In this paper, a digital regulator is designed and experimentally implemented for a flexible beam type structure containing piezoelectric sensors and actuators by using optimal control design techniques. The controller consists of a linear quadratic regulator with a state estimator, namely a Kalman observer. The structure is a cantilever beam containing a set of sensor/actuator PVDF/PZT ceramic piezoelectric patches bonded to the beam surface at the optimal location obtained for the first three vibration modes. The equations of motion of the beam are developed by using the assumed modes technique for flexible structures in infinite-dimensional models. This paper uses a method of minimizing the effect of the removed higher order modes on the low frequency dynamics of the truncated model by adding a zero frequency term to the low order model of the system. A measure of the controllability and observability of the system based on the modal cost function for flexible structures containing piezoelectric elements (intelligent structures) is used. The observability and controllability measures are determined especially to guide the placement of sensors and actuators, respectively. The experimental and numerical transfer functions are adjusted by using an optimization procedure. Experimental results illustrate the optimal control design of a cantilever beam structure.
This paper presents the numerical modeling of a plate structure containing bonded piezoelectric material. Hamilton's principle is employed to derive the finite element equations using the mechanical energy of the structure and the electrical energy of the piezoelectric material. Then, a numerical model is developed based on Kirchhoff's plate theory. A computational program is implemented for analyzing the static and dynamic behavior of composite plates with piezoelectric layers symmetrically bonded to the top and bottom surfaces. A set of numerical simulations is performed and the results are compared with those from analytical formulation available in the literature and with software ANSYS®
Este trabalho apresenta os resultados de pesquisa desenvolvida sobre a construção e utilização de barragens subterrâneas no Nordeste do Brasil, em particular no Estado de Pernambuco, onde há maior incidência desse tipo de obra. A partir da identificação de 500 barragens implantadas, foram selecionadas 151 para uma primeira inspeção, distribuídas espacialmente em áreas com características diferentes e implantadas sob óticas distintas (decisão governamental, pesquisa, ação de ONGs, diferentes níveis de participação da comunidade). Após essa primeira avaliação, foi selecionada uma amostra menor de 50 barragens para levantamento mais detalhado em campo, tanto dos aspectos técnicos como sócioeconômicos. As causas de sucesso e insucesso, os cuidados a serem tomados e as perspectivas para adoção desse tipo de obra em larga escala são discutidos neste artigo.
This paper presents design, implementation and experimental results of active vibration control of a truss structure using a pair of piezoelectric ceramic stack actuators. To reduce the vibrations caused by an impulse force, two active strut members are installed along a vertical of the base bay of the truss. The active strut element consists of a piezoelectric ceramic actuator stack, a force transducer and mechanical interfaces. A self-organizing fuzzy controller (SOFC) is designed to suppress vibration of the truss. The SOFC, which uses the input and output history in its fuzzy rules, is designed to maximize modal damping of a constructed truss structure. Experimental results illustrate that the active piezoceramic strut actuators and the SOFC can effectively reduce vibration of the truss.
This paper presents a simple feedback methodology that uses second order filters to control narrowband resonant and non-resonant vibration of a structural system. In particular, a single degree-of-freedom system is studied throughout the paper. The idea of the methodology is based on the fact that direct feedback is effective for in-phase vibration control. Thus, the position, velocity and acceleration are respectively fed back to control the low, resonant and high frequency vibration of the system. Each of these is passed through a band pass filter of second order that is inserted to extract and feed back the inphase signal component only. This is called narrowband feedback. It is demonstrated with experiments that narrowband feedback is useful for narrowband control of resonant and non-resonant vibration.
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