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류정래(Jung Rae Ryoo),도태용(Tae-Yong Doh) 제어로봇시스템학회 2014 제어·로봇·시스템학회 논문지 Vol.20 No.5
Optical pick-up is a core component for data read/write operations in optical disc drives, and an optical pick-up performance evaluator is an instrument used to analyze the overall performance of an optical pick-up. Due to inevitable errors in an analog measurement circuit, resultant evaluation data is not guaranteed to be accurate. In this paper, a calibration method for an optical pick-up performance evaluator is proposed to ensure evaluation accuracy. Measured data is corrected by a 1st order correction function, and a calibration process based on least-square method is utilized to obtain correction coefficients of the correction function. The proposed calibration method is applied to experiments, and enhanced accuracy is presented with resultant evaluation data.
류정래(Jung Rae Ryoo),도태용(Tae-Yong Doh) 제어로봇시스템학회 2014 제어·로봇·시스템학회 논문지 Vol.20 No.2
DC motor is a representative electric motor commonly utilized in various motion control fields. However, DC motor-based motion control systems suffer from degradation of position precision due to nonlinear static friction. In order to enhance control precision, friction model-based compensators have been introduced in previous researches, where friction models are identified and counter inputs are added to control inputs for cancelling out the identified friction forces. In this paper, a static friction compensator is proposed without use of a friction model. The proposed compensation algorithm utilizes internal state manipulation to generate compensation pulses, and related parameters are easily tuned experimentally. The proposed friction compensator is applied to a DC motor-based motion control system, and results are presented in comparison with those without a friction compensator.
실시간 비디오 응용을 위한 CFA 보간과 컬러 영상 워핑 통합
김봉규,류정래 대한전자공학회 2020 전자공학회논문지 Vol.57 No.11
Color filter array (CFA) image warping before color reconstruction is a computationally efficient image warping method. However, quality of the warped full-color image is a little bit degraded compared with the conventional full-colour image warping. In this paper, a new color image warping is proposed by unifying CFA demosaicking and image warping. The proposed method can be regarded as a generalized image warping from a CFA image to a full-color image in one step. In the proposed method, resultant image quality is almost equal to the full color image warping without significant increase of computational load. The proposed method is applied to lens distortion correction, and results are compared with the RGB full-color image warping and CFA image warping to prove validity of the proposed method. 실시간 컬러 영상 워핑에서 컬러 복원(color reconstruction) 전의 컬러 필터 배열(CFA: Color Filter Array) 영상에 영상 워핑을 적용하면 컬러 영상 워핑에 필요한 보간 연산량을 1/3로 줄임으로써 실시간 성능을 개선할 수 있다. 하지만, RGB 풀 컬러 영상 워핑에 비하여 CFA 영상 워핑의 결과 영상에서는 영상 품질이 떨어지는 한계가 있다. 본 논문에서는 CFA 영상의 컬러 복원과 영상 워핑을 한 단계로 통합하는 방식을 제안한다. 제안하는 방식에서는 영상 품질을 RGB 풀 컬러 영상 워핑 수준으로 유지하면서도 연산량은 크게 증가하지 않는 장점이 있다. 렌즈 왜곡 보정에 적용한 실험 결과를 RGB 풀 컬러 영상 워핑 및 CFA 영상 워핑 결과와 비교하여 제안한 방식의 타당성을 확인한다.
최용준(Yong Joon Choi),류정래(Jung Rae Ryoo),도태용(Tae-Yong Doh) 제어로봇시스템학회 2014 제어·로봇·시스템학회 논문지 Vol.20 No.9
In this paper, a new steering system for a self-balancing electric scooter is proposed with an intuitive steering command input method, where the steering command is generated from the rider’s motion of shifting body to move the center of gravity toward the rotational direction. For the purpose, weight distributions on the rider’s feet are measured using force sensors placed beneath the rider’s feet, and the difference is applied to a steering control system. Stability of the steering system and resultant radius of gyration is investigated by modeling the steering system in consideration of the rider’s motion and centrifugal force. The proposed steering system is applied to experiments, and the results are presented to prove the validity of the proposed method.
실시간 고해상도 컬러 영상 워핑을 위한 FPGA 기반 하드웨어 설계
이유진(You Jin Lee),류정래(Jung Rae Ryoo) 대한전자공학회 2021 전자공학회논문지 Vol.58 No.2
본 논문에서는 고해상도 컬러 영상 워핑의 실시간 처리를 위한 FPGA 기반 하드웨어를 설계한다. 영상 워핑은 입력 영상에 2D 좌표 변환을 적용하는 영상 처리 알고리즘으로 실시간 영상 워핑 구현을 위해서는 좌표 변환 연산, 픽셀 데이터 보간 연산, 그리고 고속 영상 버퍼 메모리 구조 등 3가지 문제에서 실시간 성능 및 정확성을 확보하여야 한다. 본 논문에서는 CFA 컬러 영상 워핑을 활용한 연산량 감소, 오프라인 캐시 스케줄링 및 캐시 메모리 분할 구조를 적용한 영상 데이터 캐시, 그리고 연산의 선후 관계 및 타이밍 조건을 고려한 병렬 처리 및 파이프라인 구조 등을 통하여 실시간 동작 성능을 확보한다. Full HD 해상도의 컬러 영상 입력에 대한 구현된 시스템의 동작 정확성을 PC 소프트웨어의 처리 결과와 비교/확인하고, 실시간 렌즈 왜곡 보정에 적용하여 구현된 시스템의 타당성을 검증한다. This paper presents a design of an FPGA-based hardware for real-time high-resolution color image warping. Image warping is an image processing algorithm applying 2D coordinate transformation to an input image. For real-time processing of image warping, real-time performance and accuracy are required in the following 3 problems, such as, computation of coordinate transformation, interpolation of pixel data, and fast image buffer memory structure. In this paper, real-time performance is guaranteed by the computationally efficient CFA color image warping, image data cache algorithm using offline cache scheduling and cache memory division, and a parallel operation and pipeline structure considering dependencies in operations and timing requirements. The implemented system is applied to some experiments using Full HD color image inputs, and the results are presented in comparison with the results of PC software to show the validity of the designed system.
Design of Repetitive Control Systems Using a Delayed Control Input and a State Error
Tae-Yong Doh,류정래 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.12
This paper presents a modified repetitive control scheme comprising of a state error and a control input via delayed feedback to track periodic reference trajectories and/or attenuate disturbances. The closed-loop state error dynamics can be represented using a typical neutral delay system with an exogenous input to be attenuated. The sufficient conditions to achieve overall stability and H∞ performance to minimize state error are derived by applying a Lyapunov-Krasovskii functional and a Hamiltonian, which are expressed as an algebraic Riccati inequality (ARI) and a linear matrix inequality (LMI). Based on the derived conditions, it is shown that the repetitive controller design problem can be reformulated as an optimization problem with an LMI constraint to determine the state error feedback gain. Finally, a numerical example is presented to demonstrate the feasibility of the proposed method.