Design and Experimental Testing of a NiTi-based, High Frequency, Centripetal Multiple Actuator

The purpose of this work is to analyze complex systems with multiple SMA actuators working at frequencies greater than 1 Hz, which are higher than those typical of NiTi actuators. In particular, we show the design, the development and the testing of a peristaltic experimental rig actuated by multiple shape-memory NiTi wires. Each centripetal actuator is designed to radially and cyclically shrink a compliant silicone pipe containing fluid. The actuation device converts a linear contraction of a heated SMA wire into a radial displacement: four rigid, aluminum-made circular sectors are placed along the pipe circumference and provide the required NiTi wire housing. The aluminum assembly acts as geometrical amplifier of the wire contraction and as heat sink required to dissipate the thermal energy of the wire during the cooling phase. The NiTi re-arm force is provided by the fluid pressure inside the pipe. The positioning of 200 of this SMA devices along the external surface of the compliant test section, has allowed to create sinusoidal waves of wall-normal deformation traveling along the pipe. The pipe wall displacement is monitored by means of laser transducers. The performance of all the actuators is analyzed and compared with the authority of the single actuator.