Application of shape memory alloy actuators for flexure control: theory and experiments

This paper presents a nonlinear control scheme for deflection control of a flexible beam using shape memory alloy (SMAs) actuators. These actuators possess interesting properties in terms of force generation capacity, possibility of miniaturization, and power consumption. However, their use in precision applications is hampered by undesirable characteristics, such as nonlinearities, hysteresis, extreme temperature dependencies, and slow response. By taking into account the nonlinear and thermal characteristics, a control scheme based on partial feedback linearization is developed to regulate the forces exerted by a differential SMA actuator pair attached to a flexible beam. The regulated force corresponds to a specific position of the flexible beam; hence, regulating the force results in position regulation. Using a Lyapunov stability analysis, qualitative guidelines are provided for selecting controller gain parameters. Furthermore, performance of the developed control scheme is tested experimentally on a laboratory testbed.