DA SILVA, M. T.; DA SILVA, MOISES T.; DA SILVA, MOISÉS T.; http://lattes.cnpq.br/2293553085745158; SILVA, Moisés Tavares da.
Resumo:
In this work, we present
contributions in the area of identification of systems using relay feedback.
With the aim of obtaining a
limit cycle insensitive to disturbance, a relay feedback structure is proposed
composed of a block
o to remove static disturbances
and/or drift, followed by a relay. this block
consists of a high-pass filter followed by
by a relay and an integrator. Several simulated and experimental studies are carried out
in order to verify the applicability of the proposed relay structure. Through such studies, it appears that the proposed structure is
able to generate the
symmetrical switching of the relay under disturbance at the process input, while the other structures present in the literature may not even produce a
sustained oscillation for some disturbances.
Regarding the analysis of the proposed relay structure, the descriptive function method is initially used. From this analysis, it is observed that the proposed structure has
characteristics similar to standard relay feedback. Then, the analysis based on the Poincaré map and a representation in state space is performed. As
In order to simplify the analysis of the structure of the relay under study, a structure is obtained
equivalent. For this LTI framework and systems
with and without delay, the
necessary and sufficient conditions for the existence of the
limit cycle. The local stability
of the limit cycle is investigated using the Jacobian
corresponding to the Poincaré map.
In addition, the analysis of the existence and stability of the
Limit cycle is performed from the original relay structure. In this case, the analysis is limited to systems without delay. At the
identification context
of FOPTD (First Order Plus Time Delay) models, it is
presented a technique
which uses the proposed open-loop relay structure,
with and without integrating element fed back into the loop. In addition, point information
of frequency
are used
as equality constraints to obtain the parameters
of the models. To estimate the delay, a Taylor series approximation is used.
second order and an iterative procedure. Finally,
based on two models
identified, a methodology for the phase adjustment of FOPTD models is proposed.