We introduce the new section "Business Information" where we will publish information about latest hard/soft-ware developments in computer graphics and geometry applications.
V. Pilyugin

Application of Information Technologies by CAD Systems Research Center in a Aerospace Industry

Y.V.Davydov,

CAD Systems Research Center, Moscow, Russia

E-mail: davydov@nicask.ru

In the beginning of the 80’s the understanding and necessity to create domestic CAD/CAM systems resulted in the creating of scientific teams. These teams had to develop software to find solution for these problems. The first team was organized in 1983 as a division of TsAGI named after N.Ye.Zhukovsky. In 1987 this division was transformed into an independent organization called CAD Systems Research Center (CAD SRC).

The first software developed by CAD SRC was the Basic Data Software of Computer Aided Design systems (BDS CADS) [1]. The software was developed and installed on more than 50 enterprises in defense industry. Analysis of traditional design process of complex machine engineering determined the specifications of this software.

Functionally in machine engineering, the whole process including defining specifications to building of a prototype comprises of the following steps:

This rather simplified scheme, does not take into account many processes (prototyping, model tests, test of units etc.), that happen in parallel and influence the final outcome.

For example, for an airframe design, the process begins at the stage of units placement. When the main assemblies of an aircraft are placed together, the overall volume emerge. The center-of-gravity of the airplane is determined and the layout of the basic load-bearing elements is formed [2]. Further stages are geometrical modeling, project accounts, design and documentation, preparation for manufacturing and production (Fig. 1).

Aircraft Figure Design

 
Preliminary Design

 

 
Outward Surface Geometry Design

 

 

 

 
Preliminary Design Calculations

 

 

 
Test and Handily in Exportation

 

 

 

 
Aircraft Exploitation

 
Fig.1.

In traditional techniques, theoretical drawings of external and internal cross sections of an airplane were the result of geometrical modeling and used as basic sources of the geometrical information. At the first stages of implementation of geometrical modeling systems, the use of mathematical models of surfaces reduced time and increased accuracy of manufacturing. But theoretical drawings didn’t allow excluding of plots and templates in connection with absence of interactive means of dialogue with geometrical model. Made in automatic mode by use of plotters, theoretical drawings served the basis for designer’s documentation.

For the first time in domestic practice BDS CADS allowed not only to introduce interactive process of geometrical modeling of external outlines and surfaces, but also to determine other problems which are invariant in relation to designed object. As invariant problems were chosen following [3]:

Pursuant to the delivered problems, BDS CADS includes the geometrical modeling system (GMS), the project data management (PDM) system, tools for development of Applied Program Packages Library (APPL), tools for expert systems development XTools and also set of interfaces to other CAD systems and applications (Fig.2).

Fig.2.

The basis of GMS is the specialized database storing exact mathematical descriptions of geometrical objects. The database provides storage, extraction and structuring of geometrical model elements, appropriation of names, numerical values and textual attributes of objects, samples of objects on given values of attributes, association of models, creation and use of typical geometrical bars and templates.

One can create 2-D and 3-D models from points, lines, arcs of circles, curves of the second order, splines, Bezier curves, line-ups of sections and arcs, polygons and polygonal lines, three-dimensional curves, planes, surfaces of revolutions, ruled and deploying surfaces, cinematic surfaces, Coons surfaces and their logic combinations. Such high-power means of geometrical modeling allow not only to describe external surfaces of flight vehicles completely (Fig. 3), but also to create their technological models by partitioning on compartments and aggregates (Fig. 4).

Fig. 3.

Fig. 4.
Project management system of PDM system is used to maintain accumulation, coordination and consumption of design information during designing. It is realized by computer facilities, integrated in a network. The realization PDM system allows to execute gradual transition to «paperless» technology of accumulation and consumption of design information, and also to ensure transfer of a design information on paper or computer carriers.

The database (DB) in the PDM system is the central component, in which information of the designer’s solutions and project’s versions are accumulated as sets of named objects of the project. Tools for accumulation of the versions and capability to search the reference information are supported within this system. The database in the PDM system can store the information about the several projects simultaneously.

For each project, the DB of the PDM system is divided into two levels: the authorized information and information located at the stage of development – information that can be updated. The authorized information represents the common region of a database for all designers of the project (central database of the project). The database is managed and controlled by the project manager. An individual designer controls updating of information.

PDM system grants the designer the following capabilities:

In addition to a name for each object, the storage of the textual description of the name / summary of object and following information should be provided:

 One of the major elements of the accompanying information is the table of the confirmation, in which the system names of the designers and/or their chiefs with the instruction for a level of the confirmation are listed. The concept is that "the Level of the confirmation" reflects sequence of automatic transfer of the information for confirmation to the higher person.

Introduction in the accompanying information of the lists of objects to which the particular version of object is connected, allows to define automatically the list of the designers for the notification after the statement of the version in a central database, and to determine connections between objects of the project.

In PDM system access, control to the central database permits to fix the certain objects of the project behind the particular users for entering data and to define the list of users who have rights to extract information or to execute other operations.

Some of the major functions of PDM SYSTEM include:

Figure. 5 shows the technology of accumulation, coordination and consumption of design information in the system of project management.

The system PARM is an example of development of an applied system based on BDS CADS for synthesis, designing and analysis of landing gears [4]. This system was created by CAD SRC together with Scientific Research Institute of Applied Mathematics and Cybernetics at Gorky State University named after Lobatchevsky. The users work in a system by an interactive mode, have broad capabilities of submission of initial information and results from calculations. The system executes the following functions:

 The graphic exchange of the data in the PARM system is executed with the help of GMS interface with a capability of transition from one system to another, not interrupting interactive process. Also PARM has capabilities such as animation of current positions for "putting on" gear on screen and preparing technical documents, the cinematic schemes and drawings in any scale.

In this system the algorithm of positions calculation for open circuits with the mobile ends - universal Assur group, algorithm of the topological analysis for Assur groups and kinetics-statics algorithms for velocity, acceleration, static and dynamic responses were developed on the basis of a matrix method for gears of such topology. The increased reliability of the matrix method is reached by reduction of non-linear system dimension.

Included in the structure of BDS CADS, the modular subsystem XTools is an integrated set of software tools which are necessary for creation of applied and expert systems for designing.

The set of software tools consists of following elements: graphic system, control system of relational databases and interpreter of logic programming language. Thus the software provides following service functions:

XTools software allows application programmer to:

The graphic system tool allows a developer to create his or her own graphic problem-oriented subsystem in FORTRAN or C++ using:

XTools software provides the developer the capability of having his own subsystem for dialogue monitor programming. For example, creating menu trees with basic menus, computing process control programs with the help of tablet, etc.

XTools software was used for creating an expert system for designing a hydraulic system of Tu-334 airplane with meeting the requirements on reliability and given constraints.

In connection with great development of personal computer capabilities, the CAD/CAM system "CREDO" was created under the control of the operating system MS Windows [5].

The system "CREDO" is the first domestic integrated system for preparation of production working under MS Windows, with capabilities of three-dimensional modeling of geometrical objects, designer documentation preparation, NC programming for the numerical control equipment and creation of an archive of the design-technology documentation (DTD). The last version of archive DTD provides visual survey of the stored documentation and search capabilities by various attributes, including information fields of a title block of delineation.

This software as well as its prototypes are intended for computer aided design process, preparation for production, manufacturing, problem-oriented application systems development in the field of geometrical modeling, and designing and preparation of production for various industries.

The system is developed on a modular principle and allows to solve specific problems. The system has a modern windows interface and contains library of basic tools for constructing geometrical primitives and operations with them in three-dimensional space. It is capable of scaling in performance by enhancing the system with better processors and new functionality added.

The system "CREDO" consists of following subsystems:

Each subsystem functions autonomously from others. At the same time, all of them use uniform functions for storage and display the geometrical information, function of dialogue etc. Therefore the system consists of basic and a set of independent functional modules and uses features of DLL’s (dynamic load-able libraries) in MS Windows. It provides facilities based on the user’s requirement, including functional modules for development, debugging, user applications, connectivity and system resources availability.

The system database provides storage, structuring and control of the information about objects of drawings, geometrical models of items and models of machining processes. The database allows the user to create and to apply standard bars and tools for computer aided processes of geometrical models development.

The user interface of the system is developed according to the requirements for the software to work under MS Windows. The system control is realized by mouse with use of the menus, messages, prompts, directives, lists of the data accompanied with information easily accessible by references, executive operation illustrating sense and character of the information required by user.

The application program interface provides a capability for users to create their own applications using built-in graphic language and languages of a high level (C++, Pascal etc.). With the help of the built-in interactive environment, the user can develop programs using graphic languages of a high level. The capabilities of the language allow to program dialogues with the user, to create and display various objects, to choose objects on screen and obtain geometrical information about the chosen objects etc.

The other tools for application systems development include special libraries of external functions. Users can create application modules (dynamic libraries) in languages of a high level and connect them with system by their standard image. The calls to these subsystems can be implemented from the main menu of a system "CREDO".

The realization of CAD/CAM system "CREDO" in MS Windows on personal computers provides designers and programmers a convenient and effective operating environment and opens for large prospects for creating integrated CAD/CAM systems.

The program complex BDS CADS with the latest version of the geometrical modeling system has received a name "FOREMAN", as well as system "CREDO", is successfully used today in many design bureaus and enterprises of aircraft industry [6].

References

[1] V.P.Lvov. Methodological aspects of creation integrated CAD systems for machine industry // Automation of designing. 1988. N1. pp. 3- 5. (in Russian)

[2] Y.V.Davydov. Concept model for informational exchange in CAD systems // Automation of designing. 1988 N1. pp. 5-11. (in Russian)

[3] Y.V.Davydov. Integration of device designing and tools for its realization // Automation of designing. 1993. N4. pp. 37 – 44. (in Russian)

[4] G.V.Burenkov, V.I.Bykov etc. The automized programm system of designing of lever gears (PARM) // Automation of designing. 1991. N2. pp. 64- 71. (in Russian)

[5] V.P.Lvov, V.A.Zlygarev etc. The geometrical modeling system CREDO/Win // Automation of designing. 1993. N4. pp. 45 - 51. (in Russian)

[6] Y.V.Davydov. The system CREDO and its family tree // PCWEEK. 1997. N30 -31. p. 57. (in Russian)