INTRODUCTION TO SIMULINK by Yasmin Hanum Md Thayoob

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INTRODUCTION TO SIMULINKbyYasmin Hanum Md
ThayoobAidil Azwin Zainul Abidin
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TABLE OF CONTENTS

• What Is Simulink?
• Starting Simulink
• Simulink Windows
• Simulink Library
• Creating A New Model
• Entering Simulink Commands
• Connecting Blocks
• Modeling In Simulink
• Example 1
• Example 2

• Creating Subsystems
• Simulation Parameters
• Running A Simulation
• Getting Output
• Using Scope
• Further Considerations
• Ending A Simulink Session
• Case Study
• References

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What Is Simulink

• Simulink is a graphical method of modeling and
  simulating a mathematical equation or a system in
  Matlab.
• Simulink is not a stand alone program which means
  that it could not be run without running Matlab.
• Whatever variable defined in Matlab can be used
  in Simulink.

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Starting Simulink

• To start Simulink, you must first start MATLAB.
  Consult your MATLAB documentation for more
  information. You can then start Simulink in two
  ways
• Click the Simulink icon on the MATLAB toolbar.
• Enter the simulink command at the MATLAB prompt.
• On Microsoft Windows platforms, starting Simulink
  displays the Simulink Library Browser

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Simulink Windows

• Simulink uses separate windows to display
• a block library browser
• a block library
• a model
• graphical (scope) simulation output
• These windows are not MATLAB figure windows and
  cannot be manipulated using HandleGraphics
  commands.

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Simulink Library

• The Library Browser displays a tree-structured
  view of the Simulink block libraries installed on
  your system. You can build models by copying
  blocks from the Library Browser into a model
  window.

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Sources and Sinks
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Continuous and Discrete Systems

• All dynamic systems can be analyzed as continuous
  or discrete time systems. Simulink allows you to
  represent these systems using transfer functions,
  integration blocks, delay blocks etc.

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Simulink Extras

• Figure 5 contains some advanced linear blocks,
  available in the Simulink Extras ibrary. They
  contain certain advanced blocks, such as a PID
  control block, transfer functions with initial
  conditions, etc.

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Non-linear operators
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Functions and Tables
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Math Block (Mathematical tools)
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Signals Systems Block (Signals and data
transfer)

• In complicated block diagrams, there may arise
  the need to transfer data from one portion to
  another portion of the block. They may be in
  different subsystems. That signal could be dumped
  into a GOTO block, which is used to send signals
  from one subsystem to another.
• Multiplexing helps us remove clutter due to
  excessive connectors, and makes matrix
  (column/row) visualization easier.

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Subsystems Block
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Creating a New Model

• Click the New button on the Simulink Library
  Browsers toolbar (Windows only) or choose New
  from the library windows File menu and select
  Model. You can move the window as you do other
  windows.
• You can build models by copying blocks from the
  Library Browser into a model window (this
  procedure is described later in the modeling
  example ).

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Simulink opens a new model window as below.
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Entering Simulink Commands

• You run Simulink and work with your model by
  entering commands. You can enter commands by
• Selecting items from the Simulink menu bar
• Selecting items from a context-sensitive
  Simulink menu (Windows only)
• Clicking buttons on the Simulink toolbar (Windows
  only)
• Entering commands in the MATLAB command window

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• Using Context-Sensitive Menus to Enter Commands
• Simulink displays a context-sensitive menu when
  you click the right mouse button over a model or
  block library window. The contents of the menu
  depend on whether a block is selected. If a block
  is selected, the menu displays commands that
  apply only to the selected block. If no block is
  selected, themenu displays commands that apply to
  a model or library as a whole.

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Connecting Blocks

• To connect blocks, left-click and drag the mouse
  from the output of one block to the input of
  another block. The figure below shows the steps
  involved.

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Modeling In SimulinkExample 1 Modeling
Equations

• Converting Celsius to Fahrenheit
• To model the equation that converts Celsius
  temperature to Fahrenheit
• TF 9/5(TC) 32
• First, consider the blocks needed to build the
  model
• A Ramp block to input the temperature signal,
  from the Sources library
• A Constant block to define a constant of 32,
  also from the Sources library
• A Gain block to multiply the input signal by
  9/5, from the Math library
• A Sum block to add the two quantities, also
  from the Math library
• A Scope block to display the output, from the
  Sinks library

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• Next, gather the blocks into your model window.
• Assign parameter values to the Gain and Constant
  blocks by opening
• (double-clicking) each block and entering
  the appropriate value. Then, click the Close
  button to apply the value and close the dialog
  box.
• Now, connect the blocks.

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• The Ramp block inputs Celsius temperature. Open
  that block and change the Initial output
  parameter to 0.
• The Gain block multiplies that temperature by the
  constant 9/5. The Sum block adds the value 32 to
  the result and outputs the Fahrenheit
  temperature.
• Open the Scope block to view the output. Now,
  choose Start from the Simulation menu to run the
  simulation. The simulation runs for 10 seconds.

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Example 2 Modeling A Simple Continuous System

• To model the differential equation
• x' (t) 2x (t) u (t)
• where u(t) is a square wave with an amplitude of
  1 and a frequency of 1 rad/sec. The Integrator
  block integrates its input x' to produce x. Other
  blocks needed in this model include a Gain block
  and a Sum block. To generate a square wave, use a
  Signal Generator block and select the Square Wave
  form but change the default units to radians/sec.
  
• Again, view the output using a Scope block.
  Gather the blocks and define the gain.

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• An important concept in this model is the loop
  that includes the Sum block, the Integrator
  block, and the Gain block. In this equation, x is
  the output of the Integrator block. It is also
  the input to the blocks that compute x', on which
  it is based. This relationship is implemented
  using a loop.

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The Scope displays x at each time step. For a
simulation lasting 10 seconds, the output looks
like this
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The equation you modeled in this example can also
be expressed as a transfer function. The model
uses the Transfer Fcn block, which accepts u as
input and outputs x. So, the block implements
x/u. If you substitute sx for x' in the above
equation, you get sx -2x u Solving
for x gives x u /(s 2) or, x / u 1
/ ( s 2)
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The Transfer Fcn block uses parameters to specify
the numerator and denominator coefficients. In
this case, the numerator is 1 and the denominator
is s2. Specify both terms as vectors of
coefficients of successively decreasing powers of
s. In this case the numerator is 1 (or just 1)
and the denominator is 1 2. The model now
becomes quite simple.

• The results of this simulation are identical to
  those of the previous model.

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Creating Sub System

• It helps reduce the number of blocks displayed in
  your model window.
• It allows you to keep functionally related blocks
  together.
• It enables you to establish a hierarchical block
  diagram, where a Subsystem block is on one layer
  and the blocks that make up the subsystem are on
  another.

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Before - After

• Check with model browser in Simulink window
• Label subsytem Ports

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Simulation Parameters

• You can set the simulation parameters for each
  simulation such as run time or solver option

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Simulation Parameters (Continue)
Solver type
Step Size

• Setting simulation time
• Setting solver

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Running A Simulation

• A simulation can be run using 3 ways
• Clicking the start word on the simulation tab
• Clicking the play button on the window
• Pressing CtrlT.

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When a simulation is running, the status bar
displays the status of the simulation, including
the current simulation time and the name of the
current solver. You can display or hide the
status bar by selecting or clearing the Status
Bar option on the Simulink View menu.
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Getting Output

• You can save scope data into workspace (you can
  do this with save to workspace block in sinks
  catagory)
• You can view more than one signal in scope either
  on the same axis or in the separate axis.
• Data can also be exported to the workspace using
  the scope.

Parameters
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Using Scope

• Setting the number of axes for the scope (Figure
  1)
• Saving the data to workspace (Figure 2)

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Further Considerations

• This lecture cant possibly look upon all the
  blocks.
• Another way is to get help concerning the
  block.
• This can be done by double clicking on the block.
  A window will appear where a help button is
  available.
• Click on that button to know what is the
  potential of the block.

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Ending A Simulink Session

• Terminate a Simulink session by closing all
  Simulink windows.
• Terminate a MATLAB session by choosing the
  command below from the File menu
• Exit MATLAB

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References

• SIMULINK Model-Based and System-Based Design
• Matlab Documentation, The MathWorks.
• www.mathworks.com
• http//sts.bwk.tue.n1/7y530/readers/.5CSimuLinkTu
  torial.pdf
• http//www.eng.warwick.ac.uk/staff/msl/progs/simul
  inklab1.pdf
• http//www.engin.umich.edu/group/ctm/working/mac/s
  imulink_basics/