• 전력전자학회논문지
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• 제13권3호
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• pp.171-178
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• 2008

본 논문에서는 압력예측기법과 직접 순시토크 제어기법을 통한 유압펌프용 SRM의 압력제어 구동시스템을 제안하였다. 일반적으로 유압 펌프 시스템은 유압센서의 응답성으로 인하여 제어시스템의 시지연이 비교적 길어지게 되며, 이러한 시간지연은 PI 또는 PID 제어 구조에서 장시간의 진동과 불안정화를 만들기 쉽다. 본 논문에서는 시간 지연문제를 해결하고 리플이 없는 압력제어를 위하여 스미스 예측기(simth predictor)를 통한 지연보상과 직접 순시토크제어기법(Direct Instantaneous Torque, 이하 DITC)을 적용하였다. 제안된 제어 방식은 펌프와 센서간의 기구적 문제에 의한 지연문제 해결과 안정성을 확보하고, 펌프 압력제어의 동특성을 향상시키며 전류(轉流, commutation) 구간에서 균일한 토크를 발생시켜 토크 리플을 억제하기 위함이다. 제안된 제어방식은 시뮬레이션과 실험을 통하여 효용성을 검증하였다.

• International Journal of Control, Automation, and Systems
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• 제6권2호
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• pp.186-193
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• 2008

The Internet's low cost and ubiquity present an attractive option for real-time distributed control of processes on the factory floor. When integrated with the Internet, the LonWorks open control network can give ubiquitous accessibility with the distributed control nature of information on the factory floor. One of the most important points in real-time distributed control of processes is timely response. There are many processes on the factory floor that require timely response. However, the uncertain time delay inherent in the network makes it difficult to guarantee timely response in many cases. Especially, the transmission characteristics of the LonWorks/IP network show a highly stochastic nature. Therefore, the time delay problem has to be resolved to achieve high performance and quality of the real-time distributed control of the process in the LonWorks/IP Virtual Device Network (VDN). It should be properly predicted and compensated. In this paper, a new distributed control scheme that can compensate for the effects of the time delay in the network is proposed. It is based on the PID controller augmented with the Smith predictor and disturbance observer. Designing methods for output feedback filter and disturbance observer are also proposed. Tracking position control experiment of a geared DC Servo motor is performed using the proposed control method. The performance of the proposed controller is compared with that of the Internal Model Controller (IMC) with the Smith predictor. The result shows that the performance is improved and guaranteed by augmenting a PID controller with both the Smith predictor and disturbance observer under the stochastic time delay in the LonWorks/IP VDN.

• 한국안전학회지
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• 제15권3호
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• pp.115-123
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• 2000

공압구동기는 다양한 형태의 위험작업 환경하에서 사용되고 있다. 또한, 공압구동기를 적용한 공정은 일반적으로 환경친화적인 것으로 인식되고 있다. 대부분의 경우, 공압구동기는 point to point 제어에 사용된다. 그러나, 최근 공압구동기의 정밀 위치제어에 관한 많은 연구가 수행되고 있다. 본 연구에서는 비례밸브로 구성된 공압구동기의 추종위치제어에 관하여 논의한다. 제안되는 제어기는 압력제어 루프와 위치제어 루프로 구성된다. 공기의 압축성에 기인한 비선형성을 상쇄하기 위하여 되먹임선형화에 의한 PID제어기가 압력제어 루프에 사용된다. 위치제어에는 신경회로망을 사용하여 비선형성을 보상한 PID제어기가 사용된다. 실험결과에 의하면, 제안된 제어기는 공압구동기의 추종성능을 대폭 향상시킬 수 있는 것으로 나타났다.

• 전기학회논문지
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• 제57권6호
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• pp.1048-1057
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• 2008

This paper represents a design method for PID or low-order controllers cascaded with a linear plant in the unit feedback system where it is required to meet the given time response specifications such as overshoot and settling time. This problem is difficult to solve because the zeros of the controller appear in the numerator of the overall system and thus those zeros may make the time response design difficult. In this paper, we propose a new approach based on the partial model matching and the so called K-polynomial. The partial matching problem is formulated to an optimization problem in which a quadratic function of coefficient errors between a target model and the resulting closed loop system is minimized. For the sake of satisfying the closed loop stability, a set of quadratic constraints associated with the cost function is introduced. As a result, the controller designed meets both time response requirements and the closed loop stability, if any. It is shown through several examples that the present method can be easily applied to these problems.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.202-207
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• 1993

A theoretical and experimental study is presented for the force holding control of a miniature robotic ringer which is driven by a pair of piezoelectric unimorph cells. In the theoretical analysis, one finger is modeled as a flexible cantilever with a tactile force sensor at the tip and the mate of the finger is a solid beam supposed with sufficient stiffness. Further, the force sensor is modeled by a one-degree-of-freedom, mass-spring system and the output of sensor is then described by the sensor stiffness multiplied by the relative displacement. The problem investigated in this paper is that two typical holding tasks of the human finger are picked up and applied to the robotic finger. One is the work holding a stationary object with a prescribed, time-varying force and the other one is to keep the contacted force constant even if the object is in motion. The simple PID feedback control scheme is used to control the minute gripping force of order 0.01 Newton. It is shown both experimentally and theoretically that the artificial finger with the piezoelectric actuator works well in the minute force holding of the tiny object.

• 한국정밀공학회지
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• 제17권10호
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• pp.69-76
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• 2000

Lots of semi-active control devices have been developed in recent years because they have the best features of passive and active system. Especially, controllable magneto-rheological(MR) fluid devices have received significant attention in these area of research. The MR fluid is the material that reversibly changes from a free-flowing, linear viscous fluid to a semisolid with a controllable yield strength in milliseconds when exposed to a magnetic field. If the magnetic field is induced by moving a permanent magnet instead of applying current to a solenoid, it is possible to design a MR damper consuming low power because the power consumption is reduced at steady state. This paper proposes valve mode MR damper using permanent magnetic circuit that has wide range of operation with low power consumption, a design parameter is adopted. The magnetic circuit, material of choke and choke type are selected experimentally with the design parameter. The behaviors of the damper are examined and torque tracking control using PID feedback controller is performed for step, ramp and sinusoidal trajectiories.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.68-74
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• 2001

This system is composed of fine and coarse apparatus, measurement system and control system. Piezoelectric actuator is designed for fine positioning. We make a study of precision apparatus that is used in the various industrial machine. The study was carried out to develope a precision positioning apparatus, consisting of servo motor and piezoelectric actuator. Coarse positioning using lead screw is drived by servo motor. Control system output a signal from laser interferometer to amplifier of servo motor and piezoelectric actuator after digital signal processing(DSP). Resolution of this apparatus measure with laser interferometer. In this study, design method and control system with ultra precision position apparatus are researched. As the first step, we have estimated for control performance and system stability before an actual apparatus is manufactured by MATLAB with SIMULINK including various functions those are composed of pre-design and system modeling.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 D
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• pp.2179-2181
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• 2004

Model-free Method들 중에 반복 피트백 조절 알고리즘(Iterative Feedback Tuning, IFT)는 특정한 성능지수를 정의하고, 이를 최소화하도록 제어기의 게인들을 조절하는 방법을 제시하였다. PID와 같은 고전적인 제어이론에 근거한 제어기 설계 과정과는 달리, IFT 알고리즘은 반복 실험을 통해 성능지수의 Gradient를 구하여 이로부터 필터 게인들 조정하는 방법을 채택하고 있다. 수학적 증명과 실험적 실증을 통하여 IFT의 수렴성과 유용성이 보여짐에도 불구하고 IFT 알고리즘의 한계점은 단일 성능지수의 사용이라는데 있다. 이를 개선하기 위해서는 단일 제어 목적을 위한 단일 성능지수의 사용이 아닌 복수의 제어 목적을 위한 복수의 성능지수의 사용이 필요하다. 본 논문에서는 두 개의 성능지수를 가지는 IFT를 이용해서 위상 여유가 크고, 대역폭이 넓은 제어기를 설계하기 위해서 제어기 게인을 자동 조절하는 알고리즘을 제안하고 ODD에서 사용되는 플랜트에 적용한 모의실험을 통하여 그 유용성을 보였다.

• 한국공작기계학회논문집
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• 제11권1호
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• pp.17-25
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• 2002

This system is composed of fine and coarse apparatus, measurement system and control system. Piezoelectric actuator is designed far fee positioning. We make a study of precision apparatus that is used in the various industrial machine. The study was carried out to develope a precision positioning apparatus, consisting of servo motor and piezoelectric actuator Coarse positioning using lead screw is thrived by servo motor. Control system output a signal from laser interferometer to amplifier of servo motor and piezoelectric actuator after digital signal processing (DSP). Resolution of this apparatus measure with laser interferometer. In this study, design method and control system with ultra precision position apparatus are researched. As the first step, we have estimated for control performance and system stability before an actual apparatus is manufactured by MATLAB with SIMUUNK including various frictions those are composed of pre-design and system modeling.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.433-439
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• 2000

Lots of semi-active control devices have been developed in recent years because they have the best features of passive and active system. Especially, controllable magneto-rheological(MR) fluid devices have received significant attention in these area of research. The MR fluid is the material that reversibly changes from a free-flowing, linear viscous fluid to a semisolid with a controllable yield strength in milliseconds when exposed to a magnetic field. If the magnetic field is induced by moving a permanent magnet instead of applying current to a solenoid, it is possible to design a MR damper consuming low power because the power consumption is reduced at steady state. This paper proposes valve mode MR damper using permanent magnetic circuit that has wide range of operation with low power consumption and small size. To design a MR damper that has a large maximum dissipating torque and a low damping coefficient, a design parameter is adopted. The magnetic circuit, material of choke and choke type are selected experimentally with the design parameter. The behaviors of the damper are examined and torque tracking control using PID feedback controller is performed for step, ramp and sinusoidal trajectories.