Design Of A Shape Control System For Shape Memory Alloy

As one kind of new type smart materials, shape memory alloy (SMA) which possesses excellent shape memory effect and superelasticity is widely applied in aerospace, industry, and bio-medical technology, etc. For example, it is mainly used in damper design, structural deformation control, smart composites, and memory element, etc. It requires the designers that they should have an in-depth understanding and knowledge of SMA constitutive equation, but it is worth noting that the properties of SMA have complex relationships to material proportion, percentage of martensite, stress state, and environmental temperature which present a highly nonlinear, so it is still different to establish a simple and accurate constitutive equation, especially in multi-dimensional state.In the present paper, the relationships among strain, temperature, and highest point displacement of SMA band were gained by experiment, and the shape of SMA band was controlled by the relationships. This research is mainly focused on the following parts.First of all, the two-way shape memory effect of SMA was attained by training after the memory effect of SMA mechanism was mastered, the training result was good.Secondly, the temperature loading unit was designed. According to the thermal effect of current, the SMA band was heated by resistance wires which were loaded voltage.Thirdly, the signal acquisition circuit was designed. Signal acquisition includes temperature acquisition, strain acquisition, and displacement acquisition. In this paper, the temperature acquisition circuit was designed by thermoelectric couple and the AD595 chip. The strain acquisition circuit and displacement acquisition circuit were achieved by strain measurement technology and laser displacement sensor, respectively. What’s more, the data are attained by the LabVIEW measurement system.And finally, the shape of SMA band was controlled by the physical relations which were measured in experiment, in which the ATmega16 chip, an AVR MCU, was used as the main control unit.