|The requirements to the process for the tool Siemens PID Self-tuner:||Advantages of CHAR-PID-2S:|
|The process should have the asymptotic time response with the steady time of delay/ This requirements excludes the processes with the oscillate time response and astatic processes.||The process may have the stable oscillate characteristic. The astatic processes are allowed.|
|The comparative small values of time delay||The time delay is up to 50% of maximal time constant|
|The small disturbances in the heat processes. The adequate quality of measured signals in the sense of sufficiently large coefficient “signal-noise”||The large external disturbance effected to the process are allowed|
The model of the controlled plant is described in the article . The external disturbance that interfered to the mode l is the negative impulse:
The plots of control process are shown below.
Process of tuning consists of four steps. On the first step, plant is controlled in manual mode (frequently, for example in the heating process, the plant is in “cold” state )
On the second step, the constant is applied to the input of the plant in the open-loop system. The program of automatic tuning monitors the output of the plant and searches the point of inflextion (, , ), This is the moment when the step response reaches maximal slope.
The program for controller was developed using IDE Siemens TIA Porta that allows to develop the program for lower level as well as the operator terminal (SCADA). The main part of the program is the interrupt function that executes all main calculations.
The program is realized as the one stream because the calculation formulae is simple
The program code is written using SCL language. The SCL is the extension of ST language for industrial controllers of standard IEC 1131.
The model of the plant is described in :
We tested the controllers for the case when the external disturbance was absent.
The system is stable after tuning.
The tuning has been successfully finished, the system is stable after tuning.