3 research outputs found
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
Planejamento de movimento de sistemas robóticos de intervenção subaquática baseado na teoria dos helicoides
Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia MecânicaOs veÃculos subaquáticos não tripulados (ou UUV, do inglês Unmanned Underwater Vehicles) são responsáveis pela execução de grande parte das operações em ambientes imersos. Os sistemas veÃculo-manipulador subaquáticos (ou UVMS, do inglês Underwater Vehicle-Manipulator Systems) são UUV voltados para a execução de tarefas de intervenção. Além de aplicações em missões cientÃficas e de resgate, os UVMS são muito usados em instalações offshore de extração/distribuição de petróleo e gás em tarefas de construção, manutenção, inspeção e operação. A maioria dos sistemas de intervenção subaquática é teleoperada devido à s dificuldades de operação no ambiente imerso e à s caracterÃsticas cinemáticas e dinâmicas dos UVMS. A evolução desses sistemas de intervenção subaquática envolve o desenvolvimento de sua autonomia. Um requisito básico para isso é a capacidade do sistema planejar as ações necessárias para realizar as tarefas a ele especificadas. Esta tese estuda o planejamento de movimento dos UVMS durante a execução de tarefas de intervenção. Este problema consiste em definir os movimentos que o sistema (veÃculo e manipuladores) deve realizar para executar as tarefas especificadas atendendo à s restrições impostas pelo espaço de trabalho. O trabalho utiliza a análise cinemática baseada na teoria dos helicoides, teoria dos grafos e ferramentas derivadas para definir modelos cinemáticos dos UVMS em diferentes cenários de execução de tarefas de intervenção. A cooperação entre manipuladores de um mesmo UVMS e entre dois ou mais UVMS é estudada, assim como a variabilidade dos modelos cinemáticos em função de mudanças no contexto da operação. A partir da análise realizada, define-se uma sistematização da modelagem cinemática dos sistemas de intervenção por componentização, visando facilitar e automatizar esse processo. Um framework computacional é projetado para facilitar a implementação desses modelos. Com base nesses resultados, define-se uma estrutura geral para o desenvolvimento de estratégias de planejamento de movimento. Simulações de uso dessa estrutura em diferentes cenários de operação são apresentadas. Assim, este trabalho contribui para a autonomia de UUV/UVMS, considerada o principal objeto de pesquisa da área e que no caso dos sistemas de intervenção subaquática reduzirá custos de operação, além de possibilitar o uso destes em novas missões.Unmanned Underwater Vehicles (UUV, for short) are used in most immerse operations. Underwater Vehicle-Manipulator Systems (UVMS, for short) are a particular kind of UUV designed for intervention tasks. Besides their application in scientific and rescue missions, UVMS are much used in offshore oil and gas extraction/distribution facilities for construction, maintenance, inspection and operation tasks. Most underwater intervention systems are teleoperated due the operational difficulties in the immerse environment and the UVMS kinematic/dynamic features. The evolution of these underwater intervention systems involves the development of their autonomy. The system ability to plan the necessary actions to perform its assigned tasks is a basic requirement for that. This thesis studies the motion planning of UVMS while executing intervention tasks. The problem consists of defining the motion that the system (vehicle and manipulators) must do to execute the specified taks while complying with the workspace imposed restrictions. A computational framework is designed to aid the implementation of these models. A general structure to the developed of motion planning strategies based on these results is defined. Simulations using this strucute in different operation scenarios are presented. So, this work contributes to the autonomy of UUV/UVMS, which is considered a major research field and it will reduce operation costs of underwater intervention systems, besides allowing their use in new missions