Manual De Simulink

Module 2 Introduction to SIMULINK

Although the standard MATLAB package is useful for linear systems analysis, SIMULINK is far more useful for control system simulation. SIMULINK enables the rapid construction and simulation of control block diagrams. The goal of the tutorial is to introduce the use of SIMULINK for control system simulation. The version available at the time of writing of thistextbook is SIMULINK 4, part of Release 12 (including MATLAB 6) from MATHWORKS. The version that you are using can be obtained by entering ver in the MATLAB Command Window. The easiest way to learn how to use SIMULINK is to implement each step of the tutorial, rather than simply reading it. The basic steps to using SIMULINK are independent of the platform (PC, MAC, UNIX, LINUX…). M2.1 BackgroundM2.2 Open-loop Simulations M2.3 Closed-loop Simulations M2.4 Developing Alternative Controller Icons

© 4 July 2001 – B.W. Bequette

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SIMULINK Tutorial

M2.1 Background
The first step is to startup MATLAB on the machine you are using. In the Launch Pad window of the MATLAB desktop, select S IMULINK and then the S IMULINK Library Browser. A number of options are listed, as shown inFigure M2.1. Notice that Continuous has been highlighted; this will provide a list of continuous function blocks available. Selecting Continuous will provide the list of blocks shown in Figure M2.2. The ones that we often use are Transfer Fcn and StateSpace.

Figure M2.1 SIMULINK Library Browser.

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Figure M2.2 SIMULINK Continuous Blocks. Selecting the Sources icon yields the library shown inFigure M2.3. The most commonly used sources are Clock (which is used to generate a time vector), and Step (which generates a step input).

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Figure M2.3 SIMULINK Sources. The Sinks icon from Figure M2.1 can be selected to reveal the set of sinks icons shown in Figure M2.4. The one that we use most often is the To Workspace icon. A variable passed to this

5 icon iswritten to a vector in the MATLAB workspace. The default data method shoulb be changed from “structure” to “matrix” in order to save data in an appropriate form for plotting.

Figure M2.4 SIMULINK Sinks.

M2.2 Open-Loop Simulation
You now have enough information to generate an open-loop simulation. The Clock, simout, step and Transfer function blocks can be dragged to a model (.mdl) workspace,as shown in Figure M2.5a. Renaming the blocks and variables, and connecting the blocks, results in the model shown in Figure M2.5b. The transfer function studied is the Van de Vusse reactor (Module 5). The s-polynomials in the process transfer function were entered by double-clicking on the transfer function icon and entering the coefficients for the numerator and denominator

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polynomials. Notice also that the default step (used for the step input change) is to step from a value of 0 to a value of 1 at t = 1. These default values can be changed by double-clicking the step icon. The simulation parameters can be changed by going to the Simulation “pull-down” menu and modifying the stop time (default = 10) or the integration solver method (default = ode45).
simoutClock To Workspace simout To Workspace1

1 s+1 Step Transfer Fcn

simout To Workspace2

a. Placement of function blocks
t Clock time u manipulated input -1.117s+3.1472 2 +4.6429s+5.3821 s step input Transfer Fcn

y measured output

b. Renaming and connection of blocks Figure M2.5 Development of an Open-loop Simulation. The reader should generate simulations and observe the “inverseresponse” behavior of the output with respect to a step input change. Use the subplot command to place the process output (y) on the top plot, and the manipulated input (u) on the bottom plot. Perform this now. If desired, change the default simulation stop time by selecting the parameters “pull down” menu.

M2.3 Feedback Control Simulation
The Math icon from Figure M2.2 can be selected,...