A mobile manipulator is a robotic system consisting of a robotic manipulator mounted onto a mobile base. This greatly extends the workspace of the robotic manipulator and allows it to perform more tasks. However, combining both systems increases the complexity of the control task as well as introducing additional controller tasks such as coordination of motion, where executing the task can involve using both the mobile base and manipulator, and cooperation of task, where many tasks can be executed at once. In this thesis a controller for a mobile manipulator is developed from smaller, simple controller blocks, allowing the controller to be flexible, easy to understand, and straightforward to implement using well-known embedded software implementation approaches. A behaviour-based approach was used to build the individual controllers, and a hierarchical structure was used to organise the individual controllers to provide cooperation between them and coordinated motion. The task assigned to the controller was to reach a series of waypoints in a large workspace, while satisfying performance metrics of manipulability and tip-over sta- bility. The operation of the controller was tested in simulation using 100 randomly generated scenarios consisting of five randomly generated waypoints in each. Using default thresholds for manipulability and tip-over stability, the controller was success- fully able to complete all scenarios. Further simulations were then performed testing the effects of varying the thresholds of the performance metrics to explore the tradeoffs involved in different parameter choices. The controller was successful in a majority of these scenarios, with only a few failing due to extreme threshold choices. The reasons for these failures, and the corresponding lessons for robot designers are discussed. Finally, to demonstrate the modularity of the controller, an obstacle avoidance con- troller was added and simulation results showed the controller was capable of avoiding obstacles while still performing the same tasks that were used in previous tests. Successful simulation results of the controller across a range of performance metrics shows that the combination of a behaviour based and hierarchical approach to mobile manipulator control is not only capable of producing a functional controller, but also one that is more modular and easier to understand than the monolithic controllers developed by other researchers.

In our environment we do two things with objects: identify them, and act on them. Perhaps not coincidentally, research has shown that the brain appears to have two distinct visual streams, one that is engaged during the identification of objects, and one that is associated with action. Although these visual streams are distinct, there has been increasing interest in how the action and identification systems interact during grasping and identification tasks. In particular, the current research explored the role that previous motor experience with familiar manipulable objects might have on the time it takes healthy participants to identify these objects (relative to non-manipulable objects). Furthermore, previous research has shown that there are multiple, computationally and neuro-anatomically different, action systems. The current research was particularly interested in the action systems involved in 1) grasping, and 2) functionally using an object. Work began by developed a new stimulus set of black & white photographs of manipulable and non-manipulable objects, and collecting ‘graspability’ and ‘functional usage’ ratings (chapter 2). This stimulus set was then used to show that high manipulability was related to faster naming but slower categorization (chapter 3). In chapter 4, the nature of these effects was explored by extending a computational model by Yoon, Heinke and Humphreys (2002). Results from chapter 5 indicated independent roles of graspability and functional usage during tasks that required identification of objects presented either with or without a concurrent mask. Specifically, graspaility effects were larger for items that were not masked; and functional use effects were larger for items that were masked. Finally, chapter 6 indicated that action effects during identification tasks are partly based on how realistic the depictions of the objects are. That is, results from chapter 6 indicated the manipulability effects are larger for photographs than they are for line-drawings of the same objects. These results have direct implications for the design of future identification tasks, but, more broadly, they speak to the interactive nature of the human mind: Action representations can be invoked and measured during simple identification tasks, even where acting on the object is not required. / Manuscript-based dissertation. One introductory chapter, one concluding chapter, and five manuscripts (seven chapters in total).

This research uses Transmissivity Index (TI) and other transmission indices to analyze the transmission performance by applying those indices to coupler-driven mechanisms with sliders. Other estimative transmission indices include Total Transmission Index (TTI) and Transmissible Mechanical Advantage (TMA). The point with best transmission performance is ¡§Effective Point,¡¨ and the combination of the effective points becomes ¡§Locus of Effective Points¡¨. In addition, this research puts the influence of mechanisms with sliders including slider-friction into consideration, and also analyzes two inverses of mechanisms with sliders. Then we can extend to study the transmission performance of six-bar mechanisms. Finally, we apply the research result into some examples, such as ping pong table mechanism, four-bar and six-bar windows operator mechanisms, rowing exercise mechanism, so that we can find the better transmission performance of those mechanisms.

This article is based on several nouns about transmission performance such as limiting positions, manipulation angle, transmission angle and mechanical advantage. In order to analyse the transmission performance of the coupler-driven and crank-output linkage mechanism, this article has developed an index called Transmissivity of Mechanical Advantage (TMA) for designers, besides this useful index, this article has identified a new noun as Total Transmission Coupler Point, that means after acting a force on the same direction of coupler point moving instantly, then the output force on the crank will act on it¡¦s moving direction and make the Transmissivity Index be the best as 1. For the designers of the coupler-driven linkage mechanisms, the transmission performance and the position where the force acts on involves to coupler curves very much. Based on the result of this research, the designers are able to choose the most proper coupler curves, and the best position of the coupler point would be designed. The designers are able to pick the best one among several similar coupler curves, and also they can certainly get a best range of either the length or the angle of the coupler designed when they were designing the coupler-driven type 4-bar linkage or the Stephenson¡¦s III 6-bar linkage. The applying force must change the direction all the time when a coupler-driven mechanism is driven, and it makes this type of mechanism seems to be uncommon, but it doesn¡¦t mean this kind of mechanism is not worth of application. On the other hand, the short of research about this type of mechanism makes the designers feel helpless when they were trying to analyse the transmission performance of mechanisms were designed. This article develops not only the theorem of analysis but also builds computer programs to help the designers to analyse the transmission performance quickly and correctly

A mobile manipulator is a robotic arm mounted on a robotic mobile platform. In such a system, the degrees of freedom of the mobile platform are combined with that of the manipulator. As a result, the workspace of the manipulator is substantially extended. A mobile manipulator has two trajectories: the end-effector trajectory and the mobile platform trajectory. Typically, the mobile platform trajectory is not defined and is determined through inverse kinematics. But in some applications it is important to follow a specified mobile platform trajectory. The main focus of this work is to determine the inverse kinematics of a mobile manipulator to follow the specified end-effector and mobile platform trajectories, especially when both trajectories cannot be exactly followed simultaneously due to physical limitations. Two new control algorithms are developed to solve this problem. In the first control algorithm, three joint-dependent control variables (spherical coordinates D, α and β) are introduced to define the mobile platform trajectory in relation to the end-effector trajectory and vice versa. This allows direct control of the mobile platform motion relative to the end-effector. Singularity-robust and task-priority inverse kinematics with gradient projection method is used to find best possible least-square solutions for the dual-trajectory tracking while maximizing the whole system manipulability. MATLAB Simulated Planar Mobile Manipulation is used to test and optimize the proposed control system. The results demonstrate the effectiveness of the control system in following the two trajectories as much as possible while optimizing the whole system manipulability measure. The second new inverse kinematics algorithm is introduced when the mobile platform motion is restricted to stay on a specified virtual or physical track. The control scheme allows xii the mobile manipulator to follow the desired end-effector trajectory while keeping the mobile platform on a specified track. The mobile platform is moved along a track to position the arm at a pose that facilitates the end-effector task. The translation of the redundant mobile manipulator over the mobile platform track is determined by combining the mobility of the platform and the manipulation of the redundant arm in a single control system. The mobile platform is allowed to move forward and backward with different velocities along its track to enable the end-effector in following its trajectory. MATLAB simulated 5 DoF redundant planar mobile manipulator is used to implement and test the proposed control algorithm. The results demonstrate the effectiveness of the control system in adjusting the mobile platform translations along its track to allow the arm to follow its own trajectory with high manipulability. Both control algorithms are implemented on MATLAB simulated wheelchair mounted robotic arm system (WMRA-II). These control algorithms are also implemented on real the WMRA-II hardware. In order to facilitate mobile manipulation, a control motion scheme is proposed to detect and correct the mobile platform pose estimation error using computer vision algorithm. The Iterative Closest Point (ICP) algorithm is used to register two consecutive Microsoft Kinect camera views. Two local transformation matrices i. e., Encoder and ICP transformation matrices, are fused using Extended Kalman Filter (EKF) to filter the encoder pose estimation error. VICON motion analysis system is used to capture the ground truth of the mobile platform. Real time implementation results show significant improvement in platform pose estimation. A real time application involving obstacle avoidance is used to test the proposed updated motion control system.

Nous étudions la manipulation par coalition des modes de scrutin: est-ce qu'un sous-ensemble des électeurs, en votant de façon stratégique, peut faire élire un candidat qu'ils préfèrent tous au candidat qui aurait été vainqueur si tous les électeurs avaient voté sincèrement? D'un point de vue théorique, nous développons un formalisme qui permet d'étudier tous les modes de scrutin, que les bulletins soient des ordres de préférences sur les candidats (systèmes ordinaux), des notes ou des valeurs d'approbation (systèmes cardinaux) ou des objets encore plus généraux. Nous montrons que pour la quasi-totalité des modes de scrutin classiques, on peut réduire strictement leur manipulabilité en ajoutant un test préliminaire visant à élire le vainqueur de Condorcet s'il en existe un. Pour les autres modes de scrutin, nous définissons la condorcification généralisée qui permet d'obtenir des résultats similaires. Puis nous définissons la notion de culture décomposable, une hypothèse dont l'indépendance probabiliste des électeurs est un cas particulier. Sous cette hypothèse, nous prouvons que, pour tout mode de scrutin, il existe un mode de scrutin qui est ordinal, qui partage certaines propriétés avec le mode de scrutin original et qui est au plus aussi manipulable. Ainsi, la recherche d'un mode de scrutin de manipulabilité minimale (dans une classe de systèmes raisonnables) peut être restreinte à ceux qui sont ordinaux et vérifient le critère de Condorcet. Afin de permettre à tous d'examiner ces phénomènes en pratique, nous présentons SVVAMP, un package Python de notre cru dédié à l'étude des modes de scrutin et de leur manipulabilité. Puis nous l'utilisons pour comparer la manipulabilité par coalition de divers modes de scrutin dans plusieurs types de cultures, c'est-à-dire des modèles probabilistes permettant de générer des populations d'électeurs munis de préférences aléatoires. Nous complétons ensuite l'analyse avec des élections issues d'expériences réelles. Enfin, nous déterminons les modes de scrutin de manipulabilité minimale pour de très faibles valeurs du nombre d'électeurs et du nombre de candidats et nous les comparons avec les modes de scrutin classiques. De manière générale, nous établissons que la méthode de Borda, le vote par notation et le vote par assentiment sont particulièrement manipulables. À l'inverse, nous montrons l'excellente résistance à la manipulation du système appelé VTI, également connu par son acronyme anglophone STV ou IRV, et de sa variante Condorcet-VTI. / We investigate the coalitional manipulation of voting systems: is there a subset of voters who, by producing an insincere ballot, can secure an outcome that they strictly prefer to the candidate who wins if all voters provide a sincere ballot? From a theoretical point of view, we develop a framework that allows us to study all kinds of voting systems: ballots can be linear orders of preferences over the candidates (ordinal systems), grades or approval values (cardinal systems) or even more general objects. We prove that for almost all voting systems from literature and real life, manipulability can be strictly diminished by adding a preliminary test that elects the Condorcet winner if one exists. Then we define the notion of decomposable culture and prove that it is met, in particular, when voters are independent. Under this assumption, we prove that for any voting system, there exists a voting system that is ordinal, has some common properties with the original voting system and is at most as manipulable. As a consequence of these theoretical results, when searching for a voting system whose manipulability is minimal (in a class of reasonable systems), investigation can be restricted to those that are ordinal and meet the Condorcet criterion.In order to provide a tool to investigate these questions in practice, we present SVVAMP, a Python package we designed to study voting systems and their manipulability. We use it to compare the coalitional manipulability of several voting systems in a variety of cultures, i.e. probabilistic models generating populations of voters with random preferences. Then we perform the same kind of analysis on real elections. Lastly, we determine voting systems with minimal manipulability for very small values of the number of voters and the number of candidates and we compare them with classical voting systems from literature and real life. Generally speaking, we show that the Borda count, Range voting and Approval voting are especially vulnerable to manipulation. In contrast, we find an excellent resilience to manipulation for the voting system called IRV (also known as STV) and its variant Condorcet-IRV.

A haptic interface is a robotic force feedback device that provides a sense of touch to users of virtual reality simulations. This thesis presents a general method for the design optimization of parallel planar haptic devices based on maximizing the manipulability of the interface over its workspace. Manipulability is selected as the key design objective to ensure avoidance of singular configurations within the workspace and to maximize the interface's ability to generate feedback forces and torques in each direction in each handle location and orientation. The optimization approach developed in this thesis results in a set of candidate designs that are found by stepping the design parameters through the range of possible values, and testing the manipulability and other measures (including workspace area and space) at each location and orientation of the interface handle. To find the optimal design, a multi-objective approach is taken to generate a set of Pareto optimal designs. A smart Pareto filter is employed to yield a smaller set of designs representative of the full Pareto frontier. The most desirable design is chosen from this reduced set. The result is a general optimization method applicable to parallel haptic interfaces. The method is demonstrated on the design of a 3-RPR parallel planar interface.

No description available.

In order to improve the design of mechanical or mechatronic systems, mathematical optimization techniques have become an efficient and attractive tool with the increasing development of computer resources. However, the application of such optimization methods to multibody systems (MBS) remains a challenge when the MBS analysis requires the solving of assembly constraints. Hence, this PhD research focuses on the optimization of such closed-loop MBS, particularly when the objective function is of geometrical or kinematic nature. For kinematic optimization of MBS, we propose two penalty strategies to deal with assembly constraints during optimization. Both strategies are compared and illustrated via applications such as the isotropy maximization of parallel manipulators: the 3-dof Delta robot and the 6-dof Hunt platform. Following the same strategies, geometrical optimization of MBS is then investigated. However, due to a higher complexity, we propose to relax the problem, combining two modeling approaches: rigid-body and extensible-link formulations. This leads to a two-step strategy which is then successfully applied to synthesize mechanisms for path-following or function-generation problems. Through these applications, the existence of multiple local optima is highlighted. Therefore, instead of focusing on the unique global optimum solution, we have developed original methods to search and propose several local solutions for the design problem. This approach is called morphological optimization. This enables the designer to choose finally the best solution among several local optima using additional design criteria. Such morphological optimization techniques open the doors for the topology optimization of MBS which remains a challenging problem for future research / Afin d'améliorer la conception de systèmes mécaniques ou mécatroniques, les techniques d'optimisation mathématique sont devenues un outil efficace et attrayant étant donné le développement croissant des ressources informatiques. Cependant, l'application de telles méthodes d'optimisation sur les systèmes multicorps demeure un défi quand l'analyse du système nécessite la résolution de contraintes d'assemblage. C'est pourquoi cette recherche doctorale se concentre sur l'optimisation de tels systèmes multicorps, particulièrement lorsque la fonction objectif est de nature géométrique ou cinématique. Pour l'optimisation cinématique des systèmes multicorps, nous proposons deux stratégies de pénalité pour traiter les contraintes d'assemblage en cours d'optimisation. Ces deux stratégies sont comparées et illustrées par des applications telles que la maximisation d'isotropie de manipulateurs parallèles. Suivant les mêmes stratégies, l'optimisation géométrique des systèmes multicorps est alors étudiée. Cependant, vu la plus grande complexité, nous proposons de relaxer le problème en combinant deux approches de modélisation : une formulation en termes de corps rigides et une autre en termes de liens extensibles. Ceci nous mène à une stratégie en deux étapes qui est alors appliquée avec succès pour la synthèse de mécanismes. A travers ces applications, on a mis en évidence l'existence d'optimums locaux multiples. Dès lors, plutôt que de se focaliser sur l'unique optimum global, nous avons développé des méthodes originales afin de rechercher et proposer plusieurs solutions locales pour le problème de conception. Cette approche est baptisée "optimisation morphologique". Elle permet au concepteur de choisir finalement la meilleure solution parmi plusieurs optimums locaux en utilisant des critères supplémentaires de conception. De telles techniques d'optimisation morphologique ouvrent les portes pour l'optimisation topologique des systèmes multicorps qui demeure un challenge motivant pour des recherches futures.

Apresentamos a teoria sobre mercados de dois lados, centralizados e descentralizados, para analisar o mercado de admissão de estudantes aos Centros de Pós-graduação em Economia no Brasil ao longo dos últimos 15 anos. Iniciamos descrevendo a história da organização deste mercado até a época atual. As falhas do sistema descentralizado e as hipóteses sobre o insucesso do procedimento centralizado de 1997 são discutidas. Observações empíricas são utilizadas para propor um modelo teórico que represente aproximadamente o atual mecanismo descentralizado e explique a aparente duradoura aplicação desse mecanismo. Por fim, tecemos considerações a respeito das possibilidades de aprimoramento deste mercado com modificações do mecanismo existente. / We present the theory of two-sided matching markets, with centralized and decentralized mechanisms, in order to analyze a Brazilian market in which graduated students seek positions in postgraduate programs in economics. We first describe the institutional history of this market. The failures of the decentralized procedure and the hypothesis about the failure of the 1997 centralized mechanism are discussed. Empirical observations are used to propose a theoretical model that represents the actual decentralized matching procedure of the market. Based in this model we explain the apparent long-lasting use of this decentralized mechanism. Finally, we make considerations about the possibilities of developments in this market by modifying the mechanism used today.