In last nearly a hundred years although PID control has been used and proved to be an
efficient controlling method by many industries, yet the PID is difficult to deal with some
sophisticated systems such as second and higher order systems, long time-lag systems,
during set point change and/or load disturbance circumstance etc. The PID principle is
based on a mathematic modeling which is obtained by tuning the process. Unfortunately ,
many systems are too complex to describe in numerical terms precisely. In addition,
these systems may be variable from time to time. In order to overcome the imperfection
of PID control, the Fuzzy Technology is introduced. What is the Fuzzy Control ? It works
like a good driver. Under different speeds and circumstances, he can control a car well
with experiences he had before and does not require the knowledge of kinetic theory of
motion. The Fuzzy Logic is a linguistic control which is different from the numerical PID
control. It controls the system by experiences and does not need to simulate the system
precisely as been controlled by PID.
In last nearly a hundred years although PID control has been used and proved to be an
efficient controlling method by many industries, yet the PID is difficult to deal with some
sophisticated systems such as second and higher order systems, long time-lag systems,
during set point change and/or load disturbance circumstance etc. The PID principle is
based on a mathematic modeling which is obtained by tuning the process. Unfortunately ,
many systems are too complex to describe in numerical terms precisely. In addition,
these systems may be variable from time to time. In order to overcome the imperfection
of PID control, the Fuzzy Technology is introduced. What is the Fuzzy Control ? It works
like a good driver. Under different speeds and circumstances, he can control a car well
with experiences he had before and does not require the knowledge of kinetic theory of
motion. The Fuzzy Logic is a linguistic control which is different from the numerical PID
control. It controls the system by experiences and does not need to simulate the system
precisely as been controlled by PID.
UM25001C
5
Digital communications RS-485, RS-232 or 4 - 20 mA retransmission are available as an
additional option. These options allow BTC-2500 to be integrated with supervisory control
system and software, or alternatively drive remote display, chart recorders or data-
loggers.
Digital communications RS-485, RS-232 or 4 - 20 mA retransmission are available as an
additional option. These options allow BTC-2500 to be integrated with supervisory control
system and software, or alternatively drive remote display, chart recorders or data-
loggers.
Three kinds
1.
2.
3.
of method can be used to program BTC-2500.
Use keys on front panel
to program the unit manually,
Use a PC and setup software to program the unit via
RS-485 or RS-232 COMM port and
Use P11A, a hand-held programmer, to program
the unit via programming port.
Three kinds
1.
2.
3.
of method can be used to program BTC-2500.
Use keys on front panel
to program the unit manually,
Use a PC and setup software to program the unit via
RS-485 or RS-232 COMM port and
Use P11A, a hand-held programmer, to program
the unit via programming port.
PROCESS
PID
FUZZY
MV
PV
_
+
SV
+
+
Fuzzy Rule
Fuzzy Inference
Engine
Defuzzifier
Fuzzifier
Digital
information
Language
information
Digital
information
Figure 1.1
Fuzzy PID System Block
Figure 1.1
Fuzzy PID System Block
The function of Fuzzy Logic is to adjust PID parameters internally in order to make
manipulation output value MV more flexible and adaptive to various processes.
The function of Fuzzy Logic is to adjust PID parameters internally in order to make
manipulation output value MV more flexible and adaptive to various processes.
PID + Fuzzy Control has been proven to be an efficient method to improve the control
stability as shown by the comparison curves below:
PID + Fuzzy Control has been proven to be an efficient method to improve the control
stability as shown by the comparison curves below:
The Fuzzy Rule may work like these:
If temperature difference is large, and temperature rate is large, then
MV is large.
If temperature difference is large, and temperature rate is small, then
MV is small.
The Fuzzy Rule may work like these:
If temperature difference is large, and temperature rate is large, then
MV is large.
If temperature difference is large, and temperature rate is small, then
MV is small.
PID + FUZZY CONTROL
PID + FUZZY CONTROL
