Model hierarchy and navigation in Simulink

Introduction

Model hierarchy helps organize complex systems into smaller parts. Navigation lets you move easily between these parts.

When building a large system with many components.

When you want to understand how different parts of a model connect.

When debugging a specific section inside a big model.

When reusing parts of a model in different projects.

When sharing models with others for easier understanding.

Syntax

Simulink

open_system('modelName')
select_system('modelName/SubsystemName')
find_system('modelName','SearchDepth',1)
find_system('modelName')

open_system opens a model or subsystem window.

select_system navigates directly to a subsystem inside a model.

Examples

Opens the main model window named myModel.

Simulink

open_system('myModel')

Jumps to the Controller subsystem inside myModel.

Simulink

select_system('myModel/Controller')

Lists all blocks at the top level of myModel.

Simulink

find_system('myModel','SearchDepth',1)

Gets all blocks inside myModel as a list.

Simulink

find_system('myModel')

Sample Program

This code opens the built-in vdp model, navigates to its Integrator subsystem, then lists all blocks at the top level of the model.

Simulink

open_system('vdp')
select_system('vdp/Integrator')
blocks = find_system('vdp','SearchDepth',1);
disp('Top-level blocks in vdp model:');
for i = 1:length(blocks)
    disp(blocks{i});
end

Important Notes

Model hierarchy helps keep models clean and easy to understand.

Use navigation commands to quickly jump to parts you want to work on.

Remember to save your model after changes to keep hierarchy updated.

Summary

Model hierarchy breaks big models into smaller, manageable parts.

Navigation commands help move between these parts easily.

Using hierarchy and navigation improves model clarity and development speed.

Practice

1. What is the main purpose of using model hierarchy in Simulink?

easy

A. To automatically generate code from the model

B. To increase the simulation speed by skipping blocks

C. To break a large model into smaller, manageable parts

D. To change the color scheme of the model

Solution

1. Step 1: Understand model hierarchy concept

   Model hierarchy means dividing a big model into smaller parts called subsystems or referenced models.

2. Step 2: Identify the main benefit

   This division helps manage complexity and makes the model easier to understand and develop.

3. Final Answer:

   To break a large model into smaller, manageable parts -> Option C

4. Quick Check:

   Model hierarchy = smaller parts [OK]

Hint: Think 'big to small parts' for model hierarchy [OK]

Common Mistakes:

• Confusing hierarchy with simulation speed
• Thinking hierarchy changes model appearance
• Assuming hierarchy auto-generates code

2. Which Simulink command is used to open a subsystem from the current model window?

easy

A. open_system('subsystem_name')

B. close_system('subsystem_name')

C. save_system('subsystem_name')

D. run_system('subsystem_name')

Solution

1. Step 1: Recall command to open subsystems

   The command open_system('name') opens the specified subsystem or model window.

2. Step 2: Verify other commands

   close_system closes, save_system saves, and run_system runs simulations, not open.

3. Final Answer:

   open_system('subsystem_name') -> Option A

4. Quick Check:

   Open subsystem = open_system [OK]

Hint: Use open_system to open any model part [OK]

Common Mistakes:

• Using close_system to open models
• Confusing save_system with open_system
• Assuming run_system opens models

3. Given the following commands in Simulink:

open_system('topModel/subsystem1')
open_system('topModel/subsystem1/subsubsystemA')

What will be the result?

medium

A. Both subsystem1 and subsubsystemA windows open

B. Only subsystem1 window opens

C. Only subsubsystemA window opens

D. An error occurs because subsubsystemA is nested

Solution

1. Step 1: Understand open_system behavior

   Each open_system command opens the specified model or subsystem window independently.

2. Step 2: Analyze nested subsystem opening

   Calling open_system on a nested subsystem opens that window even if parent is already open.

3. Final Answer:

   Both subsystem1 and subsubsystemA windows open -> Option A

4. Quick Check:

   open_system opens each specified window [OK]

Hint: Each open_system call opens its target window [OK]

Common Mistakes:

• Thinking nested subsystems open automatically
• Assuming error on nested subsystem open
• Believing only one window opens at a time

4. You try to navigate to a subsystem using open_system('model//subsystem') but get an error. What is the likely cause?

medium

A. Subsystem does not exist in the model

B. Incorrect path syntax with double slashes

C. Model is not loaded in memory

D. open_system cannot open subsystems

Solution

1. Step 1: Check path syntax

   The path uses double slashes //, which is invalid in Simulink paths.

2. Step 2: Understand correct path format

   Paths should use single slashes / to separate model and subsystem names.

3. Final Answer:

   Incorrect path syntax with double slashes -> Option B

4. Quick Check:

   Use single slash in paths [OK]

Hint: Use single slash '/' in subsystem paths [OK]

Common Mistakes:

• Using double slashes in paths
• Assuming open_system can't open subsystems
• Ignoring model load status

5. You have a large Simulink model with many nested subsystems. To improve navigation and clarity, which approach is best?

hard

A. Use only one big subsystem without nesting

B. Flatten all subsystems into one level to avoid hierarchy

C. Disable hierarchy navigation commands

D. Use model referencing to separate parts into independent models

Solution

1. Step 1: Understand model referencing benefits

   Model referencing breaks large models into separate files, improving clarity and reusability.

2. Step 2: Compare alternatives

   Flattening or using one big subsystem reduces clarity and manageability; disabling navigation removes helpful tools.

3. Final Answer:

   Use model referencing to separate parts into independent models -> Option D

4. Quick Check:

   Model referencing = better clarity and navigation [OK]

Hint: Use model referencing for big, nested models [OK]

Common Mistakes:

• Flattening hierarchy reduces clarity
• Using one big subsystem is hard to manage
• Disabling navigation commands hurts workflow