Multi-Rotor Drones: Types, Applications, and Challenges

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MULTI -ROTOR UAVS
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TABLE OF CONTENTS
INTRODUCTION.......................................................................................................... 3
TYPES OF MULTI-ROTORS.......................................................................................... 5
APPLICATIONS OF DRONES........................................................................................ 6
Drones application in agriculture................................................................................... 6
Application of drones on the delivery of goods................................................................10
Drones in fisheries, forestry and protection of wildlife......................................................12
Drones in defense...................................................................................................... 12
Drones in Civil applications......................................................................................... 12
Drones application in search and rescue........................................................................13
Application of drones in remote sensing.........................................................................14
Drones application in the inspection of construction and infrastructure...............................15
Application of drones to monitor the traffic of roads........................................................16
Application of drones to provide wireless coverage..........................................................17
Application of drones in the management of karst resources features..................................18
SECURITY ISSUES AND CHALLENGES POSED BY DRONES.........................................18
DRONE BIOMETRICS AND PILOT IDENTIFICATION...................................................21
MACHINE LEARNING TECHNIQUES..........................................................................23
ARCHITECTURE AND COMPONENTS OF DRONES.....................................................24
CHALLENGES FACING DRONES................................................................................ 28
CONCLUSION............................................................................................................ 29
REFERENCES............................................................................................................ 31

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INTRODUCTION
According to U.S Federal Aviation Administration, Unmanned Aerial Vehicle is defined as an
aircraft flown without a pilot on board. They were introduced first by the American military
usage in the 1950s. 1933, the royal navy applied drones for gunnery practices and later there
were advent and integration of advanced navigation sensors and UAV became the integral parts
of the armed forces. The efforts in transport, combat and surveillance and recent years, UAVs
have gained popularity in the usage. Control technology and improvement of sensors have
enabled UAVs to gain prominence worldwide on non-military applications. This is mostly true
for multi-rotor units' because of their cost-effectiveness and flexibility because of their small
sizes. Their prominence is promoted by the capabilities of remote control the can reduce the
exposure of the aircraft operators to dangerous environments for many forms of documentation
and investigations.
The common application includes search and rescue, agriculture, an inspection of infrastructure,
conservation of wildlife transportation and civil engineering. UAV is an integral part of the
Unmanned Aerial system which incorporates UAV, ground control station and the
communication link. It overcomes the problems of terrestrial systems such as speed, accessibility
and reliability. They can give cloud-free and images of high resolutions to serve the commercial
uses in agriculture, monitoring and mining [1].
in the recent years, the technologies that support drones has significantly improved especially
system direction and hardware design and the software has been dominated by the community of
open sources, where more research are conducted in the system of autopilot. This research paper
has described multi-rotor UAVs, their applications and importance of each application, security

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issues of drones and how they pose challenges, machine learning techniques, biometric and pilot
identification, drone architecture and its components stating their functions [2].
Figure 1: Mission categories of Drones
Figure 2: Uses of Drones

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TYPES OF MULTI-ROTORS
Bi- Copters: this has two motors and can be moved to by servos. It is cheaper compared to other
multi motors since it has only two motors. It is less stable and it not easy to turn. It has lower
lifting power since it possesses only two rotors. If one rotor is damaged the copter can't move
and hence the biggest challenge [3].
Tri-copter: it is a less expensive example of multirotor since it has few motors. They need servo
motors which are cost-effective compared to brushless motors. It as the widest angle of 120
degrees between the two front motors hence easy to conduct photography and videography in air.
It has three T shaped motors arranged in Y shape of 120 degrees. They are stable than bi-copters
but unstable compared to others. The copter will not move further if one rotor is damaged or fail.
Quadcopters: it is propelled and lifted by four motors mounted on four frames. The arms are 90
degrees apart. There are counter and clockwise propellers fitted on motors to produce opposite
force for balancing. It is simplest, stable and easy in terms of understanding [4].
Penta- copters: they possess five motors and they are lacking more information since it is not
popular because of underlying issues. They are not common and are known as the worst multi-
rotor design. It has a wide-angle that enables the propellers to stay away from the camera as
possible. It also has wide angles I the front arms hence easy to shoot aerial pictures and videos
without propellers making it into the frames. They also have more power of lifting, unlike other
copters.
Hexa-copters: they differ from the helicopters applying rotors with fixed pitch hence as the
blades rotate and move their pitch rotor don't vary. They have 6 mounted fitted on the frames

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making the angle of 120 degrees from everyone. They have the same mechanics of flight but
have more lifting power compared to the quadcopter.
Octa-copters: they have 8 rotors consisting of four clockwise and anticlockwise propellers. It is
the advanced hexacopter with more lifting power. If two or fewer motors fail or get damaged, it
can be supported by another remaining motor. It is the most reliable multi-rotor UAVs [5].
APPLICATIONS OF DRONES
Since the drones provide supremacy compared to conventional remote sensing and their
importance rely upon terms of consumption of less power, fewer risks posed to human and
health, easy way of collecting data, high ultra-spatial resolutions give them perfect choice for
mapping and surveying [6].
Drones application in agriculture
The main aim of agriculture is to apply the minimum amount of input at the correct time and
place to make the best products. Common activities of farming are the collection of data and
variability mapping of agricultural fields and lands, analysis of data making decisions of farm
management on the results obtained from the analysis and finally controlled applications
including spraying fertilizers and pesticides. Agriculture has adopted widely the art of remote
sensing using the non –modern satellites and Arial platforms. The ability of satellites to map and
monitor vegetation is based upon the temporal, spatial and spectral resolutions of sensors such as
MODIS, AVHRR and OLI. In 2013, there was the launch of OLI onboard Landsat 8 with 30m of
temporal resolution gave images with 30 to 15m spatial resolution of panchromatic in the bands
ranging between 435nm to 12510nm. More research work has been conducted in the farming
areas using satellites based remote sensing and the results were promising [7].

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The research work included yield variation caused by climate change, mapping areas under
irrigation, crop yield estimation, management of crop water stress, monitoring and classification
of forest cover. These have impacted positively in terms of analysis of productivity and
management of farming but limited to cloud cover and coarse resolutions. Later on, UAS
introduced a cost-effective and low attitude alternatives to give images of high resolutions. UAV
can be used to estimate nutrients and above-ground crops by capturing the images of agricultural
lands using the helicopter-based unmanned aerial vehicle in various bands with specified
resolutions. The drones can also be applied along with thermal and multispectral sensors to
delineate the spatial distribution and variability of water within the commercial vineyard
sustained by rain [8].
UAVs can be applied for the field of crops at lower densities with high precision at a lower cost
compared to the traditional aircraft. Applying UAVs for managing crops give real-time data
about the exact location. UAVs and give images of high resolutions for a crop to help in the
process of management such as weed management, diseases detection, variability and
minimizing the number of herbicides. Examples are [9]:
Scheduling irrigation: there are specific sectors that need monitoring before determining the
irrigation need; availability of water in the soil, crop water need which is known as the water
required by crops for optimum growth, amount of rainfall and efficiency in the systems of
irrigation. These factors can be measured by using UAVs to measure moisture in the soil,
evapotranspiration and temperature of plants. Partial distribution of moisture in the soil surface
can be measured using the multispectral image of high resolutions taken by UAVs combined
with ground sampling [10].

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Detecting diseases of crops: it is estimated that crop losses resulted from the plant diseases result
in billions of money being lost. UAVs can be used for thermal remote sensing to monitor the
temporal and spatial patterns of crop diseases during the development stages of diseases hence
farmers can minimize loss of crops. Thermal images can be taken in the air using UAVs to detect
the development of fungus in the soil [11].
Soil mapping: some of the characteristics of soil such as soil texture can indicate the quality of
soil which affects the productivity of crops. UAVs thermal images can be used to quantify
texture of soil at the regional scales by measuring the temperature of the land surface under the
same climatic conditions [12].
Tillage and cover mapping; the residue of crops is important in the conservation of soil by giving
a protective portion on agricultural fields that protect soil from water and wind. Accurate
measurement of crop residues is important for proper implementation of management and
conservation tillage activities. Thermal images taken in the air can explain the variability of the
amount of crop residue cover compared to applying near IR and visible images [13].
Mapping field: system of tile drainage removes extra water from the field and hence provides
both economic and ecological benefits. Perfect monitoring of tile drains can assist natural
resources managers and farmers to mitigate adverse economic and environmental impacts.
Through assessing differences of temperatures in the field, thermal UAVs images can give more
opportunities in the mapping of field tiles [14].
Mapping maturity of crops: UAVs can be the technology that monitors the maturity of crops for
determination of harvesting time especially when the whole area cannot be harvested in the
available time.