Dynamic behavior of smart thin-walled composite structures

This doctoral dissertation deals with optimization and active vibration suppression of smart thin-walled composite structures by using piezoelectric actuators and sensors. Mathematical model of plate composite structure with integrated actuators and sensors is developed. The problem is formulated using the finite element method based on the third order shear deformation theory. Constitutive equations and the strain - displacement relations are linear. In further work, the problem of determination of optimal sizes, positions and orientations of actuator – sensor pairs are presented and, after that, objective functions and constraints are defined. Also, the integration of finite element method and particle swarm optimization is performed and using defined optimization criteria, the optimization of sizes, positions and orientations of five actuator – sensor pairs on square cantilever composite is performed. The cantilever composite plates have following orientation of layers: (90°/0°/90°/0°)S, (90°/0°/90°/0°/90°/0°/90°/0°) i (45°/-45°/45°/-45°/45°/-45°/45°/-45°). Actuators and sensors considered in dissertation are collocated. In order to overcome problems during conventional control algorithm synthesis which occur due to vibration’s stochastic nature, the optimized self-tuning fuzzy logic controller is presented. The main idea of proposed controller is amplitude monitoring and self-tuning of input scaling factors based on amplitude. Membership functions are parameterized and optimal combination of parameters are found by using the particle swarm optimization method based on previously defined optimization criteria. Two inference methods are considered: the Mamdani and zero-order Takagi-Sugeno-Kang inference methods. Numerical studies are provided for composite cantilever beam and composite cantilever plate for both free and forced vibrations. Single-input single-output (SISO) configuration is considered for the cantilever beam and multiple-input multiple-output (MIMO) configuration is considered for cantilever plate. Comparisons of control performances for these two types of inference methods as well as optimized self-tuning fuzzy logic controller with linear quadratic regulator are performed. Ova doktorska disertacija bavi se optimizacijom i aktivnim prigušenjem vibracija pametnih tankozidnih kompozitnih struktura pomoću piezoelektričnih aktuatora i senzora. Razvijen je matematički model pločaste kompozitne strukture sa integrisanim aktuatorima i senzorima.