SDL Control of the UltraLITE Precision Deployable Test Article Using Adaptive Spatio-Temporal Filtering Based Control Albert B. Bosse Keith K. Denoyer R. Scott Irwin Thomas D. Sharp Air Force Research Laboratory Stuart J. Shelley Kirtland Air Force Base Sheet Dynamics, Ltd. Cincinnati, OH 3/3/99, Page SDL-1
SDL Overview • UltraLITE Deployable Optical Telescope program • DOT test beds – Mirror Mass Simulator – PDOS – DOT BGD • Active structural control issues • Spatio-Temporal Filtering (STF) • STF based structural control • PDOS test experience 3/3/99, Page SDL-2
SDL Acknowledgements • Phase II SBIR award from Ballistic Missile Defense Organization (BMDO) • Contract managed by and technical collaboration with Air Force Research Lab - Kirtland AFB 3/3/99, Page SDL-3
SDL Air Force Research Laboratory Deployable Space Telescope Concept • Large aperature/resolution through deployable, sparse, optical array • Deployable primary mirrors • Golay 6 configuration • Telescoping seconday tower 3/3/99, Page SDL-4
SDL Deployable Optics Concepts Evaluation Experimental Test Beds • Mirror Mass Simulator (MMS) • Precision Deployable Optics Structure (PDOS) • Deployable Optical Telescope Brassboard Ground Demonstration (BGD) 3/3/99, Page SDL-5
SDL Preliminary DOT Evaluation - Mirror Mass Simulator •Mirror Mass Simulator mounted to optics bench •3 interferometer displacement sensors •3 piezo stack actuators •Electromagnetic disturbance shaker 3/3/99, Page SDL-6
SDL Precision Deployable Optical Structure Actuation Subsystem Mirror Simulator Optical Subsystem & Truth Sensor Deployable Boom Interface Granite Slab 3/3/99, Page SDL-7
SDL Deployable Optical Telescope Brassboard Ground Demonstration 1.5m Deployable Test Tower Telescope Secondary Mirror Optical Test Bench: Finite Conjugate Scene 3m Center of Curvature Deployable Sensor Laser Metrology Secondary Tower Composite/Glass Hybrid Mirrors Optical Bench Deployable Telescope Deployable Reaction Plate Aft Optics Precision Adaptive Optics Mechanisms Wavefront Sensors Integrated Technology in Simulated Space/Ops Environment Supporting SBL, Global Virtual Presence, and Tactical Imaging Missions 3/3/99, Page SDL-8
SDL Requirements SDL’s primary mission is to provide a Vibration Control System that will assist the Optical Control System in meeting the DOT mirror positioning requirements • Precision Deployable Optical Structure (PDOS): Achieve 30 nanometers or less RMS value for relative displacement between the granite slab and the mirror mass simulator • Deployable Optical Telescope (DOT) (1) Maintain the position of the primary mirror segments within: ± 14 nanometers error per segment Piston: ± 95 nanoradians error per segment Tilt: (2) Maintain the position of the secondary mirror within: Decenter ± 50 microns ± 4 microns Piston: ± 20 microradians Tilt: 3/3/99, Page SDL-9
SDL Deployable Optics - Jitter Requirements • Disturbances – torque wheel actuators – slewing – space based laser • Vibration Control – isolation – passive vibration control – high bandwidth position control – active vibration control 3/3/99, Page SDL-10
SDL Active Structural Vibration Control Issues • Modeling - accurate and complete dynamic models of complex “real-world” systems are difficult to obtain. • Time Variance - Often, by the time you’ve got the model the system has changed - It’s a moving target. – System dynamics - temperature, load, wear, damage – Discrete failures - sensors, actuators, signal conditioning • Computational burden 3/3/99, Page SDL-11
SDL Spatio-Temporal Filter Based Control 10 2 2 10 10 1 1 10 10 0 0 10 2 10 2 10 10 -1 -1 10 1 10 10 -2 1 -2 10 10 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 0 0 10 10 -1 10 2 -1 2 10 10 10 -2 10 1 1 10 0 10 20 30 40 50 60 70 80 90 100 10 -2 10 0 10 20 30 40 50 60 70 80 90 100 Uncontrolled 0 0 10 10 Controlled Response -1 -1 10 Response 10 -2 10 10 -2 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 Controlled Modal Uncontrolled Modal Responses Responses Extracted with STF 3/3/99, Page SDL-12
SDL Modal Coordinate Transformation Uncouples System into SDOF Modes + + = �� � Mx Cx Kx f Modal Coordinate Transformation L O + L O + L O � � � M P M P M P M P M P M P η �� η � η = Φ T m c k f M P M P M P N Q N Q N Q � � � b g b g b g N ∑ φ η = = Φ η x t t t r r = r 1 3/3/99, Page SDL-13
SDL STF Origin - Modal or Spatial Filtering ψ φ = ≠ T 0 i r i r Spatial filter vector ψ = = 1 i r N ∑ ψ = ψ φ η T T x t ( ) ( ) t i i r r = r 1 Extract single mode = ψ φ η T ( ) t response from i i i measured response = η ( ) t i 3/3/99, Page SDL-14
SDL Spatio-Temporal Filtering Spatial filter � η = ψ T x η estimate of at k k R U time k x | | k | | x S V Spatio-Temporal filter η − � k 1 η = ψ T estimate of at | | k � time k | | T W x − k Nt 3/3/99, Page SDL-15
SDL Spatio-Temporal vs. Modal Filtering • FIR or “all-zero” filter on each channel • Pole-zero cancellation & preferential pass filter – fewer sensors required • Inherent estimation of modal velocity • Compensation for filter delays, sensor & signal conditioning dynamics • Non-homogeneous sensor suites - piezo patches, accelerometers, etc. 3/3/99, Page SDL-16
SDL Adaptive Calculation of STF Coefficients using Reference Model Approach • Know only poles of controlled modes • Don’t know – mode shapes – modal scaling factors (modal mass) – modal participation vectors – anything about uncontrolled modes (not even poles) 3/3/99, Page SDL-17
SDL Adaptive Calculation of STF Coefficients using Reference Model Approach b g b g SDOF (Single η r + = η r + T z l f Mode) Reference λ k 1 k k Model R U b g b g b g b g η r 1 | | η r 1 = η r 1 + 1 z f k S V + λ b g k 1 k k η r = T l � + | | � k b g T W η rN b g b g b g i rN rN N η = η + z f k i i i + λ k 1 k k = η T r l k 3/3/99, Page SDL-18
SDL Adaptive Calculation of STF Coefficients using Reference Model Approach b g � = η r − η e k k k R U R U − x x | | | | k k = R U | | | | T ψ x � S V S V S V − k 1 = η − ψ T r T l T W | | | | k − � l x − | | | | k Nto T W T W η r x − k Nto k 3/3/99, Page SDL-19
SDL STF Based Modal Velocity Feedback Control Control Command Modal Coordinate Vector for i’th mode Velocity Estimate b g b g b g b g � i i i i = � η α f v c Force Vector Scalar Feedback Gain b g b g b g b g � i = � η α i i i f l c Estimated Modal Participation Vector is Ideal Force Vector 3/3/99, Page SDL-20
SDL Initial Mirror Mass Simulator Control Experiments • STF based velocity feedback • 3 inputs, 3 outputs, 5 controlled modes • Random disturbance excitation • 1 1/2 days to implement – familiarization with test bed – all system ID – control implementation and testing 3/3/99, Page SDL-21
SDL Implementation of STF Based Control dSpace System l � η � Controller ψ � + η � e ADC's b g − r l η � Ref. Model Control Command Random Excitation DAC's Control/Excitation Command Signal Cond Amplifiers Sensors Structure Actuators 3/3/99, Page SDL-22
SDL Preliminary DOT Evaluation - Mirror Mass Simulator •Mirror Mass Simulator mounted to optics bench •3 interferometer displacement sensors •3 piezo stack actuators •Electromagnetic disturbance shaker 3/3/99, Page SDL-23
SDL Initial Mirror Mass Simulator Control Experiments Interferometer 1 versus Disturbance Force 1 10 Amplitude - Displacement/Force 0 10 -1 10 -2 10 0 50 100 150 200 250 300 350 400 Frequency - Hertz 3/3/99, Page SDL-24
SDL Initial Mirror Mass Simulator Control Experiments Interferometer 2 versus Disturbance Force 1 10 Amplitude – Displacement/Force 0 10 -1 10 -2 10 0 50 100 150 200 250 300 350 400 Frequency - Hertz 3/3/99, Page SDL-25
SDL Initial Mirror Mass Simulator Control Experiments Interferometer 3 versus Disturbance Force 1 10 Amplitude - Displacement/Force 0 10 -1 10 -2 10 0 50 100 150 200 250 300 350 400 Frequency - Hertz 3/3/99, Page SDL-26
SDL Precision Deployable Optical Structure Mirror Inertial Simulator Back-Up Structure Gravity Off-Load Reference Bench Composite Boom Proved Deployment, Acquisition, Maintenance and Control System for a 2m Optical Segment 3/3/99, Page SDL-27
SDL Precision Deployable Optical Structure 3/3/99, Page SDL-28
SDL Precision Deployable Optical Structure 3/3/99, Page SDL-29
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