Running a simulation in Simulink - Mini Project: Build & Apply

Running a simulation

📖 Scenario: You are working on a simple system model in Simulink. You want to run a simulation to see how the system behaves over time.

🎯 Goal: Learn how to set up a basic Simulink model, configure simulation parameters, run the simulation, and view the output results.

📋 What You'll Learn

Create a simple Simulink model with a Sine Wave block and a Scope block

Set the simulation stop time to 10 seconds

Run the simulation

Display the simulation output on the Scope

💡 Why This Matters

🌍 Real World

Simulink simulations are used in engineering to test system designs before building physical prototypes, saving time and cost.

💼 Career

Knowing how to run and analyze simulations is essential for roles in control systems, automotive, aerospace, and robotics engineering.

1

Create the Simulink model

Open Simulink and create a new model. Add a Sine Wave block and a Scope block. Connect the output of the Sine Wave block to the input of the Scope block.

Simulink

% Add a Sine Wave block and a Scope block, then connect them
% Your code here

Hint

Use add_block to add blocks and add_line to connect them.

2

Set simulation stop time

Set the simulation stop time of the model to 10 seconds by assigning set_param(model, 'StopTime', '10').

Simulink

% Create a new Simulink model
model = 'sim_model';
new_system(model);
open_system(model);

% Add Sine Wave block
add_block('simulink/Sources/Sine Wave', [model '/Sine Wave']);

% Add Scope block
add_block('simulink/Sinks/Scope', [model '/Scope']);

% Connect Sine Wave output to Scope input
add_line(model, 'Sine Wave/1', 'Scope/1');

% Set simulation stop time to 10 seconds
% Your code here

Hint

Use set_param with the model name and 'StopTime' parameter.

3

Run the simulation

Run the simulation of the model by calling sim(model) and store the output in a variable called simOut.

Simulink

% Create a new Simulink model
model = 'sim_model';
new_system(model);
open_system(model);

% Add Sine Wave block
add_block('simulink/Sources/Sine Wave', [model '/Sine Wave']);

% Add Scope block
add_block('simulink/Sinks/Scope', [model '/Scope']);

% Connect Sine Wave output to Scope input
add_line(model, 'Sine Wave/1', 'Scope/1');

% Set simulation stop time to 10 seconds
set_param(model, 'StopTime', '10');

% Run the simulation and save output
% Your code here

Hint

Use sim function with the model name and assign the result to simOut.

4

Display the simulation output

Open the Scope window to display the simulation results by calling open_system([model '/Scope']).

Simulink

% Create a new Simulink model
model = 'sim_model';
new_system(model);
open_system(model);

% Add Sine Wave block
add_block('simulink/Sources/Sine Wave', [model '/Sine Wave']);

% Add Scope block
add_block('simulink/Sinks/Scope', [model '/Scope']);

% Connect Sine Wave output to Scope input
add_line(model, 'Sine Wave/1', 'Scope/1');

% Set simulation stop time to 10 seconds
set_param(model, 'StopTime', '10');

% Run the simulation and save output
simOut = sim(model);

% Open the Scope window to view results
% Your code here

Hint

Use open_system with the full path to the Scope block.

Practice

1. What is the main purpose of running a simulation in Simulink?

easy

A. To test and analyze a model's behavior without building physical hardware

B. To write code faster

C. To create graphical user interfaces

D. To compile the model into an executable file

Solution

1. Step 1: Understand simulation purpose

   Simulation allows testing how a model behaves in a virtual environment.

2. Step 2: Compare options

   Only To test and analyze a model's behavior without building physical hardware describes testing and analyzing without physical hardware.

3. Final Answer:

   To test and analyze a model's behavior without building physical hardware -> Option A

4. Quick Check:

   Simulation = safe model testing [OK]

Hint: Simulation means testing model behavior virtually [OK]

Common Mistakes:

• Confusing simulation with code writing
• Thinking simulation creates GUIs
• Assuming simulation compiles code

2. Which command correctly starts a simulation of a Simulink model named myModel?

easy

A. sim('myModel')

B. execute('myModel')

C. start_sim('myModel')

D. run('myModel')

Solution

1. Step 1: Recall Simulink simulation command

   The correct command to run a simulation is sim('modelName').

2. Step 2: Match command to options

   Only sim('myModel') uses sim('myModel') correctly.

3. Final Answer:

   sim('myModel') -> Option A

4. Quick Check:

   sim command runs simulation [OK]

Hint: Use sim('modelName') to start simulation [OK]

Common Mistakes:

• Using run() instead of sim()
• Trying start_sim() which is invalid
• Using execute() which is not a Simulink command

3. Given the code:

out = sim('simpleModel', 'StopTime', '10');
disp(out.tout(end));

What will be displayed?

medium

A. 0

B. 10

C. Simulation error

D. Undefined variable

Solution

1. Step 1: Understand sim command with StopTime

   The simulation runs from time 0 to 10 seconds.

2. Step 2: Check output time vector

   out.tout stores simulation time points; end is last time point, which is 10.

3. Final Answer:

   10 -> Option B

4. Quick Check:

   Simulation end time = 10 [OK]

Hint: tout(end) shows simulation stop time [OK]

Common Mistakes:

• Assuming output is 0 instead of final time
• Expecting an error without cause
• Confusing variable names

4. What is wrong with this code snippet to run a simulation?

sim('modelName', StopTime=20);

medium

A. The StopTime parameter is misspelled

B. The model name must be a variable, not a string

C. StopTime should be a string, not a variable

D. sim command cannot take parameters

Solution

1. Step 1: Check parameter syntax for sim

   Parameters like StopTime must be passed as strings: 'StopTime', '20'.

2. Step 2: Identify error in code

   Code uses StopTime=20 without quotes, causing syntax error.

3. Final Answer:

   StopTime should be a string, not a variable -> Option C

4. Quick Check:

   Parameter names and values must be strings [OK]

Hint: Use quotes for parameter names and values [OK]

Common Mistakes:

• Passing parameters without quotes
• Confusing variable and string types
• Thinking sim can't take parameters

5. You want to run a simulation of controlModel from 0 to 15 seconds and save the output to variable simOut. Which code correctly does this and allows you to access the simulation output data?

hard

A. sim('controlModel', 'StopTime', 15, 'Output', simOut);

B. sim('controlModel', 'StartTime', '0', 'EndTime', '15');

C. simOut = run('controlModel', StopTime='15');

D. simOut = sim('controlModel', 'StopTime', '15');

Solution

1. Step 1: Identify correct sim syntax for stop time and output

   Use sim('modelName', 'StopTime', 'time') and assign output to a variable.

2. Step 2: Evaluate options

   simOut = sim('controlModel', 'StopTime', '15'); correctly assigns output to simOut and sets stop time as string '15'. Others have syntax errors or wrong commands.

3. Final Answer:

   simOut = sim('controlModel', 'StopTime', '15'); -> Option D

4. Quick Check:

   Assign sim output to variable with sim('model', 'StopTime', 'time') [OK]

Hint: Assign sim output to variable; use 'StopTime' as string [OK]

Common Mistakes:

• Passing StopTime as number without quotes
• Using run() instead of sim()
• Incorrect parameter names like StartTime/EndTime