1. Chapter - Continuous Control
Examples

2. A Feedback Controller

3. Continuous Feedback - Logical Output

4. Ladder Logic Example

5. Block Diagram

6. An Example

7. Continuous Feedback and Output

8. Proportional Control Equations

9. Modeling Behavior with Differential Equations

10. Implementing the controller in ladder logic

11. Proportional Integral Differential (PID) Control

12. PID Control With Ladder Logic

13. PID CONTROL AND STATUS BITS
pid.CTL:DINT
pid.EN:BOOL - the PID function is enabled and running
pid.PVT:BOOL -
pid.DOE:BOOL - 0=d/dtPV; 1=d/dtError
pid.SWM:BOOL - 0 = automatic, 1 = manual
pid.MO:BOOL
pid.PE:BOOL - 0=independent PID eqn; 1=dependent
pid.NDF:BOOL - 0=no derivative smoothing; 1=derivative smoothing
pid.NOBC:BOOL - 0=no bias calculation, 1=yes
pid.NOZC:BOOL - 0=no zero crossing calculation; 1=yes
pid.INI:BOOL - 0=not initialized; 1=initialized
pid.SPOR:BOOL - 0=setpoint not out of range, 1=within
pid.OLL:BOOL - 0=above minimum CV limit; 1=outside
pid.OLH:BOOL - 0=below maximum CV limit; 1=inside
pid.EWD:BOOL - 0=error outside deadband; 1=error inside
pid.DVNA:BOOL - 0=ok; 1=Error is below lower limit
pid.DVPA:BOOL - 0=ok; 1=Error is above upper limit
pid.PVLA:BOOL - 0=ok; 1=PV is below lower limit
pid.PVHA:BOOL - 0=ok; 1=PV is above upper limit

14. PID CONTROL REALS pid.SP:REAL – setpoint
pid.KP:REAL - proportional gain
pid.KI:REAL - integral gain
pid.KD:REAL - derivative gain
pid.BIAS:REAL - feed forward bias
pid.MAXS:REAL - maximum scaling
pid.MINS:REAL - minimum scaling
pid.DB:REAL - deadband
pid.SO:REAL - set output percentage
pid.MAXO:REAL - maximum output limit percentage
pid.MINO:REAL - minimum output limit percentage
pid.UPD:REAL - loop update time in seconds
pid.PV:REAL - scaled PV value
pid.ERR:REAL - scaled Error value
pid.OUT:REAL - scaled output value
pid.PVH:REAL - process variable high alarm
pid.PVL:REAL - process variable low alarm
pid.DVP:REAL - positive deviation alarm
pid.DVN:REAL - negative deviation alarm
pid.PVDB:REAL - process variable deadband alarm
pid.DVDB:REAL - error alarm deadband
pid.MAXI:REAL - maximum PV value
pid.MINI:REAL - minimum PV value
pid.TIE:REAL - tieback value for manual control
pid.MAXCV:REAL - maximum CV value
pid.MINCV:REAL - minimum CV value
pid.MINTIE:REAL - maximum tieback value
pid.MAXTIE:REAL - minimum tieback value
pid.DATA:REAL[17] - temporary and workspace (e.g. integration sums)‏
PID
CONTROL
REALS