3 Functional description of the structure switches
3.10 Other functions of the standard controller
Manual
SIPART DR21
C73000-B7476-C143-08
115
The controller is designed for PI and PID-behavior, therefore Kp, tn and for PID tv are calcu-
lated, whereby the derivative gain is fixed at 5. A prerequisite is that the D-element is con-
nected with xd/x/x1 (S47 = 0 or 2).
In S-controllers the response threshold AH is calculated in addition to Kp, tn, tv. The para-
meters tA and tE and tP/tM must be set beforehand according to the actuating drives used
(see chapter 6.3 page183 ). If the transient time T
95
is in the vicinity of 2 tP/tM (actuating
time), overshoots may also occur in controller designs with D-part even at S48=1.
In 1st order controlled systems a PI or PID controller design, in 2nd order syst ems a PID
controller design cannot be implemented according to the absolute value optimum because
in these cases Kp goes to 1. A controller design is made in which the ratio of system time
constant to control circuit constant is 3 (S48 = 1) or 10 (S48 = 2).
The new parameters for PI-controllers and for PID-controllers are offered when adaptation
has been completed.
In addition the determined system order 1 to 8 is displayed as a suffix to the PI- or
PID-identification.
The operating technique of the adaptation procedure is described in chapter 5.4.3, page
156, the commissioning explained in chapter 6.5, page 186.
3.10 Other functions of the standard controller
3.10.1 Adaptive filter
The control difference xd is fed through an adaptive filter. By adjusting tF (onPA) from oFF to
1 s the filter is switched on. By further increases to tF* the filter can be adapted to a low-fre-
quency disturbance frequency (seconds- to hours time-constant). Within a band in which
changes occur repeatedly, changes are interpreted as a fault by the filter and filtered with the
preset time constant tF, changes in a direction out of the band are passed unfiltered to the
PI(D)-algorithm to enable a faster control. If the disturbance level changes in time, the filter is
automatically adapted to the new level.
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