Junji Tani

Vibration Control of a Cylindrical Shell Using Distributed Piezoelectric Sensors and Actuators

This paper presents a study on vibration control of a cylindrical shell using distributed piezoelectric sensors and actuators which are parts of the shell wall. Modal expansion method is used in establishment of the state equation of the system. The robust control including JO. control theory and A-synthesis method are applied to the design of the controller which satisfies given control performance and robust stability. Simulation and experiment are carried out when the shell is excited at the resonance frequency of a controlled mode. The results show good agreement between simulation and experiment, as well as the effectiveness of the method using distributed sensors and actuators, and qK0. control theory and t-synthesis method.

Vibration Control of a Cylindrical Shell Using Piezoelectric Actuators

This paper presents a method to control the vibration of a cylindrical shell system. The cylindrical shell system consists of a layer of plastic film and two layers of piezoelectric film, a part of which is used as the actuator. This study presents the analysis of vibration problem caused by periodic excitation. The problem is solved by means of the modal expansion method. A numerical simulation and an experiment of vibration control are performed by applying.<,(control theory to the cylindrical shell system. The result shows the effectiveness for the suppression of the forced vibration of the cylindrical shell system by using this control method.

Vibration control of a cylindrical shell used in MRI equipment

One major problem in magnetic resonance image (MRI) equipment is the high-level noise borne by the vibration of the cylindrical shell to support the coils for gradient magnetic fields. The vibration of the shell is excited by the Lorentz force between the pulse current applied to the coils and the main magnetic field. In order to suppress the noise inside the cylindrical shell, it is aimed to control the vibration of the shell. In this paper, simulation is carried out on the vibration control of the shell by using distributed piezoelectric actuators. The actuators produce a bending moment or an in plane force when pulse voltages are applied synchronously with the pulse current of the coils. Coupling of actuators and vibration modes, and parameter optimization are also discussed. The simulation results show that the vibration level is successfully reduced in the frequency range of 400-1200 Hz.

Energy propagating surface due to a point wave source in an anisotropic laminated plate.

A numerical method is presented to determine the dispersion relation of wave propagation in an anisotropic laminated plate. A phase velocity surface, phase slowness surface, phase wave surface, group velocity surface, group slowness surface and group wave surface are defined and obtained using Reyleighs quotient. The six characteristic surfaces can be used to illustrate the characteristics of the wave propagation in the anisotropic laminated plate due to the point wave source in it. As an example, the characteristic surfaces are obtained for graphite /epoxy angle-ply laminated plates and a hybrid composite laminated plate which consists of carbon/epoxy and glass/epoxy layers. The results for the graphite/epoxy laminated plates are compared with those obtained by the other approximated theory.

A semiexact method for harmonic wave propagation in anisotropic laminated bars of rectangular cross section.

A semiexact method is presented for investigating harmonic wave propagation in arbitrary anisotropic laminated bars of rectangular cross section. In the thickness direction, the laminated bar is divided into N plate elements. The displacement field within each element is approximated by a linear expansion in the thick direction and exponential functions in the other two directions. The principle of virtual work is applied to determining the characteristic values in the width direction. Then the dispersion relations are obtained by using boundary conditions. As examples, the characteristic frequencies are calculated for an isotropic bar, an unidirectional carbon/epoxy laminated one and a hybrid composite laminated one which consists of carbon/epoxy and glass/epoxy layers. The results of the isotropic bar and unidirectional carbon/epoxy laminated one are compared with those obtained by other methods.

Static behavior of a pipe string designed for mining manganese nodules.

On the basis of linear beam theory, the static behavior of a pipe string designed for mining manganese nodules is formulated as a singularly perturbed boundary-value problem. This problem is analyzed by the method of matched asymptotic expansions and Galerkins method. Static pipe deflections and bending moments are evaluated for the practical range of towing speeds of the ship. The pipe deflections obtained by Galerkins method agree well with those by the method of matched asymptotic expansions. However, it is found that Galerkins method with the beam function is not effective in evaluating bending moments of the pipe string.