IEEE Consumer Electronics Magazine - November/December 2021 - 12

Unmanned Aerial Vehicles
Table 1. Comparisons of different UAV body materials.
Material
Foam
Plastic
Wood
Carbon Fibers
G-10
Aluminum
0.06 - 1.96
0.17
1.75
1.80
2.70
46 - 60
2 - 88
7 - 64
Density (g/cm) Tensile Strength (MPa)
0.05
Pros
Easy to shape, Flexible
Cons
Weak
Lightweight, Widely available Varying strength
2,000 - 5,600
262 - 310
276 - 310
Very lightweight, Strong
Strong
Expensive
Heavy
Inertial Measurement Unit: An inertial measurement
unit (IMU) is an electronic device that
provides a measurement of UAV's attitude, specific
force (i.e., nongravitational force per unit
mass also called g-force), angular velocity, orientation,
and position information. Most of the
IMUs consist of a combination of the following
sensors.
Accelerometer: Measures the linear acceleration
ax, ay, az on the three axes of the body x,
y, z.
Gyroscope: Measures the angular change rate
p, q, r on the three axes of the body x, y, z.
Magnetometer: Determines the heading of a
UAV by measuring the earth's magnetic field.
Barometer: Determines the altitude of a UAV
by measuring the earth's atmospheric
pressure.
Since each one of the IMU components works
on three axes, by combining the three components
(accelerometer, gyroscope, magnetometer)
the flight controller can measure the UAV's
speed, orientation, and direction along nine
axes. Currently, most professional and military
IMUs tend to incorporate redundant IMU sensors.
The advantage of this redundancy is to get
the most accurate data from the sensors. Furthermore,
redundancy is helpful in case of a sensor
failure, where the redundant components
provide a level of fault tolerance.
Global Positioning System: The global positioning
system (GPS) chip is used to get the position
of the UAV from multiple satellites, which is
how the UAV gets a navigation system. The GPS
chip together with the IMU constitutes the
Figure 2. Main components of a UAV.
navigation system of a UAV, which measures the
speed, positioning, and heading of the UAV. The
GPS chip can either be a separate receiver chip
or part of the flight controller.
Visual, Ultrasonic, and Infrared Sensors: UAVs
often incorporate visual, ultrasonic, and infrared
sensors to detect obstacles and avoid collisions
by measuring the relative distances to the
objects in the path of the UAV or surrounding it.
2. FLIGHT CONTROLLER: The flight controller is
the brain of the UAV. The flight controller is the
hardware and the firmware that processes all
the information that is collected from the IMU,
GPS, and other sensors. The flight controller
also controls the payload on the UAV (such as
cameras and other sensors). The flight controller
can be fully autonomous or just provide
some level of navigation assistance in the autopilot
mode using the sensed data from the IMUs
and other sensors to control the UAV. Some of
the flight controllers are capable of being programmed
to set a home point from where the
UAVs can be launched and land back automatically.
The flight controllers provide the ability to
fly a UAV through preloaded flight paths utilizing
waypoints. Waypoints are a set of predefined
12
IEEE Consumer Electronics Magazine
IEEE Consumer Electronics Magazine - November/December 2021

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