Aircraft and rotorcraft system identification : engineering methods with flight-test examples

Providing an engineering treatment of system identification and how to apply it to flight vehicles, this book presents guidelines, and real-world flight-test results for a range of flight vehicles, from small uncrewed aerial vehicles to large manned aircraft/rotorcraft. It is useful for students and working engineers.

Author Notes

Mark B. Tischler is a senior scientist and flight control group leader for the U.S. Army Aeroflightdynamics Directorate, located at Ames Research Center, CA
Robert K. Remple works for the University of California-Santa Cruz as a Senior Technical Writer supporting the University Affiliated Research Center (UARC) at NASA/Ames Research Center

List of Figures	p. xi
List of Tables	p. xix
Nomenclature	p. xxiii
Acronyms	p. xxix
Preface	p. xxxi
Chapter 1 Introduction and Brief History of System Identification in the Frequency Domain	p. 1
1.1 Basic Concepts of System Identification of Aircraft and Rotorcraft	p. 1
1.2 Relationship Between Simulation and System Identification	p. 6
1.3 Special Challenges of Rotorcraft System Identification	p. 8
1.4 More About the Role of Nonparametric vs Parametric Models in Flight-Vehicle System Identification	p. 9
1.5 Frequency-Response Identification Method Is Well Suited to Flight-Vehicle Development	p. 12
1.6 Role and Limitations of Flight-Mechanics Models Determined with the System-Identification Method	p. 17
1.7 Brief History of the Development of Frequency-Domain Methods for Aircraft and Rotorcraft System Identification	p. 18
1.8 Organization of this Book	p. 20
Problems	p. 22
Chapter 2 Frequency-Response Method for System Identification	p. 25
2.1 Road Map of Frequency-Response Method for System Identification	p. 25
2.2 Key Features of the Frequency-Response Method for Flight-Vehicle System Identification	p. 29
2.3 Frequency-Response Identification Method Applied to the XV-15 Tilt-Rotor Aircraft	p. 35
2.4 Examples of CIFER[Registered] Applications	p. 51
Problems	p. 53
Chapter 3 Description of Example Cases	p. 55
3.1 Pendulum Example Problem	p. 55
3.2 XV-15 Tilt-Rotor Aircraft	p. 58
3.3 XV-15 Dynamic Characteristics in Hover	p. 58
3.4 Measurements for Closed-Loop Hover Flight Testing	p. 60
3.5 XV-15 Test Case Database for Hover	p. 62
3.6 XV-15 Dynamic Characteristics in Cruise	p. 64
3.7 Measurements for Open-Loop Cruise Flight Testing	p. 64
3.8 XV-15 Test Case Database for Cruise	p. 65
Problems	p. 67
Chapter 4 Overview of CIFER[Registered] Software	p. 69
4.1 Basic Characteristics of the CIFER[Registered] Software	p. 69
4.2 Dataflow Through CIFER[Registered]	p. 71
4.3 CIFER[Registered] Menu	p. 73
4.4 CIFER[Registered] User Interface	p. 73
4.5 Examples of CIFER[Registered] Utilities	p. 78
4.6 Interfaces with Other Tools	p. 79
Problems	p. 81
Chapter 5 Collection of Time-History Data	p. 83
5.1 Overview of Data Requirements for System Identification (Time Domain and Frequency Domain)	p. 83
5.2 Optimal Input Design	p. 85
5.3 Recommended Pilot Inputs for the Frequency-Response Identification Method	p. 86
5.4 Instrumentation Requirements	p. 88
5.5 Overview of Piloted Frequency Sweeps	p. 90
5.6 Detailed Design of Frequency-Sweep Inputs	p. 92
5.7 Flight-Testing Considerations	p. 94
5.8 Open-Loop vs Closed-Loop Testing for Bare-Airframe Identification	p. 95
5.9 Piloted Frequency Sweeps: What Is and What Is Not Important	p. 97
5.10 Summary of Key Points in Piloted Frequency-Sweep Technique	p. 100
5.11 Computer-Generated Sweeps	p. 102
5.12 Frequency-Response Identification from Other Types of Inputs	p. 112
Problems	p. 117
Chapter 6 Data Consistency and Reconstruction	p. 119
6.1 Modeling Measurement Errors in Flight-Test Data	p. 119
6.2 Simple Methods for Data Consistency and State Reconstruction	p. 129
Problems	p. 143
Chapter 7 Single-Input / Single-Output Frequency-Response Identification Theory	p. 145
7.1 Definition of Frequency Response	p. 146
7.2 Relating the Fourier Transform of the Time Signals to the Frequency Response H(f)	p. 147
7.3 Simple Example of Frequency-Response Interpretation	p. 149
7.4 General Observations	p. 152
7.5 Calculating the Fourier Transform and Spectral Functions	p. 152
7.6 Interpreting Spectral Functions	p. 158
7.7 Frequency-Response Calculation	p. 159
7.8 Coherence Function	p. 165
7.9 Random Error in the Frequency-Response Estimate	p. 167
7.10 Window Size Selection and Tradeoffs	p. 169
7.11 Frequency-Response Identification in CIFER[Registered] Using FRESPID	p. 175
7.12 Summary of Guidelines for Frequency-Response Identification	p. 177
7.13 Pendulum Example	p. 177
7.14 Applications and Examples	p. 178
Problems	p. 203
Chapter 8 Bare-Airframe Identification from Data with Feedback Regulation Active	p. 209
8.1 Limiting Conditions in Closed-Loop Identification	p. 209
8.2 Quantification of Bias Errors	p. 211
8.3 Bias Errors Defined	p. 213
8.4 Numerical Study of Identification Results Obtained Under Closed-Loop Conditions	p. 215
8.5 Flight-Test Implications	p. 224
8.6 Identification of Unstable Inverted Pendulum Dynamics	p. 225
8.7 Conclusions	p. 226
Problems	p. 226
Chapter 9 Multi-Input Identification Techniques	p. 229
9.1 Multi-Input Terminology	p. 229
9.2 Need for Multiple-Input Identification Technique	p. 230
9.3 Simple Two-Input Example	p. 231
9.4 Conditioned Spectral Quantities	p. 237
9.5 Example of a Two-Input Identification Solution Using the XV-15 Flight Data	p. 239
9.6 General MIMO Solution	p. 245
9.7 High Control Correlation	p. 248
9.8 Multiple-Input Identification in CIFER[Registered] Using MISOSA	p. 249
9.9 Example of MISO Solution for a Hovering Helicopter	p. 250
9.10 MIMO Identification Using a Multi-Input Maneuver	p. 254
9.11 Determination of Broken-Loop Response for MIMO Control System	p. 256
Problems	p. 257
Chapter 10 Composite Windowing	p. 259
10.1 Background	p. 259
10.2 Composite-Window Approach	p. 260
10.3 Choice of Window Sizes	p. 263
10.4 Composite-Window Calculations in CIFER[Registered] using COMPOSITE	p. 263
10.5 Composite-Window Results for Pendulum Example	p. 263
10.6 COMPOSITE Windowing in Single-Input and Multi-Input Analyses	p. 266
10.7 Composite-Windowing Results for XV-15 Closed-Loop SISO Identification in Hover p/[delta subscript lat]	p. 268
10.8 Composite-Windowing Results for Bo-105 Helicopter MIMO Identification	p. 271
10.9 Composite Results for Structural System Identification	p. 273
10.10 Composite Windowing in Spectral Analysis of Time-History Signals	p. 274
10.11 Summary	p. 275
Problems	p. 275
Chapter 11 Transfer-Function Modeling	p. 277
11.1 Motivations for Transfer-Function Modeling	p. 277
11.2 Transfer-Function Modeling Identification Method	p. 278
11.3 Model Structure Selection	p. 281
11.4 SISO Transfer-Function Identification in CIFER[Registered] Using NAVFIT	p. 284
11.5 Pendulum Example	p. 285
11.6 Handling-Qualities Applications	p. 286
11.7 Flight-Mechanics Characterization Studies	p. 298
11.8 Flight-Dynamics Models for Control System Design	p. 307
11.9 Aeroelastic Model Identification	p. 310
11.10 Subsystem Component Modeling	p. 314
11.11 Summary and a Look Ahead	p. 317
Problems	p. 317
Chapter 12 State-Space Model Identification-Basic Concepts	p. 321
12.1 Background	p. 322
12.2 MIMO State-Space Model Identification Using the Frequency-Response Method	p. 323
12.3 Accuracy Analysis	p. 330
12.4 Key Features of the Frequency-Response Method for State-Space Model Identification	p. 340
12.5 State-Space Model Structure	p. 342
12.6 State-Space Model Identification in CIFER[Registered] Using DERIVID	p. 347
12.7 Pendulum Example	p. 348
12.8 Identification of a XV-15 Closed-Loop State-Space Model	p. 350
12.9 Structural System Identification	p. 353
Problems	p. 357
Chapter 13 State-Space Model Identification: Physical Model Structures	p. 359
13.1 Background	p. 360
13.2 Buildup Approach to Developing the Appropriate Physical Model Structure	p. 362
13.3 Equations of Motion for Flight Vehicles	p. 362
13.4 Model Formulation in a State-Space Structure	p. 366
13.5 Frequency-Response Database and Frequency Ranges	p. 371
13.6 Checking the Initial Model Setup	p. 377
13.7 Model Identification and Structure Reduction	p. 378
13.8 Identification of Three-DOF Lateral/Directional Model for XV-15 in Cruise	p. 379
13.9 Identification of Three-DOF Lateral/Directional Model for XV-15 in Hover	p. 394
13.10 Accurate Determination of Stability and Control Derivatives from Nonlinear Simulation Using System Identification	p. 402
13.11 Identification of a Three-DOF Longitudinal Model of a Fixed-Wing UAV	p. 406
13.12 System Identification of a six-DOF MIMO Model of a Lightweight Manned Helicopter	p. 413
Problems	p. 430
Chapter 14 Time-Domain Verification of Identification Models	p. 433
14.1 Motivation for Time-Domain Verification	p. 433
14.2 Time-Domain Verification Method	p. 434
14.3 Estimating the Constant Bias and Reference Shift	p. 436
14.4 Correlation Problem	p. 439
14.5 Data Conditioning for Time-Domain Verification	p. 440
14.6 Time-Domain Verification in CIFER[Registered] Using VERIFY	p. 440
14.7 Closed-Loop Transfer-Function Model Verification for XV-15	p. 441
14.8 Bare-Airframe Model Verification for Cruise (XV-15)	p. 442
14.9 Bare-Airframe Model Verification for Hover (XV-15)	p. 447
Problems	p. 449
Chapter 15 Higher-Order Modeling of Coupled Rotor/Fuselage Dynamics	p. 451
15.1 Background and Literature on Identification of Extended Helicopter Models	p. 451
15.2 Hybrid Model Formulation	p. 452
15.3 Hybrid Model Identification of SH-2G Helicopter	p. 464
15.4 Lead-Lag Dynamics Identification for S-92 Helicopter	p. 490
Problems	p. 491
Appendix A Summary of Suggested Guidelines	p. 495
References	p. 499
Index	p. 515
Supporting Materials	p. 525

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