• 대한전기학회논문지:시스템및제어부문D
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• 제53권3호
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• pp.173-181
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• 2004

In normal robot control systems without any actuator failures, it is assumed that actuator torque coefficients applied at each joint have normally 1's all the time. However, it is more practical that actuator torque coefficients applied at each joint are nonlinear time-varying. In other words, it has to be considered that actuators equipped at joints may fail due to hardware or software faults. In this work, actuator torque coefficients are assumed to have non-zero values at all joints. In the case of an actuator torque coefficient which has a zero value at a joint, it means the complete loss of torque on the joint. This paper doesn't deal with the case. As factors of performance degradation of robots, both actuator failures and uncertainties are considered in this paper at the same time. This paper proposes a robust adaptive fault-tolerant control scheme to maintain the required performance and achieve task completion for robot manipulators with performance degradation due to actuator failures and uncertainties. Simulation results are shown to verify the fault tolerance and robustness of the Proposed control scheme.

• 로봇학회논문지
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• 제9권4호
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• pp.264-271
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• 2014

In this study, we have developed the humanoid joint modules which provide a variety of service while living with people in the future home life. The most important requirement is ensuring the safety for humans of the robot system for collaboration with people and providing physical service in dynamic changing environment. Therefore we should construct the mechanism and control system that each joint of the robot should response sensitively and rapidly to fulfill that. In this study, we have analyzed the characteristic of the joint which based on the target constituting the humanoid motion, developed the optimal actuator system which can be controlled based on each joint characteristic, and developed the control system which can control an multi-joint system at a high speed. In particular, in the design of the joint, we have defined back-drivability at the safety perspective and developed an actuator unit to maximize. Therefore we establish a foundation element technology for future commercialization of intelligent service robots.

• 로봇학회논문지
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• 제2권2호
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• pp.168-177
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• 2007

In a number of fields, robots are being used for two purposes: efficiency and safety. Most robots, however, have single-actuator mechanism for each joint, where the tasks are performed with high stiffness. High stiffness causes undesired problems to the environment and robots. This study proposes redundant actuator mechanism as an alternative idea to cope with these problems. In this paper, Double-Actuator Unit (DAU) is implemented at each joint for applications of multi-link manipulators. The DAU is composed of two motors: the positioning actuator and the stiffness modulator, which enables independent control of positioning and compliance. A three-link manipulator with DAUs enables adaptive control of RCC. By modulating the joint stiffness of the manipulator and controlling the position of RCC, we can significantly reduce contact force during assembly tasks and surgical procedures.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.847-848
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• 2013

• 대한기계학회논문집 C: 기술과 교육
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• 제1권2호
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• pp.153-165
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• 2013

기존의 보행분석 연구들은 하지를 하나의 스프링으로 간주하였다. 만약 슬관절 신전을 보조할 수 있는 슬관절 액추에이팅 메커니즘을 개발할 수 있다면 보행에 필요한 탄성-변형률에너지를 혁신적으로 저장-방출할 수 있고, 그 결과 보행 중 하지강성은 더욱 증가할 것이다. 게다가 족관절 액추에이팅 메커니즘까지 추가되어 있다면 슬관절 액추에이터에 의한 과도한 인공하지강성을 능동적이고 적절한 수준으로 보상해주는 기전으로 작동할 것이다. 만약 가속도에 의한 보행속도 증가를 방지하기 위해 인위적 감속통제를 작동시킨다면 불필요한 운동에너지의 방출이 발생되고 하지강성 액추에이터의 실효성은 의심을 받게 된다. 따라서 본 저자는 보행속도를 2개의 세그먼트에 의한 상대 각속도 조절기법을 이용하여 하지강성을 증가시킨다는 기본개념으로 슬-족관절 액추에이터 시스템을 개발하였다. 또한 족관절에 슬관절 액추에이팅에 대한 보상기전이 존재하는 경우, 족관절의 보상기전이 중족지절관절 경사각 및 보행속도 변화에 미치는 상호영향을 연구하였다.

• 제어로봇시스템학회논문지
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• 제9권10호
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• pp.755-767
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• 2003

This paper proposes a robust fault-tolerant control framework for robot manipulators to maintain the required performance and achieve task completion in the presence of both partial joint failures and complete joint failures and uncertainties. In the case of a complete joint failure or free-swinging joint failure causing the complete loss of torque on a joint, a fully-actuated robot manipulator can be viewed as an underactuated robot manipulator. To detect and identify a complete actuator failure, an on-line fault detection operation is also presented. The proposed fault-tolerant control system contains a robust adaptive controller overcoming partial joint failures based on robust adaptive control methodology, an on-line fault detector detecting and identifying complete joint failures, and a robust adaptive controller overcoming partial and complete joint failures, and so eventually it can face and overcome joint failures and uncertainties. Numerical simulations are conducted to validate the proposed robust fault-tolerant control scheme.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1455-1458
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• 1996

In this paper trajectory tracking control problems are described for a robot manipulator by using pneumatic actuator. Under the assumption that the so-called independent joint control is applied to the control system, the dynamic model for each link is identified as a linear second-order system with input time-delay by the step response. Then, an optimal servo controller is designed by taking account of such a time-delay. The effectiveness of the proposed control method is illustrated through some simulations and experiments for the robot manipulator.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.315-316
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• 2012

• 한국지능시스템학회논문지
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• 제23권1호
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• pp.46-50
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• 2013

본 논문은 다수의 구동기 고장을 가진 유연 관절 로봇의 적응 고장 수용 제어기를 제안한다. 다수의 구동기 고장의 크기와 일어나는 시간은 알려지지 않는다고 가정한다. 구동기 고장을 수용하기 위해 추종 오차의 수렴율과 오버슈트의 최대치로 특성화된 미리 정의된 성능을 보장하는 유계 조건을 갖는 적응 고장 수용 제어기를 설계한다. 르아프노브 안정도 이론을 이용하여 페루트 시스템의 모든 신호가 준 전역적이고 균일하고 궁극적으로 유계됨을 증명하고 추종 오차가 미리 정의된 성능 유계에서 벗어나지 않음을 보인다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1679-1683
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• 2005

This paper suggests the new type of a joint torque sensor which is attached at each joint of a manipulator for making compliance. Previous six axis force/torque sensors are high cost and installed end-effector of the manipulator. However, torque on links of previous an end-effector cannot be measured. We design a joint torque sensor that can be fully integrated with an actuator in order to measure applying torque of the manipulator. The sensor system is designed through the structural analysis. The proposed joint torque sensors are installed to the 6 DOF manipulator of a mobile robot for hazardous works and we implemented experiments of measuring applied torque to the manipulator. By the experiment, we proved that the proposed low-cost joint torque sensor gives acceptable performance when we control a manipulator.