AUTOMATIC FLIGHT CONTROL SYSTEMS – LATEST DEVELOPMENTS Edited by Thomas Lombaerts Automatic Flight Control Systems – Latest Developments Edited by Thomas Lombaerts Published by InTech Janeza Trdine 9, 51000 Rijeka, Croatia Copyright © 2011 InTech All chapters are Open Access distributed under the Creative Commons Attribution 3.0 license, which allows users to download, copy and build upon published articles even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. After this work has been published by InTech, authors have the right to republish it, in whole or part, in any publication of which they are the author, and to make other personal use of the work. Any republication, referencing or personal use of the work must explicitly identify the original source. As for readers, this license allows users to download, copy and build upon published chapters even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. Notice Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book. Publishing Process Manager Martina Durovic Technical Editor Teodora Smiljanic Cover Designer InTech Design Team First published December, 2011 Printed in Croatia A free online edition of this book is available at www.intechopen.com Additional hard copies can be obtained from orders@intechweb.org Automatic Flight Control Systems – Latest Developments, Edited by Thomas Lombaerts p. cm. ISBN 978-953-307-816-8 free online editions of InTech Books and Journals can be found at www.intechopen.com Contents Preface VII Part 1 Literature Review and Theoretical Developments 1 Chapter 1 Fundamentals of GNSS-Aided Inertial Navigation 3 Ahmed Mohamed and Apostolos Mamatas Chapter 2 Quantitative Feedback Theory and Its Application in UAV’s Flight Control 37 Xiaojun Xing and Dongli Yuan Chapter 3 Gain Tuning of Flight Control Laws for Satisfying Trajectory Tracking Requirements 71 Urbano Tancredi and Federico Corraro Part 2 Adaptive and Fault Tolerant Flight Control 93 Chapter 4 Adaptive Feedforward Control for Gust Loads Alleviation 95 Jie Zeng, Raymond De Callafon and Martin J. Brenner Chapter 5 Fault Tolerant Flight Control Techniques with Application to a Quadrotor UAV Testbed 119 Youmin Zhang and Abbas Chamseddine Chapter 6 Effects of Automatic Flight Control System on Chinook Underslung Load Failures 151 Marilena D. Pavel Chapter 7 Tool-Based Design and Evaluation of Resilient Flight Control Systems 185 Hafid Smaili, Jan Breeman and Thomas Lombaerts Preface The history of flight control is inseparably linked to the history of aviation itself. Shortly after the German aviation pioneer Otto Lilienthal (1848-1896) left the ground for the first time in his self-made glider from Windmühlenberg (windmill hill) of Derwitz (Germany) in the summer of 1891, the problem of flight in a heavier-than-air vehicle created a new challenge, that of controlled flight. During his numerous experimental flights, Otto Lilienthal realized that leaving the ground was easier than staying in the air. For controlling his flights, he invented the first means of lateral stabilization using a vertical rudder. Following the first successful motorized flight of the Wright Brothers in 1903, the first artificially controlled flight was demonstrated in 1914 by Lawrence Sperry (1892-1923), the third son of the gyrocompass co-inventor Elmer Ambrose Sperry, by flying his Curtiss-C-2 airplane hands-free in front of a speechless crowd. This very first autopilot consisted of three gyroscopes and a magnetic compass both linked to the pneumatically operated flight control surfaces. The autopilot enabled stable flight by holding the pitch, roll and yaw attitudes constant, while maintaining the compass course. Since these early days, Sperry and many other engineers improved the concept of automatic stabilized flight further up to highly advanced automatic fly-by-wire flight control systems which can be found nowadays in military jets and civil airliners. Even today, many research efforts are made for the further development of these flight control systems in various aspects. Recent new developments in this field focus on a wealth of different aspects, such as nonlinear flight control, autonomous control of unmanned aircraft, formation flying, aeroservoelastic control, intelligent control, adaptive flight control, fault tolerant flight control, and many others. This book focuses on a selection of these key research areas. This book consists of two major sections. The first section contains three chapters and focuses on a literature review and some recent theoretical developments in flight control systems. The second section discusses some concepts of adaptive and fault- tolerant flight control systems. This topic has been receiving a lot of research attention from the scientific community lately. Each technique discussed in this book is illustrated by a relevant example. The first chapter is a literature survey providing a global overview perspective to the field of GPS-aided inertial navigation. The chapter discusses the topics of modeling, sensor properties and estimation techniques. VIII Preface The second chapter discusses the concept of quantitative feedback theory. This frequency-based control technique makes use of the Nichols chart in order to achieve a desired robust design over a specified region of plant uncertainties. Desired time- domain responses are translated into frequency-domain tolerances, which lead to bounds (or constraints) on the loop transmission function. The design process is transparent, allowing a designer to see what trade-offs are necessary to achieve a desired performance level. As an example, QFT is applied for the lateral control of a UAV. The third chapter discusses the topic of gain tuning for flight control laws for an unmanned space re-entry vehicle technology demonstrator in order to satisfy trajectory tracking requirements. The method for gain tuning is based upon the Practical Stability criterion. This is a technique developed previously by the authors for analyzing the robustness of a given flight control law. In the fourth chapter, the first of the second section, an adaptive feedforward control method is suggested for gust load alleviation. With the novel development of airborne Light Detection and Ranging (LIDAR) turbulence sensor available for the accurate measurement of the vertical gust velocity at considerable distances ahead of the aircraft, it becomes feasible to design an adaptive feedforward control algorithm to alleviate the structural loads induced by any turbulence and to extend the life of the structure. This proposed approach identifies in real time the flexible modes for parameter adjustment in the feedforward controller. This method is demonstrated on the F/A-18 active aeroelastic wing simulation model. The fifth chapter provides an extensive overview of different fault-tolerant flight control techniques, including Gain-Scheduled PID control, Model Reference Adaptive Control, Sliding Mode Control, Backstepping Control, Model Predictive Control, and Flatness-based Trajectory Planning/Re-planning. At the end of the chapter, simulations and flight tests of a quadrotor UAV testbed are discussed. The sixth chapter investigates the contributions that an automatic flight control system (AFCS) may provide to the recovery prospects of the Chinook tandem helicopter after a load failure scenario. An analysis is made as to how the advanced AFCS, implemented to improve the handling qualities characteristics of the helicopter, improves the CH-47 behavior during emergency situations such as failure scenarios of its suspended load. An example of such a failure scenario is when one of the load suspension cables snaps. The seventh and last chapter describes a new high fidelity large transport aircraft simulation benchmark which has been developed as a tool-based design and evaluation platform for resilient flight control system design. The simulation model contains nonlinear kinematics and aircraft dynamics, and includes actuator and sensor properties. Moreover, the model includes an extensive list of failure modes, varying from stuck or faulty control surfaces to significant aerodynamic damage. An important failure mode is the engine separation scenario, which has been validated by means of Preface IX the black box data recovered from such an accident. This tool is freely available for the research community and can be used to develop new fault-tolerant flight control algorithms. I would like to express my sincere gratitude to all the authors for all the time and effort they spent contributing chapters of high quality to this book. I would like to thank the publisher, InTech, for taking the initiative to publish this book and for making this book Open Access, which guarantees a wide dissemination of the published results. I also wish to acknowledge the Publishing Process Manager Ms Martina Pecar-Durovic, for her indispensable technical and administrative assistance while preparing and publishing this book. Dr Ir Thomas Lombaerts German Aerospace Center DLR Institute of Robotics and Mechatronics Department of System Dynamics and Control Oberpfaffenhofen – Wessling Germany [...]... positional drift over time The goal of the aiding system is therefore to help estimate the errors and correct them 4 2 Automatic Flight Control Systems – Latest Will-be-set-by-IN-TECH Developments 2.2 Reference frames Proceeding from the sensor stratum up to more intuitively accessible reference systems, we define the following reference frames: • Sensor Frame (s-frame) This is the reference system in which... it is defined as being either the i-, e- or l-frames, especially when one must make the distinction between native INS output and transformed values in another frame 6 4 Automatic Flight Control Systems – Latest Will-be-set-by-IN-TECH Developments mean spin axis n u e Fig 4 Local-Level Frame 2.3 Geometric figure of the earth Having defined the common reference frames, we must consider the size and shape... begin with the simple case of a sphere of radius Re Note that the linear distance between two points along a meridian (in the North direction) is δn = ( Re + h)δψ (4) 8 6 Automatic Flight Control Systems – Latest Will-be-set-by-IN-TECH Developments and the distance along a parallel (in the East direction) is δe = ( Re + h) cos ψδλ (5) where h is the height above the sphere In the case of the ellipsoidal... 9.7803253359 m/s2 γb 9.8321849378 m/s2 Table 1 WGS84 parameters away from the ellipsoidal surface: γ = γ0 − (3.0877 × 10−6 − 4.4 × 10−9 sin2 φ)h + 0.72 × 10−12 h2 (16) 10 8 Automatic Flight Control Systems – Latest Will-be-set-by-IN-TECH Developments 2.6 Mathematical treatment of rotations 2.6.1 Direction cosines matrix Before proceeding to linear and rotational models of motion, we must first discuss the... term involving the rotation and the last three define the vector of the rotation matrix which is sufficient for a single rotation but leaves the problem of propagating 12 10 Automatic Flight Control Systems – Latest Will-be-set-by-IN-TECH Developments the transformation in time A convenient relation between the elements of λ and quaternions exists, which allows us to take advantage of some felicitous properties... cancel, yielding the representation of the vector in the desired frame In navigation 4 after the rigid transformation between the IMU and the vehicle has been applied 14 12 Automatic Flight Control Systems – Latest Will-be-set-by-IN-TECH Developments applications, the time derivative of Ri is a function of the angular velocity expressed by the b b b vector ωib between the two reference frames Here, ωib... in the local-level reference frame are therefore ⎛ ⎞ ⎛ ⎞ D −1 v l ˙ rl l ˙ x = ⎝ vl ⎠ = ⎝ Rl fb − (2Ωie + Ωl )vl + gl ⎠ ˙ b el ˙ Rl Rl (Ωb − Ωb ) l b b ib il (59) 16 14 Automatic Flight Control Systems – Latest Will-be-set-by-IN-TECH Developments + + Accels Gyros ∫ - + - × ∫ ∫ + + × 2 × + + Fig 7 Mechanization in the l-frame 3.3 Mechanization in the l -frame Because of its wide applicability and intuitiveness,... ||α|| 2 (63) Implementation in either the DCM or the quaternion parametrizations involves employing numerical integration techniques, which we shall not cover here 18 16 Automatic Flight Control Systems – Latest Will-be-set-by-IN-TECH Developments 3.5 Initialization As stated above, the implementation of an INS requires the knowledge of initial position, velocity and attitude Initial position and velocity... Gaussian sequence with a shaping matrix G The general state-variable form of the error model is therefore ˙ δx ˙ δu ˙ x(t) = F x F xu 0 Fu δx δu F x(t) + 0 G G w (76) 20 18 Automatic Flight Control Systems – Latest Will-be-set-by-IN-TECH Developments The terms in F xu account for the dependence of the navigational errors upon the sensor errors and the full state vector includes the elements of u In an INS... l ⎟ l −Ωil l − δωil − Rl d ⎟ b ⎟ ⎟ −αd + wd ⎠ (89) − βb + wb To derive the elements of the dynamics matrix F, we need to specify all the matrix elements in (89) 22 20 Automatic Flight Control Systems – Latest Will-be-set-by-IN-TECH Developments 3.6.6 Matrix formulation of position errors Assuming M and N to be constant over small distances δvl = Dδ˙ l + Dr δrl r ⎛ 0 ( N + h) cos φ 0 = ⎝M + h 0 0 With . AUTOMATIC FLIGHT CONTROL SYSTEMS – LATEST DEVELOPMENTS Edited by Thomas Lombaerts Automatic Flight Control Systems – Latest Developments Edited. www.intechopen.com Additional hard copies can be obtained from orders@intechweb.org Automatic Flight Control Systems – Latest Developments, Edited by Thomas Lombaerts p. cm. ISBN 978-953-307-816-8 . development of these flight control systems in various aspects. Recent new developments in this field focus on a wealth of different aspects, such as nonlinear flight control, autonomous control of unmanned