Explanation of formula variables
Meaning of the variables in the following formulas:
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Variable
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Meaning
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is the time differential between the current cycle and the previous cycle
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System deviation (SP - PV)
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System deviation value from the current sampling step
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System deviation value from the previous sampling step
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FEED_FWD
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Disturbance variable
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Value of controlled variable from the current sampling step
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Value of controlled variable from the previous sampling step
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Y
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current output (halt mode) or YMAN (manual mode)
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YD
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D component
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YI
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I component
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YP
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P component
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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 and automatic are located 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_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:
YD = 0
