Design and Evaluation of a Propulsion System for Small, Compact, Low-Speed Maneuvering Underwater Vehicles

Underwater vehicles used to perform precision inspection and non-destructive evaluation in tightly constrained or delicate underwater environments must be small, have low-speed maneuverability and a smooth streamlined outer shape with no appendages. In this thesis, the design and analysis of a new propulsion system for such underwater vehicles is presented. It consists primarily of a syringe and a plunger driven by a linear actuator and uses different inflow and outflow nozzles to provide continuous propulsive force. A prototype of the proposed propulsion mechanism is built and tested. The practical utility and potential efficacy of the system is demonstrated and assessed via direct thrust measurement experiments and by use of an initial proof-of-concept test vehicle. Experiments are performed to enable the evaluation and modelling of the thrust output of the mechanism as well as the speed capability of a vehicle employing the propulsion system

Underwater Vehicles

For the latest twenty to thirty years, a significant number of AUVs has been created for the solving of wide spectrum of scientific and applied tasks of ocean development and research. For the short time period the AUVs have shown the efficiency at performance of complex search and inspection works and opened a number of new important applications. Initially the information about AUVs had mainly review-advertising character but now more attention is paid to practical achievements, problems and systems technologies. AUVs are losing their prototype status and have become a fully operational, reliable and effective tool and modern multi-purpose AUVs represent the new class of underwater robotic objects with inherent tasks and practical applications, particular features of technology, systems structure and functional properties

Autonomous robot systems and competitions: proceedings of the 12th International Conference

This is the 2012’s edition of the scientific meeting of the Portuguese Robotics Open (ROBOTICA’ 2012). It aims to disseminate scientific contributions and to promote discussion of theories, methods and experiences in areas of relevance to Autonomous Robotics and Robotic Competitions. All accepted contributions are included in this proceedings book. The conference program has also included an invited talk by Dr.ir. Raymond H. Cuijpers, from the Department of Human Technology Interaction of Eindhoven University of Technology, Netherlands.The conference is kindly sponsored by the IEEE Portugal Section / IEEE RAS ChapterSPR-Sociedade Portuguesa de Robótic

Desenvolvimento de um modelo matemático de um veículo não tripulado de subsuperfície biomimético

O acentuado crescimento da área da robótica submarina levou ao surgimento de novos modelos de veículos de subsuperfície e com eles advêm também novos desafios, nomeadamente associados à sua eficiência de propulsão e manobrabilidade. Para superar estes desafios as equipas de cientistas e investigadores usaram a natureza como inspiração, procurando replicar o modo de locomoção dos peixes através de barbatanas e caudas articuladas, introduzindo o conceito de veículos de subsuperfície com propulsão biomimética. Neste sentido, o projeto europeu SABUVIS foi iniciado pelo consórcio de países Portugal, Polónia e Alemanha, com o apoio da European Defense Agency, procurando desenvolver um cardume de veículos biomiméticos, tendo este, capacidade de cooperação entre unidades com função de líder e outras, menos capacitadas, com funções de executantes, podendo estes dispositivos ser aplicados a um vasto leque de missões. Esta dissertação encontra-se inserida no projeto supramencionado e tem como objetivo desenvolver o modelo matemático de uma unidade executante, denominada TOBIAS. Nesse sentido pretende-se calcular os correspondentes coeficientes hidrodinâmicos, modelar a sua propulsão biomimética, bem como os efeitos das barbatanas peitorais, procurando simular o seu comportamento dinâmico. Através deste modelo, será possível analisar a resposta do TOBIAS em função dos diferentes parâmetros de controlo sendo, para tal, realizadas diversas simulações numéricas tanto em cadeia aberta, verificando o seu comportamento num conjunto de manobras (carreira retilínea, curva de giração, mergulho e emersão, mergulho e emersão helicoidal), como em cadeia fechada, testando a aptidão do modelo para o desenvolvimento e implementação de algoritmos de controlo.The significant growth in the area of underwater robotics has led to the appearance of new models of underwater vehicles, and with them also come new challenges, particularly associated with their efficiency of propulsion and maneuverability. To overcome these challenges, teams of scientists and researchers used nature as inspiration, seeking to replicate the locomotion of a fish through fins and articulated tails, introducing the concept of underwater vehicles with biomimetic propulsion. In this sense, the European project SABUVIS was initiated by a consortium of countries Portugal, Poland and Germany, with the support of the European Defense Agency, attempting to develop a swarm of biomimetic vehicles, with the ability of cooperation between units with leader function and others, less capable, with executioner functions, where these devices can be applied to a wide range of missions. This work is inserted in the aforementioned project and aims to develop the mathematical model of a led unit, known as TOBIAS. Therefore, it is intended to calculate the corresponding hydrodynamic coefficients, and to model its biomimetic propulsion, as well as the effects of the pectoral fins, in an attempt to simulate its dynamic behavior. Through this model, it will be possible to analyze the performance of TOBIAS as a function of different control parameters. To validate this approach, several numerical simulations will be performed both in open loop, verifying its behavior in a set of maneuvers (forward swimming, turning circle, dive and emersion, helical dive and emersion), and in close loop, testing the suitability of the model for the development and implementation of control algorithms

분산된 로터로 구동되는 비행 스켈레톤 시스템의 디자인 상태추정 및 제어

학위논문(박사)--서울대학교 대학원 :공과대학 기계항공공학부,2020. 2. 이동준.In this thesis, we present key theoretical components for realizing flying aerial skeleton system called LASDRA (large-size aerial skeleton with distributed rotor actuation). Aerial skeletons are articulated aerial robots actuated by distributed rotors including both ground connected type and flying type. These systems have recently attracted interest and are being actively researched in several research groups, with the expectation of applying those for aerial manipulation in distant/narrow places, or for the performance with entertaining purpose such as drone shows. Among the aerial skeleton systems, LASDRA system, proposed by our group has some significant advantages over the other skeleton systems that it is capable of free SE(3) motion by omni-directional wrench generation of each link, and also the system can be operated with wide range of configuration because of the 3DOF (degrees of freedom) inter-link rotation enabled by cable connection among the link modules. To realize this LASDRA system, following three components are crucial: 1) a link module that can produce omni-directional force and torque and enough feasible wrench space; 2) pose and posture estimation algorithm for an articulated system with high degrees of freedom; and 3) a motion generation framework that can provide seemingly natural motion while being able to generate desired motion (e.g., linear and angular velocity) for the entire body. The main contributions of this thesis is theoretically developing these three components, and verifying these through outdoor flight experiment with a real LASDRA system. First of all, a link module for the LASDRA system is designed with proposed constrained optimization problem, maximizing the guaranteed feasible force and torque for any direction while also incorporating some constraints (e.g., avoiding inter-rotor air-flow interference) to directly obtain feasible solution. Also, an issue of ESC-induced (electronic speed control) singularity is first introduced in the literature which is inevitably caused by bi-directional thrust generation with sensorless actuators, and handled with a novel control allocation called selective mapping. Then for the state estimation of the entire LASDRA system, constrained Kalman filter based estimation algorithm is proposed that can provide estimation result satisfying kinematic constraint of the system, also along with a semi-distributed version of the algorithm to endow with system scalability. Lastly, CPG-based motion generation framework is presented that can generate natural biomimetic motion, and by exploiting the inverse CPG model obtained with machine learning method, it becomes possible to generate certain desired motion while still making CPG generated natural motion.본 논문에서는 비행 스켈레톤 시스템 LASDRA (large-size aerial skeleton with distributed rotor actuation) 의 구현을 위해 요구되는 핵심 기법들을 제안하며, 이를 실제 LASDRA 시스템의 실외 비행을 통해 검증한다. 제안된 기법은 1) 전방향으로 힘과 토크를 낼 수 있고 충분한 가용 렌치공간을 가진 링크 모듈, 2) 높은 자유도의 다관절구조 시스템을 위한 위치 및 자세 추정 알고리즘, 3) 자연스러운 움직임을 내는 동시에 전체 시스템이 속도, 각속도 등 원하는 움직임을 내도록 할 수 있는 모션 생성 프레임워크로 구성된다. 본 논문에서는 우선 링크 모듈의 디자인을 위해 전방향으로 보장되는 힘과 토크의 크기를 최대화하는 구속 최적화를 사용하고, 실제 적용가능한 해를 얻기 위해 몇가지 구속조건(로터 간 공기 흐름 간섭의 회피 등)을 고려한다. 또한 센서가 없는 액츄에이터로 양방향 추력을 내는 것에서 야기되는 ESC 유발 특이점 (ESC-induced singularity) 이라는 문제를 처음으로 소개하고, 이를 해결하기 위해 선택적 맵핑 (selective mapping) 이라는 기법을 제시한다. 전체 LASDRA 시스템의 상태추정을 위해 시스템의 기구학적 구속조건을 만족하는 결과를 얻을 수 있도록 구속 칼만 필터 기반의 상태추정 기법을 제시하고, 시스템 확장성을 고려하여 반 분산 (semi-distributed) 개념의 알고리즘을 함께 제시한다. 마지막으로 본 논문에서는 자연스러운 움직임의 생성을 위하여 CPG 기반의 모션 생성 프레임워크를 제안하며, 기계 학습 방법을 통해 CPG 역연산 모델을 얻음으로써 전체 시스템이 원하는 움직임을 낼 수 있도록 한다.1 Introduction 1 1.1 Motivation and Background 1 1.2 Research Problems and Approach 3 1.3 Preview of Contributions 5 2 Omni-Directional Aerial Robot 7 2.1 Introduction 7 2.2 Mechanical Design 12 2.2.1 Design Description 12 2.2.2 Wrench-Maximizing Design Optimization 13 2.3 System Modeling and Control Design 20 2.3.1 System Modeling 20 2.3.2 Pose Trajectory Tracking Control 22 2.3.3 Hybrid Pose/Wrench Control 22 2.3.4 PSPM-Based Teleoperation 24 2.4 Control Allocation with Selective Mapping 27 2.4.1 Infinity-Norm Minimization 27 2.4.2 ESC-Induced Singularity and Selective Mapping 29 2.5 Experiment 38 2.5.1 System Setup 38 2.5.2 Experiment Results 41 2.6 Conclusion 49 3 Pose and Posture Estimation of an Aerial Skeleton System 51 3.1 Introduction 51 3.2 Preliminary 53 3.3 Pose and Posture Estimation 55 3.3.1 Estimation Algorithm via SCKF 55 3.3.2 Semi-Distributed Version of Algorithm 59 3.4 Simulation 62 3.5 Experiment 65 3.5.1 System Setup 65 3.5.2 Experiment of SCKF-Based Estimation Algorithm 66 3.6 Conclusion 69 4 CPG-Based Motion Generation 71 4.1 Introduction 71 4.2 Description of Entire Framework 75 4.2.1 LASDRA System 75 4.2.2 Snake-Like Robot & Pivotboard 77 4.3 CPG Model 79 4.3.1 LASDRA System 79 4.3.2 Snake-Like Robot 80 4.3.3 Pivotboard 83 4.4 Target Pose Calculation with Expected Physics 84 4.5 Inverse Model Learning 86 4.5.1 LASDRA System 86 4.5.2 Snake-Like Robot 89 4.5.3 Pivotboard 90 4.6 CPG Parameter Adaptation 93 4.7 Simulation 94 4.7.1 LASDRA System 94 4.7.2 Snake-Like Robot & Pivotboard 97 4.8 Conclusion 101 5 Outdoor Flight Experiment of the F-LASDRA System 103 5.1 System Setup 103 5.2 Experiment Results 104 6 Conclusion 111 6.1 Summary 111 6.2 Future Works 112Docto

Intersection between natural and artificial swimmers: a scaling approach to underwater vehicle design.

Approximately 72% of the Earth’s surface is covered by water, yet only 20% has been mapped [1]. Autonomous Underwater Vehicles (AUVs) are one of the main tools for ocean exploration. The demand for AUVs is expected to increase rapidly in the coming years [2], so there is a need for faster and more energy efficient AUVs. A drawback to using this type of vehicle is the finite amount of energy that is stored onboard in the form of batteries. Science and roboticists have been studying nature for ways to move more efficiently. Phillips et al. [3] presents data that contradicts the idea that fish are better swimmers than conventional AUVs when comparing the energetic cost of swimming in the form of the Cost of Transport (COT). The data presented by Phillips et al. only applies to AUVs at higher length and naval displacement (mass) scales, so the question arises of whether an AUV built at different displacements and length scales is more efficient than biological animals and if current bio-inspired platforms are better than conventional AUVs. Besides power requirements, it is also useful to compare the kinematic parameters of natural and artificial swimmers. In this case, kinematic parameters indicate how fast the swimmer travels through the water. Also, they describe how fast the propulsion mechanism must act to reach a certain swimming speed. This research adopts the approach of Gazzola et al. [4] where the Reynolds number is associated with a dimensionless number, Swim number (Sw) in this case, that has all the kinematic information. A newly developed number that extends the swim number to conventional AUVs is the Propulsion number (Jw), which demonstrates excellent agreement with the kinematics of conventional AUVs. Despite being functionally similar, Sw and Jw do not have a one-to-one relationship. Sw, Jw, COT represent key performance metrics for an AUV, herein called performance criteria, which can be used to compare existing platforms with each other and estimate the performance of non-existent designs. The scaling laws are derived by evaluating the performance of 229 biological animals, 163 bioinspire platforms, and 109 conventional AUVs. AUVs and bio-inspired platforms have scarce data compared with biological swimmers. Only 5% of conventional and 38% of bio-inspired AUVs have kinematic data while 30% of conventional and 18% of bio-inspired AUVs have energetic data. The low amount of performance criteria data is due to the nature of most conventional AUVs as commercial products. Only recently has the COT metric been included in the performance criteria for bio-inspired AUVs. For this reason, the research here formulates everything in terms of allometric scaling laws. This type of formulation is used extensively when referring to biological systems and is defined by an exponential relationship f (x) = axb, where x is a physical parameter of the fish or vehicle, like length or displacement. Scaling laws have the added benefit of allowing comparisons with limited data, as is the case for AUVs. The length and displacement scale (physical scale) must be established before estimating the performance criteria. Scale is primarily determined by the payload needed for a particular application. For instance, surveying the water column in deep water will require different scientific tools than taking images of an oyster bed in an estuary. There is no way to identify the size of an AUV until it is designed for that application, since these scientific instruments each have their own volume, length, and weight. A methodology for estimating physical parameters using computer vision is presented to help determine the scale for the vehicle. It allows accurate scaling of physical parameters of biological and bio-inspired swimmers with only a side and top view of the platform. A physical scale can also be determined based on the vehicle’s overall volume, which is useful when determining how much payload is needed for a particular application. Further, this can be used in conjunction with 3D modeling software to scale nonexistent platforms. Following the establishment of a physical scale, which locomotion mode would be most appropriate? Unlike conventional AUVs that use propeller or glider locomotion, bio-inspired platforms use a variety of modes. Kinematics and energy expenditures are different for each of these modes. For bio-inspired vehicles, the focus will be on the body-caudal fin (BCF) locomotion, of which four types exist: anguilliform, carangiform, thunniform, and ostraciiform. There is ample research on anguilliform and carangiform locomotion modes, but little research on thunniform and ostraciiform modes. In order to determine which locomotion mode scales best for a bio-inspired AUV, this research examines the power output and kinematic parameters for all four BCF modes. In order to achieve this, computational fluid dynamics simulations are performed on a 2D swimmer for all four modes. Overset meshes are used in lieu of body-fitted meshes to increase stability and decrease computational time. These simulations were used to scale output power over several decades of Reynolds numbers for each locomotion mode. Carangiform locomotion was found to be the most energy efficient, followed by anguilliform, thunniform, and ostraciiform. In order to utilize the above scaling laws in designing a novel platform, or comparing an existing one, there must be a unifying framework. The framework for choosing a suitable platform is presented with a case study of two bio-inspired vehicles and a conventional one. The framework begins by determining how the platform can be physically scaled depending on the payload. Based on the physical scale and derived scaling laws, it then determines performance criteria. It also describes a method for relative cost scaling for each vehicle, which is not covered in the literature. The cost scaling is based on the assumption that all payloads and materials are the same. The case study shows that a conventional AUV performs better on all performance criteria and would cost less to build

Contribution to the model and navigation control of an autonomous underwater vehicle

This thesis deals with the further development of an existing underwater vehicle for autonomous navigation. The vehicle was conceived to navigate over the sea surface and, at certain fixed points, to dive vertically in order to obtain a profile of a water column. The main objectives of the thesis are the improvement of the hardware and software of the vehicle in order to make it fully operational, and the design and implementation of control techniques for autonomous navigation. The problem of autonomous navigation is addressed first with the calculation of an hydrodynamic model in 3DoF. An extensive study about the selection of the coefficients is performed, using a linearized model. The calculation of the coefficients is done using two approaches: a geometric one and another one based on least squares techniques applied to experimental data obtained during sea trials. The least squares method gives satisfactory results and the simulations fits the experimental data. The resulting hydrodynamic model is completed with the physical constraints of the actuators of the vehicle. Solving the autonomous navigation problem requires the design of controllers for both the inner loop (dynamic) and the outer loop (kinematic). Several solutions based on type-1 TSK fuzzy control are presented for velocity control, yaw control, pure pursuit navigation, and path following. The fuzzy controller is used to manage different linear controllers designed for specific conditions. The hydrodynamic model plays an important role in the design of the controller for the inner loop. In addition, a gain scheduled controller is designed to validate a particular case of the fuzzy controller in the inner loop. Regarding the finishing of the vehicle to be fully operational, the improvements begin with a new driver for the lateral thrusters because they lacked backwards movement capability. Additionally, upgrades in the handling of the vehicle had to devised. In this respect, a wireless on/off system is presented to power the vehicle, and a WiFi connection is adapted to manipulate the software of the vehicle remotely. Furthermore, a study of the currents and power of the immersion system in order to reduce the power consumption is performed, and the hardware is improved with the inclusion of some commercial devices, like an IMU, CTD, and acoustic localization system. The software is improved in several aspects. First, some problems derived from previous works are debugged. The system is then restructured with a multithread development, which provides robustness and modularity. As the system needed an extension of the protocol communication for easy handling, a robust protocol communication is implemented with the possibility to execute scripts. Finally, the existing graphical user interface is simplified in order to provide only the information required by the operator. In order to improve the buoyancy of the vehicle, several foams are designed, adjusted to the geometry of the vehicle, and a ballast system is also included for fine adjustment. Finally, several tests in the laboratory, a swimming pool, a channel, and at sea are performed in order to check the performance of the vehicle. Results show a correct behavior of hardware and software, and also validate the performance of the controllers designed for autonomous navigation.Esta tesis aborda el desarrollo de un vehículo submarino existente para la navegación autónoma. El vehículo fue concebido para navegar sobre la superficie del mar siguiendo ciertos puntos preestablecidos, y hacer inmersiones verticales con el fin de obtener un perfil de una columna de agua. Los objetivos principales de la tesis son la mejora del hardware y el software del vehículo con el fin de que sea plenamente operativo, y el diseño e implementación de técnicas de control para la navegación autónoma. El problema de la navegación autónoma se aborda primero con el cálculo de un modelo hidrodinámico en 3 grados de libertad. Un extenso estudio sobre la selección de los coeficientes se realizó usando un modelo linealizado. El cálculo de los coeficientes se obtuvo utilizando dos enfoques: primero un enfoque geométrico, y luego un enfoque basado en técnicas de mínimos cuadrados aplicados a los datos experimentales obtenidos durante las pruebas de mar. El método de mínimos cuadrados da resultados satisfactorios y las simulaciones se ajustan a los datos experimentales. El modelo hidrodinámico resultante se completa con las limitaciones físicas de los actuadores del vehículo. Resolver el problema de navegación autónoma requiere el diseño de controladores tanto para el lazo interno (dinámico) como el lazo exterior (cinemático). En este sentido se presentan varias soluciones basadas en controladores difusos TSK tipo 1 para el control de velocidad, control de guiñada, navegación "pure pursuit", y "path following". El controlador difuso se utiliza para gestionar diferentes controladores lineales diseñados para condiciones específicas, y el modelo hidrodinámico juega un papel importante en el diseño del controlador del lazo interno. Además, se diseñó un controlador tipo "gain scheduling" para validar un caso particular del controlador difuso. En cuanto a poner el vehículo completamente operativo, las mejoras comienzan con un nuevo controlador para los propulsores laterales pues éstos carecían del movimiento en reversa. Adicionalmente se realizaron varias mejoras respecto a la fácil manipulación del vehículo. En este sentido se implementó un sistema inalámbrico para el encendido y apagado del vehículo, y se adaptó una conexión WiFi para poder manipular el software remotamente. Luego, se realizó estudio de las corrientes y voltajes implicados en el sistema de inmersión con el fin de reducir el consumo de energía, y finalmente el hardware se mejora con la inclusión de algunos dispositivos comerciales como un IMU, CTD, y sistema de localización acústica. El software se mejora en varios aspectos. En primer lugar, algunos de los problemas derivados de desarrollos anteriores se depuran. A continuación, el sistema se reestructura con un desarrollo multi-hilo que proporciona robustez y modularidad. Debido a que el sistema necesitaba la extensión del protocolo de comunicación para un fácil manejo, se implementó un protocolo de comunicación robusto con la posibilidad de ejecutar scripts. Por último, se simplifica la interfaz gráfica de usuario existente con el fin de proporcionar solamente la información necesaria para el operador. Con el fin de mejorar la flotabilidad del vehículo, se diseñan varias espumas ajustadas a la geometría del vehículo, y también se incluye un sistema de lastre para un ajuste fino. Por último, se hicieron varias pruebas en laboratorio, piscina, un canal, y en el mar con el fin de comprobar el rendimiento del vehículo. Los resultados muestran un comportamiento correcto de hardware y software, y también validan el funcionamiento de los controladores diseñados para la navegación autónoma

Unified Dynamics and Control of a Robot Manipulator Mounted on a VTOL Aircraft Platform

An innovative type of mobile manipulator, designated Manipulator on VTOL (Vertical Take-Off and Landing) Aircraft (MOVA), is proposed as a potential candidate for autonomous execution of field work in less-structured indoor and outdoor environments. Practical use of the MOVA system requires a unified controller that addresses the coupled and complex dynamics of the composite system; especially the interaction of the robotic manipulator with the aircraft airframe. Model-based controller design methods require explicit dynamics models of the MOVA system. Preliminary investigation of a two-dimensional MOVA system toward a dynamics model and controller design is presented in preparation for developing the controller of the more complex MOVA system in 3D space. Dynamics of the planar MOVA system are derived using the Lagrangian approach and then transforming the result into a form that facilitates controller design using the concept of a virtual manipulator. A MOVA end-effector trajectory tracking controller was designed with the transformed dynamics equation using the integrator back-stepping control design framework. Validity of the controller is shown via stability analysis, simulation results, and results from a physical test-bed. A systematic approach is illustrated for the derivation of the 3D MOVA system dynamics equations. The resulting dynamics equations are represented abstractly in the standard robot dynamics form and proven to have the skew-symmetric property, which is a useful property for control derivation. An open source Mathematica program was developed to achieve automatic symbolic derivation of the MOVA system dynamics. Accessory tools were also designed to create a tool-chain that starts with an Autodesk Inventor CAD drawing, generates input to the Mathematica program, and then formats the output for direct use in MATLAB and Simulink. A unified nonlinear control algorithm that controls the 3D MOVA system, including both the aircraft and the onboard manipulator, as a single entity was developed to achieve trajectory tracking of the MOVA end-effector position and attitude based on the explicit dynamics equation. Globally Uniformly Ultimately Bounded (GUUB) stability is proven for the controller using Lyapunov-type stability analysis. Physical testing was constructed in order to to demonstrate the performance of the proposed controller on a MOVA system with a two-link onboard manipulator