Basics about drones – Drone component and movement definitions

Definition of a drone

Drones or Unmanned Aerial Vehicles have been around for quite some time now. They made their debut in the military sector and were caused quite a stir for decades. As technology advanced, drones became more mainstream and many civil sectors found great use for their versatility. However, these days, owing to their popularity as a personal toy, you are bound to see some of them droning around right in your backyard.

In technical terms, a drone can be defined as an unmanned aircraft. In simple words, it is an aircraft that doesn’t have a human pilot on board and can be remotely controlled. Of late UAVs are being used in every sector imaginable because of their great advantages, from being able to operate in dangerous locations, to being multi-functional, reliable and cost effective.

Basic components of a drone

Source: https://oscarliang.com/quadcopter-hardware-overview/

When it comes to the basic components of a Drone, there’s

1. A frame

The frame of a drone is the basic structure on to which the other components are attached. While the frame is required to be large enough to fit all the components, it cannot be too large otherwise it will be too heavy for the motors.

2. Battery

The motors and the other electronic components of the drone receive electrical power from the battery. Lithium Polymer batteries are widely favored since they have high specific energy.

3. Motors

The motors power up the propellers and thereby provide the thrust to lift up the drone. Almost all drones use brushless DC motors since they provide excellent thrust-to-weight ratios. However, they do need complex speed controllers.

4. Propellers

There are propellers of all sizes and material and the choice is based on the pitch provided by the propeller. Pitch is the distance a propeller travels in one revolution. It is also important that the propeller is able to provide appropriate thrust for a lift off without overheating the motors.

5. The ESCs – electronic speed controller

The ESC controls the motor. PWM signals indicate the speed and the controller gives an appropriate speed output based on it.

6. The PDB – power distribution board

The power distribution board is responsible for distributing power to all the other components of the drone at the required voltages. In some cases however, the role of a PDB Is taken over by the FCs, ESCs or some other component which can be connected to the battery voltage and then output a stable voltage to the other components.

7. A flight controller

The flight controller performs many operations that help in keeping the drone in control and stable. It is like the motherboard of the drone. It receives the user commands through the Rx and then calculated the motor output by combining those with the altitude sensor readings. While some altitude sensors are built outside, many flight controllers have them integrated within. An Attitude sensor is useful to figure out the drone’s orientation in space, which are then passed over to the flight controller.

8. A radio receiver

The Radio receiver converts the radio signals it receives from an RC transmitter into control signals which are then passed on to each of the control channels that include the throttle, pitch, yaw and roll. These operate on a specified radio frequency and have minimum 4 channels.

9. Camera

The camera takes photos and videos from above and is one of the most important use of any drone. Some drones come with an inbuilt camera while others have a detachable one. The camera is selected based on the requirement like, the resolution you need, or the particular height that you need it from.

10. Transmitter

The radio signals, from the controller, are transmitted by this transmitter to the drone to issue flight commands. Similar to the receiver, the transmitter needs to have a minimum of 4 channels. The transmitter and the receiver do need to operate on a single radio frequency to be able to communicate with each other.

Movements of a Drone

A drone can make the following movements:

1. Vertical

The drone moves upward or downward with the help of the rotors. The rotor works like a fan and its spinning blades push the air down while the air pushes back. This push is the force behind the lift, so, the faster the rotors spin, the greater the lift. A drone can make three movements vertically, it can hover, climb or descend.

Source: International Journal of Scientific & Engineering Research, Volume 7, Issue 3, March-2016

By keeping the total thrust of all the four rotors equal to the gravitational force, the drone hovers. When this thrust is increased, the drone climbs and by decreasing the thrust it descends.

2. Rotation

Of the four rotors of a drone, two (opposite ones) rotate counterclockwise and the other two rotate clockwise, thereby maintaining the angular momentum at zero. To make the drone turn in either direction, one set of opposite rotors increases its spin while the other set reduces it.

Source: https://www.evansville.edu/majors/eecs/downloads/projects2016/CameronRobertsReport.pdf

3. Forwards and sideways

Source: International Journal of Scientific & Engineering Research, Volume 7, Issue 3, March-2016

Given that the drone is symmetrical, there is no difference between its forward or backward movements or its side-to-side motion. For a forward motion, the front two rotors decrease their power while the rear rotors increase their power. For a sideways movement towards the left, the two rotors on the left decrease their power and the ones on the right increase their power.

The direction of the thrust from the engine or motor can be manipulated by the UAV to control its angular velocity and altitude. This method, known as thrust vectoring, is used to provide an upward vertical thrust which facilitates a vertical takeoff and landing. The movement of the rotors give a direction to the thrust. The rotors are placed radially opposite to each other and rotate in the opposite direction to balance torque. By managing the rotation of the rotors the UAV can be made to move (up/down) vertically, forward/backward and rotate.

By increasing the rotation speed of the motors and lining their axes of rotations, a Pitching movement is achieved. Rolling happens when the speed of rotation in either motor is varied. Inclining the axis of rotation of the rotors opposite to each other causes Yawing.

Source: International Journal of Scientific & Engineering Research, Volume 7, Issue 3, March-2016

Source: International Journal of Instrumentation and Control Systems (IJICS) Vol.4, No.1, January 2014

Speed and Movement Control

A PID(proportional integral derivative) controller is implemented to maintain the craft at a desired altitude.

Standard PID Block Diagram. Source: https://www.mne.psu.edu/sommer/me445/reports/Fa14.pdf

A separate PID controller is implemented for the roll, pitch and yaw axes. At any point if the craft is unsteady, the PID detects it and counteracts it to bring it back to a steady state.

The stability of a drone is maintained by controlling and varying the speed of each of its propellers. Directional control is achieved by slowing down some rotors which in turn changes the craft’s angle enough to make it move. There are two additional systems on board a drone that ensure a steady 3-dimensional flight.

1. The Accelerometer which detects linear movement and measures it.

2. The Gyroscope which detects rotational movement, that is movement around an axis.

Both of these systems are contained within the ESC of the drone. It is the ESC which controls the speed of the drone depending on the data it receives from the flight controller.

Principle of controlling drones remotely

Given the technological advances in the past decade drones have sophisticated equipment on board which allows them to be maneuvered with ease from a remote location. An operator on the ground is able to issue flight commands to the drone via a radio communication link. This system, also known as the auto-pilot, combines the instructive signals received with the data from sensors (position and orientation) and converts them into flight commands. Today the autopilot systems can provide in-flight rerouting, way point navigation, automatic take-off and landing, controlling gimbaled cameras and also fail-safe features.

To control a drone remotely, you use a transmitter which is a hand-held controller. With just a few adjustments to this controller, you can pilot your drone and control its flight pattern, by sending signals to your drone. There are sticks on the transmitter which will allow one to manually control the propellers, change directions and adjust the trim to balance the drone. In many cases screens are used to receive the live footage from the camera on board a drone. The on-board sensors can be used to move the drone at a fixed altitude and also keep it hovering at a fixed GPS position.

Specifications of a few application drones

1. Camera Drone (Phantom 4)

– Max Speed – 20 m/s

– Weight – 1380 g (including propellers and battery)

– Max Reachable altitude – 19685 feet (6000 m)

– Supported load – 300 g (approx.)

– Battery life – Approx. 28 minutes

2. Commercial Drone (DJI MATRICE 100)

– Max Speed – 22 m/s (ATTI mode, no payload, no wind) 17 m/s (GPS mode, no payload, no wind)

– Weight – (with TB47D battery) 2355 g

– Supported load – 3600 g

– Battery life – 40 minutes

3. Agriculture Drone (AGRAS MG-1)

– Max Speed – 22 m/s

– Weight – 8.8 kg (without batteries)

– Supported load – 22.5 kg (max takeoff weight)

References:

https://www.ijedr.org/papers/IJEDR1401231.pdf

https://www.pwc.be/en/documents/20180518-drone-study.pdf

https://www.ijser.org/researchpaper/DESIGN-AND-ANALYSIS-OF-A-QUADCOPTER-USING-CATIA.pdf

http://www.dtic.mil/dtic/tr/fulltext/u2/p010321.pdf

http://www.jhuapl.edu/techdigest/td/td3102/31_02-barton.pdf

https://media.digikey.com/pdf/Data Sheets/O’Reilly_PDFs/Make_Drones_9781680451719.pdf

https://www.mne.psu.edu/sommer/me445/reports/Fa14.pdf

https://quadquestions.com/blog/2014/11/07/components-fpv-quadcopter/

http://grinddrone.com/drone-features/drone-components

http://www.ijrat.org/downloads/Vol-3/dec-2015/paper id-312201505.pdf

https://upcommons.upc.edu/bitstream/handle/2117/99817/TFM_Marti_POMES.pdf

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4 thoughts to “Basics about drones – Drone component and movement definitions”

  1. It’s so great to have so much information on drones in one place. We are definitely shopping for one, which we would like to use for photography. I absolutely love on HGTV their use of drones to view the houses and neighborhoods. Drones have so many uses, and we are excited to own one. This article gave us so much detail to help in our quest. Thank you so much!

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