Article
Design and Implementation of Morphed Multi-Rotor Vehicles
with Real-Time Obstacle Detection and Sensing System
Aleligne Yohannes Shiferaw
1
, Balasubramanian Esakki
1,
* , Tamilarasan Pari
2
, Elangovan Elumalai
3
,
Saleh Mobayen
4,
* and Andrzej Bartoszewicz
5
Citation: Shiferaw, A.Y.; Esakki, B.;
Pari, T.; Elumalai, E.; Mobayen, S.;
Bartoszewicz, A. Design and
Implementation of Morphed
Multi-Rotor Vehicles with Real-Time
Obstacle Detection and Sensing
System. Sensors 2021, 21, 6192.
https://doi.org/10.3390/s21186192
Academic Editor:
George Nikolakopoulos
Received: 9 August 2021
Accepted: 13 September 2021
Published: 15 September 2021
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Attribution (CC BY) license (https://
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4.0/).
1
Department of Mechanical Engineering, Centre for Autonomous System Research, Vel Tech Rangarajan Dr
Sagunthala R & D Institute of Science and Technology, Avadi, Chennai 600062, India;
yohannesaleligne@gmail.com
2
Department of Aeronautical Engineering, Centre for Autonomous System Research, Vel Tech Rangarajan Dr
Sagunthala R & D Institute of Science and Technology, Avadi, Chennai 600062, India;
tamilarasan1837@gmail.com
3
Department of Electronics and Communication Engineering, Centre for Autonomous System Research, Vel
Tech Rangarajan Dr Sagunthala R & D Institute of Science and Technology, Avadi, Chennai 600062, India;
elangovan27sri@gmail.com
4
Future Technology Research Center, National Yunlin University of Science and Technology, 123 University
Road, Section 3, Douliou 64002, Taiwan
5
Institute of Automatic Control, Lodz University of Technology, 18/22 Stefanowskiego St., 90-924 Lodz,
Poland; andrzej.bartoszewicz@p.lodz.pl
* Correspondence: balasubramaniane@veltech.edu.in (B.E.); mobayens@yuntech.edu.tw (S.M.)
Abstract:
Multirotor unmanned aerial vehicles (MUAVs) are becoming more prominent for diverse
real-world applications due to their inherent hovering ability, swift manoeuvring and vertical take-off
landing capabilities. Nonetheless, to be entirely applicable for various obstacle prone environments,
the conventional MUAVs may not be able to change their configuration depending on the available
space and perform designated missions. It necessitates the morphing phenomenon of MUAVS,
wherein it can alter their geometric structure autonomously. This article presents the development
of a morphed MUAV based on a simple rotary actuation mechanism capable of driving each arm’s
smoothly and satisfying the necessary reduction in workspace volume to navigate in the obstacle
prone regions. The mathematical modelling for the folding mechanism was formulated, and corre-
sponding kinematic analysis was performed to understand the synchronous motion characteristics
of the arms during the folding of arms. Experiments were conducted by precisely actuating the servo
motors based on the proximity ultrasonic sensor data to avoid the obstacle for achieving effective
morphing of MUAV. The flight tests were conducted to estimate the endurance and attain a change
in morphology of MUAV from “X-Configuration” to “H-Configuration” with the four arms actuated
synchronously without time delay.
Keywords:
foldable UAV; morphology; kinematics; synchronous motion; obstacle detection; ultra-
sonic sensor
1. Introduction
In recent times, MUAVs have been widely used in multifaceted environments and
applications, including agriculture, transportation, security, entertainment, search and
rescue missions, as well as for unmanned missions in water quality monitoring and
assessment using (Internet of things) IoT based Sensors [
1
–
4
]. The inherent characteristics
of MUAVs, such as swift manoeuvrability and hovering abilities, are added advantages for
efficient navigation to inspect collapsed buildings and even examine underground tunnels.
The medium and larger-sized MUAVs have a greater load-bearing capacity and can perform
various designated tasks effectively. However, their portability and manoeuvrability have
become a severe issue. Thus, to be entirely applicable for various applications, having a low
Sensors 2021, 21, 6192. https://doi.org/10.3390/s21186192 https://www.mdpi.com/journal/sensors
