Mission Tasks Research Articles

Autonomous Vision-Based Aerial Grasping for Rotorcraft Unmanned Aerial Vehicles.

Autonomous vision-based aerial grasping is an essential and challenging task for aerial manipulation missions. In this paper, we propose a vision-based aerial grasping system for a Rotorcraft Unmanned Aerial Vehicle (UAV) to grasp a target object. The UAV system is equipped with a monocular camera, a 3-DOF robotic arm with a gripper and a Jetson TK1 computer. Efficient and reliable visual detectors and control laws are crucial for autonomous aerial grasping using limited onboard sensing and computational capabilities. To detect and track the target object in real time, an efficient proposal algorithm is presented to reliably estimate the region of interest (ROI), then a correlation filter-based classifier is developed to track the detected object. Moreover, a support vector regression (SVR)-based grasping position detector is proposed to improve the grasp success rate with high computational efficiency. Using the estimated grasping position and the UAV?Äôs states, novel control laws of the UAV and the robotic arm are proposed to perform aerial grasping. Extensive simulations and outdoor flight experiments have been implemented. The experimental results illustrate that the proposed vision-based aerial grasping system can autonomously and reliably grasp the target object while working entirely onboard.

Cost minimization of real-time mission for software systems with rejuvenation

This paper considers the optimal rejuvenation policy problem for software systems performing real-time tasks. Due to software aging, the system performance deteriorates with time eventually leading to the system crash, which can be catastrophic for critical applications. To prevent the system crash or minimize its occurrence probability, software rejuvenation has been widely adopted for counteracting the software aging effect but at the cost of extra system overhead and downtime. We derive the optimal state-based rejuvenation policy minimizing the total expected mission cost for software aging systems subject to multiple performance degradation states. The solution encompasses an event transition-based numerical method that assesses the total expected mission cost of a real-time task, covering penalty cost from the mission failure, operation cost of running the mission software and the expected rejuvenation cost. The proposed cost evaluation model can accommodate arbitrary types of state transition time distributions. The suggested model also allows simultaneous evaluations of other system performance metrics including the probability of the successful task completion (i.e., mission reliability) and conditional expected mission completion time given a successful mission task. Examples are presented to demonstrate the proposed methodology and optimizations. Effects of different parameters on the rejuvenation optimization solution are also investigated.

Evaluation of atomic oxygen effects on nano-coated carbon-carbon structures for re-entry applications

Since the beginning of Space Age, the re-entry phase represents a crucial task for both manned and unmanned aerospace missions. Along with high temperatures and plasma created by the spacecraft/atmosphere dramatic interaction, several issues must be considered in order to use new technologies and materials for re-entry systems. In particular, the effects of space environment due to ultraviolet (UV) and atomic oxygen (AO) have to be taken into account, in order to design and realize aerospace structures useful also for long duration missions. Such damaging factors, in fact, affect the spacecraft outer surfaces by degrading the thermo-mechanical properties of the materials designed to withstand re-entry conditions, thus frustrating their specific effectiveness. Carbon/Carbon (C/C) composites are widely used for high temperatures applications, including Thermal Protection Systems (TPS) for re-entry vehicles. In this work, a treatment of artificial aging was performed over in-house produced C/C material by means of AO ground facility at the Aerospace Systems Laboratory (LSA) of Sapienza University of Rome, evaluating erosion rate and surface oxides creation due to UV + AO irradiation. The experimental test was carried out setting the AO generator at a fluence of 8.7 × 1020 atoms/cm2, for an exposure time of 3000 equivalent sun hours. The material involved was manufactured by a customized vapor infiltration process; moreover, a protective coating was applied by using an aluminum oxide varnish charged with silicon di-oxide nano-spheres. The effect of coating is established by comparing with the results obtained for the uncoated material; an insight about the coating degradation due to the exposure is then assessed by morphological and chemical analyses.

Initial job analysis of military embedded behavioral health services: Tasks and essential competencies

ABSTRACT Utilization of mental health personnel assigned to operational military units is an area of growth for the US military. What activities they perform, how requirements may differ from working in clinical settings, and how to select and train for these types of positions is still poorly understood. A job analysis was conducted of Air Force mental health providers and enlisted technicians embedded in special operations, intelligence, and high-risk training units. Participants rated 27 tasks on frequency, importance, difficulty, and risks, as well as the importance of 37 knowledge, skills, and abilities (KSAs), with differentiation between KSAs that may be trained versus those that must be present to be assigned to the embedded position. Tasks reflected 4 areas of activity: unit embedding/engagement, behavioral health consultation and support, performance optimization activities, and operational mission tasks. Tasks varied by professional training (psychologist, social worker, enlisted technician) and unit type. The KSAs rated as most important were ethical judgment and ability to manage complex relationships and boundaries while working outside of a clinic, strong interpersonal skills with appropriate assertiveness to advocate for safe, effective courses of action, and understanding of unit missions and organizational dynamics. Results have implications for job design, selection criteria, professional disciplines with KSAs necessary to unit-specific tasks, and training of personnel for integrated operational support positions.

Hearing protection devices and methods used for their evaluation: A military perspective

Introduction: Soldiers are regularly exposed to potentially harmful noise such as the constant noise of transport vehicle engines and the impulse noise of weapons. Impulse noise can be particularly hazardous, especially, for example, the high-intensity noise of artillery or shoulder-fired projectile launchers. After administrative and engineering controls, hearing protection devices (HPDs) are a cornerstone of hearing conservation programs. Yet selecting the appropriate protection for the various mission tasks must be done with care. HPDs can range from simple earplugs to high-tech options. Methods: Methods of characterizing the attenuation of HPDs against high-level impulse noise are complex and evolving. Results: For the soldier, the need to balance the degree of measured sound attenuation against interference with other auditory abilities – such as the need to hear soft sounds, to understand commands, or to localize sound – is a common dilemma. Discussion: This article outlines some of the challenges of assessing and choosing HPDs that keep soldiers safe from noise exposure with a view to helping those new to hearing conservation understand more about this important subject.

Prediction of Planetary Mission Task Performance for Long-Duration Spaceflight.

This study aimed to determine values and ranges for key aerobic fitness variables that can individually map the level of success for planetary mission tasks performance for long-duration spaceflight, with the goal to develop a predictor-testing model that can be performed with in-flight equipment. We studied a group of 45 men and women who completed a series of mission-critical tasks: a surface traverse task and a hill climb task. Participants performed each mission task at a low and moderate intensity designed to elicit specific metabolic responses similar to what is expected for ambulation in lunar and Martian gravities, respectively. Aerobic fitness was characterized via cycling and rowing V˙O2peak, ventilatory threshold (VT), and critical power. Logistic regression and receiver operating characteristic curve analysis were used to determine the cutoff thresholds for each aerobic fitness parameter that accurately predicted task performance. The participants of this study were characterized by a range of cycling V˙O2peak from 15.5 to 54.1 mL·kg·min. A V˙O2peak optimal cutoff values of X and Y mL·kg·min were identified for the low- and moderate-intensity surface traverse tasks, respectively. For the low- and moderate-intensity hill climb test, the optimal V˙O2peak cutoff values were X and Y mL·kg·min, respectively. VT and critical power also showed high sensitivity and specificity for identifying individuals who could not complete the mission tasks. In summary, we identified aerobic fitness thresholds below which task performance was impaired for both low- and moderate-intensity mission-critical tasks. In particular, cycling V˙O2peak, VT, and rowing CP could each be used to predict task failure.

An automatic system for a helicopter autopilot performance evaluation

PurposeThe purpose of this paper is to elaborate and develop an automatic system for automatic flight control system (AFCS) performance evaluation. Consequently, the developed AFCS algorithm is implemented and tested in a virtual environment on one of the mission task elements (MTEs) described in Aeronautical Design Standard 33 (ADS-33) performance specification.Design/methodology/approachControl algorithm is based on the Linear Quadratic Regulator (LQR) which is adopted to work as a controller in this case. Developed controller allows for automatic flight of the helicopter via desired three-dimensional trajectory by calculating iteratively deviations between desired and actual helicopter position and multiplying it by gains obtained from the LQR methodology. For the AFCS algorithm validation, the objective data analysis is done based on specified task accomplishment requirements, reference trajectory and actual flight parameters.FindingsIn the paper, a description of an automatic flight control algorithm for small helicopter and its evaluation methodology is presented. Necessary information about helicopter dynamic model is included. The test and algorithm analysis are performed on a slalom maneuver, on which the handling qualities are calculated.Practical implicationsDeveloped automatic flight control algorithm can be adapted and used in autopilot for a small helicopter. Methodology of evaluation of an AFCS performance can be used in different applications and cases.Originality/valueIn the paper, an automatic flight control algorithm for small helicopter and solution for the validation of developed AFCS algorithms are presented.

Optimal autonomous multirotor motion planning in an obstructed environment

This paper addresses a methodology for autonomous motion planning of multirotor aircraft in obstructed environments. The control strategy allows the vehicle to online generate quasi-optimal trajectories with limited computational load while performing collision avoidance tasks. The problem is formulated in a model-predictive control architecture in which motion planning and trajectory tracking processes are solved separately. The first process is based on a spline path planning approach to generate smooth and safe trajectories. The second process elaborates trajectory inputs in terms of commanded thrust magnitude and desired attitude rates in order to steer the vehicle during the mission task. Results of both numerical simulations and, for the first time, an experimental validation are provided in order to assess the performance of the approach in the presence of external disturbances and unmodeled dynamics, provided adequate time horizon and update frequency are selected for the numerical optimization algorithm.

Developing a Linux-based nanosatellite on-board computer: Flight results from the Aalto-1 mission

The on-board computers of a spacecraft handle telecommands sent by the ground, provide telemetry to the ground, process on-board data, and control the spacecraft platform and payloads. A spacecraft may have one or several on-board computers that handle different tasks. On -board software often makes use of specialized real-time operating systems and is usually tailored to the needs of each mission, leading to software projects spanning several years. Additionally, often only parts of the developed software can be used in following missions, demanding a new long software project for the new mission -even when much of the functionality may be very similar from one mission to another. One method to facilitate software reuse is to use existing off the -shelf software modules to accomplish many of the mission tasks while only writing a small portion of mission -specific application code. One way to achieve this, used especially by universities and "new space" companies, has been to use embedded Linux [1]. However, only some of these projects have published how they built their Linux-based on -board software systems. This article describes the development, design, initial fl ight results, and lessons learned of the Linux-based on -board computer (OBC) of Aalto-1.

다항식을 이용한 비행경로생성 및 추종제어에 관한 연구

In this paper, we have studied on the flight path generation using polynomial and the flight path tracking control using guidance law, speed hold system, ACAH (Attitude Command Attitude Hold) system. The modeling section of the flight path is divided into five regions, and each region is modeled by a 7SUPth/SUP order polynomial. The flight paths were defined as maneuver library. MTEs (Mission Task Elements) of aeronautical design standard (ADS)-33 have been used to construct the Maneuver library. The Line-of-Sight(LOS) method and classical control method were applied to design the guidance law, speed hold system, and ACAH system for tracking the flight path. Simulation was performed to show that it is possible to generate mission flight path by combining the maneuver libraries. Also, it is shown that the trajectory tracking control is possible. Therefore, since the results of this study enable the real-time trajectory generation and the tracking control, it will be useful to improve the probability of mission success and survivability of UAV (Unmanned Aerial Vehicle).

Joint optimal checkpointing and rejuvenation policy for real-time computing tasks

Performance of a software system can deteriorate from higher to lower levels due to software aging. To counteract the aging effect, software rejuvenation is widely implemented to restore the performance of a degraded system before the system crash actually takes place. To facilitate an effective system function restoration after each rejuvenation action, it is desirable to apply checkpointing to occasionally save the system state on a reliable storage so that the mission task can be resumed from the last saved checkpoint (instead of being restarted from the very beginning). As both rejuvenation and checkpointing procedures incur system overhead while bringing these benefits, it is significant to determine the optimal rejuvenation and checkpointing scheduling policy optimizing the system performance measures of interest. This paper makes new contributions by modeling and optimizing the joint maintenance policy involving state-based rejuvenation and periodic checkpointing schedule for software systems performing real-time computing tasks. The system can undergo multiple performance degradation levels or states, and transition time between different states can assume arbitrary types of distributions. The proposed solution methodology encompasses an efficient numerical algorithm for evaluating the probability of task completion (PTC) by a pre-specified deadline. The joint optimal rejuvenation and checkpointing policy is further determined to maximize the PTC of the considered real-time task. Examples are provided to illustrate applications of the proposed methodology as well as effects of system parameters on the optimization solution.

Optimizing Computational Mission Operation by Periodic Backups and Preventive Replacements

This paper models a warm standby system where a single element is online performing a specified mission task (e.g., a computing task) and subject to corrective replacement (CR) by an available standby element upon its failure. During the mission, preventive replacements (PRs) are also performed to renew the aged or worn online operating element before its actual failure according to a predetermined policy. In addition, to facilitate an effective restoration of system function in case of CR or PR happening, backups are also performed periodically so that the mission task can be resumed from the last successful backup point instead of from scratch. The mission succeeds if the specified mission task is accomplished; in other words, the mission fails when no operating elements remain prior to the mission task completion. In this paper, we make new contributions by first proposing an event transition-based numerical method to evaluate mission performance indices of the considered standby system subject to periodic backups, CR and PR. Mission success probability (MSP), expected mission completion time, expected mission operation cost (EMC), and expected uncompleted work fraction are evaluated. Based on the suggested evaluation algorithm, we make another contribution by formulating and solving optimization problems that help to determine the optimal backup-PR policy or the optimal combination of element activation sequencing and backup-PR policy to maximize MSP or minimize EMC. Influence of element performance and reliability parameters, data backup and retrieval complexity parameters on the optimal operation policy is investigated. Findings from this paper can guide the optimal decision making on policies related to element sequencing, backups as well as preventive maintenance planning, contributing toward reliable and cost-effective design and operation of standby computing systems.

Backtracking analysis approach for effectiveness of air defense operation system of systems based on force-sparsed stacked-autoencoding neural networks

To reduce the difficulty of traditional data-mining methods in deep analysis of emerging capacity index mechanisms for a complex air defense system of systems (ADSOS), a novel backtracking analysis approach based on force-sparsed stacked-autoencoding (FS-SAE) neural networks is proposed. Using the method of big-data correlation analysis, community structure analysis in complex networks, and principle component analysis based on the mission task, the networked structure of an index system for ADSOS, which was a relatively complete architecture with a well-defined meaning, was obtained. An FS-SAE backtracking analysis model was build based on heuristic knowledge from the obtained networked index system structure. The emerging relations between the capacity indices of an ADSOS were formalized. Then, the formation mechanism and contribution rate of capacity indices were studied, and the validity of this approach was validated by the simulation data. The experimental results show that formalized presentation for the emergence process of capacity indices of ADSOS based on the proposed model not only reflects the complexity characteristics of nonlinearity and uncertainty in the emergence process, but also give a general defined meaning for the index structure of the ADSOS. It provides a feasible method for commanders to deeply understand, manage, and control the complex operation system of systems.

Teologi, Studi Biblika, dan Misi

Missional hermeneutics is the interpretation of Scripture as it relates to the missionary task of the church. Four elements comprise a missional hermeneutics: 1) the missional trajectory of the biblical story being the foremost element, which also underlies the other three, 2) a narrative throughout Scripture centered on Christ and intended to equip the people of God for their missional task, 3) the missional context of the reader, in which attention moves from the task of equipping to the community being equipped, a community that is active, and 4) a missional engagement with culture and the implications thereof. Through the life of God’s people an alternative is offered, together with an invitation to come and join. Because the separation of theology from the mission of the church has distorted theology, all theology needs to be reformulated from the perspective of missio Dei and from the realization that the church is a sent community, missional in its very being. A missional hermeneutics bears implications upon the congregation, worship, preaching, discipleship, education, ministerial training, and the missionary task in multicultural contexts.

L'alternanza scuola-lavoro all'Università di Foggia. Un'occasione di public engagement

The present paper describes the theoretical and methodological principles, the research perspectives and the first training experiences of work-related learning in the 2016-2017 academic year by the Department of Humanistic Studies of the University of Foggia. The intention, for the University, was to also be a place for the promotion of training/professional development projects for young students and the construction of territorial networks: therefore as an educative orientative community. In this perspective, the experiences of work-related learning can be placed within the broader and more complex task of the third mission of the university institution, which places itself at the service of the territory to build a social pact, a formative alliance for growth and the development of the young generations.

Evolution analysis of a UAV real-time operating system from a network perspective

With the flourishing development of Unmanned Aerial Vehicles (UAVs), the mission tasks of UAVs have become more and more complex. Consequently, a Real-Time Operating System (RTOS) that provides operating environments for various mission services on these UAVs has become crucial, which leads to the necessity of having a deep understanding of an RTOS. In this paper, an empirical study is conducted on FreeRTOS, a commonly used RTOS for UAVs, from a complex network perspective. A total of 85 releases of FreeRTOS, from V2.4.2 to V10.0.0, are modeled as directed networks, in which the nodes represent functions and the edges denote function calls. It is found that the size of the FreeRTOS network has grown almost linearly with the evolution of the versions, while its main core has evolved steadily. In addition, a k-core analysis-based metric is proposed to identify major functionality changes of FreeRTOS during its evolution. The result shows that the identified versions are consistent with the version change logs. Finally, it is found that the clustering coefficient of the Linux OS scheduler is larger than that of the FreeRTOS scheduler. In conclusion, the empirical results provide useful guidance for developers and users of UAV RTOSs.

초등학교 영재학급 학생들이 도구의 사용 횟수를 최소화한 정다각형 작도 방법 유형 분석

The purpose of this study is to analyze the results of applying the mission task to construct the regular polygon by minimizing the number of tool use to the elementary school gifted students. Among the types of regular polygon construction methods that students performed, each persons showed their most favorite way of constructing (representative), and recommended the most efficient way(efficiency) and the best aesthetic thinking(aesthetic) of constructing through discussion with the group members. As a result, most of the students' preferred type was selected as the method with fewer tool use, but the method was chosen as the representative method which is considered to be novel or symmetrical and which is visually good. When recommending the most efficient method of drawing by group after individual activity, it is desirable to reduce the number of times the tool is used (minimum). But when the number of times the tool is used is the same, they recommended those easy to understand(intuitive) or those useful for other construction methods(applicability). The construction of the challenge form to construct a regular polygon with as few tools as possible has proved to be a good teaching material that not only induces logical reasoning through construction but also focuses on the nature and applicability of the figure.

Physiological and Functional Alterations after Spaceflight and Bed Rest.

Exposure to microgravity causes alterations in multiple physiological systems, potentially impacting the ability of astronauts to perform critical mission tasks. The goal of this study was to determine the effects of spaceflight on functional task performance and to identify the key physiological factors contributing to their deficits. A test battery comprised of seven functional tests and 15 physiological measures was used to investigate the sensorimotor, cardiovascular, and neuromuscular adaptations to spaceflight. Astronauts were tested before and after 6-month spaceflights. Subjects were also tested before and after 70 d of 6° head-down bed rest, a spaceflight analog, to examine the role of axial body unloading on the spaceflight results. These subjects included control and exercise groups to examine the effects of exercise during bed rest. Spaceflight subjects showed the greatest decrement in performance during functional tasks that required the greatest demand for dynamic control of postural equilibrium which was paralleled by similar decrements in sensorimotor tests that assessed postural and dynamic gait control. Other changes included reduced lower limb muscle performance and increased HR to maintain blood pressure. Exercise performed during bed rest prevented detrimental change in neuromuscular and cardiovascular function; however, both bed rest groups experienced functional and balance deficits similar to spaceflight subjects. Bed rest data indicate that body support unloading experienced during spaceflight contributes to postflight postural control dysfunction. Further, the bed rest results in the exercise group of subjects confirm that resistance and aerobic exercises performed during spaceflight can play an integral role in maintaining neuromuscular and cardiovascular functions, which can help in reducing decrements in functional performance. These results indicate that a countermeasure to mitigate postflight postural control dysfunction is required to maintain functional performance.

A relative navigation sensor for CubeSats based on LED fiducial markers

Small satellite platforms are becoming very appealing both for scientific and commercial applications, thanks to their low cost, short development times and availability of standard components and subsystems. The main disadvantage with such vehicles is the limitation of available resources to perform mission tasks. To overcome this drawback, mission concepts are under study that foresee cooperation between autonomous small satellites to accomplish complex tasks; among these, on-orbit servicing and on-orbit assembly of large structures are of particular interest and the global scientific community is putting a significant effort in the miniaturization of critical technologies that are required for such innovative mission scenarios. In this work, the development and the laboratory testing of an accurate relative navigation package for nanosatellites compliant to the CubeSat standard is presented. The system features a small camera and two sets of LED fiducial markers, and is conceived as a standard package that allows small spacecraft to perform mutual tracking during rendezvous and docking maneuvers. The hardware is based on off-the-shelf components assembled in a compact configuration that is compatible with the CubeSat standard. The image processing and pose estimation software was custom developed. The experimental evaluation of the system allowed to determine both the static and dynamic performances. The system is capable to determine the close range relative position and attitude faster than 10 S/s, with errors always below 10 mm and 2 deg.

Fault-tolerant pose and inertial parameters estimation of an uncooperative spacecraft based on dual vector quaternions

Estimating the parameters of an unknown free-floating tumbling spacecraft is an essential task for the on-orbit servicing missions. This paper proposes a dual vector quaternion based fault-tolerant pose and inertial parameters estimation algorithm of an uncooperative space target using two formation flying small satellites. Firstly, by utilizing the dual vector quaternions to model the kinematics and dynamics of the system, not only the representation of the model is concise and compacted, but also the translational and rotational coupled effects are considered. By using this modeling technique along with the measurements from the on-board vision-based sensors, a dual vector quaternion based extended Kalman filter for each of the two small satellites is designed. Secondly, both of the estimations from each small satellite will be used as inputs of the fault-tolerant algorithm. This algorithm is based on the fault-tolerant federal extended Kalman filter strategy to overcome the estimation errors caused by the faulty measurements, the unknown space environment and the computing errors by setting the appropriate ratios of the two estimations from the first step dual vector quaternions extended Kalman filter. Together with the first and second steps, a novel fault-tolerant dual vector quaternions federal extended Kalman filter using two formation flying small satellites is proposed by this paper to estimate the pose and inertial parameters of a free-floating tumbling space target. By utilizing the estimation algorithm, a good prior knowledge of the unknown space target can be achieved. Finally, the proposed dual vector quaternion federal extended Kalman filter is validated by mathematical simulations to show its robust performances.