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Optimal Controller Switching for Resource-constrained Dynamical Systems
이국태,Raktim Bhattacharya 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.3
In this paper, we present the resource-optimal controller switching synthesis for dynamical systems subject to resource constraints. Particularly, for systems having limited computational power (CPU) and onboard energy (battery), it is crucial to keep resource usage as low as possible. Although restrictions on resource utilization may save a CPU time and battery life, it degrades system performance. This paper provides three distinct algorithms that synthesize a controller switching policy for the purpose of resource savings, while not debasing system performance significantly. To measure system performance, we adopted the Waserstein distance that quantifies uncertainty in a probability density function level. The cost function to minimize is then defined based on this Wasserstein metric with a resource utilization penalty. As an example, quadrotor dynamics with two controllers, high performing / high resource consuming and moderate performing / resource saving controllers, is presented. The efficiency and usefulness of the proposed methods are validated in this example.
차량형 이동로봇의 위치 추정 정밀도 향상 기법 및 자동 주차 제어
이국태,정우진,장효환 한국로봇학회 2008 로봇학회 논문지 Vol.3 No.1
Recently, automatic parking assist systems are commercially available in some cars. In order to improve the reliability and the accuracy of parking control, pose uncertainty of a vehicle and some experimental issues should be solved. In this paper, following three schemes are proposed. (1) Odometry calibration scheme for the Car-Like Mobile Robot.(CLMR) (2) Accurate localization using Extended Kalman Filter(EKF) based redundant odometry fusion. (3) Trajectory tracking controller to compensate the tracking error of the CLMR. The proposed schemes are experimentally verified using a miniature Car-Like Mobile Robot. This paper shows that odometry accuracy and trajectory tracking performance can be dramatically improved by using the proposed schemes.
이륜차동구동형로봇의 복합오차를 고려한 기구학적 파라미터 정밀보정기법
이국태,정창배,정다운,정우진 한국로봇학회 2014 로봇학회 논문지 Vol.9 No.1
Odometry using wheel encoders is one of the fundamental techniques for the pose estimation of wheeled mobile robots. However, odometry has a drawback that the position errors are accumulated when the travel distance increases. Therefore, position errors are required to be reduced using appropriate calibration schemes. The UMBmark method is the one of the widely used calibration schemes for two wheel differential drive robots. In UMBmark method, it is assumed that odometry error sources are independent. However, there is coupled effect of odometry error sources. In this paper, a new calibration scheme by considering the coupled effect of error sources is proposed. We also propose the test track design for the proposed calibration scheme. The numerical simulation and experimental results show that the odometry accuracy can be improved by the proposed calibration scheme.
차량형 이동로봇의 기구학적 파라미터 보정을 위한 수렴성 분석
유광현(Kwanghyun Yoo),이국태(Kooktae Lee),정창배(Changbae Jung),정우진(Woojin Chung) 제어로봇시스템학회 2011 제어·로봇·시스템학회 논문지 Vol.17 No.12
Automated parking assist systems are being commercialized and rapidly spread in the market. In order to improve odometry accuracy, we proposed a practical odometry calibration scheme of Car-Like Mobile Robot (CLMR). However, there were some open problems in our prior work. For example, it was not clear whether the kinematic parameters always converged or not using the proposed calibration scheme. In addition, test driving had to be carried out “twice” without detailed explanation. This research aims to provide answers for the addressed questions though the convergence property analysis of the calibration scheme. In this paper, we evaluate on the effect of the kinematic parameter error on the odometry error at the final pose by numerical computation. The evaluation will show that the wheel diameter and tread of the CLMR can be calibrated by iterative test drives. In addition, the region of convergence in the parametric space will be discussed. Presented experimental results clearly showed that the proposed calibration scheme would be useful in practical applications.
이동로봇의 오도메트리 정밀도 향상을 위한 구조적 오차 보정 기법
정창배(Changbae Jung),이국태(Kooktae Lee),정우진(Woojin Chung) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Odometry using wheel encoders provides fundamental pose estimates for mobile robots. Pose estimation by pure odometry does not require environmental modification or prior knowledge of environment. However, the major drawback of odometry is the accumulation of errors. Due to the accumulation of odometry errors, the calibration of systematic errors is necessary. The reduction of systematic errors directly contributes to the improvement of odometry accuracy. In this paper, we propose two schemes for more accurate correction of odometry errors. At first, we analyze the UMBmark method, then suggest simultaneous errors which exist in actual robot motion. Secondly, an optimized size of the test track for odometry corrections is presented. Simulations and experimental results show the efficiency of the proposed method.