The Multiobjective Optimization of a Prismatic Drive

The multiobjective optimization of Slide-o-Cam is reported in this paper. Slide-o-Cam is a cam mechanism with multiple rollers mounted on a common translating follower. This transmission provides pure-rolling motion, thereby reducing the friction of rack-and-pinions and linear drives. A Pareto frontier is obtained by means of multiobjective optimization. This optimization is based on three objective functions: (i) the pressure angle, which is a suitable performance index for the transmission because it determines the amount of force transmitted to the load vs. that transmitted to the machine frame; (ii) the Hertz pressure used to evaluate the stresses produced on the contact surface between cam and roller; and (iii) the size of the mechanism, characterized by the number of cams and their width

A Formulation of Complexity-Based Rules for the Preliminary Design Stage of Robotic Architectures

International audienceIn this paper we propose a formulation capable of measuring the complexity of robotic architectures at the conceptual-design stage. The motivation lies in providing a tool to the robot designer when selecting the best alternative among various candidates generated at the early stages of the design process, when a parametric design is not yet available. While the performance evaluation of a robot includes many criteria, we focus on: the kinetostatic, the elastostatic and the elastodynamic performances; workspace volume; actuation complexity and the life-cycle cost. Within the realm of conceptual design, characterized by the absence of a mathematical model, it is not possible to optimize the performance at hand using classical mathematical programming methods. In this paper, a set of rules derived from robotics knowledge is outlined. These rules are then used to formulate a complexity measure used to filter-out less promising architectures at the conceptual stage. The complete formulation is applied to the development of a six-degree-of-freedom robot with low topological complexity, high performance and low actuation-system complexity. A complexity-comparison between the proposed architecture, the DIESTRO and the PUMA robots, is also provided

La desmemoria impuesta a los hombres que trajeron. Cartagena de Indias en el siglo XVI y XVII. Un depósito de esclavos

This paper will focus on the role slaves played in the city of Cartagena de Indias in the seventeenth century. It will also focus on how the city became a slave warehouse and the role they played in shaping this colonial society. Their jobs, dances, sociability and ethnic origin are presented as main characters in the shaping of this city.    El presente trabajo se centrará en el papel que los esclavizadosjugaron en la ciudad de Cartagena de Indias en el siglo XVII. Igualmente,cómo la ciudad se convirtió en un depósito de esclavos y el papel queestos fueron desempeñando en la conformación de esta sociedad colonial.Sus trabajos, sus bailes, sus formas de sociabilidad, sus etnias de origenson presentados como protagonistas principales de la conformación deesta ciudad.  

Kinetostatic design of an innovative Schoenflies-motion generator

International audienceIn this paper, a novel parallel robot is introduced. The robot, a Schoenflies-Motion Generator (SMG), is capable of a special class of motions, namely, those produced with serial robots termed SCARA, an acronym for Selective-Compliance Assembly Robot Arm. These motions involve three independent translations and one rotation about an axis of fixed direction. Such motions are known to form a subgroup of the displacement group of rigid-body motions, termed the Schoenflies subgroup. The SMG is composed of two identical four-degree-of-freedom serial chains in a parallel array, sharing one common base and one common moving platform. The proximal module of each chain is active and has two controlled axes, the motors being installed on the fixed base. The links can thus be made light, thereby allowing for higher operational speeds. The distal module, in turn, is passive and follows the motions of its active counterpart, the whole mechanism giving, as a result, a four-degree-of-freedom motion to its end-platform

Design study of OER-CC ontology: a semantic web approach to describe open educational resources

Through the application of semantic technologies to describe Open Educational Resources, any agent (human or software-based) could process and understand its contents; therefore, the agent could perform tasks autonomously or in a more effective way. In this paper, we describe the design and validation of the OER-CC ontology, which models the domain knowledge of educational resources licensed under Creative Commons Licenses. One of the most important contributions of this work is that we implement different rules and axioms to identify inconsistencies between rights provided by a licensed on an learning material and particular uses that are performed on it

Reproducibility of lateral excursive tooth contact in a semi-adjustable articulator depending on the type of lateral guidance

The purposes of this study were (i) to compare the reproducibility of lateral tooth contacts of casts mounted in a semi-adjustable articulator when condylar guidance was set by different methods and (ii) to assess the margin of error of the variations of condylar guidance without changing lateral tooth contacts, depending on the type of lateral guidance. In subjects with different types of lateral guidance, intraoral lateral tooth contacts identified with occlusal registration strips were compared with those identified by use of a semi-adjustable articulator, setting the condylar guidance in four different ways: using protrusive wax wafers, by axiography and by adding and subtracting 5 degrees from the value of condylar guidance obtained by protrusive wax wafers. Tolerance to variations of condylar guidance without changing lateral tooth contacts was determined by increasing and decreasing the value of condylar guidance until lateral tooth contacts changed. Different ways of setting condylar guidance on a semi-adjustable articulator give rise to different values of condylar guidance in the same subject. The occlusal repercussions of these variations of condylar guidance values depend on the type of lateral guidance. Canine protection had the greatest tolerance to variations in the setting of condylar guidance without changing lateral occlusal contacts

Towards a learning analytics approach for supporting discovery and reuse of OER: an approach based on Social Networks Analysis and Linked Open Data

The OER movement poses challenges inherent to discovering and reuse digital educational materials from highly heterogeneous and distributed digital repositories. Search engines on today?s Web of documents are based on keyword queries. Search engines don?t provide a sufficiently comprehensive solution to answer a query that permits personalization of open educational materials. To find OER on the Web today, users must first be well informed of which OER repositories potentially contain the data they want and what data model describes these datasets, before using this information to create structured queries. Learning analytics requires not only to retrieve the useful information and knowledge about educational resources, learning processes and relations among learning agents, but also to transform the data gathered in actionable e interoperable information. Linked Data is considered as one of the most effective alternatives for creating global shared information spaces, it has become an interesting approach for discovering and enriching open educational resources data, as well as achieving semantic interoperability and re-use between multiple OER repositories. In this work, an approach based on Semantic Web technologies, the Linked Data guidelines, and Social Network Analysis methods are proposed as a fundamental way to describing, analyzing and visualizing knowledge sharing on OER initiatives

OER Development and Promotion. Outcomes of an International Research Project on the OpenCourseWare Model

In this paper, we describe the successful results of an international research project focused on the use of Web technology in the educational context. The article explains how this international project, funded by public organizations and developed over the last two academic years, focuses on the area of open educational resources (OER) and particularly the educational content of the OpenCourseWare (OCW) model. This initiative has been developed by a research group composed of researchers from three countries. The project was enabled by the Universidad Politécnica de Madrid OCW Office�s leadership of the Consortium of Latin American Universities and the distance education know-how of the Universidad Técnica Particular de Loja (UTPL, Ecuador). We give a full account of the project, methodology, main outcomes and validation. The project results have further consolidated the group, and increased the maturity of group members and networking with other groups in the area. The group is now participating in other research projects that continue the lines developed her