Accurate reduction of two-dimensional curve noises is crucial to metrology and reverse engineering. In this paper we propose a set of schemes for two-dimensional curve denoising. Our approach consists of three main steps: 1) feature-based pre-smoothing of noised polylines; 2) curve partitioning of polylines into different regions; 3) two hybrid denoising schemes of arbitrary polylines with noises. Numerical experiments indicate the effectiveness of our approach against existing methods.
This paper presents a case study examining design exemplar technology implemented as a search and retrieval tool fortire mould inserts. Limitations of using the geometric-based exemplar approach, such as tediousness of authoring exemplars and time complexity, are identified and addressed through a new parametric-based exemplar approach. Here, the maxima and minima are calculated based upon the specifications of the query mould insert. The design exemplar is demonstrated to be useful primarily in prototyping query mechanisms. Ultimately, customer requirements necessitated implementing the parametric approach as a dedicated software package grounded on the exemplar based prototyped query mechanism.
A useful way to generate solutions to engineering design problems is to compare the solutions of design problems similar to the one at hand and validate the solutions to satisfy the new design requirements. This process involves evaluating the similarity between the design problem at hand and the various design problems in the repository. The purpose of this paper is to investigate the meaning and the use of similarity in engineering design. Various similarity theories in literature have been explored. Previous applications of these theories are limited to the retrieval of similar computer-aided design models and process plans. This paper extends the applications of these theories to the various stages of the design process.
Model reuse is typically facilitated by search and retrieval tools, matching the sought model with models in the case base or database. This paper looks at providing assistance to users authoring design exemplars, a new data structure to represent parametric and geometric design problems, by providing alternative configurations. Four distinct similarity metrics are proposed for model retrieval in an interactive modeling environment: entity similarity, relationship similarity, attribute similarity, and structural similarity. A brief review of graph matching literature has been provided, followed by a technical session showing the application of a set of derived similarity metrics.Keywords: design exemplar, CAD query language, retrieval, interrogation INTRODUCTIONIn engineering design, as with many other disciplines, knowledge or model reuse is sought to reduce workload and development effort. Model reuse is typically facilitated by search and retrieval tools, often matching sought models based upon "similarity metrics". For example, a large tire manufacturing firm in North America designs mold inserts for its tire treads. The tooling cost for each mold insert is approximately 2000$. Hence, in order to reduce the manufacturing cost, the designers retrieve inserts that are similar to the desired shape geometry in that, which fall within a specified tolerance envelope. Different strategies have been employed to retrieve similar models [13,19]. For example, shape-based search methods are used to retrieve 3-D models and sketches in which spherical harmonics are used in creating discriminating similarity measures [13]. An Engineering Advisory System (EAS) has been developed, which involves the retrieval of knowledge associated with 3-D models [19]. The system takes a 3-D shape as a query and converts it into two simpler "fingerprint representations": feature vectors and skeletal graph. Feature vectors represent the global shape or geometry of the object, whereas the skeletal graphs minimally represent the topology and the local geometry of the object. Examples of feature vectors include the Geometric Moment Invariants and Geometric Ratios. Search for similar models can be performed through a combination of these two representations. This paper examines similarity in engineering model authoring contexts, offers a set of metrics that might be employed in graph based model authoring, and demonstrates these metrics by an illustrative case study. Specifically, this approach is applied to the authoring of the design exemplar, a standard representation of mechanical engineering design problem knowledge [39]. These metrics are used in a system that offers the model developer, in this case the exemplar developer, options of existing models that are matched to what has been partially authored. As mentioned above, the design exemplar is a new data structure that has been developed to represent parametric and geometric design problems [7]. Most queries associated with mechanical engineering design include parametric and geometric v...
This thesis presents a case study examining the suitability of design exemplar technology as a CAD query tool for an industrial scenario. The search and retrieval of geometrically similar mold inserts to save tooling cost for a tire manufacturing company is taken as the case study. During the implementation of the design exemplar as a CAD search and retrieval tool, several limitations of it are identified, such as the difficulty and tediousness in authoring exemplars for real world problems. To overcome these limitations, a new mathematical-based exemplar approach (mathematical model) is developed for tire mold insert retrieval. This approach calculates a set of maxima and minima based on the specifications of the target mold insert and identifies similar molds that fall within these specifications. Though the mathematical model requires less effort to author the exemplar queries than the initial boundary envelope approach, it has an unreasonably high time complexity when implemented using design exemplar. A partially developed mathematical-based exemplar takes 30 seconds to run through a sample database of 10 mold inserts. Assuming that a fully built exemplar would take more time when run on a database of 55000 mold inserts as it would have more number of constraints added to it, the approach was not implemented through design exemplar tool. However, as this exemplar approach gives a satisfactory theoretical solution to the problem, the exemplar is hard-coded in an independent C++ program to suit the requirements at hand. The mathematical-model which is implemented in an independent C++ program successfully searches through the complete database of 5500 tire mold inserts, retrieving similar mold inserts, in a span of one second, a huge efficiency gain when compared with the traditional exemplar system. Apart from the time reduction for the search and retrieval, the exemplar inspired program has an additional advantage in that no geometrical entities must be handled to build exemplars. However, the mathematical model may result in several false positives that must be manually eliminated. In an experiment, 15 mold inserts were randomly selected from the database and were searched for similar mold inserts using the program developed. In the experiment, it was observed that there were no false negatives and the number of false positive ranged from 0 -2. Considering the size of the database which is roughly 5500 mold inserts, the mathematical still provides advantages in search and retrieval. It is still good because 5500 have been iii reduced on an average to 9. During the experiment, it as been found that 80 percent of the mold inserts which were tested have similar mold inserts. The design exemplar tool could have helped company to save the tooling cost of $184,000 per annum by providing them with a search and retrieval tool. However, it was not implemented because of some of the limitations mentioned above. Still the strategies of design exemplar are valid for querying CAD models. This is proved by the fact that ...
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