Development of a shape memory alloy actuated biomimetic hydrofoil

Abstract

The development of an active biomimetic hydrofoil that utilizes Shape Memory Alloy (SMA) actuator technology is presented herein. This work describes the design and testing of two experimental hydrofoils. The first model had a trailing edge flap deflected by a pair of SMA wires and demonstrated the feasibility of using SMAs in an aquatic environment. The second hydrofoil had a skeletal structure similar to a fish with internal SMA muscles. This hydrofoil was able to deform to several shapes mimicking aquatic animals with controlled oscillation frequencies of up to 1 Hz, with 1/2 Hz oscillation producing the largest useful amplitudes. Measurable force was generated when the biomimetic hydrofoil was defected underwater. The magnitude of the force was limited by the high flexibility of the tail. An adaptive model for control of SMA actuators is also presented. The control method combines predetermined open-loop modeling with an error feedback for updating of the hysteresis model. The model was capable of tracking a single SMA wire up to 20 Hz, but had trouble simultaneously controlling six wires.