Learning and Near-Optimal Control of Underactuated Surface Vessels With Periodic Disturbances

In this article, we propose a novel learning and near-optimal control approach for underactuated surface (USV) vessels with unknown mismatched periodic external disturbances and unknown hydrodynamic parameters. Given a prior knowledge of the periods of the disturbances, an analytical near-optimal control law is derived through the approximation of the integral-type quadratic performance index with respect to the tracking error, where the equivalent unknown parameters are generated online by an auxiliary system that can learn the dynamics of the controlled system. It is proved that the state differences between the auxiliary system and the corresponding controlled USV vessel are globally asymptotically convergent to zero. Besides, the approach theoretically guarantees asymptotic optimality of the performance index. The efficacy of the method is demonstrated via simulations based on the real parameters of an USV vessel

Experimental Validation Of A Robust Surge Speed Controller For Marine Surface Vessels

The focus of the current work is on providing experimental validation for the robust performance and good tracking characteristic of a surge speed controller for autonomous piloting of an under-actuated 16 ft boat in the completely uncontrolled setting of open-water Lake Saint Clair, Michigan. The controller is designed based on the sliding mode methodology and completely ignores the dynamics of the marine surface vessel (MSV) in its formulation. The testing was conducted under considerable unstructured uncertainties and unpredictable environmental disturbances induced by waves, sea-currents, and wind. The experimental results serve to validate the robust tracking characteristic of the controller and prove the successful implementation of the controller without prior knowledge of the system dynamics; thus, yielding a robust model-less controller

Robust trajectory tracking control for unmanned surface vessels under motion constraints and environmental disturbances

To achieve a fully autonomous navigation for unmanned surface vessels (USVs), a robust control capability is essential. The control of USVs in complex maritime environments is rather challenging as numerous system uncertainties and environmental influences affect the control performance. This paper therefore investigates the trajectory tracking control problem for USVs with motion constraints and environmental disturbances. Two different controllers are proposed to achieve the task. The first approach is mainly based on the backstepping technique augmented by a virtual system to compensate for the disturbance and an auxiliary system to bound the input in the saturation limit. The second control scheme is mainly based on the normalisation technique, with which the bound of the input can be limited in the constraints by tuning the control parameters. The stability of the two control schemes is demonstrated by the Lyapunov theory. Finally, simulations are conducted to verify the effectiveness of the proposed controllers. The introduced solutions enable USVs to follow complex trajectories in an adverse environment with varying ocean currents

TRACKING OF NON-STANDARD TRAJECTORIES USING MPC METHODS WITH CONSTRAINTS HANDLING ALGORITHM

In recent decades, a Model-Based Predictive Control (MPC) has revealed its dominance over other control methods such as having an ability of constraints handling and input optimization in terms of the value function. However, the complexity of the realization of the MPC algorithm on real mechatronic systems remains one of the major challenges. Traditional predictive control approaches are based on zero regulation or a step change. Nevertheless, more complicated systems still exist that need to track setpoint trajectories. Currently, there is an active development of robotics and the creation of transport networks of movement without human participation. Therefore, the issue of programming the given trajectories of vehicles is relevant. In this article, authors reveal the alternative solution for tracking non-standard trajectories in spheres such as robotics, IT in mechatronics, etc., that could be used in self-driving cars, drones, rockets, robot arms and any other automized systems in factories. The ability of Model-Based Predictive Control (MPC) such as the constraints handling and optimization of input in terms of the value function makes it extremely attractive in the industry. Nevertheless, the complexity of implementation of MPC algorithm on real mechatronic systems remains one of the main challenges. Secondly, common predictive control algorithms are based on the regulation approach or a simple step shift. However, there exist systems that are more complicated where a setpoint to be tracked is given in the form of trajectories. In this project, there were made several modifications in order to improve an MPC algorithm to make better use of information about the trajectories

멀티로터 기반 다목적 비행 로봇 플랫폼을 위한 강건 제어 및 완전구동 비행 매커니즘

학위논문(박사)--서울대학교 대학원 :공과대학 기계항공공학부,2020. 2. 김현진.오늘날 멀티로터 무인항공기는 단순한 비행 및 공중 영상 촬영용 장비의 개념을 넘어 비행 매니퓰레이션, 공중 화물 운송 및 공중 센싱 등의 다양한 임무에 활용되고 있다. 이러한 추세에 맞추어 로보틱스 분야에서 멀티로터 무인항공기는 부과된 임무에 맞추어 원하는 장비 및 센서를 자유로이 탑재하고 비행할 수 있는 다목적 공중 로봇 플랫폼으로 인식되고 있다. 그러나 현재의 멀티로터 플랫폼은 돌풍 등의 외란에 다소 강건하지 못한 제어성능을 보인다. 또한, 병진운동의 제어를 위해 비행 중 지속적으로 동체의 자세를 변경해야 해 센서 등 동체에 부착된 탑재물의 자세 또한 지속적으로 변화한다는 단점을 가지고 있다. 위의 두 가지 문제들을 해결하고자 본 연구에서는 외란에 강건한 멀티로터 제어기법과, 병진운동과 자세운동을 독립적으로 제어할 수 있는 새로운 형태의 완전구동 멀티로터 비행 매커니즘을 소개한다. 강건 제어기법의 경우, 먼저 정확한 병진운동 제어를 위한 병진 힘 생성 기법을 소개하고 뒤이어 병진 힘 외란에 강건한 제어를 위한 외란관측기 기반 강건 제어 알고리즘의 설계 방안을 논의한다. 제어기의 피드백 루프 안정성은 mu 안정성 분석 기법을 통해 검증되며, mu 안정성 분석이 가지는 엄밀한 안정성 분석의 결과를 검증하기 위해 스몰게인 이론 (Small Gain Theorem) 기반의 안정성 분석 결과가 동시에 제시 및 비교된다. 최종적으로, 개발된 제어기를 도입한 멀티로터의 3차원 병진 가속도 제어 성능 및 힘 벡터의 형태로 인가되는 병진 운동 외란에 대한 극복 성능을 실험을 통해 검증하여, 제안된 제어기법의 효과적인 비행 지점 및 궤적 추종 능력을 확인한다. 완전 구동 멀티로터의 경우, 기존의 완전구동 멀티로터가 가진 과도한 중량 증가 및 저조한 에너지 효율을 극복하기 위한 새로운 매커니즘을 소개한다. 새로운 매커니즘은 기존 멀티로터와 최대한 유사한 형태를 가지되 완전구동을 위해 오직 두 개의 서보모터만을 포함하며, 이로 인해 기존 멀티로터와 비교해 최소한의 형태의 변형만을 가지도록 설계된다. 새로운 플랫폼의 동적 특성에 대한 분석과 함께 유도된 운동방정식을 기반으로 한 6자유도 비행 제어기법이 소개되며, 최종적으로 다양한 실험과 그 결과들을 통해 플랫폼의 완전구동 비행 능력을 검증한다. 추가적으로 본 논문에서는 완전구동 멀티로터가 가지는 여분의 제어입력(redundancy)를 활용한 쿼드콥터의 단일모터 고장 대비 비상 비행 기법을 소개한다. 비상 비행 전략에 대한 자세한 소개 및 실현 방법, 비상 비행 시의 동역학적 특성에 대한 분석 결과가 소개되며, 실험결과를 통해 제안된 기법의 타당성을 검증한다.Recently, multi-rotor unmanned aerial vehicles (UAVs) are used for a variety of missions beyond its basic flight, including aerial manipulation, aerial payload transportation, and aerial sensor platform. Following this trend, the multirotor UAV is recognized as a versatile aerial robotics platform that can freely mount and fly the necessary mission equipment and sensors to perform missions. However, the current multi-rotor platform has a relatively poor ability to maintain nominal flight performance against external disturbances such as wind or gust compared to other robotics platforms. Also, the multirotor suffers from maintaining a stable payload attitude, due to the fact that the attitude of the fuselage should continuously be changed for translational motion control. Particularly, unstabilized fuselage attitude can be a drawback for multirotor's mission performance in such cases as like visual odometry-based flight, since the fuselage-attached sensor should also be tilted during the flight and therefore causes poor sensor information acquisition. To overcome the above two problems, in this dissertation, we introduce a robust multirotor control method and a novel full-actuation mechanism which widens the usability of the multirotor. The goal of the proposed control method is to bring robustness to the translational motion control against various weather conditions. And the goal of the full actuation mechanism is to allow the multi-rotor to take arbitrary payload/fuselage attitude independently of the translational motion. For robust multirotor control, we first introduce a translational force generation technique for accurate translational motion control and then discuss the design method of disturbance observer (DOB)-based robust control algorithm. The stability of the proposed feedback controller is validated by the mu-stability analysis technique, and the results are compared to the small-gain theorem (SGT)-based stability analysis to validate the rigorousness of the analysis. Through the experiments, we validate the translational acceleration control performance of the developed controller and confirm the robustness against external disturbance forces. For a fully-actuated multirotor platform, we propose a new mechanism called a T3-Multirotor that can overcome the excessive weight increase and poor energy efficiency of the existing fully-actuated multirotor. The structure of the new platform is designed to be as close as possible to the existing multi-rotor and includes only two servo motors for full actuation. The dynamic characteristics of the new platform are analyzed and a six-degree-of-freedom (DOF) flight controller is designed based on the derived equations of motion. The full actuation of the proposed platform is then validated through various experiments. As a derivative study, this paper also introduces an emergency flight technique to prepare for a single motor failure scenario of a multi-rotor using the redundancy of the T3-Multirotor platform. The detailed introduction and implementation method of the emergency flight strategy with the analysis of the dynamic characteristics during the emergency flight is introduced, and the experimental results are provided to verify the validity of the proposed technique.1 Introduction 1 1.1 Motivation 1 1.2 Literature survey 3 1.2.1 Robust translational motion control 3 1.2.2 Fully-actuated multirotor platform 4 1.3 Research objectives and contributions 5 1.3.1 Goal #I: Robust multirotor motion control 5 1.3.2 Goal #II: A new fully actuated multirotor platform 6 1.3.3 Goal #II-A: T3-Multirotor-based fail-safe flight 7 1.4 Thesis organization 7 2 Multi-Rotor Unmanned Aerial Vehicle: Overview 9 2.1 Platform overview 9 2.2 Mathematical model of multi-rotor UAV 10 3 Robust Translational Motion Control 13 3.1 Introduction 14 3.2 Translational force/acceleration control 14 3.2.1 Relationship between \mathbf{r} and \tilde{\ddot{\mathbf{X}}} 15 3.2.2 Calculation of \mathbf{r}_d from \tilde{\ddot{\mathbf{X}}}_d considering dynamics 16 3.3 Disturbance observer 22 3.3.1 An overview of the disturbance-merged overall system 22 3.3.2 Disturbance observer 22 3.4 Stability analysis 26 3.4.1 Modeling of P(s) considering uncertainties 27 3.4.2 \tau-determination through \mu-analysis 30 3.5 Simulation and experimental result 34 3.5.1 Validation of acceleration tracking performance 34 3.5.2 Validation of DOB performance 34 4 Fully-Actuated Multirotor Mechanism 39 4.1 Introduction 39 4.2 Mechanism 40 4.3 Modeling 42 4.3.1 General equations of motion of TP and FP 42 4.3.2 Simplified equations of motion of TP and FP 46 4.4 Controller design 49 4.4.1 Controller overview 49 4.4.2 Independent roll and pitch attitude control of TP and FP 50 4.4.3 Heading angle control 54 4.4.4 Overall control scheme 54 4.5 Simulation result 56 4.5.1 Scenario 1: Changing FP attitude during hovering 58 4.5.2 Scenario 2: Fixing FP attitude during translation 58 4.6 Experimental result 60 4.6.1 Scenario 1: Changing FP attitude during hovering 60 4.6.2 Scenario 2: Fixing FP attitude during translation 60 4.7 Applications 63 4.7.1 Personal aerial vehicle 63 4.7.2 High MoI payload transportation platform - revisit of [1] 63 4.7.3 Take-off and landing on an oscillating landing pad 64 5 Derived Research: Fail-safe Flight in a Single Motor Failure Scenario 67 5.1 Introduction 67 5.1.1 Related works 68 5.1.2 Contributions 68 5.2 Mechanism and dynamics 69 5.2.1 Mechanism 69 5.2.2 Platform dynamics 70 5.3 Fail-safe flight strategy 75 5.3.1 Fail-safe flight method 75 5.3.2 Hardware condition for single motor fail-safe flight 80 5.4 Controller design 83 5.4.1 Faulty motor detection 83 5.4.2 Controller design 84 5.4.3 Attitude dynamics in fail-safe mode 86 5.5 Experiment result 90 5.5.1 Experimental settings 90 5.5.2 Stability and control performance review 92 5.5.3 Flight results 93 6 Conclusions 96 Abstract (in Korean) 107Docto

Probablistic approaches for intelligent AUV localisation

This thesis studies the problem of intelligent localisation for an autonomous underwater vehicle (AUV). After an introduction about robot localisation and specific issues in the underwater domain, the thesis will focus on passive techniques for AUV localisation, highlighting experimental results and comparison among different techniques. Then, it will develop active techniques, which require intelligent decisions about the steps to undertake in order for the AUV to localise itself. The undertaken methodology consisted in three stages: theoretical analysis of the problem, tests with a simulation environment, integration in the robot architecture and field trials. The conclusions highlight applications and scenarios where the developed techniques have been successfully used or can be potentially used to enhance the results given by current techniques. The main contribution of this thesis is in the proposal of an active localisation module, which is able to determine the best set of action to be executed, in order to maximise the localisation results, in terms of time and efficiency

A COLREGs-Compliant Decision Support Tool to Prevent Collisions at Sea

Groundings and collisions still represent the highest percentage of marine accidents despite the current attention on Maritime Education and Training and the improvement of sensor capability. Most of the time, a collision is caused by a human error with consequences ranging from moderate to severe, with a substantial impact on both environment and life safeguarded at sea. In this paper, a brief statistical data regarding human element as a root cause of marine incidents together with collision regulations misunderstanding is presented as a background chapter. Furthermore, the present work discusses a decision support system architecture to suggest an appropriate action when the risk of a potential collision is detected. The proposed architecture system is based on various modules integrated with proper sensor input data regarding the surrounding navigation area. As a result, the tool can support the Officers of Watch in the decision‐making process providing an early suggestion in compliance with the COLlision REGulations. The proposed system is intended to be used onboard independently from the degree of automation of the ship, and it is based on AIS, which is mandatory, making it widely applicable. The proper use of the system can considerably reduce the number of collisions, as demonstrated by the obtained results

Barrier Lyapunov function-based adaptive fuzzy attitude tracking control for rigid satellite with input delay and output constraint

This paper investigates the adaptive attitude tracking problem for the rigid satellite involving output constraint, input saturation, input time delay, and external disturbance by integrating barrier Lyapunov function (BLF) and prescribed performance control (PPC). In contrast to the existing approaches, the input delay is addressed by Pade approximation, and the actual control input concerning saturation is obtained by utilizing an auxiliary variable that simplifies the controller design with respect to mean value methods or Nussbaum function-based strategies. Due to the implementation of the BLF control, together with an interval notion-based PPC strategy, not only the system output but also the transformed error produced by PPC are constrained. An adaptive fuzzy controller is then constructed and the predesigned constraints for system output and the transformed error will not be violated. In addition, a smooth switch term is imported into the controller such that the finite time convergence for all error variables is guaranteed for a certain case while the singularity problem is avoided. Finally, simulations are provided to show the effectiveness and potential of the proposed new design techniques

A multirobot platform based on autonomous surface and underwater vehicles with bio-inspired neurocontrollers for long-term oil spills monitoring

This paper describes the BUSCAMOS-Oil monitoring system, which is a robotic platform consisting of an autonomous surface vessel combined with an underwater vehicle. The system has been designed for the long-term monitoring of oil spills, including the search for the spill, and transmitting information on its location, extent, direction and speed. Both vehicles are controlled by two different types of bio-inspired neural networks: a Self-Organization Direction Mapping Network for trajectory generation and a Neural Network for Avoidance Behaviour for avoiding obstacles. The systems’ resilient capabilities are provided by bio-inspired algorithms implemented in a modular software architecture and controlled by redundant devices to give the necessary robustness to operate in the difficult conditions typically found in long-term oil-spill operations. The efficacy of the vehicles’ adaptive navigation system and long-term mission capabilities are shown in the experimental results.This work was partially supported by the BUSCAMOS Project (ref. 1003211003700) under the program DN8644 COINCIDENTE of the Spanish Defense Ministry, the “Research Programme for Groups of Scientific Excellence at Region of Murcia” of the Seneca Foundation (Agency for Science and Technology of the Region of Murcia-19895/GERM/15)”, and the Spanish Government’s cDrone (ref. TIN2013-45920-R) and ViSelTR (ref. TIN2012-39279) projects

The Mercury-Redstone Program

The Mercury-Redstone program is reviewed as to its intended mission and its main results. The progressive results of unmanned, animal, and manned flights of this over-all Project Mercury ballistic training program are presented. A technical description of the major spacecraft systems is presented with some analysis of flight performance. Performance of the spacecraft with and without pilot input is discussed. The influence of the astronaut as an operating link in the over-all system is presented, and relative difficulties of manned versus unmanned flight are briefly commented upon. The program provided information on man as an integral part of a space flight system, demonstrating that man can assume a primary role in space as he does in other realms of flight. The Mercury-Redstone program demonstrated that the Mercury spacecraft was capable of manned space flight, and succeeded in partially qualifying the spacecraft for orbital flight