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Published Articles

The Volume 17, No 1, March 2012

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Instantaneous optimal control of seismic response using magnetorheological damping

N. K. Chandiramani, S. P. Purohit


Instantaneous Optimal Control (IOC) is used to obtain desired force from MR damper fitted to a seismically excited building. Excitation is considered when minimizing performance index, unlike in classical optimal controllers. Modified Bouc-Wen damper model and on-off voltage law is considered. Various forms of state weighting matrix are considered for controller design. IOC is compared with Linear Quadratic Regulator(LQR), Linear Quadratic Gaussian(LQG) and Passive-on control. It yields reduction in: maximum peak and maximum RMS interstorey drift; and generally in accelerations vis-a-vis LQR and LQG. IOC Riccati Matrix Type controller appears most effective, yielding: lowest maximum peak drift and maximum peak acceleration and generally best storeywise drift control vis-a-vis passive-on, LQR and LQG; substantially lower peak accelerations vis-a-vis LQR and LQG.

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Active Control of Rotor Vibration in an Electric Machine by Cascaded Optimal and Convergent Control Methods

Juha Orivuori, Kai Zenger, Anssi Sinervo, Antti Laiho


In this paper a method for suppressing radial rotor vibrations of an electric machine using active vibration control is presented. The required control forces are generated by an electro?magnetic actuator implemented as extra windings in the stator slots of the machine. A generic modified optimal LQ?control law cascaded with a convergent controller is introduced to tackle the control problem. The test results obtained by implementation of the designed control algorithms in a 30 kW squirrel?cage induction motor are presented. The results show that the proposed control strategy is capable to significant vibration suppression.

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Acoustic Analysis of a General Network of Multi-Port Elements - An Impedance Matrix Approach

A. Mimani and M. L. Munjal


The present work deals with a generalized algorithm for analyzing a network of linear passive acoustic filters having multi-port elements which are interconnected to each other in an arbitrary manner through their respective ports or through general two-port elements. A multi-port element is characterized by an impedance (Z) matrix and the junctions through which these multi-port elements are connected are characterized by conditions of continuity of acoustic pressure and mass velocity. A connectivity matrix is written for the entire network wherein the interconnections of the elements are taken care of by proper book-keeping of the acoustic state variables. The acoustic pressures at the external nodes (at the network terminations) are related to mass velocity at the external ports by inversion of the connectivity matrix to obtain the global impedance matrix, characterizing the entire network, thereby offering a generalized formulation for dealing with a network of multi-port elements. Generalized expressions are obtained for determination of the acoustic performance parameters (Transmission loss (TL), Insertion loss (IL) and Level Difference (LD)) for a multi-port system in terms of the Z matrix and scattering (S) matrix. A simple method is proposed for evaluation of the Z matrices by means of the axial plane wave theory to characterize long chamber mufflers for a uniform area, conical, exponential and parabolic duct having arbitrary number of ports, whilst the ports can be located on the end faces as well as on the side surfaces. The Z matrices characterizing each of these multi-port elements are then used to analyze arbitrary networks of such multi-port elements, and the results are compared with those of the 3-D FEM based analysis and also against the existing literature.

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On Application of Radiation Loss Factor in the Prediction of Sound Transmission Loss of a Honeycomb Panel

Leping Feng and Sathish Kumar R.


The application of the radiation loss factor in the prediction of sound transmission loss of a lightweight, orthotropic sandwich panel is investigated in this paper. Comparisons with measurements show that predictions often underestimate the sound transmission loss of the panel around the corresponding critical frequency when the measured loss factor, which in principle includes the radiation loss factor, is used. This is due to the measurement methods used for the loss factor and the band average. It is thus recommended to use the loss factor measured at low frequencies plus the theoretical radiation loss factor in order to improve the prediction of the sound transmission loss of a honeycomb panel around the critical frequency.

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