Chapter 15. The PID functions
15-8
15.2.1.5
Forward / Reverse action
1) PID control has two kind of action, forward action and reverse action. The forward
action makes the PV reaches to SV by outputting a positive MV when the PV is less
than SV.
2) A diagram in which forward and reverse actions are drawn using MV, PV and SV is
shown as Fig. 2.9.
Fig. 2-9 MV of forward / reverse action
3) Fig 2.10 shows examples of process control by forward and reverse actions,
respectively.
Fig. 2-10 PV of forward / reverse action
Reverse action
Forward action
