STRV Cryocooler Tip Motion Suppression

Abstract

The Space Technology Research Vehicle (STRV-1b), which was launched aboard an Ariane-4 on June 17, 1994, has a cryocooler vibration suppression experiment on board doing motion suppression of the tip of the coldfinger. STRV-1b is a bread box sized satellite containing a variety of technology demonstrations in addition to the vibration suppression experiment. To meet stringent power, weight, and space constraints, the vibration experiment uses a tiny 1/5-watt 80K Texas Instruments tactical Stirling cooler. Two different tip-motion cancellation techniques are implemented in the experiment: 1) an applique ceramic stretching the coldfinger; and 2) three commercial low voltage piezo-electric translators that move the cryocooler supports. Motion of the coldfinger tip is measured in three dimensions to 10 nanometers using commercial eddy-current transducers. Two different control systems are used: 1) an analog control system using a bandpass filter to suppress the cooler drive fundamental, and 2) a feed forward steady-state harmonic analyzer that continuously updates a command signal to each actuator.