• Title/Summary/Keyword: Slewing Mode

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Active Vibration Control of Slewing Smart Beam (회전지능보의 능동진동제어)

  • Nam, Sang-Hyun;Kwak, Moon-Kyu
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.257-262
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    • 2000
  • This research is concerned with the active vibration control of slewing smart structures subjected to rotating disturbance. When cantilever beam rotates about axes perpendicular to the undeformed beam's longitudinal axis, it experiences inertial loading. Hence, the beam vibrates after the slewing ends. In this paper, the analytical model for a single slewing flexible beam with surface bonded piezoelectric sensor and actuator is developed using the Hamilton's principle with discretization by the assumed mode method. The theoretial model is verified by the experimental open loop frequency response data. The controller is designed for residual vibration suppression after slewing. The designed cotroller is a positive position feedback (PPF) controller for controlling the first mode vibration.

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A Study on the Valid Dynamic Modeling for the Slewing and Vibration Suppression Control of Beam (보의 회전 및 진동제어를 위한 동적 모델 타당성 연구)

  • 곽문규;남상현
    • Journal of KSNVE
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    • v.11 no.2
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    • pp.292-300
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    • 2001
  • This research is concerned with the validation of the modeling technique and controller design for slewing beam structures. When cantilever beam rotates about axes perpendicular to the undeformed beam's longitudinal axis, it experiences inertial loading. Hence, the beam vibrates from the initial stage of slewing. In this paper, the analytical model for a single slewing flexible beam with surface bonded piezoelectric sensor and actuator is developed using the Hamilton's principle with discretization by the assumed mode method. Comparisons with the theoretical model are made based upon the frequency responses and time responses. A new factor called the coupling coefficient is introduced to incorporate the discrepancies between the theoretical and experimental results. The slewing is achieved by applying the PID control, which is found to be less sensitive to vibrations. The vibrations are controlled by PPF controller, which is found to be effective in suppressing residual vibrations after slewing. The vibrations occurred during slewing is difficult to control because the piezoceramic actuator is not powerful enough to overcome inertial loadings.

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Modeling Technique and Controller Design for Slewing Smart Structure (회전구조물의 모델링 개선 및 제어기 설계)

  • Kwak, Moon-Kyu
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.11a
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    • pp.674-679
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    • 2000
  • This research is concerned with the modeling technique and active vibration controller design for slewing smart structures. When cantilever beam rotates about axes perpendicular to the undeformed beam's longitudinal axis, it experiences inertial loading. Hence, the beam vibrates from the initial stage of slewing, In this paper, the analytical model for a single slewing flexible beam with surface bonded piezoelectric sensor and actuator is developed using the Hamilton's principle with discretization by the assumed mode method. It is found from experiments that the theoretical model lacks the frictional effect. The frictional effect is incorporated into the equations of motion by employing the coupling factor. Theoretical and experimental results show problems arising in modeling and controller design.

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Condition Monitoring of Low Speed Slewing Bearings Based on Ensemble Empirical Mode Decomposition Method

  • Caesarendra, W.;Park, J.H.;Choi, B.H.;Kosasih, P.B.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2012.10a
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    • pp.388-393
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    • 2012
  • Vibration condition monitoring at low rotational speeds is still a challenge. Acoustic emission (AE) is the most used technique when dealing with low speed bearings. At low rotational speeds, the energy induced from surface contact between raceway and rolling elements is very weak and sometimes buried by interference frequencies. This kind of issue is difficult to solve using vibration monitoring. Therefore some researchers utilize artificial damage on inner race or outer race to simplify the case. This paper presents vibration signal analysis of low speed slewing bearings running at a low rotational speed of 15 rpm. The natural damage data from industrial practice is used. The fault frequencies of bearings are difficult to identify using a power spectrum. Therefore the relatively improved method of empirical mode decomposition (EMD), ensemble EMD (EEMD) is employed. The result is can detect the fault frequencies when the FFT fail to do it.

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Analytical Study on the Slewing Dynamics of Hybrid Coordinate Systems (복합좌표계 시스템의 선회동역학에 관한 해석적 연구)

  • Suk, Jin-Young
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.6
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    • pp.36-44
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    • 2003
  • In this paper, an analytic solution method is proposed to overcome the numerical problems when the slewing dynamics of hybrid coordinate systems is investigated via time finite element analysis. It is shown that the dynamics of the hybrid coordinate systems is governed by the coupled dual differential equations for both slewing and structural modes. Structural modes are transformed into the time-based modal coordinates and analytic spatial propagation equations are derived for each space-dependent time mode. Slew angle history is obtained analytically by appropriate applications of the boundary conditions and structural propagation is re-calculated using the slew angle. Numerical examples are demonstrated to validate the proposed analytic method in comparison to the existing state transition matrix method.

Condition Monitoring of Low Speed Slewing Bearings Based on Ensemble Empirical Mode Decomposition Method (EEMD법을 이용한 저속 선회베어링 상태감시)

  • Caesarendra, W.;Park, J.H.;Kosasih, P.B.;Choi, B.K.
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.2
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    • pp.131-143
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    • 2013
  • Vibration condition monitoring of low-speed rotational slewing bearings is essential ever since it became necessary for a proper maintenance schedule that replaces the slewing bearings installed in massive machinery in the steel industry, among other applications. So far, acoustic emission(AE) is still the primary technique used for dealing with low-speed bearing cases. Few studies employed vibration analysis because the signal generated as a result of the impact between the rolling element and the natural defect spots at low rotational speeds is generally weak and sometimes buried in noise and other interference frequencies. In order to increase the impact energy, some researchers generate artificial defects with a predetermined length, width, and depth of crack on the inner or outer race surfaces. Consequently, the fault frequency of a particular fault is easy to identify. This paper presents the applications of empirical mode decomposition(EMD) and ensemble empirical mode decomposition(EEMD) for measuring vibration signals slewing bearings running at a low rotational speed of 15 rpm. The natural vibration damage data used in this paper are obtained from a Korean industrial company. In this study, EEMD is used to support and clarify the results of the fast Fourier transform(FFT) in identifying bearing fault frequencies.

A Robust Control Approach for Maneuvering a Flexible Spacecraft

  • Sung, Yoon-Gyeoung;Lee, Jea-Won;Kim, Hunmo
    • Journal of Mechanical Science and Technology
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    • v.15 no.2
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    • pp.143-151
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    • 2001
  • In the paper, a robust control mechanism is presented to maneuver a flexible spacecraft with the deflection reduction during large slewing operation at the same time. For deflection reduction and maneuvering of the flexible spacecraft, a control mechanism is developed with the application of stochastic optimal sliding-mode control, a linear tracking model and input shaping technique. A start-coast-stop maneuver is employed as a slewing strategy. It is shown that the control mechanism with he strategic maneuver results in better performance and is more efficient than rigid-body-like maneuver, by applying to the Spacecraft Control Laboratory Experiment (SCOLE) system in a space environment.

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Robust Slewing Control of A Flexible Space Structure using Sliding Surface (슬라이딩 평면을 이용한 유연우주비행체의 강인 선회제어)

  • Kim, Jin Hyeong;Hong, Chang Ho;Seok, Jin Yeong;Bang, Hyo Chung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.2
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    • pp.63-71
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    • 2003
  • This paper presents a robust slewing control of a flexible space structure based on sliding surface design. A sliding surface is designed for a single-axis rest-to-rest slewing in view of target angle, target angular velocity, and root monent of the flexible appendage. In comparison with the Lypunov control law, both controllers guarantee the stability and command tracking capabilities for nominal system. It is also shown that the designed control law provides further robustness to internal/external uncertainties. Extending the results of a single-axis maneuver, a sliding mode control law was sought for an arbitrary three-axis maneuver. Quaternion was used to determine the attitude of a space structure and sliding surfaces were designed for each axis, thereby a robust control law was derived considering the coupling effects between each rotational axis during the maneuver. Several numerical examples were demonstrated to show the effectiveness of the designed control law.

A Study on the Linear Pulse Motor Control by using the Microstep Method (Microstep방식을 이용한 Linear Pulse Motor 제어에 관한 연구)

  • Ahn, Jong-Bo;Kwon, Hyuk;Lee, Sang-Jeong;Kim, Yong-Joo
    • Proceedings of the KIEE Conference
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    • 1993.07b
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    • pp.840-843
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    • 1993
  • In this paper, an LPM controller using microprocessor was implemented and adopted Microstep method to control the LPW. In Microstep method, current waveform is sinusoidal not square. This method is characterized by less vibrating, less noisy, and more precise position control. Also, we simulate the static thrust characteristics for each waveform. The experiment was performed according to the mechanical vibration at the acceleration mode and slewing mode. The current tracks reference sinusoidal waveform well and stability was improved as we expected. Therefore, the possibility of the open loop position control was proposed.

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Flexural-Torsional Coupled Vibration of Slewing Beams Using Various Types of Orthogonal Polynomials

  • Kapania Rakesh K.;Kim, Yong-Yook
    • Journal of Mechanical Science and Technology
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    • v.20 no.11
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    • pp.1790-1800
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    • 2006
  • Dynamic behavior of flexural-torsional coupled vibration of rotating beams using the Rayleigh-Ritz method with orthogonal polynomials as basis functions is studied. Performance of various orthogonal polynomials is compared to each other in terms of their efficiency and accuracy in determining the required natural frequencies. Orthogonal polynomials and functions studied in the present work are: Legendre, Chebyshev, integrated Legendre, modified Duncan polynomials, the special trigonometric functions used in conjunction with Hermite cubics, and beam characteristic orthogonal polynomials. A total of 5 cases of beam boundary conditions and rotation are studied for their natural frequencies. The obtained natural frequencies and mode shapes are compared to those available in various references and the results for coupled flexural-torsional vibrations are especially compared to both previously available references and with those obtained using NASTRAN finite element package. Among all the examined orthogonal functions, Legendre orthogonal polynomials are the most efficient in overall CPU time, mainly because of ease in performing the integration required for determining the stiffness and mass matrices.