The PID parameters determined by the above procedures are rough values. If the control results using the above values
are unsatisfactory, the following rules may be used to further adjust the PID parameters:
Effects of PID adjustments on process response:
17
Adjustment Sequence
Symptom
Solution
Proportional Band (P)
PB
Slow response
Decrease PB
High overshoot or oscillations
Increase PB
Integral Time (I)
TI
Slow response
Decrease TI
Instability or oscillations
Increase TI
Derivative Time (D)
TD
Slow response or oscillations
Decrease TD
High overshoot
Increase TD
PV
Time
P action
Perfect
PB too high
PB too low
Set point
PV
Time
I action
Perfect
TI too low
TI too high
Set point
PV
Time
D action
Perfect
TD too high
TD too low
Set point
