• Journal of Advanced Marine Engineering and Technology
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• 제35권5호
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• pp.632-639
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• 2011

해양 파력 발전 시스템의 설계를 위하여 본 연구에서는 6-자유도운동해석 기법을 적용한 3차원 CFD 해석으로 두 개의 부유체에 대한 거동을 유입되는 파의 성질에 따라 해석하였다. 수조모델내에서의 파의 생성형상을 현재 실험에서 가장 많이 사용되는 피스톤 형식의 조파기와 동일한 형태의 파를 생성하였으나 얕은 수심으로 인하여 바닥면에서 생성되는 에크만 경계층에 의해 파의 에너지가 감쇄되는 현상을 보였다. 생성된 파를 이용하여 파장에 따른 부유체의 거동을 계산한 결과 파장이 5m인 경우 부유체의 최대 진폭은 0.3m, 파장 1m인 경우 최소 진폭은 0.15m 그리고 파장 6m인 경우 부유체간 최대 거리는 1.06m로 계산되었다.

• International Journal of Aeronautical and Space Sciences
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• 제14권2호
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• pp.152-161
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• 2013

This paper presents a control effectiveness analysis of the hawkmoth Manduca sexta. A multibody dynamic model of the insect that considers the time-varying inertia of two flapping wings is established, based on measurement data from the real hawkmoth. A six-degree-of-freedom (6-DOF) multibody flight dynamics simulation environment is used to analyze the effectiveness of the control variables defined in a wing kinematics function. The aerodynamics from complex wing flapping motions is estimated by a blade element approach, including translational and rotational force coefficients derived from relevant experimental studies. Control characteristics of flight dynamics with respect to the changes of three angular degrees of freedom (stroke positional, feathering, and deviation angle) of the wing kinematics are investigated. Results show that the symmetric (asymmetric) wing kinematics change of each wing only affects the longitudinal (lateral) flight forces and moments, which implies that the longitudinal and lateral flight controls are decoupled. However, there are coupling effects within each plane of motion. In the longitudinal plane, pitch and forward/backward motion controls are coupled; in the lateral plane, roll and side-translation motion controls are coupled.

• Journal of Mechanical Science and Technology
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• 제16권1호
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• pp.13-23
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• 2002

This paper presents inverse kinematic and dynamic analyses of HexaSlide type six degree-of-freedom parallel manipulators. The HexaSlide type parallel manipulators (HSM) can be characterized as an architecture with constant link lengths that are attached to moving sliders on the ground and to a mobile platform. In the inverse kinematic analyses, the slider and link motion (position, velocity, and acceleration) is computed given the desired mobile platform motion. Based on the inverse kinematic analysis, in order to compute the required actuator forces given the desired platform motion, inverse dynamic equations of motion of a parallel manipulator is derived by the Newton-Euler approach. In this derivation, the joint friction as well as all link inertia are included. Relative importance of the link inertia and joint frictions on the computed torque is investigated by computer simulations. It is expected that the inverse kinematic and dynamic equations can be used in the computed torque control and model-based adaptive control strategies.

• 한국소음진동공학회논문집
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• 제18권9호
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• pp.905-912
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• 2008

Notion sickness is well known to be caused by long time exposure to the very low frequency motion in the multiple axes of human body Since the vestibular system for the perception of low frequency motion is located in the head, accurate measurement of 6 degree of freedom head motion is of great importance. In this study, the measurement system consisting of a safety helmet and 9 translational accelerometers was constructed for the estimation of 3 translational and 3 rotational motions of human head. Since estimation errors of 3 rotational components can be significantly magnified even by small offset of the sensitivity axis from the geometric center of an accelerometer, accurate measurement of sensitivity axis must be preceded. The method for accurate estimation of the offset was proposed, and the effect of offset on the estimation of angular acceleration was investigated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 학술대회 논문집 전문대학교육위원
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• pp.129-131
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• 2000

The moving vehicle with disturbances has the 6 degree of freedom motion in the pitching, Yawing, and rolling directions of two independent axes. The control system in such a moving vehicle has to perform disturbance rejection. This paper present PID controller with disturbance rejection function, low sensitivity filter and notch filter for bending frequency rejection. The performance of a designed system has been certified by the simulation and experiment and experiment results.

• Earthquakes and Structures
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• 제8권6호
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• pp.1481-1497
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• 2015

Vertical earthquake ground motion may magnify vertical dynamic responses of structures, and thus cause serious damage to bridges. As main support structures, piers and bearings play an important role in vertical seismic response analysis of girder bridges. In this study, the pier and bearing are simplified as a vertical series spring system without mass. Then, based on the assumption of small displacement, the equation of motion governing the simply-supported straight girder bridge under vertical ground motion is established including effects of vertical deformation of support structures. Considering boundary conditions, the differential quadrature method (DQM) is applied to discretize the above equation of motion into a MDOF (multi-degree-of-freedom) system. Then seismic responses of this MDOF system are calculated by a step-by-step integration method. Effects of support structures on vertical dynamic responses of girder bridges are studied under different vertical strong earthquake motions. Results indicate that support structures may remarkably increase or decrease vertical seismic responses of girder bridges. So it is of great importance to consider effects of support structures in structural seismic design of girder bridges in near-fault region. Finally, optimization of support structures to resist vertical strong earthquake motions is discussed.

• International Journal of Control, Automation, and Systems
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• 제4권1호
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• pp.1-9
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• 2006

This paper presents the modeling and multivariable feedback control of a novel high-precision multi-dimensional positioning stage. This integrated 6-degree-of-freedom. (DOF) motion stage is levitated by three aerostatic bearings and actuated by 3 three-phase synchronous permanent-magnet planar motors (SPMPMs). It can generate all 6-DOF motions with only a single moving part. With the DQ decomposition theory, this positioning stage is modeled as a multi-input multi-output (MIMO) electromechanical system with six inputs (currents) and six outputs (displacements). To achieve high-precision positioning capability, discrete-time integrator-augmented linear-quadratic-regulator (LQR) and reduced-order linearquadratic-Gaussian (LQG) control methodologies are applied. Digital multivariable controllers are designed and implemented on the positioning system, and experimental results are also presented in this paper to demonstrate the stage's dynamic performance.

• 제어로봇시스템학회논문지
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• 제8권6호
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• pp.484-491
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• 2002

We developed a new type of human-sized BWR (biped walking robot) driven by a new actuator based on the ball screw which has high strength and high gear ratio. Each leg of the robot is composed of three pitch joints and one roll joint. In all, a 10 degree-of-freedom robot with two balancing joints was developed. A new type of actuator for the robot is proposed, which is composed of four bar link mechanism driven by the ball screw. The robot overcomes the limit of the driving torque of conventional BWRs. The BWR was designed to walk autonomously by adapting small DC motors for the robot actuators and has a space to board DC battery and controllers. In the performance test, the BWR performed sitting-up and down motion, and walking motion. Through the test, we found the possibility of a high performance biped-walking.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.743-750
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• 2000

This paper presents an equivalent linearization method and application to the equations of motion of a 6 degree-of-freedom PRRS HexaSlide type parallel manipulators which are characterized as the architecture with constant link lengths that are attached to moving sliders on the ground and to a mobile platform. Since dynamic equations of parallel manipulators are complicated and highly nonlinear, control bandwidth, adjustable control gain as well as vibration characteristics cannot be easily found. The proposed equivalent linearization method can be applied over specified workspace as well as on a path of mobile platform. Through an equivalent linearization method, one can easily get a simple linear dynamic model. This linearized dynamic model may be utilized in a simplified computed torque control strategy.

• Structural Engineering and Mechanics
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• 제21권6호
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• pp.699-712
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• 2005

The response of a plate-column system having five-degree-of-freedom supported by an elastic foundation and subjected to static lateral load, harmonic ground motion and earthquake motion is studied. Two Winkler foundation models are assumed: a conventional model which supports compression and tension and a tensionless model which supports compression only. The governing equations of the problem are obtained, solved numerically and the results are presented in figures to demonstrate the behavior of the system for various values of the system parameters comparatively for the conventional and the tensionless Winkler foundation models.