Drones are quite popular these days, and you can get a nice one without spending too much money. Oh, I'm talking about the remotely controlled flying vehicles with four rotors, not the bigger drones scientists use to study climate change and stuff. Those cost a lot of money. Small drones like mine are easy to flya skilled pilot can hover and fly in just about any direction, which makes them great for recording video.
But how does a drone actually fly? Ah, this is an excellent opportunity to look at some physics. Drones use rotors for propulsion and control. You can think of a rotor as a fan, because they work pretty much the same. Spinning blades push air down. Of course, all forces come in pairs, which means that as the rotor pushes down on the air, the air pushes up on the rotor. This is the basic idea behind lift, which comes down to controlling the upward and downward force. The faster the rotors spin, the greater the lift, and vice-versa.
Now, a drone can do three things in the vertical plane: hover, climb, or descend. To hover, the net thrust of the four rotors pushing the drone up must be equal to the gravitational force pulling it down.
So what about moving up, which pilots call climbing? Just increase the thrust speed of the four rotors so that there is a non-zero upward force that is greater than the weight.
After that, you could decrease the thrust a little bitbut there are now three forces on the drone: weight, thrust, and air drag. So, you will still need for the thrusters to be greater than for just a hover.
Descending requires doing the exact opposite: Simply decrease the rotor thrust speed so the net force is downward. Let's say you have a hovering drone pointed north and you want to rotate it to face east. How do you accomplish this by changing the power to the four rotors?
Before answering, I will draw a diagram of the rotors viewed from above labeled 1 through 4. In this configuration, the red rotors are rotating counterclockwise and the green ones are rotating clockwise. With the two sets of rotors rotating in opposite directions, the total angular momentum is zero. Angular momentum is a lot like linear momentum, and you calculate it by multiplying the angular velocity by the moment of inertia.
What is the moment of inertia? Without the battery, everything from the motors to the onboard sensors would not function. It is absolutely vital to choose a battery which can sustain a long enough flight time for your needs. This applies both when buying a new drone, or when building your own. Big drones require more power than smaller ones in most cases, mainly due to the increase in weight. LiPo batteries are increasing being found in all kinds of consumer products e.
Higher volatility means that they should discharged before longer term storage. You can have all types of sensors on a drone, depending on function. If you want to take temperature readings, there are onboard sensors you can add to a drone. You can even add proximity sensors on a drone to help it navigate around obstacles without human input. Now that you know the different components that make a drone, how do they work together to help it fly? Time for a physics crash course on the flight dynamics of drones:.
Quadcopters have 4 rotors fixed to individual motors allowing them to move at different speeds. Two diagonal rotors follow a clockwise rotation while the other two diagonal rotors spin anti-clockwise.
This movement is important because it keeps the quadcopter balanced. If all the motors were to rotate in the same direction, the resulting torque would make the whole craft rotate.
The rotors are designed in such a way that they push down air generating lift. When the rotors push down air, the air pushes back on them propelling the drone upwards. The faster the rotors spin, the faster the drone ascends.
When they slow down, the drone starts to descend. Since the motors next to each are spinning in opposite directions, when you slow down a set of diagonal rotors and speed up the other set, the drone turns to the side with the least speed.
While turning, the lift remains constant so that the drone does not change altitude. It does increase its angular momentum during a turn though. For fixed-wing vehicles, the small wings! Moving them out of their position causes the craft to either pitch up or down. To make the drone yaw -or rotate around the vertical axis — you need to manipulate the vertical stabilizer located at the tail section of the craft. The vertical stabilizer keeps the nose of fixed-wing drones from moving side to side.
When you move the vertical stabilizers correctly, you make the craft rotate the left or right — around the vertical axis. When you want your quadcopter to move forward or back, you need to slow down the motors on either the front or back side, while speeding up rotors on the other side. This makes the drone tilt towards the side that the motors are moving slowest, as you have reduced the lift. The reason the drone then moves in the direction of tilt is because some of the lift is now acting horizontally, whereas when the drone is hovering, all lift is acting downwards.
This horizontal lift component then pushes the drone in the direction of tilt. The slower the motors are rotating on one side, relative to motors on the other side, the greater the tilt. The greater the tilt, the greater the horizontal lift component and the faster you travel.
To control the rotor speeds so that the quadcopter moves as desired, you need a way of communicating with the drone. Most of the time, all you need is a joystick with a wireless transmitter. The transmitter works by alternating the voltage delivered to the motors from the internal battery. When a motor gets more voltage, it rotates faster. When the voltage goes down, it slows down. You regulate the voltage a set of motor receives by simply moving the controls on the transmitter. Drones can do all sorts of things.
They are even more maneuverable and flexible than their larger cousins — helicopters and fixed-wing aircraft. But which features make drones so popular today? What sort of technologies are manufacturers melding with drones? The GPS module, together with the flight controller, give drones the ability to go about their business without additional input from the operator. The GPS module helps the drone arrive at its destination and go back to the point of origin.
They were the first cruise missiles , sometimes called flying torpedoes, and not meant to return to base. During the Cold War , the U.
As the Vietnam War dragged on, drones flew thousands of high-risk reconnaissance missions and were destroyed by enemy fire, but in the process saved the lives of pilots who otherwise would have perished. At about the same time, engineers began equipping drones with real-time surveillance capabilities. With their onboard cameras and unlimited courage, drones could approach enemy lines and document troop movements and strategies without risking human lives. The Predator more precisely, the MQ-1 Predator , with its spine-chilling name, was one of the first military drones to see widespread action.
It was unveiled in and has since zoomed all over the world — but it's used mostly in the Middle East. It can fly more than miles kilometers on single mission and circle targets for hours; armed versions can fire sophisticated missiles.
The Predator is one of the best-known military drones, but now it's just one of many. Those first strikes in Afghanistan were, as they say, just the beginning. As the digital revolution has unfolded with its tiny microprocessors and long-distance communications abilities, drones have become more and more useful for military operations. By one estimate, the U. For anyone who feared the coming age of automated, sci-fi-type warfare The U.
Mini drones are small and mostly used for short-range surveillance. Tactical drones can fly for several hours and as far as miles kilometers and are used to assess enemy targets. Strategic drones can fly for days and carry weapons. Some drones use battery power to turn propellers.
Newer and pricier versions have full-blown jet engines and can fly more than miles kilometers per hour, soaring to 50, feet 15, meters or even higher. Some drones are autonomous, following preprogrammed routines. Many others require pilots. Those pilots may be on the ground near the operation, or they may sit in control rooms, thousands of miles away, guiding their minions by high-speed wireless networking links.
In part because there's a delay of a couple of seconds from the control room to the drone, crashes do happen. Sometimes pilots push the wrong buttons. Sometimes they misread the flight data they see on their workstation monitors; cameras on the drones simply aren't a substitute for a pilot's real vision and other senses.
More than large drones have crashed since , but many disasters have been averted, too. If a communications link is cut, advanced drones are programmed to fly in circles or even to return to the nearest base without human guidance. Like air traffic controllers, drone pilots have high-stress yet often dull and repetitive jobs, mostly surveilling areas for intelligence and potential targets. Because of burnout, they quit three times as often as regular pilots, and the U.
Those who stay receive extensive training in a traditional classroom setting, as well as hands-on training at their computers. They execute endless practice runs and then review their in-flight decisions, attempting to hone their minds to select the best approach to any given scenario, particularly those that involve the use of deadly force.
When they score an important victory, these pilots receive medals just like any others, and in spite of the geographical disconnect from their targets, many suffer emotional trauma from the damage their strikes cause. Not all drones inflict suffering and mayhem. There is an entire range of drones for commercial and private use. In many places, including the U. That does not, however, stop thousands of people from using drones for a plethora of purposes, including videography, sheep herding, product delivery and crop surveying.
If you perform a quick search through your favorite online megastore you'll see that dozens of drones are available. Other costs thousands. There are two broad drone categories: fixed wing and rotary. Each type has its strengths and weaknesses. Fixed-wing drones can be hand-launched, but often they require a runway or even an unwieldy catapult. But they're generally faster and can fly much longer than their rotary brethren. One option is the eBee senseFly, a fixed-wing drone designed specifically for mapping purposes.
Toss it into the air and it follows a preprogrammed route, snapping high-resolution images that are then integrated into maps and 3-D models. It can cover more than 4 square miles Farmers are the primary customers, as they can use the drone to optimize their agricultural practices and increase their yields. The Agribotix Hornet LR is another fixed-wing drone, and like the eBee, it's intended largely for agricultural use.
It has a 6. It can fly for nearly an hour and a half before it must descend for recharging. Fixed-wing drones are fast and fly far, but rotary models are much more common, in part because they're easier to fly and more stable for purposes like photography. If you want a rotary drone, you'll have dozens of options from which to choose.
It's so tiny that it will fit in the palm of your hand. After a minute charging session, you'll get about seven minutes of flight time during which you can make the drone do four-way flips and other stunts. You can also capture pictures on a miniscule 0. The Parrot AR. Drone 2. This drone features upgraded batteries that offer about 36 minutes of flight time. It comes with a free flight control app that you can load to your WiFi-enabled device, such as a tablet or smartphone , letting you control the drone to range of feet 50 meters.
It also has a p HD video camera that streams video live to your device, giving you a bird's-eye view literally on the fly. These drones aren't just for fun — they're intended to give blossoming cinematographers a way to catch amazing high angles without the need for more expensive gear.
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