S7-1200 FT_PIWL

oscat.lib fuer Step 7
1

(* initialize at power_up )
IF NOT #init OR #RST THEN
#init := TRUE;
#in_last := #IN;
#t_last := “T_PLC_US”();
#i := 0.0;
#tc := 0.0;
ELSE
( read last cycle time in Microseconds )
#tx := “System_Time_DB”.us_dw;
#tc := 1000.0/1024.0DINT_TO_REAL(DWORD_TO_DINT(#tx) - DWORD_TO_DINT(#t_last));
#t_last := #tx;

(* calculate proportional part *)
#p := #KP * #IN;

(* run integrator *)
#i := (#IN + #in_last) * 5.0E-7 * #KI * #tc + #i;
#in_last := #IN;

(* calculate output Y *)
#Y := #p + #i;

(* check output for limits *)
IF #Y >= #LIM_H THEN
    #Y := #LIM_H;
    IF #KI <> 0.0 THEN  
        #i := #LIM_H - #p; 
    ELSE
        #i := 0.0;
    END_IF;
    #LIM := TRUE;
ELSIF #Y <= #LIM_L THEN
    #Y := #LIM_L;
    IF #KI <> 0.0 THEN 
        #i := #LIM_L - #p; 
    ELSE
        #i := 0.0;
    END_IF;
    #LIM := TRUE;
ELSE
    #LIM := FALSE;
END_IF;

END_IF;

(* revision history
hm 13. jun. 2008 rev 1.0
original version

hm 27. oct. 2008 rev 1.1
integrator will not be adjusted when ki = 0

hm 25. jan 2009 rev 1.2
module will also work with negative K

hm 11. mar. 2009 rev 1.3
real constants updated to new systax using dot
*)