• Title/Summary/Keyword: Pitch motion

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Chaos Control of the Pitch Motion of the Gravity-gradient Satellites in an Elliptical Orbit (타원궤도상의 중력구배 인공위성의 Pitch운동의 혼돈계 제어)

  • Lee, Mok-In
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.39 no.2
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    • pp.137-143
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    • 2011
  • The pitch motion of a gravity-gradient satellite can be chaotic, depending on the ratio of mass moments of inertia and the eccentricity of the satellite orbit. For a precise prediction of motion, chaotic pitch motion has to be changed to non-chaotic motion. Feedback control can be used to obtain nonchaotic pitch motion. For chaos control and stabilization of the pitch motion of a gravity-gradient satellite, a feedback control system is designed, based on the linear nonautonomous system obtained by linearizing the nonlinear pitch motion. The control law obtained has two parameters and is applied to chaotic nonlinear pitch motion. The nonlinear control system satisfies the proposed control objectives in the range of the nonchaotic parameter space.

Pitch Directional Swimming Control of Multi-Legged Biomimetic Underwater Robot (CALEB10) (다족형 생체모방 수중 로봇(CALEB10)의 Pitch 유영 제어)

  • Lee, Hansol;Lee, Jihong
    • The Journal of Korea Robotics Society
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    • v.12 no.2
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    • pp.228-238
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    • 2017
  • The CALEB10 is a multi-legged biomimetic underwater robot. In the last research, we developed a swimming pattern named ESPG (Extended Swimming Pattern Generator) by observing diving beetle's swimming actions and experimented with a positive buoyancy state in which CALEB10 floats on the water. In this paper, however, we have experimented with CALEB10 in a neutral buoyancy state where it is completely immersed in water for pitch motion control experiment. And we found that CALEB10 was unstably swimming in the pitch direction in the neutral buoyancy state and analyzed that the reason was due to the weight proportion of the legs. In this paper, we propose a pitch motion control method to mimic the pitch motion of diving beetles and to solve the problem of CALEB10 unstably swimming in the pitch direction. To control the pitch motion, we use the method of controlling additional joints while swimming with the ESPG. The method of obtaining propulsive force by the motion of the leg has a problem of giving propulsive force in the reverse direction when swimming in the surge direction, but this new control method has an advantage that a propulsive moment generated by a swimming action only on a target pitch value. To demonstrate validity this new control method, we designed a dynamics-based simulator environment. And the control performance to the target pitch value was verified through simulation and underwater experiments.

Magnetic Levitation Control through the Introduction of Bogie Pitch Motion into a Control Law (대차 피치운동을 반영한 흡인식 자기부상제어)

  • Ha, Chang-Wan;Kim, Chang-Hyun;Jo, Jeong-Min;Lim, JaeWon;Han, Hyung-Suk
    • Journal of the Korean Society for Railway
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    • v.18 no.2
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    • pp.87-93
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    • 2015
  • The uneven reaction surface profile facing the lift magnets in attractive Maglev vehicles naturally brings about pitch motion of the bogie. In particular, in the placement configuration of the long stator of the linear synchronous motor (LSM) on the track for high-speed propulsion, surface irregularities and the offsets between the stator packs create measurable airgaps, i.e., the clearance between the magnet and the stator, with discontinuously extreme values, resulting in bogie pitch motion. This occurs because the airgap velocities and accelerations derived by the differentiations of the measured air-gaps are used to determine the voltages applied to the magnets. This paper incorporates bogie pitch motion into a control law for each magnet controller to reduce the variations in both the airgap and the pitch angle. The effectiveness of the proposed method is analyzed using a full-scale Maglev vehicle running over a test track.

Passive Maglev Carrier Control with Consideration of Pitch Motion (피치 운동을 고려한 자기부상 수동형 이송자 제어)

  • Lee, Younghak;Kim, Chang-Hyun;Ha, Chang-Wan;Park, Doh-Young;Yang, Seok-Jo;Lim, Jaewon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.2
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    • pp.213-220
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    • 2016
  • This research aims to develop core technologies for passive carrier (no power in carrier itself) transfer system. The technologies are passive levitation, propulsion, and guidance, which can be great benefits for semiconductor and display manufacturing industries. Passive maglev carrier is necessary to precise position control for quiet and stable transfer operation. However, the structural characteristics of carrier and the installation errors of gap sensors cause the pitch motion. Hence, the controller design in consideration of pitch motion is required. This study deals with the reduction control of carrier pitch motion. PDA controller and PDA controller with pitch control are proposed to compare the pitch angle analysis. The pitch angle and the levitation precision are measured by experiment. Finally, the optimized design of pitch controller is presented and the effects are discussed.

On the Motions of High Speed Surface-Effect-Ship in Waves

  • Lee, G.J.
    • Journal of Hydrospace Technology
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    • v.1 no.2
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    • pp.13-35
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    • 1995
  • The motion response of a high speed SES in waves is important because the ride quality of passengers is mainly affected by it. The pitch motion has a large influence on the vertical motion at the bow. But the pitch motion of SES does not have been analyzed properly. The reason for that is the absence of proper mathematical model for the stem bag, the bow seal, and the inherent non-linearity. In this paper, the heave and pitch motion of high speed SES in waves have been treated. For doing it, the mathematical model for the stern bag was set up, and the hydrodynamic forces on the side hulls were obtained by using the principle of momentum change. The motion responses in waves were calculated, and the analysis of the motions was done.

Study on Dynamic Stability of Cylindrical Structure in Waves (파랑 중 실린더형 구조물의 동적 안정성에 대한 연구)

  • Jang, Min-Suk;Jo, Hyo-Jae;Hwang, Jae-Hyuk;Kim, Jae-Heui;Lee, Byeong-Seong;Park, Chung-Hwan
    • Journal of Ocean Engineering and Technology
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    • v.31 no.3
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    • pp.196-201
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    • 2017
  • A cylindrical structure has a very long period of heave and pitch motion response in ocean waves. To obtain the dynamic stability of a cylindrical structure, it is necessary to obtain the suitable metacentric height (GM). However, in a structure with sufficient metacentric height, Mathieu instability can occur if the natural frequency of the heave motion is double the natural frequency of the roll and pitch motion. This study carried out numerical calculations and experiments for vertical-axis wind turbines with cylindrical floaters, which had three different centers of gravity. In the regular wave experiment, the divergence of the structure motion without yaw was observed when the natural frequency of the heave motion was double the natural frequency of the roll and pitch motion. In the irregular wave experiment, the motion spectra of the structures with the different centers of gravity were compared, and one was very high when the natural frequency of the heave motion was double the natural frequency of the roll and pitch motion.

Resonant response of spar-type floating platform in coupled heave and pitch motion

  • Choi, E.Y.;Cho, J.R.;Jeong, W.B.
    • Structural Engineering and Mechanics
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    • v.65 no.5
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    • pp.513-521
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    • 2018
  • In this paper, the resonance response of spar-type floating platform in coupled heave and pitch motion is investigated using a CPU time-effective numerical method. A coupled nonlinear 2-DOF equation of motion is derived based on the potential wave theory and the rigid-body hydrodynamics. The transient responses are solved by the fourth-order Runge-Kutta (RK4) method and transformed to the frequency responses by the digital Fourier transform (DFT), and the first-order approximation of heave response is analytically derived. Through the numerical experiments, the theoretical derivation and the numerical formulation are verified from the comparison with the commercial software AQWA. And, the frequencies of resonance arising from the nonlinear coupling between heave and pitch motions are investigated and justified from the comparison with the analytically derived first-order approximation of heave response.

Implementation of 3D Motion Simulator with Two Degrees of Freedom (2자유도를 갖는 3차원 운동 시뮬레이터 연구)

  • Choi, Myoung-Hwan;Kim, Young-Jin
    • Journal of Industrial Technology
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    • v.21 no.A
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    • pp.81-88
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    • 2001
  • In this work, we have developed a 2 degrees of freedom(DOF) motion simulator that can generate the sensation of motion in a 6 DOF space. The motion base has the DOF of roll and pitch, and the purpose of the motion base is to create the sensation of riding a vehicle in a 3D space by controlling the motion base. The dynamics of the mechanism was analysed and the optimal design of the motion base mechanism has been reached. The prototype motion base mechanism was developed and tested. The multi-axis motion controller(MMC) was used to control the two AC servo meters that drive the roll and pitch motion.

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The Melnikov Analysis of the Pitch Dynamics of a Gravity Gradient Satellite (중력구배 인공위성의 Pitch운동의 Melnikov해석)

  • Lee, Mok-In
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.12
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    • pp.1427-1432
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    • 2009
  • The pitch motion of a generic gravity gradient satellite is investigated in terms of chaos. The Melnikov method is used for detecting the onset of chaotic behavior of the pitch motion of a gravity gradient satellite. The Melnikov method determines the distance between stable and unstable manifolds of a perturbed system. When stable and unstable manifolds transverse on the Poincare section, the resulting motion can be chaotic. The Melnikov analysis indicates that the pitch dynamics of a generic gravity gradient satellite can be chaotic when the orbit eccentricity is small.

The Research of 2 DOF 3D Motion Simulator (2 DOF 3D 운동 시뮬례이터 실험)

  • 김영진;최명환
    • 제어로봇시스템학회:학술대회논문집
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    • pp.260-260
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    • 2000
  • In this work, we have developed a 2 degree of freedom(DOF) motion simulator that can generate the sensation of motion in a 6 DOF space. The motion base has the DOF of roll and pitch, and the purpose of the motion base is to create the sensation of riding a vehicle in a 3D space by controlling the motion base. The dynamics of the mechanism was analysed and the optimal design of the motion base mechanism has been reached. The prototype motion base mechanism was developed and tested. The multi-axis motion controller(MMC) was used to control the two ac servo motors that drive the roll and pitch motion.

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