Prior Flight Research Articles

Guidance and Control Systems for Multi-Satellite Assembly using Decentralized Nonlinear Model Predictive Control

Assembly of multiple satellites enables to replace the functionality of one large satellite by multiple smaller satellites for many applications and missions such as formation flying, multi robot planetary exploration, and satellites warms. In this paper, a novel decentralized guidance and control (G&C) algorithms is developed for multi-satellite assembly in proximity operations based on Non linear Model Predictive Control (NMPC).The two-body relative motion model is utilized in designing the G&C systems. Decentralization avoids the single point of failure (i.e., the leader satellite), which enhances the robustness of the system. The NMPC is utilized because of itsability to handle the output and the input constraints. Collision avoidance is ensured by defining a quadratic constraint equation. Moreover, the optimal thrust vector is computed while considering the control input saturation. The mission is to assemblemultiple satellites into a cubic configuration, where each satellite approaches a cube vertex. Totes the algorithms’ effectiveness and to increase the level of confidence prior flight, the proposed closed-loop G&C system is demonstrated by using MATLAB andtested for a relative motion model with J2 perturbation. The simulation results showsmooth conversion of all satellites to the target while satisfying the input and outputconstraints.

Longitudinal MRI-visible perivascular space (PVS) changes with long-duration spaceflight.

Humans are exposed to extreme environmental stressors during spaceflight and return with alterations in brain structure and shifts in intracranial fluids. To date, no studies have evaluated the effects of spaceflight on perivascular spaces (PVSs) within the brain, which are believed to facilitate fluid drainage and brain homeostasis. Here, we examined how the number and morphology of magnetic resonance imaging (MRI)-visible PVSs are affected by spaceflight, including prior spaceflight experience. Fifteen astronauts underwent six T1-weighted 3 T MRI scans, twice prior to launch and four times following their return to Earth after ~ 6-month missions to the International Space Station. White matter MRI-visible PVS number and morphology were calculated using an established, automated segmentation algorithm. We validated our automated segmentation algorithm by comparing algorithm PVS counts with those identified by two trained raters in 50 randomly selected slices from this cohort; the automated algorithm performed similarly to visual ratings (r(48) = 0.77, p < 0.001). In addition, we found high reliability for four of five PVS metrics across the two pre-flight time points and across the four control time points (ICC(3,k) > 0.50). Among the astronaut cohort, we found that novice astronauts showed an increase in total PVS volume from pre- to post-flight, whereas experienced crewmembers did not (p = 0.020), suggesting that experienced astronauts may exhibit holdover effects from prior spaceflight(s). Greater pre-flight PVS load was associated with more prior flight experience (r = 0.60–0.71), though these relationships did not reach statistical significance (p > 0.05). Pre- to post-flight changes in ventricular volume were not significantly associated with changes in PVS characteristics, and the presence of spaceflight associated neuro-ocular syndrome (SANS) was not associated with PVS number or morphology. Together, these findings demonstrate that PVSs can be consistently identified on T1-weighted MRI scans, and that spaceflight is associated with PVS changes. Specifically, prior spaceflight experience may be an important factor in determining PVS characteristics.

Adaptive control of hypersonic vehicles with unknown dynamics based on dual network architecture

The difficulty of obtaining accurate dynamical models of hypersonic flight has been generally recognized, and modeling inaccuracy can severely deteriorate the performance of the flight control systems. To address this issue, an adaptive control approach using two neural networks (NNs) is proposed with the aim of achieving precise and robust control for hypersonic flight when unknown dynamics are involved. Different from the existing adaptive control methods, two NNs are developed in this paper to learn the forward and inverse dynamics of hypersonic flight with guaranteed convergence. Particularly, this study focuses on the following three contributions. First, an iterative model learning algorithm is proposed to train the first NN to approximate the unmodeled system dynamics and achieve accurate observations of flight responses and unknown dynamics. Second, an iterative controller learning algorithm is proposed to guide the second NN to learn the control inputs from prior flight data and improve the dynamic performance of the adaptive controller. Third, an adaptive NN-based controller for trajectory tracking is developed combining the above two NNs. Simulations are provided to substantiate the effectiveness of the proposed techniques and demonstrate the excellent adaptability and robustness of the controller.

Ranking Pictorial Cues in Simulated Landing Flares

Abstract. Two-dimensional pictorial cues provide depth perception information that help pilots initiate the landing flare 10–20 ft from the ground. Although prior studies established the importance of three specific cues, they failed to rank-order their importance. This exploratory paper presents two studies, with different methodologies, that examine the effect of these pictorial cues on depth perception. In both studies, participants experienced simulated scenarios and attempted to initiate the landing flare 10–20 ft above ground level. Study 1 included 121, and Study 2 included 141, naïve participants with no prior flight experience. Combined, the findings suggest that flight instructors, training literature, and airport architects should emphasize the runway above all other pictorial cues.

On the relevance of data science for flight delay research: a systematic review

ABSTRACT Flight delays are a significant problem for society as they evenly impair airlines, transport companies, air traffic controllers, facility managers, and passengers. Studying prior flight data is an essential activity for every player involved in the air transportation system. Besides, developing accurate prediction models for flight delays is a crucial component of the decision-making process. Prescribing actions to solve on-going delays is an even challenging task due to the air transportation system complexity. In this regard, this paper presents a thorough literature review of data science techniques used for investigating flight delays. This work proposes a taxonomy and compiles the initiatives used to address the flight delay studies. It also offers a systematic literature review that describes the trends of the field and methods to analyse the applicability of newly proposed methods.

The Use of Unmanned Aerial Vehicles (UAVs) in Slope Stability Assessment

The use and applications of unmanned aerial vehicles (UAVs) in geotechnical engineering is rapidly growing, leading to changes in the way that data is acquired, analyzed and processed. UAVs can reach areas previously inaccessible via ground or helicopter, while also being quickly deployed. Cameras are the current standard for data collection and 3D model creation.&#x0D; There are multiple types of UAV’s currently available. Quadcopters can take off and land in spatially constrained areas, but carry a small stabilized camera producing low quality models. Octocopters permit an increased payload, so a higher quality camera can be attached, allowing for increased model accuracy. Flight time is reduced by the additional weight. Fixed wing UAVs create higher quality photogrammetry models, and are commonly deployed over large surface areas. Transport Canada certification must be approved prior to any flights occurring for research or work. A detailed application must be created, including a flight plan and demonstration of prior flight experience.&#x0D; At the White Canyon site in B.C., a Phantom 4 Quadcopter was flown for geotechnical analysis of a complex geometry slope, which has previously been studied for several years. The terrain has occluded the data available from the ground or from permissible helicopter flight paths. Therefore, detailed information from the slope has not been previously available. The process of using a UAV to obtain these data sets, to develop a full 3D model of these areas of the slope is discussed, considering the accuracy and quality of the data available.

Transforming Civil Helicopters into Personal Aerial Vehicles: Modeling, Control, and Validation

This paper presents the implementation of robust control strategies to augment an identified state-space model of a civil light helicopter. The aim of this study is to augment the helicopter model to achieve response types and handling qualities of a new category of aircraft called personal aerial vehicles, which can be flown even by inexperienced pilots. Two control methods are considered to augment the helicopter model, and synthesis. Differences, advantages, and limitations of the implemented control architectures are highlighted with respect to the personal aerial vehicle reference dynamics in terms of robust stability, nominal performance, and handling qualities. Furthermore, results are presented of an experiment performed with the Max Planck Institute CyberMotion Simulator. The aim of the experiment is to assess the discrepancies between the two augmented systems and the personal aerial vehicle reference model. The experiment consists of piloted closed-loop control tasks performed by participants without any prior flight experience. The results show that the two implemented augmented systems allow inexperienced pilots to achieve workload and performance levels comparable to those defined for personal aerial vehicles.

Performance Evaluation of Alternative Relative Orientation Procedures for UAV-based Imagery with Prior Flight Trajectory Information

Abstract. Thanks to recent advances at the hardware (e.g., emergence of reliable platforms at low cost) and software (e.g., automated identification of conjugate points in overlapping images) levels, UAV-based 3D reconstruction has been widely used in various applications. However, mitigating the impact of outliers in automatically matched points in UAV imagery, especially when dealing with scenes that has poor and/or repetitive texture, remains to be a challenging task. In spite of the fact that existing literature has already demonstrated that incorporating prior motion information can play an important role in increasing the reliability of the matching process, there is a lack of methodologies that are mainly suited for UAV imagery. Assuming the availability of prior information regarding the trajectory of a UAV-platform, this paper presents a two-point approach for reliable estimation of Relative Orientation Parameters (ROPs) of UAV-based images. This approach is based on the assumption that the UAV platform is moving at a constant flying height while maintaining the camera in a nadir-looking orientation. For this flight scenario, a closed-form solution that can be derived using a minimum of two pairs of conjugate points is established. In order to evaluate the performance of the proposed approach, experimental tests using real stereo-pairs acquired from different UAV platforms have been conducted. The derived results from the comparative performance analysis against the Nistér five-point approach demonstrate that the proposed two-point approach is capable of providing reliable estimate of the ROPs from UAV-based imagery in the presence of poor and/or repetitive texture with high percentage of matching outliers.

Performance Evaluation of Alternative Relative Orientation Procedures for UAV-based Imagery with Prior Flight Trajectory Information

Thanks to recent advances at the hardware (e.g., emergence of reliable platforms at low cost) and software (e.g., automated identification of conjugate points in overlapping images) levels, UAV-based 3D reconstruction has been widely used in various applications. However, mitigating the impact of outliers in automatically matched points in UAV imagery, especially when dealing with scenes that has poor and/or repetitive texture, remains to be a challenging task. In spite of the fact that existing literature has already demonstrated that incorporating prior motion information can play an important role in increasing the reliability of the matching process, there is a lack of methodologies that are mainly suited for UAV imagery. Assuming the availability of prior information regarding the trajectory of a UAV-platform, this paper presents a two-point approach for reliable estimation of Relative Orientation Parameters (ROPs) of UAV-based images. This approach is based on the assumption that the UAV platform is moving at a constant flying height while maintaining the camera in a nadir-looking orientation. For this flight scenario, a closed-form solution that can be derived using a minimum of two pairs of conjugate points is established. In order to evaluate the performance of the proposed approach, experimental tests using real stereo-pairs acquired from different UAV platforms have been conducted. The derived results from the comparative performance analysis against the Nistér five-point approach demonstrate that the proposed two-point approach is capable of providing reliable estimate of the ROPs from UAV-based imagery in the presence of poor and/or repetitive texture with high percentage of matching outliers.

Handling Qualities Requirements for Future Personal Aerial Vehicles

This paper describes research to develop handling qualities guidelines and criteria for a new category of aircraft: the personal aerial vehicle, which it is envisaged will demand no more skill to fly than that associated with driving a car today. Testing of concept personal aerial vehicle response types has been conducted with inexperienced “pilots” ranging from private pilot’s license holders through to those with no prior flight experience. The objective was to identify, for varying levels of flying skill, the personal aerial vehicle response type requirements that will ensure safe and precise flight. Conventional rotorcraft response types such as “rate command”, “attitude command/attitude hold” are unsuitable for likely personal aerial vehicle pilots. However, response types such as “translational rate command” and “acceleration command, speed hold” permit “flight-naïve” pilots to perform demanding tasks repeatably and with the required precision.

1302 フライトシミュレータによる航空機操縦技量解析手法の研究

We analyze pilot flight technique using the fixed base flight simulator of the Suzuki-Tsuchiya laboratory at The University of Tokyo. We look at pitch control style and input frequencies in particular, and identified differences between professional pilots and students without prior flight experience. Also students with a lot of experience playing the Microsoft Flight Simulator game show a typical control style. In addition we can distinguish control styles between instrument flight and visual flight. We provided simulator training to a number of students and followed them over a period of a few months. The analysis of their data shows that their control input frequency increases, and resembles the professional pilot's control style more and more. In addition, we found trainees develop a characteristic change in the pupil diameter just before landing comparable with professional pilots. We believe these findings are an important step towards the objective evaluation of trainee pilots.

Simplified analytical model for predicting the temperature of balloon on high-altitude

This paper outlines an analytical model to predict the temperature of fully-inflated balloon on float at high altitude in stratosphere. Simplified radiative and convective heat transfer models are developed to estimate absorption and emission heat of balloon film and lifting gas within balloon. Thermal equilibrium equations for the balloon system in the day time and night time are derived by incorporating radiative and convective heat transfer models. The new model is applied to calculate the day and night temperatures of the balloon system on float at a high-altitude in stratosphere and reasonable correlation is achieved between the predictions obtained from new models and from prior flight testing data, demonstrating the effective use of the proposed models.

Effects of Microgravity on the Virulence ofSalmonellaTowardCaenorhabditis elegans

To evaluate the effects of microgravity on virulence genes in Salmonella, we studied the ability of various Salmonella deletion mutants to kill wild-type Caenorhabditis elegans nematodes at the larval and adult stages. Simultaneous studies were performed utilizing spaceflight, clinorotation, and static ground controls. Nematodes, Salmonella, and growth media were separated until exposed to true or simulated microgravity, and then mixed and grown for 48 h. Experiments were terminated by paraformaldehyde fixation, and optical density measurements were used to assay residual microorganisms. Prior flight in space led to reduced virulence of wild-type Salmonella when subsequently evaluated in a ground-based virulence assay with carefully matched inocula for never-flown Salmonella controls. However, when the virulence assay was conducted in spaceflight, there was only a minimal change in the virulence of wild-type Salmonella toward C. elegans. Deletion of pipA, a gene in Salmonella pathogenicity island-5, reduced Salmonella virulence toward wild-type and Tol1-deletion L2 larvae in spaceflight but had no effect on virulence for Tol1-deletion adult worms in spaceflight. PipA-deletion Salmonella were also less virulent toward wild-type L2 larvae in clinorotation, but showed a paradoxical increased virulence toward Tol1-deletion L2 larvae in clinorotation.

Trajectory deconfliction with constraint programming

AbstractAs acknowledged by the SESAR (Single European Sky ATM (Air Traffic Management) Research) program, current Air Traffic Control (ATC) systems must be drastically improved to accommodate the predicted traffic growth in Europe. In this context, the Episode 3 project aims at assessing the performance of new ATM concepts, like 4D-trajectory planning and strategic deconfliction.One of the bottlenecks impeding ATC performances is the hourly capacity constraints defined on each en-route ATC sector to limit the rate of aircraft. Previous works were mainly focused on optimizing the current ground holding slot allocation process devised to satisfy these constraints. We propose to estimate the cost of directly solving all conflicts in the upper airspace with ground holding, provided that aircraft were able to follow their trajectories accurately.We present a Constraint Programming model of this large-scale combinatorial optimization problem and the results obtained with the FaCiLe (Functional Constraint Library). We study the effect of uncertainties on the departure time and estimate the cost of improving the robustness of our solutions with the Complete Air Traffic Simulator (CATS). Encouraging results were obtained without uncertainty but the costs of robust solutions are prohibitive. Our approach may however be improved, for example, with a prior flight level allocation and the dynamic resolution of remaining conflicts with one of CATS’ modules.

The education of attention as explanation of variability of practice effects: Learning the final approach phase in a flight simulator.

The present study reports two experiments in which a total of 20 participants without prior flight experience practiced the final approach phase in a fixed-base simulator. All participants received self-controlled concurrent feedback during 180 practice trials. Experiment 1 shows that participants learn more quickly under variable practice conditions than under constant practice conditions. This finding is attributed to the education of attention to the more useful informational variables: Variability of practice reduces the usefulness of initially used informational variables, which leads to a quicker change in variable use, and hence to a larger improvement in performance. In the practice phase of Experiment 2 variability was selectively applied to some experimental factors but not to others. Participants tended to converge toward the variables that were useful in the specific conditions that they encountered during practice. This indicates that an explanation for variability of practice effects in terms of the education of attention is a useful alternative to traditional explanations based on the notion of the generalized motor program and to explanations based on the notions of noise and local minima.

The Challenge of Uncoupled Motion: Duration of Cognitive and Physiological Aftereffects

This study aimed to document the cognitive aftereffects of exposure to uncoupled motion and the time course of recovery from these aftereffects. Uncoupled motion refers to a situation in which an individual is simultaneously exposed to two asynchronous motions, either real or virtual. These environments are a challenge for designers because technology that is supposed to increase the user's task performance may actually lead to decreased task performance. In the study, 11 male participants, (median age =32 years) with prior flight experience (median=600 hr) were exposed to an uncoupled motion environment consisting of a flight simulator on a vertically oscillating platform. Participants completed a cognitive test battery, a balance test, and a dynamic visual acuity test preexposure, immediately postexposure, and 2, 4, 6, 8, and 24 hr postexposure. The uncoupled motion scenario led to significant cognitive aftereffects that cannot be solely attributed to motion sickness. These aftereffects lasted between 2 and 4 hr postexposure. The scenario generated some physiological aftereffects that lasted between 1 and 2 hr postexposure. However, it is likely that these aftereffects can be attributed to motion sickness. Uncoupled motion can cause unappreciated effects, such as degraded cognitive performance. System designs that create uncoupled motion need to be evaluated for the potential to generate operator impairment, and designs should be modified to minimize this potential wherever possible. When redesign is not possible, system-use guidelines should be developed to minimize impairment. The current results suggest operators avoid performing cognitively demanding tasks for at least 2 hr postexposure.

The development of self-efficacy during aviation training

Given that self-efficacy has been shown to be positively related to training outcomes, a better understanding of factors that affect self-efficacy in complex training contexts is needed. This study examined the development of self-efficacy in a flight-training programme. Results indicate that training performance and self-esteem predicted self-efficacy for post-training flight performance. Furthermore, prior flight experience moderated the relationships between training performance and self-efficacy, and between self-esteem and self-efficacy. Implications regarding the development of self-efficacy and the design of training programmes are discussed. Copyright © 2000 John Wiley & Sons, Ltd.

Thermocapillary migration of bubbles and drops at moderate to large Marangoni number and moderate Reynolds number in reduced gravity

Results from experiments on the thermocapillary migration of air bubbles and Fluorinert drops in a Dow–Corning silicone oil aboard a NASA Space Shuttle mission are presented and discussed. The experiments cover a wider range of Marangoni and Reynolds numbers than that attained in a prior flight experiment. The data are consistent with earlier results, and are compared with theoretical predictions. Large air bubbles were found to deform slightly in shape to oblate spheroids while the deformation of even the largest drops was within the uncertainty of the size measurements.

Ada and real-time robotics: lessons learned

The Supervisory Telerobotics Laboratory (Steler) at the Jet Propulsion Laboratory (JPL) has developed a prototype telerobotic system to demonstrate the type of technology that will be used aboard Space Station Freedom Although the concept of telerobotics for space exploration is not new, the Steler system broke new ground in its demonstration of the feasibility of a local-remote architecture, including ground-remote control, for space applications. A remote space environment poses some interesting computational challenges to ground-remote control of space applications. A remote site has limited computation facilities, is burdened by minimal bandwidth and by round-trip communication delays of as much as 8 seconds, and yet is expected to respond quickly, predictably, and with recoverability to any anomalous situation. Additional design constraints are imposed by NASA's limitations on software, including on-board programs for the robot, being uploaded to the remote site without prior flight qualification. The authors discuss the use of Ada to meet the computational requirements of this project.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>