Static and Dynamic Testing of Large-Amplitude Rotary Induced-Strain (LARIS Mk 2) Actuator

Document Type


Subject Area(s)

Physics, Mechanical, Engineering


A new concept for obtaining large-amplitude rotary displacements from small linear displacements generated by induced-strain active material stacks is considered. The concept utilizes the theory of twist-warping coupling in thin-wall open tubes. A large-displacement induced-strain rotary actuator, LARIS Mk 2, was built and tested under static and dynamic conditions. A rotary displacement of 60 was measured over a 0-50 Hz frequency range. The frequency response was found to be flat up to 40 Hz, and then increasing in the 40-50 Hz frequency range.

The theoretical development of the torsional vibration response for the LARIS Mk 2 actuator is also given. The derivation is performed in a general format for a body with distributed elastic and inertia parameters, and with generic boundary conditions consisting of root stiffness and tip angular deflection. The results of this theoretical analysis are confirmed by experimental measurements. The theory presented is versatile and can be used for the analysis of other torsional vibration devices with specific root and tip boundary conditions.

This LARIS concept presented in this paper can be successfully used in a series of aerospace and mechanical engineering applications, as for example in the actuation of adaptive control surfaces for aircraft wings and helicopter blades, or as rotary vane actuators in the control of turbomachinery exhaust flow for active reduction of turbulence, vibrations, and noise.