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The Pennsylvania State University The Pennsylvania State University The Graduate School Department of Aerospace Engineering REAL-TIME PATH PLANNING AND AUTONOMOUS CONTROL FOR HELICOPTER AUTOROTATION A Dissertation in Aerospace Engineering by Thanan Yomchinda 2013 Thanan Yomchinda Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy May 2013 The dissertation of Thanan Yomchinda was reviewed and approved* by the following: Joseph F. Horn Associate Professor of Aerospace Engineering Dissertation Co-Advisor Co-Chair of Committee Jacob W. Langelaan Associate Professor of Aerospace Engineering Dissertation Co-Advisor Co-Chair of Committee Edward C. Smith Professor of Aerospace Engineering Christopher D. Rahn Professor of Mechanical Engineering George A. Lesieutre Professor of Aerospace Engineering Head of the Department of Aerospace Engineering *Signatures are on file in the Graduate School iii ABSTRACT Autorotation is a descending maneuver that can be used to recover helicopters in the event of total loss of engine power; however it is an extremely difficult and complex maneuver. The objective of this work is to develop a real-time system which provides full autonomous control for autorotation landing of helicopters. The work includes the development of an autorotation path planning method and integration of the path planner with a primary flight control system. The trajectory is divided into three parts: entry, descent and flare. Three different optimization algorithms are used to generate trajectories for each of these segments. The primary flight control is designed using a linear dynamic inversion control scheme, and a path following control law is developed to track the autorotation trajectories. Details of the path planning algorithm, trajectory following control law, and autonomous autorotation system implementation are presented. The integrated system is demonstrated in real-time high fidelity simulations. Results indicate feasibility of the capability of the algorithms to operate in real-time and of the integrated systems ability to provide safe autorotation landings. Preliminary simulations of autonomous autorotation on a small UAV are presented which will lead to a final hardware demonstration of the algorithms. iv TABLE OF CONTENTS LIST OF FIGURES ................................................................................................................. vi LIST OF TABLES ................................................................................................................... x NOMENCLATURE ................................................................................................................ xi ACKNOWLEDGEMENTS ..................................................................................................... xiii Chapter 1 Introduction ............................................................................................................. 1 1.1 Mechanics of Autorotation ......................................................................................... 3 1.2 Related Work ............................................................................................................. 5 1.2.1 Helicopter Critical Trajectories ....................................................................... 6 1.2.2 Rotorcraft Path Tracking Control .................................................................... 10 1.2.3 Dubins Curve................................................................................................... 11 1.3 Objective .................................................................................................................... 12 1.4 Method and Design .................................................................................................... 13 1.4.1 Sensor System ................................................................................................. 15 1.4.2 Landing-Site Selection .................................................................................... 15 1.4.3 Autorotation Trajectory Generation ................................................................ 16 1.4.4 Autonomous Flight Control ............................................................................ 18 1.4.5 System Evaluation ........................................................................................... 19 1.5 Summary of Contributions ......................................................................................... 20 Chapter 2 Autorotation Trajectory Planning ............................................................................ 22 2.1 Specifications of Generic Utility Helicopter .............................................................. 23 2.2 Vehicle Dynamics for Trajectory Computation ......................................................... 25 2.3 Entry Phase Path Generation ...................................................................................... 29 2.3.1 Entry Path Optimization Method 1 ................................................................. 30 2.3.2 Entry Path Optimization Method 2 ................................................................. 33 2.3.3 Analysis of Entry Phase Trajectory Methods .................................................. 38 2.4 Descent Phase Path Generation .................................................................................. 40 2.4.1 Trajectory Formulation ................................................................................... 40 2.4.2 Planar Path Planning ....................................................................................... 46 2.4.3 Quasi-steady State Autorotation ...................................................................... 66 2.4.4 Trajectory Planning Using Optimization ........................................................ 70 2.4.5 Reachable Range Extension ............................................................................ 78 2.5 Flare Phase Path Generation ...................................................................................... 82 2.5.1 Safe Landing Set Method ................................................................................ 83 2.5.2 Backward Trajectory Generation Method for the Flare Phase Trajectory ...... 88 Chapter 3 Autonomous Control ............................................................................................... 93 3.1 Inner-loop Linear Dynamic Inversion Control........................................................... 93 v 3.1.1 Desired Response ............................................................................................ 94 3.1.2 Inversion Model .............................................................................................. 95 3.1.3 Turn Coordination ........................................................................................... 97 3.2 Outer-loop Nonlinear Inversion Control .................................................................... 98 Chapter 4 Implementation and Real-Time Simulation Results ................................................ 105 4.1 Flight Simulation Description .................................................................................... 105 4.2 Implementation for Real-time Simulated Flights ....................................................... 107 4.2.1 Primary Flight Control System........................................................................ 109 4.2.2 Tuning of Point Mass Model ........................................................................... 110 4.2.3 Trajectory Generation Overview ..................................................................... 112 4.2.4 Pre-flight Computation .................................................................................... 113 4.2.5 Path Planner (In-flight Operation) ................................................................... 114 4.2.6 Flight Director (Autopilot) .............................................................................. 116 4.3 Real-time Simulation Results ..................................................................................... 122 4.4 Discussion .................................................................................................................. 140 Chapter 5 Implementation and Preliminary Result on Helicopter UAV ................................. 144 5.1 Hornet Mini Helicopter UAV .................................................................................... 144 5.2 Implementation for UAS Simulation ......................................................................... 146 5.3 Preliminary Simulation Results.................................................................................. 150 Chapter 6 Conclusions and Future work .................................................................................. 156 6.1 Conclusions ................................................................................................................ 156 6.2 Future Work ............................................................................................................... 158 Appendix A Point Mass Model Parameters ............................................................................. 160 Appendix B Proof of Equations ............................................................................................... 162 B.1 Heading Dynamics .................................................................................................... 162 B.2 Position Dynamics ....................................................................................................
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