Actuators are a critical driver of all the mechanisms used in space, and improvements of their operation mechanism enhance mission capabilities. The disclosed invention is a new type of actuator that simultaneously drives dual mechanisms (e.g., rotors, wheels, etc.) at opposite sides of a piezoelectric stack using the generated vibrations. The actuator consists of dual-sided horns and is capable of operating ratcheting mechanisms through walls.
The problem that was addressed is the need to drive miniature vehicles through walls while operating along a single axis and using a single motor. The use of more than one actuator that drives each of the two wheels on the opposite sides, or the use of a gear train, requires greater mass and complexity due to the need to use motors on each wheel and have additional drive electronics.
The actuator was designed using a piezoelectric stack as a transducer to produce vibrations, and rather than a horn on one side and a backing on the other, the stainless steel backing used for pre-stressing the stack was replaced with a second horn. Thus, the prestress backing was converted to an additional actuator on the other side of the transducer. Further, the dual-horn actuator was designed based on the piezo-ratcheting motor, providing actuation on both sides of the piezoelectric stack. This design allows rotation of wheels with no moving parts besides the rotors.
The two horns are not made identical, allowing steering capability where the use of different driving frequencies leads to changing the relative speed of the wheels along the drive axis. Also, the horns are designed to be sufficiently similar to allow operating them well within the same range of frequencies, while causing one to outperform the other. By controlling the frequency, the direction of travel of a rover driven by these horns is controlled. The piezoelectric stack was made of lead zirconate titanate (PZT) with multiple steel backing plates and clamping screws.
This work was done by Yoseph Bar-Cohen, Stewart Sherrit, Xiaoqi Bao, Mircea Badescu, Phillip E. Walkemeyer, and Grayson T. Adams of Caltech for NASA’s Jet Propulsion Laboratory. NASA is seeking partners to further develop this technology through joint cooperative research and development. For more information about this technology and to explore opportunities, please contact Dan Broderick at