Distributed Sensing of a Cantilever Beam and Plate Using a Fiber Optic Sensing System

As the capabilities of Fiber Optic Sensing Systems continue to improve, their application to real-time distributed sensing for structural analysis and control of flexible systems is increasingly feasible. This paper will report experimental results on the use of a Fiber Optic Sensing System for static and dynamic shape estimation of a cantilever beam and plate. Demonstrating the use of this sensor technology in benchtop experiments is the first step in effectively incorporating fiber optic sensors in the Integrated Adaptive Wing Technology Maturation aeroelastic half-span wind tunnel model for real-time shape sensing and feedback for drag optimization, maneuver load alleviation, gust load alleviation, and flutter suppression control laws. The effectiveness of the sensing system will be analyzed and the application of these results to aeroelasticity experimentation will be discussed

Distributed Sensing and System Identification of Cantilever Beams and Plates in the Presence of Weak Nonlinearities

While the mathematical foundation for modal analysis of continuous systems has long been established, flexible structures have become increasingly widespread and developing tools for understanding their mechanics has become increasingly important. Cantilever beams and plates, in particular, have been extensively studied due to their practical importance as approximations of more complex structures. The focus of this thesis is on understanding the dynamics of vibrating cantilever beams and plates through analytical and experimental investigation. Various models for the mechanics of these structures, of varying physical fidelity, are described and compared. A fiber optic sensing system is utilized to experimentally acquire distributed strain measurements, which are used to estimate the mode shapes and natural frequencies for the cantilever structures. These experimental estimates are compared with analytical and numerical solutions corresponding to the models previously introduced. Next, a detailed case study is described which demonstrates the nonlinear response in a cantilever beam\u27s first mode and implements an empirical procedure for estimating a variable parameter model which accounts for its varying system parameters. By implementing the described identification methods, parameter variations due to a system\u27s nonlinear response are included in a modified linear model and significantly reduce the errors in predicted response. Based on this research, methods to experimentally estimate and validate the mode shapes and system parameters can be implemented for other beam- and plate-like structures

Potential of FBG sensors for vibration control in smart structures

The large use of lightweight structures has emphasized the need to reduce undesired vibrations which can compromise the integrity and the safety of flexible structures. The advancements in materials technology have made available a new generation of materials regarded as smart. Thanks to the results obtained in this field, many research are focusing on the study of intelligent structures, able to modify their mechanical properties. Composite materials are interesting in the construction of smart structures, thanks to their high mechanical properties which allow to obtain lightweight structures with high resistance and due to the possibility of embedding sensors and actuators inside the structure. Among all, optical fiber sensors are widely used in the development of smart structures. However, while they are usually considered for structural health monitoring, this paper proposes their use in active control application. A structure made of carbon fiber with Fiber Bragg Grating (FBG) sensors and piezoelectric actuators is able to self-sense its state of vibration and to provide control forces to reduce it. The peculiarity of this structure is represented by the possibility to monitor a large number of sensors (to approximate distributed measurements), suitable for physical feedback or modal control. The experimental tests carried out allow to investigate the effectiveness of these setup in the active vibration control and to evaluate the limits of this technology