• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.883-889
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• 2005

Micro robots have been developed for many applications: medical, industrial, military, and so on. A small mobile robot was built and it has three legs made of bimorph piezoelectric actuators. It proceeds by vibrating the rear leg and it rotates by vibrating one of the front legs. The locomotion of the robot is described by relative position of mass center and the friction between the legs and the floor. This paper describes the principles of locomotion and modeling of the robot Modeling was simulated to investigate the dynamics of its mobility. The simulation results verified the modeling by showing similar movement of the robot as measured. It remained, however, several problems through experiments such as crooked direction of forward movement and proceeding speed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.451-456
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• 2006

This paper is concerned with the dynamic modeling and controller design for a cylindrical shell equipped with MFC actuators. The dynamic model was derived by using Rayleigh-Ritz method based on Donnel-Mushtari shell theory. The actuator and sensors for the MFC actuator equations were derived based on pin-force model. The boundary conditions at both ends were assumed to be shear diaphragm. After calculating the natural vibration characteristics, the positive position feedback controller was designed to cope with the first two modes. To this end, the equations of motion were reduced to modal equations of motion by considering the modes of interest. The theoretical results show that vibrations can be successfully suppressed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.725-730
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• 2002

This paper presents an efficient modeling method for open cracked beam structures. An equivalent bending spring model is introduced to represent the structural weakening effect in the presence of open cracks. The proposed method adopts the exact dynamic element method (EDEM) to avoid the difficulty and numerical errors in association with re-meshing the structure. The proposed method is rigorously compared with a commercial finite element code. Experiments are also performed to validate the proposed modeling method. Finally, a diagnostic scheme for open cracked beam structures is proposed and demonstrated through a numerical example.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.228-233
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• 2002

General modeling of a resonant shunting damper has been made from piezoelectric sensor/actuator equation. It is found that an additional damping, which is augmented to a system, is generated by the shunt damping effect. The transfer function of the tuned electrical absorber is derived for both series and parallel shunt circuit. The governing equations and associated boundary conditions are derived using Hamilton's Principle. The shunt voltage equation is also derived from the charge generated in PZT due to beam vibration. The frequency response function of the obtained mathematical model is compared with that of the tuned electrical absorber and experimental work. The vibration amplitude is reduced about 15 dB at targeted second mode frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.200-205
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• 1998

Although discretization methods such as the transfer matrix method (TMM) and the finite element method (FEM) have played an important role in the design or analysis of rotor-bearing systems, continuous system modeling and analysis are often desirable especially for sensitivity analysis or design. The present paper proposes a comprehensive modeling procedure to obtain exact solution of general rotor-bearing systems. The proposed method considers a Timoshenko beam model and makes use of complex coordinate in the formulation. The proposed method provides exact eigensolutions and frequency response functions (FRFS) of general multi-stepped rotor-bearing systems. The first numerical example compares the proposed method with FEM. The numerical study proves that the proposed method is very efficient and useful for the analysis of rotor-bearing systems.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.7
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• pp.659-666
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• 2009

This paper proposes a new method for dynamic modeling of electrorheological(ER) damper considering fluid compressibility. After describing configuration and operating principle of the ER damper, a quasi-static modeling of the ER damper is conducted on the basis of Bingham model of ER fluid. Subsequently, the dynamic model for describing the ER damper considering compressibility of ER fluid and gas chamber is obtained using the lumped parameter method. This method includes dynamic motions of annular duct, upper chamber, lower chamber and connecting pipe. The hysteresis behavior of the ER damper is evaluated through computer simulations and compared with experimental results. In addition, the hysteresis behavior due to the compressibility of ER fluid and gas chamber is investigated through computer simulations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.75-80
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• 2007

This paper is concerned with the dynamic modeling and controller design for a cylindrical shell equipped with MFC actuators. The dynamic model was derived by using Rayleigh-Ritz method based on Donnel-Mushtari shell theory. The actuator and sensors for the MFC actuator equations were derived based on pinforce model. The boundary conditions at both ends were assumed to be shear diaphragm. After calculating the natural vibration characteristics, the positive position feedback controller was designed to cope with the first two modes. To this end, the equations of motion were reduced to modal equations of motion by considering the modes of interest. The theoretical results show that vibrations can be successfully suppressed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.413-418
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• 1998

In this paper, a dynamic modeling approach is introduced to identify the dynamic characteristics of the structural/mechanical joints within an one-dimensional structure. A structural joint is represented by the four-pole parameters and the four-pole parameters are determined from the measured frequency response functions by using the spectral element method. As the illustrative examples, a cantilevered beam and a clamped-clamped beam, each consists of two beams connected by a bolted joint, are investigated to evaluate the present modeling approach. It is found that the dynamic responses predicted by using the identified four-pole parameters for the bolted joint are well agreed with the dynamic responses measured up to high frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.438-443
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• 2009

This paper proposes a new method for dynamic modeling of electrorheological (ER) damper considering fluid compressibility. After describing configuration and operating principle of the ER damper, a quasi-static modeling of the ER damper is conducted on the basis of Bingham model of ER fluid. Subsequently, the dynamic model for describing the ER damper considering compressibility of ER fluid and gas chamber is obtained using the lumped parameter method. This method includes dynamic motions of annular duct, upper chamber, lower chamber and connecting pipe. The hysteresis behavior of the ER damper is evaluated through computer simulations and compared with experimental results. In addition, the hysteresis behavior due to the compressibility of ER fluid and gas chamber is investigated through computer simulations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.227-232
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• 1995

This paper presents a digital modeling technique for the distributed parameter system. The basic idea of the proposed technique is to discretize a continuous system with respect to the spatial coordinate using the approximate methods such as bilinear method and backward difference method. The response of the discretized system is analyzed by Laplace transform and Z transform. The computational result of the proposed technique in a torsional shaft is compared with the exact solution and the result of the finite element method.