bộ điều khiển Pi Fuzzy
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FuzzyPID Controllers vs. FuzzyPI Controllers M. Santos*, S. Dormido**, J. M. de la Cruz* *Dpto. de Informática y Automática. Facultad de Físicas. (UCM) **Dpto. de Informática y Automática. Facultad de Ciencias. (UNED) Ciudad Universitaria s/n. 28040MADRID (Spain). FAX: (34)13944687 email: msantos@eucmax.sim.ucm.es Abstract The synthesis of a control system includes both the controller selection and the adjustment of its parameters. In some cases, the type of controller might be more complex or more general, like PID instead PI or PD, to improve the control system performance. In all cases, the tuning problem must be satisfactorily solved. On the other hand, Fuzzy Control has made possible the establishment of intelligent control. However, Fuzzy Logic Controllers (FLC) are only used in simple configurations and their analytic knowledge is still poor. In this paper, a quantitative and qualitative study of fuzzy controllers is done for the most complete case of a FuzzyPID. The FLCPID analytic performance is summarized in terms of its three input variables, which allows us to obtain initial values for the FLCPID scale factors in terms of the classical PID parameters. This initial tuning has been tested for several systems and a qualitative tuning has also been established. The advantages of the derivative term are also examined. 1. Introduction The need for simple advanced control alternatives especially arises in the Control Process area, where most of the real processes are generally complex and difficult to model [1]. The application of Fuzzy Logic to a wide range of control applications has made possible the establishment of intelligent control in these areas [4], [5]. Its appeal, from the Process Control Theory point of view, lies in the fact that this technique provides a good support for translating the heuristic knowledge of the skilled operator, expressed in linguistic terms, into computer algorithms. Fuzzy Control solves real problems, previously not tackled due to their complexity or to lack of information [9]. However, Fuzzy Logic Controllers (FLC) are usually applied with poor analytic knowledge of their behavior and only in simple configurations. In fact, they normally perform like PI or PD. FLCPI controllers are quite simple, though they are the most widely used in practice and provide similar results to conventional controllers. But in some applications it may be useful to employ more general controllers, which make it easier to re...
FuzzyPID Controllers vs. FuzzyPI Controllers
M. Santos*, S. Dormido**, J. M. de la Cruz*
*Dpto. de Informática y Automática. Facultad de Físicas. (UCM)
**Dpto. de Informática y Automática. Facultad de Ciencias. (UNED)
Ciudad Universitaria s/n. 28040MADRID (Spain). FAX: (34)13944687
email: msantos@eucmax.sim.ucm.es
Abstract
The synthesis of a control system includes both the
controller selection and the adjustment of its parameters.
In some cases, the type of controller might be more
complex or more general, like PID instead PI or PD, to
improve the control system performance. In all cases, the
tuning problem must be satisfactorily solved. On the other
hand, Fuzzy Control has made possible the establishment
of intelligent control. However, Fuzzy Logic Controllers
(FLC) are only used in simple configurations and their
analytic knowledge is still poor. In this paper, a
quantitative and qualitative study of fuzzy controllers is
done for the most complete case of a FuzzyPID. The
FLCPID analytic performance is summarized in terms of
its three input variables, which allows us to obtain initial
values for the FLCPID scale factors in terms of the
classical PID parameters. This initial tuning has been
tested for several systems and a qualitative tuning has
also been established. The advantages of the derivative
term are also examined.
1. Introduction
The need for simple advanced control alternatives
especially arises in the Control Process area, where most
of the real processes are generally complex and difficult to
model [1]. The application of Fuzzy Logic to a wide range
of control applications has made possible the
establishment of intelligent control in these areas [4], [5].
Its appeal, from the Process Control Theory point of view,
lies in the fact that this technique provides a good support
for translating the heuristic knowledge of the skilled
operator, expressed in linguistic terms, into computer
algorithms. Fuzzy Control solves real problems,
previously not tackled due to their complexity or to lack
of information [9].
However, Fuzzy Logic Controllers (FLC) are usually
applied with poor analytic knowledge of their behavior
and only in simple configurations. In fact, they normally
perform like PI or PD.
FLCPI controllers are quite simple, though they are
the most widely used in practice and provide similar
results to conventional controllers. But in some
applications it may be useful to employ more general
controllers, which make it easier to reach the system
specifications and improve their performance, though they
can be also more difficult to tune.
The complete study of fuzzy controllers should involve
all the terms of conventional controllers. The third control
action must be included so as to consider the FLCPID
case. Though the derivative term is not commonly
included neither in the conventional case, this allows us
to complete the development of Fuzzy controllers in a
similar way that of the classical ones. It also makes it
possible to obtain certain conclusions about their stability
and specifications.
But the main problem in the synthesis of a control
system is not only the selection of a specific controller but
also the adjustment of its parameters, to verify certain
given specifications for the controlled process.
In this paper an analytic study of the FLCPID is
carried out in section 2, which allows us to establish an
equivalence between the FLCPID and a conventional
PID; thus a tuning method is proposed for these fuzzy
controllers and is then evaluated. The qualitative analysis
is done in section 3. The behavior of these controllers is
compared with the FLCPI type in section 4 and some
general conclusions are summarized in the last section.
2. Analytic study of the FLCPID controller
The aim of a controller is to reach or maintain a
process in a specific state, by monitoring a set of variables
and selecting the adequate control actions.
The FuzzyPID controller performs like its classical
homonym, but both the input variables and the control
action are given in linguistic terms. The analytic
development of fuzzy controllers allows us to explain the
influence of each tuning parameter on the system
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bộ điều khiển Pi Fuzzy

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