This thesis presents an initial investigation into Active Damage Control (AD C) using Artificial Intelligence (AI). AI can alleviate the sometimes complicated task of modelling the system and also provides an adaptable solution process. The two research areas of ADC, damage identification and damage control, are studied in separate investigations. An AI technique called "rule induction" is used for the damage identification study. Velocity data from three plates (one without damage, one with damage at the center, and one with damage at the edge) are acquired using a laser data acquisition system. A set of rules is then induced from these data which accurately identifies which plates have damage and where the damage is located. With regard to the damage control, a real-time, machine-learning technique called "BOXES" is used to locally control the vibration of various systems by identifying their vibrational patterns. Using this technique, it is shown that the computer successfully learns an effective control law for various simulations using its trials and failures as the only learning information. It is also seen that the learning algorithm is somewhat less effective when experimentally applying this method to a pin-pin, aluminum beam. A discussion of possible improvements are presented in the future work section. / Master of Science

Graduation date: 1996

Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographical references (p. 224-227).

A modern control theory formulation of Active Structural Acoustic Control (ASAC) of simple structures radiating acoustic energy into light or heavy fluid mediums is discussed in this dissertation. ASAC of a baffled, simply-supported plate subject to mechanical disturbances is investigated. For the case of light fluid loading, a finite element modelling approach is used to extend previous ASAC design methods. Vibration and acoustic controllers are designed for the plate. Comparison of the controller performance shows distinct advantages of the ASAC method for minimizing radiated acoustic power. A novel approach to the modelling of the heavy fluid-loaded plate is developed here. Augmenting structural and acoustic dynamics using state vector formalism allows the design of both vibration and ASAC controllers for the fluid-loaded plate. This modern control approach to active structural acoustic control is unique in its ability to suppress both persistent and transient disturbances on a plate in a heavy fluid. Numerical simulations of the open-loop and closed-loop plate response are provided to support the theoretical developments. / Ph. D.

A crucial element of a smart structure is the computer system that processes data collected by sensors and determines an appropriate response. Multicomputers possess many capabilities that are required in computer systems for smart structures. This research examines the implementation and use of multicomputers for distributed processing in smart structures. The research begins by examining previous research and showing the suitability of multicomputers for distributed processing in smart structures. Appropriate cost and performance metrics for evaluating multicomputer architectures are defined. The cost metrics are the number of processors, the number of communication links, and the length of fiber required to embed the network in the structure. The performance measures are the algorithm cycle time and the mean and standard deviation of message latency in the network. The scalability of these metrics is also examined. A key issue in the examination of these metrics is how their application to smart structures differs from their application in traditional systems. The research continues by using a three-processor testbed network to identify general characteristics of algorithms that may be executed in smart structures. The testbed network uses fiber optic sensing, the MIL-STD-1773 communication protocol, and several different assignments for partitioning the necessary computations among the processing nodes to determine the shape of a triangular structure. The effects of math coprocessing on performance and the viability of hybrid links, in which a single optical fiber is used simultaneously for sensing and communication, are also demonstrated. Simulation models of a damage detection, location, and estimation algorithm implemented in VHDL, a hardware description language, are used to examine and compare the performance of multicomputer interconnection network topologies. The topologies examined in this research are a binary hypercube, a custom planar topology, and a custom hierarchical topology. The ability of hierarchical architectures to limit cost while providing acceptable performance is demonstrated. The simulations also examine the effects of background message traffic and the ratio of communication time to processing time on performance. The combined results of the testbed and simulation experiments show the importance of process assignment and scheduling. / Ph. D.