Examinando por Materia "TOLERANCIA (INGENIERÍA)"
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Ítem Design of computer experiments applied to modeling of compliant mechanisms for real-time control(Springer London, 2013-07) Acosta, Diego A.; Restrepo, David; Durango, Sebastián; Ruíz, Óscar E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis article discusses the use of design of computer experiments (DOCE) (i.e., experiments run with a computer model to find how a set of inputs affects a set of outputs) to obtain a force–displacement meta-model (i.e., a mathematical equation that summarizes and aids in analyz-ing the input–output data of a DOCE) of compliant mechanisms (CMs) -- The procedure discussed produces a force–displacement meta-model, or closed analytic vector function, that aims to control CMs in real-time -- In our work, the factorial and space-filling DOCE meta-model of CMs is supported by finite element analysis (FEA) -- The protocol discussed is used to model the HexFlex mechanism functioning under quasi-static conditions -- The HexFlex is a parallel CM for nano-manipulation that allows six degrees of freedom (x, y, z, hx, hy, hz) of its moving platform -- In the multi-linear model fit of the HexFlex, the products or inter-actions proved to be negligible, yielding a linear model (i.e.,linear in the inputs) for the operating range -- The accuracy of the meta-model was calculated by conducting a set of computer experiments with random uniform distribution of the input forces -- Three error criteria were recorded comparing the meta-model prediction with respect to the results of the FEA experiments by determining: (1) maximum of the absolute value of the error, (2) relative error, and (3) root mean square error -- The maximum errors of our model are lower than high-precision manufacturing tolerances and are also lower than those reported by other researchers who have tried to fit meta-models to the HexFlex mechanismÍtem Graphs of optimally fit features in assessment of geometric tolerances(2014) Ruíz, Óscar E.; Congote, John; Acosta, Diego A.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis article presents an industrial application case of geometric constraint graphs, whose nodes are statistically optimal instances of manufacturing or design features and whose edges are usual geometric relations used in tolerance applications -- The features might be virtual ones -- As a consequence, they may lie beyond the piece’s extents -- The geometric constraint graph may have cyclic topology -- Contrary to deterministic geometric constraint graphs, tolerance constraint graphs admit numerical slacks, due to their stochastic nature -- The methodology has been applied in industrial scenarios, showing superiority to traditional material features for the assessment of tolerancesÍtem Methodological approach for interactive preliminary-design(Universidad EAFIT, 2019) Ríos Zapata, David; Mejía Gutiérrez, Ricardo; Pailhès, JérômePreliminary design decision-making processes are related to the prioritisation of design specifications and variables in order to develop solutions that are closer to product’s requirements. Nevertheless, the size of the information is often large and hard to understand: keeping in track the list of dependent variables, independent variables and design objectives is a challenging task, with potentially reprocessing and loss of time, especially when it is necessary to identify how a modification on a variable might impact the performance of the product. The objective of this thesis is to generate an interactive method that can obtain a trade-off among the design objectives desirability. This trade-off process is supported on two aspects: i) the development of a traceability model, managing information from the input requirements (in the linguistic field) up to the variables definition (in the real numbers field). ii) A design amelioration framework, based on the definition of the design objectives desirability functions; the propagation of these functions until design variables allow calculating the combinations of values that maximise the global desirability of the solution. The goal of this trade-off process is to perform on a multidisciplinary design environment, facing convex and non-convex problems as well. The proposal of the thesis can be understood as a hybrid approach, including an interactive exploratory part and an inductive interactive part. On the exploratory part, designers can modify the variables using visual tools in order to understand in real time how these modifications have an impact on the design objectives. On the inductive part, designers make use a proposed pre-sizing method that calculates the values of the variables that maximise the desirability of the design objectives.Ítem Statistical Assessment of Global and Local Cylinder Wear(IEEE, 2007-06) Ruíz, Óscar; Vanegas, Carlos; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEAssessment of cylindricity has been traditionally performed on the basis of cylindrical crowns containing a set of points that are supposed to belong to a controlled cylinder – As such, all sampled points must lie within a crown. In contrast, the present paper analyzes the cylindricity for wear applications, in which a statistical trend is assessed, rather than to assure that all points fall within a given tolerance -- Principal Component Analysis is used to identify the central axis of the sampled cylinder, allowing to find the actual (expected value of the) radius and axis of the cylinder -- Application of k-cluster and transitive closure algorithms allow to identify particular areas of the cylinder which are specially deformed -- For both, the local areas and the global cylinder, a quantile analysis allows to numerically grade the degree of deformation of the cylinder -- The algorithms implemented are part of the CYLWEAR system and used to assess local and global wear cylindersÍtem Using Gröbner Bases in Kinematic Analysis of Mechanisms(Birkhäuser Verlag, 1996) Ruíz, Óscar E.; Ferreira, Placid M.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE