest of pills. Grippers are typically customized for a specific task; the shape of the griper is dependent on the object it will carry. Normally, the object is uniform in its shape and weight. This project required the griper to handle multiple objects of various sizes and weights, presenting a particular challenge. The griper that was developed for this project will transport objects weighing anywhere from 3 to 28 kg. The required range of dimensions are as follows; height from 200 to 600 mm, depth of 300 to 1000 mm, and length from 300 to 1000 mm. In addition to the variety of sizes, the griper was also required to move objects with speed. Initially, the griper would be attached to the manipulator ABB IRB 4600. This model can transport up to 40 kg, therefore the developed griper should have a weight limit of 12 kg. Many different solutions were studied in order to solve the challenge of multiple size and weight variations. The chosen solution was based on having two linear units driven by servo motors. The linear units are synchronized and move in opposite directions. There are linear units that allow for synchronized, opposed movement but the models available would significantly slow the movement and would not be materially different in weight or price compared to the designed unit. The design of the griper is based on allowing the maximum contact area with the box to increase friction between the gripper and cardboard. The shape of the griper is designed to avoid deforming the metal and ensuring the griper will not need to have it's parts repaired for a long time. The edges of the structure are constructed with bent sheet metal brackets, to assure the griper will not bend. The estimated weight of the griper is significantly heavier than the original expectations. Consequently, the IRB 4600,40 kg manipulator would need to be replaced with a model that can carry the estimated weight of approximately 250 kg.

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The document describes a manipulator for a wheel excavator. The purpose of the manipulator is to handle with the propulsive shaft of a crushing machine and the tension cylinder of an interchanging conveyor-belt during the assembling and maintenance. The objective of the master's thesis is the strength analysis of the manipulator components and the telescopic arm with using the finite element method. The thesis also comprises the assembly drawing of the manipulator with additional devices and the propulsion system calculation. The project is carried out with the cooperation of NOEN a.s.

No description available.

Resumo: Este trabalho trata da geração e otimização de trajetórias de um manipulador robótico planar (2D) de três graus de liberdade, num ambiente livre de obstáculos. Visto que a cinemática inversa de braços robóticos é um problema complexo que, em geral, geram múltiplas soluções, otimizam-se, aqui, estas soluções através de algoritmos genéticos (AGs). A função de avaliação do AG tem caráter multi-objetivo, de forma a minimizar os deslocamentos angulares e obter de forma precisa a posição da garra, usando funções desenvolvidas para o ambiente Matlab, tais como, GAOT e PLANMANT, devido a sua facilidade de programação e geração de gráficos. A seguir, foram obtidos resultados através de programa desenvolvido em linguagem C, utilizando a biblioteca GAUL, e tem-se avaliado o desempenho computacional de processamento. E finalmente, para a validação experimental deste estudo, tem-se implementado este procedimento em um manipulador robótico Robix RCS-6 de configuração similar ao modelo simulado. Os resultados mostram que o método implementado é eficiente, computacionalmente rápido e viável em aplicações reais. / Abstract: This work treats of the generation and optimization of trajectories for a planar robotic manipulator (2D) of three degrees of freedom, in free environment obstacles. Since the inverse kinematics of robotic arms are a complex problem that, generally, generate multiple solutions, here are optimized these solutions through genetic algorithms (AGs). The evaluation function of the AG has multi-objective character which minimize the angular displacements and the positional errors, being used functions developed for the Matlab environment, such as, GAOT and PLANMANT, due its compliance of programming and graphics generation. Immediately, results were obtained through program developed in language C, using the GAUL library. The computational processing performance has been evaluated. And finally, for the experimental validation of this study, has been implemented this procedure in a robotic manipulator Robix RCS-6 of similar configuration to the simulated model. The results show that the implemented method is efficient, and computationally fast and viable in real applications. KEYWORDS: Robotic manipulator, Optimal trajectory, Inverse kinematics, Genetic algorithm. / Orientador: Victor Orlando Gamarra Rosado / Coorientador: Francisco José Grandinetti / Banca: Mauro Pedro Peres / Banca: Luiz Octavio Mattos dos Reis / Banca: José Rui Camargo / Banca: Carlos Alberto Chavez / Doutor

Este trabalho apresenta os resultados da aplicação de três técnicas de controle utilizadas no projeto e implementação do controle de um manipulador subatuado planar de três juntas em série e de elos rígidos, projetado e construído pela Universidade Carnegie Mellon, EUA. Devido ao alto grau de não-linearidade deste sistema, seria muito difícil implementar um controlador H2, H&#8734 ou H2/H&#8734 que atuasse sozinho. Assim, propõe-se a utilização de um método de controle combinado: torque computado/H2, H&#8734 ou H2/H&#8734. No controle combinado, a porção correspondente ao torque computado lineariza e pré-compensa a dinâmica do modelo da planta nominal, enquanto a porção correspondente ao controle H2, H&#8734 ou H2/H&#8734 realiza uma pós-compensação dos erros residuais, que não foram completamente eliminados pelo método torque computado. Testes de acompanhamento de trajetória e testes de robustez são realizados aqui para comprovar a eficiência destes controladores, com resultados de implementação bastante satisfatórios. / This work presents the application results of three control techniques used for the control design and implementation of a serial planar underactuated manipulator with three joints and rigid links, designed and built by the Carnegie Mellon University, USA. Due to the high non-linearity degree of this system, it would be very difficult to implement an H2, H&#8734 or H2/ H&#8734 control which would actuate on the system by itself. Therefore, it is proposed a combined control method: computed torque/ H2, H&#8734 or H2/H&#8734. In the combined control, the portion corresponding to the computed torque linearizes and pre-compensates the dynamics of the nominal model, while the portion corresponding to the H2, H&#8734 or H2/H&#8734 control realizes a pos-compensation of the residual errors, not completely removed by the computed torque method. Trajetory tracking and robustness tests are performed here to demonstrate the efficiency of these controllers, with very satisfatory implementation results.

Este trabalho apresenta uma metodologia de controle de posição das juntas passivas de um manipulador subatuado de uma maneira subótima. O termo subatuado se refere ao fato de que nem todas as juntas ou graus de liberdade do sistema serem equipados com atuadores, o que ocorre na prática devido a falhas ou como resultado de projeto. As juntas passivas de manipuladores desse tipo são indiretamente controladas pelo movimento das juntas ativas usando as características de acoplamento da dinâmica de manipuladores. A utilização de redundância de atuação das juntas ativas permite a minimização de alguns critérios, como consumo de energia, por exemplo. Apesar da estrutura cinemática de manipuladores subatuados ser idêntica a do totalmente atuado, em geral suas características dinâmicas diferem devido a presença de juntas passivas. Assim, apresentamos a modelagem dinâmica de um manipulador subatuado e o conceito de índice de acoplamento. Este índice é utilizado na seqüência de controle ótimo do manipulador. A hipótese de que o número de juntas ativas seja maior que o número de passivas permite o controle ótimo das juntas passivas, uma vez que na etapa de controle destas há mais entradas (torques nos atuadores das juntas ativas), que elementos a controlar (posição das juntas passivas). Neste ponto reside a contribuição desta tese ao estado da arte, uma vez que não há até o momento publicação que proponha o controle ótimo das juntas passivas neste caso. / This work presents a control methodologie for the position of the passive joints of an underactuated manipulator in a suboptimal way. The term underactuated refers to the fact that not all the joints or degrees of freedom of the system are equipped with actuators, which occurs in practice due to failures or as design result. The passive joints of manipulators like this are indirectly controlled by the motion of the active joints using the dynamic coupling characteristics. The utilization of actuation redundancy of the active joints allows the minimization of some criteria, like energy consumption, for example. Although the kinematic structure of an underactuated manipulator is identical to that of a similar fully actuated one, in general their dynamic characteristics are different due to the presence of passive joints. Thus, we present the dynamic modelling of an underactuated manipulator and the concept of coulpling index. This index is used in the sequence of the optimal conirol of the manipulator. The hipotheses that the number of active joints is greatter than the number of passives (na>np) allows the optimal control of the passive joints, since there are more inputs (torques at the actuators of the active joints), than elements to be controlled (position of the passive joints). At this point resides the contribution of this dissertation to the state of the art, once there is no publication that proposes the optimal control of the passive joints in this case.

The goal of this thesis is the kinematic analysis and evaluation of wheelchair mounted robotic arms. More specifically, to address the kinematics of the wheelchair mounted robotic arm (WMRA) with respect to its ability to reach positions commonly required by an assistive device in activities of daily living (ADL). A robotic manipulator attached to a power wheelchair could enhance the manipulation functions of an individual with a disability. In this thesis, a procedure is developed for the kinematic analysis and evaluation of a wheelchair mounted robotic arm. In addition to developing the analytical procedure, the manipulator is evaluated, and design recommendations and insights are obtained. At this time there exist both commercially-available and industrial wheelchair mountable robotic manipulators. The commercially-available manipulators (of which two will be addressed in this research) have been designed specifically for use in rehabilitation robotics. In contrast, industrial robotic manipulators are designed for speed, precision, and endurance. These traits are not required in assistive robots and can actually be dangerous to the operator if mounted onto a wheelchair. Manipulators to be used as WMRAs must be designed specifically for assistive functions in order to be utilized as a wheelchair mounted robotic arm. In an effort to evaluate two commercial manipulators, the procedure for kinematic analysis is applied to each manipulator. Design recommendations with regard to each device are obtained. This method will benefit the researchers by providing a standardized procedure for kinematic analysis of WMRAs that is capable of evaluating independent designs.

This thesis presents a new approach for selecting a manipulator arm configuration (a pose) in an environment where the positions of the work items are not able to be fully controlled. The approach utilizes a belief formed from a priori knowledge, observations and predictive models to select manipulator poses and motions. Standard methods for manipulator control provide a fully specified Cartesian pose as the input to a robot controller which is assumed to act as an ideal Cartesian motion device. While this approach simplifies the controller and makes it more portable, it is not well suited for less-controlled environments where the work item position or orientation may not be completely observable and where a measure of the accuracy of the available observations is required. The proposed approach suggests selecting a manipulator configuration using two types of rating function. When uncertainty is high, configurations are rated by combining a belief, represented by a probability density function, and a value function in a decision theoretic manner enabling selection of the sensor??s motion based on its probabilistic contribution to information gain. When uncertainty is low the mean or mode of the environment state probability density function is utilized in task specific linear or angular distances constraints to map a configuration to a cost. The contribution of this thesis is in providing two formulations that allow joint configurations to be found using non-linear optimization algorithms. The first formulation shows how task specific linear and angular distance constraints are combined in a cost function to enable a satisfying pose to be selected. The second formulation is based on the probabilistic belief of the predicted environment state. This belief is formed by utilizing a Bayesian estimation framework to combine the a priori knowledge with the output of sensor data processing, a likelihood function over the state space, thereby handling the uncertainty associated with sensing in a less controlled environment. Forward models are used to transform the belief to a predicted state which is utilized in motion selection to provide the benefits of a feedforward control strategy. Extensive numerical analysis of the proposed approach shows that using the fed-forward belief improves tracking performance by up to 19%. It is also shown that motion selection based on the dynamically maintained belief reduces time to target detection by up to 50% compared to two other control approaches. These and other results show how the proposed approach is effectively able to utilize an uncertain environment state belief to select manipulator arm configurations.