Neuro-Fuzzy Control for Semi-active Dampers - Fuzzy Modeling and Control: Theory and Applications - page 169

the case of semi-active dampers it is only necessary to change structural damper
parameters that require lesser amount of power. Moreover, this low energy sup-
port contributes to make the semi-active control system more stable compared to
the active control strategies. In spite of these advantages, it is important to remark
that the control strategy is implemented by indirect actions over the semi-active
damper. Hence, the devised control strategies tend to be of higher complexity. In last
years, several researchers have proposed new control strategies based on Fuzzy or
Neuro-Fuzzy approaches (Marichal et al. 2010 ; Sun et al. 2005 ) in order to solve this
major drawback.
In this chapter, two particular vibration problems are presented. The reduction
of helicopter vibrations will be treated in Sect. 9.2 Within this field, an increasing
number of researchers are being attracted to the use of semi-active dampers, given the
fact that low consumption is a necessary requirement in this kind of applications. The
reduction of vibrations appearing in civil structures will also be treated in Sect. 9.3 .
More in particular, this analysis will be applied to the particular case of vibrations
appearing on pedestrian bridges. In this case, a different method to diminish the
vibrations will be shown, using Tuned Mass Dampers (TMD) instead of isolator
devices between the vibration source and the target system.
9.2 Semi-active Dampers for Vibration Control
in Autonomous Helicopters
Nowadays, autonomous helicopters play an essential role in surveillance and rescue
tasks both for civilian or military purposes. Due to their great maneuverability in open
environments where other aerial vehicles are more difficult to be used, they repre-
sent a very convenient type of vehicle to be employed for certain tasks. Apart from
other sensor systems, a camera is one of the most common devices to be installed
on board autonomous helicopters. However, the performance of these cameras can
be seriously compromised by an intrinsic high vibration level that increases the dif-
ficulty in carrying out proper image processing. These vibrations are originated at
different sources but more in particular, main/tail rotor systems, engine and trans-
mission (Anusonti-Inthra 2002 ). Although other efforts have been made in order to
reduce vibrations in other elements of helicopters such as passengers' seats (Hiemenz
et al. 2008 ), this section of the chapter is focused in reducing vibrations when using
sensor devices.
Many efforts have been devoted to solve the problem of reducing the vibration
levels in sensors installed on board autonomous helicopters. The main approach is to
isolate these sensors from the mentioned vibration sources. A first approach consists
in the inclusion of passive elements, such as tuned-mass absorbers, isolators and blade
design optimizations. These elements offer the advantage of avoiding external power
to operate. However, passive elements offer a fixed design, being unable to be adjusted
to any possible change in flight operations. On the other hand, active elements for