States and transitions in Simulink - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a state in a Stateflow chart.

Simulink

state [1];
entry: disp('Entering state');

Drag options to blanks, or click blank then click option'

AAction

BTransition

CIdle

DEvent

Attempts:

3 left

💡 Hint

Common Mistakes

Using keywords like 'Transition' or 'Event' as state names.

Leaving the blank empty.

The correct way to define a state is by giving it a name, such as Idle.

2fill in blank

medium

Complete the code to specify a transition condition between states.

Simulink

transition [1];
condition: x > 5;

Drag options to blanks, or click blank then click option'

AIdle_to_Active

BActive_to_Idle

CState1_to_State2

DEvent1_to_Event2

Attempts:

3 left

💡 Hint

Common Mistakes

Using event names instead of transition names.

Using generic names that do not describe the transition.

The transition name should describe the direction, such as Active_to_Idle.

3fill in blank

hard

Fix the error in the transition condition syntax.

Simulink

transition T1;
condition: [1];

Drag options to blanks, or click blank then click option'

Ax >< 10

Bx => 10

Cx = 10

Dx > 10

Attempts:

3 left

💡 Hint

Common Mistakes

Using => which is invalid in this context.

Using = which is assignment, not comparison.

Using >< which is not a valid operator.

The correct comparison operator is > for 'greater than'.

4fill in blank

hard

Fill both blanks to create a transition with a valid event trigger and action.

Simulink

transition T2;
trigger: [1];
action: [2];

Drag options to blanks, or click blank then click option'

Abutton_press

Bstart_motor()

Cstop_motor()

Dtimer_expired

Attempts:

3 left

💡 Hint

Common Mistakes

Using an action as a trigger or vice versa.

Forgetting parentheses in the action function call.

The trigger is an event like button_press, and the action is a function call like start_motor().

5fill in blank

hard

Fill all three blanks to define a state with entry action and a transition with condition.

Simulink

state [1];
entry: [2];
transition T3;
condition: [3];

Drag options to blanks, or click blank then click option'

AProcessing

Bdisp('Start Processing')

Cdata_ready == true

DIdle

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up state names and actions.

Using invalid syntax in the condition.

The state name is Processing, the entry action displays a message, and the transition condition checks if data_ready is true.

Practice

1. In Simulink Stateflow, what does a state represent?

easy

A. A mathematical operation

B. A graphical icon only

C. A data storage variable

D. A mode or condition of the system

Solution

1. Step 1: Understand the role of states in Stateflow

   States represent different modes or conditions that a system can be in during execution.

2. Step 2: Differentiate states from other elements

   States are not variables or operations; they define behavior and system modes.

3. Final Answer:

   A mode or condition of the system -> Option D

4. Quick Check:

   State = system mode [OK]

Hint: States = system modes or conditions [OK]

Common Mistakes:

• Confusing states with variables
• Thinking states are just icons
• Mixing states with mathematical operations

2. Which of the following is the correct syntax to define a transition condition in Simulink Stateflow?

easy

A. state1 => state2 (condition)

B. state1 -> state2 {condition}

C. state1 --> state2 [condition]

D. state1 -- state2 [condition]

Solution

1. Step 1: Recall Stateflow transition syntax

   Transitions use the arrow --> followed by a condition in square brackets.

2. Step 2: Match syntax options

   state1 --> state2 [condition] uses --> and square brackets correctly, others use incorrect symbols or brackets.

3. Final Answer:

   state1 --> state2 [condition] -> Option C

4. Quick Check:

   Transition syntax = --> [condition] [OK]

Hint: Transitions use --> with [condition] brackets [OK]

Common Mistakes:

• Using wrong arrow symbols
• Using curly or round brackets instead of square
• Omitting the condition brackets

3. Given this Stateflow snippet:

state A
  entry: x = 0;
  during: x = x + 1;
end

transition from A to B [x >= 3]

What is the value of x when the system transitions from state A to B?

medium

A. 3

B. 4

C. 2

D. 0

Solution

1. Step 1: Analyze state A behavior

   On entry, x is set to 0. During state A, x increments by 1 each cycle.

2. Step 2: Determine when transition triggers

   Transition triggers when x >= 3. So after 3 increments, x equals 3 and transition occurs.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   Transition at x >= 3 means x = 3 [OK]

Hint: Transition triggers when condition first becomes true [OK]

Common Mistakes:

• Counting increments before entry action
• Assuming transition triggers at x > 3 instead of >= 3
• Forgetting initial value of x

4. Identify the error in this transition definition:

state A
end
state B
end

A --> B (x > 5)

medium

A. Missing condition brackets [] around (x > 5)

B. Incorrect arrow symbol used

C. States must have entry actions

D. Transition must be inside state definitions

Solution

1. Step 1: Check transition condition syntax

   Transition conditions must be enclosed in square brackets [], not parentheses ().

2. Step 2: Verify other syntax elements

   The arrow --> is correct, states can be empty, and transitions are defined outside states.

3. Final Answer:

   Missing condition brackets [] around (x > 5) -> Option A

4. Quick Check:

   Conditions use [] not () [OK]

Hint: Use [] for conditions, not () [OK]

Common Mistakes:

• Using parentheses instead of square brackets
• Thinking arrow is wrong
• Believing states must have actions

5. You want to model a traffic light system with states Red, Green, and Yellow. The system should transition from Green to Yellow only if a timer reaches 60 seconds. Which transition condition correctly models this?

hard

A. Green --> Yellow [timer > 60]

B. Green --> Yellow [timer == 60]

C. Green --> Yellow [timer < 60]

D. Green --> Yellow [timer != 60]

Solution

1. Step 1: Understand the timing condition

   The transition should happen exactly when the timer reaches 60 seconds, so the condition must check equality.

2. Step 2: Evaluate options

   Green --> Yellow [timer == 60] uses timer == 60, which triggers transition at 60 seconds. Others check greater, less, or not equal, which do not match the requirement.

3. Final Answer:

   Green --> Yellow [timer == 60] -> Option B

4. Quick Check:

   Exact timer match triggers transition [OK]

Hint: Use == for exact timer match in transitions [OK]

Common Mistakes:

• Using > or < instead of ==
• Using != which triggers at wrong times
• Forgetting square brackets around condition