DACS is an interactive computer program for the IBM-PC that aids in the design and analysis of linear control systems. Written in compiled basic, DACS includes Root Locus, Bode plots, Nyquist diagrams, Nichols charts, system simulation, and calculates the system time response in closed-form. The state-space description is used in the simulation and time response segments while the system transfer function is used in the root locus and frequency response segments. Calculated data may be displayed in either graphical or tabular form. Graphics features of DACS include automatic-scaling, zooming, graph coordinates derived from cursor location, graphics screen dumps to disk or printer, and redisplaying of disk files. DACS is menu driven and the majority of input/output is accomplished through the function keys. All system models and data may be saved on and recalled from disk. Help screens, three levels of sound, color, and session archiving are also provided. DACS provides a wide variety of linear control system analysis tools for the engineering desktop. / Master of Science

The Control System Analysis and Design Package (CSADP) is a computer-aided design package for applying classical control system analysis and design tools to experimental frequency response measurements. CSADP allows the user to analyze and manipulate measured frequency response data, design control systems using these measurements, and determine the operational amplifier hardware required to implement the design. To perform these tasks, CSADP provides tools that allow the user to define problems using both frequency response data files and transfer function descriptions; generate Bode, Nyquist, and root-locus plots; and curve-fit frequency response data. The curve-fitting program uses novel data-scanning techniques for conditioning the data, and for predicting the model form and starting parameters. CSADP also allows the user to design compensators interactively using Bode and root-locus methods, and aids the user in selecting the required resistor and capacitor values needed for implementing the compensator using op-amp circuits. In addition, CSADP provides coefficients required to implement the compensator using selected digital algorithms. CSADP was used in the design of a velocity loop compensator for a precision diamond turning machine. Open loop frequency response data gathered from the machine was used as the basis for compensator design using Bode methods. The required compensator coefficients generated by the program were programmed into the servo for testing. Results showed that the closed loop response predicted by the program accurately matched the measured response. Estimates of natural frequencies provided by the model prediction program were within 5 percent of the actual values. Errors in estimates of the damping ratios for very lightly damped complex poles ranged from only 10 percent to 30 percent. CSADP is written in FORTRAN 77 and provides Tektronix (TEK) 4010/4014 compatible graphics output. / Master of Science

3-D Interactive CADAM allows for easier construction, modification, analysis, and display of 3-D geometry surfaces and wire-frames. This research forms a basis for preliminary aircraft geometric design using the CADAM system. The helicopter design program, HESCOMP, originally a batch mode program, was coupled with CADAM via the CADAM data base such that the analysis, design, and redesign of the helicopter geometry and interior equipment geometry can be accomplished interactively. HESCAD, a program which produces the helicopter preliminary design model and enables the interior equipment design process, is developed. It provides a capability to evolve rapidly and refine helicopter configurations generated automatically using output from HESCOMP or interior equipment design by graphically and numerically defining helicopter components through interactive, on line, computer graphic display devices. Helicopter 3-D wireframes are automatically produced for any HESCOMP helicopter geometry output. A method which directs CADAM to analyze the helicopter components and produce weights, centers of gravity, moments and products of inertia and to review the results of the analyses directly on the screen is provided. This research was sponsored by IBM Corporation Federal Systems Division under contract No. 417503-DE. This thesis describes and illustrates the HESCAD program. Detailed graphical results are also presented. / Master of Science / incomplete_metadata

In recent years, the use of computer-aided design (CAD) systems for conceptual aircraft design has greatly increased. As a result, new and better methods for creating surface models of aircraft geometry using dimensional parameters are needed. One such method, the Rule-Based Fuselage method, was suggested by Lockheed. The Rule-Based Fuselage method allows an aircraft designer to define complex aircraft fuselage geometry by specifying the fuselage profile and individual parametric cross-sections along the fuselage. This thesis describes the Rule-Based Fuselage method and discusses the implementation of the method in an interactive, object-oriented environment. Also included in this system is the Spine and Cross-Section method for creating arbitrarily shaped aircraft components. The design and implementation of both the Rule-Based Fuselage and Spine and Cross-Section methods are described. The integration of these methods with the conceptual aircraft design code, ACSYNT, is also discussed. / Master of Science

The purposes of this study were to assess student attitudes toward CAD technology and use, to determine the efficient use of computer-aided design (CAD) systems in the design curriculum, and to investigate the current use of CAD at other colleges and universities in the United States with apparel design programs. A questionnaire was administered to students enrolled in a computer-aided design course to determine previous computer experience, previous design courses taken, and attitudes toward the use of computers. Another questionnaire that focused on the student’s attitudes toward the two CAD systems used in the class was administered after completion of the final assignment. The students in the apparel design course had positive attitudes toward computers and the usage of CAD as a tool for design applications. The students preferred to use the Lectra system and felt that it was the most efficient CAD system to use for assignments in the apparel design course. However, further study needs to be conducted concerning the efficient use of CAD in apparel design courses. A questionnaire was mailed to faculty at universities with apparel design programs to determine how CAD was being used in the curriculum, the type(s) of CAD system(s) being used, and the future plans for CAD in the curriculum. Frequency and percentage distributions were used to analyze the data. The data collected from educators teaching CAD at other colleges and universities in the United States indicate that CAD is being used in the classroom to teach flat pattern techniques (18%), pattern grading (16%), and marker making (16%). Thirty-three apparel design programs were using IBM computers to teach CAD with 14 programs using MicroDesign equipment to teach CAD. The programs that were using IBM computers or compatibles were using AutoCAD software (39%). The results also showed a significant increase in the number of programs with CAD in the curriculum from 21 between 1982 and 1989 to 38 between 1990 and 1993. This indicated that apparel design programs realized the importance of integrating CAD into the design curriculum to better prepare students for employment in the apparel industry. / Master of Science

A general review of lattice dome geometry and connection details, leads to a modeling approach, which introduces intermediate elements to represent connections. The method provides improved modeling of joint behavior and flexibility for comparative studies. The discussion of lattice domes is further specialized for parallel lamella geometry. A procedure is developed for minimizing the number of different member lengths. This procedure is incorporated into a program, which generates the geometric data for a specified dome. The model is developed from a background which considers commercial space frame systems, static and dynamic loads, and modeling techniques using ABAQUS, a finite element program. An optional output of the generation program creates input data for ABAQUS. Modal analysis, static design loads, and earthquake loads are used in the evaluation of the model. / Master of Science

The purpose of this thesis is to provide a complete package for the design and three dimensional modeling display of cams. The software produced as a part of this work will operate as a module of CADAM to produce cam designs and enter the resulting cam as a CAD model and produce the graphical display of the cam. In addition to the introductory material, this thesis is divided into four sections. The section on the graphics packages used in this thesis includes a brief history and capabilities of each of the packages. The second section details the procedure to be adopted in order to design a cam. The next section details ANICAM, the program that has been developed to incorporate the design and display procedure. The fourth section of this thesis contains recommendations for further work in this area. The theoretical work in this project is a combination of original derivations and applications of the theory in the design literature. / Master of Science

Engineering design is hierarchical in nature, and if no attempt is made to benefit from this hierarchical nature, design optimization can be very expensive. There are two alternatives to taking advantage of the hierarchical nature of structural design problems. Multi-level optimization techniques incorporate the hierarchy at the formulation stage, and result in the coordinated optimization of a hierarchy of subsystems. The use of multi-level optimization techniques often necessitates the use of equality constraints. These constraints can sometimes cause numerical difficulties during optimization. Single-level decomposition techniques take advantage of the hierarchical nature to reduce the optimization cost. In this research the decomposition approach has been followed to reduce the computational effort in a single-level design space. A decoupling technique has been developed that retains the advantages of a partitioned system of smaller independent subsystems without an increase in the total number of design variables. A penalty function formulation using Newton's method for the solution of a sequence of unconstrained minimizations was employed. The optimization of the decoupled system is cheaper due to (i) cheaper evaluation of the hessian matrix by taking advantage of its sparsity, (ii) fewer global analyses for constraint derivative calculations, and (iii) utilizing the decoupled nature of the hessian matrix in the solution process. Further, the memory requirements of the decoupled system are much less than that of the original coupled system. These benefits increase substantially for design problems with larger and larger number of detailed design variables. Orthotropic material properties as stiffness global variables have been shown to be effective as global variables for panels in a hierarchical wing design formulation. The proposed decoupling technique was implemented to minimize the volume of a portal frame and a wing box. Computational savings of up to 50 percent have been obtained for medium sized problems. The savings increase as the size of the problem and the amount of decoupling is increased. The procedure is simple to implement. For truly large systems this decoupling technique provides the necessary reduction of computational effort to make the optimization process viable. / Ph. D.

The effect of structural optimization on control of stiffened laminated composite structures is considered. The structural optimization considered here, is the maximization of structural frequencies of the structure subject to maximum weight and frequency separation constraints and an upper bound on weight. The number of plies with a given orientation and the stiffener areas form the two sets of design variables. As the number of plies is restricted to integer values, the optimization problem considered belongs to the class of nonlinear mixed integer problems (NMIP). Several efficiency measures are proposed to reduce the computational cost for solution of the optimization problem. Savings in computer time due to each of the measures is discussed. The control problem is solved using the independent modal space control technique. This technique greatly simplifies the evaluation of the sensitivity of the performance index with respect to the individual frequencies. The effect of different optimization schemes on the control performance is considered. To reduce the probability, that conclusions drawn from numerical results, are purely coincidental, a large number of cases has been studied. It has been concluded that sufficient improvement in control performance can be achieved through structural optimization. / Ph. D.

Thesis (MScEng)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: This thesis describes a module that links AutoCAD and CeDeas (cost estimation software which was developed by Department of Mechanical Engineering, University of Stellenbosch). CeDeas is intended for estimating the direct manufacturing cost of simple welded assemblies in a batch production environment. It is aimed at use during late concept design or early detail design. The link module was developed in Borland C++ Builder. By using COM (Component Object Model) technology, the link module employs the methods and the properties of the AutoCAD automation interface to extract manufacturing information that is required by CeDeas. The link module prompts the user to pick objects in an AutoCAD drawing and then determines the values required by CeDeas to estimate the manufacturing cost. The user can choose between a "direct select method" (which uses the properties of geometric entities already in the drawing) and a "user define method" (whereby the user defmes temporary entities or combines aspects of existing entities in the AutoCAD drawing). With these results and some non-geometric inputs, the user can get a cost estimate of components and assemblies. After design changes, the link module can provide CeDeas with updated values with minimal user interaction in situations where the "direct select method" was used. The designer can therefore easily use the cost estimates to compare design alternatives to optimise the design. Validation studies demonstrated the numerical accuracy of the use of the link module. The link module can be regarded as an extension of CeDeas. At present it only supports AutoCAD R14, but can be extended to support AutoCAD 2000 and Mechanical Desktop. / AFRIKAANSE OPSOMMING: 'n Module wat dien as skakel tussen AutoCAD and CeDeas (kosteberamingsagteware ontwikkel deur die Departement van Meganiese Ingenieurswese, Universiteit van Stellenbosch) word in hierdie tesis beskryf. Die doel van CeDeas is om die direkte vervaardiginskoste van eenvoudige, gesweisde samestellings, in 'n lot-produksie omgewing, te beraam. Dit is gemik op gebruik tydens laat konsepontwerp en vroeë detailontwerp. Die skakelmodule is ontwikkel in Borland C++ Builder. Deur van COM (Component Object Model) tegnologie gebruik te maak, kry die skakelmodule toegang tot die funksies en eienskappe van AutoCAD se outomatisasie koppelvlak en kan sodoende die vervaardigingsinligting onttrek wat deur CeDeas benodig word. Die skakelmodule vra die gebruiker om voorwerpe in 'n AutoCAD tekening te kies en bepaal dan die waardes wat deur CeDeas benodig word om die vervaardigingskoste te skat. Die gebruiker kan kies tussen 'n "direkte keuse metode" (wat die eienskappe van geometriese entiteite wat reeds in die tekening is, gebruik) en 'n "gebruiker definieer metode" (waarin die gebruiker tydelike entiteite defmieer of kombinasies van aspekte van bestaande entiteite in die AutoCAD tekening gebruik). 'n Koste beraming van komponente of samestellings kan verkry word met hierdie inligting tesame met ander nie-geometriese inligting. Na ontwerpsveranderings, kan die skakelmodule hersiene waardes vir CeDeas voorsien met minimale gebruikers-interaksie in gevalle waar die "direkte keuse metode" gebruik is. Die gebruiker kan daarom maklik die kosteskattings gebruik om ontwerpsaltematiewe te vergelyk om die ontwerp te optimeer. Evalueringstudies het die numeriese akkuraatheid van die skakelmodule bevesting. Hierdie module kan as 'n uitbreiding van CeDeas beskou word. Tans werk die module slegs met AutoCAD R14, maar dit kan uitgebrei word om met AutoCAD 2000 en Mechanical Desktop te werk.