Fault-tolerant Flight Control and Guidance Systems (eBook)

Between 2002 and 2004, Guillaum Ducard worked with the team designing the Pac-Car 2, designing hardware and control software for embedded fuel cell systems. The vehicle holds the world record for fuel economy. Since 2004, Doctor Ducard has been interested in hardware and software for unmanned aerial vehicles including fixed-wing aeroplanes, high-altitude atmospheric air ships and quadricopters. He received his Dr.Sc. degree from ETH in 2007. His current research involves the design of navigation algorithms, flight control and guidance systems for quadricopters. Guillaume Ducard is a member of the IEEE and of the AIAA.

Series Editors’ Foreword 9
Preface 11
Contents 12
Abbreviations 20
Introduction 21
1.1 Motivations for Fault-tolerant Control Systems for Unmanned Aerial Vehicles 21
1.2 Book Outline 22
Review 23
2.1 Definition of Fault-tolerant Systems 23
2.2 Challenges of Designing Reconfigurable Control Systems 27
2.3 Different Approaches for FDI Systems 28
2.4 Different Approaches for Flight Control Systems 31
2.5 Techniques to Design Fault-tolerant Flight Control Systems 31
2.6 Reconfigurable Guidance Systems 37
2.7 Real Flight Tests 37
References 39
Nonlinear Aircraft Model 47
3.1 Definitions of the Frames 47
3.2 Wind Disturbance 52
3.3 Model of the Low Altitude Atmosphere 53
3.4 Equations of Rigid-body Motion 53
3.5 Engine 57
3.6 Model of the Aerodynamic Forces 58
3.7 Model of the Aerodynamic Torques 59
3.8 Summary of the Nonlinear Aircraft Model 61
References 61
Nonlinear Fault Detection and Isolation System 62
4.1 Introduction 62
4.2 FDI Using MMAE Schemes 63
4.3 A New FDI Scheme Based on the EMMAE Method 65
4.4 Aircraft Actuator Configuration and Nonlinear Dynamics 68
4.5 Design of the EKFs 70
4.6 Actuator Fault Isolation 78
4.7 Simulation Results of the EMMAE-FDI with no Supervision System 83
4.8 Improvements to the EMMAE-FDI System 87
4.9 A Realistic Flight Scenario 91
4.10 An Additional Filtering Stage for the EMMAE- FDI System 99
4.11 Detection and Isolation of Simultaneous Failures 100
4.12 Use of the EMMAE-FDI for a Reconfigurable Flight Control System 103
4.13 Computational Complexity of the EMMAE-FDI 104
4.14 Conclusions 105
References 105
Control Allocation 108
5.1 Introduction to Control Allocation 108
5.2 Reconfigurable Flight Control System 109
5.3 Behavior Mode of Ailerons and Elevators 114
5.4 Multiple Failures 118
5.5 Extensions of the Method 118
5.6 Computational Load of the Method 119
5.7 Simulation Results 119
5.8 Conclusions 123
References 124
Nonlinear Control Design 126
6.1 Concept of Dynamic Inversion 126
6.2 Ideal or Perfect Dynamic Inversion 128
6.3 Architecture of the Controller of Desired Dynamics 130
References 138
Autopilot for the Longitudinal Motion 140
7.1 Equations for Longitudinal Mode Analysis 140
7.2 Dynamic Modes of the Longitudinal Plant 143
7.3 Validation of the Linear Longitudinal Model 144
7.4 Stability Analysis of the Uncertain Dynamic Inversion 147
7.5 General Control Architecture for the Longitudinal Motion 162
7.6 Pitch Rate Control 164
7.7 Angle-of-attack Control Loop 171
7.8 Rate-of-climb Controller 177
7.9 Altitude Controller 180
7.10 Airspeed Controller 186
References 191
Autopilot for the Lateral Motion 194
8.1 Equations for Lateral Motion Analysis 194
8.2 Dynamic Modes of the Lateral Plant 197
8.3 Validation of the Linear Lateral Model 198
8.4 Stability Analysis of the Uncertain Dynamic Inversion 202
8.5 Roll and Yaw Rate Controllers 210
8.6 Coordinated-turn Controllers 216
References 219
Reconfigurable Guidance System 220
9.1 Introduction 220
9.2 Lateral Guidance System 222
9.3 Regular Waypoint Tracking 225
9.4 Altitude Guidance Law 229
9.5 NFZ and Obstacles 230
9.6 Detection of the NFZ 233
9.7 NFZ Avoidance Algorithm 235
9.8 Simulation 242
9.9 Conclusions 247
References 247
Evaluation of the Reduction in the Performance of a UAV 248
10.1 Introduction 248
10.2 FDI System 249
10.3 Degraded Turn Performance Evaluation 249
10.4 Interface with the Guidance System 254
10.5 Stability Discussion 255
10.6 Simulation Results 255
10.7 Performance Degradation Around the Pitch and Yaw Axes 257
10.8 Conclusion 258
References 259
Conclusions and Outlook 260
11.1 Future Work 260
11.2 The Future of Fault-tolerant Flight Control Systems for UAVs 261
11.3 General Conclusion 261
VT , a, and ß Differential Equations 264
Discretization of Linear State Space Models 266
B.1 Continuous Model 266
B.2 Discrete Model 267
Nonlinear Transformations Used in the Longitudinal Controllers 270
C.1 Nonlinear Transformation T1 Between Second Time Derivative of Altitude ¨h and the Aircraft Normal Acceleration an 270
C.2 Nonlinear Transformation T2 Between the Angle of Attack a and the Aircraft Normal Acceleration an 271
C.3 Nonlinear Transformation T3 Between a. and the Pitch Rate q 272
Nonlinear Transformation Used in the Lateral- directional Controller 274
D.1 Dynamics of the Sideslip Angle 274
D.2 Roll Angle Command Signal and Equation Governing a Coordinated Turn 275
D.3 Law of Cosines 276
Linearization of the Aircraft Model at 30m/ s 277
E.1 Longitudinal Linear Model 277
E.2 Lateral Linear Model 278
Nomenclature 279
Index 283