B1 中級 2084 タグ追加 保存
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


Indoor Flying Robots

2084 タグ追加 保存
李應振 2013 年 2 月 2 日 に公開
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