Detailed formulas
Original instructions
About us
Explanation of formula variables
Meaning of the variables in the following formulas:
Variable
Meaning
Time differential between the present cycle and the previous cycle
The current internally formed System deviation
System deviation value from the current sampling step
System deviation value from the previous sampling step
FEED_FWD
Disturbance (only in P, D or PD controllers)
OFF
Offset
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 (only when en_d = 1)
YI
I component (only when en_i= 1)
YP
P component (only when en_p= 1)
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
The following is an overview on the different calculations of the control components in relation to the elements en_p, en_i and en_d:
P component YP for all operating mode
YP for manual, halt, automatic and cascade 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 and cascade mode
YD for automatic mode and cascade is determined as follows:
For en_d = 1 and d_on_pv = 0 the following applies:
For en_d = 1 and d_on_pv = 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: