AnnexF/pid_st.txt
author Mario de Sousa <msousa@fe.up.pt>
Fri, 20 Apr 2018 17:38:09 +0100
changeset 1071 7fd69f29320a
parent 0 fb772792efd1
permissions -rwxr-xr-x
fix backup/restore functions: now also backup/restore programs instantiated to run inside tasks.
 FUNCTION_BLOCK PID
   VAR_INPUT
     AUTO : BOOL ;        (* 0 - manual , 1 - automatic *)
     PV : REAL ;          (* Process variable *)
     SP : REAL ;          (* Set point *)
     X0 : REAL ;          (* Manual output adjustment - *)
                          (* Typically from transfer station *)
     KP : REAL ;          (* Proportionality constant *)
     TR : REAL ;          (* Reset time *)
     TD : REAL ;          (* Derivative time constant *)
     CYCLE : TIME ;       (* Sampling period *)
   END_VAR
   VAR_OUTPUT XOUT : REAL; END_VAR
   VAR ERROR : REAL ;        (* PV - SP *)
       ITERM : INTEGRAL ;    (* FB for integral term  *)
       DTERM : DERIVATIVE ;  (* FB for derivative term *)
   END_VAR
   ERROR := PV - SP ;
   (*** Adjust ITERM so that XOUT := X0 when AUTO = 0 ***)
   ITERM (RUN := AUTO, R1 := NOT AUTO, XIN := ERROR,
          X0 := TR * (X0 - ERROR), CYCLE := CYCLE) ;
   DTERM (RUN := AUTO, XIN := ERROR, CYCLE := CYCLE) ;
   XOUT := KP * (ERROR + ITERM.XOUT/TR + DTERM.XOUT*TD) ;
 END_FUNCTION_BLOCK