• Smart Structures and Systems
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• 제6권8호
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• pp.921-938
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• 2010

Most of studies on control of beams containing piezoelectric sensors and actuators have been based on linear quadratic regulator (LQR) with state feedback or output feedback law. The aim of this study is to develop velocity-acceleration feedback law in the optimal control of smart piezoelectric beams. A new controller which is an optimal control system with velocity-acceleration feedback is presented. In finite element modeling of the beam, the variation of mechanical displacement through the thickness is modeled by a sinus model that ensures inter-laminar continuity of shear stress at the layer interfaces as well as the boundary conditions on the upper and lower surfaces of the beam. In addition to mechanical degrees of freedom, one electric potential degree of freedom is considered for each piezoelectric element layer. The efficiency of this control strategy is evaluated by applying to an aluminum cantilever beam under different loading conditions. Numerical simulations show that this new control scheme is almost as efficient as an optimal control system with state feedback. However, inclusion of the acceleration in the control algorithm increases practical value of a system due to easier and more accurate measurement of accelerations.

• Journal of Mechanical Science and Technology
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• 제18권8호
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• pp.1288-1296
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• 2004

Wall-following control problem for a mobile robot is to move it along a wall at a constant speed and keep a specified distance to the wall. This paper proposes wall-following controllers based on Lyapunov function candidate for a two-wheeled mobile robot (MR) to follow an unknown wall. The mobile robot is considered in terms of kinematic model in Cartesian coordinate system. Two wall-following feedback controllers are designed: full state feedback controller and observer-based controller. To design the former controller, the errors of distance and orientation of the mobile robot to the wall are defined, and the feedback controller based on Lyapunov function candidate is designed to guarantee that the errors converge to zero asymptotically. The latter controller is designed based on Busawon's observer as only the distance error is measured. Additionally, the simulation and experimental results are included to illustrate the effectiveness of the proposed controllers.

• 감성과학
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• 제12권4호
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• pp.531-544
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• 2009

HCI 분야에서 사용성은 시스템의 객관적인 사용성에 초점을 둔 것에서 점차 사용자들이 시스템을 사용하면서 느끼는 주관적인 경험을 중시하는 개념으로 확장, 변화하고 있다. 오늘날 대부분의 사람들은 휴대전화를 소지하고 사용한다. 휴대전화와 같이 인간과의 상호작용 빈도가 높은 인터페이스에서 보다 긍정적인 사용자의 주관적 경험을 유발하는 것은 중요하다고 볼 수 있다. 본 연구에서는 감정을 표현하는 인터페이스가 인간에게 보다 긍정적인 사용자 경험을 유발할 것이라는 가설 하에 감정을 표현하는 인간 목소리를 통해 청각적 피드백을 제공하는 휴대전화 프로토타입(prototype)을 제작한 후, 감정을 표현하기에 적절하지 않은 기계음을 통해 청각피드백을 제공하는 휴대전화 조건과의 비교를 통해 어떠한 조건에서 사용자들이 보다 더 긍정적인 사용자 경험을 느끼는지, 어떠한 조건을 더 선호하는지에 대해 알아보았다. 구체적으로, 참가자들은 4가지 종류의 휴대전화 프로토타입(청각적 피드백이 없는 무음 조건, 사람의 목소리를 통해 청각적 피드백을 제시하는 조건, 기계음을 통해 청각적 피드백을 제시하는 조건, 기계음과 사람의 목소리를 모두 제공하는 혼합음 조건)을 경험한 후, 그에 대한 경험적 사용성(재미, 흥미, 불쾌감), 유희적 측면(HQ) 그리고 선호도를 평정하였다. 결과적으로, 사용자들은 사람의 목소리를 통해 정서를 표현하는 조건의 휴대전화에 대해 청각적 피드백을 제공하지 않는 휴대전화나 기계음을 통해 청각적 피드백을 제시하는 휴대전화와 비교해서 상대적으로 높은 지각적 재미와 유희(HQ)를 느끼는 것으로 드러났다. 하지만 선호도는 다른 조건에 비해 낮은 수준의 평정치를 보이는 것으로 나타났다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1673-1678
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• 2005

This paper addresses both theoretical and experimental studies of the stability of haptic interfaces during the simulation of virtual Coulomb friction. The first objective of this paper is to present an analysis of how friction affects stability in terms of the describing function method and the absolute stability theory. Two different feedback methods are introduced and are used to evaluate the analysis: an active force feedback, using a motor, and a passive force feedback, using controllable brake. The second objective of this paper is to present a comparison of the theoretical and experimental results. The results indicate that the sustained oscillations due to the limit cycle occur when simulating friction with an active force feedback. In contrast, a passive force feedback can simulate virtual friction without the occurrence of instability. In conclusion, a hybrid active/passive force feedback is proposed to simulate a highly realistic friction display.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
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• pp.890-895
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• 1989

This paper discusses the regulator problem of minimizing the input energy for the multi-input linear time-invariant discrete-time system with the zero terminal state. The optimal inputs are expressed by the state feedback form and they are made up of three phases. The optimal feedback gains are independent of the initial state.

• 대한기계학회논문집A
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• 제20권10호
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• pp.3173-3185
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• 1996

Multi-model vibration control of laminated composites plates for various fiver orientations has been carried out by making use of piezolectric materials(PZT) as sensors and actuators. Cantilever plate is used as a specimen to test multi-modal vibration supression under random exitation. Impulse technique is applied to determine the natural frequency, the damping ratio(.zeta.) and the modal damping(2.zeta..omega.) of the first bending and the trosion modes. Two independent controllers are implemented to control the two modes simultaneously and established digitally on the basis of the direct negative velocity feedback control with collocated sensor/actuator. Experimental results for various fiber orientations and feedback gains are compared with finite element analysis considering stiffnesses and dampings of piezoeletiric sensors, actuators and bonding layer.

• 대한기계학회논문집A
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• 제27권12호
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• pp.2079-2084
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• 2003

In biological cell manipulation, manual thrust or penetration of an injection pipette into an embryo cell is currently performed by a skilled operator, relying on visual feedback information only. Accurately measuring cellular forces is a requirement for minimally invasive cell injections. Moreover, the cellular force sensing is essential in investigating the biophysical properties for cell injury and membrane modeling studies. This paper presents cellular force measurements for the force feedback-based biomanipulation. Cellular force measurement system using piezoelectric polymer sensor is implemented to measure the penetration force of a zebrafish egg cell. First, measurement system setup and calibration are described. Second, the force feedback-based biomanipulation is experimentally carried out. Experimental results show that it successfully supplies real-time cellular force feedback to the operator at tens of uN and thus plays a main role in improving the reliability of biological cell injection tasks.

• International Journal of Control, Automation, and Systems
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• 제5권4호
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• pp.379-387
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• 2007

In this paper, a nonlinear anti-sway controller for container cranes with load hoisting is investigated. The considered container crane involves a planar motion in conjunction with a hoisting motion. The control inputs are two (trolley and hoisting forces), whereas the variables to be controlled are three (trolley position, hoisting rope length, and sway angle). A novel feedback linearization control law provides a simultaneous trolley-position regulation, sway suppression, and load hoisting control. The performance of the closed loop system is shown to be satisfactory in the presence of disturbances at the payload and rope length variations. The advantage of the proposed control law lies in the full incorporation of the nonlinear dynamics by partial feedback linearization. The uniform asymptotic stability of the closed-loop system is assured irrespective of variations of the rope length. Simulation and experimental results are compared and discussed.

• 대한기계학회논문집A
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• 제21권8호
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• pp.1188-1194
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• 1997

In this paper, we design output feedback nonlinear dynamic control law by using state feedback nonlinear dynamic compensator and PI observer and show that the controller can stabilize globally and asymptotically a class of nonlinear systems with mismatched uncertainties. We also show that it is possible for a nonlinear system to use the output of PI observer in place of state variables in case that the nonlinear dynamic control law is used, similarly as in the linear system. The effectiveness of the proposed control law is demonstrated by a numerical simulation.

• 대한기계학회논문집A
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• 제21권8호
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• pp.1184-1184
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• 1997

In this paper, we design output feedback nonlinear dynamic control law by using state feedback nonlinear dynamic compensator and PI observer and show that the controller can stabilized globally and asymptotically a class of nonlinear systems with mismatched uncertainties. We also show that it is possible for a nonlinear system to use the output of PI observer in place of state variables in case that the nonlinear dynamic control law is used, similarly as in the linear system. The effectiveness of the proposed control law is demonstrated by a numerical simulation.