| 1. |
- Emami, Reza, et al.
(författare)
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Engineering design pedagogy : a performance analysis
- 2020
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Ingår i: International journal of technology and design education. - : Springer. - 0957-7572 .- 1573-1804. ; 30:3, s. 553-585
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Tidskriftsartikel (refereegranskat)abstract
- Cornerstone design courses have become a major part of engineering curricula, where students with different personality types and learning styles work together to design, develop, build, and demonstrate the functionality of a prototype within the duration of a term. This study analyzes student and team performance against gender, personality types, and learning styles in a second-year engineering design course. Further, the correlations between several assessment mechanisms are studied, and the effects of three different instructional design approaches on students’ performance are explored. Data have been collected on student performance and psychometrics, including marks, gender, personality type, and learning style from 2001 to 2018. To identify students’ personality types and learning styles, Myers–Briggs Type Indicators (MBTI) and Neil Fleming’s Learning VARK tests were administered. To evaluate students’ performance in the course, a number of assessment mechanisms have been defined. Several statistical methods are used to analyze data, and to determine correlation between datasets. Over nearly two decades of marks, gender, MBTI, and VARK data for 2637 students are presented for an engineering design course. The results demonstrated that there was no significant difference in performance across most assessments based on gender or gender distribution on a team. A better performance was observed from VK bimodal and quadmodal learning styles in most assessment mechanisms. Further, certain MBTI groups, namely, judging types outperformed their peers in engineering design assessments, with interesting interplay between MBTI dimensions for specific assessments and team dynamics. Traditional assessment mechanisms, such as engineering notebook and design proposals, are shown to be good predictors of student success. Lastly, scaffolded design activities and front-loading of lecture content were shown to be beneficial for student learning. There is negligible performance difference between female and male students in the engineering design course. Students whose preferred learning styles align with the assessment themes showed better performance in the course. The outcomes of this paper can be readily applied by instructors for design of assessment mechanisms, course materials, team formation, and instructional design.
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| 2. |
- Hakima, Houman, et al.
(författare)
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A Deorbiter CubeSat for Active Orbital Debris Removal
- 2018
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Ingår i: Advances in Space Research. - : Elsevier. - 0273-1177 .- 1879-1948. ; 61:9, s. 2377-2392
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Tidskriftsartikel (refereegranskat)abstract
- This paper introduces a mission concept for active removal of orbital debris based on the utilization of the CubeSat form factor. The CubeSat is deployed from a carrier spacecraft, known as a mothership, and is equipped with orbital and attitude control actuators to attach to the target debris, stabilize its attitude, and subsequently move the debris to a lower orbit where atmospheric drag is high enough for the bodies to burn up. The mass and orbit altitude of debris objects that are within the realms of the CubeSat’s propulsion capabilities are identified. The attitude control schemes for the detumbling and deorbiting phases of the mission are specified. The objective of the deorbiting maneuver is to decrease the semi-major axis of the debris orbit, at the fastest rate, from its initial value to a final value of about 6,471 km (i.e., 100 km above Earth considering a circular orbit) via a continuous low-thrust orbital transfer. Two case studies are investigated to verify the performance of the deorbiter CubeSat during the detumbling and deorbiting phases of the mission. The baseline target debris used in the study are the decommissioned KOMPSAT-1 satellite and the Pegasus rocket body. The results show that the deorbiting times for the target debris are reduced significantly, from several decades to one or two years.
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| 3. |
- Hakima, Houman, et al.
(författare)
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Adaptive Detumbling Controller for Deorbiter CubeSat
- 2020
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Ingår i: 2020 IEEE Aerospace Conference. - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- This paper presents an attitude regulation controller that is utilized by a nanosatellite, called Deorbiter CubeSat, intended for the removal of sizable debris from low Earth orbit. The controller is used to detumble an uncooperative debris object to which the Deorbiter CubeSat is attached. The spacecraft performs a rendezvous maneuver, attaches rigidly to the exterior of the target debris, and detumbles and steers it toward the deorbit altitude. Three reaction wheels, in a mutually-orthogonal configuration, are used to control the attitude of the combined CubeSat and debris system. Each reaction wheel is capable of producing about 20 mN·m of torque, and has a maximum momentum capacity of 60 mN·m·s. Since physical parameters of the debris to be detumbled, e.g., mass and moment of inertia, are not known a priori, or there are large uncertainties in their values, the detumbling controller estimates the unknown parameters in order to reduce the regulation error to zero over time. Simulation results show that the controller is able to fully detumble the CubeSat-debris system in a matter of minutes, without knowing the debris physical parameters in the beginning of the maneuver.
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| 4. |
- Hakima, Houman, et al.
(författare)
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Assessment of active methods for removal of LEO debris
- 2018
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Ingår i: Acta Astronautica. - : Elsevier. - 0094-5765 .- 1879-2030. ; 144, s. 225-243
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the applicability of five active methods for removal of large low Earth orbit debris. The removal methods, namely net, laser, electrodynamic tether, ion beam shepherd, and robotic arm, are selected based on a set of high-level space mission constraints. Mission level criteria are then utilized to assess the performance of each redirection method in light of the results obtained from a Monte Carlo simulation. The simulation provides an insight into the removal time, performance robustness, and propellant mass criteria for the targeted debris range. The remaining attributes are quantified based on the models provided in the literature, which take into account several important parameters pertaining to each removal method. The means of assigning attributes to each assessment criterion is discussed in detail. A systematic comparison is performed using two different assessment schemes: Analytical Hierarchy Process and utility-based approach. A third assessment technique, namely the potential-loss analysis, is utilized to highlight the effect of risks in each removal methods
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| 5. |
- Hakima, Houman, et al.
(författare)
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Attitude Estimation for a Deorbiter CubeSat
- 2019
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Ingår i: Proceedings of 9th International Conference on Recent Advances in Space Technologies. - : IEEE. ; , s. 709-714
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Konferensbidrag (refereegranskat)abstract
- This paper investigates the attitude estimation capabilities of a debris-removing nanosatellite called deorbiter CubeSat. The spacecraft is designed based on the utilization of commercially-available components with long space heritage, which are embedded in an eight-unit form factor. The attitude estimation machinery employed in this work is a discrete-time, quaternion-based, extended Kalman filter, which utilizes measurements provided by a three-axis rate sensor, five sun sensors, and a three-axis magnetometer. To obtain a linear state-space model, gravity gradient and magnetic disturbance torques are included in the plant model, and the model is linearized with respect to the process noise and the states, namely the inertial angular velocities and the quaternions. measurements noises are modelled based on zero-mean Gaussian distributions, and are quantified based on the performance of the state-of-the-art, commercial-of-the-shelf devices. A Monte Carlo simulation is created to analyze the performance of the estimator against various initial angular velocities and quaternions, both in the sunlit and in the eclipsed portions of the orbit. In light of the results, the accuracy of the deorbiter CubeSat’s attitude knowledge is discussed.
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| 6. |
- Hakima, Houman, et al.
(författare)
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Concurrent attitude and orbit control for deorbiter CubeSat
- 2020
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Ingår i: Aerospace Science and Technology. - : Elsevier. - 1270-9638 .- 1626-3219. ; 97
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Tidskriftsartikel (refereegranskat)abstract
- This paper details a concurrent attitude and orbit control method for a debris-removing nanosatellite, called deobriter CubeSat, during the rendezvous and synchronization maneuver with an uncontrollable tumbling debris object. The CubeSat is designed based on the utilization of an eight-unit form factor and commercially-available components with substantial space heritage, and is intended for the removal of sizable debris objects in low-Earth orbit. In particular, a low-thrust propulsion system is used for orbit control, as well as three reaction wheels allowing for a three-axis attitude control. Since the thruster can only produce force in one direction in the body frame, the spacecraft is considered to be underactuated. The controller employs the reaction wheels and the thruster to simultaneously rendezvous and synchronize the attitude of the CubeSat with the tumbling debris object, allowing for a concurrent attitude and position tracking. Detailed derivation of the concurrent controller is discussed, the effects of high-order derivatives are analyzed, and the stability of the system is proved. Simulation scenarios are created for two different thruster operation modes, namely, unsaturated thrust force and continuously-saturated thrust force, in order to verify the performance of the controller, as well as its robustness against gravity gradient disturbance torque and gravitational perturbation force.
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| 7. |
- Hakima, Houman, et al.
(författare)
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Debris detumbler : An alternative approach to active debris removal
- 2016
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Ingår i: Proceedings of the International Astronautical Congress, IAC.
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Konferensbidrag (refereegranskat)abstract
- Since the launch of the first artificial satellite, i.e., Sputnik in 1957, several thousand man-made objects have been launched into the Earth orbits, great majority of which remained in their orbit despite the termination of their mission. A number of viable solutions have been suggested in the research community for actively removing the orbital debris, some of which require the capturing of the debris, while others are contactless methods. A challenging aspect of capturing an orbital debris using any method is due to the tumbling motion of the debris. A majority of the suggested methods require zero or very low rates of debris attitude to perform successfully, or need to follow a synchronization phase with the debris before the capturing and removal operation. This is technically costly and challenging, if not infeasible. This paper proposes an alternative approach to orbital debris removal, which can make various state-of-the-art methods of active debris removal perform at lower costs and risks. The approach utilizes one or more detumbler platforms, in the form of miniaturized cubesats, which are de-signed to be lunched from the remover spacecraft, attach to the target debris, and reduce its attitude rate to zero using the onboard attitude determination sensors and control actuators. The paper outlines the operation of debris detumblers. The conceptual design of such platforms is also presented, based on the one- to three-unit cubesat bus and commercial off-the-shelf technologies. Orbital insertion, rendezvous and attachment maneuvers are also discussed. Finally, through simulations the performance of the proposed approach is compared with that of some well-studied methods in various scenarios using several catalogued debris, based on performance metrics such as delta-v, operation time, trajectory simplicity, total thrust, etc
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| 8. |
- Houman, Hakima, et al.
(författare)
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Prioritizing orbital debris for active debris removal missions
- 2017
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Ingår i: IEEE Aerospace Conference Proceedings. - Piscataway, NJ : Institute of Electrical and Electronics Engineers (IEEE). - 9781509016136
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Konferensbidrag (refereegranskat)abstract
- This paper introduces a method of prioritizing orbital debris for future active debris removal missions, based on the evaluation of the total collision probability of each cataloged debris. The United States Space Surveillance Network actively monitors, tracks, and catalogs space debris orbiting Earth. The catalog is updated routinely, and is available to the public in the form of two-line element data. The total collision probability of a debris is defined as the overall probability of the debris colliding with any other debris in a given time window. The proposed method uses the two-line element data pertaining to each debris in the catalog to project the future state of the debris, i.e., the classical orbital elements, at predefined time steps for a given time window. The effects of orbital perturbations are considered wherever applicable. The relative distances between all debris are estimated in each time step, and pairwise collision probabilities are calculated for any two debris objects in the catalog. To obtain the total collision probability for a debris, the pairwise collision probabilities pertaining to the debris are summed. Further, for every debris object the trend in the total collision probability as the time window progresses is quantified, and debris objects are ranked based on their chance of collision in the time window. The outcome of the study is compared with target debris proposed in other studies.
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