Intelligent Control of a Ducted-Fan VTOL UAV with Conventional Control Surfaces A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy Zamri Omar M.Eng. School of Aerospace, Mechanical, and Manufacturing Engineering College of Science, Engineering and Health RMIT University March 2010 i DECLARATION I certify that except where due acknowledgement has been made, the work is that of the author alone; the work has not been submitted previously, in whole or in part, to qualify for any other academic award; the content of the thesis is the result of work which has been carried out since the official commencement date of the approved research program; any editorial work, paid or unpaid, carried out by a third party is acknowledged; and, ethics procedures and guidelines have been followed. Zamri Omar 6 October 2010 ii ACKNOWLEDGMENTS I would like to thank many people who have enabled me to conduct this research. First, I am very grateful to my supervisors, Associate Professor Cees Bil and Dr. Robin Hill for their outstanding guidance, support, and patience all the way through. I would like express my thankful to my sponsorship providers; Public Service Department of Malaysia and Ministry of Higher Education Malaysia (Grant No: JPA(L)740414017077), and Universiti Tun Hussein Onn Malaysia (Grant No: KUiTTHO.PP/S/10.14/09 Jld 3(73)) for granting me a continuous financial support for this research and during my overseas stay. Thank you also to many staff at RMIT University and Universiti Tun Hussein Onn Malaysia who have helped me in many different ways. To my parents, my sincere thanks for their consistent love, support, and prayers. A very special thanks is to my wife, Fazlinda, for her endless patience, love, and support. To my son, Azim, and daughter, Rania, thanks for your patience too in allowing your dad to do his work at home. Finally, my greatest gratitude is to The Almighty God, that is Him who has made this thesis a reality. iii TABLE OF CONTENTS Declaration ii Acknowledgments iii List of Figures x List of Tables xv Summary 1 Chapter 1: Introduction 2 1.1 Rationale . 2 1.2 Problem Statement . 4 1.3 Scope and Limitations . 6 1.4 Thesis Outline . 7 Chapter 2: Literature Review and Theoretical Background 8 2.1 Introduction . 8 2.2 Needs and Challenges for VTOL UAVs . 8 2.3 Demands for Small Ducted-Fan UAVs . 11 2.4 Ducted-Fan VTOL UAV Configurations . 13 2.5 Challenges and Approaches to Autonomous Control of Ducted-Fan UAVs . 17 2.5.1 Conventional Flight Control System . 19 2.5.2 Intelligent Flight Control System . 21 iv 2.6 Fuzzy Logic Theory . 25 2.6.1 Fuzzy Sets . 26 2.6.2 Membership Functions and Logical Operators . 29 2.6.3 Linguistic Variable and Hedges . 32 2.6.4 Rule Base and Data Base . 34 2.6.5 Fuzzification, Fuzzy Inference, and Deffuzzification . 36 2.6.6 Scaling Factors, Tuning, and Evaluation . 43 2.7 Summary . 44 Chapter 3: Configuration, Aerodynamic, and Propulsion 45 3.1 Introduction . 45 3.2 Vehicle Configuration . 45 3.2.1 Design Considerations . 47 3.2.2 Geometrical Layout and Properties . 48 3.2.3 Mass and Inertia Properties . 51 3.2.4 Vehicle Specialty and Missions . 56 3.3 Aerodynamic . 57 3.3.1 Aerodynamic Coefficients . 58 3.3.1.1 Drag Estimation . 64 3.3.1.2 Stators Design . 67 3.3.1.3 Propeller Effects . 68 3.3.2 Control Surfaces Design . 69 3.3.3 Control Surfaces Aerodynamic . 71 3.4 Propulsion . 77 3.4.1 Power Estimation . 77 3.4.2 The Thrust . 84 3.4.3 Model of Brushless D.C Motor . 89 v 3.5 Summary . 92 Chapter 4: Vehicle dynamics 93 4.1 Introduction . 93 4.2 Axis Systems Definition . 93 4.2.1 Body-Axis System . 93 4.2.2 Earth-Axis System . 94 4.2.3 Stability and Wind Axis Systems . 95 4.3 Equations of Motion . 95 4.4 Aircraft Attitude and Position . 99 4.4.1 Axis Transformation . 101 4.4.2 Kinematic Equations . 104 4.4.3 Navigational Equations . 106 4.4.4 Vertical Euler Angles Representation . 107 4.4.5 Quaternion Representation . 110 4.5 Force and Moment . 111 4.6 Numerical Solution . 112 4.7 Summary . 112 Chapter 5: Flight Control System Design 114 5.1 Introduction . 114 5.2 General Overview of Flight Phases and Control . 114 5.3 Control Design Approach . 120 5.3.1 The Guidance Loop . 123 5.3.2 The Control Loop . 124 5.3.3 Control Design Steps . 125 5.3.4 Dominant Controller . 127 vi 5.3.5 Synthesis of Fuzzy Rules . 129 5.3.6 Properties of the FLC . 134 5.3.6.1 Input and Output Variables . 134 5.3.6.2 Fuzzy Sets, and Membership Functions . 135 5.3.6.3 Universe of Discourse, and Scaling Factors . 136 5.3.6.4 The Rules . 137 5.3.7 Computational Tools . 137 5.4 Vertical Flight Controller . 138 5.4.1 Vertical Flight Guidance . 141 5.4.1.1 Low-Speed Tilted Flight Guidance . 143 5.4.1.2 Ascend, Descend, and Pirouette Flight Guidance . 148 5.4.2 Vertical Flight Control . 149 5.4.2.1 Low-Speed Tilted Flight Control . 151 5.4.2.2 Ascend and Descend Flight Control . 154 5.4.2.3 Pirouette Control . 159 5.5 Transitions Flight Controller . 161 5.5.1 Vertical to Horizontal Transition Flight Control . 162 5.5.2 Horizontal to Vertical Transition Flight Control . 164 5.6 Horizontal Flight Controller . 167 5.6.1 Altitude Control . 170 5.6.2 Velocity Control . 171 5.7 Controllers Transition . 173 5.8 Summary . 177 Chapter 6: Simulation Results and Discussion 179 6.1 Introduction . 179 6.2 A Results Guide . 179 vii 6.3 Simulation Environment and Settings . 180 6.4 Disturbance Models . 181 6.5 Control and Simulation Model . 183 6.6 Controller Response . 186 6.7 Vertical Flight . 187 6.7.1 Ascend, Hover and Descend Flights . 189 6.7.2 Low-speed Tilted Flight . 193 6.7.2.1 Forward-Backward LSTF . 195 6.7.2.2 Sideways LSTF . 198 6.7.3 Pirouette . 204 6.8 Transition Flight . 208 6.8.1 Vertical to Horizontal Maneuver . 208 6.8.2 Horizontal to Vertical Maneuver . 215 6.9 Horizontal Flight . 217 6.9.1 Power Effect on Aerodynamic . 222 6.10 Autonomous Mission . 224 6.11 Summary . 230 Chapter 7:.