Motor and propeller physics basics in Drone Programming - Mini Project: Build & Apply

Motor and Propeller Physics Basics

📖 Scenario: You are programming a simple drone simulation. The drone's motors spin propellers to create lift. You want to calculate the total thrust produced by the drone's motors based on their speeds and propeller characteristics.

🎯 Goal: Build a program that stores motor speeds and propeller thrust factors, calculates the thrust for each motor, sums the total thrust, and displays the result.

📋 What You'll Learn

Create a dictionary with motor names and their speeds in RPM

Create a dictionary with motor names and their propeller thrust factors

Calculate thrust for each motor by multiplying speed and thrust factor

Sum all motor thrusts to get total thrust

Print the total thrust

💡 Why This Matters

🌍 Real World

Drone engineers use motor speeds and propeller characteristics to estimate how much lift a drone can produce, which helps in designing stable and efficient drones.

💼 Career

Understanding motor and propeller physics is important for drone software developers, robotics engineers, and anyone working on flight control systems.

1

Set up motor speeds

Create a dictionary called motor_speeds with these exact entries: 'motor1': 1200, 'motor2': 1300, 'motor3': 1250, 'motor4': 1280

Drone Programming

# Create the motor_speeds dictionary with given values
# Your code here

Hint

Use curly braces to create a dictionary. Each motor name is a key, and its speed in RPM is the value.

2

Set up propeller thrust factors

Create a dictionary called thrust_factors with these exact entries: 'motor1': 0.05, 'motor2': 0.045, 'motor3': 0.048, 'motor4': 0.047

Drone Programming

motor_speeds = {'motor1': 1200, 'motor2': 1300, 'motor3': 1250, 'motor4': 1280}
# Create the thrust_factors dictionary with given values
# Your code here

Hint

Use a dictionary to store the thrust factor for each motor. These numbers represent how much thrust each RPM produces.

3

Calculate total thrust

Create a variable called total_thrust and set it to 0. Then use a for loop with variables motor and speed to iterate over motor_speeds.items(). Inside the loop, multiply speed by the corresponding thrust factor from thrust_factors[motor] and add the result to total_thrust.

Drone Programming

motor_speeds = {'motor1': 1200, 'motor2': 1300, 'motor3': 1250, 'motor4': 1280}
thrust_factors = {'motor1': 0.05, 'motor2': 0.045, 'motor3': 0.048, 'motor4': 0.047}
# Calculate total_thrust by looping over motor_speeds
# Your code here

Hint

Start with total_thrust = 0. Use a for loop to go through each motor and speed. Multiply speed by thrust factor and add to total_thrust.

4

Display total thrust

Write a print statement to display the text Total thrust: followed by the value of total_thrust.

Drone Programming

motor_speeds = {'motor1': 1200, 'motor2': 1300, 'motor3': 1250, 'motor4': 1280}
thrust_factors = {'motor1': 0.05, 'motor2': 0.045, 'motor3': 0.048, 'motor4': 0.047}
total_thrust = 0
for motor, speed in motor_speeds.items():
    total_thrust += speed * thrust_factors[motor]
# Print the total thrust
# Your code here

Hint

Use an f-string in the print statement to show the text and the total_thrust value together.

Practice

1. Which factor directly increases the thrust generated by a drone's propeller?

easy

A. Lowering the drone's weight

B. Increasing the motor speed (rpm)

C. Reducing the battery voltage

D. Decreasing the propeller size

Solution

1. Step 1: Understand thrust formula basics

   Thrust depends on the square of the motor speed (rpm) and the propeller area.

2. Step 2: Identify which factor increases thrust

   Increasing rpm increases thrust because thrust ∝ rpm² x propeller area.

3. Final Answer:

   Increasing the motor speed (rpm) -> Option B

4. Quick Check:

   Thrust ∝ rpm² [OK]

Hint: Thrust grows with rpm squared, so speed up motor [OK]

Common Mistakes:

• Thinking smaller propellers increase thrust
• Confusing power with thrust
• Ignoring rpm's squared effect

2. Which of the following is the correct Python syntax to calculate power given rpm and propeller_area variables?

easy

A. power = rpm ** 2 + propeller_area

B. power = rpm * 3 * propeller_area

C. power = rpm ^ 3 * propeller_area

D. power = rpm ** 3 * propeller_area

Solution

1. Step 1: Recall Python exponent syntax

   Python uses ** for exponentiation, so rpm cubed is rpm ** 3.

2. Step 2: Match formula for power

   Power depends on rpm cubed times propeller area, so multiply rpm ** 3 by propeller_area.

3. Final Answer:

   power = rpm ** 3 * propeller_area -> Option D

4. Quick Check:

   Use ** for power, not ^ or *3 [OK]

Hint: Use ** for powers in Python, not ^ or * number [OK]

Common Mistakes:

• Using ^ instead of ** for exponent
• Multiplying rpm by 3 instead of cubing
• Adding instead of multiplying

3. What is the output of this Python code snippet?

rpm = 1000
propeller_area = 0.05
thrust = rpm ** 2 * propeller_area
print(round(thrust, 1))

medium

A. 50000.0

B. 50000

C. 50000.00

D. 50.0

Solution

1. Step 1: Calculate rpm squared

   rpm ** 2 = 1000 * 1000 = 1,000,000.

2. Step 2: Multiply by propeller_area

   1,000,000 * 0.05 = 50,000.0.

3. Step 3: Check print rounding

   round(50000.0, 1) = 50000.0 and print outputs 50000.0.

4. Final Answer:

   50000.0 -> Option A

5. Quick Check:

   Thrust = 1000² x 0.05 = 50000.0 [OK]

Hint: Square rpm, multiply by area, then round [OK]

Common Mistakes:

• Misreading rounding precision
• Calculating rpm squared incorrectly
• Confusing thrust with power

4. Identify the error in this Python code that calculates power:

rpm = 1200
propeller_area = 0.04
power = rpm ^ 3 * propeller_area
print(power)

medium

A. Multiplying instead of adding propeller_area

B. Missing parentheses around rpm and 3

C. Using ^ instead of ** for exponentiation

D. Incorrect variable names

Solution

1. Step 1: Check exponentiation operator

   In Python, ^ is bitwise XOR, not exponentiation. Use ** for powers.

2. Step 2: Understand impact on calculation

   Using ^ causes wrong calculation or unexpected result, not power of rpm.

3. Final Answer:

   Using ^ instead of ** for exponentiation -> Option C

4. Quick Check:

   Use ** for powers, not ^ [OK]

Hint: Remember ** means power, ^ is bitwise XOR [OK]

Common Mistakes:

• Confusing ^ with **
• Assuming parentheses fix ^ operator
• Ignoring operator precedence

5. You want to program a drone to maintain constant thrust while reducing motor speed to save battery. If you reduce rpm by 20%, how should you adjust the propeller area to keep thrust constant? (Thrust ∝ rpm² x propeller_area)

hard

A. Increase propeller area by 56.25%

B. Increase propeller area by 25%

C. Decrease propeller area by 20%

D. Keep propeller area the same

Solution

1. Step 1: Calculate new rpm ratio squared

   Reducing rpm by 20% means new rpm = 0.8 x original rpm. Squared: 0.8² = 0.64.

2. Step 2: Find required propeller area increase

   To keep thrust constant, propeller_area x 0.64 = original propeller_area. So, new propeller_area = 1 / 0.64 ≈ 1.5625 times original, or 56.25% increase.

3. Final Answer:

   Increase propeller area by 56.25% -> Option A

4. Quick Check:

   Thrust constant -> area ∝ 1 / (rpm²) = 1/0.64 = 1.5625 [OK]

Hint: Square rpm ratio, invert it for area change [OK]

Common Mistakes:

• Forgetting to square rpm ratio
• Adding instead of multiplying percentages
• Assuming area stays same