SMA Actuator Priming using Resistance Feedback

[摘要] Shape memory alloys (SMAs) are a group of alloys that demonstrate the uniqueability of returning back to a previously defined shape or size if subjected to theappropriate thermal procedure. They have been implemented as actuators in awide range of applications spanning severalfields such as robotics, aeronautics,automotive and even in medicine. Several controllers, linear and nonlinear, havebeen designed to control these actuators. However, controlling these actuators is nosimple task as they are highly nonlinear due to the hysteresis inherent in them. Infact, their control depends on two important factors: the thermal conditions theyare subjected to and the stress applied to them. The former can be further dividedinto air flow and ambient temperatures. These thermal conditions determine theamount of power needed to heat the SMA wire. In the SMA data sheets, manufacturers specify what they refer to as the ;;safe current;; which is the maximumcurrent value that can be applied to the SMA wire indefinitely without burning it.However, they specify this current value at room temperature and under certainconvection conditions. In the work presented here, the focus was the control ofSMA actuators under different ambient temperatures. Thus, in this research, themain goal was to design and implement a controller that will actuate, or contract,the SMA wire in approximately the same amount of time regardless of the ambienttemperatures with a fixed load applied to it.

[发布机构] University of Waterloo

[关键词] Electrical and Computer Engineering