Papers by Alessandro Gardi
AIAA Aviation Forum and ASCEND, 2025
Urban Air Mobility (UAM) is poised to transform transportation within densely populated cities by... more Urban Air Mobility (UAM) is poised to transform transportation within densely populated cities by leveraging the third dimension-airspace. Vertical TakeOff and Landing (VTOL) and hybrid VTOL-cruise air vehicles are the most compelling and thus popular configurations for UAM applications due to their operational versatility. However, path planning and guidance in such highly dynamic and GNSS-denied environments are likely to produce suboptimal path and erratic maneuvering commands, due to unreliable positioning and attitude determination. To address this challenge, we propose a robust monocular Visual-Inertial Navigation System (VINS), built upon VINS-Mono. Our approach models the uncertainty in both feature tracking and pose estimation, incorporating this into a Mahalanobis-distance-based outlier rejection strategy using a chi-square test. This enables effective suppression of dynamic features, thereby enhancing the robustness of VTOL and hybrid air vehicles navigation and guidance in UAM scenarios. The verification of proposed approach using public datasets demonstrates that consistently high accuracy and robustness can be attained, even under challenging motion profiles.
IEEE 12th International Workshop on Metrology for AeroSpace, MetroAeroSpace, 2025
Urban Air Mobility (UAM) introduces significant new challenges due to atmospheric boundary layer ... more Urban Air Mobility (UAM) introduces significant new challenges due to atmospheric boundary layer and wake interactions in low-altitude environments. The wind field inhomogeneity due to these phenomena can result in hazardous flight upsets due to the asymmetric thrust and aerodynamic loads induced on the UAM vehicle. To support the study of these risks and the required advances in Flight Control System (FCS) design for Vertical TakeOff and Landing (VTOL) platforms, this paper presents an innovative technique to estimate the local wind field characteristics based on measurements of power drain from the distributed electric VTOL motors equipped with Electronic Speed Controllers (ESC). By fusing these measurements with rotor speed (RPM) sensors experienced by the UAM vehicle propellers, the technique allows to estimate the wind velocity components affecting each rotor and thus the asymmetric load affecting the vehicle. A simulation case study in a representative UAM flow field verifies the validity of the proposed approach and allows us to estimate its performance in these realistic conditions.
IEEE 12th International Workshop on Metrology for AeroSpace, MetroAeroSpace, 2025
In urban canyons, the autonomous positioning and obstacle avoidance capabilities of Uncrewed Aeri... more In urban canyons, the autonomous positioning and obstacle avoidance capabilities of Uncrewed Aerial Vehicles (UAV) are challenged by dense obstructions, causing Non-Line-of-Sight (NLOS) conditions that severely degrade Global Navigation Satellite Systems (GNSS) signals. Current urban UAV operations still rely heavily on manual control and conventional GNSS-Inertial Measurement Unit (IMU) fusion, which lack autonomous obstacle avoidance capabilities and fail to provide precise positioning in GNSS-denied environments. To address these limitations, we propose a novel sensor fusion framework that integrates the Sage-Husa adaptive Kalman Filter (SHKF) with intermittent data from GNSS, IMU, and visual odometry supplied from a Visual-Inertial (VINS)-Fusion algorithm to achieve robust positioning and attitude determination. This enhanced sensor fusion architecture enables a 3DVFH*-based local planner to execute real-time obstacle avoidance and path planning toward the intended destinations. Preliminary verification activities conducted in a high-fidelity Gazebo simulation demonstrate the effective performance of the proposed method in terms of positioning and attitude determination accuracy, while also supporting the optimal reliability and efficiency of the considered obstacle avoidance functionality.
IEEE transactions on aerospace and electronic systems, 2024
Urban Air Mobility (UAM) aims to establish a low-altitude transportation system that operates saf... more Urban Air Mobility (UAM) aims to establish a low-altitude transportation system that operates safely and efficiently to mitigate the increasing ground traffic congestion in densely populated areas. Various aircraft types, including Passenger Aerial Vehicles (PAV) and Unmanned Aerial Vehicles (UAV), will be used to provide UAM services. In this context, a large number of aircraft are expected to operate in close proximity to each other, leading to challenges in terms of communication throughput and interference. To address these challenges, this paper examines UAM communication requirements and the potential applications of cellular networks in the relevant flight environments. UAM wireless connectivity performance is analyzed focusing on co-channel interference and mathematical expressions for the Probability of Coverage (PoC) are derived using stochastic geometry. Based on these premises, the improvements in PoC attainable 0000-0000 © 2022 IEEE using interference mitigation techniques such as Frequency Reuse (FR) and Separation Distance (SD) are investigated. Then, a PoC enhancement algorithm is presented using a combined FR-SD method. Numerical verification case studies are performed in representative conditions, showing that the proposed method is able to mitigate co-channel interference, significantly reducing computational time and increasing spectrum efficiency.
Quantifying the Radiative Impact of Contrails for Cruise Trajectory Planning
Automated manned and unmanned aircraft separation assurance and collision avoidance: A unified approach
Novel automated Communication, Navigation, Surveillance/Air Traffic Management and Avionics (CNS+... more Novel automated Communication, Navigation, Surveillance/Air Traffic Management and Avionics (CNS+A) systems (on airborne and ground systems) allow suitably equipped aircraft (manned and unmanned) to fly user-preferred optimal flight paths, limiting the intervention of human operators to high-level and emergency decisions. The CNS+A systems equipped manned and unmanned aircraft generate 4DT intents that consist of a number of flyable optimal trajectories in order of priority that are subsequently transmitted to the ground-based next generation ATM system via reliable data links. The introduction of automated Separation Assurance and Collision Avoidance (SA and CA) functions in the next generation CNS+A framework has the potential to provide a pathway for manned/unmanned aircraft coexistence in all classes of airspace. A unified approach to cooperative and non-cooperative SA and CA is supported by the translation of navigation and tracking errors to unified range and bearing descriptors. Navigation sensors including Global Navigation Satellite Systems (GNSS), Inertial Measurement Unit (IMU) and vision based sensing are considered in this approach. Errors in the obstacle/intruder tracking measurements are estimated considering a combination of non-cooperative sensors, including active/passive Forward-Looking Sensors (FLS) and acoustic sensors, as well as cooperative systems, including Automatic Dependent Surveillance Broadcast (ADS-B) and Traffic Collision Avoidance System (TCAS). Noncooperative sensors are employed to detect intruders or other obstacles in the aircraft Field of Regard (FOR) when cooperative systems are unavailable to the intruders. Simulation case studies performed in a realistic scenario to assess the SA and CA functions implemented in next generation avionics systems are presented corroborating the validity of the developed mathematical models.
The demand for reliable obstacle avoidance capabilities to ensure safe operation of manned and un... more The demand for reliable obstacle avoidance capabilities to ensure safe operation of manned and unmanned aircraft platforms in proximity of the terrain has led to the development of a number of obstacle detection and warning systems. Among the different technologies proposed for the application, the Light Detection and Ranging (LIDAR) technology employing eye-safe laser sources, advanced electro-optics and mechanical beam-steering components has proven to deliver the highest angular resolution and accuracy performances in a wide range of incidence angles and weather conditions. LIDAR obstacle avoidance systems have become a mature and successful solution for rotorcraft platforms, and current research activities are addressing its extension to other platforms, both civil and military. Small-to-medium size Remotely Piloted Aircraft Systems (RPAS) also employ LOAM sensor, especially for operations in proximity of the ground, further aggravated by the very limited see-and-avoid capabilities of the pilot. In this paper we describe the design and test activities performed to develop and certify the Laser Obstacle Avoidance "Marconi" (LOAM) system. After a brief description of the system architecture as well as of the data processing algorithms, emphasis is given to avoidance trajectory generation and performance estimation models. The evaluation of the avoidance trajectory generation algorithm in realistic scenario is also described. An overview of ground and flight test activities performed on various platforms and their results is also presented. The paper also overviews the future LOAM developments and integration activities with a focus on non-cooperative RPAS Detect-and-Avoid (DAA) applications.
AAM and UAS Collision Avoidance in the Presence of Wind and Wake Turbulence
A Sensor-Centric Approach to Space Traffic Management
A pressing issue and a case for a Space Situational Awareness (SSA) reformation are the current &... more A pressing issue and a case for a Space Situational Awareness (SSA) reformation are the current "operationally" deemed processes and procedures regarding Orbital Conjunction/Collision Assessment. With the growth of orbital traffic and debris, conjunction warnings are increasingly being treated as false alarms due to the high amount of uncertainty associated with current observational data. Building upon previous research, this paper presents a sensor-orientated approach to resident space object position . A mathematical framework is developed that exploits real-time navigation measurements, tracking observables to providing a sound methodology that supports SSA activities including separation assurance and collision avoidance among multiple space objects. In line with envisioned SSA evolutions, the advantage of the method is its ability to accurately represent sensor characteristics in the form of an avoidance volume that is described (and exchanged) in computationally efficient manner, while supporting both top-down and bottom-up approaches to sensor safety assessment and certification. The proposed method is applied to a representative case of on-orbit survellience as well as discussing the approaches implications and evolutions required for future SSA and Space Traffic Management (STM) Cyber-Physical Systems.
Feature article: Certification challenges for next-generation avionics and air traffic management systems
Air traffic is doubling every 15 years, and aviation systems must modernize to address sustainabi... more Air traffic is doubling every 15 years, and aviation systems must modernize to address sustainability challenges. The need to balance capacity, efficiency, safety, and environmental requirements is reflected by the several air traffic management (ATM) and avionics modernization initiatives under way. The major collaborative research programs today are the European Union's Single European Sky ATM Research (SESAR) project and the United States' Next-Generation Air Transportation System (NextGen) led by the Federal Aviation Administration (FAA). Other modernization initiatives include the Collaborative Action for Renovation of Air Traffic Systems in Japan, SIRIUS in Brazil, OneSky in Australia, and similar programs in Canada, China, India, and Russia [1]. The International Civil Aviation Organization (ICAO) has authorized a globally coordinated plan, published as the Global Air Navigation Plan (GANP) [1], to guide the harmonized implementation of communication, navigation, surveillance, and avionics (CNS+A) enhancements across regions and states. In the CNS+A context, aircraft safety is a shared responsibility between airborne and ground-based resources [1]. Hence, this is a safety challenge requiring changes to the current regulatory framework to properly capture the nature of this shared responsibility and the concept of integrated CNS+A systems. Certification of aircraft and ground equipment (hardware and software) and organizational approvals are essential elements to ensure continued and enhanced safety.
Zenodo (CERN European Organization for Nuclear Research), Nov 23, 2013
The availability of powerful eye-safe laser sources and the recent advancements in electro-optica... more The availability of powerful eye-safe laser sources and the recent advancements in electro-optical and mechanical beam-steering components have allowed laser-based Light Detection and Ranging (LIDAR) to become a promising technology for obstacle warning and avoidance in a variety of manned and unmanned aircraft applications. LIDAR outstanding angular resolution and accuracy characteristics are coupled to its good detection performance in a wide range of incidence angles and weather conditions, providing an ideal obstacle avoidance solution, which is especially attractive in military low-level flying platforms such as helicopters and small-size Unmanned Aircraft (UA). In this paper we discuss the integration of the Laser Obstacle Avoidance "Marconi" (LOAM) system on candidate UA platforms. The original LOAM system design and the performed helicopter test activities are summarised, including a brief description of the system architecture and sensor characteristics, together with the system performance models and data processing algorithms for obstacle detection and classification. The paper presents the dynamic modelling and the avoidance trajectory generation algorithm for UA applications. A description of the future planned flight test activities is also included.
Descent 4D trajectory optimisation for curved GNSS approaches
This paper describes the 4-Dimensional Trajectory (4DT) optimisation algorithm implemented to avo... more This paper describes the 4-Dimensional Trajectory (4DT) optimisation algorithm implemented to avoid a variety Global Navigation Satellite System (GNSS) signal degradations predicted by Avionics Based Integrity Augmentation system (ABIA). The paper focusses on descent and initial curved GNSS approach phases in a dense Terminal Manoeuvring Area (TMA) scenario, with multiple aircraft converging on the same short and curved final GNSS approach leg. The reference platform for this study is the Javelin Remotely Piloted Aircraft System (RPAS). The 4DT optimisation algorithm implements three degrees-of-freedom aircraft dynamics models as well as suitable GNSS satellite visibility models based on Global Positioning System (GPS) constellation ephemeris data. Direct transcription methods of the global orthogonal (pseudospectral) collocation family are implemented, generating optimal high-integrity trajectories for curved GNSS approaches in real-time. The optimal trajectories calculated by the pseudospectral method are subsequently processed by control input smoothing and manoeuvre identification algorithms to translate the mathematical optimum into a pilot- /autopilot-flyable and concisely described 4DT intent. The characteristics of the proposed 4DT optimisation algorithm are evaluated in representative simulation case studies targeting short and curved GNSS approaches in dense TMA conditions, showing very satisfactory performance.
UAS in the Terminal Area: Challenges and Opportunities
Encyclopedia of Aerospace Engineering, Jul 18, 2016
This chapter discusses the challenges and opportunities associated with the introduction of unman... more This chapter discusses the challenges and opportunities associated with the introduction of unmanned aircraft systems (UAS) in terminal areas and other airspace regions characterized by high air traffic densities and high levels of air traffic services (ATS). The specificities in terms of jurisdiction and prevalent traffic characteristics are analyzed and discussed to support the identification of operational and equipage requirements for a safe integration of UAS. In particular, as the separation monitoring and deconfliction responsibilities are primarily on the air traffic management (ATM) side, it is clear that communication, navigation, surveillance, ATM, and avionics (CNS+A) equipment play an essential role in this scenario. This is furthermore supported in relation to the very frequent occurrence of potential conflicts, as the deconfliction by ATM relies on accurate and reliable CNS systems. Nevertheless, the higher jurisdiction of ATM operators may also offer an opportunity to UAS developers, as it is shown that less expert processing functions will be required to integrate ATM-assisted sense-and-avoid (SAA) capabilities onboard the UAS.
GNSS Performance Modelling for Positioning and Navigation in Urban Environments
The Global Navigation Satellite System (GNSS) supports a growing number of several Intelligent Tr... more The Global Navigation Satellite System (GNSS) supports a growing number of several Intelligent Transport System (ITS) applications and location based services including collision avoidance, electronic toll collection, fleet management and Unmanned Aircraft System (UAS) navigation. This paper performs a detailed performance analysis of GNSS with a focus on failure modes in urban environments as a critical case study. A guidance-based augmentation strategy based on trajectory optimization is developedwhich accounts for the influence of urban structures on GNSS performance. A simulation case study representative of UAS operations in urban environments was performed as a preliminary assessment to corroborate the developed modules.
Hybrid AI-Based Demand-Capacity Balancing for UAS Traffic Management and Urban Air Mobility
AIAA AVIATION 2021 FORUM, Jul 28, 2021
Cybersecurity Trends in Low-Altitude Air Traffic Management
2022 IEEE/AIAA 41st Digital Avionics Systems Conference (DASC), Sep 18, 2022
Potential of Hybrid Neural Network Local Path Planner for small UAV in Urban Environments
AIAA SCITECH 2023 Forum, Jan 19, 2023
Journal of Aerospace Technology and Management, Feb 26, 2018
This article proposes a novel and effective solution for estimating fatigue life of General Aviat... more This article proposes a novel and effective solution for estimating fatigue life of General Aviation (GA) airframes using fl ight data produced by digital avionics systems, which are being installed or retrofi tted into a growing number of GA aircraft. In the proposed implementation, a fl ight dynamics model is adopted to process the recorded fl ight data and to determine the dynamic loadings experienced by the aircraft. The equivalent loading cycles at fatigue-critical points of the primary structure are counted by means of statistical methods. For validation purposes, the developed approach is applied to fl ight data recorded by a fl eet of Cessna 172S aircraft fi tted with a Garmin G1000 integrated navigation and guidance system. Based on the initial experimental results and the developed uncertainty analysis, the proposed approach provides acceptable estimates of the residual fatigue life of the aircraft, thereby allowing a cost-effective and streamlined structural integrity monitoring solution. Future developments will address the possible adoption of the proposed method for unmanned aircraft structural health monitoring, also considering the accuracy enhancements achievable with advanced navigation and guidance architectures based on Global Navigation Satellite Systems (GNSS), Vision-Based Navigation (VBN) Sensors, Inertial Measurement Units (IMU) and Aircraft Dynamics Model (ADM) augmentation.
arXiv (Cornell University), Jun 2, 2020
In this study, 19 exoplanets were studied. Their photometric observations were obtained from the ... more In this study, 19 exoplanets were studied. Their photometric observations were obtained from the ETD. After performing the data reduction steps, its parameters were obtained through Exofast online software. Then calculated orbital parameters of planets and as a result, the periods of all the planets in this study match comparable with the Extrasolar Planets Encyclopedia. Also, we present Tc and Tdepth obtained from the observations. The location of the host stars in this study was also plotted in the H-R diagram.
The certification challenge of integrated avionics and air traffic management systems
Transport Research Forum, Nov 1, 2016
Aviation must undertake considerable modernisation efforts in an era of steady air traffic growth... more Aviation must undertake considerable modernisation efforts in an era of steady air traffic growth to meet the crucial challenges faced by the industry, which include increasing demand for capacity and efficiency, stronger focus on global aviation safety and greater concerns on minimising adverse effects on the environment. Regulation and certification are vital to ensure high levels of safety and should also evolve harmoniously with the technological developments of Next Generation Avionics and Air Traffic Management (ATM) systems. This paper presents the challenges and opportunities for the evolution of the certification framework, considering the Global Air Navigation Plan (GANP) of International Civil Aviation Organisation (ICAO) and major air transport modernisation programs including, inter alia, the Single European Sky Air Traffic Management Research (SESAR) of Europe, Next Generation Air Transport System (NextGen) of the United States and OneSky of Australia. A critical review is carried out on the existing regulatory frameworks of the concerned aviation authorities namely the European Aviation Safety Agency (EASA), the Federal Aviation Administrator (FAA), the Civil Aviation Safety Authority (CASA) and the ICAO in relation to certification, in order to identify the key areas requiring further developments. Furthermore, a review of current industry standards in relation to hardware and software design, development, test & evaluation together with available standards for safety assessment are also presented, highlighting the outstanding gaps which should be fulfilled to achieve an integrated Communication, Navigation, Surveillance/Air Traffic Management (CNS/ATM) system certification. The paper then proposes a top level framework for integrated CNS/ATM system certification considering airborne as well as non-airborne systems, together with a matrix for means of compliance.
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Papers by Alessandro Gardi