Special Issue "Unmanned Aerial Systems 2015"

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A special issue of Aerospace (ISSN 2226-4310).

Deadline for manuscript submissions: closed (24 April 2015)

Special Issue Editor

Guest Editor
Dr. David Anderson (Website)

Aerospace Sciences Research Division, School of Engineering, University of Glasgow, Glasgow, Scotland, UK
Interests: autonomous systems, multi-agent & multi-resolution simulation, nonlinear control, operational analysis and flight dynamics & control

Special Issue Information

Dear Colleagues,

Once perceived as a niche application, Unmanned Aerial Systems (UAS) are now well established as a serious sector within the aerospace industry. The global marketplace for UAS technology has seen the sharpest growth of any aerospace sector for the past decade and this trend is predicted to continue well into the 21st century. Currently, the most prolific UAS application is military surveillance, where UAS systems have proven to be invaluable in recent conflicts. However, such uses merely scratch the surface of potential UAS applications—the real challenge facing researchers is to develop technologies to enable widespread adoption of UAS in civilian airspace, both controlled and urban.

Research in UAS requires expertise from disciplines across the academic and industrial spectra. Advances in computing and communications bandwidth for example have allowed aerodynamicists and aircraft structural engineers to explore the design space in a manner impossible even a few years ago. This is especially true in the domain of small-UAS, where a number of new platform designs from tail-sitters and stop-rotors to compound configurations have recently been proposed. Not new ideas, granted, but configurations now realisable within an unmanned aircraft setting. Unmanned systems have therefore created an opportunity for novelty, innovation and creativity in aerospace design not seen for half a century. Another key research area is in unmanned aircraft operations analysis. Here, new application areas for UAS are discovered as advances in airborne sensing, autonomy and precise platform control flow into UAS designs, yielding greater performance and capability.

The challenges in realising the true potential of UAS are not all technical. Societal factors must be addressed, particularly the negative stereotype of the ‘drone’. Such challenges may be overcome in part by developing innovative new design and analysis methods for improving and demonstrating UAS safety and reliability. We invite papers either addressing the research opportunities outlined here or in the general topic area of unmanned aerial vehicles that will make a substantive contribution to the state of the art.

Dr. David Anderson
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Aerospace is an international peer-reviewed Open Access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. For the first couple of issues the Article Processing Charge (APC) will be waived for well-prepared manuscripts. English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.

Keywords

  • autonomous systems
  • aerospace sensor technologies
  • aerodynamic technologies
  • systems engineering
  • guidance navigation and control
  • unmanned systems operational analysis/air traffic management
  • system of systems simulation
  • aerospace design and optimization
  • aerospace propulsion
  • smart materials and structures
  • composite structures and health monitoring
  • rotorcraft
  • flight safety
  • reconfigurable/fault tolerant control
  • flight dynamics
  • small unmanned aerial vehicles

Related Special Issue

Published Papers (8 papers)

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Research

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Open AccessArticle Unmanned Aerial ad Hoc Networks: Simulation-Based Evaluation of Entity Mobility Models’ Impact on Routing Performance
Aerospace 2015, 2(3), 392-422; doi:10.3390/aerospace2030392
Received: 18 February 2015 / Revised: 4 May 2015 / Accepted: 17 June 2015 / Published: 30 June 2015
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Abstract
An unmanned aerial ad hoc network (UAANET) is a special type of mobile ad hoc network (MANET). For these networks, researchers rely mostly on simulations to evaluate their proposed networking protocols. Hence, it is of great importance that the simulation environment of [...] Read more.
An unmanned aerial ad hoc network (UAANET) is a special type of mobile ad hoc network (MANET). For these networks, researchers rely mostly on simulations to evaluate their proposed networking protocols. Hence, it is of great importance that the simulation environment of a UAANET replicates as much as possible the reality of UAVs. One major component of that environment is the movement pattern of the UAVs. This means that the mobility model used in simulations has to be thoroughly understood in terms of its impact on the performance of the network. In this paper, we investigate how mobility models affect the performance of UAANET in simulations in order to come up with conclusions/recommendations that provide a benchmark for future UAANET simulations. To that end, we first propose a few metrics to evaluate the mobility models. Then, we present five random entity mobility models that allow nodes to move almost freely and independently from one another and evaluate four carefully-chosen MANET/UAANET routing protocols: ad hoc on-demand distance vector (AODV), optimized link state routing (OLSR), reactive-geographic hybrid routing (RGR) and geographic routing protocol (GRP). In addition, flooding is also evaluated. The results show a wide variation of the protocol performance over different mobility models. These performance differences can be explained by the mobility model characteristics, and we discuss these effects. The results of our analysis show that: (i) the enhanced Gauss–Markov (EGM) mobility model is best suited for UAANET; (ii) OLSR, a table-driven proactive routing protocol, and GRP, a position-based geographic protocol, are the protocols most sensitive to the change of mobility models; (iii) RGR, a reactive-geographic hybrid routing protocol, is best suited for UAANET. Full article
(This article belongs to the Special Issue Unmanned Aerial Systems 2015)
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Open AccessArticle A Comparison of Closed-Loop Performance of Multirotor Configurations Using Non-Linear Dynamic Inversion Control
Aerospace 2015, 2(2), 325-352; doi:10.3390/aerospace2020325
Received: 23 April 2015 / Revised: 18 May 2015 / Accepted: 1 June 2015 / Published: 5 June 2015
Cited by 1 | PDF Full-text (920 KB) | HTML Full-text | XML Full-text
Abstract
Multirotor is the umbrella term for the family of unmanned aircraft, which include the quadrotor, hexarotor and other vertical take-off and landing (VTOL) aircraft that employ multiple main rotors for lift and control. Development and testing of novel multirotor designs has been [...] Read more.
Multirotor is the umbrella term for the family of unmanned aircraft, which include the quadrotor, hexarotor and other vertical take-off and landing (VTOL) aircraft that employ multiple main rotors for lift and control. Development and testing of novel multirotor designs has been aided by the proliferation of 3D printing and inexpensive flight controllers and components. Different multirotor configurations exhibit specific strengths, while presenting unique challenges with regards to design and control. This article highlights the primary differences between three multirotor platforms: a quadrotor; a fully-actuated hexarotor; and an octorotor. Each platform is modelled and then controlled using non-linear dynamic inversion. The differences in dynamics, control and performance are then discussed. Full article
(This article belongs to the Special Issue Unmanned Aerial Systems 2015)
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Open AccessCommunication Development of UAS Design Based on Wideband Antenna Architecture
Aerospace 2015, 2(2), 312-324; doi:10.3390/aerospace2020312
Received: 31 January 2015 / Revised: 12 May 2015 / Accepted: 27 May 2015 / Published: 4 June 2015
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Abstract
An Unmanned Aerial System (UAS) has been developed which is based on an aerodynamically functionalized planar wideband antenna. The antenna utilizes a planar circular dipole metallization scheme. The aerodynamic structure implements a planform similar to the Nutball flier, a hobbyist flight architecture. [...] Read more.
An Unmanned Aerial System (UAS) has been developed which is based on an aerodynamically functionalized planar wideband antenna. The antenna utilizes a planar circular dipole metallization scheme. The aerodynamic structure implements a planform similar to the Nutball flier, a hobbyist flight architecture. The resulting codesign achieved a large impedance bandwidth defined by a voltage standing wave ratio (VSWR) less than 2 from 100 MHz to over 2 GHz and omnidirectional dipole-like radiation patterns at the lower frequency region and more directional patterns at higher frequencies. Full article
(This article belongs to the Special Issue Unmanned Aerial Systems 2015)
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Open AccessArticle Ornithopter Type Flapping Wings for Autonomous Micro Air Vehicles
Aerospace 2015, 2(2), 235-278; doi:10.3390/aerospace2020235
Received: 2 February 2015 / Revised: 20 April 2015 / Accepted: 4 May 2015 / Published: 13 May 2015
Cited by 2 | PDF Full-text (7899 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, an ornithopter prototype that mimics the flapping motion of bird flight is developed, and the lift and thrust generation characteristics of different wing designs are evaluated. This project focused on the spar arrangement and material used for the wings [...] Read more.
In this paper, an ornithopter prototype that mimics the flapping motion of bird flight is developed, and the lift and thrust generation characteristics of different wing designs are evaluated. This project focused on the spar arrangement and material used for the wings that could achieves improved performance. Various lift and thrust measurement techniques are explored and evaluated. Various wings of insects and birds were evaluated to understand how these natural flyers with flapping wings are able to produce sufficient lift to fly. The differences in the flapping aerodynamics were also detailed. Experiments on different wing designs and materials were conducted and a paramount wing was built for a test flight. The first prototype has a length of 46.5 cm, wing span of 88 cm, and weighs 161 g. A mechanism which produced a flapping motion was fabricated and designed to create flapping flight. The flapping flight was produced by using a single motor and a flexible and light wing structure. A force balance made of load cell was then designed to measure the thrust and lift force of the ornithopter. Three sets of wings varying flexibility were fabricated, therefore lift and thrust measurements were acquired from each different set of wings. The lift will be measured in ten cycles computing the average lift and frequency in three different speeds or frequencies (slow, medium and fast). The thrust measurement was measure likewise but in two cycles only. Several observations were made regarding the behavior of flexible flapping wings that should aid in the design of future flexible flapping wing vehicles. The wings angle or phase characteristic were analyze too and studied. The final ornithopter prototype weighs only 160 g, has a wing span of 88.5 cm, that could flap at a maximum flapping frequency of 3.869 Hz, and produce a maximum thrust and lift of about 0.719 and 0.264 N respectively. Next, we proposed resonance type flapping wing utilizes the near resonance phenomenon of a two-degree of freedom elastic system, that is, the wing is supported by the springs for flapping and feathering motions. Being oscillated close to the resonance frequency of the system, only by the torque in flapping motion, the amplitude gained is a few times higher than that of normal case. The first prototype was made from acrylic using a laser cutting machine. The wings were made up of carbon rods and kite material Ripstop. First test showed that the wings were too heavy for the mechanism to work. The third prototype was a smaller single gear crank design which was fabricated using a 3D printer. Initial test proved that the second prototype could withstand the high frequency flapping and near resonance amplitude as designed. With remote control, the third prototype was able to take off, climb, cruise and land in flapping mode successfully. Full article
(This article belongs to the Special Issue Unmanned Aerial Systems 2015)
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Open AccessArticle Trajectory Management of the Unmanned Aircraft System (UAS) in Emergency Situation
Aerospace 2015, 2(2), 222-234; doi:10.3390/aerospace2020222
Received: 1 February 2015 / Revised: 13 March 2015 / Accepted: 18 March 2015 / Published: 4 May 2015
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Abstract
Unmanned aircraft must be characterized by a level of safety, similar to that of manned aircraft, when performing flights over densely populated areas. Dangerous situations or emergencies are frequently connected with the necessity to change the profiles and parameters of a flight [...] Read more.
Unmanned aircraft must be characterized by a level of safety, similar to that of manned aircraft, when performing flights over densely populated areas. Dangerous situations or emergencies are frequently connected with the necessity to change the profiles and parameters of a flight as well as the flight plans. The aim of this work is to present the methods used to determine an Unmanned Aircraft System’s (UAS) flight profile after a dangerous situation or emergency occurs. The analysis was limited to the possibility of an engine system emergency and further flight continuing along a trajectory of which the shape depends on the type of the emergency. The suggested method also enables the determination of an optimal flying trajectory, based on the territory of a special protection zone (for example, large populated areas), in the case of an emergency that would disable continuation of the performed task. The method used in this work allows researchers, in a simplified way, to solve a variation task using the Ritz–Galerkin method, consisting of an approximate solution of the boundary value problem to determine the optimal flight path. The worked out method can become an element of the on-board system supporting UAS flight control. Full article
(This article belongs to the Special Issue Unmanned Aerial Systems 2015)
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Open AccessArticle Development of Flight Path Planning for Multirotor Aerial Vehicles
Aerospace 2015, 2(2), 171-188; doi:10.3390/aerospace2020171
Received: 21 November 2014 / Revised: 11 March 2015 / Accepted: 24 March 2015 / Published: 27 April 2015
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Abstract
This study addresses the flight-path planning problem for multirotor aerial vehicles (AVs). We consider the specific features and requirements of real-time flight-path planning and develop a rapidly-exploring random tree (RRT) algorithm to determine a preliminary flight path in three-dimensional space. Since the [...] Read more.
This study addresses the flight-path planning problem for multirotor aerial vehicles (AVs). We consider the specific features and requirements of real-time flight-path planning and develop a rapidly-exploring random tree (RRT) algorithm to determine a preliminary flight path in three-dimensional space. Since the path obtained by the RRT may not be optimal due to the existence of redundant waypoints. To reduce the cost of energy during AV’s flight, the excessive waypoints need to be refined. We revise the A-star algorithm by adopting the heading of the AV as the key indices while calculating the cost. Bezier curves are finally proposed to smooth the flight path, making it applicable for real-world flight. Full article
(This article belongs to the Special Issue Unmanned Aerial Systems 2015)
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Open AccessArticle Path Planning Using Concatenated Analytically-Defined Trajectories for Quadrotor UAVs
Aerospace 2015, 2(2), 155-170; doi:10.3390/aerospace2020155
Received: 23 February 2015 / Revised: 26 March 2015 / Accepted: 16 April 2015 / Published: 21 April 2015
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Abstract
This paper presents a semi-analytical trajectory planning method for quadrotor UAVs. These trajectories are analytically defined, are constant in speed and sub-optimal with respect to a weighted quadratic cost function of the translational and angular velocities. A technique for concatenating the trajectories [...] Read more.
This paper presents a semi-analytical trajectory planning method for quadrotor UAVs. These trajectories are analytically defined, are constant in speed and sub-optimal with respect to a weighted quadratic cost function of the translational and angular velocities. A technique for concatenating the trajectories into multi-segment paths is demonstrated. These paths are smooth to the first derivative of the translational position and pass through defined waypoints. A method for detecting potential collisions by discretizing the path into a coarse mesh before using a numerical optimiser to determine the point of the path closest to the obstacle is presented. This hybrid method reduces the computation time when compared to discretizing the trajectory into a fine mesh and calculating the minimum distance. A tracking controller is defined and used to show that the paths are dynamically feasible and the typical magnitudes of the controller inputs required to fly them. Full article
(This article belongs to the Special Issue Unmanned Aerial Systems 2015)
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Review

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Open AccessReview Unmanned Aerial Systems (UAS) Research Opportunities
Aerospace 2015, 2(2), 189-202; doi:10.3390/aerospace2020189
Received: 30 January 2015 / Revised: 15 April 2015 / Accepted: 20 April 2015 / Published: 27 April 2015
Cited by 1 | PDF Full-text (140 KB) | HTML Full-text | XML Full-text
Abstract
The aerospace community is planning for growth in Unmanned Aerial Systems (UAS) funding and research opportunities. The premise that UAS will revolutionize aerospace appears to be unfolding based on current trends. There is also an anticipation of an increasing number of new [...] Read more.
The aerospace community is planning for growth in Unmanned Aerial Systems (UAS) funding and research opportunities. The premise that UAS will revolutionize aerospace appears to be unfolding based on current trends. There is also an anticipation of an increasing number of new platforms and research investment, which is likely but must be analysed carefully to determine where the opportunities lie. This paper draws on the state of technology, history and systems engineering. We explore what aspects of UAS will be the result of aerospace science advances and what aspects will be incremental engineering and systems integration. It becomes apparent that, for academia, the largest opportunities may exist in small and micro UAS domain due to the novelty of aerospace engineering on a small scale. Full article
(This article belongs to the Special Issue Unmanned Aerial Systems 2015)
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