Drones | The complete flight dynamics

Summary

This video script delves into the exhilarating world of drone flight mechanics. It explains how BLDC outrunner motors and propeller blades generate lift, enabling takeoff and hovering. The script clarifies the importance of counter-rotating propellers to neutralize torque and maintain stability. It also details how manipulating motor speeds controls yaw, pitch, and roll for directional control. Furthermore, it explores the physics behind moving the drone forward, sideways, and in circular patterns, providing a comprehensive look at the fascinating dynamics of quadcopter flight.

Takeaways

• 🚁 Flying a drone involves complex maneuvers and understanding its flight mechanics is essential for effective operation.
• 🛫 Drones utilize BLDC outrunner motors with propeller blades attached directly to the motor cover for lift generation.
• 🔄 The airfoil principle is key in drone flight, as it allows the propeller blades to generate lift force when air flows over them.
• 📈 The controller adjusts motor speed, which in turn affects the lift force produced by the propellers; higher speed results in greater lift.
• 🛫 Takeoff in a drone is achieved by increasing rotor speed until the collective lift force overcomes the drone's weight.
• 💫 Hovering is maintained by balancing the lift force with the drone's weight, achieved by adjusting rotor speed.
• 🔄 Opposing rotation of diagonally opposite propellers is necessary to counteract reaction torque and prevent the drone from spinning.
• 🌀 Yaw motion is achieved by varying the speed of one diagonal pair of propellers compared to the other, creating a net torque that spins the drone.
• 📊 Pitch and roll are controlled by adjusting the speed of the front and back, or side propellers respectively, to create a net torque that maneuvers the drone.
• 🔄 In both roll and pitch operations, the reaction torques from the motors cancel each other out, ensuring stable drone operation.
• 🌐 To move the drone forward or sideward, it must be pitched or rolled and then balanced vertically to counteract the horizontal component of the propeller force.

Q & A

What is the main purpose of the propeller blades on a drone?

The propeller blades on a drone are the most important part, as they produce lift force when air flows over them due to the airfoil principle, allowing the drone to take off, hover, and maneuver.

How do BLDC motors, specifically outrunner types, contribute to a drone's flight mechanics?

BLDC outrunner motors are used in drones because they have propeller blades attached directly to the motor cover, which allows for efficient conversion of electrical energy into mechanical energy to generate lift.

What is the significance of the lift force produced by the drone's blades?

The lift force produced by the drone's blades is crucial for overcoming the weight of the drone, enabling it to lift off the ground, hover, and perform various maneuvers.

How does the controller modify the drone's flight?

The controller is used to modify the motor speed; a greater blade speed results in a greater lift force, allowing the drone to change its altitude and perform different movements.

What is the 'climbing stage' in drone flight?

The 'climbing stage' is when the rotor speed is increased to the point where the collective lift force produced by the blades overcomes the weight of the drone, causing it to lift off the ground.

Why do opposite pairs of propellers on a drone rotate in different directions?

Opposite pairs of propellers rotate in different directions to counteract the reaction torque that would otherwise cause the drone body to spin, maintaining stability during flight.

What is the role of Newton's third law of motion in drone flight mechanics?

Newton's third law of motion explains that for every action, there is an equal and opposite reaction. In drone flight, this means that as the rotors apply a torque to the air, the stator receives an equal and opposite torque, which must be balanced to prevent the drone from spinning.

How does a drone achieve yaw motion?

Yaw motion is achieved by rotating one diagonal pair of propellers at one speed and the other pair at a different speed, creating a net reaction torque that causes the drone body to spin.

What controls the pitch and roll of a drone?

The pitch and roll of a drone are controlled by the same stick on the remote control. By spinning the front and back propellers at different speeds, the drone pitches, and by spinning the side pairs at different speeds, the drone rolls.

How can a drone move in a perfect circle?

A drone can move in a perfect circle by applying a force that is always perpendicular to its velocity, which can be achieved by combining pitch and roll movements to create the necessary centripetal force.

How does a drone maintain balance during forward or sideward movement?

To maintain balance during forward or sideward movement, the drone must balance the gravitational force with the vertical component of the propeller force, and the horizontal component of the propeller force must be matched by the drag force as the drone moves.

Outlines

00:00

🚁 Understanding Drone Mechanics and Takeoff

This paragraph delves into the mechanics of flying a drone, starting with the basics of takeoff and hovering. It explains the importance of propeller blades and how they generate lift using the airfoil principle. The role of the controller in adjusting motor speed to control lift is highlighted, with an explanation of how increasing rotor speed leads to takeoff and how balancing lift and weight results in hovering. The paragraph also addresses the counter-rotation of diagonally opposite propellers to negate reaction torque and maintain drone stability. Finally, it touches on the principles behind drone maneuvers like yaw, pitch, and roll, and how these are achieved by adjusting the speed of different propellers to create net torque.

05:02

🔄 Advanced Drone Movements and Physics

The second paragraph explores the advanced concepts of drone movement, including pitch, roll, and the physics behind them. It discusses how changing the speed of propellers can create a net torque that results in pitching or rolling the drone. The paragraph explains how the drone's design ensures that reaction torques cancel out, contributing to stable operation. It also covers how to move the drone forward or sideways by pitching or rolling and balancing the drone vertically to counteract horizontal forces. The concept of circular motion is introduced, explaining how a force perpendicular to the drone's velocity can make it turn in a circle. The paragraph concludes with an invitation to learn more about drone dynamics in other videos of the series.

Keywords

💡Drone

A drone is an unmanned aerial vehicle that can be remotely controlled or fly autonomously. In the context of the video, drones are used to demonstrate the principles of flight mechanics, showcasing how they can take off, hover, and maneuver in various directions, which is central to the video's theme of explaining the physics behind drone flight.

💡BLDC Motors

BLDC stands for Brushless Direct Current motors, which are a type of electric motor used in drones. They are known for their efficiency and reliability. In the video, BLDC motors, specifically outrunner types, are mentioned as the power source for the drone's propellers, highlighting their importance in generating lift and enabling flight.

💡Propeller Blades

Propeller blades are the rotating parts of the drone that create lift by pushing air downwards. They are crucial for drone flight as they generate the necessary force to overcome gravity. The script explains how the cross-section of the blades, designed based on the airfoil principle, produces lift, which is a fundamental concept in understanding how drones achieve and maintain flight.

💡Airfoil Principle

The airfoil principle refers to the shape of an object such as an airplane wing or a drone propeller blade, which is designed to generate lift when air flows over it. The script describes how the blade's design ensures that the lift force is in the same direction along its length, which is essential for the drone to achieve lift-off and maintain stable flight.

💡Controller

The controller is the device used to operate the drone, allowing the user to modify motor speeds and control the drone's movements. In the video, the controller is mentioned as the tool that modifies the motor speed, which in turn affects the lift force and the drone's ability to take off, hover, and perform various maneuvers.

💡Takeoff

Takeoff is the process by which a drone transitions from the ground to the air. The script explains that increasing the rotor speed generates enough lift force to overcome the drone's weight, allowing it to lift off. This is a critical phase in drone operation and a key part of the video's exploration of flight mechanics.

💡Hovering

Hovering is the state where a drone maintains a stable position in the air without moving vertically or horizontally. The video describes how, once the necessary height is achieved, the rotor speed can be reduced to balance the lift force with the drone's weight, resulting in levitation, which is more technically known as hovering.

💡Reaction Torque

Reaction torque is the force that opposes the torque applied by the motor to the propeller. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. In the context of the video, reaction torque is discussed to explain why opposite pairs of propellers rotate in different directions to prevent the drone body from spinning.

💡Yaw Motion

Yaw motion refers to the rotation of the drone around its vertical axis. The video explains how yaw is achieved by varying the speed of one diagonal pair of propellers compared to the other, creating a net reaction torque that causes the drone to spin. This is an essential maneuver for changing the drone's orientation.

💡Pitch and Roll

Pitch and roll are angular motions that control the drone's orientation in three-dimensional space. Pitch involves tilting the drone forward or backward, while roll involves tilting it side to side. The script describes how these motions are achieved by adjusting the speed of the front and back propellers for pitch, and the side propellers for roll, creating a net torque that maneuvers the drone.

💡Climbing Stage

The climbing stage is the phase during takeoff when the drone's collective lift force from the propellers overcomes its weight, allowing it to ascend. The video uses this term to describe the initial ascent of the drone, which is a fundamental step in the process of getting from the ground to the air.

💡Drag Force

Drag force is the resistance that opposes the motion of an object through a fluid, such as air. In the context of the video, drag force is mentioned to explain how, after pitching the drone forward, the horizontal component of the propeller force causes the drone to move horizontally until the drag force balances this force, allowing the drone to move forward.

💡Circular Motion

Circular motion is the movement of an object along a circular path. The video script touches on the physics of circular motion to explain how a drone can be maneuvered to fly in a perfect circle. This involves applying a force that is always perpendicular to the drone's velocity, a principle that is key to understanding advanced drone maneuvers.

Highlights

Drones use BLDC (Brushless Direct Current) motors, specifically outrunner types, with propeller blades attached to the motor cover.

Propeller blades are crucial for drone flight, producing lift force through the airfoil principle.

The blade design ensures lift force direction consistency, allowing for total lift force representation.

The controller adjusts motor speed to modify lift force, with higher blade speed generating more lift.

Takeoff involves increasing rotor speed until the collective lift force overcomes the drone's weight.

Drones hover by balancing lift force with the drone's weight after achieving necessary height.

Opposite rotation of diagonally opposite propellers prevents the drone body from spinning.

Newton's third law of motion explains the reaction torque and its effect on drone body stability.

Yaw motion is achieved by varying the speed of diagonal propeller pairs, creating non-cancelled reaction torque.

Pitch and roll are controlled by adjusting the speed of front/back or side propeller pairs, respectively.

In roll and pitch operations, the net reaction torque from motors sums up to zero for stable operation.

Climbing a drone is demonstrated by pitching it forward and then balancing the propeller speeds.

Forward or sideward motion is achieved by pitching or rolling the drone and balancing it vertically.

The horizontal component of propeller force and drag force balance for horizontal drone movement.

Circular motion of a drone is possible by applying a force perpendicular to its velocity.

The video concludes by inviting viewers to explore more drone-related content and support the channel.

Transcripts

flying a drone is great fun

you can do a nice takeoff like this

you can hover it

turn it into any axis you want

and even show off to your friends with

complex maneuvers but how do the flight

mechanics actually work

if you've ever found yourself wondering

that that this video is for you

drones use bldc motors which are

outrunner types

as you can see the propeller blades are

attached to the cover of the motor the

propeller blades are the most important

part of the drone

each cross section of the blade produces

a lift force when air flows over the

blade due to the airfoil principle

the blade is designed such a way that

the lift force produced along the length

will be in the same direction on both

parts of the blades allowing us to

represent the total lift force produced

by the drone blade as shown

the controller is used to modify the

motor speed the greater the blade speed

the greater the lift force

so how do we get from being on land to

being sky high

it's time for takeoff

just increase the rotor speed

as the collective lift force produced by

the blades overcomes the weight of the

drone it will lift from the ground this

is known as the climbing stage when

you've achieved the necessary height you

can reduce the rotor speed until the

lift force exactly balances the drone

weight

there we have it folks

levitation more technically known as

drone hovering

in both the drone takeoff and hovering

stages all the four propellers rotate at

the same speed but do you notice

anything strange about this visual

you might have spotted that one

diagonally opposite pair of propellers

rotate in one direction and the other

pair rotates in the other direction

it might look strange but if all the

propellers were spinning in the same

direction the drone body would have spun

in the opposite direction

let's see why this is the case

the stator of the motor is attached to

the drone body

the rotor of the motor turns because it

is receiving a torque from the stator

enter newton's third law of motion

if the rotor is receiving a torque from

the stator the stator will also receive

an equal amount of torque but in the

opposite direction from the rotor

if all the rotors are spinning in the

same direction the drone body will

receive reaction torque as shown

what would happen then

the net effect of these four reaction

torques would force the drone body to

turn in the same direction of the

reaction torque or in the opposite

direction of propeller rotation

by spinning the propeller pairs in the

opposite direction we are in fact making

the net reaction torque zero

interestingly the same physics is used

to achieve the yaw motion in normal

conditions all the blades will be

spinning at the same speed the yaw

motion is produced by rotating one

diagonal pair at one speed and the other

pair at a different speed

in this case the reaction torque will

not cancel out and the drone body will

spin as shown

when you control the yaw stick of the

remote control this is what happens

let's learn about the other two angular

motions of the drone pitch and roll

the pitch and roll of a drone is

controlled by the same stick

and they work based on the same physics

to pitch the drone forward the front

propellers are spun at a lower speed and

the back propellers at a higher speed

this creates a different lift force at

the front and back and thus a net torque

the net torque causes the drone to pitch

to roll the drone the same trick is

applied but to the side pairs

here one side pair is spun faster and

the other slower

once again the net torque forces the

drone to go for a roll motion

one interesting thing to note both in

the roll and pitch operation is that

even though you are changing the speed

of the propellers when you add up the

reaction torques produced by the motors

it becomes zero

this is the beauty of quadcopter drone

design they make way for stable drone

operation

the beginning of this video we saw how

to climb a drone

now let's see how the drone is flowing

forward or sideward

assume you are pitching the drone

forward after you achieve the desired

pitch angle you brought the propeller

speeds to the same value so that it

won't pitch further

the question is whether the drone can

balance here at this tilted angle

the answer is no to balance the drone we

have to first balance the gravitational

force suppose the propeller speed is

such a way that the vertical component

of the propeller force balances the

weight

here comes the issue the propeller force

has a horizontal component as well even

though the vertical forces are balanced

the unbalanced horizontal force will

move the drone horizontally this will

cause a drag force on the drone's body

the drone will increase its speed

horizontally until the drag force

matches the horizontal force

in short to fly the drone forward you

just pitch down the drone and balance it

vertically

the drone does the rest automatically

moving forward

to get the side motion the same physics

is used roll the drone towards one side

and balance it vertically

so here's a question for you is it

possible to move the drone in a perfect

circle

the secret lies in the physics of

circular motion let's shake off the dust

and brush up on our basic principles

consider an object moving in a straight

line when acted on by a force that is

always perpendicular to its velocity the

object will turn in a circle

now you have the answer in your mind for

example you can make the drone move

straight by pitching it down

now if you roll the drone as well you

can easily produce a force perpendicular

to the drone velocity

this will make the drone turn in a

circle

if you've enjoyed learning about the

interesting flight dynamics of the

quadcopter drone why not check out the

other videos in our drone series

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