• Journal of Aerospace System Engineering
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• v.17 no.5
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• pp.34-41
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• 2023

This paper applies the icing effect and wing rock uncertainty to small unmanned aerial vehicles (UAVs), which have recently attracted attention. Attitude control simulations were performed using various control methods. First, the selected platform, the Skywalker X8 UAV with blended wing-body (BWB) configuration, was linearized for both its baseline form, and a form with applied icing effects. Subsequently, using MATLAB SimulinkⓇ, simulations were conducted for roll and pitch attitude control of the baseline configuration and the configuration with icing effects, employing disturbance observer-based PID control, model reference adaptive control, and model predictive control. Furthermore, the study introduced wing rock uncertainty simultaneously with icing effects on the configured model-a combination not previously explored in existing research-and conducted simulations. The performance of each control Method was compared and analyzed.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1363-1369
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• 2015

The frequency of a power system should be maintained within the allowed limits for stable operation. When a disturbance such as generator tripping occurs in a power system, the frequency is recovered to the nominal value through the inertial, primary, and secondary responses of the operating synchronous generators (SGs). However, for a power system with high wind penetration, the system inertia will decrease significantly because wind generators (WGs) are operating decoupled from the power system. This paper proposes a dynamic droop-based inertial control for a WG. The proposed inertial control determines the dynamic droop depending on the rate of change of frequency (ROCOF). At the initial period of a disturbance, where the ROCOF is large, the droop is set to be small to release a large amount of the kinetic energy (KE) and thus the frequency nadir can be increased significantly. However, as times goes on, the ROCOF will decrease and thus the droop is set to be large to prevent over-deceleration of the rotor speed of a WG. The performance of the proposed inertial control was investigated in a model system, which includes a 200 MW wind power plant (WPP) and five SGs using an EMTP-RV simulator. The test results indicate that the proposed scheme improves the frequency nadir significantly by releasing a large amount of the KE during the initial period of a disturbance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.10
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• pp.1973-1980
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• 2017

In the case of a small UUV operating an active synthetic aperture sonar, various velocity disturbances may occur on the path due to the influence of external underwater environment, and this causes phase errors in coherent synthetic aperture processing, which has a large influence on the detected image. In this paper, when a periodic sinusoidal velocity disturbance is generated in the traveling direction, the phase generated by the round trip slope range at each position is estimated the cross correlation coefficient for multiple received signals and compensated the position variation in the overlapped DPC by the average value within the maximum allowable width. Through simulations, it has been confirmed that the images degraded by the velocity disturbance amplitude and fluctuating frequency of the UUV are removed from the false targets and the performance of azimuth resolution is improved by the proposed phase compensation method.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.2
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• pp.301-308
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• 2017

This paper proposes a disturbance observer based controller design method for generating and yawing control of windturbine with two cooperative generators. Windturbine system with two cooperative generators is a distinct structure in which the wind energy supplied by blade axis is converted into electrical energy by two cooperative generators. In this structure, two generators can be controlled independently and therefore they can generate power, simultaneously performing yawing control of nacelle without extra yawing mechanism by cooperatively controlling generating load in appropriate manner. Using this structural trait, this paper designs a disturbance observer based controller that enables the windturbine system with cooperative generators to generate and yaw stably, and verifies the performance of the controller experimentally by applying it to a small-scale windturbine system with the same structure.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.356-362
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• 2017

This paper presents a robust position controller for a one degree-of-freedom (DOF) mechanical system using only position measurement. In order to alleviate the performance degradation owing to various uncertainties, a two-stage design method is studied by employing a proportional integral observer (PIO). In the first stage, a baseline backstepping controller is designed for a nominal system without accounting for uncertainties. The PIO is developed for estimating both the velocity information for the backstepping controller and an equivalent input disturbance for a feedforward compensation using the estimated uncertainty. It is shown that the estimation errors with the proposed PIO can be made arbitrarily small in a finite time. If the system suffers from undesirable actuator nonlinearities, however, it might be necessary to estimate the velocity and the disturbance with different rates of convergence. The proposed method combines the predesigned backstepping controller and dual PIOs to reduce mechanical vibrations as well as steady-state errors. The performance of the proposed method is tested through comparative computer simulations and experiments using a laboratory prototype.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.2
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• pp.163-172
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• 2014

This paper proposes a novel guidance law based on the block backstepping sliding mode control and extended state observer (ESO), which also takes into account the autopilot dynamic characteristics of the near space interceptor (NSI), and the impact angle constraint of attacking the maneuvering target. Based on the backstepping control approach, the target maneuvers and the parameter uncertainties of the autopilot are regarded as disturbances of the outer loop and inner loop, respectively. Then, the ESO is constructed to estimate the target acceleration and the inner loop disturbance, and the block backstepping sliding model guidance law is employed, based on the estimated disturbance value. Furthermore, in order to avoid the "explosion of complexity" problem, first-order low-pass filters are also introduced, to obtain differentiations of the virtual control variables. The stability of the closed-loop guidance system is also proven, based on the Lyapunov theory. Finally, simulation results demonstrate that the proposed guidance law can not only overcome the influence of the autopilot dynamic delay and target maneuvers, but also obtain a small miss distance.

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.503-505
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• 1986

주어진 제어대상 모델에 대하여 제어기를 구성하여 실제로 적용하는 경우 모델의 불일치, 모델링에서 고려하지 않은 외란(disturbance), 측정잡음등에 의하여 성능이 설계시와 달라진다. 실제적용에서도 성능을 계속 유지하기 위하여 제어기는 안정성, 계수변화(parameter variation)에 대한 강인성(robustness), 외란상쇄(disturbance rejection) 및 측정잡음에 둔감함등의 특성을 가져야 한다. 귀환(feedback)을 사용하여 제어기를 구성하는 경우 위의 모든 조건을 만족 시킬 수 없으므로 제어목적에 따라 적당한 조건을 선정하여 중요한 특성을 주로 갖게 한다. 본 논문에서는 쌍동선(small waterplane area twin hull ship-SWATHS)에 대하여 PID, LQ, LQG 제어기를 구성하여 안정성, 계수 변화에 대한 강인성, 외란 상쇄 및 측정잡음의 영향을 비교하였다. 쌍동선의 경우 다른 단동선(mono hull ship)에 비하여 접수면(waterplane)이 적으므로 무게증변을 흡수할 수 있는 복원력이 약하여 적은 외력에도 상하동요(heave)와 종동요(pitch)가 심하게 일어난다. 이러한 동요를 줄이는 것이 쌍동선의 제어목적이다. 본 연구에서는 먼저 선형화된 수직축 운동방정식을 이용하여 선체운동의 모델을 구했으며 중첩의 원리(super-position theorem)에 의하여 주파수 응답의 합으로 파도입력을 모델링 하였으며 제어를 위하여 필요한 측정치는 IMU(Inertial Measurement Unit)에서 제공된다고 가정하였다. 쌍동선의 동요의 원인은 파도, 바람, 조류 등이 있으나 파도에 의한 영향이 가장 크므로 본 논문에서는 파도에 의한 영향만을 고려하였다. 파도는 쌍동선에 외란으로 작용하며 측정할 수 없는 양이므로 PID, LQ 제어에서는 제어모델에 포함되지 않지만 LQG 제어에서는 제어모델에 포함된다. LQG 제어의 경우 제어모델에 파도를 백색잡음으로 가정하고 제어기를 구성한 것 (LQG1)과 2차의 쉐이핑필터(shaping filter)를 사용하여 구성한 것(LQG2)으로 나누었다.

• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.1
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• pp.50-63
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• 2002

The Karman boundary-layer has been numerically investigated for the disturbance wave number, wave velocity, azimuth angle and radius (Reynolds number, Re). The disturbed flow over rotating disk can lead to transition at a much lower Re than that of the well-known Type I instability. This early transition is due to the excitation of the Type II. Presented are the neutral stability results concerning these instabilities by solving newly formulated stability equations with consideration of whole convective terms. When the present numerical results are compared with the previously known results, the value of critical Re corresponding to Type I is moved from ${Re}_{c.1}$=285.3 to 270.2 and the value corresponding to Type II from ${Re}_{c.2}$=69.4 to 36.9, respectively. Also, the corresponding wave number is moved fro)m $k_1$=0.378 to 0.386 for Type I; from $k_2$=0.279 to 0.385 for Type II. For Type II, the upped limit of wave number and azimuth angle is $k_u$=0.5872, $\varepsilon_u$=$-17.5^{\circ}$, while its lower limit is near $k_u$=0, $\varepsilon_u$=$-28.4^{\circ}$. This implies that the disturbances will be relatively fast amplified at small Re and within narrow bands of wave number compared with the previous results.

• Journal of Ocean Engineering and Technology
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• v.14 no.4
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• pp.35-42
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• 2000

The sway control problem of the pendulum motion of a container hanging on the trolly, which transports containers from a container ship to trucks, is considered in the paper. In the container crane control problem, suppressing the residual swing motion of the container at the end of acceleration or the case of that the unexpected disturbance input exists is main issue. For this problem, in general, the trolley motion control strategy is introduced and applied. But in this paper, we introduce and synthesize a new type of swing motion control system. In this control system, a small auxiliary mass is installed on the spreader. And the actuator reacts against the auxiliary mass, applying intertial control forces to the container to reduce the swing motion in the desired manner. In this paper, we apply the LMI approach and simultaneous optimization design method to design the anti-swing motion control system for the controlled plant. And the simulation result shows that the proposed control strategy is shown to be robust to disturbances like winds and initial sway motion.

• Journal of Navigation and Port Research
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• v.42 no.2
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• pp.87-96
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• 2018

A trajectory control system plays an important role in controlling motions of marine vehicle when a series of way points or a path is given. In this paper, a sliding mode control (SMC)-based trajectory tracking controller for marine vehicles is presented. A small-sized unmanned ship is considered as a control object. Both speed and heading angle of a ship should be controlled for tracking control. The common point of related researches was to separate ship's speed and heading angle in control methods. In this research, a new control law from a general sliding mode theory that can be applied to MIMO (multi input multi output) system is derived and both speed and heading angle of a ship can be controlled simultaneously. The propulsion force and rudder force are also applied in modeling stage to achieve accurate simulation. Disturbance induced by wind is also tackled in the dynamics considering robustness of the proposed control scheme. In the simulation, we employed a way-point method to generate ship's trajectory and applied the proposed control scheme to ship's trajectory tracking control. Our results confirmed that the tracking error was converged to zero, thus demonstrating the effectiveness of the proposed method.