Computer-aided Design Problems Research Articles

Subdivision Schemes Based on Weighted Local Polynomial Regression: A New Technique for the Convergence Analysis

The generation of curves and surfaces from given data is a well-known problem in Computer-Aided Design that can be approached using subdivision schemes. They are powerful tools that allow obtaining new data from the initial one by means of simple calculations. However, in some applications, the collected data are given with noise and most of schemes are not adequate to process them. In this paper, we present new families of binary univariate linear subdivision schemes using weighted local polynomial regression which are suitable for noisy data. We study their properties, such as convergence, monotonicity, polynomial reproduction and approximation and denoising capabilities. We establish conditions that connect the weight function with two essential properties: noise elimination and approximation capability. We propose a multi-objective optimization problem for improving these two capabilities and conclude that only some weight functions are Pareto optimal. For the convergence study, we develop some new theoretical results. Finally, some examples are presented to confirm the proven properties.

Adaptive Spline Surface Fitting With Arbitrary Topological Control Mesh.

Reconstructing a spline surface from a given arbitrary topological triangle mesh is a fundamental and challenging problem in computer-aided design and engineering. This article introduces a novel surface fitting method utilizing G-NURBS capable of handling control meshes with arbitrary topologies. This method employs adaptive control point adjustment, guided by the geometric attributes of the input model, ensuring precise representation of sharp features such as edges and corners. Two primary strategies are employed: A parameter correspondence approach designed for sharp features and a control mesh iterative refinement technique that incorporates geometrical feature information. The proposed method has been tested and evaluated on various CAD models to demonstrate its effectiveness. This method can achieve higher fitting accuracy while faithfully preserving the geometrical features with fewer control points.

The Development of B-Splines for CAD.

A description is given of the milieu, including people, events, and research activities, surrounding the development of the author's doctoral thesis, "Applications of B-spline Approximation to Geometric Problems of Computer-Aided Design." Although initially slow to become adopted, today nonuniform B-splines have become the international de facto standard representation in the CAD industry.

Определение управляющих воздействий и энергозатрат при программном движении манипулятора

The paper presents the modeling of the solution to one of the problems of mechanics - the automated control of the manipulator used in the forestry industry for moving operations at various stages of the technological process. A unified model has been developed that allows generating control actions and energy consumption of the object under study. As a result of solving the problem, a system of equations was obtained for determining the control moment and control force, which allow the manipulator to be set in motion, as well as to determine the energy consumption for the implementation of the program motion, in which the load moves at a given speed from point a to point b along a straight line inclined at a given angle to the horizon. The proposed algorithm is generalized for solving computer-aided design problems and is a simulation experiment. The software solution is implemented in two forms. In the first module, the database is filled with the initial metric, angular and physical and mathematical characteristics of the manipulator. In the second, according to the unified model described above, the indicators are calculated that are necessary for the movement of the object and characterize the dynamics of movement, as well as the necessary energy consumption for performing the operations performed. The possibility of converting the calculated values from the database into an MS Excel table is provided.

Boolean Satisfiability Methods for Modern Computer-Aided Design Problems in Microelectronics

Boolean Satisfiability Methods for Modern Computer-Aided Design Problems in Microelectronics

C2F-3DToothSeg: Coarse-to-fine 3D tooth segmentation via intuitive single clicks

3D tooth segmentation is a challenging fundamental problem in computer-aided design (CAD) systems for orthodontic treatment planning. Existing methods of tooth segmentation cannot meet the requirements for both efficiency and accuracy. This paper presents a coarse-to-fine 3D tooth segmentation algorithm, called C2F-3DToothSeg, to improve tooth segmentation. The algorithm consists of two steps: extraction of the coarse gum line and optimization of this line. A concavity-sensitive harmonic field is searched in a local region of entire dental meshes to produce a series of isolines. The best isoline is selected as the coarse gum line, which is then optimized by a heuristic feature line extraction scheme to yield an accurate gum line. Extensive visual and numerical experiments demonstrate that our C2F-3DToothSeg has better overall performance in accuracy and efficiency compared to other existing methods directly applicable in orthodontic CAD systems. A point on the tooth surface is loosely found to locate the center zone of each individual tooth via a simple intuitive single click of the operation. The experiments also show that our method is robust to different complex dental models; for example, it copes with bulge bubbles, decay and cavity issues, and dental accessories.

Volumetric and dimensional accuracy assessment of CAD-CAM–manufactured dental prostheses from different materials

Statement of problemIn computer-aided design and computer-aided manufacturing (CAD-CAM) dentistry, the CAD of the prosthesis represents the clinical prerequisite design to restore the treated tooth. However, how closely the CAM prosthesis shape matches the CAD, particularly in relation to different materials, is unclear. PurposeThe purpose of this in vitro study was to evaluate onlays designed and manufactured with the same CAD-CAM system but manufactured with different materials. Material and methodsA single standard tessellation language (STL) model was used to produce 6 composite resin onlays, 6 leucite glass-ceramic onlays, and 6 lithium disilicate glass-ceramic onlays. The onlays were digitized by using an X-ray microtomographic protocol with a metrological calibration. The CAD model was then compared with the scans of the different onlays. An analysis by region of interest was then carried out to assess the accuracy and reliability of the dimensional accuracy. ResultsThe composite resin and the lithium disilicate glass-ceramic had the best dimensional accuracy. The leucite glass-ceramic exhibited a lack of trueness linked to consistent overmilling. The composite resin had less peripheral chipping than the glass-ceramics. ConclusionsThe composite resin and the lithium disilicate glass-ceramic material exhibited satisfactory dimensional accuracy. Milling the glass-ceramic before crystallization considerably improved dimensional accuracy.

Multicriteria optimization in the problem of computer-aided design of hybrid solar energy systems

This paper reports an approach to optimizing the structure of a hybrid solar energy system (HSES), used in the task of automated design, under two modes: independent and connected to the network. The proposed HSES includes a solar energy system (SES), an energy storage system (ESS) powered by rechargeable batteries (RBs), a set of diesel generators (DGs), and a network-connecting system. This paper has identified models of the HSES elements' power and proposed a control algorithm based on rules that assess the state of the system during operation. The energy models in conjunction with the control algorithm make it possible to model the system's operation stage over a predefined time interval. The proposed approach is based on solving a multicriteria optimization problem (MCO). MCO takes into consideration the minimization of system costs and the total cost of the system, minimizing fuel use, maximizing reliability, and minimizing the use of non-renewable energy sources. A solution to the MCO problem is based on using a Pareto-optimal solution search algorithm, underlying which is the NSGA-II genetic algorithm employing the proposed set of crossbreeding, mutation, and breeding operators. The devised procedure makes it possible to determine the structure of HSES, which includes a set of the number of solar panels, RBs, and DGs. The result is three variants of HSES for a household for two people (Kyiv, Ukraine), under an autonomous mode and in the regime connected to the electricity grid. Given the possibility of selling electricity at a green tariff during the year, the reported solution makes it possible to reduce the estimated cost of the system by up to 45 %. The use of simulation has helped conduct a detailed analysis of the system's performance throughout the year

Application of parallel and distributed processing techniques for computer-aided design problems

Application of parallel and distributed processing techniques for computer-aided design problems

Possibilities of computer-aided design of flange connections in pipe fittings based on the nanoCAD Mechanics graphic editor

The article discusses the possibilities of using the nanoCAD Mechanics editor, developed by the Russian company Nanosoft JSC (www.nanocad.ru), for the automated design of pipeline sections with threaded flange connections. It is shown that for solving the problems in computer-aided design, there are various tools presented in the ribbon interface of the program. Such tools include the Standard command from the Standard group on the Mechanics tab, which opens the Select Parts dialog box. In the Select Parts dialog box, a functional panel of the Element Base is built-in, including: folders Pipeline fittings and Welded pipelines; dropdown catalogs Flanges, Gaskets and Pipes with element sizes that comply with ESKD standards. On the “Mechanics” tab, the Bolt connection tool from the Design group with the Mounting Details dialog box included in it is used, after calling it and specifying the start and end points of the connection, the Mounting Details dialog box opens. The last lists show bolts made according to ESKD standards. Insertion of flanges, gaskets, bends, pipes and bolt joints and their automated selection are carried out by left-clicking and selecting parameters in the corresponding dialog boxes.

DESIGN TIMED FSM WITH VHDL MOORE PATTERN

Context. The relevance of the work consists in the development of computer-aided design methods for automatic real-time logic control devices by developing a single template in a synthesized subset of the hardware description language in the style of automatabased programming with implementation on the PLD hardware platform (FPGA, CPLD). Development of the description template for timed control finite state machines (FSM) in the hardware description language VHDL, automated synthesis and implementation of the model in PLD (FPGAs, CPLDs) using Xilinx ISE, subsequent analysis of the received circuit implementation for compliance with values of timing parameters of the circuit after implementation.Objective. The aim of the work is to develop principles for constructing models of timed control FSM in the VHDL hardware description language. In this work, we solved the problem of constructing a pattern for describing models of timed control Moore FSM using VHDL, automated synthesis and implementation of the obtained VHDL model in PLDs (FPGA, CPLD) using Xilinx ISE and subsequent analysis of the resulting circuit implementation for compliance with values of timing parameters of the circuit after implementation.Method. Realization of models’ parameters of timed FSM in logical control systems using VHDL statements. Development of VHDL language constructions of timed FSM models for timing parameters implementation that provide the correct automated synthesis and implementation of these models in PLDs (FPGA, CPLD) using CAD tools Xilinx ISE.Results. Synthesis and implementation of proposed templates of VHDL-models of timed control Moore FSM in logic control systems by XILINX ISE CAD tools confirmed the receipt of not redundant circuits in PLD (FPGA, CPLD), and simulation after implementation showed the efficiency of such models.Conclusions. The work solves the problem of computer-aided design of timed control FSM in real-time logic control systems. To solve this problem, VHDL-models of timed control Moore FSM were developed, which made it possible to implement control FSM with time constraints, timeouts and output delays. Automated synthesis and simulation of VHDL models based on the developed templates confirmed the efficiency and correctness of the proposed models.The scientific novelty of the work consists in the further development of methods for constructing templates of HDL models of timed control Moore FSM, which made it possible to implement control FSM with time constraints, timeouts and output delays, as well as perform their correct automated synthesis and simulation.The practical value of results is in the development of procedures for constructing VHDL models of timed Moore control FSM in real-time logic control systems, which made it possible to automate the synthesis of control FSM taking into account the possibility of processing external events and implementing arbitrary delays for output signals and to increase the flexibility and speed of designed systems. The developed procedures can be useful for designers of timed control FSM in Xilinx ISE.

Analyzing Clustering and Partitioning Problems in Selected VLSI Models

As the modern integrated circuit continues to grow in complexity, the design of very large-scale integrated (VLSI) circuits involves massive teams employing state-of-the-art computer-aided design (CAD) tools. An old yet significant CAD problem for VLSI circuits is physical design automation. In physical design automation, we need to compute the best physical layout of millions to billions of circuit components on a tiny silicon surface. The process of mapping an electronic design to a chip involves several physical design stages, one of which is clustering. Even for combinatorial circuits, there are several models for the clustering problem. In particular, we consider the problem of clustering without replication in combinatorial circuits with a view towards minimizing delay (CN). The corresponding problem with replication has been well-studied and solvable in polynomial time. However, replication can become expensive when it is unbounded. Consequently, CN is a problem worth investigating. We establish the computational complexities of several variants of CN. Additionally, we obtain approximability and inapproximability results for some NP-hard variants of CN. We also present approximation and exact exponential algorithms for some variants of CN. We prove that for some cases there exists an approximation factor of strictly less than two and that our exact exponential algorithms beat brute force. Furthermore, we provide the first parameterized approximation algorithm in which the approximation ratio is also a parameter.

To the problem of computer-aided design of gear-and-leverage mechanisms

The possibilities of using gear-lever mechanisms in modern mechanical engineering are described on the example of three mechanisms from different areas of industry. For practical application, a method of structural and kinematic analysis of gear-lever mechanisms is proposed, implemented using the program module developed by the authors, and an algorithm for kinematic calculation of a gear-lever three-wheeled articulated four-link, as the most common and used in mechanical engineering, is given.

DEVELOPMENT OF TECHNOLOGY EDUCATION STUDENTS’ ICT COMPETENCE WHILE TEACHING COMPUTER-AIDED FASHION DESIGN

The present paper deals with the problem of CAD (computer-aided design) competence formation of would-be teachers of technology and vocational school teachers. It is noted that for fashion industry to develop, it is necessary that its professionals should have both the knowledge of basic communication technologies and foundations of using CAD. ICT competence is necessary for trainee teachers of technology and vocational education specialists both for their educational activity and for successful creation of outfit models using computer techniques. The aim of the research lies in grounding the list of software equipment to be used by trainee teachers of technology and vocational school teachers to provide effective learning of CAD in professional sphere. The introduction to professional-oriented software is realized in higher education institutions of Ukraine during the course of “Basics of computer aided design”, after a preparatory course “Information Technologies” Information technologies are used in fashion industry for creating new models, equipment management, and for maintaining the life cycle of outfits. Hereby presented is a systemized list of computer software tools for professional purposes to be used in automated workstation of the designer: software tools for correct and safe system component management; software for file creation and information sharing; CAD-subsystems. The content of the course “Basics of computer aided design” have been described. Practical approbation has proved effectiveness of the developed syllabus along with the methodological support of the course “Basics of computer-aided design”. The results of the investigation are important for grounding the content of study for trainee teachers of technology and specialists of vocational education, as well as for professionals in fashion industry.

Numerical Proper Reparametrization of Space Curves and Surfaces

Simplifying rational parametrizations of surfaces is a basic problem in CAD (computer-aided design). Reducing their tracing index, called proper reparametrization, is an important simplification way. Most existing proper reparametrization work is symbolic. Yet in practical environments the surfaces are usually given with perturbed coefficients hence need a numerical technique of reparametrization considering the intrinsic properness of the perturbed surfaces. We present algorithms for reparametrizing a numerically rational space curve or surface. First, we provide an efficient way to find a parametric support transformation and compute a reparametrization with proper parametric support. Second, we develop a numerical algorithm to further reduce the tracing index, where numerical techniques such as sparse interpolation and approximated GCD computations are involved. We finally provide the error bound between the given rational curve/surface and our reparametrization result.

Research on Determination of Optimum Parameters for The Lower Extremity Exoskeleton

Lower extremity exoskeleton is a device that enables the user to sit down without the need of using a chair. The design of the exoskeleton has to satisfy multiple objectives, many of which are defined by the body of the user. Most CAD (Computer aided design) programs nowadays still have not added multiple-objective evolutionary algorithms (EAs). This paper presents an application of NSGA-II (Non-dominated sorting genetic algorithm II) and AMO (Adaptive-Multiple objectives) in order to solve the problem of multiple-objective optimization in designing Lower extremity exoskeleton. Moreover, the Box-Behnken design (BBD) - based response surface methodology was also used to investigate the effects of the number of initial samples, the number of samples per iteration and the maximum number of iterations on AMO. Then, the Pareto-optimal frontier of feasible points was carried out for the alternative solutions of design problem. In addition, the TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) method was employed in order to support the decision makers in deciding the engineering optimum parameters. The optimum parameters obtained are αmin = 24.81°, αmax=1 15.08° and (Wd = 177.2°. With the same input values, AMO and NSGA-II gave the same output values, however the number of samples which are used to determine convergence of AMO only equals to 0.66 that of NSGA-II. The method in this study is advantageous for multiple-objective optimization in CAD problems.

Clustering without replication in combinatorial circuits

The modern integrated circuit is one of the most complex products engineered to date. It continues to grow in complexity as years progress. As a result, very large-scale integrated (VLSI) circuit design now involves massive design teams employing state-of-the-art computer-aided design (CAD) tools. One of the oldest, yet most important CAD problems for VLSI circuits is physical design automation, where one needs to compute the best physical layout of millions to billions of circuit components on a tiny silicon surface (Lim in Practical problems in VLSI physical design automation, Springer, Dordrecht, 2008). The process of mapping an electronic design to a chip involves several physical design stages, one of which is clustering. Even for combinatorial circuits, there exists several models for the clustering problem. In particular, we consider the problem of clustering in combinatorial circuits for delay minimization, without permitting logic replication (CN). The problem of clustering for delay minimization when logic replication is allowed (CA) has been well-studied and is known to be solvable in polynomial time (Lawler et al. in IEEE Trans Comput 18(1):47–57, 1969; Rajaraman and Wong, in: 30th ACM/IEEE design automation conference, pp 309–314, 1993). However, unbounded logic replication can be quite expensive. It follows that CN is an important problem. We show that selected variants of CN are NP-hard. We also obtain approximability and inapproximability results for some of these problems. A preliminary version of this paper appears in Donovan et al. (in: 9th International conference on combinatorial optimization and applications, COCOA 2015, Proceedings, pp 334–347, 2015).

Automation system of communication satellite designing

The selection of efficient alternative design of communication satellite architecture is impossible without solving the problem of Computer-Aided Design. The authors have offered the structure and the functions of communication satellite and data relay satellite. The prospects for further development have been defined as well.

Assessment of CAD-CAM zirconia crowns designed with 2 different methods: A self-controlled clinical trial

Statement of problemIn computer-aided design and computer-aided manufacturing (CAD-CAM) dentistry, the correlation method is an efficient way to design complete crowns. However, the occlusal relationship and patient satisfaction with prostheses fabricated using this method remain unclear. PurposeThe purpose of this clinical trial was to compare the occlusion of monolithic zirconia crowns designed using the correlation and library methods. Material and methodsTwenty-three teeth of 21 participants received 2 monolithic zirconia crowns designed by using the correlation or the library method. Defective teeth were scanned using an intraoral scanner to obtain references and working casts from before and after the preparation. Before cementation, the occlusal relationship of both crowns and patient satisfaction were evaluated, and the occlusal adjustment time was recorded. ResultsThe correlation method resulted in less lateral occlusal interference of the crowns than the library method (P<.01). The occlusal adjustment times of the correlation and library conditions were 455.8 ±357.1 seconds and 575.3 ±488.0 seconds, respectively (P>.05). Relative occlusal force was significantly higher in the correlation than in the library condition and was related to before preparation relative occlusal force (r=0.706, P<.01). The visual analog score before occlusal adjustment was higher in the correlation than in the library condition (P<.05). The occlusal contacts, occlusal contact distributions, and number of occlusal contacts did not differ between conditions (P>.05). ConclusionsBetter eccentric occlusion and reduced lateral occlusal interference were obtained when the correlation method was used to design crowns. The correlation method yielded higher relative occlusal force, which helped to restore the original occlusal force.

Evolutionary Operators for Global Optimization Population-Based Algorithms. Experience of Systematization

There are a large number of examples of using the population-based algorithms (P-algorithms) to have a successful solution for complex practical tasks of global optimization, for instance, problems of computer-aided design, synthesis of complex chemical compounds, optimal control of dynamic systems, etc. P-algorithms are also successfully used in multi-criteria optimization, when a preliminary construction of some Pareto set (front) approximation is required. P-algorithms are numerous and very diverse – over 100 such algorithms are known, and new algorithms continue to appear. In this connection, the problem of systematizing expressive means of P-algorithms is of relevance. We consider one of the components of this problem that is the problem of classification of the search operators of P-algorithms.The paper formulates a global optimization problem and a general scheme of the P-algorithms to solve it. This multilevel classification of the main search operators of P-algorithms at the highest level of the hierarchy identifies the following operators: initialization of the population and the end of the search; coding of individuals; randomization; selection; crossing; population management; local search.These operators at the next hierarchical level are divided into deterministic and stochastic ones. Further, we distinguish static, dynamic program and dynamic adaptive operators. The following classification levels are "operator dependent", that is, generally speaking, different for each operator. We reveal the essence of these operators and give the use cases in various P-algorithms.Although the paper uses the names of operators such as selection, crossing, our orientation is not only to evolutionary algorithms. A description scheme of operators presented in this paper can be used to determine any population-based algorithms.The work development expects extending a set of operators presented, and, above all, using this set and a set of basic essences of population algorithms, the formalization of which was earlier proposed by the author, systematizing the most known algorithms of this class.