Understanding Components of UAV for Research

July 7, 2023

In this article, I aim to provide a comprehensive overview of the components used in drones while drawing from my personal experiences during my time in graduate school. As a student pursuing my studie, I had the opportunity to delve into the fascinating world of drones and explore their various applications. Through this article, I hope to share my knowledge and insights gained from my research and experiences, shedding light on the essential components that make up these remarkable aerial vehicles. Whether you are a hobbyist or a professional in the field, understanding the intricacies of drone components is crucial for successful operation and exploration of this exciting technology.

Fig. A common parts in a drone for aerial robotics research

1. Control system

The control system of a drone is responsible for managing its flight and navigation. It consists of two primary components: the onboard computer and the flight control unit (FCU).

Onboard computer

This computer is where your research algorithm is running. The onboard computer handles perception and planning, enabling the drone to process sensory data and make decisions accordingly. In many cases, the OS is linux, and many researchers have used the following products:

The spec of the computer really depends on your scenario: how your testing algorithm is complex, and whether your algorithm requires GPU and cuda. This decision directly affects the payload of your drone.

Pixhawk

Fig. Pixhawk manual

The Pixhawk is a popular FCU used in many drone systems, providing stability and reliable flight control. The FCU is responsible for:

  • interfacing the onboard computer and all the hardware components such as propulsion and sensors inside Pixhawk.
  • Output PWM signal to control motors.
  • Communication such MavLink and RC channels.
  • Low-level controllers and filtering algorithm in its Firmware.
  • Log and analysis using Flight review.
  • Mission planning receiving.
  • Flight mode changes.

For more information, refer to Pixhawk offical site (opens in a new tab) and its Firmware PX4 (opens in a new tab).

2. Sensors & Communication

Fig. Drone with velodyne (I built myself)

To operate effectively, drones rely on various sensors and communication devices. These components enable the drone to gather information about its surroundings and communicate with the operator or other devices. Key components include:

Pixhawk

As mentioned earlier, the Pixhawk serves as both a flight control unit and a sensor hub, collecting data from different sensors and facilitating flight control. Two representative sensors of Pixhawk are

  • Inertial Measurement Unit (IMU): The Pixhawk 4 usually includes an IMU that consists of an accelerometer, gyroscope, and magnetometer. These sensors provide essential data for stabilizing the drone, measuring its orientation, and compensating for external forces.
  • Barometer: A barometer sensor measures atmospheric pressure, allowing the Pixhawk 4 to estimate altitude and vertical speed.
  • Default compass: A compass sensor, such as a magnetometer, is used to determine the drone's heading and orientation relative to Earth's magnetic field. It helps with navigation and stabilization.

It's worth noting that different Pixhawk 4 configurations or variations may include additional or slightly different sensors. It's always recommended to refer to the specific product documentation or manufacturer's website for the precise details and specifications of the Pixhawk 4 you are using.

Vision Sensor

Drones often incorporate vision sensors such as cameras or LiDAR (Light Detection and Ranging) systems. These sensors provide vital visual data, enabling tasks such as object detection, terrain mapping, and obstacle avoidance. Some of frequently used sensors include:

You might need multiple sensoers, in that case, you need reliable extrinsic calibration using libraries such as Kalibr (opens in a new tab).

GPS/Compass

Global Positioning System (GPS) modules provide precise positioning information, allowing drones to navigate accurately. Compass sensors help drones maintain their heading and orientation.

Telemetry

Telemetry systems establish a wireless link between the drone and the ground station, transmitting real-time flight data, status updates, and control commands.

RC Receiver

In cases where manual control is necessary, drones utilize a radio control (RC) receiver to receive commands from a remote controller.

3. Propulsion

The propulsion system of a drone is responsible for generating the necessary thrust to achieve and maintain flight. When selecting propulsion components, factors such as payload capacity and flight time must be considered. Providers like iFlight (opens in a new tab) and T motor (opens in a new tab) offer bundled products comprising ESCs (Electronic Speed Controllers), motors, and propellers, known for their stability and compatibility.

ESC

Electronic Speed Controllers regulate the speed and direction of the motors, ensuring precise control over the drone's movement. When I was in graduate school, I used to leverage the belows:

BLDC Motor

Brushless Direct Current (BLDC) motors are commonly used in drones due to their high efficiency, reliability, and compact design.

Propeller

Propellers convert rotational motion from the motors into thrust, propelling the drone through the air. The choice of propeller depends on factors such as payload, flight characteristics, and motor specifications.

Propeller Guard

Propeller guards are optional accessories that protect the propellers from damage during flight and provide an added layer of safety.

Lipo Battery

While not explicitly mentioned in the abstract, it's worth noting that drones often utilize Lithium Polymer (LiPo) batteries due to their high energy density and lightweight properties.

4. Body

Fig. The parts I designed with solidworks (used for velodyne drone)

The body or frame of a drone serves as its structural backbone, providing stability and protection to the internal components. Factors to consider when selecting a drone body include:

Commercial Frame

Commercially available drone frames offer a reliable and tested solution. They come in various sizes and configurations to accommodate different payloads and flight requirements. Some of very famous frames include:

Landing Gear

Landing gear plays a crucial role in protecting the drone's sensitive components during takeoff and landing. Choosing appropriate landing gear is essential to prevent vibrations that can affect flight performance.

Custom Connectors

In many cases, custom connectors are required to mount and connect the various components introduced earlier. The design and production of these connectors should be considered in the overall schedule, as it may take several weeks to complete.

What's next?

I will write how I configured software stack to operate my drone with the components !