Underwater Robots - Gianluca Antonelli.pdf

3. Dynamic Control of 6-DOF AUVs
3.1 Introduction
In this Chapter, the problem ofcontrolling anAutonomous Underwater Vehicle
in 6-DOFs is approached.
To effectively compensate the hydrodynamic effects several adaptive (integral)
control laws have been proposed in the literature (see, e.g., [91, 93, 97,
152, 319]). In[126], anumber ofadaptive control actions are proposed, where
the presence of an external disturbance is taken into account and its counteraction
isobtained bymeans of aswitching term; simulation on the simplified
three-DOF horizontal model of NEROV are given. In [121], abody-fixedframe
based adaptive control law isdeveloped. In [314], an adaptive control
law based onEuler angle representation of the orientation has been proposed
for the control of an AUV; planar simulations are provided to show the effectiveness
of the proposed approach. Reference [184] proposes aself-adaptive
neuro-fuzzy inference system that makes use of a5-layer-structured neural
network to improve the function approximation. In [175] afuzzy membership
function based-neural network is proposed; the control’s membership functions
derivation isachieved by aback propagation network.
Generally speaking, the performance achievable from the application of
adaptive control laws has been validated only by means of reduced-order simulations;
on the other hand, six-DOF experimental results are seldom presented
in the literature [299]. References [34, 35, 122, 126] describe six-DOF
control laws in which the orientation is described bythe use of quaternions.
The papers [34, 35, 84, 215, 216, 323] report six-DOF experimental results
on the underwater vehicle ODIN (Omni-Directional Intelligent Navigator).
An experimental work is given in [269, 270] by the use of the Johns Hopkins
UniversityROV on asingle DOF. Differentsimple control laws are tested
on the vehicle in presence ofmodel mismatching and thruster saturation and
their performance is evaluated.
Among the other hydrodynamic effects acting on arigid body moving in a
fluid, the restoring generalized forces (gravity plus buoyancy) and the ocean
current are of major concern in designing amotion control law for underwater
vehicles, since they are responsible of steady-state position and orientation
errors. However, while the restoring generalized forces are usually dealt with
in the framework of adaptive dynamic compensations, only few papers take
G. Antonelli: Underwater Robots, 2nd Edition, STAR 2, pp. 45–77, 2006.
© Springer-Verlag Berlin Heidelberg 2006