Plataforma para análise comportamental de atuadores de ligas com memória de forma e para o controle de deformação de uma barra flexível.

Abstract

In this dissertation, the development of an experimental platform, containing a simply supported flexible aluminum beam, strain-gauges and SMA wires as force actuators, to analyze the behavior of the SMA wires of NiTi (Nickel-Titanium) and of NiTiCu (Nickel- Titanium-Copper) and, in addition, to accomplish the deformation control in the beam. In the platform for analysis of the behavior of wires are used strain-gauges, a LVDT (Lineal Variable Differential Transducer) and a micro-thermocouple to measure respectively the deformation and the deflexion in the beam , as well as the temperature in the SMA wires. For the data acquisition, it developed a code in Visual Basic a spreadsheet to accomplish the communication with the measurement instruments with interface GPIB (General Purpose Interface Bus). In the control platform the deformation control in the beam, the data acquisition and control are implemented with an ADuC microcontroller based card. The system answer in open-loop was used to identify the mathematical model of the system, using the technique of direct tunning to find the appropriate controller. The PI controller have been used to control the deformation in the beam for different types of reference signals, varying the frequencies to be able to observe the bandwidth that the system answers. The microcontroller card is connected to the PC running LabVIEW software to visualize the measurements in a graphic user interface. The analysis platform allowed to determine a no-lineal and lineal relationship, as well as the appearance of a hysteresis in the behavior of the SMA wires. With the control platform, it observed that the deformation in the beam can be controlled by a PI controller, obtaining a deformation value through an electric voltage source that it makes to pass an electric current in the SMA thread, accomplishing its heating for effect Joule.