This paper presents approximate model based sliding and integral control for an arc-shaped Shape Memory Alloy ( SMA ) actuator. This actuator uses SMA wire which is knit in an arc shape. Due to this arc shape, when heated, this arc shaped SMA actuator produces rotary motion while recovering its shape. Thus, rotational motion is harnessed without any mechanical attachments such as disk or gear. Further, the actuator behavior shows that we can harness motion below the austenite start temperature due to its unique mechanical shape. To model this unique behavior, we have used nonlinear autoregressive exogenous ( ARX ) modeling technique to model the behavior of the actuator. It is difficult to model the actuator using conventional one dimensional constitutive modeling technique because the applied forces on SMA wire are multidimensional. Next, to control rotational motion of the actuator, we have developed proportional-integral-derivative ( PID ), sliding mode and integral sliding mode controllers. PID controller is model-free controller, whereas sliding and integral sliding mode controllers assume upper limits of SMA dynamics. These controllers are experimentally evaluated with input, output and combined input-output disturbances. Results indicate that integral sliding mode controller outperforms the aforementioned controllers in terms of tracking accuracy and controller effort.
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