Navigation Functionalities for an Autonomous UAV Helicopter

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46 CHAPTER 4. PATH FOLLOWING CONTROL MODE previously mentioned, using a path described by a cubic polynomial, the curvature changes continuously and the helicopter almost never flies in trimmed conditions. The resulting umax might not always be consistent with the attitude dynamics ˙ θ and ˙ φ. The faster the speed, the more the attitude dynamics is relevant. The velocity vtarg3 is calculated as follows. The vertical velocity must be limited during a descending path because of the vortex ring which can build up around the main rotor in this flight condition. In this case, the helicopter descends into rotor down-wash and enters what is commonly called the vortex ring state (VRS). This situation can cause loss of helicopter control and might be difficult to recover. For this reason a limitation on the descending velocity component is necessary. The flow state diagram of Fig. 4.7 shows the combination of horizontal and vertical speed where VRS occurs. This diagram was developed at the Aviation Safety School, Monterey CA, in the late 1980s for use by mishap investigators in their analysis of several of these events. In this thesis, this diagram has been used as a guideline in choosing the right combination of vertical and horizontal speed in order to avoid a VRS situation. More details on VRS phenomenon can be found in [20]. The flow state diagram axes are parametrized with the hovering induced velocity which is calculated in feet/minutes as follows: Vi = 60 � DL 2ρ (4.21) where DL is the rotor disk loading (lbs/ft2 ) and ρ the air density ( SLUGS ft3 ). This diagram will be used to calculate a safe vertical speed. For the RMAX helicopter, the induced hovering velocity calculated using 4.21 and converted in m/s results in Vi=6.37 m/s. The value has been calculated using the air density at sea level ρ = 0.002377 SLUGS ft3 , RMAX weight of 80 kg and rotor diameter R=3.115 m. From the diagram, the vertical speed when the light turbulence first occurs is
4.2. TRAJECTORY GENERATOR 47 Figure 4.7: Flow states in descending forward flight.
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Linköping Studies in Science and T
Page 5: Acknowledgements This work would ha
Page 9 and 10: 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 53 and 54: 4.2. TRAJECTORY GENERATOR 43 Figure
Page 55: 4.2. TRAJECTORY GENERATOR 45 by the
Page 59 and 60: 4.3. OUTER LOOP CONTROL EQUATIONS 4
Page 61 and 62: 4.4. EXPERIMENTAL RESULTS 51 Up [m]
Page 63 and 64: 4.5. CONCLUSIONS 53 1 + s 1 C(s) =
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
Page 113 and 114:
A.3. PAPER III 103 immediately afte
Page 115 and 116:
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
Page 125 and 126:
No 1024 Aleksandra Tešanovic: Towa
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Navigation Functionalities for an Autonomous UAV Helicopter

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