Y. P. Chen

Multi-User NC Machining Simulation over the WWW

The realisation of a virtual manufacturing system requires an open network environment to perform 3D graphics simulation or virtual reality information processing among multiple users. This paper introduces a prototype system that employs Java, the virtual reality modelling language (VRML) and the external authoring interface (EAI) to perform NC machining simulation. A client/server paradigm is adopted to construct a multi-user enabled interactive environment. A novel method is presented to update dynamically the geometry of a workpiece being cut in a VRML-based scene. In addition, the prototype system is analysed in terms of functionality and performance.

Geometric model simplification for distributed CAD

Abstract Visualization of CAD models in distributed design environment is an essential feature to support collaborative design. To efficiently transmit and render CAD models geometric simplification can be applied to CAD models. However, it is difficult to use available general geometric simplification algorithms because these algorithms are not designed to handle mechanical CAD parts. Applying general simplification on a CAD model would result in distortion of design features and make them unrecognizable to viewers. In this paper, a novel approach is proposed to exploit trimming information in CAD models to simplify their geometry. Visibility culling is integrated into this approach to facilitate selective refinements. The work introduced here aims to support visualization of multiple CAD models in a distributed CAD environment. Implementation details are included and case studies are demonstrated.

Real-time, dynamic level-of-detail management for three-axis NC milling simulation

The Z-buffer based NC milling simulation approach has been widely used in a number of commercial application softwares. However, this approach is essentially based on image and hence it has many drawbacks. Some polygon-based approaches have been presented to overcome these drawbacks, but these approaches are mostly not optimal. In order to achieve real-time simulation, the total number of polygons has to be reduced in these approaches, which results in poor image quality. Using those proposed level-of-detail mesh algorithms can reduce the number of polygons, but the majority of those algorithms are not suitable for dynamic real-time NC milling simulation. Therefore, it is necessary to develop an approach to reduce the number of polygons without much loss in image quality. An adaptive regular mesh decimation algorithm is proposed in this paper. It uses a quadtree to represent the milling surface and enabled flags are used to perform the optimization of the mesh, actual insertion and deletion operations of triangles do not exist. This algorithm can automatically adjust the polygon density to approximate the milling surface according to its changes in real-time, and numerical inspections of any area of the machined surface can be performed with full resolution.

Geometric Simulation of NC Machining Based on STL Models

Abstract Presently, simulation models In virtual CNC machining simulation can be generated using commercial CAD software to provide dynamic 3D interactive virtual environments specifically designed for visualizing and analyzing the functionality of CNC machine tools and the material removal processes. However, these models generated using different CAD software have distinct Individual formats, and are difficult to use in another simulation environment. This paper proposes to use the STL (stereollthography) models as the common models in machining simulation for bridging the Incompatibility between different CAD software systems. The simulation results in the STL model format can be immediately used in rapid prototyping to produce the prototype and design changes can be reflected quickly from these prototypes. This will serve as a useful guide for the designers to make the necessary changes along the design process.

A methodology for evaluating the manufacturing ability of equipment in virtual enterprises

This paper proposes a methodology for evaluating the manufacturing ability of equipment in a multi-agent-based virtual manufacturing enterprise by enveloping the manufacturing information of the various equipment as equipment agents. The manufacturing ability of equipment consists of two classes: the processing ability and the processing capability of the equipment. The processing ability of equipment indicates the tasks and operations that the equipment can perform, and is peculiar to the equipment. The processing capability of equipment shows the capability of the equipment to undertake and accomplish a specified task under some constraints, such as time and cost, and it depends on both the equipment and the task. It varies with different equipment and tasks, and at different times. The concept of an operation spectrum of equipment is introduced to verify the processing ability of the equipment, and methods are formulated to calculate the current capability of the equipment and estimate the cost for bidding for new tasks. The proposed methodology on the manufacturing ability of the equipment in a virtual enterprise can be implemented easily using equipment agents. This methodology can support the equipment agents to bid for new tasks as real independent agents in virtual manufacturing enterprises or multi-site enterprises.

Technical Section: Reflectance modeling for a textured object under uncontrolled illumination from high dynamic range maps

During the past several years, considerable work has been presented on the methods for measuring and modeling the observed reflectance properties of materials. However, most of these works have been done under controlled lighting configurations, and require a constant bidirectional reflectance distribution function (BRDF), which is a measure of the amount of light scattered by a medium from one direction into another, or a homogeneous material over the object regions. This paper discusses a method to estimate the reflectance properties of a textured object under uncontrolled illumination. Assuming that the object has a constant specular reflectance property over its surface, the BRDF can be approximated as a constant specular component and a spatially varying diffuse component. The proposed method will first approximate the illumination distribution of a scene from a set of high dynamic range (HDR) radiance maps of a light probe. Next, a patch on the surface of an object is selected; several HDR intensity maps of the patch taken under different viewing conditions are used to estimate the average specular reflectance parameters of this patch. With the separation of the specular component and the diffuse component of each sample, and using the separated diffuse component, the diffuse reflectance parameters for each point over the surface are next estimated. The test results show that the method is effective for textured objects with constant specular reflectance properties. The method can also be directly applied to objects with piecewise-smooth material, which means that although the surface of an object does not have a constant specular reflectance property; when sub-divided into many smaller meshes, the specular parameter of each mesh can be regarded as uniform.

Novel NPHS1 gene mutations in a Chinese family with congenital nephrotic syndrome

Congenital nephrotic syndrome (CNS) of the Finnish type (CNF; MIM: 256300) is a rare autosomal recessively inherited disease characterized by a large placenta, massive proteinuria, marked edema and clinical onset within the first three months of life. Mutations of NPHS1 gene were the most well-recognized causes of CNF, which was firstly and mostly described in Finland with two main defects: Finmajor (c.121delCT) and Finminor (c.3325C>T). In other countries, the two typical Finnish mutations were rarely found, but a wide variety of different mutations have been described (Heeringa et al. 2008; Schoeb et al. 2010), including missense, nonsense, deletions, insertions and splice site. To date, about 183 different NPHS1 mutations in CNF have been reported, but only a few have been reported in China (Shi et al. 2005; Wu et al. 2011; Yu et al. 2012). In this study, we report a Chinese family with two CNF patients and identified two novel heterozygous missense mutations in exons 15 and 16 of NPHS1 gene.

An efficient 3d registration method using markerless image in AR-Based CNC machining simulation

In this paper we present a model-based approach for the real-time recognition and registration for augmented reality applications. It does not need any artificial markers to track the target. What the system need is the 3D model of target and some representative learning images. The most contribution of our work is that we put forward an idea of transferring the construction of correspondent point pairs between model and real scenes to the calculation of the affine matrix between a pair of 2D images. Our method is based on a two-stage process. In the first stage, a set of features is learned from the training images. The second stage matches the learned features with that obtained from the real scenes. If the target is recognized, the final correspondences used for registration are built with the help of the calculated affine matrix. The system is robust to large viewpoint changes and partial occlusions. And in the premise of stability assurance, the system has a good performance in reducing the computation burden.