The objective of this tutorial is to acquaint the student with the basic tools needed to use the SIMULINK package on the Unix workstations of the Rensselaer Computing System (RCS). SIMULINK is an extension to MATLAB which uses a icon-driven interface for the construction of a block diagram representation of a process. A block diagram is simply a graphical representation of a process (which is composed of an input, the system, and an output).
Typically, the MATLAB m-file ode45 is used to solve sets of linear and nonlinear ordinary differential equations. The ``traditional'' numerical methods approach is used, e.g. supply the equations to be solved in a function file, and use a general purpose equation solver (linear or nonlinear algebraic, linear or nonlinear differential equation, etc.) which ``calls'' the supplied function file to obtain the solution. One of the reasons why MATLAB is relatively easy to use is that the ``equation solvers'' are supplied for us, and we access these through a command line interface (CLI) (aka the MATLAB prompt, >>). However, SIMULINK uses a graphical user interface (GUI) for solving process simulations. Instead of writing MATLAB code, we simply connect the necessary ``icons'' together to construct the block diagram. The ``icons'' represent possible inputs to the system, parts of the systems, or outputs of the system. SIMULINK allows the user to easily simulate systems of linear and nonlinear ordinary differential equations. A good background in matrix algebra and lumped parameter systems as well as an understanding of MATLAB is required, and we highly recommend that the student thoroughly reads and works through this tutorial. Many of the features of SIMULINK are user-friendly due to the icon-driven interface, yet it is important to spend some time experimenting with SIMULINK and its many features. Dynamic simulation packages (such as MATLAB, SIMULINK, etc.) are being used more and more frequently in the chemical process industries for process simulation and control system design. After completing this tutorial, the student should be able to ``build'' and simulate block diagram representations of dynamic systems.
SIMULINK is an icon-driven state of the art dynamic simulation package that allows the user to specify a block diagram representation of a dynamic process. Assorted sections of the block diagram are represented by icons which are available via various "windows" that the user opens (through double clicking on the icon). The block diagram is composed of icons representing different sections of the process (inputs, state-space models, transfer functions, outputs, etc.) and connections between the icons (which are made by "drawing" a line connecting the icons). Once the block diagram is "built", one has to specify the parameters in the various blocks, for example the gain of a transfer function. Once these parameters are specified, then the user has to set the integration method (of the dynamic equations), stepsize, start and end times of the integration, etc. in the simulation menu of the block diagram window.
In order to use SIMULINK the student must ``start'' a MATLAB session (click on the MATLAB button). Once MATLAB has started up, type simulink (SMALL LETTERS!) at the MATLAB prompt (>>) followed by a carriage return (press the return key). A SIMULINK window should appear shortly, with the following icons: Sources, Sinks, Discrete, Linear, Nonlinear, Connections, Extras (this window is shown in Figure 2). Next, go to the file menu in this window and choose New in order to begin building the block diagram representation of the system of interest.
