• 대한기계학회논문집A
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• 제26권12호
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• pp.2687-2694
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• 2002

A precision displacement measuring system is proposed, which can detect the 3-DOF translational motions of precision positioning devices. The optical system, which is composed of two diode-laser sources and two quadratic PSDs, is adapted to detect the position of the spherical reflector usually mounted on the platform of positioning devices. Each of the laser beams from diode-laser sources is reflected at the highly reflective surface of the sphere; hence, the 3-dimensional position of the sphere causes the directional change of the reflected beams, which is detected by the PSDs. In this paper, we define the relationships between the output values of the two PSDs and the 3-DOF translational motions of the sphere. Based on a deduced measurement model, we perform measurement simulation and evaluate the performance of the proposed measurement system: linearity, sensitivity, measuring range, and measurement error. The results show that the proposed measuring method is very useful for the measurement of the precision displacement of 3-DOF micro motions.

• Journal of Biosystems Engineering
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• 제25권2호
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• pp.141-150
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• 2000

This study was carried out to de develop a control strategy of a fruit harvesting redundant robot. The method of generating a safe trajectory, which avoids collisions with obstracles such as branches or immature fruits, in the 3D(3-dimension) space using artificial potential field technique and virtual plane concept was proposed. Also, the method of setting reference velocity vectors to follow the trajectory and to avoid obstacles in the 3D space was proposed. Developed methods were verified with computer simulations and with actual robot tests. Fro the actual robot tests, a machine vision system was used for detecting fruits and obstacles, Results showed that developed control method could reduce the occurrences of the robot manipulator located in the possible collision distance. with 10 virtual obstacles generated randomly in the 3 D space, maximum rates of the occurrences of the robot manipulator located in the possible collision distance, 0.03 m, from the obstacles were 8 % with 5 degree of freedom (DOF), 8 % with 6-DOF, and 4% with 7-DOF, respectively.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.299-303
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• 2004

In our pervious paper, a new parallel-type spherical 3-degree-of-freedom mechanism consisting of a two-degree-of-freedom parallel module and a serial RRR subchain was proposed[1]. In this paper, its improved version is suggested and implemented. Differently from the previous 3-dof spherical mechanism, gear chains are incorporated into the current version of the mechanism to drive the distal revolute joint of the serial subchain from the base of the mechanism and in fact, the modification significantly improves kinematic characteristics of the mechanism within its workspace. Firstly, after a brief description on its structure, the closed-form solutions of both the forward and the reverse position analysis are derived. Secondly, the first-order kinematic model of the mechanism for the inputs which are assumed to be located at the base is derived. Thirdly, through the simulations of the kinematic analysis via. kinematic isotropic index, it is confirmed that the mechanism has much more improved isotropic properties throughout the workspace of the mechanism than the previous mechanism in [1]. Lastly, the proposed mechanism is implemented to verify the results from this analysis.

• 제어로봇시스템학회논문지
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• 제3권4호
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• pp.422-434
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• 1997

In this paper, a two-stage kinematic optimal design for a 3 degree of-freedom (DOF) excavator subsystem, which consists of boom, arm and bucket, is performed. The objective of the first stage is to find the optimal parameters of the joint-actuating mechanisms which maximize the force-torque transmission ratio between the hydraulic actuator and the rotating joint. The objective of the second stage is to find the optimal link parameters which maximize the isotropic characteristic of the excavator subsystem throughout the workspace. It is illustrated that kinematic/dynamic performances of the kinematically optimized excavator subsystem have improved compared to those of original HE280 excavator, with respect to three performance indices such as maximum load handling capacity, maximum velocity capability, and acceleration capability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.65-67
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• 2007

In this paper describes the design and characteristic analysis of a novel 2-DOF(Degree of Freedom) motor. For multi DOF actuating, several numbers of motors have been used. But the using of normal motors they connected each other in single joint, have necessary to a several type of complex power transmission devices. The 2-DOF motor can drive pan, tilt motion in only one unit and it is not necessary to use additional gears and links parts. Therefore by the using of 2-DOF spherical motor ran eliminate; combined effects of inertia, backlash, non-linear friction, and elastic deformation of gears. The validity of the analysis is confirmed by 3D finite element method.

• 대한기계학회논문집A
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• 제22권3호
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• pp.504-518
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• 1998

Degree-Of-Freedom(DOF) for most power transmission system varies according to the operation status which consists of friction elements to change the power flow or to adjust the speed ratio such as clutches, brakes or one-way clutches. To simulate the dynamic characteristics of automatic power transmission system which is a typical example of such a variable DOF systems, many sets of governing equations and complicated phase decision routines are necessary. In this paper dynamic constraint theorem is derived explaining the torque transmission characteristics during the clutch engagement process and a robust stable algorithm is developed describing this phase transition phenomenon effectively by introducing the concept of direct torque and virtual damping. Finally, applying this algorithm to a passenger car automatic transmission gear consisting of several friction elements, an efficient simulation methods for such a complex system will be suggested that is very simple and systematic.

• 대한조선학회논문집
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• 제48권3호
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• pp.267-274
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• 2011

This paper presents the results of prediction of maneuverability of KCS about 4 degree of freedom(DOF) including roll motion. The prediction is carried out by CPMC captive model test. The CPMC(Computerized Planar Motion Carriage) with captive model test equipment including roll moment gage is installed at Ocean Engineering Tank of MOERI. KCS is the container ship open to the world by MOERI. To predict the 4 DOF maneuverability of a ship some tests with roll angle are conducted. And the prediction results of maneuverability by simulation are compared with the results of free running model test. The simulation results agree well with those of free running model tests.

• 한국지능시스템학회논문지
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• 제22권3호
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• pp.267-272
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• 2012

본 논문에서는 6 방향 자유도를 지닌 능동 자기베어링 시스템의 강인 디지털 퍼지 제어에 대한 내용을 다루고자 한다. 6방향 자유도에 대한 기본 모델은 회전자 구조와 원뿔형의 능동 자기베어링 시스템의 자기력 간의 상관관계에 의해 결정된다. 구성된 모델은 비선형 동적방정식으로 구성되기 때문에, 제어 목적을 달성하기 위한 제어 입력 신호의 설계가 어려우며, 외부 환경의 영향에 따른 시스템 파라미터 변화율에도 많이 민감한 편이다. 이를 보완하기 위하여, 획득한 동적방정식을 기반으로 TS 퍼지 모델에 기반 한 디지털 제어 목적에 적합한 구조로의 변환이 이루어진다. 여기서 말하는 제어 목적이란, 회전자의 회전을 외부의 물리적 접촉 없이 자기장의 힘만으로 동작하도록 베어링의 위치를 최대한 센터에 위치케 하는 것을 말한다. 본 논문에서는 6자유도를 지닌 능동 자기베어링 시스템의 비선형성에 대한 해석 방안으로 퍼지 모델링을 통해 시스템을 재해석하게 되며, 외부 파라미터 변화에 따른 대응을 위하여 강인 제어기 설계를 목적으로 한다. 제안된 강인 제어 알고리즘은 시뮬레이션 과정을 통해 검증된다.

• Wind and Structures
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• 제7권3호
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• pp.187-202
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• 2004

Wind tunnel experiments are often performed for the identification of aeroelastic parameters known as flutter derivatives that are necessary for the prediction of flutter instability for flexible structures. Experimental determination of all the eighteen flutter derivatives for a section model facilitates complete understanding of the physical mechanism of flutter. However, work in the field of identifying all the eighteen flutter derivatives using section models with all three degree-of-freedom (DOF) has been limited. In the current paper, all eighteen flutter derivatives for a streamlined bridge deck and an airfoil section model were identified by using a new system identification technique, namely, Iterative Least Squares (ILS) approach. Flutter derivatives of the current bridge and the Tsurumi bridge are compared. Flutter derivatives related to the lateral DOF have been emphasized. Pseudo-steady theory for predicting some of the flutter derivatives is verified by comparing with experimental data. The three-DOF suspension system and the electromagnetic system for providing the initial conditions for free-vibration of the section model are also discussed.

• Smart Structures and Systems
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• 제3권1호
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• pp.115-131
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• 2007

The electromechanical integrated toroidal drive is a new drive system. For the control of the drive, the torque fluctuation and the steady-state errors should be removed and the fast response to the input change should be achieved. In this paper, the torque fluctuation of the drive system is analyzed and expressed as Fourier series forms. The transfer function of the torque control for the drive system is derived from its electromechanical coupled dynamic equations. A 2-DOF control method is used to control the drive system. Using definite parameter relationship of the 2-DOF control system, the steady errors of the torque control for the drive system is removed. Influences of the drive parameters on the control system are investigated. Using proper drive parameters, the response time of the control system is reduced and the quick torque response of the drive system is realized. Using a compensated input voltage, the torque fluctuation of the drive system is removed as well. The compensated input voltage can be obtained from the torque fluctuation equation and the transfer function. These research results are useful for designing control system of the new drive.