Development of design methodology for a small solar-powered unmanned aerial vehicle

Existing mathematical design models for small solar-powered electric unmanned aerial vehicles (UAVs) only focus on mass, performance, and aerodynamic analyses. Presently, UAV designs have low endurance. The current study aims to improve the shortcomings of existing UAV design models. Three new design aspects (i.e., electric propulsion, sensitivity, and trend analysis), three improved design properties (i.e., mass, aerodynamics, and mission profile), and a design feature (i.e., solar irradiance) are incorporated to enhance the existing small solar UAV design model. A design validation experiment established that the use of the proposed mathematical design model may at least improve power consumption-to-take-off mass ratio by 25% than that of previously designed UAVs. UAVs powered by solar (solar and battery) and nonsolar (battery-only) energy were also compared, showing that nonsolar UAVs can generally carry more payloads at a particular time and place than solar UAVs with sufficient endurance requirement. The investigation also identified that the payload results in the highest effect on the maximum take-off weight, followed by the battery, structure, and propulsion weight with the three new design aspects (i.e., electric propulsion, sensitivity, and trend analysis) for sizing consideration to optimize UAV designs

Designing and building a hybrid (electric/ic) UAV

In comparison with conventional internal combustion (IC) engine power trains, a hybrid electric propulsion system with two or more energy sources has proved to be a more effective in terms of pollution rate, and a reduction of heat release and sound effects. For applications of hybrid electric/IC propulsion to vehicles and especially military, it has been demonstrated that considerable improvement of energy use by reducing fuel consumption required for basic functions occurs. Due to these factors, the use of unmanned aerial vehicles (UAVs) may be adopted to civil service as well. This might include detecting and monitoring disaster, hazards, and environment conditions, and reserving backup power for emergency. Based on the above information, this Capstone Project aims to develop the design a prototype of an economical and practical small scale tilt-rotor UAV, with emphasis on good performance characteristics, including high endurance, a rotor-tilting mechanism, payload capacity and vertical to horizontal transition stability. The main focus was on optimizing the aerodynamic parameters of fixed-wing prototype and combining the hovering abilities of a multi-rotor UAV. The CAD model built in SolidWorks, computational analysis and simulations of the vehicle performance in Ansys CFX related to this project are delivered as well. In addition, laboratory work was done in order to check performance of both the engine and generator

Innovative Propulsion Systems and CFD Simulation for Fixed Wings UAVs

Nowadays, mobile applications demand, in large extent, an improvement in the overall efficiency of systems, in order to diversify the number of applications. For unmanned aerial vehicles (UAVs), an enhancement in their performance translates into larger payloads and range. These factors encourage the search for novel propulsion architectures, which present high synergy with the airframe and remaining components and subsystems, to enable a better UAV performance. In this context, technologies broadly examined are distributed propulsion (DP), thrust split (TS), and boundary layer ingestion (BLI), which have shown potential opportunities to achieve ambitious performance targets (ACARE 2020, NASA N+3). The present work briefly describes these technologies and shows preliminary results for a conceptual propulsion configuration using a set number of propulsors. Furthermore, the simulation process for a blended wing body (BWB) airframe using computational fluid dynamics (CFD) OpenFOAM software is described. The latter is examined due to its advantages in terms of versatility and cost, compared with licensed CFD software. This work does not intend to give a broad explanation of each of the topics, but rather to give an insight into the state of the art in modeling of distributed propulsion systems and CFD simulation using open-source software implemented in UAVs

DESIGN METHODS FOR REMOTELY POWERED UNMANNED AERIAL VEHICLES

A method for sizing remotely powered unmanned aerial vehicles is presented to augment the conventional design process. This method allows for unconventionally powered aircraft to become options in trade studies during the initial design phase. A design matrix is created that shows where, and if, a remotely powered vehicle fits within the design space. For given range and power requirements, the design matrix uses historical data to determine whether an internal combustion or electrical system would be most appropriate. Trends in the historical data show that the break in the design space between the two systems is around 30 miles and 1 kW. Electrical systems are broken into subcategories of onboard energy sources and remote power sources. For this work, only batteries were considered as an onboard energy source, but both lasers and microwaves were considered for remote power transmission methods. The conventional sizing method is adjusted to so that it is based on energy consumption, instead of fuel consumption. Using the manner in which microwaves and laser propagate through the atmosphere, the weight fraction of a receiving apparatus is estimated. This is then used with the sizing method to determine the gross takeoff weight of the vehicle. This new sizing method is used to compare battery systems, microwave systems, and laser systems

High Specific Power Electrical Machines: A System Perspective

There has been a growing need for high specific power electrical machines for a wide range of applications. These include hybrid/electric traction applications, aerospace applications and Oil and Gas applications. A lot of work has been done to accomplish significantly higher specific power electrical machines especially for aerospace applications. Several machine topologies as well as thermal management schemes have been proposed. Even though there has been a few publications that provided an overview of high-speed and high specific power electrical machines [1-3], the goal of this paper is to provide a more comprehensive review of high specific power electrical machines with special focus on machines that have been built and tested and are considered the leading candidates defining the state-of-the art. Another key objective of this paper is to highlight the key “system-level” tradeoffs involved in pushing electrical machines to higher specific power. Focusing solely on the machine specific power can lead to a sub-optimal solution at the system-level

Accessibility Design and Operational Considerations in the Development of Urban Aerial Mobility Vehicles and Networks

Urban aerial mobility vehicles and networks have recently gained considerable interest in the aviation community. These small, short-range vehicles with all-electric or hybrid-electric propulsion systems, tailored to metropolitan aerial transportation needs, promise to radically change passenger mobility and cargo distribution in cities. Accessibility issues have not been a major consideration in UAM vehicle and network discussions to date. This paper seeks to help change that

Preliminary design of a fuel cell - battery hybrid propulsion system for a small VTOL UAV

Master's thesis in Mechanical engineeringOver the past decade, utilization of unmanned aerial vehicles (UAVs) in military and commercial applications has increased significantly. The vertical take-off and landing (VTOL) UAV is appreciated for its easy launch and versatile operation capability, but the missions are limited due to low endurance. Hybrid fuel cell systems have the potential to increase the endurance significantly. Until now, the use of fuel cell systems in VTOL UAVs have been limited to demonstrations, but as new and lightweight fuel cell systems have been developed, the technology seems to have reached the maturity level needed to realize fuel cell powered VTOL UAVs for more widespread use. This paper considers the implementation of a hybrid fuel cell – battery system on an existing VTOL UAV with maximum take-off weight (MTOW) of 25 kg. The available technology for fuel cells and hydrogen storage are investigated with the aim of determining the best solution for this UAV, and a preliminary design of the entire propulsion system is done. The selection of different components is based on power estimation from momentum theory. The hydrogen storage is a customized spherical composite pressure vessel. A comparison between cylindrical and spherical pressure vessels are performed to justify the use of a spherical pressure vessel. The calculations are based on classical lamination theory. The results indicate that a spherical pressure vessel gives weight savings of 15 %. The estimated endurance of the proposed system is 3.2 hours at MTOW with a custom spherical pressure of 21 liters. This is a 7-fold improvement compared to the current installed batteries