Swing Suppression Control of a Variable Length Link Using Shape Memory Alloy Actuator

This paper concerns a swing suppression control of a variable length link utilizing the length change of a shape memory alloy (SMA) wire. In general, SMA actuators exhibit hysteresis characteristic, which affects the control of application using the length change of SMA actuators. To suppress the sway angle of a variable length pendulum efficiently, the feedback control system to make the length of the SMA wire track to the reference input which represents the desired length of the link is designed. In this paper, a SMA actuator model which consists of thermal model and hysteresis model is represented. A SMA actuator is considered as a controlled object, an operator theoretic control method by using the SMA actuator model is proposed based on right coprime factorization approach. The designed nonlinear feedback control system is compensated the hysteresis effect and the slow response of the SMA actuator. As a stabilization control method for the variable length link, the energy-based control approach using the kinetic energy of rotation and the potential energy of the link is employed for the purpose of obtaining the reference input of the feedback system. From the simulation results, the effectiveness of the proposed method to suppress the sway angle of a variable length link by using a SMA actuator is illustrated.