DESIGN OF LINEAR ACTUATORS BASED ON COMPLIANT MULTI-STABLE STRUCTURES

Light-weight, compact actuators capable of delivering large linear stroke based compliant structures offer interesting potential for adaptive structures and robotics given their capability to carry a load and to be geometrically scalable. Furthermore, the utilization of compliant structures replacing mechanisms and moving parts offers the possibility for reducing losses due to friction. Solid state actuators have been proposed as a means to attain such capabilities with particular success for smart systems based on piezoelectric, shape memory, and electroactive polymer materials. Despite this success, smart material systems do not concurrently offer large strokes, high blocking force and wide response bandwidth. Recently, a new class of multi-stable structures that generate large linear strokes from twisting have been introduced. Furthermore, the snap-through action characterizing the changes between stable states of multi-stable systems has been shown to be a viable mechanism for inducing controlled actuation at high rates. In this paper, the novel design of a linear actuator adapted from twisting multi-stable structures is tailored to have geometric instability that is exploited to achieve large axial strokes under the action of small deformations from a single structural component. Finite element modeling is used for analysis of the structure, where parameter studies of composite layup and structure geometry are conducted to adjust equilibrium positions and stroke length of the actuator design. Different smart actuator topologies demonstrating the ability for compliant multi-stable systems are coupled with smart materials to produce large linear deformations and wide actuation bandwidth. The herein presented unconventional design serves as a useful linear actuator; as well as a load carrying component. The introduced multi-functional light-weight load-carrying actuators are relevant for aerospace and robotics applications.