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