sUAS Swarm Navigation using Inertial, Range Radios and Partial GNSS

Small Unmanned Aerial Systems (sUAS) operations are increasing in demand and complexity. Using multiple cooperative sUAS (i.e. a swarm) can be beneficial and is sometimes necessary to perform certain tasks (e.g., precision agriculture, mapping, surveillance) either independent or collaboratively. However, controlling the flight of multiple sUAS autonomously and in real-time in a challenging environment in terms of obstacles and navigation requires highly accurate absolute and relative position and velocity information for all platforms in the swarm. This information is also necessary to effectively and efficiently resolve possible collision encounters between the sUAS. In our swarm, each platform is equipped with a Global Navigation Satellite System (GNSS) sensor, an inertial measurement unit (IMU), a baro-altimeter and a relative range sensor (range radio). When GNSS is available, its measurements are tightly integrated with IMU, baro-altimeter and range-radio measurements to obtain the platform’s absolute and relative position. When GNSS is not available due to external factors (e.g., obstructions, interference), the position and velocity estimators switch to an integrated solution based on IMU, baro and relative range meas-urements. This solution enables the system to maintain an accurate relative position estimate, and reduce the drift in the swarm’s absolute position estimate as is typical of an IMU-based system. Multiple multi-copter data collection platforms have been developed and equipped with GNSS, inertial sensors and range radios, which were developed at Ohio University. This paper outlines the underlying methodology, the platform hardware components (three multi-copters and one ground station) and analyzes and discusses the performance using both simulation and sUAS flight test data

Conflict-free trajectory optimization with target tracking and conformance monitoring

This is a postprint (author final draft) deposit on institutional repository UPCommons from UPC, thanks to AIAA. Original version can be found on: https://arc.aiaa.org/doi/10.2514/1.C034251This paper proposes an optimization framework that computes conflict-free optimal trajectories in dense terminal airspace, while continuously monitoring trajectory conformance in an effort to improve predictability. The objective is to allow, as much as possible, continuous vertical trajectory profiles without impacting negatively on airspace capacity. Given automatic dependent surveillance–broadcast intent information, the future state of potential intruder aircraft are predicted, and this nominal trajectory is used as a constraint in the ownship trajectory optimization process. In it, a continuous multiphase optimal control problem is solved, taking into account spatial and temporal constraints. Additionally, a linearized Kalman filter keeps track of the target by estimating the deviations of its actual trajectory from its nominal trajectory, issuing a warning when an appropriate threshold is exceeded. This may be due to unexpected events, biases in the performance and weather models, wrong parameter assumptions, etc. An illustrative example is given, based on a computer simulation of two hypothetical trajectories in the Barcelona terminal maneuvering area. The results show how this framework resolves the problem of uncertainties in the trajectory predictions and results in a more efficient conflict resolution.Peer ReviewedPostprint (author's final draft

GNSS Double Differences used as Beacon Landing System for Aircraft Instrument Approach

When using GNSS navigation for final approach guidance of aircraft to a landing site, the only systems currently available are differential GNSS with additional integrity data called augmentation systems. These work well when the landing site is fixed in space and well surveyed. In all other cases, augmentation systems are difficult to use. Here, we propose relative navigation based on GNSS double difference measurement to accomplish the same task, but also onto moving landing platforms or at unsurveyed locations. We call this the Beacon Landing System. Furthermore, we show long term measurement data confirming the sub-meter accuracy and results from flight tests. During the flight test we successfully used the relative navigation for aircraft guidance

Design and Testing of a Vertically Guided High Precision Approach into Salzburg Airport

The approach to landing on runway 33 of Salzburg Airport, Austria is severely impacted by mountainous terrain on the extended runway centerline. This renders all straight-in approaches but those based on Required Navigation Performance (RNP) Authorization Required (AR) impossible. Only the high navigation accuracy available under RNP AR minimizes the required obstacle protection areas sufficiently to be not penetrated by terrain. The combination of RNP AR and Localizer Performance with Vertical guidance (LPV) makes it furthermore possible to use a more precise angular guidance for the final approach. In Salzburg, this enables a reduction of the decision height from 368 ft to 218 ft above aerodrome level as critical terrain and obstacles now fall outside of the protection areas. A Level D full flight simulator test with an Airbus A350 showed that advanced RNP 0.1 coding is sufficient to achieve RNP 0.1 performance under all permitted environmental conditions

Usability Evaluation of Indicators of Energy-Related Problems in Commercial Airline Flight Decks

A series of pilot-in-the-loop flight simulation studies were conducted at NASA Langley Research Center to evaluate indicators aimed at supporting the flight crews awareness of problems related to energy states. Indicators were evaluated utilizing state-of-the-art flight deck systems such as on commercial air transport aircraft. This paper presents results for four technologies: (1) conventional primary flight display speed cues, (2) an enhanced airspeed control indicator, (3) a synthetic vision baseline that provides a flight path vector, speed error, and an acceleration cue, and (4) an aural airspeed alert that triggers when current airspeed deviates beyond a specified threshold from the selected airspeed. Full-mission high-fidelity flight simulation studies were conducted using commercial airline crews. Crews were paired by airline for common crew resource management procedures and protocols. Scenarios spanned a range of complex conditions while emulating several causal factors reported in recent accidents involving loss of energy state awareness by pilots. Data collection included questionnaires administered at the completion of flight scenarios, aircraft state data, audio/video recordings of flight crew, eye tracking, pilot control inputs, and researcher observations. Questionnaire response data included subjective measures of workload, situation awareness, complexity, usability, and acceptability. This paper reports relevant findings derived from subjective measures as well as quantitative measures

Emerging Technologies for Airplane State Awareness and Prediction

Loss of control in flight (LOC-I) is consistently the leading cause of fatal aircraft accidents. A study of LOC accidents and incidents, commissioned by the Commercial Aviation Safety Team (CAST) identified a growing trend in loss of Airplane State Awareness (ASA) by the flight crew. This has led to recommended safety enhancements that include flight deck technologies with the potential of enhancing flight crew awareness of airplane energy state. The goal of this research is to develop and evaluate technologies that predict and assess the future aircraft energy state and auto-flight configuration, and provide appropriate alerting to anticipated problematic auto-flight inputs, with the aim of enhancing pilots situational awareness

Attribution of physical complaints to the air disaster in Amsterdam by exposed rescue workers: an epidemiological study using historic cohorts

BACKGROUND: In 1992 a cargo aircraft crashed into a residential area of Amsterdam. A troublesome aftermath followed, with rumors on potential toxic exposures and health consequences. Health concerns remained even though no excess morbidity was predicted in retrospective risk evaluations. This study aimed to assess to what extent the rescue workers attribute long-term physical complaints to this disaster, including its aftermath, and to examine associations between such attribution and types of exposure and background variables. METHODS: Historic cohort study that collected questionnaire data on occupational disaster exposure, attribution of physical complaints, and background variables on average 8.5 years post-disaster. For the present study the workers who were exposed to the disaster were selected from the historic cohort, i.e. the professional firefighters (n = 334), police officers (n = 834), and accident and wreckage investigators (n = 241) who performed disaster-related tasks. RESULTS: Across the three occupational groups, a consistent percentage (ranging from 43% to 49%) of exposed workers with long-term physical complaints attributed these to the disaster, including its aftermath. Those with more physical complaints attributed these to a stronger degree. Multivariate logistic regression analyses showed that attribution was significantly more often reported by firefighters who rescued people, and by police officers who reported the identification and recovery of or search for victims and human remains, clean-up, or security and surveillance of the disaster area; who witnessed the immediate disaster scene; who had a close one affected by the disaster; and who perceived the disaster as the worst thing that ever happened to them. Age, sex and educational level were not significantly associated with attribution. CONCLUSION: This study provides further cross-sectional evidence for the role of causal attribution in post-disaster subjective physical health problems. After on average 8.5 years, almost a third (32%) of all the exposed workers, and almost half (45%) of the exposed workers with physical complaints, attributed these complaints to the disaster, including its aftermath. The similarity of the results across the occupational groups suggests a general rather than an occupation-specific attribution process. Longitudinal studies are needed to determine whether causal disaster attribution leads to persistence of post-disaster complaints and health care utilization

Teratogenicity of depleted uranium aerosols: A review from an epidemiological perspective

BACKGROUND: Depleted uranium is being used increasingly often as a component of munitions in military conflicts. Military personnel, civilians and the DU munitions producers are being exposed to the DU aerosols that are generated. METHODS: We reviewed toxicological data on both natural and depleted uranium. We included peer reviewed studies and gray literature on birth malformations due to natural and depleted uranium. Our approach was to assess the "weight of evidence" with respect to teratogenicity of depleted uranium. RESULTS: Animal studies firmly support the possibility that DU is a teratogen. While the detailed pathways by which environmental DU can be internalized and reach reproductive cells are not yet fully elucidated, again, the evidence supports plausibility. To date, human epidemiological data include case examples, disease registry records, a case-control study and prospective longitudinal studies. DISCUSSION: The two most significant challenges to establishing a causal pathway between (human) parental DU exposure and the birth of offspring with defects are: i) distinguishing the role of DU from that of exposure to other potential teratogens; ii) documentation on the individual level of extent of parental DU exposure. Studies that use biomarkers, none yet reported, can help address the latter challenge. Thoughtful triangulation of the results of multiple studies (epidemiological and other) of DU teratogenicity contributes to disentangling the roles of various potentially teratogenic parental exposures. This paper is just such an endeavor. CONCLUSION: In aggregate the human epidemiological evidence is consistent with increased risk of birth defects in offspring of persons exposed to DU