• 한국산학기술학회논문지
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• 제9권5호
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• pp.1178-1183
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• 2008

슬라이딩 모드를 가진 가변 구조 제어(VSC)는 비선형 시스템의 현대제어에서 중요하고 흥미로운 주제이다. 그러나, VSC에서의 불연속적인 제어 법칙은 실제로 바람직하지 못한 떨림 현상을 발생시킨다. 본 논문에서는 이러한 문제점을 해결하기 위해 신경망 슬라이딩 곡면을 갖는 VSC 구조를 제안한다. 불연속 제어 법칙을 해결하기 위해 경계층을 가진 신경망 슬라이딩 곡면이 도입된다. 제안된 제어기는 보편적인 VSC의 떨림 현상 문제를 해결할 수 있다. 제안된 제어 구조의 효과는 시뮬레이션을 통해 증명하였다.

• 한국산학기술학회논문지
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• 제10권10호
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• pp.2634-2638
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• 2009

슬라이딩 모드를 가진 가변 구조 제어(VSC)에서의 불연속적인 제어 법칙은 실제로 바람직하지 못한 떨림 현상을 발생시킨다. 본 논문에서는 이러한 문제점을 해결하기 위해 신경망 슬라이딩 곡면을 갖는 VSC 구조를 제안한다. 불연속 제어 법칙을 해결하기 위해 경계층을 가진 신경망 슬라이딩 곡면이 도입된다. 제안된 제어기는 보편적인 VSC의 떨림 현상 문제를 해결할 수 있다. 제안된 제어 구조의 효과는 시뮬레이션을 통해 증명하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.519-523
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• 1993

In this paper, the variable structure model following control scheme is proposed for the nonlinear robot manipulator system. The proposed control system guarantees that the system state is in the sliding mode for all time. Therefore, error transient can be prescribed in advance for all time. Furthermore, overall system is globally exponentially stable. Chattering problem is reduced by the introduction of a boundary layer. Simulation results are given to show the usefulness of the proposed control scheme.

• 한국정밀공학회지
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• 제19권7호
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• pp.154-162
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• 2002

The effect of nonlinear friction in the low velocity is dominant in precise controlled mechanisms and it is difficult to model. This paper is concerned with the compensation for friction using the variable structure system approach as nonmodel based method. The problem of chattering in the sliding mode controller is suppressed by the implementation of the boundary layer concept. And the estimation for friction using sliding mode observer makes the upper bound of matched uncertainty reduced. Accordingly, the effect of chattering can be more suppressed. And the sliding surface is constructed by adding an integral component to the switching function that is made by using error dynamics. This sliding surface guarantees the good tracking performance. Experimental results for a XY table system show that the proposed method has a good performance especially in the low velocity.

• 제어로봇시스템학회논문지
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• 제16권3호
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• pp.256-263
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• 2010

The paper proposes a sensorless speed control strategy for a PMSM (Permanent Magnet Synchronous Motor) based on a new SMO (Sliding Mode Observer), which substitutes a signum function with a sigmoid function. To apply robust sensorless control of PMSM against parameter fluctuations and disturbance, the high speed SMO is proposed, which estimates the rotor position and angular velocity from the back EMF. The low-pass filter and additional position compensation of the rotor are used to reduce the chattering problem commonly found in sliding mode observer with signum function, which becomes possible by applying the sigmoid function with the control of a switching function. Also the proposed sliding mode observer with the sigmoid function has better efficiency than the conventional sliding mode observer since it adjusts the observer gain by variable boundary layer and estimates the stator resistance. The stability of the proposed sliding mode observer is verified by the Lyapunov second method in determining the observer gain. The validity of the proposed high speed PMSM sensorless velocity control has been demonstrated by real experiments.

• Korea-Australia Rheology Journal
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• 제18권4호
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• pp.171-181
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• 2006

We present a short review for authors' previous work on direct numerical simulations for inertialess hard particle suspensions formulated either with a Newtonian fluid or with viscoelastic polymeric fluids to understand the microstructural evolution and the bulk material behavior. We employ two well-defined bi-periodic domain concepts such that a single cell problem with a small number of particles may represent a large number of repeated structures: one is the sliding bi-periodic frame for simple shear flow and the other is the extensional bi-periodic frame for planar elongational flow. For implicit treatment of hydrodynamic interaction between particle and fluid, we use the finite-element/fictitious-domain method similar to the distributed Lagrangian multiplier (DLM) method together with the rigid ring description. The bi-periodic boundary conditions can be effectively incorportated as constraint equations and implemented by Lagrangian multipliers. The bulk stress can be evaluated by simple boundary integrals of stresslets on the particle boundary in such formulations. Some 2-D example results are presented to show effects of the solid fraction and the particle configuration on the shear and elongational viscosity along with the micro-structural evolution for both particles and fluid. Effects of the fluid elasticity has been also presented.

• 전기학회논문지
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• 제60권11호
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• pp.2139-2146
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• 2011

In this paper, a robust adaptive controller is proposed for trajectory tracking of robot manipulators with the unknown friction coefficient and bounded disturbance. A new adaptive control law is developed based on sliding mode and derived from the Lyapunov stability analysis. The introduction of a boundary layer solves the problem of chattering. The proposed adaptive controller is globally asymptotically stable and guarantees zero steady state error for joint positions. The estimated friction coefficients can also approach the actual coefficients asymptotically. A simulation example is provided to demonstrate the performance of the proposed algorithm.

• 로봇학회논문지
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• 제7권1호
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• pp.20-28
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• 2012

In spite of the difficulties and uncertain characteristic of cable driven method, surgical robot instrument has adopted it as driving mechanism for various reasons. To overcome the problem of cable system, previous research applied SMCSPO (sliding mode control with sliding perturbation observer) algorithm as robust controller to control the instrument and found that the value of SPO (sliding perturbation observer) followed force disturbance, reaction force loaded on the tip very similarly. Thus, this paper confirms that the perturbation observer is sufficient estimator which finds out the mount of loaded force on the surgical robot instrument. To prove the proposition, simulation using the similar model with an actual instrument and experimental evaluation are performed. The results show that it is possible to substitute SPO for sensors to measure the reaction force. This estimated reaction force will be used to realize haptic function by sending the reaction force to a master device for a surgeon. The results will contribute to create surgical benefit such as shortening the practice time of a surgeon and giving haptic information to surgeon by using it as haptic signal to protect an organ by making force boundary.

• 농업과학연구
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• 제25권1호
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• pp.97-106
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• 1998

본 연구는 현재 산사태 대책수립에 많이 이용되고 있는 원호활동 해석방법의 문제점을 규명하기 위하여 실시되었으며, 여기서 얻어진 결과를 요약하면 다음과 같다. 1. 40개의 모델사면을 지층에 따라 활동면을 분석해 본 결과, 풍화토와 풍화암의 경계 부분이 다른 부분에 비하여 활동이 일어날 가능성이 높은 것으로 나타났다. 2. 우리나라에서 발생하는 산사태의 대부분이 깊이 2m를 전후로 하여 토층의 경계부근등 주로 불연속면을 따라 발생하기 때문에 절취사변에 대한 산사태의 안정해석을 할때, 무한사면해석을 우선 고려하는 것이 안전한 설계가 될 것으로 판단된다. 3. 사면경사가 일정한 상태에서 사면길이만을 변화 시켰을 경우, 원호활동사면인 경우는 토층이 얕고 사면길이가 짧을수록 안전하였으나 무한사면인 경우는 사면길이에 관계없이 최소안전율은 동일하였다. 4. 우리나라 산사태의 대부분을 차지하는 사면경사 $30^{\circ}$의 조건으로 원호활동해석과 무한활동해석으로 분석한 결과, 상호간의 최소안전율의 차이가 많으며 원호활동해석 방법은 무한활동해석에 비해 과다하게 안전측으로 나타났다.

• 대한기계학회논문집
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• 제17권7호
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• pp.1658-1667
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• 1993

In this research, a numerical algorithm has been developed, which can be applied to the large deformation and large displacement contact problems between two deformable bodies. The contact conditions expressed in terms of the rate of angle change have been proposed considering the change in geometric shape and rate of contact force. A set of linear simultaneous equations is constructed by adding the geometric shape change and contact conditions to the original stiffness matrix. A new method to determine time increment has been proposed based on Euler method, in which the condition to prevent the contact bodies from penetrating and overrunning each other has been taken into consideration. Practical application to contact problem is extrusion in which bodies are sliding along the contact boundary.