MODELING AND L2-STABILITY OF A SHAPE-MEMORY ALLOY POSITION CONTROL-SYSTEM

Shape memory alloys (SMA's) are inherently nonlinear devices exhibitin g significant hysteresis in their stress-strain-temperature characteri stic, As a consequence most SMA actuator systems presented in the lite rature employ some form of proportional-integral-derivative (PID) or p ulse-width modulated (PWM) control. Unfortunately, due to the hysteres is of the SMA, the theoretical stability of these systems has been lar gely ignored. This paper extends tl;e work of Ikuta el al. to arrive a t a new model of an SMA actuator. The key feature of the model is its ability to model minor hysteresis loops. The model is suitable for com puter simulation, even of closed-loop control systems, as well as cont rol system analysis. Indeed, the model is used to prove the L-2-stabil ity of a position control system.