Coupled and decoupled force/motion controllers for an underwater vehicle-manipulator system

Autonomous interaction with the underwater environment has increased the interest of scientists in the study of control structures for lightweight underwater vehicle-manipulator systems. This paper presents an essential comparison between two different strategies of designing control laws for a lightweight underwater vehicle-manipulator system. The first strategy aims to separately control the vehicle and the manipulator and hereafter is referred to as the decoupled approach. The second method, the coupled approach, proposes to control the system at the operational space level, treating the lightweight underwater vehicle-manipulator system as a single system. Both strategies use a parallel position/force control structure with sliding mode controllers and incorporate the mathematical model of the system. It is demonstrated that both methods are able to handle this highly non-linear system and compensate for the coupling effects between the vehicle and the manipulator. The results demonstrate the validity of the two different control strategies when the goal is located at various positions, as well as the reliable behaviour of the system when different environment stiffnesses are considered

Modelling and control of lightweight underwater vehicle-manipulator systems

This thesis studies the mathematical description and the low-level control structures for underwater robotic systems performing motion and interaction tasks. The main focus is on the study of lightweight underwater-vehicle manipulator systems. A description of the dynamic and hydrodynamic modelling of the underwater vehicle-manipulator system (UVMS) is presented and a study of the coupling effects between the vehicle and manipulator is given. Through simulation results it is shown that the vehicle’s capabilities are degraded by the motion of the manipulator, when it has a considerable mass with respect to the vehicle. Understanding the interaction effects between the two subsystems is beneficial in developing new control architectures that can improve the performance of the system. A control strategy is proposed for reducing the coupling effects between the two subsystems when motion tasks are required. The method is developed based on the mathematical model of the UVMS and the estimated interaction effects. Simulation results show the validity of the proposed control structure even in the presence of uncertainties in the dynamic model. The problem of autonomous interaction with the underwater environment is further addressed. The thesis proposes a parallel position/force control structure for lightweight underwater vehicle-manipulator systems. Two different strategies for integrating this control law on the vehicle-manipulator structure are proposed. The first strategy uses the parallel control law for the manipulator while a different control law, the Proportional Integral Limited control structure, is used for the vehicle. The second strategy treats the underwater vehicle-manipulator system as a single system and the parallel position/force law is used for the overall system. The low level parallel position/force control law is validated through practical experiments using the HDT-MK3-M electric manipulator. The Proportional Integral Limited control structure is tested using a 5 degrees-of-freedom underwater vehicle in a wave-tank facility. Furthermore, an adaptive tuning method based on interaction theory is proposed for adjusting the gains of the controller. The experimental results show that the method is advantageous as it decreases the complexity of the manual tuning otherwise required and reduces the energy consumption. The main objectives of this thesis are to understand and accurately represent the behaviour of an underwater vehiclemanipulator system, to evaluate this system when in contact with the environment and to design informed low-level control structures based on the observations made through the mathematical study of the system. The concepts presented in this thesis are not restricted to only vehicle-manipulator systems but can be applied to different other multibody robotic systems

A survey on uninhabited underwater vehicles (UUV)

ASME Early Career Technical Conference, ASME ECTC, October 2-3, 2009, Tuscaloosa, Alabama, USAThis work presents the initiation of our underwater robotics research which will be focused on underwater vehicle-manipulator systems. Our aim is to build an underwater vehicle with a robotic manipulator which has a robust system and also can compensate itself under the influence of the hydrodynamic effects. In this paper, overview of the existing underwater vehicle systems, thruster designs, their dynamic models and control architectures are given. The purpose and results of the existing methods in underwater robotics are investigated

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

A Unified Task Priority Control Framework Design for Autonomous Underwater Vehicles

In this thesis, we investigate the problem of bringing various behaviours of Autonomous Underwater Vehicles under a common control framework. Thereby, we propose a unified guidance and control framework for AUVs based on the task priority control approach. This incorporate various behaviors such as path following, terrain following, obstacle avoidance, as well as homing and docking to stationary and moving docking stations. The integration of homing and docking maneuvers into the task priority framework is thus a novel contribution of this thesis. This integration allows, for example, to execute homing maneuvers close to uneven seafloor or obstacles, ensuring the safety of the AUV by giving the highest priority to the safety tasks. Furthermore, the proposed approach tackles a wide range of scenarios without ad hoc solutions. Indeed, the proposed approach is well suited for both the emerging trend of resident AUVs, which stay underwater for a long period inside garage stations, exiting to perform inspection and maintenance missions and homing back to them, and for AUVs that are required to dock to moving stations such as surface vehicles, or towed docking stations. The proposed techniques are further studied in a simulation setting, taking into account the rich number of aforementioned scenarios

Análise cinemática via quatérnios duais aplicada a um sistema veículo-manipulador subaquático

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Automação e Sistemas, Florianópolis, 2011Este trabalho propõe metodologias para a análise cinemática de sistemas veículo-manipulador subaquáticos (UVMS) através de quatérnios duais com o intuito de impor menor variação de torque nas juntas durante o seguimento de trajetória. Em adição a isso, evita-se a ocorrência de singularidades cinemáticas e obtém-se menor custo computacional. A abordagem é apresentada inicialmente como uma alternativa à representação tradicional dos movimentos aplicada na cinemática direta de mecanismos através da convenção de Denavit-Hartenberg e do método dos helicoides sucessivos. O benefício dessa representação está no menor custo computacional, mas principalmente, no desacoplamento dos ângulos de orientação de forma a evitar as singularidades cinemáticas. Os quatérnios duais também são aplicados na cinemática inversa em uma metodologia interativa através do método de Davies como uma modalidade de realimentação livre de singularidades. Por fim, a principal contribuição deste trabalho está na proposta da aplicação dos quatérnios duais na cinemática inversa diferencial em por uma metodologia analítica, através da apresentação do Jacobiano dual-quaterniônico. Essas abordagens são aplicadas a um sistema subaquático, onde o amortecimento imposto pela imersão no fluido dissipa grandes variações de torque e agrega erros no seguimento da trajetória.This work proposes a methodology for kinematic analysis of underwater vehicle-manipulator systems (UVMS) using dual-quaternions. The objective is to provide a less joint torque variation to trajectory tracking, avoidance of kinematic singularities occurrence and a lower computational cost. The approach is initially presented as an alternative representation of movements applied to direct kinematics through the Denavit- Hartenberg convention and the successive screws method. The benefit of this representation is a lower computational cost, but mainly, the decoupling of orientation angles in order to avoid kinematic singularities. The dual quaternions also are applied in the inverse kinematics in an interactive approach through Davies method as a feedback without singularities. Finally, the main contribution of this work is the proposal of dual quaternions application in an analytical approach of differential inverse kinematics through of the dual-quaternionic Jacobian. These approaches are applied to an underwater system, where the damping imposed by fluid immersion dissipates large torque variations adding errors in trajectory tracking