Narrow Results

Choosing the right number and type of elements in modern commercial finite element tools is a challenging task. It requires a broad knowledge about the theory behind or much experience by the user. Benchmark tests are a common method to prove the element performance against analytical solutions. However, these tests often analyze the performance only for single elements. When investigating the complete mesh of an arbitrary structure, the comparison of the element’s performance is quite challenging due to the lack of closed or fully converged solutions. The purpose of this paper is to show a high-precision comparison of eigenfrequencies of a real structure between experimental and numerical results in the context of an element performance check with respect to a converged solution. Additionally, the authors identify the practically relevant accuracy of simulation and experiment. Finally, the influence of accuracy with respect to the number of elements per standing structural bending wave is shown.

In close collaboration with wood sculptor Brent Collins, a computer program has been developed to explore and optimize different configurations of his type of abstract, geometrical wood sculptures. The family of sculptures addressed by this program can be understood as rings of saddle surfaces resulting from a toroidal warping of a truncated section of Scherk's second minimal surface. The result of setting different values for the number of holes, the amount of twist, and for several other parameters of these virtual sculptures can be explored at interactive speeds, providing immediate feedback to the designer. The best solution found is sliced into final construction blueprints from which the artist then constructs a real wood sculpture.

A second-generation version of this program takes a much broader and more modular approach to parameterized modeling. It can prototype any shape that can be described as a 3-dimensional shape element iterated along an arbitrary space curve, while being suitably warped to fit the local curving of the specified path. The stimulating collaboration with Brent Collins continues.

Reconciling scene realism with interactivity has emerged as one of the most important areas in making virtual reality feasible for large-scale CAD data sets consisting of several millions of primitives. Level of detail (LoD) and multi-resolution modeling techniques in virtual reality can be used to speed up the process of virtual design and virtual prototyping. In this paper, we present an automatic LoD generation and rendering algorithm, which is suitable for CAD models and propose a new multi-resolution representation scheme called MRM (multi-resolution model), which can support efficient extraction of fixed resolution and variable resolution for multiple objects in the same scene. MRM scheme supports unified selective simplifications and selective refinements over the mesh. Furthermore, LoD and multi-resolution models may be used to support real-time geometric transmission in collaborative virtual design and prototyping.

The aim of this research is develop an effective virtual prototyping system for product development using augmented reality technology. Before a virtual environment is put into work for design and development, some way of quantifying errors or uncertainties in the computer model is needed so that a robust and reliable system can be achieved. This paper presents the calibration, registration, and preparation of an augmented reality environment with 3D tracking and dynamic simulation technologies for studying dynamic systems, such as parts orientation devices. With such virtual prototyping techniques, engineers can run high-fidelity simulation to test new materials, components, and systems before investing valuable resources in construction of physical prototypes.

Industrial adoption of PKMs may be eased by the availability of methodologies and integrated tools able to analyze in a short time PKMs of any architecture, providing the key data needed to design the machine. The proposed Virtual Prototyping Environment for PKM Analysis answers to these requirements, quickly estimating not only the reachable workspace, the Jacobian conditioning, but also the actuators' effort, internal loads in the mechanical structure and the effects of lumped structural compliances. A description of the developed VPE-PKM, based on a commercial Multi-body package, is given. Its effectiveness is shown, presenting results obtained by ITIA-CNR during the design of a 3 dof translational PKM for light deburring operations.

Presented in the paper is a virtual factory simulator (VFS) framework as a 3D solid-based factory simulator to be used as a line prototyping tool for an AMS (automated manufacturing system). The VFS framework supports a 3D resource & factory layout modeling, a physical emulation, and a performance simulation: the physical emulation is used for the kinematics simulation, interference check between resources, and the generation & verification of device program; and the performance simulation is used for the material flow & control logic evaluation and system performance evaluation. The proposed VFS framework supports a fully integrated graphical modeling environment for emulation scenario modeling and material flow & control logic modeling. Therefore, the proposed VFS meets the modeling requirements of high modeling power, ease of model building & validation, and ease of communication with stakeholders compared to other commercial system. Based on the VFS framework, a virtual factory simulator named VM-Factory^® has been developed in C++ with OpenGL and a DEVS engine, and its validity was demonstrated by applying it in constructing a virtual factory of an FMS (flexible manufacturing system).

Kinematic simulation in virtual environment is the key technique of product performance evaluation. Based on graph theory, the paper gives the integrity knowledge expression of product motion model, including the topological structure, motion dimension and driver information. It builds a solver of kinematic analysis for planar linkage interactive-oriented, which based on auto-identifying of Assur groups and auto-generating of kinematic analysis routine by operating labeled adjacency matrix. A new method of kinematic simulation for virtual prototyping is put forward based on the kinematic mapping of pseudo-linkage. The achievements have been applied to the kinematic simulation of internal-combustion engine, punch and crusher.

The dynamic model of a grab ship unloader's swing exhibits strong nonlinear characteristics due to the changeable rope length and the changeable center of gravity of the grab in the actual work process. In fact, it is difficult to simulate the changes using traditional mathematical modeling methods. Thus, typical swing control methods based on mathematical models, such as the input shaping methods, are often difficult to match to the actual operation of the ship unloader. In this paper, a dynamic simulation model of a grab ship unloader is built by using virtual prototyping technology. This model also uses the ADAMS/Cable module to simulate the changes of grab rope length, and further simulates the opening and closing conditions of the grab. Afterwards, the commonly used input shaping control methods are simulated and analyzed in the established virtual prototype model of grab ship unloader. The results show that the virtual prototype model established by this paper can simulate the whole working process of grab ship unloader appropriately and enables verification of the swing control effects of different swing control strategies.