User manual - CONTROLLER PUR-94D
Configuring the PID controller
The PID controller can be configured in two ways: manually and automatically.
In manual mode, the user defines all factors and additional elements of the controllers
(fuzzy logic, inertia, output limiting and dead zone) at their own discretion. The settings chosen
by the device in automatic mode can also be improved and fine-tuned. The user can disable
each block of the PID controller as well as additional blocks. This is done by setting the zero
value or
OFF
option in the selected parameter.
In automatic mode, in the auto-tuning process using the
Ziegler-Nichols
method, the
device calculates and tunes the parameters
P, I
and
D
of
one of the controller’s loops.
Additional blocks (fuzzy logic, inertia, output limiting and dead zone) are not configured in this
mode and the user must choose them himself according to respective applications. The auto-
tuning process is described later in this chapter.
Fuzzy logic block (FuZL submenu)
Step changes in the setpoint can be mitigated by the use of the fuzzy logic block, which
inserts speed control of the setpoint change. Thanks to its application the user may dictate
how quickly a fuzzy value approximates the target value in the process (
SEtP
).
This feature is particularly useful in systems where too rapid change in the setpoint and,
as it is possible in such a situation, the control signal, could lead to unwanted behaviour on the
part of a object, for instance destruction of the product being manufactured. It is also possible
to set the minimum difference between the setpoint (
SEtP
), and the fuzzy setpoint, beyond
which the controller step changes the fuzzy setpoint to the setpoint (
SEtP
). This is defined by
the
HYST
parameter. Both controllers use the same settings of the fuzzy logic block.
Figure 6.8. Comparison of the PID-H controller’s response to a change in the setpoint using
and without the use of fuzzy logic
25
0
20
40
60
80
100
120
140
160
180
200
0
20
40
60
80
100
120
PID-H control loop
FuZL on
FuZL off
time
se
tp
oi
nt
Histeresis
