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Weighted-Perpendicular-Tangent-Based Path-Following Control for Aerial Vehicles in Time-Varying Ambient Wind : 대기바람을 고려한 비행체의 수직-접선벡터 가중치 기반 경로추종 제어

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dc.contributor.advisor김유단-
dc.contributor.author서용준-
dc.date.accessioned2023-06-29T01:51:52Z-
dc.date.available2023-06-29T01:51:52Z-
dc.date.issued2023-
dc.identifier.other000000176728-
dc.identifier.urihttps://hdl.handle.net/10371/193121-
dc.identifier.urihttps://dcollection.snu.ac.kr/common/orgView/000000176728ko_KR
dc.description학위논문(박사) -- 서울대학교대학원 : 공과대학 기계항공공학부, 2023. 2. 김유단.-
dc.description.abstractIn this dissertation, a versatile path-following control method for aerial vehicles that can effectively deal with an ambient wind shear is proposed. Novel equations of motion for aerial vehicles considering the effect of continuously differentiable time-varying ambient winds are derived, and a path-following control law in a three-dimensional Euclidean space, called the Weighted-Perpendicular-Tangent-based Path-Following Control (WPTPFC), that makes the vehicle asymptotically follow a given sufficiently smooth desired path is developed.

The proposed equations of motion consist of the aerodynamic angles and the inertial flight path angles as state variables. The equations cover a large range of ambient wind speeds without any approximation or linearization. Two unique angles of sequential rotations called the path-relative wind angles are proposed to parametrize the difference between the air-relative velocity and the inertial velocity caused by ambient wind terms. The conventional aerodynamic roll angle is not defined in a wind condition; thus, a compatible modified version is also proposed. The resulting state equations are structured to form a cascade system, which helps designers interpret the physical and geometrical meaning of individual subsystems and efficiently design a corresponding feedback control law. The model particularly fits motion control problems such as trajectory tracking or path-following control of fixed-wing-type aerial vehicles in the presence of time-varying ambient wind. The properties and potential of the proposed formulation are discussed in depth by focusing on the meaning and use of each proposed angle and the wind estimation techniques.

In the design of WPTPFC, a reference point called the perpendicular foot is proposed for path-following control as an alternative to the closest point. Though the notion of perpendicular foot suffers from a similar singularity issue that the closest point has, it guarantees the continuity of solution with respect to the motion of the vehicle provided that the point does not reach some geometrical region, and it is shown that the region can be effectively avoided by the proposed singularity avoidance strategies. A Velocity Direction Input (VDI) and Steering Input (SI), which are common input configurations for mobile robots with nonzero moving speed, are considered the inputs of the control system. In particular, a special barrier function-based method called the Barrier Weighting Method (BWM) is developed to fully utilize the characteristics of the backstepping control for a certain class of constrained systems. Using the proposed technique, it is demonstrated that the velocity direction control law can be efficiently reused for the steering input control design preserving the singularity avoidance capability.

Finally, the flight control system and WPTPFC are unified based on the time-scale decomposition technique. The compatibility between the methods is investigated, and appropriate coordinate transformations and control allocation methods are developed. Numerical simulations are performed to demonstrate the effectiveness of the proposed control scheme.
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dc.description.abstract본 논문에서는 대기바람이 존재하는 환경에서 운용되는 비행체에 적용할 수 있는 경로추종 기법을 제안하였다. 연속 미분가능한 대기바람 속도를 고려하는 비행체 운동방정식을 유도하고, 이를 기반으로 한 비행제어 법칙을 설계하였다. 또한, 비행체가 충분히 매끈한 경로를 추종하도록 하는 수직-접선벡터 가중치 기반 경로추종 제어를 개발하고 비행제어 법칙과 통합하였다.

본 논문에서 제안한 운동방정식은 공력각과 관성 경로각을 상태변수로 가진다. 두 개의 경로대비 바람각(path-relative wind angle)을 정의하여 대기바람에 의해 발생하는 대기속도와 대지속도 벡터 성분의 차이를 매개화 하였다. 대기바람이 존재하는 상황에서 공력롤각을 정의하여 대기바람이 존재하는 환경에서도 균형선회가 수월하게 하였다. 제안한 운동방정식은 계단식 구조를 가지도록 정식화하여 제어법칙을 설계하는 데 도움이 되도록 하였다. 또한, 제안한 모델은 바람이 존재하는 상황에서도 관성 경로각의 거동을 효율적으로 표현하므로 경로추종 제어법칙을 설계하기에 유리하다.

한편, 수직-접선벡터 가중치 기반 경로추종 제어는 경로에 대한 수선의 발(perpendicular foot)을 기준점으로 채택하여, 기존 기법에서 널리 쓰이는 최단점이 가지는 특이점, 불연속성 등의 문제들을 보완하였다. 시스템 입력으로는 속도방향 벡터(velocity direction)와 조향 벡터(steering)을 고려하였다. 특히, 장벽가중치 기법(barrier weighting method)을 적용하여 조향벡터 입력 시스템에 백스텝핑 기법을 도입할 때 기준점 운동방정식이 가지는 특이점을 효과적으로 회피하도록 하였다.

위의 연구내용은 시간비례 분해기법(time-scale decomposition)을 적용하여 비행제어 법칙과 경로추종 제어기법을 통합하였다. 개별적으로 설계된 비행제어법칙 간의 호환성을 검토하고, 적절한 변환 및 조종할당 기법을 개발하였다. 본 논문에서 제안한 기법의 성능을 평가하기 위해 수치 시뮬레이션을 수행하였다.
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dc.description.tableofcontents1 Introduction 1
1.1 Motivation and Objective 1
1.1.1 Effects of Wind Shear on Aerial Vehicles 1
1.1.2 Path-Following Control for Aerial Vehicles 3
1.1.3 Unification of Flight Controller and PFC 4
1.1.4 Study Objective 5
1.2 Literature Survey 6
1.2.1 Flight in Ambient Wind Shear 6
1.2.2 PFC for Aerial Vehicles 7
1.3 Research Contribution 9
1.3.1 Flight Dynamics 9
1.3.2 Weighted-Perpendicular-Tangent-based PFC 10
1.3.3 Summary 11
1.4 Dissertation Organization 13
2 Flight Dynamics Considering Time-Varying Ambient Wind 14
2.1 Derivation of Equations of Motion 15
2.1.1 External Force and Moment 20
2.1.2 Angular Velocity Dynamics 22
2.1.3 Aerodynamic Angle Dynamics 22
2.1.4 Flight Path Angle Dynamics 25
2.1.5 Airspeed Dynamics 26
2.1.6 Ground Speed Dynamics 27
2.1.7 Aerodynamic Roll Angle Dynamics 28
2.1.8 Overall Dynamics 36
2.2 Discussions 39
2.2.1 Aerodynamic Roll Angle 39
2.2.2 Path-Relative Wind Angles 40
2.2.3 Compensation of Unsteady Winds 40
2.2.4 Local Wind Field 42
2.2.5 Wind Estimation 43
3 Design of Flight Control System 49
3.1 State Representation 50
3.2 Cascade System Approximation 51
3.3 Angular Velocity Tracking Control 52
3.4 Aerodynamic Angle Tracking Control 54
3.5 Flight-path Angle Tracking Control 56
3.6 Numerical Examples 58
3.6.1 Example 3.1 59
3.6.2 Example 3.2 60
3.6.3 Example 3.3 65
4 Lyapunov Barrier Weighting Method 67
4.1 Notation 71
4.2 Mathematical Preliminary 72
4.3 Barrier Method 78
4.4 Lyapunov Barrier Weighting Method 83
5 Weighted-Perpendicular-Tangent-based Path-Following Control 90
5.1 Notation 91
5.2 Path-Following Problem 92
5.2.1 Perpendicular Foot 92
5.2.2 Vehicle Dynamics 94
5.2.3 Problem Statement 96
5.2.4 Path and Initial Position 99
5.2.5 Closest Point and Perpendicular Foot 99
5.3 Velocity Direction Control 104
5.3.1 Dynamics 104
5.3.2 Controller Design 105
5.3.3 Direct Approaching 113
5.3.4 Singularity Avoidance 114
5.3.5 Design Example 116
5.4 Steering Control 118
5.4.1 Dynamics 118
5.4.2 Controller Design 120
5.4.3 Singularity Avoidance 122
5.4.4 Design Example 125
5.5 Numerical Simulations 127
5.5.1 Rotation weighting function 127
5.5.2 Singularity Avoidance 130
5.5.3 Various Initial Position and Velocity 133
6 Unification of Flight Control System and WPTPFC 137
6.1 Parameter Normalization 138
6.2 WPTPFC: Velocity Direction Control 138
6.2.1 FPA Command Filter 140
6.3 WPTPFC: Steering Control 144
6.3.1 Normal Acceleration Control Allocation 146
6.3.2 Low-pass Filter for VDI Control 146
6.4 Numerical Simulation 147
6.4.1 Scenario 1: straight line tracking 147
6.4.2 Scenario 2: descending vertical helix tracking 153
6.4.3 Various simulation results 156
7 Conclusion 165
7.1 Concluding Remarks 165
7.2 Future Research 166
Appendices 166
A Flight Dynamics 167
A.1 Components of the Equations of Motion 167
A.2 Angle Conversion 169
B WPTPFC 172
B.1 Foot Dynamics 172
B.1.1 Curve Parametrization 172
B.1.2 Robust Foot Control 173
초록 184
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dc.format.extentxi, 184-
dc.language.isoeng-
dc.publisher서울대학교 대학원-
dc.subjectFlight Dynamics-
dc.subjectAmbient Wind-
dc.subjectPath-Following Control-
dc.subjectBackstepping-
dc.subjectBarrier Weighting-
dc.subject.ddc621-
dc.titleWeighted-Perpendicular-Tangent-Based Path-Following Control for Aerial Vehicles in Time-Varying Ambient Wind-
dc.title.alternative대기바람을 고려한 비행체의 수직-접선벡터 가중치 기반 경로추종 제어-
dc.typeThesis-
dc.typeDissertation-
dc.contributor.AlternativeAuthorYongjun Seo-
dc.contributor.department공과대학 기계항공공학부-
dc.description.degree박사-
dc.date.awarded2023-02-
dc.identifier.uciI804:11032-000000176728-
dc.identifier.holdings000000000049▲000000000056▲000000176728▲-
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