PLC Programming

Appendix D: CoDeSys Libraries
A P-controller is easily generated by setting TV to a fixed value of 0.
PID
The PID controller function block:
Unlike the PD controller, this function block contains a further DWORD input TN for the readjusting
time in msec.
The output, the manipulated variable (Y) is again of type REAL, and contains, unlike the PD controller,
an additional integral part:
Y = KP ⋅ (∆ + 1/TN ∆(t)dt + TV δ∆/δt) + Y_OFFSET
The PID controller can be easily converted to a PI controller by setting TV=0.
Because of the additional integral part, an overflow can come about by incorrect parameterization of
the controller, if the integral of the error ∆ becomes too great. Therefore for the sake of safety a
BOOLean output called OVERFLOW is present, which in this case would have the value TRUE. At
the same time, the controller is suspended and will only be activated again by re-initialization.
10.17.5 Signal Generators...
BLINK
The function block BLINK generates a pulsating signal. The input consists of ENABLE of the type
BOOL, as well as TIMELOW and TIMEHIGH of the type TIME. The output OUT is of the type BOOL.
If ENABLE is set to TRUE, BLINK begins, to set the output for the time period TIMEHIGH to TRUE,
and then afterwards to set it for the time period TIMELOW to FALSE.
Example in CFC:
GEN
The function generator generates typical periodic functions:
The inputs are a composition consisting of MODE from the pre-defined counting type GEN_MODE,
BASE of the type BOOL, PERIOD of the type TIME, of two INT values CYCLES and AMPLITUDE and
of the BOOLean RESET input.
The MODE describes the function which should be generated, whereby the enumeration values
TRIANGLE and TRIANGLE_POS deliver two triangular functions, SAWTOOTH_RISE an ascending,
CoDeSys V2.3 10-55