Demonstration of Torsional Behaviour Using Vibration-based Single-storey Model with Double Eccentricities

R. Tabatabaei,H. Saffari 대한토목학회 2010 KSCE JOURNAL OF CIVIL ENGINEERING Vol.14 No.4

The use of single-storey schemes appears necessary in order to investigate lateral-torsional coupling in building structures. In this paper, the torsional behaviour of an eccentric single-storey system based on undamped free vibration analysis has been investigated with particular emphasis on double eccentricities. An eccentricity between the center of rigidity and the center of mass in a building system causes the different torsional behaviour during a seismic loading. This approach reveals clearly how the double eccentric system behaves in relationship with the natural frequencies and modes and translational or torsional motion of the modeling system. From the parametric analysis of such an approach the determinative role of the distance from the center of mass to the center of rotation corresponding to the torsional and lateral stiffness ratio of the system becomes an obvious means of defining the torsional behaviour. From the outcome of applying the model, the building model can be classified as Torsionally Stiff (TS) and Torsionally Flexible (TF) based on the way the model has been configured in terms of the loci of the centers of rotation.

잔류진동 저감을 위한 비대칭 S-curve 프로파일의 영점 배치법

하창완(Chang-Wan Ha),류근호(Keun-Ho Rew),김경수(Kyung-Soo Kim),김수현(Soo-Hyun Kim) 제어로봇시스템학회 2012 제어·로봇·시스템학회 논문지 Vol.18 No.4

Robust tuning rules of the motion profile are proposed to minimize the residual vibration. For asymmetric S-curve profile, tuning rules are analytically formulated using Laplace-domain approach. When the system modeling is known exactly, by placing a single zero of the motion profile on the pole of the system, the residual vibration can be perfectly eliminated under undamped system. However, if there are some amounts of the modeling errors, the residual vibration significantly increases. To track this issue, the robust tuning rules against modeling error are discussed. One of the proposed robust tuning rules is placing the multiple zeros of the motion profile on the pole of the system, and the other is placing the zeros of the motion profile around the pole of the system. Thanks to the proposed robust tuning rules, motion profile becomes more robust to modeling errors while minimizing the residual vibration. By simulation, the effectiveness of the proposed robust tuning rules is verified.

로봇 구동용 BLDC Motor의 영구자석 오버행에 따른 토크 및 진동ㆍ소음 특성

姜圭洪(Gyu-Hong Kang),金德顯(Duck-Hyun Kim) 대한전기학회 2006 전기학회논문지 B Vol.55 No.7

In Brushless DC Motor, there are Permanent Magnets (PMs) with driving circuit and sensor for detecting to rotor position and rotation speed. In the case of using hall IC sensor which response to magnetic flux, that is required to additional sensor magnet for rotor position detecting. Most of BLDC motor, However, take asymmetrical overhang of PM in rotor instead of additional sensor magnet for operating of hall IC sensor. The asymmetrical overhang of PM occur rotor thrust to z-axis direction that is lead to not only damage of bearing but also intensive noise and vibration. Therefore, the analysis of magnet overhang effect in the side of vibration and drive to hall IC sensor is required to precise. In this paper, 2-D Finite Element Method is used to solve precise field computation and thrust of z-axis direction considering asymmetrical magnet overhang. And also the z-axis thrust from the analysis result is compared to experimental result. In conclusion, the purpose of this paper minimize to noise and vibration of BLDC Motor as analyzes to asymmetrical magnet overhang effect.

잔류진동 저감을 위한 비대칭 S-curve 설계

하창완(Chang-Wan Ha),류근호(Keun-Ho Rew),김경수(Kyung-Soo Kim),김수현(Soo-Hyun Kim) 제어로봇시스템학회 2011 제어로봇시스템학회 각 지부별 자료집 Vol.2011 No.12

Tuning rules of the motion profile is proposed to minimize the residual vibration. For asymmetric S-curve profile, tuning rules are formulated using Laplace-domain approach. By placing the zeros of the motion profile on the pole of the system, the residual vibration can be minimized, which results in improvement of setting time. In particular, by placing zeros beside pole, the motion profile can be made robustly against modeling error. By simulations, the proposed approaches are verified.

영구자석 오버행에 의한 BLDC Motor의 전자기적 현상 및 진동특성 해석

姜圭洪(Gyu-Hong Kang),金德縣(Duck-Hyun Kim),金奎卓(Gyu-Tak Kim) 대한전기학회 2006 전기학회논문지 B Vol.55 No.11

In this paper, the estimation of Z-axis thrust ripple and vibration of BLDC motor with asymmetrical permanent magnet overhang is performed by 3-D Finite Element Method (3-D FEM) and vibration experimentation. The ripple of Z-axis thrust is due to armature reaction field in BLDC motor driven to squire wave. That is generating to Z-axis vibration. The analysis results of Z-axis thrust and the vibration by Z-axis thrust ripple is validated by comparison with experimental result.

Direct implementation of stochastic linearization for SDOF systems with general hysteresis

Dobson, S.,Noori, M.,Hou, Z.,Dimentberg, M. Techno-Press 1998 Structural Engineering and Mechanics, An Int'l Jou Vol.6 No.5

The first and second moments of response variables for SDOF systems with hysteretic nonlinearity are obtained by a direct linearization procedure. This adaptation in the implementation of well-known statistical linearization methods, provides concise, model-independent linearization coefficients that are well-suited for numerical solution. The method may be applied to systems which incorporate any hysteresis model governed by a differential constitutive equation, and may be used for zero or non-zero mean random vibration. The implementation eliminates the effort of analytically deriving specific linearization coefficients for new hysteresis models. In doing so, the procedure of stochastic analysis is made independent from the task of physical modeling of hysteretic systems. In this study, systems with three different hysteresis models are analyzed under various zero and non-zero mean Gaussian White noise inputs. Results are shown to be in agreement with previous linearization studies and Monte Carlo Simulation.

Estimation of active multiple tuned mass dampers for asymmetric structures

Chunxiang Li,Xueyu Xiong 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.29 No.5

This paper proposes the application of active multiple tuned mass dampers (AMTMD) for translational and torsional response control of a simplified two-degree-of-freedom (2DOF) structure, able to represent the dynamic characteristics of general asymmetric structures, under the ground acceleration. This 2DOF structure is a generalized 2DOF system of an asymmetric structure with predominant translational and torsional responses under earthquake excitations using the mode reduced-order method. Depending on the ratio of the torsional to the translational eigenfrequency, i.e. the torsional to translational frequency ratio (TTFR), of asymmetric structures, the following three cases can be distinguished: (1) torsionally flexible structures (TTFR < 1.0), (2) torsionally intermediate stiff structures (TTFR = 1.0), and (3) torsionally stiff structures (TTFR > 1.0). The even distribution of the AMTMD within the whole width and half width of the asymmetric structure, thus leading to three cases of installing the AMTMD (referred to as the AMTMD of case 1, AMTMD of case 2, AMTMD of case 3, respectively), is taken into account. In the present study, the criterion for searching the optimum parameters of the AMTMD is defined as the minimization of the minimum values of the maximum translational and torsional displacement dynamic magnification factors (DMF) of an asymmetric structure with the AMTMD. The criterion used for assessing the effectiveness of the AMTMD is selected as the ratio of the minimization of the minimum values of the maximum translational and torsional displacement DMF of the asymmetric structure with the AMTMD to the maximum translational and torsional displacement DMF of the asymmetric structure without the AMTMD. By resorting to these two criteria, a careful examination of the effects of the normalized eccentricity ratio (NER) on the effectiveness and robustness of the AMTMD are carried out in the mitigation of both the translational and torsional responses of the asymmetric structure. Likewise, the effectiveness of a single ATMD with the optimum positions is presented and compared with that of the AMTMD.

The effect of a parabolic potential on the properties of a strongly coupled polaron in an asymmetric Gaussian quantum well

Geng Yan-Bo,Ding Zhao-Hua,Xiao Jing-Lin 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.1

In this work, the effect of parabolic potential on the properties of strongly coupled polaron in an asymmetric Gaussian quantum well (QW) has been studied. Relations of the frequency vibration and the strongly coupled polaron’s ground-state energy in an asymmetric Gaussian QW for RbCl crystals at different confinement strengths along the x and the y directions, the asymmetric Gaussian QW barrier heights, and the Gaussian confinement potential widths and temperatures have been studied using the Lee–Low–Pines unitary transformation and the linear combination operator methods. Calculations show that the absolute value of ground-state energy increased with increasing confinement strengths along the x and the y directions and asymmetric Gaussian QW barrier height, and derease with increeasing Gaussian confinement potential width, and temperature. In addition, vibrational frequency was found to decrease with increasing Gaussian confinement potential width and to increase with increasing confinement strengths along the x and the y directions, asymmetric Gaussian QW barrier height, and temperature. The five parameters involved in this paper are important physical quantities for studying the properties of Gaussian QWs, and have important physical significance for the study of nanomaterials.

Estimation of active multiple tuned mass dampers for asymmetric structures

Li, Chunxiang,Xiong, Xueyu Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.29 No.5

This paper proposes the application of active multiple tuned mass dampers (AMTMD) for translational and torsional response control of a simplified two-degree-of-freedom (2DOF) structure, able to represent the dynamic characteristics of general asymmetric structures, under the ground acceleration. This 2DOF structure is a generalized 2DOF system of an asymmetric structure with predominant translational and torsional responses under earthquake excitations using the mode reduced-order method. Depending on the ratio of the torsional to the translational eigenfrequency, i.e. the torsional to translational frequency ratio (TTFR), of asymmetric structures, the following three cases can be distinguished: (1) torsionally flexible structures (TTFR < 1.0), (2) torsionally intermediate stiff structures (TTFR = 1.0), and (3) torsionally stiff structures (TTFR > 1.0). The even distribution of the AMTMD within the whole width and half width of the asymmetric structure, thus leading to three cases of installing the AMTMD (referred to as the AMTMD of case 1, AMTMD of case 2, AMTMD of case 3, respectively), is taken into account. In the present study, the criterion for searching the optimum parameters of the AMTMD is defined as the minimization of the minimum values of the maximum translational and torsional displacement dynamic magnification factors (DMF) of an asymmetric structure with the AMTMD. The criterion used for assessing the effectiveness of the AMTMD is selected as the ratio of the minimization of the minimum values of the maximum translational and torsional displacement DMF of the asymmetric structure with the AMTMD to the maximum translational and torsional displacement DMF of the asymmetric structure without the AMTMD. By resorting to these two criteria, a careful examination of the effects of the normalized eccentricity ratio (NER) on the effectiveness and robustness of the AMTMD are carried out in the mitigation of both the translational and torsional responses of the asymmetric structure. Likewise, the effectiveness of a single ATMD with the optimum positions is presented and compared with that of the AMTMD.

Diagnosis of Excessive Vibration Signals of Two-Pole Generator Rotors in Balancing

Park, Jong-Po The Korean Society of Mechanical Engineers 2000 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.14 No.6

Cause of excessive vibration with twice the rotational speed of a two-pole generator rotor for the fossil power plants was investigated. The two-pole generator rotor, treated as a typically asymmetric rotor in vibration analysis, produces asynchronous vibration with twice the rotational speed, sub-harmonic critical speeds, and potentially unstable operating zones due to its own inertia and/or stiffness asymmetry. This paper introduces a practical balancing procedure, and presents the results of the investigation on sources of the excessive vibration based on the experimental vibration data of the asymmetric two-pole rotor in balancing.