Running a simulation in Simulink - Cheat Sheet & Quick Revision

Recall & Review

beginner

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

To test and observe how a model behaves over time without building a physical system.

beginner

Which button do you press to start a simulation in Simulink?

The 'Run' button, usually shown as a green triangle in the toolbar.

beginner

What does the 'Stop Time' parameter control in a Simulink simulation?

It sets how long the simulation will run before it stops automatically.

beginner

How can you view the results of a simulation in Simulink?

By using scopes or output blocks that display graphs or data after running the simulation.

intermediate

Why is it important to set the correct solver before running a simulation?

Because the solver decides how the model calculations are done and affects accuracy and speed.

What does pressing the 'Run' button in Simulink do?

A Opens the settings

B Saves the model

C Closes Simulink

D Starts the simulation

Pressing 'Run' starts the simulation to see how the model behaves.

Which parameter controls how long a simulation runs?

A Stop Time

B Solver Type

C Step Size

D Start Time

Stop Time sets the duration for the simulation to run.

How can you see the output of a simulation in Simulink?

A Using scopes or output blocks

B By saving the model

C By changing the solver

D By opening the library browser

Scopes and output blocks show simulation results visually.

What happens if you set the solver incorrectly before running a simulation?

A Simulation will run faster always

B Model will automatically fix it

C Simulation might be inaccurate or slow

D No effect on simulation

The solver affects accuracy and speed; wrong settings can cause problems.

What is the first step to run a simulation in Simulink?

A Click the 'Run' button

B Set the stop time

C Open the scope

D Save the model

You should set the stop time to define how long the simulation runs before clicking 'Run'.

Explain the steps to run a simulation in Simulink and how to view the results.

Think about what you do before and after pressing run.

Why is choosing the right solver important when running a simulation?

Consider how the solver affects the model's behavior.

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