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On Semi-cubically Hyponormal Weighted Shifts with First Two Equal Weights
Baek, Seunghwan,Jung, Il Bong,Exner, George R.,Li, Chunji Department of Mathematics 2016 Kyungpook mathematical journal Vol.56 No.3
It is known that a semi-cubically hyponormal weighted shift need not satisfy the flatness property, in which equality of two weights forces all or almost all weights to be equal. So it is a natural question to describe all semi-cubically hyponormal weighted shifts $W_{\alpha}$ with first two weights equal. Let ${\alpha}$ : 1, 1, ${\sqrt{x}}$(${\sqrt{u}}$, ${\sqrt{v}}$, ${\sqrt{w}}$)^ be a backward 3-step extension of a recursively generated weight sequence with 1 < x < u < v < w and let $W_{\alpha}$ be the associated weighted shift. In this paper we characterize completely the semi-cubical hyponormal $W_{\alpha}$ satisfying the additional assumption of the positive determinant coefficient property, which result is parallel to results for quadratic hyponormality.
Robust Estimation of Vehicle Dynamic Behavior by Using Fusion Sensors
Seunghwan Baek,Jungkwang Choi,Heungseob Kim,Moonyoung Yoon,Kwangsuck Boo 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
This paper presents the development of an algorithm for vehicle dynamics estimation by using four 3-axis acceleration sensors which are located in the MR-CDC damper for vehicle dynamics control. The sensor fusion algorithm has been developed to identify road information and estimate vehicle dynamics behavior instead of the yaw rate. The Kalman filter has been also designed to estimate the yaw rate of the vehicle and provides the yaw rate as well as the estimation error. The outputs of the 4 sensor pairs according to 4 suspensions have been fused to provide an accurate and robust estimation of the yaw rate by weighted sum in which the weighting factors are inverses of the estimation errors. The proposed sensor fusion algorithm has been also evaluated by comparison with the yaw rate sensor at center of the vehicle gravity. The robust and accurate estimation of the vehicle dynamics has been achieved even under the failed sensor or noisy environment.
The Flatness Property of Local-cubically Hyponormal Weighted Shifts
Baek, Seunghwan,Do, Hyunjin,Lee, Mi Ryeong,Li, Chunji Department of Mathematics 2019 Kyungpook mathematical journal Vol.59 No.2
In this note we introduce a local-cubically hyponormal weighted shift of order ${\theta}$ with $0{\leq}{\theta}{\leq}{\frac{\pi}{2}}$, which is a new notion between cubic hyponormality and quadratic hyponormality of operators. We discuss the property of flatness for local-cubically hyponormal weighted shifts.
Application of a Sliding Mode Control to Anti-lock Brake System
Seunghwan Baek,Jeonghoon Song,Duksun Yun,Heungseob Kim,Kwangsuck Boo 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
This paper presents application method of a sliding mode wheel slip controller for ABS that improves the vehicle response and increases the safety on slippery road. Sliding mode wheel slip controller receives wheel slip ratio, vehicle velocity, longitudinal acceleration, and tire forces from vehicle model to generate braking pressures. In general, two solenoid valves, so called normal open and normal close valves, have been used to generate the hydraulic pressure necessary to generate proper braking force. In this paper, the valve operating method is proposed to implement the sliding mode control output in hydraulic unit of the ABS. The control performance is verified by using a HILS System that has a vehicle braking system controlled with On/Off solenoid valves.
Robust Estimation of Vehicle Recognition on Curved Roads using a Rear-Side View Vision System
Baek, Seunghwan,Kim, Heungseob,Boo, Kwangsuck 한국정밀공학회 2014 International Journal of Precision Engineering and Vol.15 No.4
This paper presents a method to estimate the relative distance and speed of vehicles approaching from the side and rear for a blind spot detection system or lane change assistance. Vehicles with the same relative distance can be assigned different pixel positions on the image frame depending on the road curvature. Thus, based on a lane model and vehicle dynamics, a Perception-Net estimation algorithm has been designed to recognize the rear-side lanes and their curvature under various noisy environments. Vehicles approaching from the rear are detected by calculating the velocity vector of feature flows, which are a type of motion analysis, on the image frame. Through various simulations, it is concluded that the proposed method can provide robust estimations of the relative distance and speed between vehicles with satisfactory error tolerance.
SEMI-CUBICALLY HYPONORMAL WEIGHTED SHIFTS WITH STAMPFLI'S SUBNORMAL COMPLETION
Baek, Seunghwan,Lee, Mi Ryeong Korean Mathematical Society 2019 대한수학회논문집 Vol.34 No.2
Let ${\alpha}:1,(1,{\sqrt{x}},{\sqrt{y}})^{\wedge}$ be a weight sequence with Stampfli's subnormal completion and let $W_{\alpha}$ be its associated weighted shift. In this paper we discuss some properties of the region ${\mathcal{U}}:=\{(x,y):W_{\alpha}$ is semi-cubically hyponormal} and describe the shape of the boundary of ${\mathcal{U}}$. In particular, we improve the results of [19, Theorem 4.2].
Seunghwan Baek,Jeonghoon Song,Duksun Yun,Heungseob Kim,Kwangsuck Boo 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
This paper deals with vehicle stability during deceleration by using sliding mode anti-lock brake system (ABS) controller, which is designed in this research. The sliding mode controller (SMC) applies to hardware in the loop simulation (HILS) system, which can be performed ABS test with actual hydraulic unit and hydraulic lines that are the same of passenger vehicle, and the experiment results are compared with that of commercial ABS ECU. In this paper, the designed sliding mode ABS controller follows the target slip ratio and secures the vehicle stability for braking on various road conditions and several test modes. The test results show that designed sliding mode ABS controller has better performance than commercial ABS ECU for ensuring vehicle stability as well as holding the target slip ratio.
상용 소프트웨어를 이용한 Sliding Mode TCS 제어기의 성능평가
백승환(Seunghwan Baek),이창석(Changseok Lee),윤득선(Duksun Yun),송정훈(Jeonghoon Song),김흥섭(Heungseob Kim),부광석(Kwangsuck Boo) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
This paper evaluates traction control system (TCS) by using sliding mode control (SMC) method. The designed SMC only control braking force, an engine torque control is not considered in this research. SMC is a type of variable structure control where the dynamics of a nonlinear system is altered via application of a highfrequency switching control. Validation of the designed controller has been performed by using commercial vehicle dynamics analysis program, it can be used to simulate dynamic characteristics of a vehicle on various driving conditions. The results show that performances of designed SMC are in good accordance with those of the commercial software on various road conditions. The designed SMC provides more available steering angle on uniform slippery road, and if an engine TCS is used, the yaw rate and the lateral offset are larger than those obtained results.
방역차량의 약제 살포량 측정 정확성 개선을 위한 디지털 필터와 댐퍼 개발
백승환 ( Seunghwan Baek ),박동혁 ( Donghyeok Park ),박하나 ( Hana Park ),이춘구 ( Chungu Lee ),이중용 ( Joongyong Rhee ) 한국농업기계학회 2017 한국농업기계학회 학술발표논문집 Vol.22 No.1
방역 차량의 약액탱크, 차량의 연료, 워셔액 등의 탱크 내부에는 잔존량을 측정하기 위해 기둥과 floating box로 이루어진 부력식 수위레벨센서가 사용되고 있으나 액체레벨에 따라 float이 상하로 움직이는 측정원리상 차량 주행 중 정확성이 매우 떨어진다(Park et al. 2016). 방역차량이 주행 중 분사할 때, 슬로싱 현상과 방역소독기의 노즐과 펌프에서 발생하는 진동으로 인해 기존의 부력식 센서를 이용한 약제살포량 측정방법은 정확성이 매우 떨어지는 경향이 있다. 본 연구의 목적은 방역차량이 주행하면서 분사할 때, 수위레벨 센서를 이용한 약제살포량 측정의 정확성을 개선하는 것으로 디지털 칼만필터, Low pass filter와 댐퍼를 제작하여 이용했다. 본 연구에서는 압력식 레벨센서를 이용해 약액탱크의 높이당 단면적과 수위를 측정하여 약제살포량을 계산했다. Python 2.7을 이용해 디지털 칼만필터와 Low pass filter(LPF)를 구현하였으며 3D프린터를 이용해 댐퍼를 제작했다. 실내에서 슬로싱 현상을 인공적으로 만들어 필터와 댐퍼의 수위 측정 정확성개선효과를 확인 후 실제 방역차량에 부착하여 비포장도로에서 주행하면서 분사할 때 필터와 댐퍼의 효과를 확인하였다. 댐퍼의 공극률(p)을 바꿔가며 수위 측정 정확성 개선효과를 확인하였다. 실내, 현장 실험 결과, 칼만필터가 LPF보다 개선효과가 더 크지만 데이터 50개 처리에 1.71초의 시간지연이 발생했다. 댐퍼는 수위센서를 고정시키고 유체의 운동을 방해하여 이상치와 큰 오차제거에 효과적이었다. 칼만필터와 댐퍼를 동시에 이용할 경우, 수위 측정정확성 R²는 0.9985, 0.9981로 ±4.3cm의 범위내에서 수위를 측정할 수 있었다. 필터의 시간지연과 수위 측정정확성을 고려하여 데이터 기록간격을 3초로 설정하면 ±3cm이내에서 약탱크 내 수위를 측정할 수 있었다. 공극률(p)가 0.294, 0.291, 0.17에서 측정정확성 R²는 각각 0.9897, 0.9858, 0.9872 로 p가 0.294에서 개선효과가 가장 좋았으나 개선효과의 차이는 크지 않았다.