Modelling and gain scheduled control of shape memory alloy actuators

This paper describes a gain-scheduled controller for a shape memory alloy (SMA) actuator. For accurate control of an SMA actuator, it is important to develop a precise model for the SMA. A model has been proposed based on concepts from physics. The equations include Joules heating - convectional cooling to explain the dynamics of temperature, Fermi-Dirac statistics to explain the variation of mole fraction with temperature, and a stress-strain constitutive equation to relate changes in mole fraction and temperature to changes in stress and strain of the SMA. This model is then used to develop a gain-scheduled controller to control the strain in the SMA. Simulation and experimental results show fast and accurate control of the strain in the SMA actuator