Model-based design concept in Simulink - Mini Project: Build & Apply

Model-based design concept

📖 Scenario: You are working on a simple control system for a home heating system. You want to design and simulate the system using model-based design in Simulink. This approach helps you build a visual model of the system, test it, and understand how it behaves before building the real system.

🎯 Goal: Build a basic Simulink model that represents a simple heating control system. You will create the initial model components, configure parameters, implement the control logic, and finally simulate and observe the output.

📋 What You'll Learn

Create a Simulink model with blocks representing system components

Configure block parameters to set system behavior

Implement control logic using Simulink blocks

Simulate the model and observe the output

💡 Why This Matters

🌍 Real World

Model-based design is widely used in engineering fields like automotive, aerospace, and robotics to design and test control systems before building physical prototypes.

💼 Career

Understanding model-based design with Simulink is valuable for roles in control engineering, embedded systems development, and simulation-based testing.

1

Create the initial Simulink model

Open Simulink and create a new model. Add a Constant block named DesiredTemp with value 22 (degrees Celsius). Add a Step block named CurrentTemp with initial value 18 and step time 10 seconds. Connect these blocks to prepare for the control system.

Simulink

% Your Simulink model should have a Constant block named DesiredTemp with value 22
% and a Step block named CurrentTemp with initial value 18 and step time 10
% Connect these blocks appropriately

Hint

Use the Simulink Library Browser to find the Constant and Step blocks. Set their parameters exactly as described.

2

Configure the control parameters

Add a Gain block named ControlGain with gain value 0.5. This block will represent the proportional control strength. Connect the output of the difference between DesiredTemp and CurrentTemp to this Gain block.

Simulink

% Add a Gain block named ControlGain with gain 0.5
% Connect the difference between DesiredTemp and CurrentTemp to ControlGain
% Your code here

Hint

Use a Sum block with signs set to '+-' to subtract CurrentTemp from DesiredTemp. Then connect to the Gain block.

3

Implement the control logic

Add a Scope block to visualize the control output. Connect the output of the ControlGain block to the Scope. This will show how the control signal changes over time.

Simulink

% Add a Scope block
% Connect ControlGain output to Scope input
% Your code here

Hint

Find the Scope block in Simulink and connect it to the output of the Gain block.

4

Simulate and observe the output

Run the simulation for 30 seconds. Observe the control signal in the Scope window. Use sim('modelname', 'StopTime', '30') replacing modelname with your model's name. Then open the Scope to see the control output over time.

Simulink

% Run the simulation for 30 seconds
% Open the Scope to view the control output
% Your code here

Hint

Use the sim function with your model's name and simulation time 30 seconds.

Practice

1. What is the main idea behind Model-based design in Simulink?

easy

A. Building system models using visual blocks to simulate behavior

B. Writing code line by line to create a system

C. Using spreadsheets to analyze data

D. Manually assembling hardware components

Solution

1. Step 1: Understand model-based design in Simulink

   Model-based design uses visual blocks to create models representing systems. Simulink allows simulation of these models to test system behavior before building real hardware.

2. Final Answer:

   Building system models using visual blocks to simulate behavior -> Option A

3. Quick Check:

   Model-based design = Visual block modeling [OK]

Hint: Think visual blocks, not code or hardware [OK]

Common Mistakes:

• Confusing model-based design with coding
• Thinking it involves hardware assembly
• Assuming it uses spreadsheets

2. Which of the following is the correct way to start a new model in Simulink?

easy

A. Use the command start_simulation()

B. Write new_model() in MATLAB command window

C. Open a text editor and type the model code

D. Click File > New > Model

Solution

1. Step 1: Recall Simulink interface basics

   Simulink models are created via the graphical interface using File > New > Model, not by typing commands.

2. Final Answer:

   Click File > New > Model -> Option D

3. Quick Check:

   New model = File > New > Model [OK]

Hint: Use menus, not commands, to create models [OK]

Common Mistakes:

• Trying to create models by MATLAB commands
• Confusing simulation start with model creation
• Using text editors for Simulink models

3. Given this Simulink model snippet, what will the output be after simulation?

Input Signal: Constant block with value 5
Block: Gain block with gain 3
Output: Connected to Gain block output

medium

A. Output will be 5

B. Output will be 8

C. Output will be 15

D. Simulation will fail due to missing blocks

Solution

1. Step 1: Understand blocks and calculate output

   The Constant block outputs 5. The Gain block multiplies input by 3: 5 * 3 = 15.

2. Final Answer:

   Output will be 15 -> Option C

3. Quick Check:

   5 * 3 = 15 [OK]

Hint: Multiply constant by gain for output [OK]

Common Mistakes:

• Adding instead of multiplying
• Confusing input and output values
• Assuming simulation error without reason

4. You created a Simulink model but the simulation does not run. Which of these is the most likely cause?

medium

A. Simulation time set to zero

B. Using too many blocks

C. Model saved in wrong folder

D. Missing connection between blocks

Solution

1. Step 1: Check common simulation errors

   Simulation won't run if simulation time is zero because no time passes. Missing connections cause errors but usually show warnings; too many blocks or folder location don't stop simulation.

2. Final Answer:

   Simulation time set to zero -> Option A

3. Quick Check:

   Simulation time > 0 needed [OK]

Hint: Check simulation time is not zero [OK]

Common Mistakes:

• Ignoring simulation time settings
• Assuming folder location stops simulation
• Thinking too many blocks cause failure

5. You want to model a system where an input signal is doubled, then 4 is added, and finally the result is squared. Which Simulink block sequence correctly represents this?

hard

A. Sum block (+4) -> Gain block (gain=2) -> Math Function block (square)

B. Gain block (gain=2) -> Sum block (+4) -> Math Function block (square)

C. Math Function block (square) -> Gain block (gain=2) -> Sum block (+4)

D. Gain block (gain=2) -> Math Function block (square) -> Sum block (+4)

Solution

1. Step 1: Analyze required operations order

   Input first doubled (Gain=2), then +4 (Sum), then squared (Math Function). Matches Gain -> Sum -> Math Function.

2. Final Answer:

   Gain block (gain=2) -> Sum block (+4) -> Math Function block (square) -> Option B

3. Quick Check:

   Order matters: multiply, add, then square [OK]

Hint: Follow math order: multiply, add, then square [OK]

Common Mistakes:

• Changing operation order
• Adding before multiplying
• Squaring before adding