Dissertationen zum Thema „Computer-aided design“

This thesis presents research into the possibility of developing a computerised system that can evaluate the aesthetics and engineering aspects of solid shapes. One of the research areas is also to include such an evaluation system into an existing evolutionary CAD system which utilizes the Genetic Algorithms (GAs) technology. An extensive literature survey has been carried out to better understand and clarify the vagueness and subjectivity of the concept of aesthetics, which leads to the work of defining and quantifying a set of aesthetic parameters. This research achieves its novelty in aiming to assist designers in evaluating the aesthetics and functional aspects of designs early in the conceptual design stage, and its inclusion into an evolutionary CAD system. The field of Computer Aided Design (CAD) lacks the aesthetics aspect of the design, which is very crucial in evaluating designs especially considering the trend towards virtual prototypes replacing physical prototypes. This research has managed to suggest, define and quantify a set of aesthetic and functional elements or parameters, which will be the basis of solid shape evaluation. This achievement will help designers in determining the fulfilment of design targets, where the designers will have a full control to determine the priority of each evaluation element in the developed system. In achieving this, computer software including a programming language package and CAD software are involved, which eventually led to the development of a prototype system called Computer Aided Aesthetics and Functions Evaluation (CAAFE). An evolutionary CAD system called Evolutionary Form Design (EFD), which utilizes GAs, has been available for few years now. It evolves shapes for quick and creative suggestions, however it lacks the automated evaluation and aesthetics aspects of the design. This research has worked into the integrating of CAAFE into EFD, which led to a system that could evolve objects based on a selected and weighed aesthetic and functional elements. Finally, surveys from users have also been presented in this thesis to offer improvement to the scoring system within the CAAFE system.

Ferrets are amusing, flexible creatures that have been under represented in computer models. Because their bodies can assume almost any curved shape, splines are the natural tool for modelling ferrets. Surface pasting is a hierarchical method of modelling with spline surfaces, where features are added onto a base surface. Existing surface pasting techniques are limited to modelling rectilinear shapes. Using the task of modelling a ferret as a driving force, I propose a method of pasting cylinders in world space; I looked at methods for reducing distortion of pasted features; and I created a method for pasting trimmed features to allow for features that do not have the rectilinear shape of standard pasting. With my methods, modelling ferrets with surface pasting is easier, and the resulting models are closer to a real ferret.

Hepatitis C virus (HCV) chronic infection represents one of the major and still unresolved health problems. HCV infecting 3% of the world population, leading to chronic hepatitis, liver cirrhosis and hepatocellular carcinoma in addition to the extrahepatic manifestations. No efficient therapy exists; the standard dual treatment with peg IFN-alpha and ribavirin is effective only in 55% of the selected cases with substantial side effects in addition to the high cost. To date, there is no vaccine against HCV due to the high variability of the RNA genome. NS3 helicase is one of the non-structural proteins whose activity is indispensable for viral RNA replication and its inhibition is estimated to arrest viral proliferation and indirectly stimulate a cellular antiviral response against ds RNA. In our project we proposed to use structure based knowledge of the x-ray crystal structure of helicase enzyme to design and synthesise different scaffolds of novel potential HCV NS3 helicase inhibitors. Using different computer software packages, we manage to design a number of small focused libraries of compounds, which were used for docking simulations. The results obtained in silico guided the selection of two series of promising compounds for synthesis. In the first series; several quinazoline derivatives were prepared and evaluated for antiviral activity in subgenomic replicon assay showing EC50 in the low muM range with relatively high selectivity index. In the second series of pyrrole or phenyl based compounds, irreversible inhibition of helicase is assumed through addition to the electrophilic warheads of the alpha,beta-unsaturated ketones, thiols or 1,2,4 thiadiazoles based inhibitors. Among the synthesised compounds a number showed a sub muM activity in the helicase enzyme assay. These promising findings are considered to be a starting point for further optimisation of structure, activity and toxicity relationships.

Today's competitive market requires engineers to produce reliable light weight products at low cost. This can be achieved by more effective use of computer aided engineering tools during early stages of the design process. A research programme has been undertaken to investigate the data requirements of integrating commercially available software packages (finite element analysis and fatigue life evaluation) to evaluate the integrity and durability of engineering components at the conceptual design stage. A real engineering component, in the form of a steering arm, supplied by a European truck manufacturer was used as a basis for the investigation. This is a typical vehicle component, in which, under service loading conditions, a multiaxial state of stress occurs. A geometric model of the component was created using the Prime "MEDUSA" software suite. The model was used to locate the boundary co-ordinates necessary for the development of a PAFEC Finite Element model. By imposing the conditions experienced during the service, the critical areas of the component were identified by analysing the F.E. model and a detailed description of the elastic stress/strain fields were also established. These were incorporated in an energy density approach and Neuber's uniaxial analysis to predict total local elastic/plastic strains at these critical- locations. These were compared with strain gauge measurements. The calculated results were used to plot a number of load/local strain calibration curves for the development of a load history, suitable for experimental fatigue life assessment. Fatigue crack initiation tests were performed on the steering arm using a computer controlled DARTEC multiaxial fatigue testing machine. Fatigue life assessment based on full service loading was carried out using a software package based on the critical location approach. A comparison of computerised, experimental and actual test circuit fatigue lives has been made. The work enabled a specification to be produced for the integration of the two items of software. This integrated software was developed by third parties and used to produce a computerised life map of the steering arm.

Cold roll forming is an extremely important but little studied sheet metal forming process. In this thesis, the process of cold roll forming is introduced and it is seen that form roll design is central to the cold roll forming process. The conventional design and manufacture of form rolls is discussed and it is observed that surrounding the design process are a number of activities which although peripheral are time consuming and a possible source of error. A CAD/CAM system is described which alleviates many of the problems traditional to form roll design. New techniques for the calculation of strip length and controlling the means of forming bends are detailed. The CAD/CAM system's advantages and limitations are discussed and, whilst the system has numerous significant advantages, its principal limitation can be said to be the need to manufacture form rolls and test them on a mill before a design can be stated satisfactory. A survey of the previous theoretical and experimental analysis of cold roll forming is presented and is found to be limited. By considering the previous work, a method of numerical analysis of the cold roll forming process is proposed based on a minimum energy approach. Parallel to the numerical analysis, a comprehensive range of software has been developed to enhance the designer's visualisation of the effects of his form roll design. A complementary approach to the analysis of form roll design is the generation of form roll design, a method for the partial generation of designs is described. It is suggested that the two approaches should continue in parallel and that the limitation of each approach is knowledge of the cold roll forming process. Hence, an initial experimental investigation of the rolling of channel sections is described. Finally, areas of potential future work are discussed.

Thesis (M.S.)--Worcester Polytechnic Institute.
Keywords: Fixture stiffness matrix; Jacobian matrix; kinetic model; geometric model; fixture design verification; stability analysis; tolerance analysis; tolerance assignment. Includes bibliographical references (p. 92-97).

The thesis describes the development of a computer-aided design and computer-aided draughting package of industrial gearboxes for transmitting power between shafts having parallel major axes. The package mainly consists of the following functions: (a) Determination of gear tooth numbers from the properties of continued and conjugate fractions (b) Generation of gear teeth by a rack-type cutter (c) Calculation of gear tooth profile and production of gear tooth grid for finite element stress analysis (d) Detailed strength analysis and design of a spur or helical, external or internal, standard or modified, single- or double- reduction gear set based on the ISO gear standards (e) Shaft design and analysis (f) Bearing selection and analysis (g) Production of the working drawings of the main gearbox components. This package works on the IBM PC and its compatible machines, operates in an interactive mode, combines the experience of the designer with the power of the computer, and produces substantial savings in time and cost over conventional design methods. Design examples illustrating this package are given. In addition, the maximum tooth root bending stresses have been studied by using finite element techniques and the results have been compared with those using the ISO gear standards.

In-silico methods used to aid the development of therapeutic drugs have gained utility in the recent past and continue to grow in importance. Small molecule drugs for the use in the treatment of type 2 diabetes were designed using computational methods to probe the active site of Dipeptidyl Peptidase IV (DPP-IV) and were subsequently synthesized and tested in-vitro. A number of pseudodipeptides formed from derivatives of tryptophan and proline were synthesized. The effects of a tetrazole group on the pyrrolidine of proline were studied, as well as the effect of protecting groups on the activity on DPP-IV. Exploring the effects of rigidifying the active dipeptides was next explored by attempting to synthesize the analogous bicyclic structures.
In order to add to the knowledge in the realm of computation tools used for drug discovery, eight docking programs were used to screen a subset of a small molecule database, the Database of Useful Decoys (DUD). This study focused on the effects of protein flexibility, crystallographic waters and program/protein dependence on active compound identification accuracy. This knowledge gained on the efficacy of current docking programs in VS campaign on real world therapeutic targets will allow for more efficient drug design in the search for new therapeutic agents.
Les méthodes in-silico, utilisées pour faciliter le développement de composés thérapeutiques, ont dernièrement vu leur utilité croître en considérablement. Au cours de ce travail, une série de petites molécules visant le traitement du diabète de type 2 a été conçue en se servant de méthodes informatiques pour sonder le site actif de Dipeptidyl Peptidase IV (DPP-IV) et a, par la suite, été synthétisée et testée in-vitro.
Tout d'abord, de nombreux pseudo-dipeptides construits à partir de dérivés de tryptophane et proline ont été préparés. Les effets sur l'activité biologique d'un groupe tétrazole sur le groupe pyrrolidine de la proline ont été étudiés, ainsi que l'effet de la protection des groupes fonctionnels. L'étude de l'impact de la rigidification de ces dipeptides actives a ensuite été envisagée et une synthèse de structures bi-cycliques debutée.
Dans le but d'accroitre les connaissances sur les outils informatiques servant pour la découverte de médicaments, huit programmes d'amarrage ont été évalués sur une banque de données d'une petites molécules, "Database of Useful Decoys" (DUD). Nous nous sommes plus particulièrement intéressés à l'impact de la flexibilité des protéines, de l'eau cristallographique et du type de programme utilisé sur la fiabilité des résultats. Les données collectées au cours de cette étude va nous permettre de développer des programmes plus efficaces et par la suite permettre une meilleure fiabilité de ces programmes dans les campagnes de criblage virtuel futures qui auront pour but de trouver de nouveaux agents thérapeutiques.

This thesis consists of three parts. Part I (chapters 1-4) gives a review and description of the basis for the numerical modelling of tension structures. The discussion in Part I leads to the conclusion of a need for an interactive design procedure for tension structures which is the subject under consideration in Part II (chapters 5-7). In the design of tension structures, an area which requires special attention is the dynamic response often initiated by the action of a natural wind. In Part III (chapters 8 and 9), this area is examined in detail and a strategy is proposed to give an improved modelling of dynamic response. The numerical procedure developed is assessed by comparison with previously reported test results for a pneumatic dome. Chapter 1 gives a general introduction to tension structures, and their main characteristics and behaviour are briefly described. From both the structural and architectural points of view, tension structures (classified as either prestressed cable nets or doubly curved membranes) do offer a number of benefits which arise from their characteristics and behaviour. The different types of cable nets which can be contructed are outlined, and various possible types of membrane structures and membrane materials which can be used are described. In addition, the form-finding and load analysis stages in the design process of tension structures are briefly discussed. An overview of Parts I, II and III of this thesis is also included. As a result of the flexible nature of a tension structure, large deformations often occur under loads acting normal to the surface. In addition, the coated woven fabrics exhibit material non-linearities, ie. the material properties vary under loads. In other words, a full non-linear structural analysis accounting for both material and geometric non-linearities is required in order to give a realistic modelling of the behaviour of a tension structure. Chapter 2 reviews numerical methods which have been widely reported for dealing with nonlinear structural analysis. From the review, it will be noted that the dynamic relaxation (DR) method is well suited to solving the highly non-linear problems which occur particularly in the case of tension structures. The dynamic relaxation method with a finite element idealisation of the structure is chosen as the solution scheme for all the analysis work in this thesis, and a detailed description of the method is given in chapter 3. Features of the method which are particularly useful for the design of tension structures are: (a) the effective decoupling of the equations of compatibility and equilibrium which allows complex material properties modelling and the use of slip cables, etc., and (b) the use of a 'kinetic' damping procedure which permits gross changes in support geometries to be made during interactive form-finding without the possibility of numerical instability. Although the main surface spanning elements may be purely tensile, many tension structures will employ compression and bending elements for their support. For example, as a means of providing support to a large span tension structure, a compression boundary is considered to be an efficient alternative to tension anchorages. In a sense, a compression boundary is complimentary to the tension elements in the structure as these elements also act as supports to the compression boundary. This gives the advantage of a compression boundary comprising of slender sections. The compression boundary is modelled as a series of beam elements. The moment-curvature equations of a beam element expressed in the form of natural stiffness relations, are developed in chapter 4. In addition, the non-linearities, both geometric and material, and boundary conditions which can be dealt with by the beam elements are considered. An outline is given of the implementation of the beam elements using the dynamic relaxation method. Included in chapter 4 are also the results to test problems which have been set up in order to validate the underlying theory and implementation of the beam elements. As tension structures often exhibit complex surface curvatures, a study of surfaces, their properties and behaviour is appropriate, and useful in the understanding of concepts applied in the design process. This study is the subject of chapter 5 which focusses on the relevant topics of differential geometry. A few useful ideas from differential geometry form the basis of certain procedures implemented into the form-finding and patterning stages being considered in chapter 6. The derivation of the equilibrium equations for a surface when acted on by applied loads is also given in chapter 5. The discussion in chapter 6 is about the stages of form-finding and static load analysis in the design process. A review of the available solution methods for the form-finding problem are given in this chapter. In these methods, the solution can be for either the unknown geometry or unknown stresses, or both. The adopted approach in this thesis is to solve for the unknown equilibrium geometry given the stress distributions, and initial and boundary conditions. The controls which can be used during form-finding to achieve the desired geometries of cable nets and membrane structures are discussed. The equilibrium geometry derived from the form-finding stage has to be subsequently evaluated for its performance under loads at the load analysis stage. After an equilibrium geometry which behaves satisfactorily under loads has been achieved, the corresponding cutting patterns are developed in the case of membrane structures. Recent advances in interactive computer graphics technology have made it possible to develop a fully interactive CAD system for tension structures. The development of such a CAD system is the subject of discussion in chapter 7. The CAD system integrates together the form-finding, load analysis and fabrication patterning stages, resulting in a continuous design process. It demonstrates how the various concepts discussed in Part I of this thesis fit together within an interactive environment implemented with an effective and functional user interface. It is illustrated in chapter 7 how such a user interface has been achieved. The CAD system fully exploits the capabilities offered by the available computer hardware such that the computations involved during analysis of the structure, in generation of surface shaded graphic images and so on, can be executed at very high speeds. As a result, the CAD system can respond quickly to the user and is thus consistent with the interactive nature of the design process. The discussion in chapter 7 also provides an insight into the various procedures involved throughout the design process. The CAD system has produced a number of benefits of which the main one is the saving in design time which has been achieved. As the CAD system is highly user friendly, only a short learning period is required, thus enabling it to be used more widely among designers. The CAD system also serves as a useful tool for the communication of ideas between the engineer and the architect. In the design of a tension structure unlike that of a conventional building, there is often close cooperation between the engineer and the architect right from the early stages of conceptual development. In chapter 8, the possible loads which may act on a tension structure during its service life are considered. These loads are applied to the structure at the load analysis stage in the design process. In most cases, the design loads are those due to snow and wind. An accurate assessment of the loads is essential in order to achieve a structurally sound and economic design. In addition, it should be possible to represent the loads in a form which can be easily applied in the structural analysis. The considerations which are involved in the assessments of the snow and wind loads are outlined.

The work presented in this thesis examines mode conversion characteristics of corrugated horns. The outcome of this investigation is the ability to produce optimum designs for corrugated horns. Analysis of propagation characteristics of corrugated conical horns is extended to the throat region where the complex representation of eigenvalues must be used to obtain an accurate field representation. A modal matching technique to the several is described using spherical modes and applied investigation of the scattering properties of types of discontinuities which may occur in corrugated horns. Computer modelling of a corrugated horn is described using the modal matching technique. The corrugated horn is divided up into a number of conical horn sections, each section propagating spherical modes. The propagating characteristics of each section are computed and modal matching is used to predict the scattering matrix for each junction between sections. The scattering matrices are then cascaded so that the complete horn can be modelled on the computer and an optimised design performed. Radiation properties of corrugated horns are studied by taking the influence of mode conversion in the horn into account. Comprehensive theoretical investigation into return loss performance, mode conversion characteristics and radiation properties of corrugated horns are described and substantiated by the experimental results . A phase cancellation method is presented, which can be used to design a profiled corrugated horn with low return loss and low higher order modes presented at the aperture.

This Thesis addresses Factory Layout Problems, and reviews and evaluates the available layout techniques. Manufacturing as a system has been studied and reclassified for factory layout: space demands and spatial relationships have been considered as main principles of Factory Layout Planning. This forms a basis for the introduction of a new, more efficient Factory Layout Planning Methodology, denoted as SPACE MANAGEMENT. A new COMPUTER AIDED FACTORY LAYOUT PLANNING system is formulated as a tool for: - preparing 3-D templates of Work Station Modules and Equipment Modules; - drawing a requested interior of an industrial hall/bay in 3-D; - positioning any 'objects1 (spaces), via manual interactive programs i n 3-D; - automatic positioning of work stations and equipment in the bay, in 'technological' order (in 3-D), using an automatic positioning program, with a facility for: collision course finding(with objects within the bay), manual override for corrections, and finding an optimum size (width) of the bay. The resulting layout scene can be observed from any required Position and distance. The system includes a set of auxiliary programs for Manual Feeding of lines of work stations in 'technological' order and for basic capacity calculations. CAFLAP also opens a new way of economic evaluation of Projects and alternatives. CAFLAP is implemented in FORTRAN 77 and uses the Computer Graphics System PICASO.

For the past three decades DNA has been exploited as building material for programmable self-assembly of diverse supramolecular architectures. Since 2006, DNA origami method offers a bottom-up route to fabricate nanometer-scale objects with molecular weights in megadalton regime. Small polyhedral containers of DNA could potentially be used to transport drugs or diagnostic chemicals to cells. In order to fold these objects to a high yield this project aims to develop a new design paradigm that uses DNA origami. The design process involves the calculations of an optimal path for a DNA-strand to take through the structure. Using Python scripting in Maya (3D software) it is possible to calculate the best topology for polyhedral DNA nanostructures. The important part of this project is the complex programming of scaffold routing. It is mostly a computer based project where it is required to write a python program that calculates an optimal path for a DNA strand to take through a 3D design. The design consists of two versions of the polyhedral containers which possess the shape of subdivided icosahedral .The final stage of the project is experimental phase, where self-assembling of these two structures, based on the principles of scaffolded DNA origami method was carried out.

The design and construction of fixtures is a major hindrance to the reconfigurability of flexible manufacturing systems. A promising method is to use a modular fixturing system. There remains, however, a considerable problem in the design of appropriate assemblies of such fixturing elements. This project describes a program for the automatic design of assemblies of modular fixturing elements. Its input is a description of the workpiece geometry, the machining envelope and the fixturing points. Its output is an automatically generated fixture design. The program incorporates systematic design procedure in conjunction with a large library of rules governing the movement and combination of the modular elements. A key feature of the system is the development of a suitable spatial representation technique, to describe those regions of space which are occupied by the workpiece itself, by the fixture and by the tools used to produce it. This spatial representation system permits the program to search and identify objects and object intersections. It is also able to determine the relative position of the modular elements during the design process. A design example was given to illustrate the method.

The twin screw refrigeration compressor is required to run over a large range of working conditions. In order to design an advanced and high-efficiency compressor economically, computer aided design techniques are required. This thesis presents such techniques, which include profile generation, geometrical characteristic calculation, working process simulation, rotor cutter blade calculation and optimisation techniques. All the basic theory and equations and the derived equations are presented. Four important computer programs, ie the profile generation program, the geometrical characteristics calculation program, the working process simulation program and the cutter blade calculation program, are developed and presented in the thesis. A few other support programs are also developed by the author to display the calculated results. All the programs developed form a program library for the CAD of twin screw compressors. All the programs except the profile generation program are universal, which means that they can be used for any shape of rotor profile. For the working process simulation program, only refrigeration twin screw compressors are considered, but it is easy to extend the use of the programs to other kinds of compressor. The thermodynamic effects of the following are discussed and taken into account: internal leakage of gas through all paths; oil, injected and drained from bearings; refrigerant injection, both gaseous and liquid; the flashing of injected refrigerant and that dissolved in oil; friction effects, in both end and main casings; the use of measured performance data in the determination of essential empirical coefficients in the mathematical model. The application of the programs and the design optimisation technique are presented, which include leakage analysis, compressor geometrical parameter optimisation, rotor-to-rotor clearance distribution optimisation and cutter blade shape optimisation etc. The author believes that the research work presented in this thesis is of practical value. Further, it presents new knowledge: of the compression start blow hole and its influence; of leakage quantitative analysis; of compressor design optimisation; of the quantitative analysis of the influence of different determination procedures of inter-rotor clearances.

Thrombosis is the most important pathological process underlying many cardiovascular diseases, which are responsible for high mortality worldwide. In this theses the computer-aided design of new anti-thrombotic agents able to inhibit two types of receptors located on the surface of the platelets has been applied. The first one - αIIbβ3 - is responsible for the interaction of activated platelets with fibrinogen to form clots, whereas the second one - thromboxane A2 - is responsible for platelet activation by one of agonists excreted by activated platelets. To achieve this, different types of models have been developed using experimentally available information and structure of protein-ligand complexes. This concerns: QSAR models, structure-based and ligand-based 3D pharmacophore models, 2D pharmacophore models, shape-based and molecular field-based models. The ensemble of the developed models were used in virtual screening. This study resulted in suggestion of new potential antagonists of αIIbβ3 and thromboxane A2 receptors. Suggested antagonists of αIIbβ3 able to bind either open or closed form of the receptor have been synthesized and tested experimentally. Experiments show that they display high activity; moreover some of theoretically designed compounds are more efficient than Tirofiban - the commercialized drug molecule. The recommended antagonists of thromboxane A2 receptor have been already synthesized but biological tests have not been completed yet.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.
Includes bibliographical references (leaves 63-66).
Microfluidic chips fabricated by multilayer soft lithography are emerging as "lab-on-a-chip" systems that can automate biological experiments. As we are able to build more complex microfluidic chips with thousands of components, it becomes possible to build devices which can be programmatically changed to solve multiple problems. However, the current design methodology does not scale. In this thesis, we introduce design automation techniques to multilayer soft lithography microfluidics. Our work focuses on automating the design of the control layer. We present a method to define an Instruction Set Architecture as a hierarchical composition of flows. From this specification, we automatically infer and generate the logic and signals to control the chip. To complete the design automation of the control layer, we suggest a routing algorithm to connect control channels to peripheral I/O ports. To the microfluidic community, we offer a free computer-aided design tool, Micado, which implements our ideas for automation in a practical plug-in to AutoCAD. We have evaluated our work on real chips and our tool has been used successfully by microfluidic designers.
by Nada Amin.
M.Eng.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004.
Vita.
Includes bibliographical references (p. 66).
Computer aided design has allowed many design decisions to be made before hardware is built through "virtual" prototypes: computer simulations of an engineering design. To produce robust systems noise factors must also be considered (robust design), and should they should be considered as early as possible to reduce the impact of late design changes. Robust design on the computer requires a method to analyze the effects of uncertainty. Unfortunately, the most commonly used computer uncertainty analysis technique (Monte Carlo Simulation) requires thousands more simulation runs than needed if noises are ignored. For complex simulations such as Computational Fluid Dynamics, such a drastic increase in the time required to evaluate an engineering design may be probative early in the design process. Several uncertainty analysis techniques have been developed to decrease the number of simulation runs required, but none have supplanted Monte Carlo. Gaussian Quadrature (GQ) is presented here as a new option with significant benefits for many types of engineering problems. Advantages of GQ include: as few as 2*(number of noise factors) simulation runs required to estimate performance mean and variance, errors dependent only on the ability to approximate performance using polynomials for each noise factor, and the ability to estimate gradients without further simulation rims for use in computer aided optimization of mean or variance. The mathematically basis for GQ is discussed along with case studies demonstrating its utility.
by Geoffrey Scott Reber.
S.M.

碩士
亞洲大學
電腦與通訊學系碩士班
97
Before the electronic accounting machine and the computer were invented, lens designer calculated the lens' third-order aberration and the multistage likely differential value without any technical instrument. It was really a laborious work. However, in the 21st century, it will be helpful to rely on computer to deal with the lens design formula. To simplify the computation procedure, the aberration formula will be programized with the aids of Matlab, Excel , and Zemax will be used to simulate the performance of the optical system. This research includes two important parts. Firstly,through the discussion of single lens, it shows the influence of shape factor on the aberration and the chromatic aberration. It is aimed to find the shape factor which will affect the Seidel aberration and the chromatic aberration. The second part, based on the above result ,we will discuss the eight degrees-of-freedom in three shape factors,the K value of three lenses and the two spaces of lens in Cooke triplet. Then, the Siedel aberration (spherical aberration, bright difference, astigmatic aberration, field tune, distortion), and the chromatic aberration (longitudinal chromatic aberration, lateral chromatic aberration) will be corrected to meet the specifications of the designed system. Therefore, the optimal three piece of lenses group can be obtained. In this paper, it shows the first order lenses structure can be got by fundamental image forming equations in chapter 4 which is often called the start point of lens design. In these days, it is easily to get this point from patents, lens demo, but it lacks the chance to know how it comes from. Beside, we also show the power of the computer lens design pakage that it gives the advanced design by optimization process. I hope this paper will give the idea how the computer helps to design a lens system.