Sun Jiachang is extracted from [Computer World News] ComputeRededDesign (CAD) is a technology that can assist, modify, analyze, and optimize design with computer systems. With the popularity of Internet / intranet network and parallel, high performance computing, transaction processing, different places, collaboration, virtual design and real-time simulation have also been widely used.
---- CAD as an important part of information technology, combining computer high-speed, massive data storage and processing and excavation capabilities and human integrated analysis and creative thinking ability, and shorten design and manufacturing cycles for accelerated engineering and product development Increase quality, reduce costs, and enhance corporate market competitiveness and innovation capabilities play an important role. Whether it is a military industry or a civilian industry, whether it is the construction industry or manufacturing and processing industry, whether it is mechanical, electronic, textile products, or cultural and scent, film and television advertising production is inseparable from CAD technology. CAD technology is an important technical foundation for enterprise informationization. It is also an admission ticket in the international market.
---- CAD, if the graphics system is disposed from the US MIT Cyclone I, it has been 50 years; if the charter system for human-computer communication published by Iesutherland in Mit Lincoln Laboratory Doctoral thesis begins, there are also 36 years of history. After nearly half a century, CAD technology has made great progress in theory, technology, system and application, and the computer aided design (CAD), process planning (CAPP), manufacturing (CAM), engineering analysis ( CAE) and the content of product data management (PDM) are simple review.
Computer Aided Design (CAD) ---- 1. User interface
---- The user uses the CAD system through the user interface, the early computer uses a character-type user interface (SUI), and in the 1970s, people began to study the graphical user interface (GUI). In 1984, the Macintosh developed by Apple made the GUI into a window system and became the mainstream of the PC. In the 1990s, with the wide application of the network, multimedia technology, network user interface (NUI) and multimedia user interface (MUI) have become the lead interface of CAD systems. The workstation CAD system basically uses Motif as its user interface.
----2. Graphic standard
---- In the early 1970s, in order to reduce the cost of CAD software, researchers put forward research and development and equipment-independent graphics software. In 1974, the issue of formulating graphic standards has been proposed in the Work Conference of ACMSiggraph, "NSI) held in the US National Standardization Bureau (ANSI), and proposed" core graphics system "in 1977 ( CGS) Standard text. Subsequently, ISO issued an international standard text such as computer graphics interface (CGI), computer graphographic file standard (CGM), computer graphics core system (GKS), programmer hierarchy interactive graphics system PHIGS. In terms of product data exchange, in the late 1970s, US CAM-I proposed initialization graphic standard IGES, product data definition interface PDDI, product data exchange specification PDES. In the 1990s, ISO approved the standard STEP as an international standard. The application of STEP played a positive role in the integration of CAD corresponding unit technology and system.
---- 3. Engineering drawing
---- Computer Auxiliary Drawing Engineering Drawings are the earliest and most successful areas of CAD applications. Since the mid-1970s, this technology has experienced the following stages:
---- Passive Drawing Computer Interpretation Performs a drawing instruction, output the corresponding drawing on the plotter; ---- interactive drawing user repeatedly modify the graph on the display screen with the interactive tool until satisfaction, finally successfully output the corresponding blueprint;
---- Parameterized drawing users do not have to enter graphical elements on the drawings (such as straight lines, arcs, characters, labels, etc.), but the parameters of the design component, automatically output the corresponding parts of the corresponding components by the CAD system;
---- Smart Drawing Based on the parameterized drawing, the corresponding rules and regulations of the engineering drawing are used in the Knowledge Rules. Under the guidance of the corresponding expert system, some professional engineering drawings or products can be automatically output. Design plan.
---- For enterprises in the enterprise, entering a computer, in the 1990s, many units at home and abroad conducted research and development of engineering drawings and automatic identification reconstruction techniques and systems, but due to identification and reconstruction theory. Breakthrough, the corresponding system is still in trial.
---- 4. Digital modeling
---- (1) wire frame, surface modeling
---- Digital Modeling is the use of a computer to represent the actual or imaginary body and the technique of the scene, which is the foundation and core of CAD, involving wireframe, surface, entity, and characteristic modeling. Since there is a computer processing geometry, there is still many problems that have not yet been resolved in a relatively ancient and complex field in CAD. From 1963 Franus, the curve surface indicates the form of parameter vector function, the wireframe, and the surface modeling experience have experienced the following development stage:
--- 1963 Franuson (Ferguson) represents the curve surface as a parameter vector function;
---- 1964 Coons defines a surface with the four borders of the closed curve;
---- 1971 Bezier published a method of defining curves and surfaces with control polygon;
---- 1972 Deboo deboo gave the standard calculation method of the B-spline;
---- 1974 Gordon and Riesenfeld use B spline theory for shape descriptions, proposes B-spline curves, surfaces;
---- 1975 Fosprill proposed a reason for b - spline method in his doctoral thesis;
---- 1980s, Piegl and Tiller developed the B-spline into a non-uniform A NURBS method, and became the most widely described in the current free curve and surface description. For popular technologies. Using NURBS can be unified to represent the primary parsing curves and surfaces and their unreasonable Bezier, non-reasonable B - spline curves and surfaces.
---- (2) Entity modeling
---- Since the wireframe and surface modeling cannot indicate the condition of the outbody inside, it cannot support the optimization design of the body. In the late 1960s, the United States and the United Kingdom have carried out the research and development of physical styling technology and systems. The University of Rochester has started PADL physical modeling system in 1972, and the PADL1 version and PADL2 version were launched in 1976 and 1982; Shapedata, England, also launched Romulus solid modeling systems in the 1970s. In the 1980s, there were more than a dozen of the international solid styling system, but it has also impacts: Pro / ENGINEER, CATIA, Ideas, Parasolid and Acis, where Parasolid and Acis are supported by the core, which has supported many end users. Develop a commercial version of the commercial version of the commercial version of different application purposes, such as SolidEdge, SolidWork, MDT, etc. Substrate-like forms commonly used include solid geometry (CSG) representation, boundary representation (BREP) and scanning representation, the most critical calculation, combined operation, collection operation, and Euler operation. ---- (3) Feature Modeling
---- Feature modeling is also called feature styling. The characteristic modeling is a product information model for establishing a body to support a whole process of designing and manufacturing a new modeling technology for CAD / CAM integration. The product information model of the body includes geometric topography information and non-geometric information such as process rules, tolerances, materials, manufacturing processes, and corresponding costs. Features is a description of a particular attribute of the product, which reflects a specific geometry and specific processing requirements for actual parts or components, providing higher-level design concepts and means for designers and other systems.
---- Characteristic styling technology is the rise in the end of the 1980s. The factors in the two have led to its appearance and application. On the one hand, traditional physical styling technology is based on geometric representation and operation, low-level, uninordful meaning geometric operation and designer's high-level design should result in contradictions; on the other hand, nearly 10 years, CIMS Technology has been greatly developed, which requires traditional styling systems to provide non-geometric information that reflects designers intent for other systems, including CAPP, CAM, etc. in addition to satisfying their own information, including CAPP, CAM, etc., such as tolerances, materials, etc.
---- In order to adapt to computer animation production, and directly reflect object motion and variation law, based on physical law, modeling technology and system have a long-term development in the past 10 years. It is used to represent the shape technology and system of irregularities such as hills, trees, grass, and clouds, such as fractional design, text-based modeling and particle systems, starting research since the 1980s, now achieved a practical level.
---- 5. parametric design
---- In the development of new products, about 70% to 80% of the cost is consumed in the design phase. Therefore, how to develop and study advanced design methods and tools to improve product design efficiency is critical. Artificial intelligence studies believe that design issues are constraints to meet questions (CSP), namely given features, structures, materials, and manufacturing, etc., seeking detail of design objects.
---- The key to parameterization design is the extraction and expression of geometric constraints, the solution of geometric constraints and the construction of parameterized geometric models. In the late 1970s, the University of R. C. Hillyard, the University of Cambridge, and the US MIT's D. C.Gossard, which took the first to design in CAD; 1985, US PTC first introduced parameterized CAD system Pro / ENGINEER in 1985 At present, two-dimensional parametric design technology has developed more mature and has been widely used in parameterized drawings. The problem of three-dimensional parameterized modeling can be handled is relatively simple, and the surface type that can be processed is mainly axis, flat and axis-symptoms, and the type of constraint can be handled is also limited.
---- In parameterization design, the expression of geometric constraints is mainly: equation or inequality relationship composed of arithmetic operators, logic comparison operators, and standard mathematical functions; curve relationship; relational files; face-oriented intelligence Knowledge expression. ---- 6. Graphic display
---- In order to realize the digital model of products and engineering generated by CAD technology, the true graphic display technology is also an important part of CAD, which mainly includes light illumination model, drawing algorithm, acceleration algorithm, etc.
---- Graphic display is a simple local light illumination model. The Lambert cosinence summary summarizes a diffuse reflective light illumination model under point light irradiation, and proposes a dark-dimensional interpolation model with a polygonal vertex light inclusion (1971) according to this model (1971), mirror Reflected Empirical Model and Phong Lighting Model under a single source (1973), partial light illumination model and overall light model (1981), improved the authenticity of the computer generated graphics.
---- True Justice Drawing Method The first is the first 1974 Zaffler hidden face elimination algorithm proposed by CATMull. Subsequently, a two-parameter polynomial drawing algorithm based on scan line is proposed, and the recursive light tracking algorithm and the corresponding overall light model are proposed. . In the mid-1970s, CATMULL first uses texture mapping technology to generate the texture details of the scene surface, which can be divided into two-dimensional texture and three-dimensional texture according to the texture definition domain; the texture-based manifestation, and can be divided into color texture, geometric texture and Process texture. In 1984, the American Cornell University's scholar introduced the radiation method in the hot radiation engineering into CAD, which produced a real graphic generated radiometer algorithm. In the mid-1980s, in order to adapt to the need to display the needs of the multi-dimensional data field, the research and application of scientific calculations in medical, finite element analysis and other areas. With the real-time display of three-dimensional realism, the development of multimedia technology, the immersible virtual reality or the museum environment also has significant progress and development in the 1990s, and promotes virtual design, virtual manufacturing and virtual enterprises. Working.
Computer Assistance Process Planning (CAPP) ---- Process Planning is a bridge that connects product design and product manufacturing, which has an important impact on product quality and manufacturing costs.
---- The world's earliest research CAPP is Norway, starting in 1966, and officially launched the world's first CAPP system AutoPros in 1969, which officially launched the commercial AutoPros system in 1973. The United States is the beginning of CAPP at the end of the 1960s, and in 1976, the United States launched an influential CAP-I'SAUTOMATEDPROCESSPLANNING system by Cam-i.
---- From the end of the 1960s, there were two types of systems in design in design methods, namely:
---- Derived system has become a system that has different degrees of modifications, editing and automatic screening, and combines partial creations and methods.
---- GENERATIVE system its research and development began in the mid-1970s, and quickly attaches general attention, is considered a promising approach, but practical results are not ideal.
---- In recent years, these two types of systems have been continuously improved, improved and penetrated, from the 1980s, and people explore the research and development of artificial intelligence (AI), expert system technology, etc. CAPP system, The development successfully implemented CAPP system or CAPP expert system based on knowledge-based (Knowledge-based). In recent years, some people have used artificial neuron network technology, fuzzy reasoning, and examples of reasoning, etc., and some people have proposed the idea of CAPP system construction tools and have a practical practice. Some people combine traditional derivatives and traditional creation methods with artificial intelligence, integrating their advantages, constructing a hybrid CAPP system. There are many examples of various types of systems at home and abroad, generally for a special CAPP system for a company, a type of part, but so far, there is not much practical production test and satisfactory commercialization system. my country's research on CAPP began in the early 1980s, and several systems were applied in the enterprise. Computer Aided Manufacturing (CAM) ---- The core technology in CAM is CNC technology. Usually the part structure uses the point, line, and the digital quantity of the surface in the spatial angle coordinate system, and the CAM is the digital control of the digital control tool movement with the CNC machine, complete the parts processing. NC machining main division programming and machining process two steps. The programming is based on the drawings or CAD information, according to the requirements of the CNC machine control system, determines processing instructions, completing the parts CNC programming; the processing process is to transmit the obtained CNC program to the CNC machine tool, control the servo system of each coordinate of the machine, drive the machine Make the tool and workpiece strictly follow the requirements of the executive program, and the parts that meet the requirements are processed. At the end of the 1940s, the United States began researching CNC machining technology, and the first CNC machine tool was produced in 1952. In 1957, the first number of control machine tools were put into use. In 1958, my country has developed a number of control machine tools with electronic tube CNC system, starting from 1965, three-coordinate number-controlling milling machines for producing transistor CNC systems. In the 1990s, there were tens of thousands of technologies at home and abroad, and PC-based three-coordinate to six-coordinate numerical machine tools were widely used in production.
Computer Aided Engineering Analysis (CAE) ---- CAE is mainly to achieve structural analysis and structural optimization. Although CAE's approach has a variety of methods, the most widely used, most mature is finite element analysis, but also known as limited elevation, the proposal of its basic ideas can be traced back to 1943, and Courarant first applying the division in the triangular area. Slice continuous function and minimum positional energy principle to solve St.venant torsional problems. The first successful attempt of modern limited cell law is in 1956, Turner, Clough et al., In the analysis of the aircraft structure, the steel frame movement is applied to the elastic mechanical plane problem, which gives a flat stress with a triangular unit. The correct answer of the problem. In 1960, Clough further handled a flat elastic issue and the first time I proposed "limited cell law" to make people realize its efficacy. After the 1960s, especially with the development and extensive application of the computer, finite element analysis in structural mechanics, elastic mechanics, fluid mechanics, thermodynamics, electromagnetic, aerospace, civil engineering, water conservancy, materials and other engineering design and engineering analysis areas. More becoming an indispensable effective calculation and analysis method.
---- The basic idea of limited cell method is to discret into a combination of a limited simple unit, simulate or approximate the original object with a collection of these units, thereby rejection of an continuous degree of freedom The problem is simplified to discrete limited freedom. After the object is discretized, the analysis structure of the entire object is finally obtained by unit analysis of each unit. As the number of units increases, the approximate degree of solution will be increasing. The finite element analysis process mainly includes three stages:
---- The previous processing phase first establishes a finite element model, completing the input of the data, and the model works for discrete vertex node data. Grid section is a key step in this phase. ---- The finite element analysis process finally analyzes the overall analysis of all units by unit analysis of each unit. This phase is mainly to obtain a calculated result by solving the linear equation.
---- The post-treatment phase uses a variety of ways to display the analysis results and evaluate. The process has an intuitive understanding of the analytical structure of data volume through intuitive, graphic, vector and dynamic display.
Product Data Management (PDM) ---- CAD technology is popular, so that the product design and manufacturing data information in the enterprise is low, the transmission speed is slow, the business management is backward, the design method is old, the support technology does not match and the application integrated system efficiency Not high contradictions are getting more and more prominent. In the early 1980s, manufacturers have developed a lot of self-use PDM systems to solve the above contradictions. By the late 1980s, many professional companies will evolve into PDM products. In the 1990s, some manufacturing companies in the United States began using PDM.
---- my country began research and development of PDM system in the mid-1990s, due to the experience of absorbing foreign PDM development, therefore, the starting point is high. Currently, the "863" program supports CORBA / Web-based PDM system and the international advanced PDM system in less than 5 years. PDM is integrated and managed technology-related information, procedures, and its own technology, its application is divided into four levels of corporate staging electronic management, departmental data management, enterprise data management, and inter-business data management. PDM implements the correct task in the right time, the correct information, the correct task, to the correct person, to the correct person, to the correct person, to the correct person, to the correct person, to the correct person, to the correct person, to the correct person, to the correct person, to the correct person, to complete the correct task Personnel collaboration, process optimization, and raising effort. As a management system, PDM needs to be customized and implemented for special needs of enterprises. To this end, the establishment of corporate models, the development of specifications is a key factor in accelerating PDM promotion applications.
---- In the past 30 years, the software development has passed four waves. In the 1970s, the batch was calculated on the world. In the 1980s, online processing calculation exclusive, in the 1990s, the customer / server-based processing mode prevails, the introduction of Internet, Java and distributed component technology The unstoppable potential quickly spreads into various fields, forming the fourth wave of software development. Under the fourth wave, the host terminal form, desktop calculation form, customer / server form, and network calculation form will coexist, combin, and develop together. Under the impact of the fourth wave, the development and application of different places, heterogeneous, synergies, virtual CAD technology will be more popular, more efficient.
