An overview of the self-organizing map algorithm, on which the papers in this issue are based, is presented in this article.

The Self-Organizing Map

T HE utility and cost effectiveness of small unmanned aerial vehicles (UAVs) has seen a large increase in their use, in both civilian and military applications. Depending on the particular requirements, the aircraft may be powered using a piston-gasoline engine or an electric motor. Electric propulsion appears to be favored as the UAV size diminishes or if stealth, in terms of acoustic signature, is a design requirement. Expressions to estimate the range and endurance of piston propeller and jet aircraft are well established [1,2] (the Breguet equations). Estimates for the range and endurance of electric aircraft are less well established [3,4] and may not be presented in a fashion consistent with that typically employed in the aeronautics community. Consideration of the propulsion system would suggest that equating the power delivered by the battery, accounting for losses due to the propeller, motor, and motor controller, to the power required to overcome drag would yield performance estimates. While this approach is sound, the behavior of a battery and its effective capacity, depending on the current draw (the so-called Peukert effect [5]), should be accounted for; otherwise, significant estimation errors may occur. Consequently, in this Note, expressions are derived to estimate the range and endurance of a battery-powered electric aircraft, accounting for battery discharge behavior. The impact of ignoring the Peukert effect is investigated. Parameters affecting performance are examined.

Range and Endurance Estimates for Battery-Powered Aircraft

HE utility and cost effectiveness of small unmanned aerialvehicles (UAVs) has seen a large increase in their use, in bothcivilian and military applications. Depending on the particularrequirements, the aircraft may be powered using a piston-gasolineengineoranelectricmotor.Electricpropulsionappearstobefavoredas the UAV size diminishes or if stealth, in terms of acousticsignature, is a design requirement.Expressions to estimate the range and endurance of pistonpropeller and jet aircraft are well established [1,2] (the Breguetequations).Estimatesfortherangeandenduranceofelectricaircraftare less well established [3,4]and may not be presented in a fashionconsistent with that typically employed in the aeronauticscommunity. Consideration of the propulsion system would suggestthat equating the power delivered by the battery, accounting forlossesduetothepropeller,motor,andmotorcontroller,tothepowerrequired to overcome drag would yield performance estimates.While this approach is sound, the behavior of a battery and itseffective capacity, depending on the current draw (the so-calledPeukert effect [5]), should be accounted for; otherwise, signiﬁcantestimation errors may occur.Consequently,inthisNote,expressionsarederivedtoestimatetherange and endurance of a battery-powered electric aircraft,accounting for battery discharge behavior. The impact of ignoringthe Peukert effect is investigated. Parameters affecting performanceare examined.

Engineering Notes Range and Endurance Estimates for Battery-Powered Aircraft

Nowadays, Unmanned Aerial Vehicles (UAVs) are used in many different applications. Using systems of multiple UAVs is the next obvious step in the process of applying this technology for variety of ...

https://www.worldscientific.com/doi/pdf/10.1142/S2301385020500090

Multiple UAV Systems: A Survey

On parallel hybrid-electric propulsion system for unmanned aerial vehicles

This paper describes recent research into the advancement of small, electric powered unmanned aerial vehicle (UAV) capabilities. Specifically, topics include the improvements made in battery technology, design methodologies, avionics architectures and algorithms, materials and structural concepts, propulsion system performance prediction, and others. The results of prototype vehicle designs and flight tests are discussed in the context of their usefulness in defining and validating progress in the various technology areas. Further areas of research need are also identified. These include the need for more robust operating regimes (wind, gust, etc.), and continued improvement in payload fraction vs. endurance.

/pdf/small-uav-research-and-evolution-in-long-endurance-electric-4an94f20c8.pdf

Small UAV Research and Evolution in Long Endurance Electric Powered Vehicles

Many beneficial civilian applications of commercial and public small unmanned aircraft systems (sUAS) in low-altitude uncontrolled airspace have been proposed and are being developed. Associated with the proliferation of civil applications for sUAS is an expected requirement for BVLOS (beyond visual line of sight) operations with increasing use of autonomous systems and operations under increasing levels of urban development and airspace usage. It is also anticipated that future demand will necessitate a shift toward multi-UAS operations in which a single operator will be responsible for the safe operation of multiple sUAS simultaneously. As risk increases for ensuring the safety of manned aircraft and persons on the ground (e.g., in suburban and urban environments), these operations become safety-critical. Ensuring the safety and effectiveness of these safety-critical operations will require an assessment of the impacts of safety hazards on sUAS and their operation, as well as the development of hazard mitigation and contingency management systems and strategies that reduce the associated risk. Safety assessments must be performed under nominal and off-nominal conditions using analysis, simulation, and experimental testing that utilize a set of test scenarios designed to expose safety vulnerabilities. Moreover, the effectiveness of hazard mitigation systems and contingency management strategies must be similarly evaluated. Experimental test techniques and hazardsbased test scenarios that facilitate these safety assessments are therefore needed, as well as sUAS computer simulation models that are capable of characterizing off-nominal vehicle dynamics. Ultimately, real-time risk assessment and safety assurance systems may be needed for safetycritical operations such that determination of unacceptable risk will initiate hazard mitigation actions to reduce risk to an acceptable level and thereby ensure safety. This capability may especially be needed to enable (and ensure) safe multi-UAS operations under uncertain, offnominal, and hazardous conditions. This will require the development of methodologies for the effective detection and mitigation of emergent (unanticipated) safety hazards, as well as humanautomation interface systems that enable effective teaming under adverse conditions. Validation of these systems will require (in part) experimental testing in a realistic and relevant flight environment. This paper presents experimental flight test techniques and an initial set of hazardsbased test scenarios that are under development for assessing the safety of sUAS operations. Key research and technical requirements for establishing a flight test environment for assessing the safety of multi-UAS operations are also briefly addressed.

Experimental Flight Testing for Assessing the Safety of Unmanned Aircraft System Safety-Critical Operations

A set of more than 100 flight operations were conducted at NASA Langley Research Center using small UAS (sUAS) to demonstrate, test, and evaluate a set of technologies and an overarching air-ground system concept aimed at enabling safety. The research vehicle was tracked continuously during nominal traversal of planned flight paths while autonomously operating over moderately populated land. For selected flights, off-nominal risks were introduced, including vehicle-to-vehicle (V2V) encounters. Three contingency maneuvers were demonstrated that provide safe responses. These maneuvers made use of an integrated air/ground platform and two on-board autonomous capabilities. Flight data was monitored and recorded with multiple ground systems and was forwarded in real time to a UAS traffic management (UTM) server for airspace coordination and supervision.

/pdf/testing-enabling-technologies-for-safe-uas-urban-operations-h0cg135qv5.pdf

Testing Enabling Technologies for Safe UAS Urban Operations

Small unmanned aerial systems (sUAS) have been studied and results indicate that there is a large array of highly-beneficial applications. These applications are too numerous to list, but include search and rescue, fire spotting, precision agriculture, etc. to name a few. Typically sUAS vehicles weigh less than 55 pounds and will be performing flight operations in the presence of manned aircraft and other sUAS. Certain sUAS applications, such as package delivery, will include operations in the close proximity of the general public. The full benefit from sUAS is contingent upon the resolution of several technological areas to enable free and widespread use of these vehicles. Technological areas in question include, but are not limited to: autonomous sense and avoid and deconfliction of sUAS from other sUAS and manned aircraft, communications and interfaces between the vehicle and human operators, and high-reliability autonomous systems. The NASA UAS Traffic Management (UTM) project is endeavoring to develop a traffic management system and concept of operations for these types of vehicles. An extensive sUAS flight test effort was performed to partially address vehicle-related technological areas and to shape an understanding of future developmental and test efforts for vehicles intended to use the UTM traffic management system. The flight testing described herein had the following objectives: 1) Install and test Dedicated Short Range Communications (DSRC) systems developed for the automotive industry for potential sense and avoid sUAS applications; 2) Evaluate the use of cellular 4G systems to provide vehicle control; 3) Obtain high-resolution video imagery in support of image-based optical detection sense and avoid systems; 4) Acquire data in fixed-wing flight to support validation and maturation of an autonomous range containment system known as Safeguard in fixed-wing flight. A total of 53 flights were performed over 12 operational days at Beaver Dam Airpark in Elberon, VA. This work was sponsored by the UTM project that is part of the Aviation Operations and Safety Program (AOSP) at NASA.

/pdf/small-unmanned-aerial-system-uas-flight-testing-of-enabling-1oxbhqdp91.pdf

Small Unmanned Aerial System (UAS) Flight Testing of Enabling Vehicle Technologies for the UAS Traffic Management Project

Development of highly capable small UAVs present unique challenges for technology protagonists. Size constraints, the desire for ultra low cost and/or disposable platforms, lack of capable design and analysis tools, and unique mission requirements all add to the level of difficulty in creating state-of-the-art small UAVs. This paper presents the results of several small UAV developments, the difficulties encountered, and proposes a list of technology shortfalls that need to be addressed.

/pdf/technology-challenges-in-small-uav-development-2d58k5panb.pdf

Michael J. Logan

Papers

Small UAV Research and Evolution in Long Endurance Electric Powered Vehicles

Experimental Flight Testing for Assessing the Safety of Unmanned Aircraft System Safety-Critical Operations

Testing Enabling Technologies for Safe UAS Urban Operations

Small Unmanned Aerial System (UAS) Flight Testing of Enabling Vehicle Technologies for the UAS Traffic Management Project

Technology Challenges in Small UAV Development