Copyright © SCD 2016 All rights reserved SCD Proprietary MULTIMODAL TUNED DYNAMIC ABSORBER FOR SPLIT STIRLING LINEAR CRYOCOOLER A VEPRIK, A TUITTO SCD, IMOD

Copyright © SCD 2016 All rights reserved SCD Proprietary OUTLINE 1.INTRODUCTION AND MOTIVATION 2.TUNED DYNAMIC ABSORBER – HOW STUFF WORKS? 3.MULTIMODAL TUNED DYNAMIC ABSORBER CONCEPT EQUATIONS OF MOTION ATTAINABLE PERFORMANCE PRACTICAL DESIGN AND TUNING CONCEPT DYNAMIC SIMULATIONS – PICS AND MOVIES 4.CONCLUSIONS AND FUTURE WORK

Copyright © SCD 2016 All rights reserved SCD Proprietary INTRODUCTION AND MOTIVATION Novel HOT IR detectors are operative at 150K and above Bespoke low size, weight, power and price (SWAPP) cryo- refrigerators Closed cycle split Stirling linear cryo-refrigerator: compressor + expander Single piston compressor – better SWAPP Paradigm: high vibration export Typical: high driving frequency small weight of moving assemblies small stroke Result 1: low vibration export (comparable with existing dual-piston compressors) and less affected visual perception Result 2: single piston compressors “as is” are suitable for most of applications Vibration sensitive applications: tuned dynamic absorber (TDA)

Copyright © SCD 2016 All rights reserved SCD Proprietary INTRODUCTION AND MOTIVATION SWAP CRYOGENIC COOLERS (COURTESY OF DRS, L3, THALES, COBHAM, AIM, RICOR)

Copyright © SCD 2016 All rights reserved SCD Proprietary TUNED DYNAMIC ABSORBER – HOW STUFF WORKS? US # A B. Ross and R.W. Olan WO A1 C. Rosenhagen and I. Rühlich

Copyright © SCD 2016 All rights reserved SCD Proprietary TUNED DYNAMIC ABSORBER – HOW STUFF WORKS? TDA WITH SINGLE PISTON COMPRESSORS COURTESY OF AIM, SUNPOWER, RICOR

Copyright © SCD 2016 All rights reserved SCD Proprietary TUNED DYNAMIC ABSORBER – HOW STUFF WORKS? Vibration sensitive applications: vibration export by expander can not be disregarded Inline (1 inline TDA) or side-by-side architecture (2 TDAs)

Copyright © SCD 2016 All rights reserved SCD Proprietary TUNED DYNAMIC ABSORBER – HOW STUFF WORKS? Basic dynamic model and equations of motion:

Copyright © SCD 2016 All rights reserved SCD Proprietary TUNED DYNAMIC ABSORBER – HOW STUFF WORKS? SOLUTION AT NO DAMPING Asymptotically stable equilibrium at any initial conditions and occasional disturbances

Copyright © SCD 2016 All rights reserved SCD Proprietary TUNED DYNAMIC ABSORBER – HOW STUFF WORKS?

Copyright © SCD 2016 All rights reserved SCD Proprietary

TUNED DYNAMIC ABSORBER – HOW STUFF WORKS?

Copyright © SCD 2016 All rights reserved SCD Proprietary MULTIMODAL TUNED DYNAMIC ABSORBER Vibration export from side-by-side cryo-refrigerator: Two parallel forces (pair) of same frequency and fixed phase lag Equivalent to force and moment of same frequency and fixed phase lag Multimodal TDA Three degrees of freedom sprung system: translation and 2 tilt modes Resonant frequencies are equal and matched to the driving frequency The reaction force and moment are counterbalancing the vibration export Application field: line of side jitter and dynamic defocus control in vibration sensitive application with side-by-side packaged cryo-refrigerator NOVEL CONCEPT

Copyright © SCD 2016 All rights reserved SCD Proprietary MULTIMODAL TUNED DYNAMIC ABSORBER DYNAMIC MODEL AND EQUATIONS OF MOTION

Copyright © SCD 2016 All rights reserved SCD Proprietary MULTIMODAL TUNED DYNAMIC ABSORBER SOLUTION IN FREQUENCY DOMAIN AT NO DAMPING TUNING

Copyright © SCD 2016 All rights reserved SCD Proprietary MULTIMODAL TUNED DYNAMIC ABSORBER ATTAINABLE PERFORMANCE NUMERICAL VALUES

Copyright © SCD 2016 All rights reserved SCD Proprietary ATTAINABLE PERFORMANCE MULTIMODAL TUNED DYNAMIC ABSORBER Typical requirement for tilt: 25  rad Reference case: no TDA. 6  m translation; 263  rad tilt SDOF TDA: prior art TDA. 2  m translation; 50  rad tilt TDOF TDA: multimodal TDA. 0.4  m translation; 5  rad tilt

Copyright © SCD 2016 All rights reserved SCD Proprietary ATTAINABLE PERFORMANCE MULTIMODAL TUNED DYNAMIC ABSORBER Effect of frequency detuning

Copyright © SCD 2016 All rights reserved SCD Proprietary PRACTICAL DESIGN AND TUNING CONCEPT MULTIMODAL TUNED DYNAMIC ABSORBER 1- compressor 2 - expander 3 - transfer line 4 - primary proof ring 5 – flexural bearing 6 - secondary proof ring Translation frequency depends on the axial stiffness of flexural bearing and aggregate mass of proof rings Tilt frequency depends on the angular stiffness of flexural bearing and aggregate moment of inertia of proof rings Displacing secondary proof ring along the primary proof ring modifies moment of inertia without affecting the mass Tuning scenario: Driving frequency is tuned to the frequency of translation resonance Tilt frequency is tuned to the driving frequency by displacing secondary proof ring

Copyright © SCD 2016 All rights reserved SCD Proprietary PRACTICAL DESIGN AND TUNING CONCEPT MULTIMODAL TUNED DYNAMIC ABSORBER Flexural bearing - photoetching

Copyright © SCD 2016 All rights reserved SCD Proprietary FINITE ELEMENTS MODAL ANALYSIS ModeFrequency, Hz #1 rotation60 #2 translation100 #3,4 tilt100 #5,6 in-plane140

Copyright © SCD 2016 All rights reserved SCD Proprietary FINITE ELEMENTS MODAL ANALYSIS RESONANT FREQUENCIES AT DIFFERENT POSITIONS OF CORRECTION RING MULTIMODAL TUNED DYNAMIC ABSORBER

Copyright © SCD 2016 All rights reserved SCD Proprietary FATIGUE SAFETY MULTIMODAL TUNED DYNAMIC ABSORBER

Copyright © SCD 2016 All rights reserved SCD Proprietary DYNAMIC SIMULATIONS – PICS AND MOVIES MULTIMODAL TUNED DYNAMIC ABSORBER SOFT SUPPORTS ENCLOSURE COLD FINGER COMPRESSOR 100Hz MULTIMODAL TUNED DYNAMIC ABSORBER CG

Copyright © SCD 2016 All rights reserved SCD Proprietary DYNAMIC SIMULATIONS – PICS AND MOVIES MULTIMODAL TUNED DYNAMIC ABSORBER NO TDA

Copyright © SCD 2016 All rights reserved SCD Proprietary DYNAMIC SIMULATIONS – PICS AND MOVIES MULTIMODAL TUNED DYNAMIC ABSORBER NO TDA CF axial = 6  m CF tilt =( )/100E+03=268  rad

Copyright © SCD 2016 All rights reserved SCD Proprietary DYNAMIC SIMULATIONS – PICS AND MOVIES MULTIMODAL TUNED DYNAMIC ABSORBER WITH TDA

Copyright © SCD 2016 All rights reserved SCD Proprietary DYNAMIC SIMULATIONS – PICS AND MOVIES MULTIMODAL TUNED DYNAMIC ABSORBER WITH TDA CF axial = 0.04  m CF tilt =( )/100E+03=0.39  rad

Copyright © SCD 2016 All rights reserved SCD Proprietary CONCLUSIONS AND FUTURE WORK Multimodal tuned dynamic absorber – powerful tool for cryocooler-induced line of sight jitter and dynamic defocusing control Minimum added weight – use of moment of inertia On the spot tuning is possible Full scale testing is underway