Kourtney Kehr was born in Kahului, Maui and will be a junior studying Mechanical Engineering in the fall at the University of Colorado Boulder. Her academic interests include space travel and she hopes to become an astronaut one day in the future. She currently works in the physics lab on campus where she is able to put her engineering knowledge to practical use. In the lab, she is in charge of improving demos and fixing any other issues that may arise. She is a member of the American Society of Mechanical Engineers and the Society for Women Engineers. Kourtney enjoys being outdoors, whether she is snowboarding, hiking, or just lounging outside with her dog, Tater.

Project Title: Determining the Behavior of Piezo-Ceramic Actuators and Finding Errors in Mirror Configurations for an Aperture Partitioning Optic

Project Site: Air Force Research Laboratory

Mentors: Dr. Jeremy Bos, Dr. Steven Griffin, and Dr. Brandoch Calef

Project Abstract: Atmospheric turbulence and sky brightness degrade satellite imagery collected during daytime telescope observations. To improve image quality, an aperture partitioning optic is being developed by The Boeing Company. The device consists of four articulating mirrors whose positions are adjusted by controlling the voltages applied to piezo-ceramic actuators positioned behind each mirror. The purpose of this project was to first determine the behavior of the actuators and then to develop a solution for detecting error in the mirror configurations. Using a high voltage amplifier, voltage was applied to a piezo-ceramic stack whose deformation or displacement was measured using a laser displacement sensor. The data collected in this experiment, using a CoCo signal analyzer, was then plotted in Octave in order to determine and observe the behavior of the piezo-ceramic actuators. They behaved according to a hysteresis loop, as expected. The hysteresis loop can now be characterized, and from this characterization, control voltages for each desired displacement can be attained. The method of characterizing the hysteresis loop is more complicated than closed loop positioning but has better resolution. Octave was used to simulate the image produced by the separate mirrors in order to determine piston error in the mirror configurations. It was observed that the piston error could be measured using the focal plane data so that it can then be corrected by adjusting the actuators. With the behavior of the piezo ceramic actuators determined and a method found for detecting error in the mirror configurations, the optic device can be used effectively and efficiently to improve the quality of daylight imagery of satellites.