An Overview of Drones and their Applications

Drones are becoming more reliable, faster, accurate, and stable, with industries developing platforms for commercial use. Autonomous capabilities offer opportunities for rescue, emergency supplies, and combat operations.

What is a drone?

Drones, also known as unmanned aerial vehicles (UAVs), are flying robots controlled remotely or autonomously using software-controlled flight plans. Initially used for military purposes, they now serve civilian roles such as intelligence gathering, anti-aircraft target practice, and weapons platforms. They work with onboard sensors and GPS.

Drones are now also used in a range of civilian roles, including the following:

  • search and rescue
  • surveillance
  • traffic monitoring
  • weather monitoring
  • firefighting
  • personal use
  • drone-based photography
  • videography
  • agriculture
  • delivery services

What is Drone Technology?

A drone is a flying robot that can be operated manually or autonomously using sensors. They have four rotors, usually a quadcopter design, which generate thrust against Earth’s gravitational force. If the thrust equals the drone’s weight, it hovers, and if it’s higher or lower than the force, it climbs or descends in the air.

Figure 1: The drone, with vertical rotor rotation, can hover, climb up, or descend depending on the force of gravity.

The thrust generated by the propellers is given by:

where D (m) is the diameter of the propeller, ρ (Kg/m3) is the density of air (1.225 kg/ m3), v(m/s) is the velocity of air at the propeller, and Δν (m/s) is the velocity of air accelerated by the propeller.

The thrust generated is vertically opposite to the direction of gravity and thus, the drone’s height can only ascend or descend in place unless it has a component of generated thrust in other directions as well. One set of diametrically opposite rotors rotates clockwise, while the other set rotates counter-clockwise. If they have the same rotational speeds, both sets cancel out the reactive yaw generated, and thus, the drone can only translate. By varying the speed of rotation of the propellers, the drone’s pitch and roll can be controlled.

Note: To move ahead in a particular direction, the drone needs to have its nose down such that the thrust has a component in the horizontal plane (see figure below).

Figure 2. Drone forward motion configuration

Physics Behind Drone Motion

A drone’s motion is influenced by the rotation of its propellers and the thrust generated against gravity and in the horizontal plane.

Figure 3. Motion characteristics defined by propeller rotation intensity. Red denotes high speed and green denotes low.

The scenarios for drone motion are:

  • If all propellers rotate fast, the drone rises up against the gravity and vice versa
  • If the rear propellers rotate faster, the nose pitches down and the drone generates a component of thrust in the forward direction for the forward motion of the drone and vice-versa
  • If the right side propellers rotate faster, they generate thrust for roll control, allowing the drone to move to the  left and vice-versa
  • If the right diagonal propellers rotate faster, they generate yaw force due to a reactive force that obtains yaw control, allowing the drone to rotate left and vice-versa

How It’s Made

Since drones generate a lot of thrust to battle strong winds, air resistance, and particles in the air, they need a strong body. They also need to absorb vibrations while being lightweight to reduce the load the drone body needs to lift against the gravitational force. Lightweight drones are also more agile and can react faster due to less inertia.

Figure 4. Side view of a drone

Most commercial drones have a lightweight carbon fiber body with a honeycomb design for the limbs that hold the rotors. The brushless motors on these drones can rotate at more than 10000 RPM and generate enough thrust to lift up the body weight. The embedded control unit, usually a microcontroller with multiple sensors, is mounted on top of the drone while the battery is placed below the controller. The battery is usually the drone’s heaviest component.

What Electronics Are in a Drone?

The most important components on a drone include a microcontroller board that runs the computations for the control of the motors, the motor speed control components, sensors for various measurements, and the drone’s lifeline, the battery.

A flight controller for a drone is a common microcontroller, but usually with high processing speed and a bare minimum of sensors onboard, needed for stabilizations. The most common commercially available flight controllers for drones are PixHawk 4, Navio2, and Beaglebone Blue capable of running the ArduPilot and PX4 autopilot software.

A 3D gyroscope is usually needed to at least have the ability to automatically stabilize the drone on a horizontal plane.

The sensor suite of a drone can include:

  • Gyroscope: provides the angular velocity of the drone and thus its orientation in the 3D world
  • Accelerometer: measures the linear acceleration but mainly used to know the direction of gravity
  • Magnetometer: detects the Earth’s magnetic field and obtains the drone’s compass direction
  • Barometer: detects the pressure and indirectly computes the height of the drone
  • GPS: obtains the coordinates (latitude and longitude) of the drone using multiple satellites

A drone also needs communication with the ground station, satellites, and networking. These components include:

  • Radio control transceiver, usually with four channels for height, pitch, roll, and yaw.
  • Bluetooth for local debugging and controller access
  • Wi-Fi/Internet for onboard connectivity with the ground station to relay real-time sensing information

The most critical component, the battery, is usually a high current source with different voltage ratings from 7.4V to ~22V depending on the type of motor used.

Drones use four propellers to move in a 3D world, with control and perception algorithms playing crucial roles. Control algorithms determine the propeller rotational speed, using a linear PID controller. Adaptive control handles unpredictable winds and atmospheric objects. Perception algorithms process sensors like accelerometer, gyroscope, and magnetometer to determine motion characteristics. Kalman filters filter sensor readings for stable results. Image processing algorithms may also run on the live camera feed for real-time analysis onboard the drone or via cloud computing. Autonomous drone navigation is a growing technological advancement that aims to eliminate the need for teleoperation in drones. Similar to commercial airplanes, autonomous drones in 3D space face less challenges due to the absence of dynamic objects at high altitudes. However, they still require intelligent sensing near ground level due to more obstacles and dynamic objects. Autonomous drones run localization, motion planning, mapping, and control algorithms similar to mobile robots. However, 3D navigation introduces its own variables, such as tolerance for inaccuracies due to noise, lower GPS accuracy, and air turbulence. Autonomous drones don’t need a large occupancy grid, but simple search algorithms like A* or Djikstra can navigate along streets or follow a projectile path.

Figure 5. Autonomous drone operations

Challenges and Future of Autonomous Drones

Autonomous drones face challenges in implementing and sustaining their capabilities due to battery power limitations, lack of quick ROI (return on investment), and insufficient control mechanisms. They struggle to handle dynamic situations without manual intervention or active weather perception, and remote communication with cloud infrastructure is challenging due to weaker mobile networks and high latency satellite communication. Despite their potential, these limitations limit commercial scalability and revenue generation. Enhancements in edge computing and control algorithms could improve autonomous drone control, but regulations and infrastructure development are necessary for large-scale commercial viability. Despite these challenges, autonomous drones have potential lifesavers in critical situations like emergency package delivery.

The Best Military Drones In The World In 2023

There are various types of drones used by armed forces, categorized into four categories: microdrones, small tactical drones, medium-sized reconnaissance drones, and large combat and surveillance drones. Microdrones, such as the Black Hornet, are used for spying over walls in Afghanistan. Small tactical drones, like the Fulmar X, are used for ISTAR (Intelligence, Surveillance, Target Acquisition, and Reconnaissance) capabilities. Medium-sized reconnaissance drones, also known as Medium Altitude Long Endurance (MALE) or High-Altitude Long Endurance (HALE) drones, are used for ISTAR and have a range of about 100 kilometers. The Northrop Grumman Global Hawk, the largest and most expensive combat and surveillance drone, has sophisticated ISTAR capabilities and flies at altitudes above commercial air traffic. Below are reported some of the most advanced drones in 2023.

#1 – MQ-9 Reaper:

The General Atomics MQ-9 Reaper is a US Air Force UAV used for offensive strikes, capable of both remotely controlled and autonomous flight operations. It operates with a ground control station and a US-based crew. The UAV is powered by a Honeywell TPE331-10GD turboprop engine producing a maximum of 900 shaft horsepower, giving it a cruise speed of about 230 mph (200 knots). The drone can carry 602 gallons of fuel and has a range of 1,150 miles. It can loiter at its flight ceiling of 50,000 feet for more than 27 hours conducting surveillance using sophisticated cameras, sensors, and radar. The Reaper can carry a payload of 3,750 pounds consisting of a variety of attack weapons.The Air Force Special Operations Command highlights its unique capability to perform strike, coordination, and reconnaissance against high-value, fleeting, and time-sensitive targets due to its significant loiter time, wide-range sensors, and precision weapons.

Length: 36 feet
Height: 12.5 feet
Wingspan: 66 feet
Weighs (empty): 4,900 pounds
Cruise speed: 230 mph (200 knots)
Range: 1,150 miles
Max Operating Altitude: 50,000 feet
Payload: 3,750 pounds

#2 – B.A.E. Systems Taranis (Under Development)

Taranis is a large-scale unmanned combat aerial vehicle (UCAV) designed to demonstrate ISTAR capabilities, including sustained surveillance, target marking, intelligence gathering, adversary deterrence, and hostile territory strikes. It features pre-programmed waypoint tracking, takeoff, and landing procedures, and AI features for objective modification. The British Ministry of Defence (MOD) unveiled the fully developed Taranis UCAV prototype in 2010, followed by high-speed taxi tests in 2013. The first test flight was conducted in August 2013, and in-flight footage was released in July 2014. The UCAV, built with a 9.1-meter wingspan, 11.35-meter barrel length, and a height of 4 meters, weighs 8,000 kg and is powered by a Rolls Royce Adour Mk. 951 turbofan engine. It has two internal weapons bays and an option for installing electro-optical and radar sensors.

Length: 37 feet
Height: 13.12 feet
Wingspan: 30 feet
Weighs (empty): 17,637 pounds
Cruise speed: Mach >1
Range: Not available
Max Operating Altitude: Not available
Payload: Not available

#3 – Bayraktar Kizilema

Baykar, a Turkish company, has developed the Bayraktar Kizilelma Fighter, an advanced unmanned aerial vehicle (UAV) with stealthy design and advanced maneuvering capabilities. The drone, powered by a Ukrainian Al-25T turbofan, can reach a cruise speed of 0.6 Mach and 500 nautical miles, and can stay airborne for five hours. It features low radar cross section, high situational awareness, and autonomous takeoff and landing. Baykar plans to develop two supersonic models using the Ukrainian Ivchenko-Progress AI-322 afterburning engines. The Kizilelma completed its inaugural flight in December 2022, and is slated for duty aboard the TCG Anadolu amphibious assault ship. Both the U.S.-built Kratos XQ-58 Valkyrie drone and Russia’s Sukhoi S-70 Okhotnik are currently in development with similar features.

Length: 48 ft 3 in
Height: 10 ft 10 in
Wingspan: 32 ft 10 in
Weighs: 8.5 tons including 1.5 tons of ordnance
Max speed: 0.9 Mach
Range: 500 nautical miles
Max Operating Altitude: 30,000 feet

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