Frequency-domain control design for shape memory alloy actuators

This contribution provides a model-based control design approach for shape memory alloy (SMA) actuators with position feedback. The electro-thermo-mechanical transmission behavior is described by linearized partial transfer functions. The system transfer function of a SMA actuator is characterized by the thermal time constant and the mechanical resonance frequency. Additionally, the frequency response is measured based on the analysis of correlation, and the identified model shows closeness to the measured results. The control design is performed in the frequency domain by using Bode plots in order to meet the stability criterion of Nyquist. The objective is mainly to overcome the problem of mechanical resonance by a correction transfer function. The PI-controlled SMA actuator shows fast actuation and stable controllability.