Assessment of air quality has been traditionally conducted by ground based monitoring, and more recently by manned aircrafts and satellites. However, performing fast, comprehensive data collection near pollution sources is not always feasible due to the complexity of sites, moving sources or physical barriers. Small Unmanned Aerial Vehicles (UAVs) equipped with different sensors have been introduced for in-situ air quality monitoring, as they can offer new approaches and research opportunities in air pollution and emission monitoring, as well as for studying atmospheric trends, such as climate change, while ensuring urban and industrial air safety. The aims of this review were to: (1) compile information on the use of UAVs for air quality studies; and (2) assess their benefits and range of applications. An extensive literature review was conducted using three bibliographic databases (Scopus, Web of Knowledge, Google Scholar) and a total of 60 papers was found. This relatively small number of papers implies that the field is still in its early stages of development. We concluded that, while the potential of UAVs for air quality research has been established, several challenges still need to be addressed, including: the flight endurance, payload capacity, sensor dimensions/accuracy, and sensitivity. However, the challenges are not simply technological, in fact, policy and regulations, which differ between countries, represent the greatest challenge to facilitating the wider use of UAVs in atmospheric research.

An Overview of Small Unmanned Aerial Vehicles for Air Quality Measurements: Present Applications and Future Prospectives

A survey of hybrid Unmanned Aerial Vehicles

This article presents a review on the platform design, dynamic modeling and control of hybrid Unmanned Aerial Vehicles (UAVs). For now, miniature UAVs which have experienced a tremendous development are dominated by two main types, i.e., fixed-wing UAV and Vertical Take-Off and Landing (VTOL) UAV, each of which, however, has its own inherent limitations on such as flexibility, payload, axnd endurance. Enhanced popularity and interest are recently gained by a newer type of UAVs, named hybrid UAV that integrates the beneficial features of both conventional ones. In this paper, a technical overview of the recent advances of the hybrid UAV is presented. More specifically, the hybrid UAV's platform design together with the associated technical details and features are introduced first. Next, the work on hybrid UAV's flight dynamics modeling is then categorized and explained. As for the flight control system design for the hybrid UAV, several flight control strategies implemented are discussed and compared in terms of theory, linearity and implementation.

A review on the platform design, dynamic modeling and control of hybrid UAVs

Thermal infrared imaging of geothermal environments and by an unmanned aerial vehicle (UAV): A case study of the Wairakei – Tauhara geothermal field, Taupo, New Zealand

Additive Manufacturing (AM) is a game changing production technology for aerospace applications. Fused deposition modeling is one of the most widely used AM technologies and recently has gained much attention in the advancement of many products. This paper introduces an extensive review of fused deposition modeling and its application in the development of high performance unmanned aerial vehicles. The process methodology, materials, post processing, and properties of its products are discussed in details. Successful examples of using this technology for making functional, lightweight, and high endurance unmanned aerial vehicles are also highlighted. In addition, major opportunities, limitations, and outlook of fused deposition modeling are also explored. The paper shows that the emerge of fused deposition modeling as a robust technique for unmanned aerial vehicles represents a good opportunity to produce compact, strong, lightweight structures, and functional parts with embedded electronic.

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Fused Deposition Modeling for Unmanned Aerial Vehicles (UAVs): A Review

For the last four decades Unmanned Air Vehicles (UAVs) have been extensively used for military operations that include tracking, surveillance, active engagement with weapons and airborne data acquisition. UAVs are also in demand commercially due to their advantages in comparison to manned vehicles. These advantages include lower manufacturing and operating costs, flexibility in configuration depending on customer request and not risking the pilot on demanding missions. Even though civilian UAVs currently constitute 3 % of the UAV market, it is estimated that their numbers will reach up to 10 % of the UAV market within the next 5 years. Most of the civilian UAV applications require UAVs that are capable of doing a wide range of different and complementary operations within a composite mission. These operations include taking off and landing from limited runway space, while traversing the operation region in considerable cruise speed for mobile tracking applications. This is in addition to being able traverse in low cruise speeds or being able to hover for stationary measurement and tracking. All of these complementary and but different operational capabilities point to a hybrid unmanned vehicle concept, namely the Vertical Take-Off and Landing (VTOL) UAVs. In addition, the desired UAV system needs to be cost-efficient while providing easy payload conversion for different civilian applications. In this paper, we review the preliminary design process of such a capable civilian UAV system, namely the TURAC VTOL UAV. TURAC UAV is aimed to have both vertical take-off and landing and Conventional Take-off and Landing (CTOL) capability. TURAC interchangeable payload pod and detachable wing (with potential different size variants) provides capability to perform different mission types, including long endurance and high cruise speed operations. In addition, the TURAC concept is to have two different variants. The TURAC A variant is an eco-friendly and low-noise fully electrical platform which includes 2 tilt electric motors in the front, and a fixed electric motor and ducted fan in the rear, where as the TURAC B variant is envisioned to use high energy density fuel cells for extended hovering time. In this paper, we provide the TURAC UAV's iterative design and trade-off studies which also include detailed aerodynamic and structural configuration analysis. For the aerodynamic analysis, an in-house software including graphical user interface has been developed to calculate the aerodynamic forces and moments by using the Vortex Lattice Method (VLM). Computational Fluid Dynamics (CFD) studies are performed to determine the aerodynamic effects for various configurations For structural analysis, a Finite Element Model (FEM) of the TURAC has been prepared and its modal analysis is carried out. Maximum displacements and maximal principal stresses are calculated and used for streamlining a weight efficient fuselage design. Prototypes have been built to show success of the design at both hover and forward flight regime. In this paper, we also provide the flight management and autopilot architecture of the TURAC. The testing of the controller performance has been initiated with the prototype of TURAC. Current work focuses on the building of the full fight test prototype of the TURAC UAV and aerodynamic modeling of the transition flight.

Design of a Commercial Hybrid VTOL UAV System

This paper describes a complete six-degree-of-freedom nonlinear mathematical model of a tilt rotor unmanned aerial vehicle (UAV). The model is specifically tailored for the design of a hover to forward flight and forward flight to hover transition control system. In that respect, the model includes the aerodynamic effect of propeller-induced airstream which is a function of cruise speed, tilt angle and angle of attack. The cross-section area and output velocity of the propeller-induced airstream are calculated with momentum theory. The projected area on the UAV body that is affected by the propeller-induced airstream is specified and 2D aerodynamic analyses are performed for the airfoil profile of this region. Lookup-tables are generated and implemented in the nonlinear mathematical model. In addition, aerodynamic coefficients of the airframe are calculated by using CFD method and these data are embedded into the nonlinear model as a lookup-table form. In the transition flight regime, both aerodynamic and thrust forces act on the UAV body and the superimposed dynamics become very complex. Hence, it is important to define a method for hover-to-cruise and cruise-to-hover transitions. To this end, both transition scenarios are designed and a state-schedule is developed for flight velocity, angle of attack, and thrust levels of each of the thrust-propellers. This transition state schedule is used as a feedforward state for the flight control system. We present the simulation results of the transition control system and show the successful transition of TURAC in experiment.

Transition Flight Modeling of a Fixed-Wing VTOL UAV

This paper presents a transition-flight mathematical model of a civil tilt-rotor VTOL unmanned aerial vehicle (UAV) TURAC. Forces and moments acting on the UAV body are calculated using Newton's second law. Aerodynamic effects of free airstream and propeller airstream are defined separately. CFD analyses are performed to specify aerodynamic coefficients for transitional flight regime. The trim point is mathematically defined with respect to angle of attack, tilt angle, airspeed, thrust of tilt-rotor and coaxial fan are defined during transitional flight. A transitional flight scenario is developed with force and moment equations.

Dynamic modeling of a fixed-wing VTOL UAV

Over the last decade, the share of civilian Unmanned Aerial Vehicles (UAVs) in the general UAV market has steadily increased. These systems are being used more and more for applications ranging from crop monitoring to the tracking air emissions in high-pollution areas. Most civilian applications require UAVs to be low cost, portable, and easily packaged while also having Vertical Take-off and Landing (VTOL) capability. In light of this, the TURAC was designed, a VTOL Tilt Rotor UAV with these capabilities. Mathematical and CFD analyses were performed iteratively in order to optimize the design, but testing in actual conditions were needed. However, as with such an iterative design process, the manufacturing process costs, including different molds for each design, can be exorbitant. In addition, once an imperfection in the design is encountered, making design modifications on the full scale UAV prototype is difficult and expensive. Therefore, a cheap, rapid, and easily reproducible prototyping methodology is essential. In this study, the end result of an iterative design process of TURAC is presented. In addition, a low-cost prototyping methodology is developed and its application is demonstrated in detail. The ground and flight tests are applied on a fully functional prototype and the results are given.

Rapid Prototyping of a Fixed-Wing VTOL UAV for Design Testing

Over the last decade, the market share of civilian UAVs within the general UAV market has consistently increased. As such, these systems are increasingly being used for applications ranging from the monitoring of crops to the tracking of air emissions around high-pollution areas. Most of the civilian applications of UAVs require these vehicles to be of low-cost and for the portability and packaging to be easy while also having vertical take-off and landing capability. TURAC - a VTOL Tilt Rotor UAV with these capabilities - is designed. Although mathematical and CFD analyses were performed iteratively in order to optimize the design, testing in real life conditions were needed to see the real performance of the TURAC UAV. However, as with such an iterative design process, the manufacturing process costs, including different molds for each design, can be exorbitant. In addition, once an imperfection in the design is encountered, making radical design modifications on the UAV in real life is difficult and expensive. Therefore, a cheap, rapid, and easily reproducible prototyping methodology is essential. In this study, the end result of an iterative design process of TURAC is presented. In addition, a low-cost prototyping methodology is developed and its application is demonstrated in detail by explaining all of its phases. The ground and flight tests are applied on a fully functional prototype and the results are given.

Aslihan Vuruskan

Papers

Design of a Commercial Hybrid VTOL UAV System

Transition Flight Modeling of a Fixed-Wing VTOL UAV

Dynamic modeling of a fixed-wing VTOL UAV

Rapid Prototyping of a Fixed-Wing VTOL UAV for Design Testing

A low cost prototyping approach for design analysis and flight testing of the TURAC VTOL UAV