• Journal of KSNVE
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• v.6 no.3
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• pp.287-296
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• 1996

A virtual work form of flexible multibody dynamic formulation with rotary inertia has been derived. For the analysis of large flexible multibody systems, deformation modal coordinates have been employed to represent coupled motion between gross and vibrational motion. For the efficient evaluation of the entries in the mass matrix, a flexible body has been treated as a collection of mass points. The rotary inertia was generated from the consistent mass matrix in a finite element model. Deformation mode shapes were obtained from finite element analysis. Bending and twisting vibration analyses of a cantilever have been carried out to see rotary inertia effects. A space flexible robot simulation has been also carried out to show effectiveness of the proposed formulation. This formulation is effective to the model that consists of beam, plate, or shell element that contains rotational degree of freedom at the nodal point. It is also effective to the flexible body model to which a large lumped rotary inertia is attached.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.690-695
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• 2005

Flexible circular cantilever beams when excited externally introduce a lot of dynamic characteristics. The non-linear elements that these flexible beams develop include non-linearity due to inertia terms, spring, and damping. They show different characteristics of motion from each other. In the modes of lower order, the non-linearity due to spring is prevalent, while the non-linearity due to inertia Is prevalent in the modes of higher order. To analyze these effects the non-linear phenomena are analyzed experimentally. When the response characteristics of non-linear vibration are analyzed using autospectrum, it is possible to analyze the subharmonic and superharmonic mot ion by comparison. The phase change is analyzed using the method of phase portrait and the non-linear characteristics of response characteristics that are developed in flexible structures can be predicted and applied to the stage of design.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.5
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• pp.495-501
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• 2013

This paper describes a flexible wireless telemetering system using a mesoscale cantilever sensor, which is microfabricated with a patterned thin Ni-Cu foil on a resin substrate. The dynamic validation of the sensor has been conducted in a flow. The wireless telemetry is used to obtain data regarding the oscillating flows. It is shown that the sensor is nearly independent of the environmental temperature and is suitable for application to primary healthcare and diagnostic devices. It can be easily integrated with other modules for measuring physiological parameters, e.g., blood pressure, oxygen saturation, and heart rate, to increase the convenience and reliability of diagnosis. The precision and reliability of the sensor are also dependent on the design of the analog front-end and noise reduction techniques. It is shown that the present system's minimum interval between packet transmissions is ~16 ms.

• Smart Structures and Systems
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• v.25 no.5
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• pp.559-567
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• 2020

Vibration at the tip of various flexible manipulators may affect their operation accuracy and work efficiency. To suppress such vibrations, the feasibility of using MFC actuators and sensors is investigated in this paper. Considering the convergence of the famous filtered-x least mean square (FXLMS) algorithm could not be guaranteed while it is employed for vibration suppression of plants with varying secondary path, this paper proposes a new multiple model switching adaptive control algorithm to implement the real time active vibration suppression tests with a new multiple switching strategy. The new switching strategy is based on a cost function with reconstructed error signal and disturbance signal instead of the error signal from the error sensor. And from a robustness perspective, a new variable step-size sign algorithm (VSSA) based FXLMS algorithm is proposed to improve the convergence rate. A cantilever beam with varying tip mass is employed as flexible manipulator model. MFC layers are attached on both sides of it as sensors and actuators. A co-simulation platform was built using ADAMS and MATLAB to test the feasibility of the proposed algorithms. And an experimental platform was constructed to verify the effectiveness of MFC actuators and sensors and the real-time vibration control performance. Simulation and experiment results show that the proposed FXLMS algorithm based multiple model adaptive control approach has good convergence performance under varying load conditions for the flexible cantilever beam, and the proposed FX-VSSA-LMS algorithm based multiple model adaptive control algorithm has the best vibration suppression performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.356-359
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• 2007

In this paper, the stability of a rotating cantilever pipe conveying fluid with a crack is investigated by the numerical method. That is, the influences of the rotating angular velocity, mass ratio and crack severity on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating pipe are derived using the Euler beam theory and the Lagrange's equation. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations. Generally, the critical flow velocity for flutter is proportional to the angular velocity and the depth of crack. Also, the critical flow velocity and stability maps of the rotating pipe system as a function of mass ratio for the changing each parameter are obtained.

• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.1994-2003
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• 2003

The vibration of a flexible cantilever tube with nonlinear constraints when it is subjected to flow internally with fluids is examined by experimental and theoretical analysis. These kinds of studies have been performed to find the existence of chaotic motion. In this paper, the important parameters of the system leading to such a chaotic motion such as Young's modulus and the coefficient of viscoelastic damping are discussed. The parameters are investigated by means of system identification so that comparisons are made between numerical analysis using the design parameters and the experimental results. The chaotic region led by several period-doubling bifurcations beyond the Hopf bifurcation is also re-established with phase portraits, bifurcation diagram and Lyapunov exponent so that one can define optimal parameters for system design.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.495-500
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• 2003

The vibration of a flexible cantilever tube with nonlinear constraints when it is subjected to flow internally with fluids is examined by experiment and theoretical analysis. These kind of studies have often been performed that finds the existence of chaotic motion. In this paper, the important parameters of the system leading to such a chaotic motion such as Young's modulus and coefficient of viscoelasticity in tube material are discussed. The parameters are investigated by means of a system identification so that comparisons are made between numerical analysis using the parameters of a handbook and the experimental results. The chaotic region led by several period-doubling bifurcations beyond the Hopf bifurcation is also re-established with phase portraits and bifurcation diagram so that one can define optimal parameters for system design.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.917-922
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• 1992

Resently there have been increasing interests in adaptive identification and control of flexible structures. In this paper, vector channel lattice filters and their applications to parameter identification of flexible structures are studied. Numerical examples are given to show its performace to estimate the natural frequencies of 5-mass system. It is observed that vector channel lattice filter convetges quickly and identifies modal frequencies even when some of them is unobservable for some measurements. Experimental results demonstrated the ability of the lattice filter to identify the natural frequencies and the damping ratios of cantilever beam and pipe.

• Structural Engineering and Mechanics
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• v.49 no.1
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• pp.1-22
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• 2014

A seismic evaluation is made of the response to horizontal ground shaking of cantilever retaining walls using the finite element model in three dimensional space whose verification is provided analytically through the modal analysis technique in case of the assumptions of fixed base, complete bonding behavior at the wall-soil interface, and elastic behavior of soil. Thanks to the versatility of the finite element model, the retained medium is then idealized as a uniform, elastoplastic stratum of constant thickness and semi-infinite extent in the horizontal direction considering debonding behavior at the interface in order to perform comprehensive soil-structure interaction (SSI) analyses. The parameters varied include the flexibility of the wall, the properties of the soil medium, and the characteristics of the ground motion. Two different finite element models corresponding with flexible and rigid wall configurations are studied for six different soil types under the effects of two different ground motions. The response quantities examined incorporate the lateral displacements of the wall relative to the moving base and the stresses in the wall in all directions. The results show that the wall flexibility and soil properties have a major effect on seismic behavior of cantilever retaining walls and should be considered in design criteria of cantilever walls. Furthermore, the results of the numerical investigations are expected to be useful for the better understanding and the optimization of seismic design of this particular type of retaining structure.

• The Journal of the Acoustical Society of Korea
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• v.34 no.2
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• pp.108-116
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• 2015

An acoustic vector sensor is a device that is capable of measuring the direction of wave propagation and the acoustic pressure. In this paper, the modeling of micro-cantilever sensor for the vector sensor are proposed by consideration of acoustic phenomenon in water. Two models based on unimorph structure are proposed in this paper and corresponding transfer function which describes the relation between input pressure wave and output voltage depending on incidence angle and frequency of pressure wave is derived based on lumped model. It has been shown that very thin and flexible micro-cantilever can be used to measure directly the particle velocity component in water.