Study On The Theories And Methods Of Virtual Environment Railway Location System

Railway location design is a kind of synthetic work cncluding planning and designing. Designs in railway location, such as route selection, alignments design, alternatives evaluation, and alignment optimization, are all very complex. In order to find out a location satisfying all the requirements about politics, economy and technology, a location engineer must analyse the natural environment consisting of topographic, geological and hydrological conditions. As the determination of railway location depends on the analysis natural conditions, the relationship is much more important between railway location and natural environment than some other engineering projects. In order to improve the design quality and increase the design speed, since the early of 1950, experts and researchers in the field of railway and highway, have begun to find out the methods applying computer and its services to help engineers to do their location tasks. Also there have been some practical software, these software can only be used to provide help in some special tasks. The problem existed in theses software is that one system offers little assistance to co-ordinate and exchange information with other system. This problem has been identified by many authors in construction industry and it has been exemplified as islands of automation. It is difficult to use these tools developed in island model to help the engineer in their work with creativeness. To develop an integrated railway location has become the main subject. In this thesis, an idea of VIRTUAL ENVIRONMENT RAILWAY LOCATION SYSTEM has been put forward. This thesis will study on the theories and mthods about developing Virtual Environment Railway Location system. 1 This thesis put forward the idea of "Virtual Environment"firstly. In this thesis, tasks about developing intelligent interface, graph kernel system, knowledge and reference machine and engineering database are all defined as Intelligent Environment Modeling. Methods about identify, handle with and use the digital space information are defined as Natural Environment Modeling. With this definition the technology about computer aided railway location becomes more standard and unify. 2 By applying knowledge-based engineering and objected-oriented modeling to develop intelligent railway location system, this thesis has realized to transform information and knowledge intelligently. Based on the analysis of the structure and classification of domain knowledge in railway location, the methods of object-oriented knowledge expression have been studied. And a method of class-predicate logic knowledge expression has been presented. By combining traditional predicate logic knowledge expression with object-oriented technology, this method has much more ability in knowledge expression. According to the properties of railway location knowledge, this thesis suggests 15 categories to represent the knowledge about the characterization of a single object:, that are knowledge about attribute knowledge, knowledge about analysis, knowledge about synthesize, knowledge about axiom, knowledge about controlling the procedure, knowledge about design action, knowledge about alternative assessment, knowledge about decision making, knowledge about object selection, knowledge about design status, knowledge about object topology, knowledge about procedure, knowledge about data, knowledge about the information transform. This kind of classification has been proved convenient to the expression and application of knowledge. In this thesis, a mixed object-oriented knowledge expression model and its reasoning mechanism to railway location knowledge is given. By using this model, The reasoning mechanism can only reason the sub-domain knowledge base that is related to the problem to be solved. By this way, the reasoning space becomes very small. In this thesis an inspiration and model identify technology based on the graphical interface is put forward. With this technology the complexity can be decrease and the efficiency of intelligent design can be increase greatly. By integrating object-oriented modeling, isomeric database, constraint database and uncertainty database technologies, this thesis develop a practical prototype for railway location engineering database. A structure of FDBMS (Federated Database System) is applied to this model. By adding constraints to related database, this thesis has applied the constraint database technology to railway location engineering database successfully. This is a promotion for constrain database from theory to practice. The uncertain database in railway location engineering database is also an augment on traditional related database. In integrating the whole engineering database, this thesis used the path-index technology. This can be realized easily by combined programming method. 3 From the viewpoint of virtual natural environment modeling, and through analyzing the characteristics of railway location, this thesis presented a practical fast algorithm for TIN-DTM generation. This method takes many characteristics of large strip terrain area into consideration, such as mapping area, boundaries, characteristic lines, and special areas, etc. And several data structures have been used to increase the efficiency of generation and application of TIN-DTM. This method is more effective and reliable to establish continuous strip TIN-DTM than other conventional methods. As the 3D surface model will be not only used to show the design results in 3D space, but also be used to estimate the possible corridor in 3D scene, the sub system for developing 3D models should be integrated with the main system. This makes the transition of information much easy. Based on the analyses of several types of curve surface models, the author has employed a Free-surface model, Coons surface model, to depict the design curve surface of railway formation. The principle of Free-surface model is to construct the interpolation curve surface piece by 3D boundary lines and connect these pieces with chain table to form the curve surface model of the whole design surface. As Coons surface provides a controlled surface, the designer can modify the formation of the surface by changing the boundary conditions on screen. If the four vertexes of a piece of curve surface are given, a Coons surface function can be constructed. By using Coos to depict design surface, not only the block feature on the surface of roadbed can be taken into consideration, but the not continuous features on surface boundaries can also be handle with smoothly. And the calculation set up on Coons surface is very simple. For describing real terrain surface, this thesis employs the fractal Brownian model that has been proved as a good mathematical model in space information study field. The interpolation based on fractal Brownian model constructs a 3D-terrain surface fast and distinctly. This thesis also suggests that a 3D-projected grid be generated during the calculation of coordinate transformation. This idea can solve several difficult problem of 3D interaction in 2D environment. 4. Being directed against several key problems in railway location, this thesis presents the intelligent CAD methods for solving railway location problems with virtual environment railway location system. In this thesis, the author presents an intelligent cad method for railway local route selection. With this method, engineer can estimate the railway corridor roughly in a 3D topographical environment first; then, in a 2D contour map interface, select the possible route by using intelligent methods. The Hypertext model for inquiring about knowledge and guiding location procedure combines the knowledge and reasoning mechanism with Hypertext system. In this way the huge information in text and graphical model can be organized, stored, and appliedefficiently. With the fast increasing of land price, the cost of railway right of way has become an important part. In the computer aided optimum design of railway alignment, with the varying of horizontal alignment the effect on the design result caused by the cost of right of way must be considered. On the other hand, for the purpose of computing the cost of right of way, the information of land value is needed. In order to realize the computer aided railway design, it is necessary to let computer distinguish the soil characteristic and deal with the information of land values. In order to express the features of land values with numeral method, the author presents a new concept of Digital Model of Land Price (DMLP). With the example of a square grid strip DMLP, this thesis describes how to set up a DMLP and to calculate the cost for purchasing land by computer using DMLP. For the purpose of optimization an initial horizontal alignment should be generated for each possible route. This thesis is aimed to study on the method about producing an initial horizontal alignment scheme for the optimization of a new railway line. In order to obtain a reasonable initial horizontal alignment quickly, the procedure of generating initial horizontal alignment is divided into two stages: first, from the centerline of selected route, find a chain-liked-fold-line by using optimizing method; then based on the chain-liked-fold-line, generate an straight-curve-straight initial horizontal alignment. By using computer to generate initial level alignment the design of alignments can be completed much automatically. By combining interactive graphic CAD and optimizing methods this thesis presents an intelligent optimum method for railway location. Using this method the optimization of alignments of railway can be realized with automated optimum and interactive graphic design alternatively. The result makes optimum technique for railway location more completed. By0the methods of interactive graphic design and optimum techniques, the optimization of railway location in a wider area can be realized. According to the characteristic indexes and their relations in railway location, this thesis constructs a multi-analyzing structure for evaluating schemes of railway location by dividing the program for evaluating schemes into several sub-programs. Using Intelligent CAD system for Railway location, the information for constructing the judgement matrix can be produced automatically. On considering the features of railway location system, this thesis illustrated a model for evaluating schemes of railway location synthetically, that is multi-objective gray relevant optimized decision-making model of engineering system with preference information of schemes. The evaluating method presented in this thesis is simple, scientific and applicable. The selection of major standards is very important in railway location. Based on the virtual environment railway location system, this thesis suggests a new idea for selecting the major standards. 5 At last, by using the methods presented in this thesis, the author has developed a prototype of intelligent CAD system for railway location (PIRLPS). The major functions in IRLPS have been tested and verified by several examples. The results show that the theories employed and methods presented in this thesis are scientific and applicable. Although studies in this thesis are aimed at railway location, the theories and methods presented in this thesis can been used to develop highway location system directly. Some theories and methods can also be used to other civil engineering system based on terrain information.