Article
Design, Analysis, and Testing of a Hybrid VTOL Tilt-Rotor
UAV for Increased Endurance
Siddhant Panigrahi
1
, Yenugu Siva Sai Krishna
2
and Asokan Thondiyath
1,
*
Citation: Panigrahi, S.; Krishna,
Y.S.S.; Thondiyath, A. Design,
Analysis, and Testing of a Hybrid
VTOL Tilt-Rotor UAV for Increased
Endurance. Sensors 2021, 21, 5987.
https://doi.org/10.3390/s21185987
Academic Editor:
George Nikolakopoulos
Received: 27 June 2021
Accepted: 18 August 2021
Published: 07 September 2021
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4.0/).
1
Robotics Laboratory, Department of Engineering Design, Indian Institute of Technology Madras,
Chennai 600036, India; ed18d701@smail.iitm.ac.in
2
Department of Aerospace Engineering, Indian Institute of Technology Madras, Chennai 600036, India;
ae16b115@smail.iitm.ac.in
* Correspondence: asok@iitm.ac.in
Abstract:
Unmanned Aerial Vehicles (UAVs) have slowly but steadily emerged as a research and
commercial hotspot because of their widespread applications. Due to their agility, compact size, and
ability to integrate multiple sensors, they are mostly sought for applications that require supplement-
ing human effort in risky and monotonous missions. Despite all of these advantages, rotorcrafts, in
general, are limited by their endurance and power-intensive flight requirements, which consequently
affect the time of flight and operational range. On the other hand, fixed-wing aircrafts have an
extended range, as the entire thrust force is along the direction of motion and are inherently more
stable but are limited by their takeoff and landing strip requirements. One of the potential solutions
to increase the endurance of VTOL rotorcrafts (Vertical Take-Off and Landing Vehicles) was to exploit
the thrust vectoring ability of the individual actuators in multi-rotors, which would enable take-off
and hovering as a VTOL vehicle and flight as a fixed-wing aircraft. The primary aim of this paper is
to lay out the overall design process of a Hybrid VTOL tilt-rotor UAV from the initial conceptual
sketch to the final fabricated prototype. The novelty of the design lies in achieving thrust vectoring
capabilities in a fixed-wing platform with minimum actuation and no additional control complexity.
This paper presents novel bi-copter that has been designed to perform as a hybrid configuration in
both VTOL and fixed wing conditions with minimum actuators in comparison to existing designs.
The unified dynamic modelling along with the approximation of multiple aerodynamic coefficients
by numerical simulations is also presented. The overall conceptual design, dynamic modeling, com-
putational simulation, and experimental analysis of the novel hybrid fixed-wing bi-copter with thrust
vectoring capabilities aiming to substantially increase the flight range and endurance compared to
the conventional aircraft rotorcraft configurations are presented.
Keywords: UAV; VTOL; Bi-copter; PID
1. Introduction
Aerial flight has been a topic of sheer interest from time immemorial since the
Wright brothers built the first manned aircraft in 1903. However, recent developments
in lightweight composite materials, compact and reliable electronics, and robust flight
controller algorithms have made the technology accessible to the research, educational, and
developer communities. UAVs have created a tremendous impact on society by adding a
new perspective to the way that we look at things, as they has revolutionized agriculture
and farming by the application of NDVI (Normalized Difference Vegetation Index) imaging
and pest control [
1
], remote inspection, and strategic disaster management operations
through the application of image processing and object detection [
2
], mapping, surveil-
lance, law enforcement, social distancing, and reconnaissance operations by providing
aerial footage of the region of interest for target acquisition [3].
With the applications of UAVs catering to such widespread areas, there has been
an undeniable demand for hybrid UAV configurations. UAVs have been categorically
Sensors 2021, 21, 5987. https://doi.org/10.3390/s21185987 https://www.mdpi.com/journal/sensors
