Sensorless Control of SMA Using Seebeck Voltage

Active research of SMA has presented the measurement of thermoelectric properties as a useful and a potential tool in the study of phase transformations. The Seebeck coefficient is sensitive to the martensitic transformation behavior of SMA and can potentially be used to determine the state of Martensitic transformation of a SMA. The combination of Shape Memory Alloy having a positive Seebeck coefficient and Constantan with a negative Seebeck coefficient (−35 μV/K) is a suitable thermocouple pair to measure temperature. This relation along with the displacement characteristic provides a feasible method to determine the state of SMA at any point during Martensitic phase transformation. Future work aims at utilizing the thermoelectric relation of the SMA-Constantan thermocouple as a feedback variable in replacing external sensor.