Exaggerated actuation and bearing-free rotational mobility in smart

Abstract

The implementation of smart materials (shape-memory alloys (SMA) or piezoceramics) as integral actuating devices for single degree-of-freedom (DOF) hinges, thereby providing mobility as well as actuation to a wide range of mechanisms used in industrial, automotive and aircraft systems. A single DOF hinge is used in which smart materials are used both for actuation and for performance enhancement. The hinge consists of a tang and clevis, two conical inserts, one push block, one bolt and nut, and two washers. Assembly takes place by first putting the push block inside the clevis and putting the tang in place, then inserting the cones, inserting a bolt in the cones and finally tightening the bolt in this arrangement together with the nut to a specified torque. The amount of torque applied is related to the amount of preload in the undisturbed configuration of the hinge and the expansion of the conical inserts required to initiate rotation of the hinge. The smart material of the conical inserts is used to provide rotational mobility to the hinge. Applying a current causes the conical inserts, which are fabricated out of a smart material, to expand, thereby creating a gap between the conical inserts and the clevis. The existence of the free-play caused by the gap allows the clevis to rotate about the hinge's rotational axis. Once the hinge rotation is complete, the free-play in the hinge is eliminated by restoring the smart material of the conical inserts to the original (undisturbed) configuration, thereby pre-loading the hinge components.