Navigation Functionalities for an Autonomous UAV Helicopter

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52 CHAPTER 4. PATH FOLLOWING CONTROL MODE Although the PFCM just described has exhibited a satisfactory performance in terms of robustness, the tracking capabilities in case of maneuvered flight (when path curvature change rapidly) were not satisfactory. For this reason, the possibility to improve the tracking performance was investigated in the case of maneuvered flight without a major redesign of the control system. The lateral control has been modified by adding an extra control loop on the roll channel besides the YACS control system. The new lateral control loop is depicted in Fig. 4.11 b). From the diagram one can compare the difference between the previous control scheme, Fig. 4.11 a), and the new one Fig. 4.11 b). Figure 4.11: a)Previous lateral control. b)Modified lateral control loop using a lead compensator. The inner compensator that was added provides a phase lead compensation with an integral action and has the following structure:
4.5. CONCLUSIONS 53 1 + s 1 C(s) = K(α ) + KI 1 + αs s (4.25) The phase lead compensation increases the bandwidth and, hence, makes the closed loop system faster, but it also increases the resonance frequency with the danger of undesired amplification of system noise. The control system has been tuned in simulation but a second tuning iteration was needed on the field due to the presence of damped oscillations on the roll channel. An experimental comparison between the modified control system and the previous one is shown in Fig. 4.12. The target velocity in both cases was set to 10 m/s. Fig. 4.13 depicts the target velocity and the actual helicopter velocity relative to the path on the right side of Fig. 4.12. The diagram on the right side in Fig. 4.12 depicts the path flown with the basic PFCM controller (Fig. 4.11 a). One can observe that in the dynamic part of the path, where the curvature changes rapidly, the controller is slow. This results in a relevant tracking error. The diagram on the left in Fig. 4.12 depicts a test of the same path flown with the modified roll control loop (Fig. 4.11 b). The new lateral control scheme improves the tracking capability in the presence of fast curvature change. The helicopter can follow the dynamic part of the path with considerably lower tracking error. 4.5 Conclusions The PFCM developed here has been integrated in the helicopter software architecture and it is currently used in a number of flight missions carried out in an urban area used for flight-tests. The goal has been the development of a reliable and flexible flight mode which could be integrated robustly with a path planner. Safety mechanisms have been built-in the PFCM in order to handle communication failures with the path planner (this can happen since the path planner is implemented on a separate computer). More details on this topic can be found in Paper I. Moreover, since the path planner was developed before the PFCM, a number of constraints
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Linköping Studies in Science and T
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Acknowledgements This work would ha
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Contents 1 Introduction 1 2 Overvie
Page 11 and 12: Chapter 1 Introduction An Unmanned
Page 13 and 14: of the environment in order to avoi
Page 15 and 16: Chapter 2 Overview This chapter pre
Page 17 and 18: 2.1. UAV SOFTWARE ARCHITECTURE 7 wh
Page 19 and 20: 2.2. THE UAV HELICOPTER PLATFORM 9
Page 21 and 22: 2.2. THE UAV HELICOPTER PLATFORM 11
Page 23 and 24: Chapter 3 Simulation 3.1 Introducti
Page 25 and 26: 3.2. HARDWARE-IN-THE-LOOP SIMULATIO
Page 27 and 28: 3.3. REFERENCE FRAMES 17 3.3 Refere
Page 29 and 30: 3.4. THE AUGMENTED RMAX DYNAMIC MOD
Page 31 and 32: 3.4. THE AUGMENTED RMAX DYNAMIC MOD
Page 33 and 34: 3.5. SIMULATION RESULTS 23 3.5 Simu
Page 35 and 36: 3.5. SIMULATION RESULTS 25 Figure 3
Page 37 and 38: 3.5. SIMULATION RESULTS 27 Figure 3
Page 39 and 40: Chapter 4 Path Following Control Mo
Page 41 and 42: 4.2. TRAJECTORY GENERATOR 31 Figure
Page 43 and 44: 4.2. TRAJECTORY GENERATOR 33 Fig. 4
Page 45 and 46: 4.2. TRAJECTORY GENERATOR 35 be use
Page 47 and 48: 4.2. TRAJECTORY GENERATOR 37 4.2.3
Page 49 and 50: 4.2. TRAJECTORY GENERATOR 39 radius
Page 51 and 52: 4.2. TRAJECTORY GENERATOR 41 Calcul
Page 55 and 56: 4.2. TRAJECTORY GENERATOR 45 by the
Page 59 and 60: 4.3. OUTER LOOP CONTROL EQUATIONS 4
Page 61: 4.4. EXPERIMENTAL RESULTS 51 Up [m]
Page 65 and 66: 4.5. CONCLUSIONS 55 Vel [m/s] 20 18
Page 67 and 68: Chapter 5 Sensor fusion for vision
Page 69 and 70: composed of three accelerometers an
Page 71 and 72: 5.1. FILTER ARCHITECTURE 61 filter
Page 73 and 74: 5.1. FILTER ARCHITECTURE 63 north,
Page 75 and 76: 5.2. EXPERIMENTAL RESULTS 65 Figure
Page 77 and 78: 5.2. EXPERIMENTAL RESULTS 67 Figure
Page 79 and 80: 5.2. EXPERIMENTAL RESULTS 69 by the
Page 81 and 82: 5.3. CONCLUSION 71 vision system st
Page 83 and 84: BIBLIOGRAPHY 73 [9] E. Frazzoli. Ro
Page 85 and 86: Appendix A 75
Page 87 and 88: A.1. PAPER I 77 is a three-dimensio
Page 89 and 90: A.1. PAPER I 79 The reference point
Page 91 and 92: A.1. PAPER I 81 Path Av Err Max Err
Page 93 and 94: A.2. PAPER II 83 From Motion Planni
Page 107 and 108: A.3. PAPER III 97 A.3 Paper III Aut
Page 109 and 110: A.3. PAPER III 99 the projection of
Page 111 and 112: A.3. PAPER III 101 yes Tbo > Tlim2
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A.3. PAPER III 103 immediately afte
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A.3. PAPER III 105 altitude [m] 20
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A.3. PAPER III 107 Fig. 10. Flight
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Department of Computer and Informat
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No 598 Rego Granlund: C 3 Fire - A
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No 1024 Aleksandra Tešanovic: Towa
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Navigation Functionalities for an Autonomous UAV Helicopter

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