The Pennsylvania State University The Graduate School Department of Aerospace Engineering ...

171 Pages·2014·13.89 MB·English

The Pennsylvania State University

The Graduate School

Department of Aerospace Engineering
ASSESSMENT OF CONTROL ALLOCATION OPTIMIZATION ON PERFORMANCE
AND DYNAMIC RESPONSE ENHANCEMENT OF A COMPOUND ROTORCRAFT
A Thesis in

Aerospace Engineering

by

Adam Thorsen

 2014 Adam Thorsen
Submitted in Partial Fulfillment
of the Requirements
for the Degree of
Master of Science

August 2014
The thesis of Adam Thorsen was reviewed and approved* by the following:

Joseph F. Horn
Professor of Aerospace Engineering
Thesis Advisor

Kenneth S. Brentner
Professor of Aerospace Engineering

George A. Lesieutre
Professor of Aerospace Engineering
Head of the Department of Aerospace Engineering

*Signatures are on file in the Graduate School
iii

ABSTRACT

This research investigates control allocation for a compound rotorcraft to minimize
power required in acceleration, pull-up, and turning maneuvers and examines the transient
response characteristics of a compound rotorcraft in order to establish methods of control that
enhance handling qualities via the use of redundant control surfaces. Simulations of a
hypothetical compound rotorcraft based on an H-60 airframe and rotor compounded with a wing
and pusher propeller are used. Background is provided on the simulated compound rotorcraft’s
performance in trim and the trim methodology employed, the simulated compound rotorcraft
model, and the behavior of redundant controls in minimum power quasi-steady maneuvering
flight; then the focus shifts to the transient response characteristics of the aircraft in various
maneuvers. In addition to the four traditional controls, this research will examine the use of five
redundant control effectors: rotor speed, propeller pitch, symmetric stabilator deflection,
symmetric wing flap deflection, and differential wing flap deflection, which can be optimized for
performance in trim and maneuvering flight along with handling qualities.
The results of the minimum power quasi-steady maneuver optimization are incorporated
into a g-command dynamic inversion controller that regulates longitudinal and vertical load factor
in minimum power flight. This g-command controller is used to achieve optimal control
allocation with regards to the propulsive force distribution between the main rotor and propeller,
and the lift force distribution between the main rotor and wing. Pull-up and turning maneuvers are
simulated to analyze predicted handling qualities both with and without redundant controls.
Quickness metrics (agility, roll attitude, and turn quickness) are also investigated for pull-up and
turning maneuvers to understand how the deployment of redundant controls might be used to
enhance transient response and handling qualities.
iv

TABLE OF CONTENTS
List of Figures .......................................................................................................................... vi
List of Tables ........................................................................................................................... xiv
Nomenclature ........................................................................................................................... xv
Acknowledgements .................................................................................................................. xx
Chapter 1 Introduction ............................................................................................................. 1
1.1 Background ................................................................................................................ 1
1.2 Literature Review ....................................................................................................... 6
1.3 Research Objectives ................................................................................................... 8
Chapter 2 Compound Rotorcraft Simulation Model ................................................................ 12
2.1 GENHEL-PSU ........................................................................................................... 12
2.2 Lift Compounding: Wing Model ............................................................................... 14
2.3 Thrust Compounding: Propeller Model ..................................................................... 16
Chapter 3 Trim and Quasi-Steady Maneuvering Flight Background ...................................... 19
3.1 Trim ............................................................................................................................ 19
3.1.1 Compound Rotorcraft Trim Theory ................................................................ 21
3.1.2 Main Rotor Collective Control Effectiveness ................................................. 26
3.1.3 High Speed Flight Trim ................................................................................... 27
3.2 Quasi-Steady Maneuvering Flight ............................................................................. 29
3.2.1 Minimum Power Quasi-Steady Accelerations at 100% RPM ......................... 30
3.2.2 Minimum Power Quasi-Steady Accelerations at High Advance Ratios ......... 34
3.2.3 Minimum Power Quasi-Steady Pull-ups at 100% RPM ................................. 36
3.2.4 Minimum Power Quasi-Steady Pull-ups at High Advance Ratios .................. 40
Chapter 4 Flight Control System Design ................................................................................. 42
4.1 Baseline Controller .................................................................................................... 42
4.1.1 Inner Loop Control Law .................................................................................. 43
4.2 G-Command Controller ............................................................................................. 48
4.2.1 Redundant Control Laws for Transient Deployment ...................................... 51
Chapter 5 Sustained Maneuver Simulations ............................................................................ 53
5.1 Piloted Simulation of a Level Acceleration ............................................................... 53
5.2 High Advance Ratio Level Acceleration Simulation ................................................. 57
5.3 Accelerated Climbing Turn Simulation ..................................................................... 61
v

Chapter 6 Transient Maneuver Simulations............................................................................. 67
6.1 Longitudinal Axis Simulations .................................................................................. 67
6.2 Lateral Axis Simulations ............................................................................................ 75
6.3 Transient Turn Simulations ........................................................................................ 79
Chapter 7 Generalized Maneuver Simulations ........................................................................ 84
7.1 Sustained Pull-up ....................................................................................................... 84
7.2 Sustained Turn ........................................................................................................... 86
Chapter 8 Concluding Remarks ............................................................................................... 90
8.1 Conclusions ................................................................................................................ 90
8.2 Recommendations for Future Work ........................................................................... 92
Appendix A Comprehensive Simulation Results for Trim ...................................................... 94
Appendix B Trends of Main Rotor Thrust in High Advance Ratio Trim ................................ 109
Appendix C Effect of Wing Incidence on Compound Rotorcraft Trim ................................... 113
Appendix D Propeller Performance Maps ............................................................................... 117
Appendix E Propeller vs. Main Rotor Propulsive Efficiency in Trim ..................................... 119
Appendix F Redundant Control Power Sensitivities in Trim .................................................. 123
Appendix G Extended Simulation Results for Accelerations and Pull-ups ............................. 130
Appendix H Derivation of Vertical Load Factor in Generalized Maneuvering Flight ............ 146
References ................................................................................................................................ 147
vi

LIST OF FIGURES
Figure 1-1. 16H-1A. ................................................................................................................. 2
Figure 1-2. XH-51A. ................................................................................................................ 3
Figure 1-3. AH-56A Cheyenne. ............................................................................................... 4
Figure 1-4. X-49A Speed Hawk. ............................................................................................. 6
Figure 1-5. Defiant. .................................................................................................................. 10
Figure 1-6. Optimum Speed Tiltrotor (OSTR). ....................................................................... 10
Figure 1-7. AVX’s JMR-FVL Entrant. .................................................................................... 10
Figure 1-8. Phantom Swift. ...................................................................................................... 11
Figure 2-1. Compound Rotorcraft Configuration. ................................................................... 13
Figure 2-2. Propeller Thrust Coefficient Validation. ............................................................... 16
Figure 2-3. Propeller Power Coefficient Validation. ............................................................... 17
Figure 3-1. Compound Rotorcraft FBD (Side Perspective). .................................................... 22
Figure 3-2. Compound Rotorcraft FBD (Top Perspective). .................................................... 22
Figure 3-3. Compound Rotorcraft FBD (Front Perspective). .................................................. 22
Figure 3-4. Trim Analysis for Total Power Required Survey at 180 knots, 90% RPM. ......... 27
Figure 3-5. Trim Analysis for Total Power Required Survey at 200 knots, 85% RPM. ......... 28
Figure 3-6. Min Power Propulsive Forces in Accelerations at 100% RPM. ............................ 31
Figure 3-7. Min Power Redundant Controls in Accelerations at 100% RPM. ........................ 32
Figure 3-8. Min Power Lift Forces in Accelerations at 100% RPM. ....................................... 33
Figure 3-9. Min Power Fuselage Pitch Attitudes in Accelerations at 100% RPM. ................. 33
Figure 3-10. Min Power Path in Accelerations at 120 knots, 100% RPM. .............................. 34
Figure 3-11. Min Power Propulsive Forces in Accelerations at 160 knots for 100% RPM
and 90% RPM. ................................................................................................................. 35
Figure 3-12. Min Power Propulsive Forces in Accelerations at 180 knots for 100% RPM
and 90% RPM. ................................................................................................................. 36
vii

Figure 3-13. Min Power Propulsive Forces in Accelerations at 90% RPM. ............................ 36
Figure 3-14. Min Power Lift Forces in Pull-ups at 100% RPM. ............................................. 37
Figure 3-15. Min Power Longitudinal Tip Path Plane Orientations in Pull-ups at 100%
RPM ................................................................................................................................. 37
Figure 3-16. Min Power Redundant Controls in Pull-ups at 100% RPM. ............................... 38
Figure 3-17. Min Power Fuselage Pitch Attitudes in Pull-ups at 100% RPM. ........................ 39
Figure 3-18. Min Power Path in Pull-ups at 150 knots, 100% RPM. ...................................... 39
Figure 3-19. Min Power Lift Forces in Pull-ups at 160 knots for 100% RPM and 90%
RPM. ................................................................................................................................ 40
Figure 3-20. Min Power Lift Forces in Pull-ups at 180 knots for 100% RPM and 90%
RPM ................................................................................................................................. 41
Figure 3-21. Min Power Lift Forces in Pull-ups at 90% RPM ................................................ 41
Figure 4-1. Model Following and Dynamic Inversion Control for ACAH ............................. 43
Figure 4-2. Model Following and Dynamic Inversion Control for RCAH. ............................. 43
Figure 4-3. Dynamic Inversion Control Scheme for Roll and Pitch Axes. .............................. 47
Figure 4-4. Dynamic Inversion Control Scheme for Yaw and Heave Axes. ........................... 47
Figure 4-5. G-Command Flight Control Architecture. ............................................................ 48
Figure 4-6. Acceleration Command Velocity Hold Control Architecture (ACVH) ................ 50
Figure 5-1. Airspeed and Rate of Climb in Piloted Level Acceleration .................................. 54
Figure 5-2. Propulsive Forces in Piloted Level Acceleration. ................................................. 54
Figure 5-3. Lift Forces in Piloted Level Acceleration. ............................................................ 55
Figure 5-4. Redundant Controls in Piloted Level Acceleration. .............................................. 55
Figure 5-5. Power Required in Piloted Level Acceleration. .................................................... 56
Figure 5-6. Airspeed and Rate of Climb in Level Acceleration. ............................................. 57
Figure 5-7. Propulsive Forces in Level Acceleration............................................................... 58
Figure 5-8. Redundant Controls in Level Acceleration ........................................................... 59
Figure 5-9. Lift Forces in Level Acceleration .......................................................................... 59
viii

Figure 5-10. Power Required in Level Acceleration. .............................................................. 60
Figure 5-11. Flight Path of Accelerated Climbing Turn .......................................................... 61
Figure 5-12. Airspeed and Rate of Climb in Accelerated Climbing Turn. .............................. 62
Figure 5-13. Attitudes in Accelerated Climbing Turn. ............................................................ 62
Figure 5-14. Vertical Load Factor in Accelerated Climbing Turn. .......................................... 63
Figure 5-15. Longitudinal Load Factor in Accelerated Climbing Turn. .................................. 63
Figure 5-16. Propulsive Forces in Accelerated Climbing Turn ............................................... 64
Figure 5-17. Lift Forces in Accelerated Climbing Turn .......................................................... 64
Figure 5-18. Redundant Controls in Accelerated Climbing Turn. ........................................... 65
Figure 5-19. Power Required in Accelerated Climbing Turn. ................................................. 66
Figure 6-1. Agility Quickness with Redundant Controls at 130 knots, 150 knots, and 170
knots for 2 second Longitudinal Cyclic Pulses ................................................................ 68
Figure 6-2. Agility Quickness with Redundant Controls at 130 knots, 150 knots,and 170
knots for 3 second Longitudinal Cyclic Pulses. ............................................................... 68
Figure 6-3. Agility Quickness With and Without Redundant Controls at 130 knots, 150
knots, and 170 knots for 2 second Longitudinal Cyclic Pulses. ....................................... 69
Figure 6-4. Command Tracking for 2 second, 1.4g Pull-up at 150 knots. ............................... 70
Figure 6-5. Vertical Load Factor for 2 second 1.4g Pull-up at 150 knots. ............................... 71
Figure 6-6. Redundant Longitudinal Controls for 2 second, 1.4g Pull-up at 150 knots. ......... 71
Figure 6-7. Lift Forces for 2 second, 1.4g Pull-up at 150 knots .............................................. 72
Figure 6-8. Angle of Attack for 2 second, 1.4g Pull-up at 150 knots ...................................... 73
Figure 6-9. Peak Pitch Rate and Agility Quickness for 2 second Vertical Load Factor
Commands at 150 knots ................................................................................................... 74
Figure 6-10. Propulsive Forces for 2 second, 1.4g Pull-up at 150 knots. ................................ 74
Figure 6-11. Pitching Moments for 2 second, 1.4g Pull-up at 150 knots ................................ 75
Figure 6-12. Roll Attitude Quickness at 130 knots, 150 knots, and 170 knots for Lateral
Cyclic steps. ..................................................................................................................... 76
Figure 6-13. Command Tracking for 47º bank at 150 knots. ................................................... 78
ix

Figure 6-14. Redundant Lateral Controls for 47º bank at 150 knots. ...................................... 78
Figure 6-15. Rolling Moments for 47º bank at 150 knots. ....................................................... 79
Figure 6-16. Command Tracking for Transient Turn .............................................................. 80
Figure 6-17. Controls for Transient Turn using Collective and Symmetric Wing Flaps ......... 81
Figure 6-18. Controls for Transient Turn using Differential Wing Flaps. ............................... 81
Figure 6-19. Pavel and Padfield: Turn Quickness in a Transient Turn [23]. ........................... 82
Figure 6-20. Turn Quickness in Transient Turn. ..................................................................... 83
Figure 7-1. Redundant Controls in a Pushover/Pull-up ........................................................... 84
Figure 7-2. Power in Pushover/Pull-up. ................................................................................... 85
Figure 7-3. Propulsive Forces in Pushover/Pull-up. ................................................................ 85
Figure 7-4. Angle of Attack in Pushover/Pull-up. ................................................................... 86
Figure 7-5. Redundant Controls in Sustained Turn. ................................................................ 87
Figure 7-6. Command Tracking in Sustained Turn. ................................................................ 87
Figure 7-7. Vertical Load Factor in Sustained Turn ................................................................ 89
Figure 7-8. Power in Sustained Turn ....................................................................................... 89
Figure A-1. Total Power Required Variation with Collective Pitch, Symmetric Stabilator
Deflection, and Propeller Pitch | 140 knots | 100% RPM. ............................................... 94
Figure A-2. Propeller Power Required Variation with Collective Pitch, Symmetric
Stabilator Deflection, and Propeller Pitch | 140 knots | 100% RPM. ............................... 95
Figure A-3. Tip Path Plane Longitudinal Orientation Variation with Collective Pitch,
Symmetric Stabilator Deflection, and Propeller Pitch (+ longitudinal tilt forward) |
140 knots | 100% RPM. ................................................................................................... 95
Figure A-4. Fuselage Pitch Attitude Variation with Collective Pitch, Symmetric
Stabilator Deflection, and Propeller Pitch | 140 knots | 100% RPM. ............................... 96
Figure A-5. Longitudinal Cyclic Variation with Collective Pitch, Symmetric Stabilator
Deflection, and Propeller Pitch | 140 knots | 100% RPM. ............................................... 96
Figure A-6. Lateral Cyclic Variation with Collective Pitch, Symmetric Stabilator
Deflection, and Propeller Pitch | 140 knots | 100% RPM ................................................ 97
x

Figure A-7. Wing Lift Variation with Collective Pitch, Symmetric Stabilator Deflection,
and Propeller Pitch | 140 knots | 100% RPM ................................................................... 97
Figure A-8. Stabilator Lift Variation with Collective Pitch, Symmetric Stabilator
Deflection, and Propeller Pitch | 140 knots | 100% RPM ................................................ 98
Figure A-9. Propeller Propulsive Force Variation with Collective Pitch, Symmetric
Stabilator Deflection, and Propeller Pitch | 140 knots | 100% RPM ................................ 98
Figure A-10. Total Power Required Variation with Collective Pitch, Symmetric Stabilator
Deflection, and Propeller Pitch | 180 knots | 90% RPM. ................................................. 99
Figure A-11. Propeller Power Required Variation with Collective Pitch, Symmetric
Stabilator Deflection, and Propeller Pitch | 180 knots | 90% RPM. ................................. 100
Figure A-12. Tip Path Plane Longitudinal Orientation Variation with Collective Pitch,
Symmetric Stabilator Deflection, and Propeller Pitch (+ longitudinal tilt forward) |
180 knots | 90% RPM. ..................................................................................................... 100
Figure A-13. Fuselage Pitch Attitude Variation with Collective Pitch, Symmetric
Stabilator Deflection, and Propeller Pitch | 180 knots | 90% RPM. ................................. 101
Figure A-14. Longitudinal Cyclic Variation with Collective Pitch, Symmetric Stabilator
Deflection, and Propeller Pitch | 180 knots | 90% RPM. ................................................. 101
Figure A-15. Lateral Cyclic Variation with Collective Pitch, Symmetric Stabilator
Deflection, and Propeller Pitch | 180 knots | 90% RPM .................................................. 102
Figure A-16. Wing Lift Variation with Collective Pitch, Symmetric Stabilator Deflection,
and Propeller Pitch | 180 knots | 90% RPM ..................................................................... 102
Figure A-17. Stabilator Lift Variation with Collective Pitch, Symmetric Stabilator
Deflection, and Propeller Pitch | 180 knots | 90% RPM .................................................. 103
Figure A-18. Propeller Propulsive Force Variation with Collective Pitch, Symmetric
Stabilator Deflection, and Propeller Pitch | 180 knots | 90% RPM .................................. 103
Figure A-19. Total Power Required Variation with Collective Pitch, Symmetric Stabilator
Deflection, and Propeller Pitch | 200 knots | 85% RPM. ................................................. 104
Figure A-20. Propeller Power Required Variation with Collective Pitch, Symmetric
Stabilator Deflection, and Propeller Pitch | 200 knots | 85% RPM. ................................. 105
Figure A-21. Tip Path Plane Longitudinal Orientation Variation with Collective Pitch,
Symmetric Stabilator Deflection, and Propeller Pitch (+ longitudinal tilt forward) |
200 knots | 85% RPM. ..................................................................................................... 105
Figure A-22. Fuselage Pitch Attitude Variation with Collective Pitch, Symmetric
Stabilator Deflection, and Propeller Pitch | 200 knots | 85% RPM. ................................. 106