Failsafe actions (RTL, Land, SmartRTL) in Drone Programming - Mini Project: Build & Apply

Failsafe Actions: RTL, Land, and SmartRTL

📖 Scenario: You are programming a drone to handle emergency situations safely. When the drone loses connection or faces a critical battery level, it must perform a failsafe action to protect itself and its surroundings.There are three main failsafe actions:RTL (Return to Launch): The drone flies back to its starting point.Land: The drone lands immediately at its current location.SmartRTL: The drone decides the safest way to return home, avoiding obstacles.

🎯 Goal: You will create a program that stores the drone's failsafe actions, sets a current failsafe mode, and then prints the action the drone will take in an emergency.

📋 What You'll Learn

Create a dictionary called failsafe_actions with keys 'RTL', 'Land', and 'SmartRTL' and their descriptions as values.

Create a variable called current_mode and set it to 'SmartRTL'.

Use a for loop with variables mode and description to iterate over failsafe_actions.items() and find the description for current_mode.

Print the message "Failsafe action: <description>" where <description> is the description of the current failsafe mode.

💡 Why This Matters

🌍 Real World

Drones must handle emergencies safely to avoid crashes or damage. Programming failsafe actions helps drones respond automatically when something goes wrong.

💼 Career

Understanding how to manage emergency procedures in drone software is important for drone operators, developers, and engineers working in robotics and unmanned aerial vehicles.

1

Create the failsafe actions dictionary

Create a dictionary called failsafe_actions with these exact entries: 'RTL': 'Return to Launch - fly back to starting point', 'Land': 'Land immediately at current location', and 'SmartRTL': 'Return home safely avoiding obstacles'.

Drone Programming

# Create the failsafe_actions dictionary with the given keys and descriptions
# Your code here

Hint

Use curly braces {} to create the dictionary and separate each key-value pair with a comma.

2

Set the current failsafe mode

Create a variable called current_mode and set it to the string 'SmartRTL'.

Drone Programming

failsafe_actions = {
    'RTL': 'Return to Launch - fly back to starting point',
    'Land': 'Land immediately at current location',
    'SmartRTL': 'Return home safely avoiding obstacles'
}
# Set current_mode to 'SmartRTL'
# Your code here

Hint

Assign the string 'SmartRTL' to the variable current_mode.

3

Find the description for the current failsafe mode

Use a for loop with variables mode and description to iterate over failsafe_actions.items(). Inside the loop, check if mode equals current_mode. If yes, assign description to a variable called action_description.

Drone Programming

failsafe_actions = {
    'RTL': 'Return to Launch - fly back to starting point',
    'Land': 'Land immediately at current location',
    'SmartRTL': 'Return home safely avoiding obstacles'
}

current_mode = 'SmartRTL'

for mode, description in failsafe_actions.items():
    # Check if mode matches current_mode
    # Your code here

Hint

Use if mode == current_mode: inside the loop to find the matching description.

4

Print the failsafe action description

Write a print statement to display the message "Failsafe action: <action_description>" where <action_description> is the variable holding the description of the current failsafe mode.

Drone Programming

failsafe_actions = {
    'RTL': 'Return to Launch - fly back to starting point',
    'Land': 'Land immediately at current location',
    'SmartRTL': 'Return home safely avoiding obstacles'
}

current_mode = 'SmartRTL'

for mode, description in failsafe_actions.items():
    if mode == current_mode:
        action_description = description

# Print the failsafe action message
# Your code here

Hint

Use an f-string inside print to include the variable action_description in the message.

Practice

1. What does the RTL failsafe action do when triggered on a drone?

easy

A. The drone returns to its takeoff point automatically.

B. The drone immediately lands at its current location.

C. The drone hovers in place until manual control is regained.

D. The drone performs a pre-programmed flight path before landing.

Solution

1. Step 1: Understand RTL meaning

   RTL stands for "Return To Launch," meaning the drone flies back to where it took off.

2. Step 2: Compare with other failsafe actions

   Unlike Land or SmartRTL, RTL specifically returns the drone to the takeoff point automatically.

3. Final Answer:

   The drone returns to its takeoff point automatically. -> Option A

4. Quick Check:

   RTL = Return To Launch [OK]

Hint: RTL always means return to the starting point [OK]

Common Mistakes:

• Confusing RTL with immediate landing
• Thinking RTL means hovering
• Assuming RTL follows a custom path

2. Which of the following is the correct syntax to set the failsafe action to Land in a drone programming script?

easy

A. set_failsafeAction('Land')

B. setFailsafeAction(Land)

C. setFailsafeAction("Land")

D. setFailsafeAction('land')

Solution

1. Step 1: Identify string syntax in code

   Failsafe actions are usually passed as strings, so quotes are needed around the word Land.

2. Step 2: Check correct string format

   Double quotes or single quotes can be used, but the option with double quotes and correct capitalization is standard.

3. Final Answer:

   setFailsafeAction("Land") -> Option C

4. Quick Check:

   String with quotes and correct case = setFailsafeAction("Land") [OK]

Hint: Use quotes and correct capitalization for string parameters [OK]

Common Mistakes:

• Omitting quotes around the string
• Using wrong capitalization
• Passing the action as a variable without quotes

3. Given the following code snippet, what will be the drone's behavior if the failsafe is triggered?

failsafe = 'SmartRTL'
if failsafe == 'RTL':
    action = 'Return to launch point'
elif failsafe == 'Land':
    action = 'Land immediately'
elif failsafe == 'SmartRTL':
    action = 'Return home avoiding obstacles'
else:
    action = 'Hover in place'
print(action)

medium

A. Return home avoiding obstacles

B. Land immediately

C. Return to launch point

D. Hover in place

Solution

1. Step 1: Check the value of failsafe variable

   The variable failsafe is set to 'SmartRTL'.

2. Step 2: Follow the if-elif conditions

   The code matches the 'SmartRTL' condition and sets action to 'Return home avoiding obstacles'.

3. Final Answer:

   Return home avoiding obstacles -> Option A

4. Quick Check:

   SmartRTL triggers obstacle-avoiding return [OK]

Hint: Match variable value to condition branches carefully [OK]

Common Mistakes:

• Choosing the default else action
• Confusing SmartRTL with simple RTL
• Ignoring case sensitivity in strings

4. Identify the error in this failsafe action code snippet:

def set_failsafe(action):
    if action = 'RTL':
        return 'Returning home'
    elif action == 'Land':
        return 'Landing now'
    else:
        return 'Hovering'

medium

A. Missing colon after the else statement

B. Using single equals (=) instead of double equals (==) in the if condition

C. Incorrect indentation of the return statements

D. Using single quotes instead of double quotes for strings

Solution

1. Step 1: Check the if condition syntax

   The if condition uses a single equals sign (=), which is assignment, not comparison.

2. Step 2: Confirm correct comparison operator

   Comparison requires double equals (==) to check equality.

3. Final Answer:

   Using single equals (=) instead of double equals (==) in the if condition -> Option B

4. Quick Check:

   Comparison needs '==' not '=' [OK]

Hint: Use '==' for comparison, '=' is assignment [OK]

Common Mistakes:

• Confusing assignment and comparison operators
• Ignoring syntax errors from missing colons
• Assuming quotes style causes errors

5. Given the following code snippet, what failsafe action will be selected?

battery = 15  # percentage
gps_signal = False

if battery < 20 and gps_signal:
    failsafe = 'SmartRTL'
elif battery < 20 and not gps_signal:
    failsafe = 'Land'
else:
    failsafe = 'RTL'

print(failsafe)

hard

A. The drone will choose 'RTL' because battery is sufficient.

B. The drone will choose 'SmartRTL' because battery is low and GPS signal is present.

C. The drone will choose 'Land' because GPS signal is present.

D. The drone will choose 'Land' because battery is low and GPS signal is missing.

Solution

1. Step 1: Analyze battery and GPS conditions

   Battery is 15% (less than 20) and GPS signal is False (missing).

2. Step 2: Follow the if-elif-else logic

   Since battery < 20 and gps_signal is False, the elif condition matches and sets failsafe to 'Land'.

3. Final Answer:

   The drone will choose 'Land' because battery is low and GPS signal is missing. -> Option D

4. Quick Check:

   Low battery + no GPS = Land [OK]

Hint: Check conditions in order: battery then GPS [OK]

Common Mistakes:

• Assuming SmartRTL without GPS signal
• Ignoring battery level in decision
• Mixing up elif and else conditions