Combining Dynamic Modeling With Geometric Constraint Management to Support Low Clearance Virtual Manual Assembly

This research presents a novel approach to virtual assembly that combines dynamic modeling with geometric constraint-based modeling to support low clearance manual assembly of CAD models. This is made possible by utilizing the boundary representation solid model data available in most contemporary CAD representations, which enables (a) accurate collision/physics calculations on exact model definitions, and (b) access to geometric features. Application of geometric constraints during run-time, aid the designer during assembly of the virtual models. The feasibility of the approach is demonstrated using a pin and hole assembly example. Results that demonstrate the method give the user the ability to assemble parts without requiring extensive CAD preprocessing and without over constraining the user to arrive at predetermined final part orientations. Assembly is successful with diametral clearance as low as 0.0001 mm, as measured between a 26 mm diameter hole and pin

Robot virtual prototype in ADAMS

Tato práce se zabývá vytvořením virtuálního modelu robotu v ADAMS a co-simulačním propojením tohoto modelu s návrhem řízení v Matlab/Simulink. Robotem je segway Pierot vytvořený v rámci předchozích závěrečných prací. Obsahem této práce je vytvoření multi-body modelu, volba pohonu vytvoření co-simulačního propojení a samotná co-simulace.The goal of this work is to create virtual model of robot in ADAMS and co-simulation link between ADAMS and control system in Matlab/Simulink. Robot is segway robot called Pierot, created as the result of past final works. In this work is described creation of robot's multi-body model, choice of the motor, creation of co-simulation link and co-simulation itself.

A Systematic Approach to Constructing Incremental Topology Control Algorithms Using Graph Transformation

Communication networks form the backbone of our society. Topology control algorithms optimize the topology of such communication networks. Due to the importance of communication networks, a topology control algorithm should guarantee certain required consistency properties (e.g., connectivity of the topology), while achieving desired optimization properties (e.g., a bounded number of neighbors). Real-world topologies are dynamic (e.g., because nodes join, leave, or move within the network), which requires topology control algorithms to operate in an incremental way, i.e., based on the recently introduced modifications of a topology. Visual programming and specification languages are a proven means for specifying the structure as well as consistency and optimization properties of topologies. In this paper, we present a novel methodology, based on a visual graph transformation and graph constraint language, for developing incremental topology control algorithms that are guaranteed to fulfill a set of specified consistency and optimization constraints. More specifically, we model the possible modifications of a topology control algorithm and the environment using graph transformation rules, and we describe consistency and optimization properties using graph constraints. On this basis, we apply and extend a well-known constructive approach to derive refined graph transformation rules that preserve these graph constraints. We apply our methodology to re-engineer an established topology control algorithm, kTC, and evaluate it in a network simulation study to show the practical applicability of our approachComment: This document corresponds to the accepted manuscript of the referenced journal articl

Haptic Gdraw: A fun and Easy to Use 3D Haptically Enhanced Sculpting Program

We have developed a simple haptically-enhanced 3D sculpting application which utilizes Hermite spline-based primitives as building blocks to construct more complex solid models. To accomplish this, we have constructed a VR work environment which is intuitive and whose control affordances are made clear through the use of graspable handles. Haptics is used to support handle selection and provide physical constraints on handle movements consistent with their visual affordances. Our goal is to demonstrate how relatively simple haptic force constraints can combine with a visually intuitive and compelling environment to enable a program that is fun and easy to use

A finite element framework for modeling internal frictional contact in three-dimensional fractured media using unstructured tetrahedral meshes

AbstractThis paper introduces a three-dimensional finite element (FE) formulation to accurately model the linear elastic deformation of fractured media under compressive loading. The presented method applies the classic Augmented Lagrangian(AL)-Uzawa method, to evaluate the growth of multiple interacting and intersecting discrete fractures. The volume and surfaces are discretized by unstructured quadratic triangle-tetrahedral meshes; quarter-point triangles and tetrahedra are placed around fracture tips. Frictional contact between crack faces for high contact precisions is modeled using isoparametric integration point-to-integration point contact discretization, and a gap-based augmentation procedure. Contact forces are updated by interpolating tractions over elements that are adjacent to fracture tips, and have boundaries that are excluded from the contact region. Stress intensity factors are computed numerically using the methods of displacement correlation and disk-shaped domain integral. A novel square-root singular variation of the penalty parameter near the crack front is proposed to accurately model the contact tractions near the crack front. Tractions and compressive stress intensity factors are validated against analytical solutions. Numerical examples of cubes containing one, two, twenty four and seventy interacting and intersecting fractures are presented