STRAIN ACTUATED AEROELASTIC CONTROL Charrissa Y. Lin B.S., Aeronautics and Astronautics Massachusetts Institute of Technology, 1990 Submitted to the Department of Aeronautics and Astronautics in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE in AERONAUTICS AND ASTRONAUTICS at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY February 1993 © Massachusetts Institute of Technology, 1993. All rights reserved Signature of Author ..~.Y -' '~ I" . . . .. "rl ir I I I - Department of Aero /htic and Astronautics Janu ary 15, 1993 -. Certified by I - -' Professor Edward F. Crtley Department of Aeronautics and Astronaitics Mac Vicar Faculty Fellow Thesis Advisor Accepted by Sofessor Harold Y. Wachman Chairman, Department Gradiate Cormittee MASSACHUSETTS INSTITUTE OF TFCi~hi"' nny 0 FEB 17 1993 1 UBRARIES STRAIN ACTUATED AEROELASTIC CONTROL by CHARRISSA Y. LIN Submitted to the Department of Aeronautics and Astronautics on January 15, 1993 in partial fulfillment of the requirements for the Degree of Master of Science in Aeronautics and Astronautics ABSTRACT The preliminary design of a wing with strain actuation and conventional flap actuation for vibration and flutter suppression experiments is completed. A two degree of freedom typical section model with steady aerodynamics is used to gain an understanding of the fundamentals of the strain actuated aeroelastic control problem. Actuation issues and the effects of fiber and geometric sweep are examined using the typical section. Controllers are designed using the Linear Quadratic Regulator (LQR) method and observers are designed using the Kalman filter. The results are verified through a series of parameter variations and the incorporation of unsteady aerodynamics. With the typical section analyses as a foundation, the actual design is begun. The functional requirements and the design parameters are explicitly outlined. Non-parametric studies are used to determine several of the geometric design parameters. Specifically, a scaling analysis is used to determine the piezoelectric thickness and the spar thickness. Three parametric trade studies are used to determine the remainder of the design parameters. A five mode Rayleigh-Ritz analysis with two dimensional unsteady strip theory aerodynamics is used for all of the parametric trade studies. The first trade study examines the interaction of the fiber and the geometric sweep. The effect of fiber and geometric sweep on the stability characteristics, the piezoelectric actuation, and the relative authority of LQR controllers using piezoelectric actuation or conventional flap actuation is observed. The second trade study consists of the design of a tip mass flutter stopper. The final trade study investigates the influence of taper on the dynamics of the wing. Thesis Supervisor: Dr. Edward F. Crawley Title: Professor of Aeronautics and Astronautics MacVicar Faculty Fellow Acknowledgements Although there is only one author's name on the title page of this thesis, there are many people who have contributed greatly to its completion. First I would like to thank my advisor, Professor Ed Crawley, for the countless discussions and meetings that have peppered the last two and a half years and that have aided my intellectual growth (or at least we hope so). In addition, I would like to thank Professor John Dugundji who has served as an unofficial co-advisor for the past half year for all of the time he has been willing to spend. I also have to thank the National Science Foundation for their generous fellowship during my years of being a Master's student. Next I would like to say thanks to all of the people of SERC - past and present (although I guess there aren't too many in the past category). Thanks for the technical discussions and the social ones, too. I'd especially like to mention my officemates who have had to put up with my idiosyncrasies, even if they haven't always turned up the heat. To my parents who have always taught me that education is very important and to my sister - for always trying to understand me. To Alissa Fitzgerald - whom I will always admire for her strength. To "the gang" - for friendship and fun times. To Mark Campbell - thank you for listening to me and keeping your cool when I was losing mine. Without you around, grad school would have been much less enjoyable. Go Penguins! And finally, to Terry. I hope you will always know how much I appreciate your unflagging support. Thank you for always being there to listen to me vent my frustrations, for helping me find my strength when it didn't seem like I had any left, and for providing a safe harbor. I can't say enough about your role in my thesis, my sanity, and my life. Table of Contents Introduction ......................................................................... 15 Chapter 1......................................................................... 15 Foundation for Design ....................................................................... 23 Chapter 2: Typical Section Analyses .......................................... 23 2.1 Introduction ........................................ 23 2.2 Description of model .................................................. 24 2.3 Control analysis for the reference case.........................28 2.4 Fiber vs. Geometric Sweep..........................................49 2.5 Robustness of Qualitative Results: Parameter Variation ......................................................... 58 2.6 Incorporation of unsteady aerodynamics...................64 2.7 Sum m ary ................................................................. 71 Building the Design ........................................................................ 73 Chapter 3: Functional Requirements and Design Parameters ..... 73 3.1 Introduction ............................................................. 73 3.2 Functional Requirements ................. 74 3.3 Design Parameters .................................................. 78 Chapter 4: Non-Parametric Studies...........................................81 4.1 Introduction ............................................................. 81 4.2 Survey of commercial aircraft.......................................82 4.3 Scaling analysis ....................................... ....... 83 Chapter 5: Design Trade 1: Geometric vs. Fiber Sweep...........93 5.1 Introduction ........................................................... 93 5.2 Model Development....................................................94 5.3 Application to simple rectangular plates ................... 103 5.4 Application to Wing Model: Aeroelastic Behavior ...... 107 5.5 Application to Wing Model: Actuation Issues ............ 112 5.6 Summary ....................................... ......... 128 Chapter 6: Design Trade 2: Tip Mass Flutter Stopper ................ 131 6.1 Introduction ................................... .......... 131 6.2 Variation in hinge position....................................133 6.3 Variation in mass ......................................... .......... 137 6.4 Variation in length... .............................. ................ 139 6.5 Final design............................................................141 Chapter 7: Design Trade 3: Taper Ratio............................. 143 7.1 Introduction ........................................................... 143 7.2 Structural and aerodynamic models........................ 143 7.3 Flutter analysis................................. ......... 145 7.4 Effect on actuation .............................................147 Conclusion ........................................................................................ 151 Chapter 8................................................................. ............... 151 8.1 Summary of final design ........................................ 151 8.2 Summary of Scientific Issues.......................153 Appendix A........ ....................................... 157 Appendix B .................................................................................. 161 Appendix C ...................................................................................... 163 Appendix D ............................................. 169 Bibliography.................................................................................... 171 List of Figures Figure 2.1 Typical section geometry...............................24 Figure 2.2 Transformation from Leading edge-Wing-Trailing Edge to Wing-Aileron-Tab.................................................25 Figure 2.3 Pole movement for nominal typical section as airspeed changes ..................................................................... 30 Figure 2.4 Pole and individual SISO transfer function zero frequencies versus non-dimensionalized airspeed. Nominal param eters.....................................................33 Figure 2.5 Pole and zero locations for the individual SISO transfer functions at design point 1 ....................................... 34 Figure 2.6 Pole and zero locations for the individual SISO transfer functions at design point 2 ........................................... 35 Figure 2.7 Loci of the LQR closed loop poles for the four actuators acting individually ..................................... 39 Figure 2.8 Cost curves for single actuator systems at design point 1. ................................................................................ 40 Figure 2.9 Loci of LQR closed loop poles for systems using m ultiple actuators ...................................................... 42 Figure 2.10 Cost curves for systems with multiple actuators ............ 43 Figure 2.11 Loci of LQR closed loop poles for design point 2, all actuator combinations ................................................. 44 Figure 2.12 Cost curves for all actuator combinations for design point 2 ............ ...................................................... 45 Figure 2.13 Cost curve comparison of different measurement schemes at 1% noise.............. ...................................48 Figure 2.14 Sign convention for Rayleigh-Ritz modeshapes.............50 Figure 2.15 Location of elastic axis for varying fiber sweep angle.........53 Figure 2.16 Transformation of coordinates for addition of geometric sweep........................................................ 54 Figure 2.17 Typical section stability characteristics for varying geometric and fiber sweep angles ................................. 57 Figure 2.18 Parameter variation on the spacing between elastic axis and center of gravity...........................................59 Figure 2.19 Pole/zero movement with respect to the non- dimensional airspeed for the variation of the spacing between the elastic axis and the center of gravity .......... 61 Figure 2.20 Parameter variation on location of elastic axis / center of gravity pair............................................................. 62 Figure 2.21 Pole/zero movement with respect to non-dimensional airspeed for variation of location of elastic axis/center of gravity pair......................................... .......... ....... 63 Figure 2.22 Comparison of one-pole approximations to the tabulated values of Theodorsen's function.....................65 Figure 2.23 Pole movement with change in airspeed for nominal typical section, unsteady aerodynamics ........................... 66 Figure 2.24 Pole/zero movement with respect to non-dimensional airspeed for nominal typical section with unsteady aerodynamics .................... . ............ .................6.8. Figure 2.25 Loci of LQR closed loop poles for all combinations of actuators at design point 1, unsteady aerodynamics .......... 69 Figure 2.26 State cost vs. control cost for nominal plant with unsteady aerodynamics at design point 1.......................70 Figure 5.1 Sign convention for Rayleigh-Ritz and aerodynamic analysis ................................... ....................................9 4 Figure 5.2 Calculated flutter and divergence speeds for the ply fiber angle vs. structural sweep angle trade . 3" by 12" plates...................................................................... 105 Figure 5.3 Pole locus for a ply fiber angle of -15 degrees and a structural sweep angle of 30 degrees ............................ 107 Figure 5.4 Schematic of wing model used in analysis .................... 108 Figure 5.5 Flutter and divergence speeds for the ply fiber angle vs. structural sweep angle trade. Wing model ...................... 110 Figure 5.6 Pole locus for a ply fiber angle of -45 degrees and a structural sweep angle of 30 degrees.............................111 Figure 5.7 Pole locus for a ply fiber angle of -15 degrees and structural sweep angle of 30 degrees.........................112 Figure 5.8 Inclusion of flap in wing model ..................................... 115 Figure 5.9 Deflection and curvature contours for the two primary modes of wing model with a [0/0/90]s laminate ................ 119 Figure 5.10 Deflection and curvature contours for the two primary modes of wing model with a [-15/-15/0]s laminate............120 Figure 5.11 Deflection and curvature contours for the two primary modes of wing model with a [-30/-30/0]s laminate..........121 Figure 5.12 Cost curves for the wing model at a geometric sweep angle of 30 degrees for varying ply fiber angles .............. 125 Figure 5.13 Cost curves for the wing model with a [-15/-15/0]s laminate for varying geometric sweep angles................ 127 Figure 6.1 Schematics of nominal wing model and wing model with typical flutter stopper deployed positions................ 134 Figure 6.2 Fixed and deployed flutter speeds for hinge position trade ............................................................... 135 Figure 6.3 Deployed/undeployed flutter speed and dynamic pressure ratios for hinge position trade ......................... 135 Figure 6.4 Pole loci for the undeployed flutter stopper and the deployed flutter stopper at the leading edge hinge position ........................................................ ............... 136 Figure 6.5 Undeployed and deployed flutter speeds for mass trade .............................................................. 138 Figure 6.6 Deployed/undeployed flutter speed and dynamic pressure ratios for mass trade........................................138 Figure 6.7 Undeployed and deployed flutter speeds for length trade . ................................................................... 140 Figure 6.8 Deployed/undeployed flutter speed and dynamic pressure ratios for length trade ................................... 140
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