Application of the AutoLisp simulator

Implementation of a hall pricing program

The pricing of a hall structure is a comlex process. Hall pricing means that an engineer or sales person generates a quotation for the the whole structure, including the cost and the weight of the components and the structure. Beside the cost, the weight is also important to decide how many and what type of trucks are required to deliver the components of the structure to the building site. During the pricing process all components must be accounted. Figure 1 shows a general overview of a hall structure. The main structural system of a hall structure consits of frames. To be able to cover the hall a girder system is also introduced. Finally trapezoidal sheeting is used to cover the hall. The different structural systems are attached to each other by screws and bolts. The joints and details are dictated by the engineering design as shown in Figure 2. The complexity of the figure also shows that the pricing program must include a lot of engineering know-how.

Figure 1Figure 2

The original pricing program has been implemented in AutoLISP under AutoCAD. The program accepts user input through a series of dialog windows. The minimum required list of input contains: Using these input data the pricing program draws the 2D views of the hall structure in AutoCAD as shown in Figure 3. At the same time the AutoLISP program attaches non-graphical data to the graphical objects, for example in a simple case the type of the object and how many screws or bolts are required to fix the component. When the design process is finished the generated 2D drawings can be used by the engineers or fabricators, but more importantly the price and the weight of the hall structure can be determined from the non-graphical data. A part of the generated output in Excel format is shown in Figure 4.

Figure 3 Figure 4

New company strategy

The implemented AutoLISP program is mainly used by engineers as the knowledge of AutoCAD is also required. However it became a requirement that marketing and sales personal should be able to use the pricing program. To solve this problem the company has decided to implement a new strategy.

The analysis and pricing part of the design process is centralised. The programs to perform these tasks are placed on a central server. A new graphical program has been created which can be more easily handled and it does not require any engineering knowledge. This graphical program can connect to the central server, where all engineering decisions and calculations are made. This means that the engineering know-how and the company resources are tightly controlled, as they are kept on the central server and the newly developed graphical program can be distributed freely as it does not contain any company information. In this way it is possible for an international company to transfer its design process to the Internet and to make a unified design interface for all sub-branches and sub-contractors in different regions of Europe.

To achieve this strategy a working pricing program is required. To reprogram the original pricing program, containing a lot of engineering know-how would be very difficult. Furthermore even if the original AutoCAD system is kept as an execution environment, problems would arise as it is not scalable, since for every execution the full featured CAD system has to start up. Moreover the execution of the AutoLISP pricing program would require several copies of AutoCAD as several simultaneous connections can be made through the Internet.

To avoid all these problems the current project has been initiated to create a simulation environment which can execute the already implemented pricing program. This means that an AutoLISP language simulator has to be implemented.

For the current project, to implement the AutoLISP execution environment, PLT-Scheme, one of the most modern Scheme implementations has been selected. The reasons for selecting PLT-Scheme are:

Implementation details of the AutoLISP simulator in PLT-Scheme

Some details of the program

For further details or enquiries, please contact the author.

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Copyright © 2007, Péter Iványi