Ph.D. Dissertation Title: Mechanical Realization Theory and its Application to Machinery Emulation

Author: Wenyuan Chen

University: Boston University, College of Engineering

Graduation Year: 2004

Advisor: Pierre E. Dupont, Ph.D., Associate Professor of Department of Aerospace and Mechanical Engineering, Boston University

Committee Members:

Allan D. Pierce, Ph.D., Professor, Fellow of Acoustical Society of America, Editor-in-Chief of Journal of Acoustical Society of America

John Baillieul, Ph.D., Professor, Chair, IEEE Fellow, President of IEEE Control Systems Society, Former Editor-in-Chief of IEEE Transactions on Automatic Control

J. Gregory McDaniel, Associate Professor, Fellow of Acoustical Society of America, Associate Editor of Journal of Acoustical Society of America

Pierre E. Dupont, Associate Professor, IEEE Senior Member, Associate Editor of IEEE Transactions on Robotics and Automation

ABSTRACT

The realization of electromechanical dynamic systems possessing specified input-output dynamic properties is studied. Applications of this problem include the scaled shock and vibration testing of complicated structures, the design of electromechanical filters and the design of vibration absorbers. A two-step realization process is developed by which both passive and active systems can be realized. In the first step, a passive mechanical system is obtained, which is then modified in the second step to achieve active realization. For example, in machinery emulation, the goal is to design an electromechanical system which matches the vibrational energy flow at the locations where the machinery attaches to its foundation. In this case, the passive realization would correspond to the machinery when it is not in operation while the active realization would also account for the vibrational energy produced during machinery operation.

Two techniques have been developed to obtain realizable models for the design of passive mechanical systems. The first technique involves searching the parameterized space of congruent coordinate transformations relating input-output equivalent second order models for those that are realizable, i.e., those that can be directly interpreted as a network of mechanical elements. %Necessary conditions for realizability of both single-input, single-output (SISO) %and multi-input, multi-output (MIMO) mechanical systems have been derived. The second technique involves estimating realizable models which include both distributed and lumped mechanical elements directly from experimental machinery data. This approach utilizes a cost function dependent on accelerance and dynamic mass errors. Active emulation is achieved by adding vibration sources, e.g., shakers, to the passive structure. These sources are driven under closed-loop control so as to produce the desired level of vibration at the output locations. Experimental evaluation of these techniques has been carried out through the design of a modular, SISO machinery emulator, which can be adapted to match the mass and dynamic properties of a desired machine within a frequency range of interest. Experimental results demonstrating the effectiveness of the techniques for both passive and active emulation are presented. My Ph.D. dissertation can be downloaded here:

Mechanical Realization Theory and its Application to Machinery Emulation

Below are my latest publications on Journal of Acoustical Society of America, one of the best journals in acoustics and vibration field.

Paper 1: Wenyuan Chen and Pierre E. Dupont, Electromechanical Emulation of Active Vibratory Systems, Journal of Acoustical Society of America - JASA Express Letters, Vol. 119(3), pp.EL27-EL33, March 2006.
Paper 2: Wenyuan Chen and Pierre E. Dupont, Realization of Mechanical Systems from Second-order Models, Journal of Acoustical Society of America, Vol. 118(2), pp.762-773, August 2005.

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