Symbolic Methods for VTB Model Development

Summary form only given. Symbolic computation is not just helpful, it is very nearly a prerequisite for building models of complex objects that will be used in dynamic system simulators such as the virtual test bed (VTB). The reason that symbolic computation is so necessary is that, for reasons of compuatational speed, the code of any VTB model having natural coupling ports must directly express the Jacobian of the dynamic equations. Computing the often-large number of Jacobian terms by hand is extremely tedious, time consuming, and error-prone, and entirely unnecessary with today´s symbolic math tools. VTB model developers currently rely on several different tools to accomplish model development. One of the tools, included directly in the VTB distribution package, comes in both runtime and development-time versions that allow a user to directly enter the math equations that describe the system dynamics. Then those equations are either interpreted and symbolically processed on-the-fly during system simulation, or they are interpreted and processed prior to generation of C code that will later be compiled into a model. The combination of these two approaches provides an incremental path for model development: the first approach supports rapidly prototyping of a model, and the second supports final development of full-featured models that may require some additional hand-tailoring of the C code. Additional model development tools that are being developed based on commercial symbolic math packages will also be described