Shuming Gao

Automatic recognition of interacting machining features based on minimal condition subgraph

Abstract This paper presents a methodology for efficiently recognizing both isolated and interacting features in a uniform way. The conventional, graph-based recognition method is combined with hint-based feature recognition to recognize and extract alternative interpretations of interacting features. First all isolated (non-intersecting) features are recognized based on a Manufacturing Face Adjacency Graph. Interacting features are then recognized based on the features minimal condition subgraph (MCSG) that is used as a feature hint. Unlike Previous hint-based recognition methods, the MCSGs of all features are defined, generated and completed in a uniform way, independent of the feature type. Hints are defined by an Extended Attributed Adjacency Graph, generated by graph decomposition and completed by adding virtual links, corresponding to entities lost by interactions. An efficient algorithm for generating virtual links is developed. A new classification of feature interactions is also presented.

A robust hole-filling algorithm for triangular mesh

This paper presents a novel hole-filling algorithm that can fill arbitrary holes in triangular mesh models. First, the advancing front mesh technique is used to cover the hole with newly created triangles. Next, the desirable normals of the new triangles are approximated using our desirable normal computing schemes. Finally, the three coordinates of every new vertex are re-positioned by solving the Poisson equation based on the desirable normals and the boundary vertices of the hole. Many experimental results and error evaluations are given to show the robustness and efficiency of the algorithm.

Real-Time Collaborative Design With Heterogeneous CAD Systems Based on Neutral Modeling Commands

This paper presents an integration-based solution for developing a real-time collaborative design (co-design) platform on heterogeneous computer-aided design (CAD) systems. Different from the visualization-based approaches, the product models are allowed to be constructed and modified from various sites together in the proposed collaborative design platform. Our approach is based on a mechanism for the translation between system modeling operations (SMOs) and neutral modeling commands (NMCs). Every operation given by a user on one site is translated into a NMC and transmitted to all the other sites through the network, and then the received NMC is converted into corresponding SMOs on every other site, instantaneously. Since only the commands but not the product data are transferred, the data size under transmission is greatly reduced, so that a real-time synchronization can be achieved with a standard network bandwidth. In addition, by developing system-dependent SMO↔NMC translators on different client CAD systems, users on different sites could join the collaboration by using their familiar CAD systems; this is the benefit that cannot be offered by the homogeneous co-design systems. The prototype implementation proves that our approach works well for integrating various current popular commercial CAD systems into a real-time collaborative design platform.

Design reuse oriented partial retrieval of CAD models

As a huge number of 3D CAD models is generated each year, retrieval of 3D CAD models is becoming more and more important for achieving design reuse. However, the existing methods for partial retrieval of 3D CAD models are very few and far from the requirements of design reuse. In this paper, we present an approach to partial retrieval of 3D CAD models for design reuse. The criteria for determining whether a subpart of 3D CAD models is reusable for design is defined first. Based on the criteria defined, all the design reusable subparts involved in the 3D CAD models in the library are automatically extracted and stored in the library as reference models. Moreover, each design reusable subpart in the library is represented by all its local matching regions in a hierarchical way so as to support multi-mode partial retrieval. In our approach, three partial retrieval modes including normal retrieval, exact retrieval and relaxed retrieval are defined to meet various partial retrieval requirements of design reuse such as the incomplete and vague queries during the early design stage. And the multi-mode partial retrieval is achieved by performing multi-mode matching and similarity assessment between the query and the design reusable subparts in the library indexed by bitmap. Experimental results are presented to demonstrate the effectiveness of the approach.

A Robust Hole-Filling Algorithm for Triangular Mesh

Summary form only given. This paper presents a novel hole-filling algorithm that can fill arbitrary holes in triangular mesh models. First, the advancing front mesh technique is used to cover the hole with newly created triangles. Next, the desirable normals of the new triangles are approximated using our desirable normal computing schemes. Finally, the three coordinates of every new vertex are re-positioned by solving the Poisson equation based on the desirable normals and the boundary vertices of the hole. Many experimental results and error evaluations are given to show the robustness and efficiency of the algorithm.

MIVAS: A Multi-Modal Immersive Virtual Assembly System

Evaluation and planning of assembly processes in virtual environments have become an active research area in engineering community. However, planning of complex assemblies in virtual environments, especially large-scale virtual environments, is still hindered by limitations like unnatural user interaction, insufficient frame rates, and deficiencies in processing of assembly constraints. In this paper, we present MIVAS, a Multi-modal Immersive Virtual Assembly System. By viewing the virtual assembly system as a finite state machine, we incorporate tracked devices, force feedback dataglove, voice commands, human sounds, fully immersive 4-sided CAVE, together with optimization techniques for both complex assembly models and assembly operations to provide for engineers an intuitive and natural way of assembly evaluation and planning. Testing scenarios on disassembling different components of an intelligent hydraulic excavator are described. Special attention is paid upon such technical issues as interface between CAD packages and the CAVE virtual environment, natural and intuitive user interaction including realistic virtual hand interaction and force feedback, intelligent navigation for assembly operations, and real-time display of complex assemblies.Copyright

Multi-level assembly model for top-down design of mechanical products

To enable next generation CAD tools to effectively support top-down design of products, a top-down assembly design process is refined from the traditional product design process to better exhibit the recursive-execution and structure-evolvement characteristics of product design. Based on the top-down assembly design process, a multi-level assembly model is put forward to capture the abstract information, skeleton information and detailed information involved. The multi-level assembly model is a meta-level implementation and is easy to be extended. Moreover, the inheritance mechanisms are explored to ensure the feasibility of information transferring and conversion between different design phases in the top-down assembly design process. A top-down assembly design sample is analyzed at length to show the application effects of the multi-level assembly model and the relevant inheritance mechanisms. In addition, a practical topic about the model adaptation of existing CAD systems is also discussed for a broader application of the top-down assembly design. Finally, the conclusion of the work and the future directions for further exploration are given.

Feature suppression based CAD mesh model simplification

Dynamic simulation and high quality FEA mesh generation need the CAD mesh model to be simplified, that is, suppressing the detailed features on the mesh without any changes to the rest. However, the traditional mesh simplification methods for graphical models can not satisfy the requirements of CAD mesh simplification. In this paper, we develop a feature suppression based CAD mesh model simplification framework. First, the CAD mesh model is segmented by an improved watershed segmentation algorithm, constructing the region-level representation required by feature recognition. Second, the form features needing to be suppressed are extracted using a feature recognition method with user defined feature facility based on the region-level representation, establishing the feature-level representation. Third, every recognized feature is suppressed using the most suitable one of the three methods, i.e. planar Delaunay triangulation, Poisson equation based method, and the method for blend features, thus simplifying the CAD mesh model. Our method provides an effective way to make CAD mesh model simplification meet the requirements of engineering applications. Several experimental results are presented to show the superiority and effectivity of our approach.

A Survey on Partial Retrieval of 3D Shapes

Content-based shape retrieval techniques can facilitate 3D model resource reuse, 3D model modeling, object recognition, and 3D content classification. Recently more and more researchers have attempted to solve the problems of partial retrieval in the domain of computer graphics, vision, CAD, and multimedia. Unfortunately, in the literature, there is little comprehensive discussion on the state-of-the-art methods of partial shape retrieval. In this article we focus on reviewing the partial shape retrieval methods over the last decade, and help novices to grasp latest developments in this field. We first give the definition of partial retrieval and discuss its desirable capabilities. Secondly, we classify the existing methods on partial shape retrieval into three classes by several criteria, describe the main ideas and techniques for each class, and detailedly compare their advantages and limits. We also present several relevant 3D datasets and corresponding evaluation metrics, which are necessary for evaluating partial retrieval performance. Finally, we discuss possible research directions to address partial shape retrieval.

A flexible assembly retrieval approach for model reuse

Nowadays, growing quantities of product models are created in industries. Usually, these models contain abundant design knowledge, either explicit or implicit, in various disciplines. As an approach to taking full advantage of the design knowledge embedded, model reuse plays an increasingly important part in complex product design and innovative design, in which enormous time and cost can be saved. While model retrieval is a natural and promising way to help designers find the right models for quick and accurate reuse, the retrieval technology for assemblies is yet to reach maturity since the previous text-based or low-level content-based assembly retrieval could not fully support the needs of users. In this paper, a new assembly retrieval approach is presented, based on which, users can input flexible queries, either rough or precise, to retrieve efficiently the whole or partial assemblies they want from the product library. First, a multilevel assembly descriptor supporting various searching requirements is elaborated, which collects different levels of information in assembly models. Then, the corresponding matching and similarity assessment methods with well-balanced efficiency and discriminability are given to evaluate the differences between assembly models. Moreover, an indexing mechanism for accelerating assembly retrieval, especially the partial retrieval, is presented to filter the unmatchable models quickly. Finally, an assembly retrieval prototype system is implemented, and the experimental results are analyzed to verify the advantages of the flexible assembly retrieval approach.