Title

Fuzzy approach for the analysis and optimal control of composite structures with application to damage detection and health monitoring

Date of Award

2002

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Mechanical Engineering

First Committee Member

Singiresu S. Rao, Committee Chair

Abstract

A theoretical study has been conducted on the analysis and optimal control of laminated composite structures with application to damage detection and health monitoring in the presence of uncertainties. The uncertainties in material properties, geometry and external loads have been modeled as fuzzy quantities and fuzzy logic has been used to develop structural analysis models. The use of fuzzy optimal controllers in structural health monitoring has been explored. The optimal design of the structure, which constitutes a health monitoring system, is also explored. Numerical simulations have been conducted to demonstrate the applicability and utility of the proposed techniques.In order to model the uncertainties of the laminated composite structure that are introduced during manufacturing and assembling, fuzzy logic and fuzzy set theory is used. Using the fuzzy set theory and fuzzy computations, the fuzzy mechanics characteristics of laminated composite materials and structures such as beams and plates are established. The fuzzy finite element method is explored to model and analyze composite structures. Based on the fuzzy finite element models, possible static and dynamic responses are determined. For the health monitoring of a composite structure, damage can be detected by comparing the responses with those of an undamaged structure. Further, a fuzzy optimal controller is theoretically explored which will serve to maintain the performance and health of the structure. The stability characteristics of the controller design are also studied. Next, the conceptual development of a fuzzy smart structure including sensors, actuators, a fuzzy structural model, as well as a fuzzy optimal controller is presented. Finally, the optimal structure, obtained by considering fuzzy input parameters, minimum weight and structural and control performance constraints, is used to achieve a fuzzy smart structure.Several applications and numerical results are presented along with a discussion and interpretation of the results. The results demonstrate that the fuzzy approach is an effective tool to deal with the uncertainties present in composite structures and can provide more realistic solutions. The methodology presented for the fuzzy optimal control can be used for the health monitoring and damage detection of composite structures.

Keywords

Engineering, Mechanical

Link to Full Text

http://access.library.miami.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3071265