• Journal of Mechanical Science and Technology
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• 제19권3호
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• pp.756-767
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• 2005

This paper presents a decentralized motion control method of welding mobile manipulators which use for welding in many industrial fields. Major requirements of welding robots are accuracy, robust, and reliability so that they can substitute for the welders in hazardous and worse environment. To do this, the manipulator has to take the torch tracking along a welding trajectory with a constant velocity and a constant heading angle, and the mobile-platform has to move to avoid the singularities of the manipulator. In this paper, we develop a kinematic model of the mobile-platform and the manipulator as two separate subsystems. With the idea that the manipulator can avoid the singularities by keeping its initial configuration in the welding process, the redundancy problem of system is solved by introducing the platform mobility to realize this idea. Two controllers for the mobile-platform and the manipulator were designed, respectively, and the relationships between two controllers are the velocities of two subsystems. Control laws are obtained based on the Lyapunov function to ensure the asymptotical stability of the system. The simulation and experimental results show the effectiveness of the proposed controllers.

• Tribology and Lubricants
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• 제28권6호
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• pp.328-332
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• 2012

Generated Axial Force (GAF) due to internal friction at Constant Velocity (CV) joints is one of the causes generating vibration problems such as shudder in vehicle. In this study, the GAF measuring tester is developed to precisely measure GAF caused by internal friction in CV joints. As the developed tester can control temperature at joint, driving torque, angle of rotation and joint angles, actual driving conditions such as sudden acceleration can be applied to the machine. GAFs are measured and compared by using different types of grease in tripod housing. Also GAFs are measured for both new and used CV joints to be compared and analyzed. The test result shows the repeatability and consistency of the tester in terms of the different test conditions. By using the developed CV joint tester, friction performance of the joint can be evaluated by proposing the best CV joints as well as greases generating the lowest GAF.

• 한국멀티미디어학회논문지
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• 제3권3호
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• pp.224-233
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• 2000

본 논문은 인간과 VR환경과의 상호작용을 지원하는 중요한 요소 중 하나인 이동의 문제점 및 해 결 방법에 대하여 연구하였다. 이 논문에서 제시된 Intelligent Cruise-Control Navigation (ICCN)은 다중 사용자 환경의 가상공간을 이동할 때, 실세계와 유사한 이동방법을 제공하여 사용자로 하여금 가상공간에 대한 현장감 및 현실감의 제고에 초점을 두었다. ICCN은 사용자들이 가상공간에서 이동시 부가적인 입력이 없이도 일정한 속도로 이동을 지원하는 Constant Velocity Navigation, 이동 중 장애물 및 다른 사용자(아바타)와의 충돌현상을 감지 및 회피하는 Collision Detection and Avoidance, 그리고 충돌회피후 기존 방향으로의 계속된 이동을 지원하는 Path Adjustment등의 기능을 제공한다. ICCN은 사용자의 부가적인 노력의 감소 및 병행작업을 보장, 현실과 유사한 사용자 중심의 navigation 기 법 을 제공, 가상공간과 현실과의 괴리를 줄임으로써 가상현실이 추구하는 현실감 및 현장감을 높일 수 있도록 하였다. 실험을 통하여 본 연구에서 제안한 ICCN이 사용자중심의 매우 자연스럽고, 쉽고 편리한 가상공간 navigation 인터페이스라는 평가를 얻었다.

• 제어로봇시스템학회논문지
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• 제12권10호
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• pp.1029-1034
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• 2006

In this paper, the tracking control of an automatic pipe cutting robot, called APCROM, with a magnetic binder is studied. Using magnetic force APCROM, a wheeled robot, binds itself to the pipe and executes unmanned cutting process. The gravity effect on the movement of APCROM varies as it rotates around the pipe laid in the gravitational field. In addition to the varying gravity effect other types of nonlinear disturbances including backlash in the driving system and the slip between the wheels of APCROM and the pipe also cause degradation in the cutting process. To maintain a constant velocity and consistent cutting performance, the authors adopt a repetitive learning controller (MRLC), which learns the required effort to cancel the tracking errors. An angular-position estimation method based on the MEMS-type accelerometer is also used in conjunction with MRLC to compensate the tracking error caused by slip at the wheels. Experimental results verify the effectiveness of the proposed control scheme.

• 한국군사과학기술학회지
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• 제8권3호
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• pp.92-100
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• 2005

The objective of this paper is to design a sliding mode controller of an electro-mechanical fin actuation system using extended reducer-observer(ERO) which is used in order to estimate the velocity. The employed observer enables proper estimation of the plant state variables, even in the case of the constant or slow varying load torque disturbances. The effectiveness of this control scheme is verified by comparison with a PID control through a series of simulation studies. The simulation results show that the sliding mode control designed with the ERO gives good control performances.

• 전력전자학회논문지
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• 제6권2호
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• pp.202-208
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• 2001

스위치드 리럭턴스 모터(Switched Relutance Motor : 이하 SRM)는 이중 돌극형으로 되어있으며, 상권선은 고정자만 사용한다. 다른 어느 전동기보다도 간단한 구조를 가지고 있어 제작단가가 저렴하고, 기계적으로 견고하며, 고온 등의 열악한 환경에서도 신뢰성이 높으며, 브러쉬 등이 없어 유지비가 거의 들지 않는 장점을 지니고 있다. 그러나 SRM은 상여자를 위하여 회전자의 위치정보를 알아야하므로 위치 검출기가 필요하고, 정속도 운전을 위하여 타코 발전기나 엔코더가 부가적으로 필요하다. 그러나 본 논문에서는 회전자의 속도측정을 얻기 위하여 고가의 엔코더를 사용하지 않고, 단지 간단한 슬롯 디스크로부터 위치를 검출하여 속도를 추정할 수 있는 알고리즘을 제시하고 개발하였다. 속도 추정 알고리즘을 적용한 가변속 디지털 제어시스템을 구현하기 위하여 TI사의 TMS320F240-20MIPS 고정 소수점 연산용 프로세서를 사용하였다. 개발한 시스템을 실험한 결과 넓은 범위에 걸쳐 속도제어가 가능하였고, 단일 펄스모드, 하드 쵸핑모드 및 소프트 쵸핑모드 뿐만 아니라, 전류제어 동작모드에서 가변속 제어가 가능하였다. 그리고 어드밴스각 제어가 가능하였다.

• 대한의용생체공학회:의공학회지
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• 제24권5호
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• pp.435-442
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• 2003

In this paper, biomechanical aspects of dynamic대학교postural responses against forward perturbations were experimentally determined simultaneous measurements of joint angles, accelerations. EMG activations, center of pressure(CoP) movements and ground reaction forces(GRF), Thirteen young healthy volunteers, stood on a flat platform, were translated into the forward direction by an AC servo-motor at two separate velocities(0.1m and 0.2m/s). In order to recover postural balance against the forward perturbation, joint motions were observed in the sequence of the ankle dorsiflexion, the knee flexion and then the hip flexion during the later acceleration phase. Both acceleration patterns at the heel and the sacrum were shown the forward acceleration pattern during the later acceleration phase and early of constant velocity phase as increasing platform velocity, respectively. Tibialis anterior(TA) for the ankle dorsiflexion and biceps femoris(BF) for the knee flexion. the primary muscle to recover the forward perturbation, was activated during the half of acceleration phase. Ankle strategy was used for slow-velocity perturbation, but mixed strategy of both ankle and hip used for the fast-velocity perturbation. In addition, parameters of perturbation such as timing and magnitude influenced the postural response against the perturbation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.292-294
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• 2001

자가용 발전기는 주로 디젤엔진과 동기발 전기로 구성된다. 자가용 발전기의 안정적인 출력을 위해서는 디젤엔진을 정속으로 운전하는 것이 중요하다. 디젤엔진의 속도 제어기로는 일반적으로 조속기가 사용되는데, 본 논문에서는 DSP를 이용한 디지털 조속기를 개발하고 정속제어를 위한 운전 알고리즘을 제시하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1418-1423
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• 2003

In this paper, a nonlinear controller based on sliding mode control is applied to a two -wheeled Welding Mobile Robot (WMR) to track a smooth-curved welding path at a constant velocity of the welding point. T he mobile robot is considered in terms of dynamics model in Cartesian coordinates and its parameters are exactly known . To obtain the controller, the tracking errors are defined, and the two sliding surfaces are chosen to guarantee that the errors converge to zero asymptotically. Two cases are to be considered: fixed torch and controllable torch. In addition, a simple way of measuring the errors is introduced using two potentiometers. The simulation results are included to illustrate the performance of the control law.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 추계학술대회 논문집
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• pp.301-305
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• 2001

Conventionally, robot control algorithms are divided into two stages, namely, path or trajectory planning and path tracking(or path control). This division has been adopted mainly as a means of alleviating difficulties in dealing with complex, complex, coupled manipulator dynamics. The minimum-time manipulator control problem is solved for the case when the path is specified and the actuator torque limitations are known. In path planning, DP is applied to applied to find the shortest path form initial position to final position with the assumptions that there is no obstacle and that each path is straight line. In path control, the phase plane technique is applied to the minimum-time control with the assumptions that the bound on each actuator torque is a function of joint position and velocity or constant. This algorithm can be used for any manipulator that has rigid link, known dynamics equations of motion, and joint angles that can be determined at a given position on the path.