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Tracking Control of Shape Memory Alloy Flexible Actuators Using Dynamic Surface Controller with Approximate Duhem Model*

As a class of flexible function materials, shape memory alloys (SMAs) can produce the deformation and recovery tension with the change of the phases caused by the temperature difference, fulfilling the conversion of thermal energy and mechanical energy bidirectionally. The flexible actuating characteristics of the SMA have gradually been applied in the fields of bionic robots and aerospace. However, there are strong saturated hysteresis nonlinearities existing between the input-output of the SMA actuators due to the internal materials properties, causing the output accuracy to descend seriously, even instability for some special cases. To overcome the negative effects from the saturated hysteresis, an adaptive dynamic surface controller (ADSC) is proposed in this paper, where the internal hysteresis is modeled by an approximate Duhem model. The designed controller can ensure the output performance of the SMA actuator, and the tracking experiment is conducted to illustrate the effectiveness of the proposed control method.