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- calculation and permanent saving of parameters (Pb, Ti, Td to the selected PID and Tc set, i.e. PEr1/2/3 , chapter
8),
- switching on the control for a given output with new PID settings
The program can discontinue the autotuning b or c (with the EtP1/2/3 message) in the following situations:
- the initial value of PV is higher than the setpoint SP for heating or lower than the setpoint for cooling,
- the SP setpoint has been changed or the measured value of the PV process changes too quickly or too slowly,
- the maximum tuning time (4 hours) has been exceeded
It is recommended to restart the autotuning b or c after a significant change in the SP threshold or the
parameters of the control object (eg heating/cooling power, batch mass, initial temperature, etc.).
Autotuning does not work in program control (process controller) and valve control (servo) mode.
9.5. CORRECTION OF PID PARAMETERS
The autotuning function correctly selects the PID regulation parameters for most processes, but sometimes it may
be necessary to correct them. Due to the strong interdependence of these parameters (described in chapters 9.3
and 8, Table 8), only one of them should be changed and the impact on the process should be observed:
a) oscillation around the threshold - increase the proportional band Pb, increase the integration time Ti , decrease
differentiation time Td , (or reduce the pulse period of the output by half, parameter Tc )
b) slow response - reduce the Pb proportional band, Td differentiation time and Ti integration time
c) overshoot - increase the Pb proportional band, Td differentiation time and Ti integration time
d) instability - increase the integration time Ti.
9.6. PROGRAMMED WORK CHARACTERISTICS. SAMPLE CONFIGURATION.
The controller allows you to create a control program (process controller) consisting of a maximum of 6 segments
(3 stages configured with the parameters described in chapter 8, Table 8, point V). Each stage (1/2/3) operates in
accordance with the control parameters of the assigned setpoint SP (1/2/3), description in Table 8, point II.
A program can be assigned to any of the control outputs (1/2/3) with parameter 9/16/23: ctY1/2/3 set to the value
PrGc. Additionally, it is possible to define an auxiliary output ( PrGA ), which can be useful for signaling the
operating status for individual program stages as well as for switching on additional devices (fans, additional
heating sections, etc.) with the manual operation option (when parameter 52/57/62/63: ASt/1/2/3/E = hAnd).
The program starts at the moment of starting the control (automatically after switching on the power or manually
using the [F], [SET] function keys or the BIN binary input programmed as the start/stop of outputs, chapter 7.1)
and is always performed from the beginning (1st stage/segment). Successive stages of the process (1/2/3) are
signaled by the messages Pr-1/2/3 appearing every few seconds, alternately with the current setpoint SP (or other
programmed parameter 73: dibo) and optionally with the remaining stage time (in hh: mm format with m or 00:
ss unit when time<1min, without unit). During the countdown, the upper right dot flashes (chapter 7, point d). The
program ends with message PEnd and switching off the control output.
Diagram of an exemplary program configuration
Fig.9.6. Diagram of a sample program
consisting of 4 segments for the heatingtype
control (Fvn1/2/3 = indH) is presented in the
diagram on the right. At the start of the process
(control) , the initial setpoint for segment 1 is the
current measured value (PV
0
, e.g. 25°C), target
setpoint SP
C
= Set1 , which is achieved with the
rate (slope) N1 = GrA1 (e.g. 25°C/ min). After
reaching the SP
C
value and control at this level by the T2 time set for the 2nd segment = tiM1, the move to the 3rd
section takes place, for which the cooling function with the speed N3 =GrA2 is provided
(e.g. -10°C/min) up to SP
K level
= Set2. During cooling, an auxiliary output can be used to switch on e.g. a fan. The
program is stopped (with switching off the control output) after reaching the SP
K
and going to the 4th segment.
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