UBC Theses and Dissertations

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UBC Theses and Dissertations

CAM, a computer-aided modelling program for systems dynamics models Chheda, Dhirendra Padamshi


An arbitrary continuous system model can be constructed on a Graphic Display by interacting with a light pen and dials. The user is presented with a control language and a menu on the Graphic Display, which uses pre-defined symbols to design a Continuous System Model. After constructing the model he wants to simulate, the user can assign appropriate variable names and values to the symbols, direct flow of information or material between components, can assign mathematical relationships between the components of a model, and can sketch graphical functions (x-y relationships) on the Graphic Display with the help of cross-hairs. The model, when built, can be saved on disk. In order to make modifications to the model at later time, a previously saved model can be restored. Changes such as altering values, mathematical relationships, and the deletion or addition cf components can be made before rerunning a simulation. Once the user is satisfied with the model description phase and when his model is complete, a CSBP program for that model is written onto disk, which can then be compiled and run in order to obtain the results for the specified variables in tabulated form. As visual aids, plots against Time can also be observed on the Graphic Display or can be plotted cn an X-Y plotter. The CAB system presented here provides an interactive tool for the design, modification and experimentation with Continuous System Models. As such it can enhance the modeller's representation and understanding of reality.

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