Active Reduction of Cryocooler Induced Vibrations Using Smart Materials and Adaptive Control

Kurzfassung

Future space mission requirements on high precision structures get continuously more challenging with respect to structural accuracy. With classical structural technology coming to ist limits, adaptive structure technology offers the potential to solve a variety of quasistatic and dynamic problems. With respect to the dynamic excitation of sensitive equipment, mechanical cryocooler systems, which are often used in aerospace applications to cool specific equipment to its cryogenic working temperature, represent a typical disturbance source within a satellite. They either directly excite vibrations at the attached cryogenic equipment or indirectly by transferring the disturbance energy via the generally poorly damped interface structures to finally excite remote instruments. One approach to compensate for such vibrations utilizing adaptive structure technologies is presented in this paper. Within a typical small satellite project, two infrared detectors have to be cooled by two independent miniature mechanical cryocoolers. The coolers’ operation induce critical vibrations at the detectors, leading to a severe reduction of the quality of the scientific results. Opposite alignment of the coolers is impractical due to mission constraints. DLR developed an add-on, long life adaptive vibration compensation system that removes critical vibratory energy and works without launch locking devices. The system has been designed and qualified for general space applications on material and system level. Functional demonstration proved a vibration reduction by 53 dB, representin g a significant improvement of the general acceptance specifications for residual cryocooler vibration force levels for future missions. Long life testing showed no performance degradation after more than lo* cycles. The modular stand-alone system design offers high potential for a simple technology transfer to other space and non-space applications.