복수기 수실 진공유지 공정개선으로 설비 신뢰도 향상 개선사례

이상덕,최호택,민장섭 한국품질경영학회 2020 한국품질경영학회 학술대회 Vol.2020 No.-

복수기란 발전소 터빈을 회전시킨 배기 증기를 응축시키기 위해 내부를 대기압 이하로 낮춤으로써, 증기가 보유한열 낙차를 크게 하여 터빈 효율을 향상시키는 장치이다. 내부 구조는 동체(Shell), 수실(Water Box), 튜브, 복수조(Hot well)로 구성되어 있다. 수실은 냉각수 유량에 의한 복수기 증기 효율을 높이기 위해 정상운전 중 670mmHg 이상의 진공상태를 유지하는 것이 매우 중요하나 645mmHg로 진공도 저하가 발생되었다. 본 사례는 수실 진공유지공정 진공도 저하원인과 구성설비의 고질적 문제를 원인분석과 통계적 품질개선 기법을 활용하여 설비 신뢰도를 향상시킨 사례이다. 1. 수실의 진공을 생성하는 진공펌프의 임펠러 국부부식 발생으로 흡ㆍ배기구 간격이 증가하여 펌프의 성능이 저하되는 문제를 해결하기 위해 인장강도 및 항복강도, 내식성 등을 고려하여 아이디어 평가를 통해 임펠러의 재질을 STS316L로 변경ㆍ적용하였다. 2. 진공펌프 임펠러 질량 불균형으로 언밸런스 성분 증가에 의한 펌프 진동상승의 문제점 개선을 위해 벡터도 분석을 통한 웨이트 부착각도 및 중량 계산 등 기술검토를 통해 웨이트 발란싱 조정으로 펌프 진동을 최소화하였다. 3. 열교환기 튜브 누설에 의한 냉각 효율 저하로 밀봉수 온도 상승 문제를 해결하기 위해 내식성, 운전조건 등을 고려하여 티타늄 재질로 변경하여 튜브 누설 압력시험을 통해 검증 및 밀봉수 온도 상승을 방지하였다. 4. 드레인 트랩 배출 부적합에 의한 탱크 수위 상승으로 진공펌프가 과열되는 문제를 해결하기 위해 트랩 배출조건을 개선하여 탱크 수위상승을 최소화하였다. 위의 개선을 통해 복수기 수실의 진공은 670mmhg이상으로 유지되고 있으며, 진공유지를 위하여 점검항목을 설정하고 지속 관리중에 있다.

대학생의 부모 애착과 학업적 자기효능감의 관계

이상덕,홍계옥 경주지역발전협의회 부설 경주발전연구원 2015 경주연구 Vol.24 No.2

The purpose of this study was to investigate the relationships of college student-parents' attachment on their self-efficacy for academic attainment. The data was collected by questionnaires method from 555 college students. The instruments were college student-parents' attachment and self-efficacy for academic attainment. The results of the study were as follows : College students' self-efficacy for academic attainment relations meaningfully related to attachment to their parents. The relationships of college students' self-efficacy for academic attainment and attachment to their parents showed positively, especially more positively to their mothers. The relationship of college student attachment to parents and their self-efficacy for academic attainmentdiffered according to their sex. Male students' attachment to parents have more likely related to their self-efficacy for academic attainment.

인(人) 또는 재산에 대한 고의적 침해의 항변

이상덕 한국사법행정학회 1986 사법행정 Vol.27 No.7

외란관측기 설계를 위한 Q필터 시정수 영향 분석 : 외바퀴 로봇의 균형 제어 응용

이상덕,정슬,Lee, Sangdeok,Jung, Seul 대한전자공학회 2016 전자공학회논문지 Vol.53 No.10

본 논문에서는 외바퀴 로봇의 균형 제어 성능을 향상할 목적으로 외란관측기를 사용한다. 외란관측기의 설계는 역 공칭 모델 설계와 Q필터 설계의 두 과정으로 구성된다. 외바퀴 로봇의 역 공칭 모델을 역 스틱 모델로 부터 유도하고 역 공칭 모델의 안정화를 위한 Q필터를 설계한다. 이 과정에서 Q31의 형태를 갖는 필터를 설계하고 Q필터 시정수의 영향에 관한 실험적인 검증 결과를 제시한다. 시정수는 외란 억제 대역폭을 결정하는 역할을 하지만 외란 억제와 센서 잡음 내성은 상보적인 특성을 갖고 있다. 그러므로 전체 시스템을 고려하여 적절한 시정수가 선택되어야만 한다. 이를 해결하기 위해 3개의 서로 다른 시정수가 외란관측기에 각각 사용되었을 때의 제어 성능을 비교하는 실험을 수행한다. 결과 분석을 바탕으로 한 바퀴 로봇의 균형 제어에 대한 외란관측기 설계에 적합한 시정수 변수의 설계 범위를 제안한다. Disturbance Observer(DOB) based control is considered for the purpose of the balancing performance enhancement in a single-wheel robot. Design of DOB can be folded into two parts, the inverse model of the plant and the Q-filter. The inverse model is derived from the inverted stick model and a Q-filter is designed to stabilize the inverse model. In this paper, a Q31 filter is designed and its effect is evaluated by experimental studies. The time constant provides a complimentary characteristic between the disturbance suppression and the sensor noise immunity. Therefore, suitable selection of the time-constant must be considered. Comparative experiments are conducted to investigate the control performances when three different Q filters are respectively applied in the DOB. Through the analysis of the experimental results, a time constant is designed to have a proper value in the design of DOB for balancing control of a single-wheel robot.

노동자용역대여사업의 문제점

이상덕 한국노동법학회 1995 노동법학 Vol.- No.5

일본의 VAN 사업현황 및 전망

이상덕,Lee, Sang-Deok 한국정보통신집흥협회 1989 정보화사회 Vol.18 No.-

Awakening Strategies from a Sleeping Mode to a Balancing Mode for a Sphere Robot

이상덕,정슬 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.6

This paper presents the strategy of awakening a sphere robot from a sleep mode to a balancing mode. The sphere robot is designed on the basis of a single-wheel robot covered with two hemispheres to have the sphereshape with casters to maintain the sleep mode at a specific angle. The sleep angle has been empirically found tobe 16 degrees for enabling the sphere robot to be upright position. The gyroscopic force is controlled to performthe awakening strategy of the robot system. Firstly, the key design features such as angular momentum, agility,and controllable bandwidth are investigated to identify three phases such as triggering, stumbling, and stabilizingfor the awakening strategy. Secondly, the sphere robot is modeled as an inverted stick and the phase portrait of themodel is analyzed. Thirdly, a control law with a compensation algorithm is proposed to enhance the stabilizingperformance. Finally, the proposed awakening strategy is verified through experimental studies.

Practical Implementation of a Factorized All Pass Filtering Technique for Non-minimum Phase Models

이상덕,정슬 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.3

One of the problems of the inverse model-based control techniques is the stability of the identified inverse model after the estimation process by the recursive least square (RLS) method. One solution is to use the all pass filtering (APF) technique to transform non-minimum phase models into minimum phase models [9]. However, there are several cases not cured by the all pass filtering method when the all pass filter algorithm is implemented on the hardware. In this paper, an improved version of the all pass filtering technique is presented to deal with the non-minimum phase models. The factorized APF (fAPF) technique for non-minimum phase models is presented to suggest a simple solution. A simple method for avoiding the calculation of complex numbers is also presented for the easy implementation. Several examples are given to support the proposal.

Experimental Verification of a Novel Quad-RLS Technique for Improving Real-time System Identification Performance : A Practical Approach to CMG

이상덕,정슬 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.6

This paper presents a Quad RLS(Q-RLS) technique with four RLSs under a fixed forgetting factor condition to improve the identification performance of a dynamical system in a real-time fashion. Although an adaptive RLS method with a variable forgetting factor and a higher order model may provide the modeling accuracy, their implementations are not easy because of leakage effects and relatively complex modeling. In practice, the fixed forgetting factor is still used for the RLS-based system identification. Therefore, a novel Q-RLS scheme with concurrent four RLSs is proposed as an alternative way for the better estimation performance in an on-line fashion. In the Q-RLS scheme, the first pair of the forward and inverse RLSs is to identify the forward and inverse models independently. The second pair of the forward and inverse RLSs is to improve the identification of the previously identified model. The proposed approach has several advantages: 1) The RLS with a fixed forgetting factor can avoid the leakage problem. 2) Both forward and inverse models are separately identified to improve the accuracy. 3) Q-RLS can have the 4th order filter structure, but provide the better identification performance. Three schemes such as a second-order RLS, a fourth-order RLS, and the Q-RLS are experimentally tested and their performances are compared for the state observation accuracy of the control moment gyroscope(CMG) system.

A Decentralized Model Identification Scheme by Random-work RLS Process for Robot Manipulators: Experimental Studies

이상덕,배영걸,정슬 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.7

In this paper, a parameter identification method by randomly excited trajectories for decentralized jointsof robot manipulators is presented. Each joint of a robot manipulator is decoupled and identified as a secondorder linear equation by a recursive least square method. Although robot manipulators are a nonlinear and coupledsystem, decentralized models are required for either the independent joint control such as model-based linear controlmethods, a time-delayed control (TDC) method or the input torque estimation. The random walk-based parameteridentification scheme of using a recursive least square (RLS) method is applied to a mobile manipulator, KOBOKERas a test-bed. Then the identified models are used for designing a state observer to estimate the states of KOBOKERmore accurately when the robot follows the sinusoidal trajectory. The accuracies of the identified model and theestimated state are verified experimentally by comparing with the torque of a linearized motion equation.