Design of A Fluid Elastic Actuator with Application to Structure Control

摘要

An elastically deformable pressure vessel is used as an actuator. The internalpressure is controlled hydraulically via force applied to an external bellows. The resulting elongation of the vessel is a linear function of the input force, and depends on the physical properties of the vessel, fluid, and bellows. The design includes an orifice through which fluid flows, adding damping to the actuator. Mathematical models of the actuator are developed which relate performance of the actuator to its geometry and material properties. A static analysis yields the linear relationship between the commanded input force and the resulting elongation of the vessel. A model of the passive (no input force) response of the actuator indicates it will act as a passive damper. The active response (application of a dynamic input force yielding a dynamic elongation) is limited in frequency by the orifice damping. Strategies for optimizing the actuator size and material properties are developed from the models. Actuators manufactured with differing materials and fluids were tested. The static results are linear and matched the analysis. The passive results and the model predictions confirm that the configuration of the actuators, as built, is poor for passive damping. The correlation between the model and active experiments is excellent. Actuation bandwidth is shown to be selectable by selecting orifice size. Tailoring the material properties of the vessel by the use of optimally designed composite laminates results in a factor of two improvement in the performance. The actuator is useful for structural control. It's performance is comparable to other available actuators, it is constructed of off-the-shelf hardware, and it has the advantages of a built-in frequency limit and easily customizable pe.