• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.277-282
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• 2001

As human-friendly robot techniques improve, the concept of the wearability of robotic arms becomes important. A master arm that detects human arm motion and provides virtual forces to the operator is an embodied concept of a wearable robotic arm. In this study, we design a 7 DOF wearable robotic arm with high joint torques. An operator wearing this robotic arm can move around freely because this robotic arm was designed to have its fixed point at the shoulder part of the operator. The proposed robotic arm uses parallel mechanisms at the shoulder part and the wrist part on the model of the human muscular structure of an upper limb. To reduce the computational load in solving the forward kinematics and to prevent singularity motions of the parallel mechanism, yawing motion of the parallel mechanisms was separated using a slip ling mechanism. The total weight of the proposed robotic arm is about 4 kg. An experimental result of force tracking test for the pneumatic control system and an application example for VR robot are described to show the validity of the robot.

• 한국정밀공학회지
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• 제16권4호통권97호
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• pp.205-212
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• 1999

A three dimensional binary parallel robot manipulator uses actuators which have only two stable states and its structure is variable geometry truss. As a result, it has a finite number of states and fault tolerant mechanism because of kinematic redundancy. This kind of robot manipulator has some advantages compared to a traditional one. Feedback control is not required, task repeatability can be very high, and finite state actuators are generally inexpensive. Because the number of states of a binary robot manipulator grows exponentially with the number of actuators it is very difficult to solve and inverse kinematic problem. The goal of this paper is to develop an efficient algorithm to solve an inverse kinematic problem of three dimensional binary parallel robot manipulator using a backbone curve when the number of actuators are too much. We first derive the coordinate transformations associated with a three degree of freedom in-parallel actuated robot manipulator. The backbone curve is generated optimally by considering the maximum roll and pitch angles of the robot manipulator configuration and length of link. Then, the robot manipulator is fitted along the backbone curve with some criterion.

• 한국기계가공학회지
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• 제13권5호
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• pp.90-97
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• 2014

This paper presents a simplified dynamics model, dynamics simulations, and computed torque control experiments of the Delta high-speed parallel robot. Using the typical Newton-Euler method, a simplified but accurate dynamics model with practical assumptions is derived. Accuracy and fast calculations of the dynamics are essential in the computed torque control for high-speed applications. It was found that the simplified dynamics equation is in very god agreement with the ADAMS model, and the calculation time of the inverse kinematics and inverse dynamics is about 0.04 msec. From the dynamics simulations, the cycle trajectory along the y-axis requires less peak motor torque and a lower angular velocity and less power than that along the x-axis. The computed torque control scheme can reduce the position error by half as compared to a PD control scheme. Finally, the developed Delta parallel robot prototype, half the size of the ABB Flexpicker robot, can achieve a cycle time of 0.43 sec with a 1.0kg payload.

• 한국기계가공학회지
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• 제21권2호
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• pp.116-122
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• 2022

This study proposed a method of testing the stability when selecting gears to reduce the weight of a 3-DOF wrist mechanism for a pick-and-place 3-DOF parallel robot with an increased workspace by using an additional straight axis at its top. We performed SolidWorks^® modeling- and ANSYS^®-based structural analysis of a pinion gear, which is most vulnerable to the force from a 3-DOF wrist mechanism, to lighten the robot weight for performing various tasks. When the initial analysis results considerably differed from the theoretical values calculated in advance, we checked and identified the errors in the contact conditions or input values. Ultimately, it is believed that the methodology presented in this paper will help in mitigating errors during analysis and determine the accurate values for a lightweight 3-DOF wrist mechanism for a parallel robot with an expanded workspace.

• 로봇학회논문지
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• 제11권4호
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• pp.248-255
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• 2016

Machining error makes the uncertainty of dimensional accuracy of the kinematic structure of a parallel robot system, which makes the uncertainty of kinematic accuracy of the end-effector of the parallel robot system. In this paper, the tendency of trajectory tracking error caused by the tolerance of design parameters of the parallel robot is analyzed. For this purpose, all the position errors are analyzed as the manipulator is moved on the target trajectory. X, Y, Z components of the trajectory errors are analyzed respectively, as well as resultant errors, which give the designer of the manipulator the intuitive and deep understanding on the effects of each design parameter to the trajectory tracking errors caused by the uncertainty of dimensional accuracy. The research results shows which design parameters are critically sensitive to the trajectory tracking error and the tendency of the trajectory tracking error caused by them.

• 대한기계학회논문집A
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• 제20권1호
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• pp.35-43
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• 1996

A computer program for automatic deriving the symbolic equations of motion for robots using the programming language MATHEMATICA has been developed. The program, developed based on the Lagrange formalism, is applicable to the closed chain robots as well as the open chain robots. The closed chains are virtually cut open, and the kinematics and dynamics of the virtual open chain robot are analyzed. The constraints are applied to the virtually cut joints. As a result, the spatial closed chain robot can be considered as a tree structured open chain robot with kinematic constraints. The topology of tree structured open chain robot is described by a FATHER array. The FATHER array of a link indicates the link that is connected in the direction of base link. The constraints are represented by Lagrange multipliers. The parallel robot, DELTA, having three-dimensional closed chains is modeled and simulated to illustrate the approach.

• 로봇학회논문지
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• 제11권2호
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• pp.73-82
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• 2016

This paper focuses on the vibration analysis of planar cable-driven parallel robots on their configurations. Despite of many advantages of the cable robots, elasticity of the cables may cause the vibration at the existence of external disturbance, resulting in deterioration of positioning accuracy. According to the vibration theory, having high first order natural frequency can prevent resonance with low frequency disturbance from the surrounding environment. A series of simulations showed that choosing frame / end-effector shape and cable connection method affects robots' natural frequency. For the precise simulation, the cables are modeled as linear springs and axial vibration of cables is mainly considered. Aspect ratios of the frame and end-effector are defined as non-dimensional parameters while their areas are fixed. It was shown that vibration analysis guides to design a planar cable robot in terms of high capacity to reduce vibration.

• 대한기계학회논문집A
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• 제37권8호
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• pp.1043-1050
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• 2013

병렬로봇은 구조적 특성 때문에 정밀성 및 고강성이 요구되는 분야와 고속성이 요구되는 분야에서 주로 적용되고 있다. 물류 분야에서 고속이송의 중요성은 날이 갈수록 증가하고 있으며, 본 연구에서도 동일한 목적으로 고속 이송에 적용될 병렬로봇이 개발되었다. 개발된 로봇은 최대 3kg의 부하를 이송할 수 있으며 0.1kg의 부하조건에서의 최대 운전 조건은 싸이클 타임 0.3sec로 최대 속도 약 4.5m/sec로 운전할 수 있으며(Pick & Place 작업, Adept cycle) 이때 최대 가속도는 약 13G에 달한다. 본 논문에서는 개발된 고속 병렬로봇의 설계 및 해석에 관한 연구결과와 개발된 로봇의 성능에 관해 소개하고자 한다.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.200-209
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• 1999

This paper presents a precise tracking control scheme for the proposed parallel robot using artificial neural network. This control scheme is composed of three feedback controllers and one feedforward controller. Conventional PD controller and artificial neural network are used as feedback and feedforward controller respectively. A backpropagation learning strategy is applied to the training of artificial neural network, and PD controller outputs are used as target outputs. The PD controllers are designed at the robot dynamics based on inter-relationship between active joints and moving platform. Feedback controllers insure the total stability of system, and feedforward controller generates the control signal for trajectory tracking. The precise tracking performance of proposed control scheme is proved by computer simulation.

• 한국기계연구소 소보
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• 통권19호
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• pp.81-92
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• 1989

This paper presents a simple identification method of the actual kinematic parameters for the robot with parallel joints. It is known that Denavit-Hartenberg's coordinate system is not useful for nearly parallel joints. In this paper, the coordinate frames are reassigned to model the kinematic parameter between nearly parallel joints by four parameters. The proposed identification method uses a straight ruler about 1m long. A robot hand is placed by using a teaching pendant at the prescribed points on the ruler, and corresponding error function is defined. The identified kinematic parameters which make the error function zero are obtained by iterative least square error method based on the singular value decomposition. In the compensation of joint angles, only the position is considered because the usual applications of robot do not require a precise orientation control.