Quanto Magazine

The Physics of Quadcopters

A quadcopter is a type of multirotor helicopter, which is propelled by a set of four rotors. The have a simple mechanical design which means they are cheap to construct, and available for commercial use.

Quadcopters have seen a major increase in popularity in recent years. One of their most famous appearances in the public eye was their demonstration on TED in 2013.

The sheer maneuverability and control of these things is incredible! You’re probably wondering how these things work – so I’ll outline some of the physics behind them.

Well to start with the drone needs its key components: An electronic flight system, motors, a battery, and propellers. These are also intelligent machines and some quadcopters have miniature sensors in their on-board computer. These can detect changes in air pressure and air pressure, and provide obstacle avoidance and GPS location.

When the drone lifts off, the motors serve the purpose of rotating the blades at super-high speeds, approximately 30,000 RPM for high end drones.

Flight Dynamics

To calculate the Lift of the drone, the formula is:

L = 1/2 pV^2 x S x CL

Where:

p = Air Density (approx 1.2KG/m^3)
v = Velocity
S = Surface Area (of the blade)
CL = Coefficient of lift.

A quadcopter has four blades. When the quad lifts off, two of these blades will rotate clockwise, and the other two will rotate counterclockwise. T
he aim will be to generate enough force upward that is greater that the weight of the drone. Once the drone is in the air, it can then reduce the power, and when the upward force of the blades is equal to the weight of the drone, it will hover.

When the drone wants to move in a direction, the force increase in the two rotors at the opposite end of the direction that the drone wishes to move in. For example, if the drone wishes to move sideways right, the two rotors on the left side of the drone will increase in power.

If the drone wishes to turn in a direction, two diagonal rotors increase in power. For example, if the drone wishes to turn right (turn in a clockwise direction), the front left and back right motor will increase in power. This is because they are rotating counter clockwise.

There are also some commercial drones with more than four rotors, usually six or eight. The more rotors a drone has, the more stable it becomes. It also gives the pilot more accuracy and maneuverability when flying.

Battery

Most drones get very little airtime, with few reaching over 30 minutes. This is because as you increase the battery size, you also increase the weight on the drone. If we were to attach a battery powerful enough to last a few hours – it would be so heavy that the drone wouldn’t get off the ground!

To fuel the motors, most batteries are Lithium Polymer Batteries (LiPos). Never leave these batteries unattended hen charging as they have been known to explode!

For further information take a look at these articles

The different types of drone

This Is How Drones Work

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