• 전자공학회논문지CI
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• 제44권1호
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• pp.94-101
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• 2007

스트리밍 비디오 서비스는 최근 이종망으로 구성되는 무선망에서 중요한 어플리케이션으로 자리잡을 것으로 예상된다. 그러나 군집성있는 패킷 손실에 의해서 서비스의 충분한 품질이 보장되지 않는다. 무선망에서 패킷 손실에 대한 효율적인 해결책은 수신단에서 적절한 에러 은닉 기술을 사용하는 방법일 것이다. 그러나 대부분의 에러 은닉 기술은 손실 블록에 인접한 이웃 블록들이 군집성 패킷 손실에 의해 이미 손실되었기 때문에 효율적으로 손실된 블록열들을 복원하기 어렵다. 이를 해결하기 위해 손실된 MB에서의 움직임 선형 특성을 이용하는 bidirectional motion vector tracking (BMVT)가 이전에 제안되었었다. 본 논문에서는 BMVT 에러 은닉 기술을 향상시킨 채널 적응형 잉여 코딩 방식이 소개되어진다.

• IEIE Transactions on Smart Processing and Computing
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• 제1권2호
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• pp.78-87
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• 2012

In this paper, we address the tracking problem caused by camera motion and rolling shutter effects associated with CMOS sensors in consumer handheld cameras, such as mobile cameras, digital cameras, and digital camcorders. A modified particle filtering method is proposed for simultaneously tracking objects and compensating for the effects of camera motion. The proposed method uses an elastic registration algorithm (ER) that considers the global affine motion as well as the brightness and contrast between images, assuming that camera motion results in an affine transform of the image between two successive frames. By assuming that the camera motion is modeled globally by an affine transform, only the global affine model instead of the local model was considered. Only the brightness parameter was used in intensity variation. The contrast parameters used in the original ER algorithm were ignored because the change in illumination is small enough between temporally adjacent frames. The proposed particle filtering consists of the following four steps: (i) prediction step, (ii) compensating prediction state error based on camera motion estimation, (iii) update step and (iv) re-sampling step. A larger number of particles are needed when camera motion generates a prediction state error of an object at the prediction step. The proposed method robustly tracks the object of interest by compensating for the prediction state error using the affine motion model estimated from ER. Experimental results show that the proposed method outperforms the conventional particle filter, and can track moving objects robustly in consumer handheld imaging devices.

• Journal of Advanced Marine Engineering and Technology
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• 제25권1호
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• pp.199-208
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• 2001

In this paper, an automatic route tracking algorithm using the position variables and the yaw angle of a ship is suggested, Since most autopilot systems paly only a role of course-keeping by integrating the gyrocompass output, they cannot cope with position errors between the desired route and real route of the ship resulted from a drifting and disturbances such as wave, wind and currents during navigation. In order for autopilot systems to track the desired route, a method which can reduce such position errors is required and some algorithms have been proposed[1,2]While such were turned out effective methods, they have a shortage that the rudder control actions for reducing the position errors are occurred very frequently. In order to improve this problem it is necessary to convert that error into the corresponding yaw angle and necessary to treat only yaw angle control problem. To do this a command generation algorithm which converts the rudder angle command reducing the current position error into they yaw angle command is suggested. To control the ship under disturbances and nonlinearities of the ship dynamics, the adaptive fuzzy controller is developed. Finally, through computer simulations for two ship models, the effectiveness of the suggested method and the possibility of the automatic route tracking are assured.

• 한국항행학회논문지
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• 제7권2호
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• pp.217-226
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• 2003

근래에 Poisson 형의 점프 프로세스를 이용하여 표적의 기동 운동을 모델링하고 이것을 이용한 반복형 최소 분산 선형 필터가 제안되었다. 이 필터에서는 기동 표적의 모델링에 사용한 점프의 상태천이 파라미터가 미리부터 필터에 알려져 있다고 가정하였는데 실제는 이것을 모르는 경우가 많다. 본 논문에서는 이러한 기동 추적과정에 수반되는 모델링 오류가 제안된 추적필터의 성능에 어떤 영향을 미치는지 고려한다. 정성적인 분석을 위해서 상태천이 파라미터를 실제와 다른 값을 사용하고, Monte-Carlo 시뮬레이션을 통해 필터의 성능을 해석한다.

• 제어로봇시스템학회논문지
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• 제12권2호
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• pp.101-105
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• 2006

Disk radial runout creates a periodic relative motion between the laser beam spot and tracks formed on an optical disk. While only focus control is activated, the periodic relative motion yields sinusoid-like waves in the tracking error signal, where one cycle of the sinusoid-like waves corresponds to one track. The frequency of the sinusoid-like waves varies depending on the disk rotational speed and the amount of the disk radial runout. If the frequency of the tracking error signal in the off-track state is too high due to large radial runout of the disk, it is not a simple matter to begin track-following control stably. It might take a long time to reach a steady state or tracking control might fail to reach a stable steady state in the worst case. This article proposes a simple method for reducing the relative motion caused by the disk radial runout in the off-track state. The relative motion in the off-track state is effectively reduced by a drive input obtained through measurements of the tracking error signal and simple calculations based on the measurements, which helps reduce the transient response time of the track-following control. The validity of the proposed method is verified through an experiment using an optical disk drive.

• 제어로봇시스템학회논문지
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• 제19권6호
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• pp.495-500
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• 2013

This paper proposes a double sliding surfaces based on a sliding mode control for a tracking control of nonholonomic mobile robots in the Cartesian coordinates. In order to remove sliding surface constraints, we design the additional sliding surface for the heading angle with respect to the newly defined coordinates. Then, we define the switching law based on the posture error to combine the designed sliding surface with the previous one. By using the double sliding surfaces and the switching law, we obtain the control law for arbitrary trajectories. It is proved that the position tracking error and the heading direction error asymptotically converge to zero, respectively, with the Lyapunov stability theory. Finally, through computer simulations, we demonstrate the effectiveness of the proposed control system.

• 한국군사과학기술학회지
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• 제10권2호
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• pp.21-30
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• 2007

A practical method to design the input shaping which generates control command is proposed in this paper, We suggest an experimental technique considering human operator's target tracking error to improve aiming accuracy which significantly affects hit probability. It is known that stabilization performance is one of the most important factors for ground combat vehicle system. In particular, stabilization error of the manual target tracking system mounted on moving vehicle directly affects hit probability. To reduce this error, we applied input command shaping method using preprocessing filtering and functional curve fitting. First of all, we construct the human operator model to consider effects of human operator on our system. Input shaping curve is divided into several regions to get rid of the above problems and to improve the system performance. At example design part, we chose three steps of functional command curve and determine the parameters of the function by the proposed design method. In order to verify the proposed design method, we carried out the experiments with real plant of a fighting vehicle.

• 전자공학회논문지CI
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• 제48권5호
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• pp.1-7
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• 2011

전자광학추적장비는 영상신호를 이용하여 이동하는 목표물을 추적하며 안정화된 영상을 제공하는 장비이다. 또한, 특정 위치를 자동으로 관측하는 좌표지향 기능을 수행한다. 좌표지향은 항공기의 급격한 기동이나 외란 등의 외적 요인에 방해받지않고 시선을 지향점에 고정하도록 하는 기능이다. 본 논문에서 좌표지향시의 주요 오차 요소들의 영향을 검토하여 항법정보의 전송지연이 주요 오차임을 확인하였다. 또한 지연된 항법정보로부터 현재 항공기의 항법정보를 추정하기 위해 병합칼만필터를 설계하였다. 실제 항공기의 비행데이터를 이용한 시뮬레이션을 통해 제안한 방법이 전송지연으로 인한 좌표지향 오차를 절반 이하로 줄일 수 있음을 보였다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권11호
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• pp.664-670
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• 2004

This paper presents a new velocity estimation strategy of a non-salient permanent magnet synchronous motor (PMSM) drive without high frequency signal injection or special PWM pattern. This approach is based on the d-axis current regulator output voltage of the drive system that has the information of rotor position error. The rotor velocity can be estimated through a rotor position tracking PI controller that controls the position error to zero. For zero and low speed operation, PI controller gains of rotor position tracking controller have a variable structure according to the estimated rotor velocity. In order to boost the bandwidth of PI controller around zero speed, a loop recovery technique is applied to the control system. The proposed method only requires the flux linkage of permanent magnet and is insensitive to the parameter estimation error and variation. The designers can easily determine the possible operating range with a desired bandwidth and perform the vector control even at low speeds. The experimental results show the satisfactory operation of the proposed sensorless algorithm under rated load conditions.

• 한국항공우주학회지
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• 제49권11호
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• pp.953-960
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• 2021

거창 우주물체 레이저 추적 시스템은 인공위성 레이저 추적, 적응광학, 우주쓰레기 레이저 추적 등 과학 연구 및 국가적 미션을 수행하기 위해 100cm 크기의 광학 망원경을 가지고 있으며, 빠르고 정밀한 구동을 위하여 경위대식 방식의 추적마운트를 개발하여 테스트 관측 중에 있다. 최근 레이저 추적 시스템의 자동 관측 및 응용 연구 분야에서 추적 대상을 정밀하게 추적할 수 있는 능력은 시스템 성능을 판단할 수 있는 중요한 지표 중 하나이다. 그러기 위해서는 정밀 추적을 저해하는 요인을 파악하고 보정하기 위한 지향 보정 모델이 요구된다. 따라서 본 논문에서는 추적마운트 제작, 조립 및 설치 과정에서 발생 할 수 있는 정적 지향 오차 발생 원인들을 분석하였으며, 거창 우주물체 레이저 시스템의 추적마운트에 적용된 지향 보정 모델 및 최소자승법을 통해 추적마운트 파라미터를 추정하고, 지향 정밀도 분석 결과를 제시하였다.