RESEARCH SUBJECTS
The research activities of Paolo Castaldi include:
1.Development of new Fault Detection and Isolation (FDI)
methodologies for general aviation aircrafts, UAVs and satellites
(2005-today)
2.Development of new Active Fault Tolerant Control (AFTC)
methodologies for general aviation aircrafts, UAVs and satellites
(2006-today)
3.Development of methodologies for landing in wind shear conditions
(2011-today)
4.Development of new methodologies for the identification of static
and dynamic Errors-in-variables (EIV) models through the
application of ARAIM for GPS/GALILEO (2004-today)
5.Theoretical development and application of new adaptive filtering
algorithms for the estimation of the parameters and of the state of
induction engines (2004-today)
6.Development and application of Control, Identification and Fault
Detection schemes to generic real processes (2005- today (some
topic))
RESEARCH TOPIC 1:
•Development of a new linear and polynomial FDI methodology for the
aircraft I/O sensors. This approach is based on the development of
a residual generator bank and it has been compared with "classical"
FDI methods based on residual generator banks developed by means of
neural networks or Unknown Input Kalman Filters. Such comparison
has been carried out both in case of decoupled and coupled
longitudinal and latero-directional dynamics. Particular attention
has been paid to methodology robustness: the diagnostic residual
generators are decoupled from wind (turbulence and wind gust) and
robust against model uncertainties. Finally, the above-described
comparison has been made by means of a nonlinear flight simulator
including the model of sensors, actuators, turbulence and wind
gusts. These simulations have highlighted the superior performances
of the proposed approach with respect to the linear techniques
presented in literature.
•Development of a new FDI scheme based on the Nonlinear Geometric
Approach (NLGA). For the first time in literature a NLGA scheme for
a 6 DoF (Degree of Freedom) aircraft model has been proposed,
taking also in account the nonlinear engine dynamic and a
longitudinal dynamic coupled with the lateral one. This FDI
methodology is characterized by residual generators decoupled from
wind (turbulence and wind gust) and robust against both critical
model errors and parametric uncertainties, due to an inaccurate
knowledge of the flight condition. Such decoupling is achieved
through the identification of subsystems which are affected by the
considered fault and not affected by the other faults and
disturbances to be decoupled. On the base of this subsystem it is
possible to design residuals which are affected only by the
considered fault. The obtained filters have been tested on a flight
simulator, including the model of sensors, actuators, turbulence
and wind gust model, and compared with filters developed by means
of Neural Networks or Unknown Input Kalman Filters. The better
achievable performance,s have shown the effectiveness of the
proposed algorithm.
•The above described research work has led to the design not only
of a FDI unit, but also of a more general FDD (Fault Detection and
Diagnosis) unit based on the NLGA (NLGA-FDD). Such unit provides
not only the fault detection and isolation, but also the fault
estimation in the time domain thus resulting in the development of
research topic 2 (see below), i.e. an Active Fault Tolerant Control
(AFTC) system based on the NLGA (NLGA-AFTC). In fact, it is
possible to achieve the compensation of the fault, affecting
satellite or aircraft actuators, by means of a further feedback
loop based on the fault estimation. A peculiarity of the proposed
scheme is that the fault estimation, thanks to the NLGA, is
decoupled from the disturbances affecting the system (wind for
aircrafts and gravitational and aerodynamic fields for satellites).
Such result allows to obtain an asymptotically unbiased and robust
fault estimation, and therefore the rejection of the fault
itself.
RESEARCH TOPIC 2:
The NLGA-AFTC approach is conceptually suitable for both aircrafts
and spacecrafts and also for generic benchmark systems, as shown in
the most recent papers on journals with high IF and invited
sessions in international congresses. In particular, by means of
the the benchmark, a comparison with Sliding Mode Control (SMC),
has shown the better achievable performances of NLGA-AFTC, in
particular during the transitory phases following faults
occurrence.
•Different NLGA-FDD units decoupled from wind gusts and turbulence
have been developed for airplanes and UAVs characterised by 6 DoF
models, or UAVs characterised by 3 DoF models. In particular, it
has been shown how FDD filters are characterized by different
structures depending on the considered model. Nevertheless this
investigation has shown how the theoretical base of the NLGA has to
be generalized to not affine models. This is a very challenging
aspect not present in literature. The achieved results for the
NLGA-AFTC have been demonstrated to be better with respect to the
ones achievable from other FTC methodologies.
•A NLGA-FTC scheme has been developed also for spacecrafts. In this
case, for the first time in literature, the decoupling of the fault
estimation (and so of the AFTC scheme) from gravitational and
aerodynamic disturbances, particularly significant for Low Orbit
satellites (about 500-800 km), has been obtained. A peculiarity of
this approach is that, for example air density in case of
aerodynamic disturbance, could be unknown. This allows to apply the
methodology for planets with uncertain atmospheric information. In
particular, it has been shown that the minimum detectable fault
size by means of the NLGA-FDD unit is lower than that one obtainble
by other methods. This fact allows to design NLGA-AFTC system which
allows to reject the fault, even in case where other FTC schemes do
not apply fault rejection.
The result of the above described research topics have been
presented in many journals with high IF and have several citations.
Moreover the topics have been proposed in a large number of regular
or invited participations to international congresses. Finally
topic 1 and 2 have been the subject of two plenary talk.
RESEARCH TOPIC 3:
The approach has been published in 2 papers and consists in
considering the wind-shear (WS) components as faults, and therefore
in obtaining WS compensation through an AFTC scheme. The added
value with respect to actual literature and the commercial
autopilots is important. Fyrther investigation will regard the
proof of the stability of the overal control system
RESEARCH TOPIC 4:
Starting from my theoretical results in Errors-In-Variables (EIV)
system identification, published on high IF Journal, a diagnosis
method has been developed, aiming to detect the presence of faults
on pseudorange measurements coming from a GPS/GALILEO system. The
EIV approach, assuming that all the variables are affected by
errors, allows to obtain more estimations of the same fault. By
means of coherency conditions between the different estimations, I
have demonstrated how it is possible to identify the fault size and
the faulty satellite. The redundancy due to the availability of
multiple estimations of the same parameter in the EIV environment
lends a greater robustness to the method, compared to the classical
FDI methods based on a single least square estimation. This allows
to isolate with more confidence the faulty satellite and to obtain
a more accurate estimation of the actual position.
RESEARCH TOPIC 5:
With reference to this subject, about which some papers have been
published on journals with high IF, it is worth observing that the
presented theoretical methodologies have been applied to induction
motors. On the other hand , it is wort observing that the
theoretical methodology can be applied and generalised to aerospace
systems.
•In particular, a new adaptive observer for parameter estimation in
an induction motor at standstill has been developed. The method is
based on a new canonical form and on a new observer gain law. The
main innovation, with reference to the state of the art, lies in
the parallel type structure of the observer, particularly robust
against noises affecting data.
•Moreover, a new adaptive observer different from the previous one,
based on a new canonical form and characterised by a
serial-parallel structure, has been developed.
Both the algorithms have been tested with success on the induction
motors available at the Laboratorio di Automatica e Robotica (LAR)
of the university of Bologna.
RESEARCH TOPIC 6:
Paolo Castaldi has developed and then applied several
identification and filtering techniques:
•Blind Identification for communication channels. The usually
adopted techniques are based on assumptions not congruent with the
real case (assumption of white noises with the same variance
affecting the signals). A new methodology has been proposed, which
is based on techniques developed for the identification of
errors-in-variables models. This extends the results presented in
literature since it allows to identify systems which are corrupted
by additive noises with different variances and characterised by
low signal-to-noise ratios.
•A very important and innovative application, presented on a high
IF journal, has been the exploitation of the eigenvector method for
the identification of the time constants of the relaxation curve of
a NMR signal (Nuclear Magnetic Resonance) in the study of the
features of porous mediums.
•An exhaustive investigation on modeling and tracking problems for
moving objects in noisy environment has been carried out, in
collaboration with ITALTEL s.p.a. (Milan).
•A diagnosis methodology for railroad switch faults has been
developed within a CNR project, in collaboration with SABIS s.p.a.
(now ALSTOM s.p.s.) in Bologna.
