Physics
-
Thomas Young's Double Slit Experiment
-
Bridge Design and Destruction! (part 1)
-
Bridge Design (and Destruction!) Part 2
-
Shifts in Equilibrium
-
The Marangoni Effect: How to make a soap propelled boat!
-
The Invention of the Battery
-
The Forces on an Airplane
-
Bouncing Droplets: Superhydrophobic and Superhydrophilic Surfaces
-
A Crash Course on Indoor Flying Robots
A Crash Course on Indoor Flying Robots Learn the physics behind how quadrotors fly and find out how they can by themselves without human help.
⇐ Use this menu to view and help create subtitles for this video in many different languages.
You'll probably want to hide YouTube's captions if using these subtitles.
- This is a quadrotor
- It's called a quadrotor because it has four propellars that spin & generate thrust
- This is the pilot controlling a vehicle with a radio transmitter
- That's pretty neat.But if we take a short trip across the street
- Of course looking both ways before we cross
- We come to this place for this quadrotor can fly by itself
- without any human help at all
- We don't even need a pilot
- This flying robot can operate with extreme precision
- in tight indoor spaces
- It can do some other pretty neat stuff as well
- So if you're wondering how to make robots fly
- You've come to the right place
- Indoor Flying Robots!
- A crash course
- Maybe crash course isn't the right term
- Indoor Flying Robots!
- An expedited learning experience
- To figure how to make robots fly
- we'll need to understand the basic physics of quadrotors
- How humans pilot them
- How we can use a computer to achieve the same task
- And why the resulting flying robots can do more complex things
- First let's take a quick look at the physics behind
- how the quadrotors fly
- When the propellers spin they push downward on the air around
- Newton's third law tells us that the air applies in an equal & opposite
- reaction force on the propeller.When this lifting force
- equals that of gravity the quadrotor achieves hoverfly
- In order to bank one propeller spins slightly faster
- than the opposite one
- This introduces a horizontal force in addition to the one opposing gravity
- And the vehicle moves sideways
- That's great, but it didn't tell us how the quadrotor
- can rotate about it's vertical axis
- It turns out that newton's third law also applies to rotational force
- called 'Torque'
- When this two propellers spin they apply a torque to the air
- in the clockwise direction. The air applies in equal and opposite reaction torque
- pushing the vehicle in a counterclock direction meanwhile the other two
- motors spin in the other direction plus the reaction torque
- pushes the vehicle clockwise
- When all four motors are turned on the rotational force
- remember they are called 'Torque' s -balance each other
- In flight the vehicle turns by spinning two motors even so
- slightly faster than the other two
- That went on the basic physics of how quadrotor flies
- But before we can fly it robotically we need to know
- how to control it. First let's figure out how a human would do that
- The task can be broken down into four keysteps
- First, the pilot uses his eyes to observe the vehicle
- and figure out where it is and in which direction it's pointing
- In this example let's say the pilot see is the quadrotor is sinking
- Next, the pilot has to decide what control commands to give the vehicle
- In this case, the pilot has to stop the vehicle from sinking
- And thus decides to increase the speed of all four propellars
- To tell the quadrotor what is decided on the pilot uses a radio transmitter
- which is basically a fancy remote control
- Finally the quadrotor listens for the radio commands
- and adjust the speed of each motor accordingly.
- Now let's see how each of these forces have to change in order to
- fly the quadrotor robotically
- In the first step, we use specialized cameras for vision
- and set up the pilot's eyes. The camera shine infrared light
- which bounces off of more reflective markers on the vehicle
- and go back to the camera
- A camera from the side point of view can tell how far the marker is
- in the vertical direction and one horizontal direction
- And a camera from the top point of view can tell how far the marker is in both
- horizontal directions. Using some slightly more complicated mathematcs
- we can use the points of view from 12 different cameras
- To determine the exact three dimensional position of the markers
- This process is executed many times for second to track the position
- of the markers and pass the quadrotor in real time
- In step two, we use a computer to handle the control commands
- in stead of the pilots brain. The computer program consists of a
- couple hundred lines of C++ code written by grad students
- who really don't get out much. It does essentially the same thing
- as the pilot using the observed position of the quadrotor to evaluate
- control commands. Only it does so in a much faster and less dramatic fshion
- In step three, the system uses a similar radio transmitter except a smaller one
- without any switches or control sticks.
- Step four is exactly as the same as before. The quadrotor listens for
- radio commands and adjust the speed of each motor accordingly.
- So we've updated all four steps in order to make the quadrotor
- fly entirely by itself. Now all we need is for our grad students
- to press the go button and voila. One of the reasons the robot
- fly more precisely than the human pilot is because this loop of information
- called a 'Feedback Control Loop' can be executed much more quickly by computers
- In this case 200 times per second. This allows the researchers
- to do cool things with these indoor flying robots. For instance,
- fly six of them at once but why not ten
- They can teach the vehicles how to switch out their old batteries
- for new ones automically or stop propeller for swing
- They can even do flips like this one or this one or this one
- And the fun doesn't stop with quadrotors. The same technology
- can be applied to rig the shape into three wing aircraft. One more
- conventional fixed wing vehicles like this one, this one and this one
- that can even fly in loops. Well hopefully you've learn the basics of how to make
- robots fly. This concludes the crash course--I, I mean the expedited learning experience
Be specific, and indicate a time in the video:
At 5:31, how is the moon large enough to block the sun? Isn't the sun way larger?
|
Have something that's not a question about this content? |
This discussion area is not meant for answering homework questions.
Discuss the site
For general discussions about Khan Academy, visit our Reddit discussion page.
Flag inappropriate posts
Here are posts to avoid making. If you do encounter them, flag them for attention from our Guardians.
abuse
- disrespectful or offensive
- an advertisement
not helpful
- low quality
- not about the video topic
- soliciting votes or seeking badges
- a homework question
- a duplicate answer
- repeatedly making the same post
wrong category
- a tip or feedback in Questions
- a question in Tips & Feedback
- an answer that should be its own question
about the site
Share a tip
Suggest a fix
Have something that's not a tip or feedback about this content?
This discussion area is not meant for answering homework questions.