Aplicação de métodos de controle em uma estrutura ativa de viga engastada com atuador de liga com memória de forma.

Abstract

According to recent studies in the field of smart structures, the integrated use of sensors, actuators and controllers, could enable any system to respond as controlled to external excitations, compensating effects that would take the response amplitude levels away from acceptable. It an objective of this work to control the equilibrium position of a cantilever beam, using samples of SMA as actuators, strain gauges as sensors, and using different control techniques. For this overview, a studies platform was used, where a steel beam is simply riveted to a column, and secure with the SMA sample at the opposite end. Attached on the top and bottom faces of this beam, we have unidirectional electrical resistance strain gages, so that we can acquire data from the beam deformation. At the SMA both ends, electrical terminals are connected in a way that is possible to provide the signal for action. To generate this signal operation, it was necessary to design a control system. We designed and implemented two control techniques for this structure, making the acting of the alloy by a voltage source and current source, and evaluate which one has better viability to control this type of structure. The criteria to be used for comparison are the error rates of each technique, and frequency response of the same. As controller, the LabView virtual instrumentation software was used running on a microcomputer equipped with a PCI-Express card manufactured by National Instruments, model PCI-6036e, which must be connected to the platform by means of a block model BNC-2110. So the order is also working to develop a virtual instrument to implement the proposed control techniques. It was found, based on graphical results and performance indices calculated that the control achieved with current source showed better results compared with the control voltage source. Similarly, it was found that tuning the controller using the root locus obtained better results than a tune done automatically by LabView. Still, comparative tests were made between an actuator in the form of wire with circular cross section, and an actuator wire rod or tape, where the cross section is rectangular in shape.