Computationally adaptive multi-objective trajectory optimization for UAS with variable planning deadlines

Unmanned Aerial System (UAS)-enabled bridge inspection technique, as a promising alternative to conventional practices, has drawn more interest in recent years. However, UAS performance metrics requirements imposed by bridge structure (e.g., turbulent flow characteristics around the bridge) and terrain characteristics (e.g., surface roughness, temperature, and humidity), have made the selection of the suitable UAS platform a challenging problem. Currently, there is no verified and comprehensive methodology for UAS-enabled bridge inspection practices; existing case-dependent solutions rely on general-purpose commercially available UAS platforms. There is no study to quantify the gap between the performance metrics of the commercially available UAS platforms to those required for the bridge inspection. The objective of this paper is to initiate the development of a framework to systematically select a commercially available UAS that is the most appropriate choice for bridge inspection. An Analytic Hierarchy Process (AHP) methodology is adopted for the multiple-criteria decision making (MCDM) and comparing the capabilities of multiple UAS platforms. The AHP methodology is applied to 32 criteria defined under Four major categories including flight performance, situational awareness, payload and sensor capabilities, and communication quality. The developed method is illustrated and applied to a set of UAS platforms. A pairwise comparison approach is conducted in a hierarchical manner at the category level, criterion level, and candidate platform level. The results from comparison tables that meet the required AHP consistency ratio threshold, result in the selection of the most suitable UAS for bridge inspection in the defined scenario.

Policy processes and recommendations for Unmanned Aerial System operations near roadways based on visual attention of drivers

As a result of the FAA Modernization and Reform Act of 2012, Unmanned Aerial Systems (UAS) are expected to be integrated into the National Airspace System (NAS) by 2015. Several human factors challenges need to be addressed before UAS can safely and routinely fly in the NAS with manned aircraft. Perhaps the most significant challenge is for the UAS to be non-disruptive to the air traffic management system. Another human factors challenge is how to provide UAS pilots with intuitive traffic information in order to support situation awareness (SA) of their airspace environment as well as a see-and-avoid capability comparable to manned aircraft so that a UAS pilot could safely maneuver the aircraft to maintain separation and collision avoidance if necessary. A simulation experiment was conducted to examine baseline compliance of UAS operations in the current airspace system. Researchers also examined the effects of introducing a Cockpit Situation Display (CSD) into a UAS Ground Control Station (GCS) on UAS pilot performance, workload and situation awareness while flying in a positively controlled sector. Pilots were tasked with conducting a highway patrol police mission with a Medium Altitude Long Endurance (MALE) UAS in L.A. Center airspace with two mission objectives: 1) to reroute the UAS when issued new instructions from their commander, and 2) to communicate with Air Traffic Control (ATC) to negotiate flight plan changes and respond to vectoring and altitude change instructions. Objective aircraft separation data, workload ratings, SA data, and subjective ratings regarding UAS operations in the NAS were collected. Results indicate that UAS pilots were able to comply appropriately with ATC instructions. In addition, the introduction of the CSD improved pilot SA and reduced workload associated with UAS and ATC interactions.

This paper presents a systematic method for generating optimal helicopter flight trajectories in real time for cockpit display. Helicopter flights in the event of a single engine failure are critical, and display of optimal flight paths on-board is desirable. Due to the large number of states and constraints, however, numerical solutions on a mainframe computer can take a long tune. In this paper, optimal solutions are first obtained off-line using a ground computer. For a given set of initial helicopter states and flight parameters, optimal solutions are fitted by a Fourier series. The coefficients of the Fourier approximations are then interpolated as functions of initial flight states and parameters. The approximate optimal trajectories can be quickly generated on-board using the proposed method. Introduction Engine failure is a major safety issue for all helicopters, especially during takeoff and landing operations. Due to the complexity of the situation and the dependence of safety on many parameters, optimal flight trajectories can provide useful guidance for pilot operation. In particular, on-board display of optimal trajectories is desirable. This paper presents a method for generating optimal flight trajectories in real-tune that can be used for on-board display. Depending on its capability and performance during an engine failure, a transport helicopter can be certified as Category A or Category B. The Federal Aviation Administration (FAA) grants Category B certification to a single or multi-engine helicopter with gross weight less than 20,000 Ib and capable of landing safely in case of one or all engine failures. Category A certification, on the other hand, is granted to multi-engine helicopters with independent engine systems. Category A helicopters must be able to either land safely or continue flight in case of One Engine Inoperation (OEI). This makes Category A helicopters uniquely suited for remote places where emergency landing sites are not available. I Ph.D. Candidate, Center for Control Sciences, Member AIAA * Assistant Professor, Dept. of Aerospace Eng. and Mechanics, Member AIAA + Civil Rotorcraft Group Leader, Rotorcraft and Powered Lift Branch The decision to continue the flight or to land represents an energy management problem. It has been shown''' that this decision depends on initial conditions at the time of failure as well as flight parameters. Due to the numerous initial variables involved in this decision, a method to communicate all this information to the pilot instantaneously, at engine failure, is needed. This method must keep the emergency procedure simple and manageable. In particular, on-board cockpit display of optimal flight trajectories is useful. This requires a reliable real-tune solution of optimal trajectories, on board, with limited time, limited computing power, and limited memory available. If possible, an analytical solution of optimal trajectories is desirable. Unfortunately, this can only be achieved for systems of low order and where the equations of motion and the cost function are simple. Therefore, for a complex system, an open-loop numerical procedure becomes necessary. Research efforts were made to solve optimal control problems in real-time. Schultz et al. used calculus of variation and energy state method to generate optimal trajectories on-board for the National Aerospace Plane (NASP). In his study, the equations of motion of the NASP are less complex than those of the helicopter, and an interval of time of few minutes is allowed. Bryson used neighboring control theory to generate near-optimal solutions that could be used in real-time. This method is elegant but requires a large amount of memory to store the needed perturbation matrices. Also, it is valid on a relatively small neighborhood of the nominal trajectory. Perturbation methods and table lookups are often used if only few parameters are involved. In the current problem, the equations of motion of the helicopter are complex and too many path equality and inequality constraints are present. Also, limitations on tune, computing power, and memory available make all the above methods unsuitable for this problem. This paper proposes a technique of real-time optimal trajectory generation based on approximation and

The growing demand for Unmanned Aerial Systems (UAS) operating beyond the line of sight (BLOS) has resulted in an increased interest in using existing commercial satellite communication capabilities for UAS command and control (C2) communications. The World Radiocommunication Conference in 2015 designated portions of Ku-Band and Ka-Band fixed satellite service (FSS) spectrum to support UAS C2 communications, provided that potential interference with existing co-allocated users in these bands is addressed. As the user base in this new spectrum allocation expands, there is an increased potential for interference with existing terrestrial communication systems operating under fixed service (FS) allocations. The portion of Ka-Band spectrum allocated for UAS C2 avoids significant interference issues, but the Ku-Band allocation contains a co-primary FS allocation, creating potential interference problems. Therefore, UAS must identify solutions to avoid interfering with these existing FS ground sites while maintaining good links with satellite constellations. UAS operating with conventional fixed feed parabolic antennas will have difficulty in meeting interference thresholds, especially at high latitudes where the antennas will operate with low elevation angles. As a means of addressing this limitation, NASA is investigating the use of a phased array antenna to enable mitigation of interference into ground-based FS receivers. In this paper, a novel lightweight conformal phased array antenna will be presented that can use null-steering and/or beam shaping to avoid ground interference while simultaneously providing strong satellite microwave links for communications. The reduced weight of this design and ability to integrate into the fuselage of smaller UAS platforms will also be discussed as a potential solution to provide BLOS operation via spectrum sharing for an expanding user base. This presentation will review design aspects of the conformal phased array antenna, describe the intended benefits in reducing interference with FS ground stations, and describe phased array development and test plans.

The rapid growth of urban mobility and logistics demands innovative solutions to address congestion, inefficiencies, and sustainability challenges. Unmanned Aerial Systems (UAS) offer a promising alternative for urban transportation, particularly in last-mile deliveries and emergency response. To accommodate the anticipated scale of UAS operations, potentially involving millions of daily flights, the UAS Traffic Management (UTM) ecosystem must support safe, efficient, and fair airspace access while minimizing disruption. UAS operations in dense urban areas must be supported by efficient and scalable path planning and deconflicting mechanisms which compute collision-free trajectories. A dynamic rerouting mechanism allows UAS trajectories to dynamically adapt to real-time deviations caused by environmental factors, communication errors, or dynamic airspace constraints. In this paper, we introduce a UAS Path Planning with Dynamic Rerouting framework that leverages a space-time graph model to ensure safe and efficient variable speed UAS navigation in urban environments. Our approach provides collision-free trajectories by construction and enables real-time path adjustments by dynamically rerouting UAS in case of slowdown events. By incorporating real-time request management and collision-free trajectories, our model enhances the feasibility of integrating UAS into multimodal urban transportation networks. We analyze the computational efficiency of our approach and demonstrate its scalability through simulation experiments using a real-world urban map in very dense scenarios with up to 14000 UAS vehicles. Our results indicate that dynamic rerouting with collision-free trajectory computation improves UAS route availability while maintaining airspace safety and operational efficiency.

This paper explores the potential of integrating Global Navigation Satellite System (GNSS) Avionics Based Integrity Augmentation (ABIA) functionalities in Unmanned Aerial Systems (UAS) to perform mission planning and real-time trajectory optimisation tasks. In case of mission planning, a pseudo-spectral optimization technique is adopted. For real-time trajectory optimisation a Direct Constrained Optimisation (DCO) method is employed. In this method the aircraft dynamics model is used to generate a number of feasible flight trajectories that also satisfy the GNSS integrity constraints. The feasible trajectories are calculated by initialising the aircraft dynamics model with a manoeuvre identification algorithm. The performance of the proposed GNSS integrity augmentation and trajectory optimisation algorithms was evaluated in representative simulation case studies. Additionally, the ABIA performance was compared with Space-Based and Ground-Based Augmentation Systems (SBAS/GBAS). Simulation results show that the proposed integration scheme is capable of performing safety-critical UAS tasks (CAT III precision approach, UAS Detect-and-Avoid, etc.) when GNSS is used as the primary source of navigation data. There is a synergy with SBAS/GBAS in providing suitable (predictive and reactive) integrity flags in all flight phases. Therefore, the integration of ABIA with SBAS/GBAS is a clear opportunity for future research towards the development of a Space-Ground-Avionics Augmentation Network (SGAAN) for UAS SAA and other safety-critical aviation applications.

The use of Unmanned Aerial Systems (UASs) is emerging more and more in recent years for many civil applications. They provide great opportunities in urban areas and, in particular, they will be involved in smart cities, bringing many advantages in terms of lower cost and operational flexibility. In this paper, we propose a survey of UAS technologies to enable safe flight operations in urban areas. The main goal of this paper is to investigate the most efficient solution to perform UAS missions and to manage aerial traffic in a future congested sky. The development of new mobile Internet technologies, the progress of UAS technology and the necessity to perform automatic/autonomous flight missions open new opportunities to UAS operations. Moreover, a revision of current UAS regulations is necessary.After a survey of UAS technologies, we discuss how the combination of an autonomous vehicle in Beyond Visual Line-of-Sight mode and a wireless connection with a mobile Internet connection could improve the UAS operations.

The cone of uncertainty of a small unmanned aerial vehicle's (UAV) flight trajectory induced by the aircraft's encounters with an upstream wake vortex or gust is addressed in the context of safety assessments for UAS operations. Such safety assessments will be a critical facet of the integration of unmanned aerial systems (UAS) into the National Airspace System (NAS), particularly in terminal airspace. This paper describes a predictive, robust feedback-loop flight control model that is applicable to various classes of UAVs and unsteady flight-path scenarios. The current test study investigates a new robust flight controller employing a ‘virtual’ control surface, which is generated using arrays of synthetic-jet micro-actuators (SJA). For a given amplitude of the flow disturbance and UAS parameters, the model employed in this paper allows us to estimate UAS flight-path deviations and recovery time, as well as to identify the limits of the control authority. In addition, the computationally simplistic structure of the proposed robust flight control method can operate at a faster sample rate, which can enable a UAS to recover more quickly from external disturbances due to wind gusts, while effectively minimizing deviations from the desired flight trajectory.

The article provides an in-depth, systematic analysis of the regulatory and legal component that forms the foundation for the use of unmanned aerial systems (UAS) by the state border protection bodies of the State Border Guard Service of Ukraine (hereinafter – SBGS). The research covers the entire hierarchical structure of national legislation that directly or indirectly regulates the use of UAS, ranging from fundamental acts of the highest legal force, such as the Air Code of Ukraine and the specialized Law of Ukraine «On the State Border Guard Service of Ukraine,» to specialized by-laws that detail operational procedures, including the Cabinet of Ministers’ Resolution No. 954 «On Approval of the Regulation on the Use of the Airspace of Ukraine» and the key departmental document – the Ministry of Defence Order No. 661, which approves the «Rules for the Operation of Unmanned Aerial Systems of State Aviation of Ukraine.» It has been established that the current legal framework, despite the existence of basic powers, is characterized by significant fragmentation, internal contradictions, and the presence of substantial gaps, which collectively create a regime of legal uncertainty. This situation generates significant operational and legal risks for SBGS personnel, who are forced to operate in conditions where the performance of their official duties may formally contradict outdated aviation legislation. The central object of analysis is the fundamental legal conflict arising from the mechanical extension of general requirements (certification, registration, permits), developed for traditional manned aviation, to UAS, which are irrelevant and operationally impossible to implement for most types of drones used by the SBGS. Special attention is paid to the analysis of recent legislative initiatives, particularly draft laws No. 8185 and No. 8186, which are a response to urgent security challenges. It is detailed how these acts fundamentally transform the role of the SBGS from a mere user of airspace to its active guardian, granting powers for the forced termination of UAS flights used for illegal activities in the border strip. At the same time, it is emphasized that this expansion of powers creates new challenges that require further detailing, particularly the development of clear inter-agency deconfliction protocols and rules of engagement. The conclusion is substantiated regarding the urgent strategic need to adopt a single, comprehensive legislative act that would systematically regulate all aspects of the «life cycle» and application of UAS by the SBGS, taking into account the unique hybrid nature of its activities, which combines law enforcement and defense tasks.

The drone sector offers a wide range of affordances, opportunities, and economic benefits for society. Delivery services, agriculture monitoring, wildfire control, public infrastructure inspections, humanitarian aid, or drone journalism, are among the activities enhanced by unmanned aerial systems (UAS). No surprise the civilian UAS market is growing fast throughout the world. Yet, on a daily basis, newspapers report serious concerns for people infringing other people’s rights through the use of drones. Cybersecurity attacks, data theft, criminal offences brought about the use of this technology frame the picture. Nowadays, several countries are changing their legal rules to properly address such challenges. In 2018, the European Union (EU) started its five year-long regulative process that should establish the common rules and standards for UAS operations within the EU Single Sky by 2023. A similar timeline has been adopted in the United States, so as to provide the jurisdictional boundaries for the civilian use of drones. The United Kingdom (UK) and Japan are adopting new rules too. From a legal point of view, the overall framework is thus rapidly evolving. The aim of this paper is to give attention to (i) privacy and data protection concerns raised by UAS operations; (ii) their monitoring functions and corresponding surveillance issues; and, (iii) how a privacy preserving approach – such as with privacy by design technologies, organizational measures, audit procedures, civic involvement, to name a few – makes a lawful and ethical use of this powerful technology possible.

With the increased availability of unmanned aerial systems (UAS) imagery, digitalized forest inventory has gained prominence in recent years. This paper presents a methodology for automated measurement of tree height and crown area in two broadleaf tree plantations of different species and ages using two different UAS platforms. Using structure from motion (SfM), we generated canopy height models (CHMs) for each broadleaf plantation in Indiana, USA. From the CHMs, we calculated individual tree parameters automatically through an open-source web tool developed using the Shiny R package and assessed the accuracy against field measurements. Our analysis shows higher tree measurement accuracy with the datasets derived from multi-rotor platform (M600) than with the fixed wing platform (Bramor). The results show that our automated method could identify individual trees (F-score > 90%) and tree biometrics (root mean square error < 1.2 m for height and <1 m2 for the crown area) with reasonably good accuracy. Moreover, our automated tool can efficiently calculate tree-level biometric estimations for 4600 trees within 30 min based on a CHM from UAS-SfM derived images. This automated UAS imagery approach for tree-level forest measurements will be beneficial to landowners and forest managers by streamlining their broadleaf forest measurement and monitoring effort.

Recent advances and ubiquity of Unmanned Aerial System (UAS) capabilities have expedited the need for counter UAS capabilities. While visible imaging and acoustic sensors have been widely used to detect/track UAS signatures, several challenges remain: (1) images that are acquired using EO sensors that are sensitive to visible light (0.4-0.7μm) contain a significant amount of clutter leading to false detections and have limited feasibility under low variable lighting condition (e.g., nighttime), (2) visible imagery is more susceptible to nonlinear, time varying atmospheric distortions, and (3) the discriminative power spectrum of UAS acoustic signatures are sensitive to amplifier gains, microphone array directional response characteristics, and obfuscation by non-white acoustic clutter/noise. Instead, we consider using thermal infrared—specifically longwave infrared (7-14μm)— cameras to detect UAS platforms. Additionally, we consider detecting UAS platforms using a UAS-based counter surveillance platform equipped with the thermal infrared imaging payload, opposed to conventional ground-based counter UAS imaging systems. Here, challenges arise from limited discriminative details and quality in thermal imagery (compared with visible imagery) due variations in sensors, standoff distance, and motion. Therefore, we present a new dataset containing both thermal and visible imagery designed to evaluate UAS detection performance using existing object detectors, such as YOLOv5,1 RetinaNet,2, 3 and SSD.4 More importantly, we present a novel deep domain adaptive framework to optimize the object detectors for more discriminative detection performance and to enhance both daytime and nighttime operations. Lastly, we provide extensive analysis that compares our framework to state-of-the-art domain adaptation methods using our dataset.

There are many current active orthosis designs to assist with disabilities related to foot-drop, with most of them intervening during the whole gait cycle. We propose that, for the treatment of foot-drop, it is possible to design an ankle–foot device that will assist a walking user only during the dorsiflexion stages of the gait, avoiding interference with other stages, by using a single actuator with a simple transmission and a suspension block. This design can be improved by the use of multi-objective optimization to obtain a static set of parameters that are applicable to varying initial conditions. We present a computer simulation study of an active ankle–foot orthosis design, based on the interaction of a cam and lever with a suspension block, with the objective of assisting only with dorsiflexion during the gait cycle, leaving the rest of the movements unimpeded while reducing the complexity and weight of the device. This design is validated using a full simulation environment that includes the movements of the lower leg and foot, as they interact with our device and a ground element. As part of the design and validation, we found sets of mechanical and control parameters that provoke adequate output behavior of the orthosis to help the wearer perform a moderate-speed, normal gait. To optimize the design, we proposed three objectives to warrant ankle angle accuracy, minimal oscillations, and low energy consumption. A set of solutions was obtained with multi-objective optimization algorithms NSGA-II and RVEA to tune the parameters of the active orthosis. The solutions set from RVEA resulted in lower mean and standard deviation values for the oscillations and energy objectives in comparison to the solutions from NSGA-II, while for the MSE objective, NSGA-II obtained lower mean and standard deviation; for the energy consumption objective, the mean score using RVEA is 17% less than with NSGA-II. The orthosis is shown to be robust to differences in initial ankle angles. We observed that it is possible to obtain a broad set of solutions with a good performance during the gait cycle in controlled spaces and that in this application, the RVEA algorithm results in a better option for optimization to balance the objectives.

Radiometric calibration assessments for UAS-borne multispectral cameras: Laboratory and field protocols