Using Simulink    

Quick Start

The following sections use examples to give you a quick introduction to using Simulink to model and simulate dynamic systems.
Running a Demo Model
 Example of how to run a Simulink model.
Building a Simple Model
 Example of how to build a Simulink model.
Setting Simulink Preferences
 How to set Simulink preferences.

Running a Demo Model

An interesting demo program provided with Simulink models the thermodynamics of a house. To run this demo, follow these steps:

  1. Start MATLAB. See your MATLAB documentation if you're not sure how to do this.
  2. Run the demo model by typing thermo in the MATLAB command window. This command starts up Simulink and creates a model window that contains this model.

  3. Double-click the Scope block labeled Thermo Plots.
  1. The Scope block displays two plots labeled Indoor vs. Outdoor Temp and Heat Cost ($), respectively.

  1. To start the simulation, pull down the Simulation menu and choose the Start command (or, on Microsoft Windows, click the Start button on the Simulink toolbar). As the simulation runs, the indoor and outdoor temperatures appear in the Indoor vs. Outdoor Temp plot and the cumulative heating cost appears in the Heat Cost ($) plot.
  2. To stop the simulation, choose the Stop command from the Simulation menu (or click the Pause button on the toolbar). If you want to explore other parts of the model, look over the suggestions in Some Things to Try.
  3. When you're finished running the simulation, close the model by choosing Close from the File menu.

Description of the Demo

The demo models the thermodynamics of a house using a simple model. The thermostat is set to 70 degrees Fahrenheit and is affected by the outside temperature, which varies by applying a sine wave with amplitude of 15 degrees to a base temperature of 50 degrees. This simulates daily temperature fluctuations.

The model uses subsystems to simplify the model diagram and create reusable systems. A subsystem is a group of blocks that is represented by a Subsystem block. This model contains five subsystems: one named Thermostat, one named House, and three Temp Convert subsystems (two convert Fahrenheit to Celsius, one converts Celsius to Fahrenheit).

The internal and external temperatures are fed into the House subsystem, which updates the internal temperature. Double-click the House block to see the underlying blocks in that subsystem.

The Thermostat subsystem models the operation of a thermostat, determining when the heating system is turned on and off. Double-click the block to see the underlying blocks in that subsystem.

Both the outside and inside temperatures are converted from Fahrenheit to Celsius by identical subsystems.

When the heat is on, the heating costs are computed and displayed on the Heat Cost ($) plot on the Thermo Plots Scope. The internal temperature is displayed on the Indoor Temp Scope.


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