Detailed formulas
Original instructions
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Explanation of formula variables
Meaning of the variables in the following formulas:
Variable
Meaning
Time differential between the present cycle and the previous cycle
System deviation (SP - PV)
System deviation value from the current sampling step
System deviation value from the previous sampling step
BIAS
Disturbance variable
Value of controlled variable from the current sampling step
Value of controlled variable from the previous sampling step
Y
current output (halt mode) or YMAN (manual mode)
YD
D component
YI
I component
YP
P component
Manipulated variable
The manipulated variable consists of various terms which are dependent on the operating mode:
After summation of the components manipulated variable limiting takes place, so that:
Overview of the calculation of the control components
Following this an overview on the different calculations of the control components in relation to the inputs EN_P, EN_I and EN_D can be found:
P component YP for all operating modes
YP for manual, halt and automatic modes is determined as follows:
For EN_P = 1 the following applies:
For EN_P = 0 the following applies:
I component YI for automatic mode
YI for automatic mode is determined as follows:
For EN_I = 1 the following applies:
For EN_I = 0 the following applies:
The I component is formed according to the trapezoid rule.
I component YI for manual and halt modes
YI for manual, halt and automatic modes is determined as follows:
For EN_I = 1 the following applies:
For EN_I = 0 the following applies:
D component YD for automatic mode
YD for automatic mode and cascade is determined as follows:
For EN_D = 1 and D_ON_X = 0 the following applies:
For EN_D = 1 and D_ON_X = 1 the following applies:
For EN_D = 0 the following applies:
D component YD for manual and halt modes
YD for manual, halt and automatic modes is determined as follows:
YD = 0