• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1651-1656
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• 2005

This paper describes a natural frequency analysis conducted to find out a suitable working area for a spring-manipulator system generating a large vibrating force with mechanical resonance. Large force generation is one of the functions that we hope for a robot. For example, a weeding robot is required to generate a large force, because some weeds have roots spreading deeply and tightly. The spring-manipulator system has a spring element as an end-effector, so it can be in a state of resonance with the elasticity of the spring element and the inertial characteristics of the manipulator. A force generation method utilizing the mechanical resonance has potential to produce a large force that cannot be realized by a static method. A method for calculating a natural frequency of a spring-manipulator system with the generalized inertia tensor is proposed. Then the suitable working area for the spring-manipulator system is identified based on a natural frequency analysis. If a spring-manipulator system operates in the suitable working area, it can sustain mechanical resonance and generate a large vibrating force. Moreover, it is shown that adding a mass at the tip of the manipulator expands the suitable working area.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권2호
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• pp.74-80
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• 2000

In this paper, we present a control method of mobile power assist systems. Most of mobile power assist systems have a heavy base for preventing easy tumbling, so continual movement of the base during operations causes high energy consumption and gives the high risk of human injury. Furthermore, the slow dynamics of the base limits the frequency bandwidth of the whole system. Thus we propose a cooperation control method of the mobile base and manipulator, which removes the unnecessary movements of the base. In our scheme, the mobile base does not move until the center of gravity(C.G) of the system goes outside a safety region. When C.G. reaches the boundary of the safety region, the base starts moving to recover the manipulator's initial configuration. By varying the parameters of a human impedance controller, the operator is warned by a force feedback that C.G. is on the marginal safety region. Our scheme is implemented by assigning a nonlinear mass-damper-spring impedance to the tip of the manipulator. Our scheme is implemented by a nonlinear mass-spring impedance to the tip of the manipulator. The experimental results show the efficacy of the proposed control method.

• 대한기계학회논문집A
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• 제24권2호
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• pp.481-488
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• 2000

This paper presents a new passive gravity -compensating system for articulated robot manipulators. The system, which consists of linear zero- free -length springs, achieves exact counterbalancing o f the gravitational loads throughout the entire range of the manipulator workspace, A basic concept is to design springs such that the total potential energy of the system including the manipulator and the springs should be maintained constant. A prototype has been developed for a direct-drive five-bar manipulator and its performances have been investigated. Results show that the gravity-induced motor torques have been reduced to less than 5% of those of uncompensated robots. Also, the gravity-compensating system simplifies the position control algorithm while maintaining the trajectory-tracking errors in a satisfactory level. In conclusion, the proposed system efficiently improves the manipulator performances by reducing the driving motor size and the energy consumption as well as by simplifying the control systems.

• 대한기계학회논문집A
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• 제36권11호
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• pp.1405-1411
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• 2012

위험지역에서의 작업을 위하여 전세계적으로 원격조작기가 널리 활용되고 있다. 특히 원격 시스템의 경우, 운영되는 환경의 특징상 안정적인 성능이 담보되어야만 하며, 조작기 몸체의 경량화 및 운용환경 외부에서의 유지보수 편리성을 위하여 구동부를 시스템의 기저부에 집중시킬 수 있는 장력구동방식 메커니즘이 주로 활용되고 있다. 본 연구에서는 장력구동 방식 원격조작기에 적용하기 위한 그리퍼 탄성 구동부의 설계를 위해 시도된 접근법을 소개하고자 한다. 제시된 그리퍼 시스템은 기본적으로 스프링 메커니즘에 기반을 둔 4 절 링크형 구조를 가지고 있으며 마스터 조작자에 의해 동작되는 슬레이브 조작기의 말단부에 결합되는 구조를 가진다. 본 논문에서는 이러한 조작기의 요구사항에 맞는 그리퍼의 파지력 및 복원력을 재현하기 위하여 그리퍼 상에서의 적정 스프링 결합위치 및 요구강성과 그에 따른 운동학적 영향계수 등을 분석 및 고찰하였다. 최종적으로는 이러한 분석내용들을 바탕으로, 실제 그리퍼 시스템에 적용함으로써 타당성을 검증하였다.

• 한국정밀공학회지
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• 제21권11호
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• pp.83-90
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• 2004

In this paper we present a new real-time visual servoing unit for laparoscopic surgery This unit can automatically control laparoscope manipulator through visual tracking of laparoscopic surgical tool. For the tracking, we present two-stage adaptive CONDENSATION(conditional density propagation) algorithm to extract the accurate position of the surgical tool tip from a surgical image sequence in real-time. This algorithm can be adaptable to abrupt change of laparoscope illumination. For the control, we present virtual damper system to control a laparoscope manipulator safely and stably. This system causes the laparoscope to move under constraint of the virtual dampers which are linked to the four sides of image. The visual servoing unit operates the manipulator in real-time with locating the surgical tool in the center of image. The experimental results show that the proposed visual tracking algorithm is highly robust and the controlled manipulator can present stable view with safe.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.145-148
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• 1990

In this paper, the problem of designing a feedback controller for a robotic manipulator, which is activated by a D.C. motor through a gear train and a flexible shaft or chain, is considered. When the response of the closed loop control system is relatively slow, a satisfactory controller may be designed as a PID controller. As the speed of the control system increases, however, the spring effect of the linkage becomes profound, and as a result, the transient response exhibits a substantial oscillation. To eliminate this oscillation, it is necessary to design the controller based on at least a fourth order system model. This, in turn, requires the feedback of the entire state variables. In practice, however, only the position of the manipulator and the velocity of the motor are readily measurable. The state variable reconstruction method or a state observer cannot be used because of the system nonlinearities such as the Coulomb frictions. In this study, an alternative controller, which is based on delayed feedback of the output variable only, is proposed, and a successful delayed feedback controller is designed and implemented on an actual experimental manipulator.

• 제어로봇시스템학회논문지
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• 제22권9호
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• pp.733-737
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• 2016

In this paper, we propose a mechanism that can compensate for gravity in a robot manipulator. Industry robots generate torque due to carrying heavy weight. For this reason, the robots need high specification motors, which increases the prices of the robots and their production costs. In order to resolve these problems, a mechanism for gravity compensation has been developed using a spring and wire system. But this system has problems related to wire stretching. A winding mechanism is therefore used to supplement this drawback of the wire. The robot used was developed by the 1-DOF system. Analysis was performed for the performance of the mechanism. Experiments were conducted to compare simulation results and experimental results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.149-154
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• 1990

In this paper, simulation results of a robust digital tracking controller on a robotic manipulator are presented. The objective is to follow a ramp reference input with zero steady state error in the presence of a disturbance and system parameter variations. Some of the difficulties are caused by the Coulomb frictions, the disturbance due to the gravitational pull, the spring effect of a link between the drive motor and the manipulator arm. Another difficulty is that, because of the non-differentiable Coulomb friction, the digital control system cannot be represented as a discrete system. It is thus necessary to design the controller based on a discrete-continuous hybrid model. The controller is based on feeding back the state variables and augmenting the system by addition discrete integrators. The feedback gain parameters are obtained by applying the quadratic optimal control theory and then choosing the new weighting matrices to eliminate the limit cycle by using the describing function method for hybrid system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.957-962
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• 2007

This paper describes a new mechanism for improving the force of actuators based on shape memory alloys (SMA) by increasing the number at which a coil pattern SMA spring can evenly be heated. This structure accomplishes a high efficient transformation between force and displacement overcoming the main mechanical drawback of shape memory alloys, that being the limit strain. A pantograph manipulator actuated by the introduced new mechanism has been designed for this research. Mechanical structure and driving mechanism of this manipulator are described in detail, and its control algorithm and current amplifier circuit in a position control system are designed.

• 전력전자학회논문지
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• 제4권6호
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• pp.608-615
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• 1999

본 논문에서는 초음파 모터의 위상차 구동원리에 관해서 명확히 하였고, 이를 이용하여 점·탄성 특성을 갖는 컴플라이언스 제어를 제시하였다. 제안된 컴플라이언스 제어는 인간의 근골격 시스템으로부터 유출하여 인간의 운동특성과 같이 매니퓰레이터의 관절 토크를 점성과 탄성계수의 조절에 의해 매니퓰레이터의 위치와 자세가 제어되도록 하였다. 초음파 모터의 위상차 구동원리에 대한 타당성을 모의실험을 통해 검증하였으며, 제시된 제어방법의 타당성을 검증하기 위하여 초음파모터를 이용하여 2축 수평형 직접구동 매니퓰레이터를 제작하여 점성과 탄성 특성에 대한 실험을 하였다.