Sending velocity commands in Drone Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the drone's velocity after this command?

Given the following code snippet that sends velocity commands to a drone, what will be the drone's velocity vector after execution?

Drone Programming

velocity_command = {'vx': 5, 'vy': 0, 'vz': -2}
# Command sent to drone
current_velocity = velocity_command
print(current_velocity)

A {'vx': 5, 'vy': 0, 'vz': -2}

B {'vx': 0, 'vy': 0, 'vz': 0}

C {'vx': -5, 'vy': 0, 'vz': 2}

D None

💡 Hint

Look at the dictionary values assigned to current_velocity.

The velocity_command dictionary sets the drone's velocity directly. Assigning it to current_velocity means the drone's velocity is exactly {'vx': 5, 'vy': 0, 'vz': -2}.

🧠 Conceptual

intermediate

Which velocity command moves the drone straight up?

You want the drone to move straight up at 3 meters per second. Which velocity command dictionary achieves this?

A {'vx': 0, 'vy': 3, 'vz': 0}

B {'vx': 3, 'vy': 0, 'vz': 0}

C {'vx': 0, 'vy': 0, 'vz': 3}

D {'vx': 0, 'vy': 0, 'vz': -3}

💡 Hint

Upward movement affects the vertical velocity component.

The 'vz' key controls vertical velocity. Positive 'vz' moves the drone up, so {'vz': 3} moves it straight up at 3 m/s.

🔧 Debug

advanced

Why does this velocity command cause an error?

This code snippet is intended to send a velocity command to the drone, but it raises an error. What is the cause?

Drone Programming

velocity_command = {'vx': 2, 'vy': 3, 'vz': 'fast'}
send_velocity(velocity_command)

A No error, command sends successfully

B SyntaxError due to missing colon in dictionary

C NameError because send_velocity is not defined

D TypeError because 'vz' value is a string instead of a number

💡 Hint

Check the data types of the velocity values.

Velocity values must be numbers. 'vz' is given as a string 'fast', causing a TypeError when the drone tries to process it.

📝 Syntax

advanced

Which velocity command syntax is correct?

Select the option that correctly defines a velocity command dictionary for moving the drone forward at 4 m/s.

A {'vx': 4, 'vy': 0, 'vz': 0}

B ['vx': 4, 'vy': 0, 'vz': 0]

C {'vx' = 4, 'vy' = 0, 'vz' = 0}

D {vx: 4, vy: 0, vz: 0}

💡 Hint

Remember how to write dictionaries in Python.

Dictionaries require keys in quotes and colons to separate keys and values. Option A follows this syntax correctly.

🚀 Application

expert

What is the resulting velocity after combining two commands?

You have two velocity commands sent sequentially: Command 1: {'vx': 3, 'vy': 2, 'vz': 0} Command 2: {'vx': -1, 'vy': 0, 'vz': 4} If the drone adds these velocity vectors, what is the resulting velocity?

A {'vx': 4, 'vy': 2, 'vz': 4}

B {'vx': 2, 'vy': 2, 'vz': 4}

C {'vx': 2, 'vy': 0, 'vz': 4}

D {'vx': 3, 'vy': 2, 'vz': 0}

💡 Hint

Add the corresponding velocity components from both commands.

Adding vx: 3 + (-1) = 2, vy: 2 + 0 = 2, vz: 0 + 4 = 4 results in {'vx': 2, 'vy': 2, 'vz': 4}.

Practice

1. What does sending a velocity command to a drone usually control?
send_velocity(x_speed, y_speed, z_speed, duration)

easy

A. The drone's battery level

B. The speed and direction the drone moves in each axis

C. The drone's camera angle

D. The drone's GPS coordinates

Solution

1. Step 1: Understand velocity command parameters

   The parameters x_speed, y_speed, and z_speed represent how fast the drone moves along each axis.

2. Step 2: Connect parameters to drone movement

   These speeds control the drone's direction and speed, while duration controls how long it moves.

3. Final Answer:

   The speed and direction the drone moves in each axis -> Option B

4. Quick Check:

   Velocity commands = speed and direction control [OK]

Hint: Velocity commands set speed and direction, not camera or battery [OK]

Common Mistakes:

• Confusing velocity with camera control
• Thinking velocity sets GPS location directly
• Assuming velocity changes battery level

2. Which of the following is the correct syntax to send a velocity command moving the drone forward at 2 m/s for 5 seconds?

easy

A. send_velocity(5, 0, 0, 2)

B. send_velocity(0, 2, 0, 5)

C. send_velocity(0, 0, 2, 5)

D. send_velocity(2, 0, 0, 5)

Solution

1. Step 1: Identify forward direction axis

   Forward movement is usually along the X-axis, so x_speed should be 2.

2. Step 2: Check duration and other speeds

   Y and Z speeds are zero, duration is 5 seconds, matching the command.

3. Final Answer:

   send_velocity(2, 0, 0, 5) -> Option D

4. Quick Check:

   X-axis speed = 2, duration = 5 [OK]

Hint: Forward speed is X-axis; duration is last parameter [OK]

Common Mistakes:

• Mixing up X and Y axes
• Putting duration in wrong position
• Setting speed on wrong axis

3. What will be the drone's movement after running this code?

send_velocity(0, -3, 0, 4)

medium

A. The drone moves left at 3 m/s for 4 seconds

B. The drone moves backward at 3 m/s for 4 seconds

C. The drone moves right at 3 m/s for 4 seconds

D. The drone moves upward at 3 m/s for 4 seconds

Solution

1. Step 1: Identify axis for Y speed

   The Y-axis controls left-right movement; negative means left.

2. Step 2: Interpret speed and duration

   Speed is 3 m/s left for 4 seconds, no movement on X or Z axes.

3. Final Answer:

   The drone moves left at 3 m/s for 4 seconds -> Option A

4. Quick Check:

   Negative Y speed = left movement [OK]

Hint: Negative Y speed means left movement [OK]

Common Mistakes:

• Confusing negative Y with backward
• Mixing Y and Z axes
• Assuming negative means right

4. Identify the error in this velocity command code:

send_velocity(1, 0, 0)

medium

A. Missing duration parameter

B. Wrong order of speed parameters

C. Negative speed value not allowed

D. Extra parameter included

Solution

1. Step 1: Check function parameters

   The function requires four parameters: x_speed, y_speed, z_speed, and duration.

2. Step 2: Identify missing parameter

   Only three parameters are given; duration is missing, causing an error.

3. Final Answer:

   Missing duration parameter -> Option A

4. Quick Check:

   Duration required as 4th parameter [OK]

Hint: Velocity commands need 4 parameters: x, y, z, duration [OK]

Common Mistakes:

• Forgetting duration parameter
• Swapping speed and duration order
• Using negative duration

5. You want the drone to move diagonally upward forward at 1 m/s on X and Z axes for 3 seconds, but keep Y speed zero. Which command is correct?

hard

A. send_velocity(1, 1, 0, 3)

B. send_velocity(0, 1, 1, 3)

C. send_velocity(1, 0, 1, 3)

D. send_velocity(1, 0, 0, 1)

Solution

1. Step 1: Assign speeds to correct axes

   X speed = 1 (forward), Y speed = 0 (no sideways), Z speed = 1 (upward).

2. Step 2: Check duration matches requirement

   Duration is 3 seconds, matching the problem statement.

3. Final Answer:

   send_velocity(1, 0, 1, 3) -> Option C

4. Quick Check:

   X=1, Y=0, Z=1, duration=3 [OK]

Hint: Set speeds on X and Z, zero on Y, duration last [OK]

Common Mistakes:

• Mixing Y and Z speeds
• Wrong duration value
• Setting zero on wrong axis