• 전자공학회논문지SC
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• 제45권1호
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• pp.1-8
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• 2008

자유롭고 빠르게 이동할 수 있도록 도와주는 개인 이동 수단인 two-wheel balancing vehicle은 inverted pendulum 시스템의 원리를 이용한 것으로, 최근 들어 많은 연구가 이루어지고 있고 이를 이용한 제품이 실제 사용되고 있다. 본 논문에서는 일반적인 PID 제어이론을 이용한 two-wheel balancing vehicle에 대한 제어성능을 개선시키는 새로운 제어방식을 제안한다. 제안한 방식은 퍼지 PD+I 제어방식으로 향상된 PID 제어의 일종으로 2개의 입력과 1개의 출력을 가진 퍼지시스템에 적분 신호를 더함으로써 출력신호를 만든다. 퍼지시스템의 비선형성은 시간공정에서 비례신호와 미분신호의 가중치를 변화함으로써 최적의 출력제어신호를 만들어낸다. 제안한 퍼지 PD+I 제어방식의 유용성을 알아보기 위해 two-wheel balancing mobile robot에 대해 시뮬레이션과 실험의 결과를 통해, 제안한 퍼지 PD+I 제어방식이 일반적인 PID 방식보다 우수한 성능을 가지고 있음을 알 수가 있다.

• 대한조선학회논문집
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• 제28권1호
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• pp.38-52
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• 1991

자유표면하에서 움직이는 임의의 형상의 3차원 물체로 인한 비선형 유체력을 준 Lagrangian 방법을 사용하여 해석하였다. 경계치 문제는 경계 적분 방법(Boundary Integral Method)을 이용하여 해결하였으며, 물체와 자유 표면의 형상은 곡면 Panel로 표현하였다. 이들 표면은 hi-cubic B-spline 방법을 사용하여 유한개의 작은 표면 요소로 나뉘어지게 되며, 또한 \phi와 (equation omitted) 표면 요소상에서 bi-linear하다고 가정한다. 특이점에 의한 유기 포텐시얼의 계산시 1/R에 비례하는 부분은 제거하고 해석적으로 처리하였다. 물체로부터 멀리 떨어진 곳에서의 유체 유통은 좌표계의 원점에 위치한 Dipole로 표현하였으며, Time Stepping시 Runge-Kutta의 4차 방법을 사용하였다. 3차원인 경우에 대한 적분 방정식과 포텐시얼의 시간 미분간에 대한 경계 조건이 유도되었으며, 이러한 식들을 사용하여 자유표면의 형상과 물체의 운동을 동시에 계산하였다. 대진폭을 가지고 규칙적으로 진동하는 물체에 작용하는 힘과 이때의 자유 표면 형상을 계산하고 기 발표된 자료와 비교하여 보았으며, 자유표면 근처에서 운동하는 물체에 작용하는 비선형 효과를 관찰하였다.

• 드라이브 ㆍ 컨트롤
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• 제12권4호
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• pp.60-70
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• 2015

A front-end loader (FEL) mounted on an agricultural tractor is one of the most commonly used implements for farm work. However, when the tractor carries material using the bucket attached to the FEL on a sloping ground, the materials can spill or roll back over the operator due to the tilted body, thereby requiring the bucket surface to remain level at a constant value regardless of varying slopes. In this study, an active system for controlling the angle of the FEL bucket on a tractor based on the real-time measurement of ground slopes was developed to enable the bucket to constantly remain level. A FEL simulator operated based on an electro hydraulic proportional valve (EHPV) was constructed in the laboratory to develop a proportional-integral-derivative (PID) controller forming a virtual electronic control unit (ECU) on the computer, which could automatically adjust the bucket angles depending on varying input angles while sending SAE-J1939 associated messages via CAN BUS to the EHPV. The different parameter values for the PID controller due to the gravity effect of the bucket were determined using a manual PID tuning method while assuming that the tractor travels on either an ascending slope or a descending slope. The developed PID control-based self-leveling system showed a mean of steady-state errors of within $1^{\circ}$ and a mean of delayed times of ~ 0.8s when the step input of $+20^{\circ}$ was given, implying that the developed system and control algorithm would be effective in maintaining the bucket angle at a certain value. Future studies include the improvement of the control algorithm to reduce such a time delay as well as the application of the developed algorithm to the FEL mounted on a tractor tested at a testing ground.

• 대한기계학회논문집A
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• 제40권1호
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• pp.1-8
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• 2016

본 논문에서는 기존의 관성안정화 플랫폼에서 보편적으로 사용됐던 PID 제어에 외란관측기를 적용하는 알고리즘 제안한다. 외란관측기 알고리즘을 적용하기 위하여 직접구동 모터로 구동되는 안정화 플랫폼 축의 관성모멘트와 축 마찰 특성을 실험적으로 구하고, 시뮬레이션과 실험결과를 비교하여 정확도를 검증하였다. 또한 차수와 상대차수가 다른 여러 가지 Q-filter 적용실험을 통하여 필터 특성에 따른 시스템의 안정성을 확인하였다. 본 논문에서 제안한 알고리즘은 6 자유도 시뮬레이터를 이용하여 차량 모션 인가실험을 통해 이중 PID 제어 루프의 결과와 비교/검증하였다.

• Smart Structures and Systems
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• 제20권1호
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• pp.85-97
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• 2017

The aim of this research is to develop a new method to use magnetorheological (MR) damper for vibration control. It is a new way to achieve the MR damper response without the need to have detailed constant parameters estimations. The methodology adopted in designing the control structure in this work is based on the experimental results. In order to investigate and understand the behaviour of an MR damper, an experiment is first conducted. Force-displacement and force-velocity responses with varying current have been established to model the MR damper. The force for upward and downward motions of the damper piston is found to be increasing with current and velocity. In cyclic motion, which is the combination of upward and downward motions of the piston, the force with hysteresis behaviour is seen to be increasing with current. In addition, the energy dissipated is also found to be linear with current. A proportional-integral-derivative (PID) controller, based on the established characteristics for a quarter car suspension model, has been adapted in this study. A fuzzy rule based PID controller (F-PID) is opted to achieve better response for a varying frequency input. The outcome of this study can be used in the modelling of MR damper and applied to control engineering. Moreover, the identified behaviour can help in further development of the MR damper technology.

• Korean Chemical Engineering Research
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• 제49권5호
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• pp.565-570
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• 2011

시간지연이 없는 다양한 범주의 안정, 적분, 불안정 공정에 대하여 비례-적분-미분(PID) 제어기의 해석적 조율 방법을 제안하였다. 2자유도 제어구조와 내부모델 제어에 기반한 제안된 방법은 설계가 간단하고 직접적이며 공정산업에 쉽게 구현할 수 있어 강화된 설정점 추종과 외란제거 성능을 얻는데 유용하게 사용될 수 있다. 몇몇 대표적 공정에 대하여 강건성을 같게 유지하면서 기존 설계 방법과 비교한 결과, 제안된 방법의 우수한 폐루프 성능을 확인하였다.

• 한국미생물·생명공학회지
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• 제21권4호
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• pp.354-365
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• 1993

A novel control method with automatic tuning of PID controller parameters has been developed for efficient regulation of dissolved oxygen concentration in fed-batch fermentations of Escherichia coli. Agitation speed and oxygen partial pressure in the inlet gas stream were chosen to be the manipulated variables. A heuristic reasoning allowed improved tuning decisions from the supervision of control performance indices and it coule obviate the needs for process assumptions or disturbance patterns. The control input consisted of feedback and feedforword parts. The feedback part was determined by PID control and the feedforward part is determined from the feed rate. The proportional gain was updated on-line by a set of heuristics rules based on the supervision of three performance indices. These indices were output error covariance, the average value of output error, and input covariance, which were calculated on-line using a moving window. The integral and derivative time constants were determined from the period of output response. The specific growth rate was maintained at a low level to avoid acetic acid accumulation and thus to achieve a high cell density. The specific growthe rate was estimated from the carbon dioxide evolution rate. In fed-batch fermentation, the simutaneous control of dissolved oxygen concentration (at 0.2; fraction of saturated value) and specific growth rate (at 0.25$hr^{-1}$) was satisfactory for the entire culture period in spite of the changes in the feed rate and the switching of control input.

• 한국해양공학회지
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• 제25권6호
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• pp.1-8
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• 2011

This paper describes a new method for a digital gas metal arc welding (GMAW) system. The GMAW system is an arc welding process that incorporates the GMAW power source (PS-GMAW) with a wire feed unit (WFU). The PS-GMAW requires an electric power of constant voltage. A constant magnitude is maintained for the arc current by controlling the wire-feed speed of the WFU. A mathematical model is derived, and a self-tuning fuzzy proportional-integral-derivative (PID) controller is designed and applied to control the welding current. The electrode wire feeding mechanism with this controller is driven by a DC motor, which can compensate for both the molten part of the electrode and undesirable fluctuations in the arc length during the welding process. By accurately maintaining the output welding current and welding voltage at constant values during the welding process, excellent welding results can be obtained. Simulation and experimental results are shown to prove the effectiveness of the proposed controller.

• 한국소음진동공학회논문집
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• 제27권1호
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• pp.28-35
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• 2017

최근 기존의 유압 차량 리프트는 높이제어의 어려움으로 인해 기술개발의 한계에 직면하였다. 휠 얼라이먼트나 차량의 하중 분포에 따른 미세한 불규칙적인 변형을 보상하기 위해서는 매우 정밀한 위치 제어성이 요구되고 있다. 이 연구에서는 이러한 기존 리프트 시스템의 한계를 해결하고자 매우 정교한 압력강하를 이끌어낼 수 있는 MR 밸브 시스템을 활용하여 새로운 차량 리프트를 제안하고 이에 대한 분석을 진행한다. 우선적으로 MR 밸브의 요구되는 성능을 파악하기 위해 유압 리프트의 운동방정식을 설립하고, 요구되는 압력강하를 얻기 위해 MR 밸브를 설계한다. 또한 정밀한 위치 제어 성능을 얻기 위해 PID 제어기를 설립하고, 시뮬레이션을 통해 제안된 시스템의 제어성을 검증한다.

• Journal of Biosystems Engineering
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• 제35권4호
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• pp.224-230
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• 2010

The purpose of this study was to develop position control system of an electric actuator for automatic shuttle shifting of a tractor. The electric actuator was installed at the link of the forward-reverse gearshift of the tractor transmission, and controlled in the ranges of forward, neutral, and reverse positions. The position control system of the electric actuator was developed based on PID (Proportional Integral Derivative) controller and transfer function of the electric actuator. The coefficients of the PID controller were determined by Ziegler-Nichols (Z-N) method and optimized using simulation program. The prototype AMT (Automated Manual Transmission) test unit of the tractor was installed and used to evaluate the performance of the position control. The evaluation system for the control performance consisted of forward-reverse actuator, motor driver, and controller. The tests were conducted as the controlled positions of the actuator were changed from neutral position to forward, neutral, and reverse positions in sequence. The sequential tests were repeated 20 times. The operations of changing the gearshift were considered as the step response of the control system. Maximum overshoot, settling time, and steady-state error were analyzed. The results showed that performance of the position control system was reasonable and qualified. The maximum overshoots, the steady-state errors, and the settling times of the position control system were 10~20%, 1~5%, and 0.92~1.49 sec, respectively. The modifications of the electric actuator will be required to enhance the performance of position control during field operation.