Abstract
Modern infrared imagers often rely on low Size, Weight and Power split Stirling linear cryocoolers comprised of side-by-side packed compressor and expander units fixedly mounted upon a common frame and interconnected by the configurable transfer line. Imbalanced reciprocation of moving assemblies generates vibration export in the form of tonal force couple producing angular and translational dynamic responses. Resulting line of sight jitter and dynamic defocusing may affect the image quality. The authors explore the concept of multimodal tuned dynamic absorber, the translational and tilting modal frequencies of which are essentially matched to the driving frequency. Dynamic analysis and full-scale testing show that the dynamic reactions (forces and moments) produced by such a device may effectively attenuate both translational and angular components of cryocooler-induced vibration.
Highlights
Split Stirling linear low Size, Weight and Power (SWAP) cryocoolers find wide use in infrared (IR) imagers. Such cryocooler usually comprise electro-dynamically actuated linear pressure wave generator and pneumatically actuated resonant expander, which are fixedly mounted upon a common frame and interconnected by a configurable transfer line [1]
A force couple generated by an imbalanced reciprocation of moving assemblies inside both compressor and expander units produces the cryocooler induced vibration comprising angular and translational components resulting in line of sight jitter and/or dynamic defocusing
Manufacturers of low SWAP split Stirling linear cryocoolers featuring singlepiston compressors and Integrated Dewar Detector Cooler Assemblies (IDDCA), such as Ricor, AIM and SCD [10,11,12,13,14,15,16,17,18,19,20,21] developed and fielded new models of optional tuned dynamic absorber (TDA) intended for use in vibration sensitive lightweight and flexibly mounted, hand-held and gyro-stabilized payloads
Summary
Split Stirling linear low Size, Weight and Power (SWAP) cryocoolers find wide use in infrared (IR) imagers. Manufacturers of low SWAP split Stirling linear cryocoolers featuring singlepiston compressors and Integrated Dewar Detector Cooler Assemblies (IDDCA), such as Ricor, AIM and SCD [10,11,12,13,14,15,16,17,18,19,20,21] developed and fielded new models of optional TDA intended for use in vibration sensitive lightweight and flexibly mounted, hand-held and gyro-stabilized payloads Such TDA are made in the form of single-degree-of-freedom (SDOF) resonator, where the frequencies of "parasitic" modes (tilting, in-plane translation, rotation about the axis) are well separated from the frequency of useful axial translational mode, the frequency of which needs to be tuned exactly to the driving frequency (or vice versa).
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