• Advances in aircraft and spacecraft science
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• 제9권5호
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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.

• Advances in aircraft and spacecraft science
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• 제1권4호
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• pp.427-441
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• 2014

Orbit-raising is an important step to place spacecraft from parking orbits into working orbits. Attitude control system design is crucial in the success of orbit-raising. Several text books have discussed this design and focused mainly on the traditional methods based on single-input single-output (SISO) transfer function models. These models are not good representations for many orbit-raising control systems which have multiple thrusters and each thruster has impact on the attitude defined by all outputs. Only one published article is known to use a more suitable multi-input multi-output (MIMO) Euler angle model in spacecraft orbit-raising attitude control system design. In this paper, a quaternion based MIMO model for the orbit-raising attitude control system design is proposed. The advantages of using quaternion based model for orbit-raising control system designs are (a) there is no need for mathematical transformations because the attitude measurements are normally given by quaternion, (b) quaternion based model does not depend on rotational sequences, which reduces the chance of human errors, and (c) the singular point of reduced quaternion model is the farthest from the operational point where linearization is performed. We will show that performance of quaternion model based design will be as good as the performance of Euler angle model based design for orbit-raising problem.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.150-153
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• 1995

In this paper the attitude control system is developed for longitudinal motion of Foil-Catamaran in regular waves with all-movable foils which attached to fore and after part of the ship and verified the system by theoretical calculation and model-tests. The linearized equations of motion of the ship is employed to apply the linear control theories, the PID control and the LQR. The strip method was used to calculate hydrodynamic coefficients and wave exciting forces of the demi hull, and unsteady hydrodynamic forces of foils are considered by using the result of Wu(1972). About 40-60% of motions is reduced in experiments. The control system described in this paper is able to extended to 6-DOF motions or control in irregular wave with trivial modification. And it is applicable to hull shape development for better seakeeping performance and to determine the size and the position of hydrofoils for the attitude control.

• 제어로봇시스템학회논문지
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• 제5권1호
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• pp.62-68
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• 1999

The attitude of a vehicle can be precisely determined using GPS carrier phase measurements from more than two antennas attached to a vehicle and an efficient integer ambiguity resolution technique. Many methods utilizing the known baseline length as a constraint of independent elements of integer ambiguities are proposed to resolve integer ambiguity at real time. Three-dimensional search space is reduced to two-dimensional search space with this constraint. Thus the true integer ambiguity can be easily determined with less computational burden and fewer number of measurements. But there are still strong requirements for the real time integer ambiguity resolution, which uses single epoch measurement of long baseline. In this paper, a new constraint from the geometry of multiple baselines is derived. With this new constraint, two-dimensional search space is further reduced to one-dimensional search space. It makes possible to determine integer ambiguity with single epoch measurement. The proposed method is applied to real data to show its effectiveness.

• 보건교육건강증진학회지
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• 제21권3호
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• pp.87-100
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• 2004

Objective: This research has been conducted in order to conduct sex education using information and communication technologies (ICT) which is currently taught to elementary school students, understand how this method of education affects the knowledge of and attitude towards sexual health in them, so that it could be actually applied in classrooms. Subject: 115 students were divided into three different groups: a comparison group of 38 students (who were given no sex education at all), control 2 group of 39 students (who were given sex education via video programmes), and control 1 group of 38 students (who were given sex education using ICT). Research Tool: A questionnaire used by the literature studies. After verifying content validity, it was modified and supplemented in this way: sex knowledge was reduced to 26, and sex attitude was also reduced to 11. The reliability of the research tool was Cronbach's a=0.86 for sex knowledge tool, and Cronbach's a=0.81 for sex attitude tool. The collected data have been analysed using SPSS 11.0 program. The content validity was analysed by factor analysis and multiple regression analysis, and hypothesis verification was analysed using repeated measure ANOVA test. Result: 1) In sex knowledge marks, there was a significant difference according to the group (p=.009) and point of time (p=.000), and there was a significant interaction between the groups and point of time(P=.000). As a result, it turned out that both video programmes and ICT were significantly effective in improve the knowledge. 2) In sex attitude marks, there were no significant differences according to the group (p=.213), but there was a significant difference according to point of time (p=.002), and there was a significant interaction between the groups and point of time(P=.018). As a result, it turned out that only the education method using ICT was effective in improving the attitude. Conclusion: From the results of this research, it can be said that the sex education using ICT was the most effective method in improving the sex knowledge and attitude of students at elementary school. Therefore, it is advisable that the sex education methods using ICT should be developed and applied continuously.

• Journal of Astronomy and Space Sciences
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• 제28권4호
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• pp.311-317
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• 2011

Momentum changing actuators like reaction wheels and control moment gyros are generally used for spacecraft attitude control. This type of actuators produces force and torque disturbances. These disturbances must be reduced since they degrade the quality of spacecraft attitude control. Major disturbances are mainly due to static and dynamic imbalances. This paper gives attention to the reduction of the static and dynamic imbalance. Force/torque measurement system is used to measure the disturbance of the test reaction wheel. An identification method for the location and magnitude of the imbalance is suggested, and the corrections of the imbalance are performed using balancing method. Through balancing, the static and dynamic imbalance is remarkably reduced.

• 한국항공우주학회지
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• 제46권11호
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• pp.934-943
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• 2018

고기동 위성은 영상획득수량 등의 주요 임무성능을 향상시킬 수 있는 진보된 위성으로, 특히 지구관측분야에서 그 수요가 꾸준히 증대되고 있다. 본 논문은 고-토크 리액션휠을 장착한 위성의 기동성능을 높일 수 있는 자세제어 기법을 연구한다. 크게 3가지의 서로 독립된 방법을 제안하며, 위성 자세제어 시스템에 따라 모든 방법을 적용하거나 1-2개 방법만 적용하는 것도 가능하다. 각 방법을 요약하면 다음과 같다. 첫 번째로, 기존 피드백 제어기에 피드포워드(자세명령) 입력을 추가한 피드포워드/피드백 제어기를 소개하고 그 장단점을 요약한다. 두 번째로, 리액션휠 클러스터의 토크/모멘텀 용량을 최대한 활용하는 방법을 제안한다. 세 번째로, 마찰토크를 보상하는 토크기반 리액션휠 제어기법을 소개한다. 시뮬레이션을 통해 기존 피드백 제어기에 비해, 피드포워드/피드백 제어기를 적용 시 기동성이 향상됨을 확인하였다. 특히, 기동각이 클 때, 정착시간 감소가 두드러짐을 확인하였다.

• 보건교육건강증진학회지
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• 제11권2호
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• pp.18-32
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• 1994

The purpose of this study was to analyze the effectiveness of injury prevention education on elementary school students. We are selected two elementary school in Tejeon, one was intervention school, the other was control school. Surveys were completed before the begining of the interventions in February in 1994 and again after their completion in July 1994. Intervention group was 284 students in pre-test and 218 students in post-test. And control group was 253 students in pre-test and 208 students in post-test. The results of this study was followed. 1. In the general characteristics of subjects studied, sex, mother education, father education, economic status, number of household, and traffic environment were not significant difference between intervention and control group(p>0.05). 2. The contents of injury prevention education that subjects wished to learn, were not significant difference between intervention and control group(p>0.05). Also the mothods of that were significant difference between intervention and control group in pre-test(p<0.05) but not in post-test(p>0.05). 3. Education in knowledge, attitude and practice of injury prevention was slightly effectiveness. Change in attitude of injury prevention was higher than in knowledge and attitude of that we guess that they require a lot of education in the pedestrian prevention. 4. Reative risk between intervention and control group in injury incidence was 1.53 in hospital-care students, and 1.43 in home-care children. Also relative risk of total injury incidence was 1.38, therefore we knew that injury incidence after education was reduced. 5. In the analysis of injury causes, pedestrain injury was remarkably reduced at hospital-care students in two group. At home-care students, two groups were high proportion in play injury. 6. In the analysis of injury places, intervention group was high proportion at near-the house in pre-test(35.4%) and at school in post-test(36.4%). And control group was high at inside-the house in pre-test(31.5%) and at near-the house in post-test(28.2%).

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.141.5-141
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• 2001

An attitude GPS receiver with 3 antennas obtains 3-dimensional attitude using GPS carrier phase measurement INS obtains the 3 dimensional navigation solution for IMU consisting of accelerometers and gyro. Ground-alignment process for the low -cost INS cannot be performed well due to the large sensor noise. Using the standard GPS receiver, however, continuous in-flight alignment for the INS becomes possible, and consequently, the errors in IMU sensors and navigation solution can be compensated. Especially with attitude measurement from the attitude GPS receiver, the compensation of errors in gyroscope and attitude would be done respite of the vehicle´s dynamics and their error covariance would be reduced. This paper presents ...

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2011년도 한국우주과학회보 제20권1호
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• pp.32.2-32.2
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• 2011

State dependent Riccati equation (SDRE) control technique has been widely used in the control society. Although it solves nonlinear optimal control problems, which minimizes state error and control efforts simultaneously, it has drawbacks when it is to be applied to the real time systems in that it requires much computational efforts. So the real time system whose computational ability is limited (for example, satellites) cannot afford to use SDRE controller. To solve this problem, a hybrid controller which is based on MSDRE (Modified SDRE) and ANFIS (Adaptive Neuro-Fuzzy Inference System) has been proposed by Abdelrahman et al. (2010). We propose a hybrid controller based on SDRE and ANFIS, and apply the hybrid controller to the hardware attitude simulator to perform a HIL (Hardware-In-the-Loop) simulation. Through HIL simulation, it is demonstrated that the hybrid controller satisfies the control requirement and the computation load is reduced significantly. In addition, the effects of statistical properties of the ANFIS training data to the performance of the ANFIS controller have been analyzed.