• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.110-114
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• 1995

This paper presents the on-board attitude determination algorithm for LEO (Low Earth Orbit) three-axis stabilized spacecraft. Two advanced star trackers and a three-axis Inertial Reference Unit (IRU) are assumed to be attitude sensors. The gyro in the IRU provides a direct measurement of the attitude rates. However, the attitude estimation error increases with time due to the gyro drift and noise. An update filter with measurements of star trackers and/or sun sensor is designed to update these gyro drift bias and to compensate the attitude error. Kalman Filter is adapted for the on-board update filter algorithm. Simulation results will be presented to investigate the attitude pointing performance.

• Journal of Family Resource Management and Policy Review
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• v.19 no.2
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• pp.127-148
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• 2015

This study compared types of time and money attitudes by respondents' characteristics, and compared leisure consumption behavior and leisure satisfaction among different groups, which are classified by attitudes toward time and money. It also verified a structural model for the relationship of leisure satisfaction and the attitudes toward time and money, and investigated the moderating effects of leisure consumption behavior. Data were obtained from a questionnaire completed by 512 adult consumers. Using factor analyses and cluster analyses, this study classified the types of time and money attitudes. The time attitude was categorized according to four clusters: time-insensibility, future- oriented, present-oriented, and past-oriented. The money attitude was divided into four clusters: future safety, stinginess/anxiety, diversion, and power/prestige. The major findings of this study were as follows: First, the propensity of leisure consumption behavior to seek fashion and conspicuousness was higher for time-insensibility group than for the others. However, the propensity of rational consumption behavior for leisure was higher for the future-oriented group. The level of leisure satisfaction was the highest for the time-insensibility group. Second, the propensity of leisure consumption behavior to seek fashion and conspicuousness was higher for those who considered money as tools for diversion and power/prestige. The propensity of rational consumption behavior for leisure was higher for the future safety and stinginess/anxiety groups. The level of leisure satisfaction was significantly higher for the diversion group. Third, from the results of structural analyses, the time-insensibility attitude showed a positive effect on the leisure consumption behavior to seek fashion and conspicuousness. The future-oriented attitude had a positive effect on the propensity of rational consumption behavior for leisure. The money attitudes of diversion and power/prestige had positive impacts on the leisure consumption behavior to seek fashion and conspicuousness, although they had negative effects on the propensity of rational consumption behavior for leisure. The leisure consumption behavior to seek fashion and conspicuousness had a positive effect on leisure satisfaction, although the rational consumption behavior for leisure had a negative effect.

• Journal of Mechanical Science and Technology
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• v.20 no.3
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• pp.376-381
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• 2006

In this paper, the quaternion, the dual Euler, and the direction cosine methods are numerically compared using a non-aerodynamic 6 degree-of-freedom rigid model at all-attitude angles of an aircraft. The dual Euler method turns out to be superior to the others in the applications because it shows better numerical accuracy, stability, and robustness in integration step sizes. The dual Euler method is affordably less efficient than the quaternion method in terms of computational cost. Numerical accuracy and stability, which allow larger integration step sizes, are more critical in modern real-time applications than computational efficiency because of today's increased computational power. If the quaternion method is required because of constraints in computation time, then a suppression mechanism should be provided for algebraic constraint errors which will eventually add computational burden.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.2
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• pp.300-314
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• 2017

This paper examines finite rotation angle (FRA) applications for spacecraft attitude control. The coordinate transformation matrix and the attitude kinematics represented by FRAs are introduced. The interpolation techniques for the angular orientations are thoroughly investigated using the FRAs and the results are compared to those using traditional methods. The paper proposes trajectory description techniques by using extremely smooth polynomial functions of time, which can describe point-to-point attitude maneuvers in a realizable and accurate manner with the help of unique FRA features. In addition, new controller design techniques using the FRAs are developed by combining the proposed interpolation techniques with a model predictive control framework. The proposed techniques are validated through their attitude control applications for an aggressive point-to-point maneuver. Conclusively, the FRAs provide much more flexibility than quaternions and Euler angles when describing kinematics, generating trajectories, and designing attitude controllers for spacecraft.

• International Journal of Aeronautical and Space Sciences
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• v.6 no.2
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• pp.17-22
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• 2005

As one of validation tool for attitude determination system, we have used various constraints using priori information which is known through base vector set up. However these conventional constraints cannot guarantee validity in terms of final solutions such as Euler angle. So we suggest attitude boundary concept to verify the final attitude solution on the flying airplane, it is based on the combination of velocity based attitude estimation technique and ambiguity resolution. we can say it can check invalid solution effectively at just one epoch without repeatability test of resolved cycle ambiguity. In this paper we show that the suggested constraint can effectively reject incorrectly resolved cycle ambiguity the conventional constraints have missed.

• Advances in aircraft and spacecraft science
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• v.9 no.5
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• pp.433-447
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• 2022

This work deals with an explicit guidance and control architecture for autonomous lunar ascent and orbit injection, i.e., the locally-flat near-optimal guidance, accompanied by nonlinear reduced-attitude control. This is a new explicit guidance scheme, based on the local projection of the position and velocity variables, in conjunction with the real-time solution of the associated minimum-time problem. A recently-introduced quaternion-based reduced-attitude control algorithm, which enjoys quasi-global stability properties, is employed to drive the longitudinal axis of the ascent vehicle toward the desired direction. Actuation, based on thrust vectoring, is modeled as well. Extensive Monte Carlo simulations prove the effectiveness of the guidance, control, and actuation architecture proposed in this study for precise lunar orbit insertion, in the presence of nonnominal flight conditions.

• International Journal of Aeronautical and Space Sciences
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• v.8 no.1
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• pp.10-20
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• 2007

For spacecraft attitude control, reaction wheel (RW) steering laws with more than three wheels for three-axis attitude control can be derived by using a control allocation (CA) approach.1-2 The CA technique deals with a problem of distributing a given control demand to available sets of actuators.3-4 There are many references for CA with applications to aerospace systems. For spacecraft, the control torque command for three body-fixed reference frames can be constructed by a combination of multiple wheels, usually four-wheel pyramid sets. Multi-wheel configurations can be exploited to satisfy a body-axis control torque requirement while satisfying objectives such as minimum control energy.1-2 In general, the reaction wheel steering laws determine required torque command for each wheel in the form of matrix pseudo-inverse. In general, the attitude control command is generated in the form of a feedback control. The spacecraft body angular rate measured by gyros is used to estimate angular displacement also.⁵ Combination of the body angular rate and attitude parameters such as quaternion and MRPs(Modified Rodrigues Parameters) is typically used in synthesizing the control command which should be produced by RWs.¹ The attitude sensor signals are usually corrupted by noise; gyros tend to contain errors such as drift and random noise. The attitude determination system can estimate such errors, and provide best true signals for feedback control.⁶ Even if the attitude determination system, for instance, sophisticated algorithm such as the EKF(Extended Kalman Filter) algorithm⁶, can eliminate the errors efficiently, it is quite probable that the control command still contains noise sources. The noise and/or other high frequency components in the control command would cause the wheel speed to change in an undesirable manner. The closed-loop system, governed by the feedback control law, is also directly affected by the noise due to imperfect sensor characteristics. The noise components in the sensor signal should be mitigated so that the control command is isolated from the noise effect. This can be done by adding a filter to the sensor output or preventing rapid change in the control command. Dynamic control allocation(DCA), recently studied by Härkegård, is to distribute the control command in the sense of dynamics⁴: the allocation is made over a certain time interval, not a fixed time instant. The dynamic behavior of the control command is taken into account in the course of distributing the control command. Not only the control command requirement, but also variation of the control command over a sampling interval is included in the performance criterion to be optimized. The result is a control command in the form of a finite difference equation over the given time interval.⁴ It results in a filter dynamics by taking the previous control command into account for the synthesis of current control command. Stability of the proposed dynamic control allocation (CA) approach was proved to ensure the control command is bounded at the steady-state. In this study, we extended the results presented in Ref. 4 by adding a two-step dynamic CA term in deriving the control allocation law. Also, the strict equality constraint, between the virtual and actual control inputs, is relaxed in order to construct control command with a smooth profile. The proposed DCA technique is applied to a spacecraft attitude control problem. The sensor noise and/or irregular signals, which are existent in most of spacecraft attitude sensors, can be handled effectively by the proposed approach.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.1
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• pp.54-63
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• 2016

A novel attitude tacking control method using Time Delay Control (TDC) scheme is developed to provide robust controllability of a rigid hexacopter in case of single or multiple rotor faults. When the TDC scheme is developed, the rotor faults such as the abrupt and/or incipient rotor faults are considered as model uncertainties. The kinematics, modeling of rigid dynamics of hexacopter, and design of stability and controllability augmentation system (SCAS) are addressed rigorously in this paper. In order to compare the developed control scheme to a conventional control method, a nonlinear numerical simulation has been performed and the attitude tracking performance has been compared between the two methods considering the single and multiple rotor faults cases. The developed control scheme shows superior stability and robust controllability of a hexacopter that is subjected to one or multiple rotor faults and external disturbance, i.e., wind shear, gust, and turbulence.

• The Journal of Industrial Distribution & Business
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• v.12 no.10
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• pp.43-57
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• 2021

Purpose: This study focuses how motivations influence interactivity in the live streaming commerce context. Live streaming commerce involves the provision of e-commerce activities and transactions via a live streaming platform that offers real-time interaction, entertainment, social activities, and commerce. The purpose of study is to examine effects of motivations on perceived interactivity and the effects of perceived interactivity on attitude and intention to use the live streaming commerce. Research design, data and methodology: The study investigates key questions about consumers' motivation to use live streaming commerce and perceived interactivity by surveying 300 users of live commerce. Participants were asked whether they were live streaming commerce users who had experienced live streaming commerce before participating in the survey. The full survey required live streaming commerce users to respond to all the questions. Results: The study uncovered motivations for using live streaming commerce by finding information, entertainment, pass time, fashion/status and real time and perceived interactivity in the live streaming commerce. The results indicated motivation to use live streaming commerce positively influenced perceived interactivity. Perceived interactivity had positive effects on attitude toward brand. Attitude toward brand had positive effects on intention to use. Conclusions: Live streaming commerce is getting increasing attention from marketers because live streaming commerce has seamlessly integrated commerce, social activities, and hedonic factors. This study clarifies motivations and perceived interactivity in the live streaming commerce context. The study uncovers the relationships between motivations, perceived interactivity, attitude, and intention to use that contributes to the theoretical foundation and practical implications for marketing and management in the live streaming commerce context. Specifically, the study develops the theoretical contributions to perceived interactivity in the in the live streaming commerce context. The results also contribute to the practical implications for new marketing strategies that provides dynamic real-time interaction, exact information, and social and hedonic factors to attract consumers to indulge in the consumption processes. Marketing practitioners will obtain insights that can help them develop and manage brand strategies by understanding the influence of motivation and perceived interactivity in the live commerce context, which offers opportunities for contactless marketing and management.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.274-277
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• 2002

This paper deals with the attitude determination using GPS carrier phase. The main factors on attitude reliability are accuracy, error factors and the real-time ambiguity resolution speed. Firstly, these factors are reviewed. And then, the attitude reliability is improved by applying the averaging method. Finally, the attitude determination software is verified by the experiments. The accuracy of the proposed attitude determination method is 0.013$^{\circ}$ PE in live test. This result is more accurate than the existing INS equipment.