Fine Tuning V1 - Siemens SIMATIC S7-1200 Function Manual

Using PID_3Step
5.3 PID_3Step V1
5.3.2.3

Fine tuning V1

Fine tuning generates a constant, limited oscillation of the process value. The PID
parameters are optimized for the operating point from the amplitude and frequency of this
oscillation. All PID parameters are recalculated on the basis of the findings. PID parameters
from fine tuning usually have better master control and disturbance behavior than PID
parameters from pretuning.
PID_3Step automatically attempts to generate an oscillation greater than the noise of the
process value. Fine tuning is only minimally influenced by the stability of the process value.
The PID parameters are backed up before being recalculated.
The setpoint is frozen during fine tuning.
Requirement
● The PID_3Step instruction is called in a cyclic interrupt OB.
● ManualEnable = FALSE
● The motor transition time has been configured or measured.
● The setpoint and the process value lie within the configured limits (see "Process value
settings" configuration).
● The control loop has stabilized at the operating point. The operating point is reached
when the process value corresponds to the setpoint.
● No disturbances are expected.
● PID_3Step is in inactive mode, automatic mode or manual mode.
Process depends on initial situation
Fine tuning proceeds as follows when started in:
● Automatic mode
Start fine tuning in automatic mode if you wish to improve the existing PID parameters
using controller tuning.
PID_3Step will regulate using the existing PID parameters until the control loop has
stabilized and the requirements for fine tuning have been met. Only then will fine tuning
start.
● Inactive or manual mode
Pretuning is always started first. The PID parameters established will be used for
adjustment until the control loop has stabilized and the requirements for fine tuning have
been met. Only then will fine tuning start.
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Function Manual, 03/2017, A5E35300227-AC
PID control