방위 위치오차 자동 추출을 활용한 SAR 영상 기반 선박의 거리방향 속도 측정

송주영,김덕진,김진우,전영범,김종건,김혁,김휘송,이혁빈,안상호,이정훈,김준우 한국전자파학회 2023 한국전자파학회논문지 Vol.34 No.12

Estimation of the moving target velocity from SAR images is widely focused on range projection, exploiting the azimuth offset caused by the target range velocity. For marine vessels, positional distortion between the vessel signature and the wake enables velocity estimation. However, the wake signature is highly influenced by the vessel velocity, weather conditions, and SAR polarization, thereby preventing accurate velocity estimation. This study proposed an automated estimation of the azimuth offset that enabled the precise meas- urement of the range velocity. Given that different line-of-sight directions modify the range velocity, the movement of the vessel in each Doppler sublook was estimated. Accordingly, the distance of the vessel in SLC and the position without the azimuth offset were measured and used to accurately estimate the target range velocity; tested against the AIS velocity, 0.51 m/s of average offset was measured from ICEYE SAR images. The algorithm uniquely proposed the automatic estimation of the target range velocity using the target heading angle.

Estimation of the maximum velocity using the entropy concept in an open channel

Choo, Tai Ho,Yun, Gwan Seon,Yoon, Hyeon Cheol,Noh, Hyun Seok,Bae, Chang Yeon Springer Science and Busness Media 2016 Environmental Earth Sciences Vol.75 No.2

<P>Accurate measurements and estimations of the river flow rate are essential elements for the effective management of water resources. The stage-discharge curve is a traditional method but it has limited applicability because of the loop form characteristics, which are caused by a tidal river, the backwater effect, and the sudden changes in water level during the flood season. Therefore, various discharge estimation methods have been studied for long periods. On the other hand, measurements and estimations of the maximum velocity, which is a technically important parameter, have been difficult. If the maximum velocity can be estimated, it will be possible to determine the flow velocity because the minimum velocity is always zero at the bed under open channel flow conditions. In addition, the maximum velocity always has one value regardless of the flow conditions, such as laminar flow, turbulent flow, and a cross-sectional shape. This means that the maximum velocity is used to estimate the mean velocity. Therefore, in the present paper, an estimation formula for the maximum velocity was proposed using the entropy concept. The accuracy was verified using 12 sets measured under non-uniform flow conditions in the laboratory. A comparison of the estimated value with the value actually measured showed very high accuracy.</P>

A Position and Velocity Estimation Using Multifarious and Multiple Sensor Fusion

Youngwan Cho,Heejin Lee 한국지능시스템학회 2017 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.17 No.2

In this paper, we propose a fusion algorithm of multifarious and multiple sensors to enhance the accuracy and reliability of position and velocity estimation for the vehicles. We proposed an adaptive Kalman filter for multiple sensor fusion to provide a fault tolerant estimation. We verified the multiple sensor fusion estimator can provide a fault tolerant estimation through Matlab simulation and laboratory equipped experiments. We also proposed a fusion algorithm of multifarious sensors in order to enhance the velocity estimation accuracy. We proposed a Kalman filter error correction for compensate the accumulative error in the main sensor with the other type of sensor which has characteristic of biased error. We also developed a fusion algorithm for compensate the error in the position measuring with the velocity measuring. We made experiments for estimating position and velocity of vehicle simultaneously through the fusion of multifarious and multiple sensors and showed that average position error was 1.5764 m and average velocity accuracy was 99.81%.

Quantitative analysis of resolution and smoothing effects of digital pore microstructures on numerical velocity estimation

이민후,김영석,송다희 한국지질과학협의회 2017 Geosciences Journal Vol.21 No.3

Numerical estimation of physical properties from digital pore microstructures has drawn great attention and is being used for quantifying interrelation between various physical properties. The pore microstructures are commonly obtained by the Xray microtomographic technique, which can give fairly accurate pore geometry. However, there is minor distortion due to the limited resolution or smoothing. This distortion can cause errors in estimating physical properties by pore-scale simulation techniques. Among the properties, seismic velocity would have relatively large errors since a small amount of change in grain contacts can cause significant over-estimation. In this paper, we analyzed the errors in seismic velocity by resolution and smoothing of pore geometry using three samples: an unconsolidated sand pack and two medium-porosity sandstones with different degrees of consolidation. As the resolution becomes poor, the calculated velocity increases linearly, while smoothing gives nonlinear trends; higher errors in the early stage of smoothing. As we expected, soft rocks have higher sensitivity, since the grain contacts are small and are sensitive to minor distortion. Within similar ranges, the resolution causes larger errors than smoothing. In addition, smoothing does not cause velocity over-estimation once the resolution becomes poor, while the resolution can create considerable errors in velocity even after significant smoothing. We conclude that the resolution should be considered in the first place when obtaining digital pore microstructures to minimize errors in velocity estimation. We can also suggest that a good care should be taken when applying smoothing filters, if a sample is suspected to be poorly-consolidated or to have high porosity.

저 분해능 엔코더를 사용한 정밀 속도 제어

서기원(Ki Won Seo),강현재(Hyun Jae Kang),이충우(Choong Woo Lee),정정주(Chung Choo Chung) 대한전기학회 2007 대한전기학회 학술대회 논문집 Vol.2007 No.4

This paper presents an effective method of precise velocity control at low speed with a low resolution encoder. Multirate observer to estimate the velocity at every DSP control period is used except a constant velocity mode. The observer corrects the estimation error when detects pulse signal. Unlike the conventional methods. the multirate estimator is stable at a low speed. However, the multirate estimator shows ripples at a constant velocity. Thus, in this paper we use a velocity prediction method which uses the present velocity from the previous average velocity to reject the ripple. In a summary, at a constant speed mode, the predicted velocity is used. Otherwise, the estimated velocity by the multirate obvserver is used. The effectiveness of the multirate observer and ripple rejection at low speed is verified through various simulations.

Integrated Estimation of Vehicle States, Tire Forces, and Tire-Road Friction Coefficients

Tesheng Hsiao,Jing-Yuan Lan,Hanping Yang 제어로봇시스템학회 2014 제어로봇시스템학회 국제학술대회 논문집 Vol.2014 No.10

Information about the vehicle states (e.g. the sideslip angle and the longitudinal velocity), tire forces, and tire-road friction coefficients is crucial for advanced vehicular active safety systems. In particular, the latest high-performance control system based on optimally distributing and controlling all tire forces requires feedback of the tire forces and the tire-road friction coefficient of each individual tire. Therefore, estimating all or parts of the vehicle/tire/road states from available sensor measurements in production vehicles has long been an active research topic in both academia and industry. Despite recent advances in automotive estimation technologies, it remains an open question on identifying the tire-road friction coefficient of each individual tire. This paper proposes an integrated estimation system that provides accurate estimates of the vehicle/tire/road states from available sensor measurements. More importantly, the tire-road friction coefficient of each tire can be separately estimated. The performance of the proposed estimation system is verified by simulations based on a complex nonlinear vehicle/ tire model.

SAR-GMTI에서 지상이동표적의 속도 추정 기법

배창식(Chang-Sik Bae),전현무(Hyeon-Mu Jeon),양동혁(Dong-Hyeuk Yang),양훈기(Hoon-Gee Yang) 한국전자파학회 2017 한국전자파학회논문지 Vol.28 No.2

본 논문에서는 2채널 displaced phase center antenna(DPCA) 기반의 SAR-GMTI 시스템에서 지상이동 표적의 속도 정보를 추정하는 알고리즘을 제안한다. 제시된 알고리즘에서는 이동표적의 across-track 속도는 기존의 along-track interferometry(ATI) 기법을 이용하여 추정이 가능하다고 가정한 후 표적의 along-track 속도를 추정하는 방법을 제시한다. 이를 위해 기존 이동표적 구조를 변형하여 이동표적 속도를 영으로 만들고, 이를 레이다 속도에 반영하여 레이다 속도가 변화된 새로운 기하학적 구조를 얻는다. 이후 합성 개구면(synthetic aperture) 내의 subaperture 신호에 대한 푸리에 변환을 통해 공간 주파수 중심점 위치를 이용하여 표적의 along-track 속도를 추정한다. 시뮬레이션을 통해 제안한 알고리즘의 속도 추정 성능을 검증하고, 또한 추정된 속도가 보상되어 이동표적 영상의 해상도 및 SINR이 개선됨을 보인다. A ground moving target"s velocity estimation algorithm applicable for a SAR-GMTI system using 2 channel displaced phase center antenna(DPCA) is proposed. In this algorithm, we assume target"s across-track velocity can be estimated by along-track interferometry (ATI) and present a method to estimate target"s along-track velocity. To accomplish this method, we first transform a radar-target geometry in which a moving target has zero velocity via altering a radar velocity such that target"s velocity is reflected into it and next manipulate the spectral centers of the subapertures within the synthetic aperture. The validity of the proposed algorithm is demonstrated through simulation results showing the performance of the target"s velocity estimation and the enhancement of reconstructed target image quality in terms of resolution and SINR.

SAR 영상의 Azimuth 차분을 이용한 움직이는 물체의 속도측정방법

박정원 ( Jeong Won Park ),정형섭 ( Hyung Sup Jung ),원중선 ( Joong Sun Won ) 大韓遠隔探査學會 2008 大韓遠隔探査學會誌 Vol.24 No.2

SAR에서 마이크로파의 진행방향으로의 속도성분을 가지고 움직이는 물체는 영상에서 azimuth 방향으로 이동된 위치에 상이 맺힌다는 현상은 이미 잘 알려져 있다. 대부분의 속도측정 알고리즘들은 실제물체의 위치와 상이 맺힌 위치 사이의 거리를 측정함으로써 속도를 유추하였다. 그러나 움직이는 물체의 실제의 위치를 나타내는 지시자인 도로나 배의 물결모양은 일반적으로 SAR 영상에서의 식별도가 높지 않기 때문에 이러한 방법은 영상취득시의 조건이나 물체의 움직임 정도에 따라 적용이 제한적이다. 이에 본 연구에서는 SAR 원시자료 처리단계의 중간 산물인 range-compressed 영상의 azimuth 차분신호로부터 물체의 속도를 측정하는 새로운 방법을 제안한다. 이 방법은 움직이는 물체에 의한 도플러 중심주파수의 변이가 azimuth 차분신호에서의 위상변화를 일으킨다는 점에 기초한다. 일반적으로 SAR에서 감지하는 지표물의 위상은 SAR의 기하에 의하여 발생하는 도플러 변화율에 따라서 선형적으로 변한다. 이 선형변화위상과 몇 가지 상수 값을 갖는 위상들을 제거하고 남은 신호는 물체의 움직임과 직접적인 관련이 있으므로, 이로부터 속도를 구해낼 수 있다. 이 방법을 실제 ENVISAT ASAR영상을 이용하여 배의 속도를 구하는 데에 적용해 보았으며, 그 결과는 목표물의 위치에 따라 다른 양상을 보였다. 해상에 단독적으로 존재하는 배에 적용하였을 때는 0.1m/s 정도의 차이로 기존의 속도측정 알고리즘의 결과와 잘 일치하였으나, 육지에 인접한 연안의 배는 선호의 교란에 의해서 1m/s 이상의 오차를 보였다. We present an efficient and robust technique to estimate the velocity of moving targets from a single SAR image. In SAR images, azimuth image shift is a well known phenomenon, which is observed in moving targets having slant-range velocity. Most methods estimated the velocity of moving targets from the distance difference between the road and moving targets or between ship and the ship wake. However, the methods could not be always applied to moving targets because it is difficult to find the road and the ship wake. We propose a method for estimating the velocity of moving targets from azimuth differentials of range-compressed image. This method is based on a phenomenon that Doppler center frequency shift of moving target causes a phase difference in azimuth differential values. The phase difference is linearly distorted by Doppler rate due to the geometry of SAR image. The linear distortion is eliminated from phase removal procedure, and then the constant phase difference is estimated. Finally, range velocity estimates for moving targets are retrieved from the constant phase difference. This technique was tested using an ENVISAT ASAR image in which several unknown ships are presented. In the case of a isolated target, the result was nearly coincident with the result from conventional method. However, in the case of a target which is located near non-target material, the difference of the result between from our algorithm and from conventional method was more than 1m/s.

다중 프레임의 SAD를 이용한 드론 속도 측정

남돈호,염석원 한국융합신호처리학회 2019 융합신호처리학회 논문지 (JISPS) Vol.20 No.3

Drones are highly utilized because they can efficiently acquire long-distance videos. In drone operation, the speed, which is the magnitude of the velocity, can be set, but the moving direction cannot be set, so accurate information about the drone’s movement should be estimated. In this paper, we estimate the velocity of the drone moving at a constant speed and direction. In order to estimate the drone's velocity, the displacement of the target frame to minimize the sum of absolute difference (SAD) of the reference frame and the target frame is obtained. The ground truth of the drone’s velocity is calculated using the position of a certain matching point over all frames. In the experiments, a video was obtained from the drone moving at a constant speed at a height of 150 meters. The root mean squared error (RMSE) of the estimated velocities in x and y directions and the RMSE of the speed were obtained showing the reliability of the proposed method. 드론은 원거리 동영상을 효율적으로 획득할 수 있어서 활용성이 높다. 드론 운용에서 속도의 크기인 속력은 설정할 수 있지만 이동하는 방위의 정확한 값은 설정이 불가능하다. 본 논문에서는 드론에서 획득한 동영상을 이용하여 일정한 속도로 이동하는 드론의 속도를 추정한다. 기준 프레임과 표적 프레임의 Sum of Absolute Difference(SAD)를 최소로 하는 표적 프레임의 변위를 구한다. 드론의 실제 속도(Ground Truth)는 각 프레임에서 일정한 동일 지점(Matching Point)의 위치를 이용하여 계산한다. 실험에서 150m 상공에서 일정한 속력으로 이동하는 드론으로 동영상을 획득하였다. 추정한 x와 y방향의 속도와 속력의 평균 제곱근 오차(RMSE)를 구하여 제안한 방법의 신뢰성을 보였다.

주파수 영역에서의 간단한 zero-forcing 기법을 이용한 속도 적응형 채널 추정 기법

류탁기,박구현,홍대식,강창언,Yu Takki,Park Goohyun,Hong Daesik,Kang Changeon 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.1a

본 논문에서는 주파수 영역에서의 간단한 zero-forcing 기법을 이용한 속도 적응형 채널 추정 기법을 제안한다. 제안된 기법은 최적의 채널 추정 기법인 Wiener 필터의 주파수 응답을 구형(rectangular)으로 근사화하여 유도된다. 채널 추정 과정은 수신 신호에서 최대 도플러 주파수보다 큰 주파수 성분들을 제거함으로써 수행된다. 제안된 기법은 채널 계수와 이동체 속도에 대한 동시 추정 기법으로 확장 가능하며, 하나의 FFT 구조를 사용하여 효과적으로 구현 가능하다. 실험 결과를 통해 제안된 채널 추정 기법은 기존의 속도 적응형 채널 추정 기법들보다 넓은 속도 범위에서 낮은 채널 추정 MSE 성능을 보여주며, 확장된 동시 추정 기법은 다양한 채널 환경에서 안정된 추정 성능을 보인다. 마지막으로 제안된 기법에 대한 MSE 성능이 수식적으로 유도된다. In this paper, we propose a velocity-adaptive channel estimation scheme using the simple zero-forcing technique in the frequency domain. Channel estimation is performed by removing frequency components that are higher than the maximum Doppler frequency in the received signal. The proposed scheme can be extended to the combined estimation scheme for channel coefficients and mobile velocity using one FFT/IFFT module. Simulation results show that the proposed scheme outperforms conventional schemes for a wide range of mobile velocities($3{\sim}300\;Km/h$). Finally, the MSE for the proposed channel estimation scheme is analyzed.