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The Impact of Electric Propulsion on the Performance of VTOL UAVs
Abstract
One of the biggest challenges in aviation is the design of transitioning vertical takeoff and landing (VTOL) aircraft. Thrust-borne flight implies a higher mass fraction of the propulsion system, as well as much increased energy consumption in the takeoff and landing phases. A good VTOL design will offset this disadvantage by transitioning to conventional forward flight, thus travelling at much higher efficiency than a comparable rotorcraft, for an overall improvement in mission performance. This paper explores the impact of considering a supplemental electric propulsion system for achieving hovering flight. Key variables in this study are the rotor disk loading and hover flight time, as well as the electrical systems technology level for both batteries and motors. Payload and Endurance are typically used as the measures of merit for unmanned aircraft, and therefore the analysis focuses on these particular parameters.
... [8] The reason why the design of VTOL aircraft is so challenging is simple physics. This is explained well in [9] and is therefore cited here. "VTOL aircraft require a thrustto-weight ratio greater than unity for the vertical part of their mission, however, once transition to forward flight is commenced, typically not more than a thrust-to-weight ratio of 0.1 (depending on the achieved L/Da L/D of 10 is assumed here) is needed to sustain steady flight. ...
... Due to this huge gap in required power, a single propulsion system for both hover flight and cruise flight suffers from reduced efficiency, as its primary operation points are very far from each other." [9] "Hybrid propulsion options (meaning electric lift motors and combustion engines for endurance flight) are used frequently and minimize the weight impact. Because electric motors have a vastly higher power-to-weight ratio than internal combustion engines (currently about 5 kW/kg vs. 1 kW/kg), they are very much suited for this application. ...
... This is not possible for a traditional combustion engine." [9] While the configuration design of VTOL aircraft is discussed extensively in literature (e.g. [5] or [10]), the basic definitions, as well as pros and cons of certain configurations relevant to this paper will be presented here in an abbreviated form. ...
For vertical takeoff and landing (VTOL) aircraft, the power needed for vertical takeoff is much greater than the power needed for cruise. This power-matching problem can be solved with a balanced hybrid-electric propulsion system. However, there is a trade-off between takeoff weight, wing loading, battery technology and range. This paper applies a new initial sizing algorithm for transitioning VTOL aircraft with hybrid-electric propulsion systems, including serial-hybrid and parallel-hybrid configurations. Exemplarily, a family of transitioning VTOL aircraft, intended for urban air mobility (air taxi) operations is designed. Results indicate that hybrid-electric propulsion systems must be considered for future mid-range VTOL aircraft. Very short missions favor fully electric propulsion systems, as this configuration avoids the complexity of a hybrid.
... Other factors that were considered to be important in the mission were lift drag ratio, hover time, and surplus thrust factor. e paper demonstrates the various sizing possibilities depending upon the configuration requirements, which can be viewed as futuristic concepts to drive down cost, as shown in Table 4 [33]. ...
The Vertical Take-off and Landing (VTOL) unmanned aerial vehicles (UAVs) with the tilt-rotor mechanism also known as hybrid
UAVs have a lot of challenges in designing and controlling concerning their use in harsh weather for surveillance and access to
remote areas. is review paper presents a review of the preliminary design of hybrid aircraft and control systems. e tilt-rotor
mechanism and tilt wings of a hybrid UAV are analyzed. e paper provides an outline of technical advances in UAVs in hybrid
conguration concerning their constraint analysis, propulsion sizing, and design evaluation. Furthermore, the ight dynamics
modeling is described with the control system and dynamics of the hybrid UAV. is paper lists various software for simulations
and analysis such as SOLIDWORKS and CATIA for CAD modeling, MATLAB and SIMULINK for mathematical modeling and
ight control, and XFLR5 for stability analysis of aerofoils, wings, and planes. In addition, certain control strategies are executed
and scrutinized in terms of the theory, the linearity, and the implementation of the model.
... Hybrid VTOL systems provide a compromise between rotorcraft and fixed wing by improving forward-flight efficiency while maintaining VTOL capability and are increasingly being trialled for package delivery. These configurations can provide benefits of electric-powered lifting rotors and ICE-powered forward propulsion, but suffer additional drag in forward flight due to the lifting rotors [43]. Tilt-rotors and tilt-wing have demonstrated success and allow two or more rotors to be used for all flight profiles, with the downside of complexity [44]. ...
The backdrop to the rapidly expanding use of drones is described, including development of drone technology, followed by an overview of current civilian use, focusing on use in and around the urban environment. The inhibitors to further use are considered including technological and societal aspects. The operation and control issues are reviewed including autonomous or semi-autonomous operation. Issues of lack of regulation, safety, lack of endurance/payload, noise, inability to fly well in adverse weather are considered. Research into how these issues may be overcome is discussed and comparisons are drawn with how equivalent-sized natural flyers (bird and larger flying insects) cope within the urban environment are made. The paper concludes with an overview of possible and planned use in the urban environment.
... During the last few years, design methods, controllers and performance of QFHUAVs have been greatly explored. 7,[11][12][13][14][15][16][17][18] A few successful QFHUAV products, such as the JUMP 15 from Arcturus UAV, 19 the Hybrid Quadcopter from Latitude Engineering, 20 and the CW 007 from JOUAV, 21 have been used in many situations. Both the works in the literature and these products have proven the applicability of QFHUAVs and their potential to be developed. ...
The wind disturbance rejection capability of a quadrotor fixed-wing hybrid unmanned aerial vehicle (QFHUAV) in the quadrotor mode is an important factor restricting its large-scale applications. In this paper, based on static equilibrium analysis of the quadrotor mode of a QFHUAV with a wind disturbance, a method for analyzing and evaluating the wind disturbance rejection capability of the QFHUAV in the quadrotor mode is presented. The six degrees-of-freedom (6-DOF) static equilibrium equations of the QFHUAV are established in headwind and crosswind situations. The maximum wind velocity that satisfies the equilibrium equations under the constraints of the maximum thrust and torque of the quadrotor propulsion system is used to determine the wind disturbance rejection capability of the QFHUAV in the quadrotor mode. A QFHUAV with a twin-boom is used as an example to analyze and evaluate its wind disturbance rejection capability in the quadrotor mode. The configuration parameters, quadrotor propulsion system parameters, and aerodynamic parameters affecting the wind disturbance rejection capability of the QFHUAV in the quadrotor mode are presented, discussed, and explained. The yawing moment from the wind disturbance is the main factor threatening the safe flight of the QFHUAV in the quadrotor mode. The rotor disk angle, the maximum thrust of the quadrotor propulsion system, and the moment arms of the components of the quadrotor propulsion system thrust are the main factors affecting the wind disturbance rejection capability of the QFHUAV in the quadrotor mode. Increasing these parameter values is an effective approach to improve the wind disturbance rejection capability of the QFHUAV in the quadrotor mode. From the perspective of wind disturbance rejection capability, tailless and X-type layouts are better choices for QFHUAVs. The correctness of results obtained by the proposed method is verified by two flight test schemes.
... While this alone does not completely solve this thrust matching problem, at least it alleviates it [23]. Recently, a new 'hybrid' configuration [24] has gained a lot of popularity amongst designers of unmanned transitioning VTOL aircraft: The fusion between a multicopter and a conventional aircraft [25]. Recent improvements in electrical motor technology and battery systems allow to add an electric hoverpropulsion system to an otherwise conventional UAV, giving it VTOL capability. ...
A hybrid-electric propulsion system combines the advantages of fuel-based systems and battery powered systems and offers new design freedom. To take full advantage of this technology, aircraft designers must be aware of its key differences, compared to conventional, carbon-fuel based, propulsion systems. This paper gives an overview of the challenges and potential benefits associated with the design of aircraft that use hybrid-electric propulsion systems. It offers an introduction of the most popular hybrid-electric propulsion architectures and critically assess them against the conventional and fully electric propulsion configurations. The effects on operational aspects and design aspects are covered. Special consideration is given to the application of hybrid-electric propulsion technology to both unmanned and vertical take-off and landing aircraft. The authors conclude that electric propulsion technology has the potential to revolutionize aircraft design. However, new and innovative methods must be researched, to realize the full benefit of the technology.
... While this alone does not completely solve this thrust matching problem, at least it alleviates it [23]. Recently, a new 'hybrid' configuration [24] has gained a lot of popularity amongst designers of unmanned transitioning VTOL aircraft: The fusion between a multicopter and a conventional aircraft [25]. Recent improvements in electrical motor technology and battery systems allow to add an electric hoverpropulsion system to an otherwise conventional UAV, giving it VTOL capability. ...
A hybrid-electric propulsion system combines the advantages of fuel-based systems and battery powered systems and offers new design freedom. To take full advantage of this technology, aircraft designers must be aware of its key differences, compared to conventional, carbon-fuel based, propulsion systems. This paper gives an overview of the challenges and potential benefits associated with the design of aircraft that use hybrid-electric propulsion systems. It offers an introduction of the most popular hybrid-electric propulsion architectures and critically assess them against the conventional and fully electric propulsion configurations. The effects on operational aspects and design aspects are covered. Special consideration is given to the application of hybrid-electric propulsion technology to both unmanned and vertical takeoff and landing aircraft. The authors conclude that electric propulsion technology has the potential to revolutionize aircraft design. However, new and innovative methods must be researched, to realize the full benefit of the technology.
... The comparison of each hybrid aircraft to the equivalent conventional aircraft with the same mission requirements is conducted using the assessment criterion of maximum take-off mass (MTOM). Consequently, aircraft costs are regarded too, since cost scales almost linearly with aircraft weight for this aircraft class [5,6]. Moreover, the required fuel mass is considered, as well as the primary energy use. ...
In the past decades, interest in cleaner, alternative propulsion increased rapidly. Accordingly, novel approaches for aircraft propulsion are required to meet the spirit of the time. This paper aims to assess the viability of parallel hybrid-electric propulsion systems for General Aviation (GA) aircraft with state of the art technology. Therefore, a comparison to the conventionally powered competitors is performed by using initial sizing results. An assessment of clean sheet designs is performed, as well as an evaluation of retrofit designs. Additionally, parameter studies on battery specific energy and aerodynamic efficiency are conducted to analyze their potential in improving viability and advantages of such aircraft. The studies' results indicate that parallel hybrid-electric light aircraft are able to offer considerable benefits over conventional aircraft, even with today's technological standards. However, several design aspects have to be taken into account to make full use of the benefits arising from these concepts.
... Unfortunately, the conventional design point is only the right design point for conventional aircraft. Because electric motors offer a 3-5 times higher specific power than combustion engines, the propulsion system mass (neglecting the energy source) is reduced [16]. Additionally, the efficiency of electric motors is very high, and much less dependent on the power setting, compared to combustion engines. ...
This paper describes the methodology and the benefits of an initial sizing algorithm that is able to consider aircraft with hybrid-electric propulsion systems by using an innovative point- and mission performance analysis. A central element is the use of the matching diagram (Power-to-weight ratio P/W vs. wing-loading W/S). Conventionally, aircraft are designed for minimal installed power, while still satisfying all performance constraints. This assumption is not applicable to hybrid-electric designs. The combination of P/W and W/S that results in minimal gross weight needs to be determined in conjunction with the optimal degree of hybridization. A sizing study is shown that indicates that the result of such an optimization can be a reduction in sized weight and increased aircraft performance. Hybrid aircraft should be sized with a higher installed P/W and a higher W/S than their conventional counterparts.
... The rotors can then be mounted inline for minimal drag impact. frequently and minimize the weight impact [12]. Because electric motors have a vastly higher power-to-weight ratio than internal combustion engines (about 5 kW/kg vs. ...
One of the biggest challenges in aviation is the design of transitioning vertical takeoff and landing (VTOL) aircraft. Thrust-borne flight implies a higher mass fraction of the propulsion system, as well as much increased energy consumption in the takeoff and landing phases. A good VTOL design will offset this disadvantage by transitioning to conventional forward flight, thus travelling at much higher efficiency than a comparable rotorcraft, for an overall improvement in mission performance. This paper intents to support the configuration designer of VTOL aircraft by giving a review of some of the available configuration possibilities, considering the latest advancements in technology. While VTOL aircraft can use the conventional wing-fuselage-stabilizer configuration, much of new development efforts involve unconventional planforms. The advent of distributed propulsion and electric-or hybrid-electric propulsion systems offers additional opportunities to optimize the vehicle layout and improve flight performance. This review considers propeller driven designs, lift fans and ducted fans, as well as jet lift and hybrid configurations that use a mix of propulsion methods.
The electric propulsion system (EPS) of a quadrotor fixed-wing hybrid unmanned aerial vehicle (QFHUAV) has important effects on its time of endurance and wind disturbance rejection capability in the quadrotor mode. Currently, the design methods of most QFHUAV EPSs are to design the quadrotor propulsion system and fixed-wing propulsion system independently. The wind disturbance rejection capability in the quadrotor mode is not considered in these methods. The multidisciplinary design optimization (MDO) method can reduce design time and cost by integrating all the disciplines involved in the design process. The MDO solutions are generally more optimal with respect to standard optimal sequential solutions. This paper proposes an MDO for a QFHUAV EPS considering the wind disturbance rejection capability in the quadrotor mode. The analysis modules of the propeller/rotor discipline, brushless direct current motor discipline, electronic speed control discipline, lithium polymer battery discipline, time of endurance discipline, mass discipline, and wind disturbance rejection capability in the quadrotor mode discipline are modeled. The MDO process of a QFHUAV EPS is constructed according to the transfer process and coupling relations among the discipline parameters. Based on the mission profile, the flight performance and mission requirements of the QFHUAV are created and a multi-objective optimization design model of the QFHUAV EPS is modeled. The Multidisciplinary feasible approach is implemented to decompose the mass coupling variables between the EPS component analysis modules and the mass analysis module effectively. A multi-objective evolutionary algorithm named NSGA-II is used to discover the full Pareto front for the multi-objective problem. The proposed MDO method is used to design the EPS of a self-developed QFHUAV. The optimal combination of QFHUAV EPS components is determined based on the optimization results. A comparison between the optimization results and the actual flight performance of the QFHUAV shows that the flight performance is in good agreement with the optimization results, which indicates that the MDO method proposed in this paper is feasible and reasonable.
One of the biggest challenges in aviation is the design of transitioning vertical takeoff and landing (VTOL) aircraft. Thrust-borne flight implies a higher mass fraction of the propulsion system, as well as much increased energy consumption in the takeoff and landing phases. A good VTOL design will offset this disadvantage by transitioning to conventional forward flight, thus travelling at much higher efficiency than a comparable rotorcraft, for an overall improvement in mission performance. This paper intents to support the configuration designer of VTOL aircraft by giving a review of some of the available configuration possibilities, considering the latest advancements in technology. While VTOL aircraft can use the conventional wing-fuselage-stabilizer configuration, much of new development efforts involve unconventional planforms. The advent of distributed propulsion and electric-or hybrid-electric propulsion systems offers additional opportunities to optimize the vehicle layout and improve flight performance. This review considers propeller driven designs, lift fans and ducted fans, as well as jet lift and hybrid configurations that use a mix of propulsion methods.
At present, the UAV market is rapidly expanding. Technological innovation and progress makes new aircraft and mission concepts feasible, which would be literally unable to takeoff , employing conventional, manned design approaches. One of the biggest challenges in aviation is the design of vertical takeoff and landing (VTOL) aircraft. A market study, conducted within the scope of this work, showed a supply gap for VTOL UAVs. A VTOL requirement is often cited but there exist very few successful designs. A reason for this is the lack of published research in VTOL UAV configuration design. This paper aims to explore the design space for VTOL UAVs and to evaluate the performance by a direct comparison with conventional aircraft. This is done by developing a model for propulsion and flight performance, which can represent the impact of VTOL systems on aircraft characteristics. The influence of key variables is discussed and the costs and benefits of a VTOL requirement are assessed.
Dieses Buch richtet sich an Entwickler und Anwender von Batterien und batteriebetriebenen Geräten, Planer von Batteriesystemen, Studenten und interessierte Privatpersonen. Es erklärt auf verständliche Weise die Grundlagen und Eigenschaften der einzelnen Systeme. Das Buch konzentriert sich auf die heute gängigen wiederaufladbaren Batteriesysteme, Bleibatterien, NiCd Batterien, NiMH Batterien und Lithium-Ionen sowie Lithium-Polymer Systeme. Im zweiten Teil wird auf den Einsatz von Batterien besonderer Wert gelegt. Schwerpunkte sind hier Lademethoden, Messtechnik, Batteriemanagement sowie die optimale Auslegung und der Bau von Batteriepacks.
In this paper the feasibility of electric on-demand aircraft is discussed in a context that includes the performance characteristics of the aircraft but also its potential cost. Traditional vehicle sizing methods are utilized and weight regressions are updated to link the performance of the aircraft to its acquisition cost. Moreover, cost variables sensitive to performance are identified to enable the integration between the costs of operation and aircraft performance. This formulation is used to assess the feasibility of the aircraft by considering the coupling of its physical constraints and its cost. With this integration a design environment that enables design space exploration is constructed. The environment can aid in the identification of favorable design conditions that could make an electric on-demand vehicle feasible in the future.
Find the right answer the first time with this useful handbook of preliminary aircraft design. Written by an engineer with close to 20 years of design experience, General Aviation Aircraft Design: Applied Methods and Procedures provides the practicing engineer with a versatile handbook that serves as the first source for finding answers to realistic aircraft design questions. The book is structured in an "equation/derivation/solved example" format for easy access to content. Readers will find it a valuable guide to topics such as sizing of horizontal and vertical tails to minimize drag, sizing of lifting surfaces to ensure proper dynamic stability, numerical performance methods, and common faults and fixes in aircraft design. In most cases, numerical examples involve actual aircraft specs. Concepts are visually depicted by a number of useful black-and-white figures, photos, and graphs (with full-color images included in the eBook only). Broad and deep in coverage, it is intended for practicing engineers, aerospace engineering students, mathematically astute amateur aircraft designers, and anyone interested in aircraft design.
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