Showing papers in "Computer-aided Design in 1982"
TL;DR: The basic approach to modifications of geometric models, a procedure for significant reduction of the number of constraint equations to be solved, and the effect of sparse matrix methods in reducing the time required to solve the equations are presented.
Abstract: Systems for computer-aided mechanical design use geometric models for drafting, analysis and programming of NC machines. Because design is iterative in nature, the topology, geometry or dimensioning of a geometric model must be modified many times during the design cycle. The effectiveness of future CAD systems will depend in large part upon the ease with which geometric models can be created and modified. This paper presents the results of a research effort to develop flexible procedures for the definition and modification of geometric models. A central idea of this effort is that dimensions, such as appear on a mechanical drawing, are a natural descriptorr of geometry and provide the most appropriate means for altering a geometric model. A procedure is described by which geometry is determined from a set of dimensions. The geometry corresponding to an altered dimension is found through the simultaneous solution of the set of constraint equations. Presented in this paper are the basic approach to modifications of geometric models, a procedure for significant reduction of the number of constraint equations to be solved, and the effect of sparse matrix methods in reducing the time required to solve the equations.
348 citations
TL;DR: In this article, generalized C 2 conditions are used to define a class of cubic splines, and a B spline-like design scheme is provided for these curves, which is based on a B-spline.
Abstract: Generalized C 2 conditions are used to define a class of cubic splines. A B spline-like design scheme is provide for these curves.
84 citations
TL;DR: In this article, the problem of tolerancing mechanical parts is reduced to the analysis of systems of linear inequalities, and a method is provided for the construction of a system of inequalities which the working dimensions and inaccuracies of machining operations must satisfy if a given tolerance specification is to be met.
Abstract: This paper discusses basic problems of tolerancing mechanical parts. The problem of part design analysis (determination of consistency, determinacy and stability) is reduced to the analysis of systems of linear inequalities. It is shown that the calculation of resulting tolerances between components of parts can be easily solved by linear programming. A method is provided for the construction of a system of inequalities which the working dimensions and inaccuracies of machining operations must satisfy if a given tolerance specification is to be met.
51 citations
TL;DR: In this paper, a numerical technique is described which allows spacing of points as a function of arc length for any parametric curve, and the design of a subroutine package for performing this parameterization is outlined.
Abstract: A numerical technique is described which allows spacing of points as a function of arc-length for any parametric curve. The design of a subroutine package for performing this parameterization is outlined. The technique has been incorporated into a CAD system and has been shown to be fast and accurate.
39 citations
TL;DR: Examples are given to demonstrate the effectiveness and the processing time of the program, which is part of the designer system for microelectronics (MICAD) elaborated at the Central Research Institute for Physics of the Hungarian Academy of Sciences.
Abstract: The polygons on the pattern generator used to produce masks for integrated circuits must be covered by the smallest possible number of rectangles. Two algorithms were elaborated to enable this task to be computerized. One of these algorithms is for general polygons, the other for orthogonal ones - the latter is quicker and more effective. Examples are given to demonstrate the effectiveness and the processing time of the program, which is part of the designer system for microelectronics (MICAD) elaborated at the Central Research Institute for Physics of the Hungarian Academy of Sciences.
36 citations
TL;DR: An algorithm is described that constructs the Bezier control vertices of cubic triangular polynomial patches from a grid of hexagons with a honeycomb structure.
Abstract: An algorithm is described that constructs the Bezier control vertices of cubic triangular polynomial patches from a grid of hexagons with a honeycomb structure.
33 citations
TL;DR: A new approach to the problem of smoothing digitized points is presented, where the smoothness of the input data is made visible by displaying the first and second differences.
Abstract: A new approach to the problem of smoothing digitized points is presented. The smoothness of the input data is made visible by displaying the first and second differences. Local corrections are performed on the first- and second-difference difference curves. The improved original data points are then computed by integration.
29 citations
TL;DR: In this article, the authors describe a recently developed interface between a bounded geometry modeller (ROMULUS) and an unbounded NC processor (APT) to provide a powerful manufacturing system for industry from the initial design right through part manufacture using NC machines.
Abstract: As systems for CAD and production of mechanical parts have developed, there has arisen a need for techniques for the comprehensive description of the desired part, including its 3D shape. It is desirable for links to be established between these geometric modellers and machining programs. Currently, unbounded APT and some bounded geometry systems are being widely used in manufacturing industry for machining operations such as: milling, drilling, boring and turning, applied mainly to engineering parts. APT systems, however, are presently only linked to wire-frame drafting systems. The combination of a geometric modeller and APT will provide a powerful manufacturing system for industry from the initial design right through part manufacture using NC machines. This paper describes a recently developed interface (ROMAPT) between a bounded geometry modeller (ROMULUS) and an unbounded NC processor (APT)
29 citations
TL;DR: This paper describes a technique for processing sketch input to a Boolean modeller that produces an efficient decomposition of the input profiles into half-spaces.
Abstract: This paper describes a technique for processing sketch input to a Boolean modeller. It allows the user to input one or more 2D profiles which may be interpreted as plates, plates with a draft angle, or (facetted) 'turned parts'. The method produces an efficient decomposition of the input profiles into half-spaces.
29 citations
TL;DR: Computer-aided architectural design is reviewed with particular reference to new software techniques that are becoming available, leading to a specification for the computing tools that may serve architects in the future.
Abstract: Computer-aided architectural design is reviewed with particular reference to new software techniques that are becoming available The needs of the designer are examined leading to a specification for the computing tools that may serve architects in the future The paper concludes by reporting on the results of early studies into one radically new technique: logic programming The research work referred to in this paper is sponsored by the Science and Engineering Research Council under grant numbers GR/A80341 and GR/A88774
25 citations
TL;DR: A generalization of the classical subdivision algorithm for Bezier curves that allows the direct construction of the control points of the curve is obtained.
Abstract: This paper looks at the classical subdivision algorithm for Bezier curves. This algoritm allows the direct construction of the control points of the curve. A generalization of this technique is obtained.
TL;DR: In this paper, a simplified three-dimensional computer input device is described as an aid to the potential use of computer aided design techniques by the lay public, which is demonstrated in an experiment which involves the builders of a self-build housing association scheme in the design of their own houses.
Abstract: The emphasis of most computer aided design is on the benefits to the user of the CAD system rather than on the possible benefits to the user of the resulting end products. This paper looks at some of the problems for any designer using a CAD system and in particular at the problems of involving the end user of a product directly in the design process.
A simplified three-dimensional computer input device is described as an aid to the potential use of computer aided design techniques by the lay public. The technique is demonstrated in an experiment which involves the builders of a self-build housing association scheme in the design of their own houses.
TL;DR: In this paper, the relative merits of numerical and wind tunnel models are discussed and various numerical techniques examined, and the relationship between wind flow round a building and heat loss from it is investigated.
Abstract: This paper looks at the relationship between wind flow round a building and heat loss from it. The relative merits of numerical and wind tunnel models are discussed and various numerical techniques examined.
TL;DR: In this article, the authors present a review of fifty programs simulating energy use in buildings and identify those which could offer the possibility of use as comprehensive models for the evaluation of passive solar designs.
Abstract: About fifty programs simulating energy use in buildings have been reviewed in order to identify those which could offer the possibility of use as comprehensive models for the evaluation of passive solar designs. The major attributes necessary are listed, and three models are identified as potentially the most suitable. An indication is provided of present deficiencies.
TL;DR: A system, currently being implemented, is presented that goes some way towards attacking the problem of modelling large assemblies by segmenting them spatially, designed to reduce to reasonable levels the cost of many common queries on databases containing large models.
Abstract: A problem with many solid modelling systems currently in existence is that their performance diminishes excessively with increasing model complexity. This has been the limiting factor on the complexity of model that can be evaluated and has hampered the modelling of large mechanical engineering assemblies. A system, currently being implemented, is presented that goes some way towards attacking the problem of modelling large assemblies by segmenting them spatially. This technique is designed to reduce to reasonable levels the cost of many common queries (including picture generation) on databases containing large models.
TL;DR: This paper looks at some of the problems for any designer using a CAD system and in particular at the problems of involving the end user of a product directly in the design process.
TL;DR: In this article, 23 computer program owners from 8 different countries collaborated in a joint R&D project to compare energy programs, both in terms of consistency between programs, and in considering the accuracy of these same programs in modelling the behaviour of a real building.
Abstract: Computer programs for predicting the energy consumption of a building are providing architects and building services engineers with very valuable aids to assist them in the design function. The calculation of building energy flows is extremely complex, and so validation is a vital element in the development of any model. Under the auspices of the International Energy Agency, 23 computer program owners from 8 different countries collaborated in a joint R&D project to compare energy programs, both in terms of consistency between programs, and in considering the accuracy of these same programs in modelling the behaviour of a real building. This paper summarizes the major conclusions that developed out of the project, and gives insight into some of the most important aspects which need to be considered in the development of a reliable computer program.
TL;DR: The Kelisky — Rivlin theorem for the Bernstein polynomials has been extended to the Bezier curves and some new identities of the BeZier functions are found which are potentially useful in CAGD.
Abstract: At the start of this paper, a recurrence formula for calculating the Bezier functions of any order is proved. Based on this formula, the Bezier functions are written in matrix form which enables us to develop the Bezier technique in a concise way. There are some new identities of the Bezier functions which are potentially useful in CAGD. Surprisingly a matrix involving the Bezier functions has been shown to be a doubly-stochastic matrix and the convergence behaviour of its powers is determined. Based upon these facts, the Kelisky — Rivlin theorem for the Bernstein polynomials has been extended to the Bezier curves.
TL;DR: In this paper, an interactive surface representation system is described which uses a parametric uniform bicubic B-spline formulation which can describe a surface initially defined to interpolate a specified network of points.
Abstract: An interactive surface representation system is described which uses a parametric uniform bicubic B-spline formulation which can describe a surface initially defined to interpolate a specified network of points.
TL;DR: An algorithm based on dynamic programming for the optimization of a series of manufacturing operations during multi-stage batch machining, finding the cycle time and process variables of each operation are optimum corresponding to which objective function is optimized.
Abstract: This paper presents an algorithm based on dynamic programming for the optimization of a series of manufacturing operations during multi-stage batch machining. The machine variables can be treated as discrete when necessary. The lower and upper limits of the overall cycle time are computed first. The interval between these limits is then divided into a sufficiently large number of parts to define a number of feasible cycle times. We then compute the optimum values of the process variables for each operation and the value of the chosen objective function corresponding to each of the cycle times. The cycle time and process variables of each operation are optimum corresponding to which objective function is optimized. The algorithm has been applied to a test problem. The results have been found to be directly usable and realistic.
TL;DR: The trials carried out within the Building Design Partnership of a dynamic energy model, ESP, developed by ABACUS at the University of Strathclyde are summarised.
Abstract: Implementation of computer software is concerned with trials of its robustness, relevance, and efficacy in the real-world, realtime context of design practice. This paper summarises the trials carried out within the Building Design Partnership of a dynamic energy model, ESP, developed by ABACUS at the University of Strathclyde. Over an 18 month period the program was used on 6 projects to address a variety of design problems over a variety of building types. The naper reports in outline on each of the six: four concerned with the need for a definite answer to a snecific question, eg. “will it overheat in summer” two concerned to provide, on the one hand for the client, on the other hand for the design practice, paradigms for energy conscious design of hospitals and offices. The conclusions drawn have relevance to the takeup of CAD generally.
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TL;DR: A new technique for the solution of CAD problems using PROLOG, in the form of the design of a multistorey living-house, which is illustrated on an architectural example.
Abstract: This paper presents a new technique for the solution of CAD problems. The technique is illustrated on an architectural example. The designing knowledge is represented in the form of axioms described in the language of mathematical logic. The calculi of logic which manipulate these axioms can be used to model designing processes. If Horn formulas are used the description of the technical problem can be considered as a program written in PROLOG. A new architectural application of PROLOG is introduced, in the form of the design of a multistorey living-house. The first program generates different versions of ground-plans according to the special needs of the customer. During the design of the house those versions are selected which meet the functional requirements, the dimensions and the environment data of the building.
TL;DR: The link between drawing systems and knowledge of users' work-practices is discussed and illustrated by examples of experience at EdCAAD, highlighting the significance of knowledge engineering to practical CAAD applications.
Abstract: The link between drawing systems and knowledge of users' work-practices is discussed and illustrated by examples of experience at EdCAAD, highlighting the significance of knowledge engineering to practical CAAD applications.
Drawing systems, design systems, user-interface, knowledge engineering.
TL;DR: The UK Science Research Council (UKSC) has set up a programme of funding for projects on the dynamic thermal performance of buildings as mentioned in this paper, which includes various models and techniques available, and a list of grants so far is presented.
Abstract: The UK Science Research Council has set up a programme of funding for projects on the dynamic thermal performance of buildings. This paper examines the programme in detail, looking at the various models and techniques available. A list of grants awarded so far is presented.
TL;DR: The structure strongly supports designer—database interaction by providing extremely versatile access mechanisms and an associated concurrrency control mechanism and it is demonstrated that the relational model provides a flexibility of access not readily available in other models.
Abstract: This paper proposes an implementation structure and the corresponding relational model for a building design database. The structure strongly supports designer—database interaction by providing extremely versatile access mechanisms and an associated concurrrency control mechanism. It is demonstrated that the relational model provides a flexibility of access not readily available in other models. The implementation structure supports designer access to database entities by location, attribute value, and combinations of both. It also supports ad hoc groupings of data. At the same time it maintains the integrity of the database against violations caused by concurrent use. Existing concurrency control methods are explored and a new level of locking for concurrency control is proposed. The module is recommended as the optimal level to which a locking mechanism be applied.
TL;DR: Part of the GABLE computer aided architectural design system developed at Sheffield University is described, which allows the user to input a building from a series of simply drawn floor plans in such a way that ISAAC is able automatically to develop a three dimensional model of the inside of each space.
Abstract: In this paper we shall describe part of the GABLE computer aided architectural design system developed at Sheffield University. This system, written in BASIC to run on Tektronix 4050 series desktop computers, is intended to be capable of being used even in the smallest design office without the need for specialist staff. In particular, we shall show how GABLE allows the user to input a building from a series of simply drawn floor plans in such a way that ISAAC is able automatically to develop a three dimensional model of the inside of each space. We shall show how this system is sufficiently general to accommodate buildings irregular both in plan and section without the need for any restricting planning grids.
TL;DR: A set of lower level geometry functions is presented and on these the authors build algorithms for geometry calculations on B-spline curves.
Abstract: B-splines are used as the standard storage format for all curve geometry in the sculptured surface module of the Inter-Nordic CAD/CAM project GPM. The geometry resulting from the calculations are stored in standard formats, while data structures take care of how the geometry was defined. A set of lower level geometry functions is presented. On these we build algorithms for geometry calculations on B-spline curves.
TL;DR: It is shown how a roof may be described to the GABLE computer aided architectural design system from a roughly drawn roof plan, together with pitches of roof planes and heights of points within the roof in whatever combination is most convenient for the user.
Abstract: This paper describes part of the GABLE computer aided architectural design system developed at Sheffield University. This system, written in BASIC to run on Tektronix 4050 series desktop computers, is intended to be capable of being used even in the smallest design office without the need for specialist staff. We will show how a roof may be described to the system from a roughly drawn roof plan, together with pitches of roof planes and heights of points within the roof in whatever combination is most convenient for the user. RODIN will check the consistency of the information which is given and use it to construct a geometrically correct three dimensional model of the roof. The system imposes no restriction on the type of roof which may be modelled.
TL;DR: In this paper, the requirements for validation of a model and the techniques which can be used for validation are discussed, as well as the type of data required for validation is examined.
Abstract: This paper looks at the requirements for validation of a model and at the techniques which can be used. The author reports on his own experience with instrumenting an office building in Glasgow, UK. The type of data required for validation is examined. Integration of building and systems modelling is discussed, and the requirements for this to occur in the future are examined.