1,219 research outputs found
Task-space dynamic control of underwater robots
This thesis is concerned with the control aspects for underwater tasks performed by
marine robots. The mathematical models of an underwater vehicle and an underwater
vehicle with an onboard manipulator are discussed together with their associated
properties.
The task-space regulation problem for an underwater vehicle is addressed where the
desired target is commonly specified as a point. A new control technique is proposed
where the multiple targets are defined as sub-regions. A fuzzy technique is used to
handle these multiple sub-region criteria effectively. Due to the unknown gravitational
and buoyancy forces, an adaptive term is adopted in the proposed controller.
An extension to a region boundary-based control law is then proposed for an underwater
vehicle to illustrate the flexibility of the region reaching concept. In this novel
controller, a desired target is defined as a boundary instead of a point or region. For a
mapping of the uncertain restoring forces, a least-squares estimation algorithm and the
inverse Jacobian matrix are utilised in the adaptive control law.
To realise a new tracking control concept for a kinematically redundant robot, subregion
tracking control schemes with a sub-tasks objective are developed for a UVMS.
In this concept, the desired objective is specified as a moving sub-region instead of a
trajectory. In addition, due to the system being kinematically redundant, the controller
also enables the use of self-motion of the system to perform sub-tasks (drag
minimisation, obstacle avoidance, manipulability and avoidance of mechanical joint
limits)
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
A brief review of neural networks based learning and control and their applications for robots
As an imitation of the biological nervous systems, neural networks (NN), which are characterized with powerful learning ability, have been employed in a wide range of applications, such as control of complex nonlinear systems, optimization, system identification and patterns recognition etc. This article aims to bring a brief review of the state-of-art NN for the complex nonlinear systems. Recent progresses of NNs in both theoretical developments and practical applications are investigated and surveyed. Specifically, NN based robot learning and control applications were further reviewed, including NN based robot manipulator control, NN based human robot interaction and NN based behavior recognition and generation
Disturbance Observer-based Robust Control and Its Applications: 35th Anniversary Overview
Disturbance Observer has been one of the most widely used robust control
tools since it was proposed in 1983. This paper introduces the origins of
Disturbance Observer and presents a survey of the major results on Disturbance
Observer-based robust control in the last thirty-five years. Furthermore, it
explains the analysis and synthesis techniques of Disturbance Observer-based
robust control for linear and nonlinear systems by using a unified framework.
In the last section, this paper presents concluding remarks on Disturbance
Observer-based robust control and its engineering applications.Comment: 12 pages, 4 figure
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
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