The following are general tips and should be used often.

- In order to save your work, select Save from the file menu and give
the file that you want to save a name (or choose an old name if you are
``writing over'' an old version), and click the ok button (using the left-most
mouse button). Realize that you have a choice of the ``folder'' that the file
is saved in.
- The PID Controller block parameters are entered in as: , , .
- The following transfer function (in the Laplace domain)
is entered into the

**transfer function**icon by double clicking on the**transfer function**icon and entering the numerator and denominator polynomial coefficients. The numerator coefficients would be entered as [2 1] and the denominator coefficients are entered as [10 5 1]. - The following state-space A matrix
is entered into the

**state space**icon as [1.0 -2.8;-3.1 0.2]. - The results of a simulation can be sent to the
**MATLAB**window by the use of the**to workspace**icon from the Sinks window. Open the**to workspace**icon and select the variable name that you want the results stored in the**MATLAB**workspace. - If your simulation has n state (or output) variables and you want to
save them as different names, then you have to use a special connection called
a
**Demux**(as in demultiplexer) icon which is found in the Connections window. Basically, it takes a vector input and converts it into several scalar lines. You can set the number of outputs (scalar lines) by double clicking on the icon and changing the number of outputs. A**Mux**icon takes several scalar inputs and multiplexes those in a vector (useful sometimes in transferring the results of a simulation to the**MATLAB**workspace, for example). - You can generate white (random) noise by selecting the
**white noise**icon from the Source window. - You can use a
**Gain**icon from the Linear window if you need to multiple a signal by a constant number. - You can convert back to physical variables after a state-space or
transfer function simulation by using the
**Constant**icon from the Sources window and a**Sum**icon from the Sources window. To do this for a scalar output signal, just enter the value of the steady-state into the**Constant**icon and add this to the scalar output using the**Sum**icon. For a vector output, you must first "break-up" the vector into scalar outputs using the**Demux**icon and then add the steady-state value to each scalar output. - The signs of the
**Sum**icon may be changed to negative (in order to subtract) by double clicking on the**Sum**icon and changing the sign from a positive to a negative sign. The number of inputs to the**Sum**icon may be changed by double clicking on the**Sum**icon and setting the number of inputs in the window. - Make sure to set the integration parameters in the simulation menu.
In particular, the default minimum and maximum step sizes must be changed
(they should be around 1/100 to 1/10 of the dominant (slowest) time constant of your system).
- Parameters can be "passed" to
**SIMULINK**from the**MATLAB**window by using the parameter in a**SIMULINK**block or parameter box and defining the parameter in the**MATLAB**window. For example, say that one wants to run the simulation with many different process gains, then in the**transfer function**icon the gain (in the numerator) can be given the symbol k (or any symbol) and then at the**MATLAB**prompt define k = 1.0. Run the simulation, then at the**MATLAB**prompt redefine k = 1.5, etc. This is very useful if the student wants to study the influence of a parameter on the dynamic behavior of a process (important in determining stability). - In order to print the block diagram, first save the block diagram. Then,
at the
**MATLAB**prompt, type:*print -sname-of-simulink-block*where

*name-of-simulink-block*is the name that you saved the block diagram under. For example, if you saved the block diagram as*homework1.m*, then you would type:*print -shomework1* - Time delays (deadtimes) can be simulated in
**SIMULINK**easily by using a**transport delay**icon from the Nonlinear window. Double click on the**transport delay**icon to set the value of the deadtime. - Nonlinear systems can be simulated in
**SIMULINK**using an**s-function**icon from the Extras window. The nonlinear ordinary differential equations must be specified in an m-file, and the name of this m-file is specified in the**s-function**by the user. We will generally supply the student with the m-file containing the nonlinear ordinary differential equations.

Lou Russo, Howard P. Isermann Dept. of Chemical Engineering