LSIS Master-K K200S - Integral Operation (I Action)

Chapter 15 The PID function of K200S MASTER-K
15-4
15.2.2 Integral operation (I action)
1) With integ ral operation, the manipulate value (MV) is increased or decreased
continuously in accordance time in order to eliminate the deviation between the SV and PV.
When the deviation is very small, the proportional operation can not produce a proper
manipulate value and an offset remains between PV and SV. In other hand, the integral
operation can eliminate the offset value even the deviation is very small.
2) The period of the time from when the deviation has occurred in I action to when the MV
of I action become that of P action is called integration time and represented as Ki.
3) Integral action when a constant deviation has occurred is shown as the following Fig.
15.4.
Fig. 15.4 The integral action with constant deviation
4) The expression of I action is as following;
As shown in the expression, integral action can be made stronger or weaker by adjusting
integration time (Ki) in I action.
That is, the more integration time (the longer integration time) as shown in Fig. 15.5, the
less quantity added to or subtracted from the MV and the longer time is needed to make
PV reached the SV.
As shown in Fig. 15.6, when the integration time given is short the PC will approach the
SV in short time since the quantity added or subtracted become increased. However, if
the integration time is too short, a oscillation may occur. Therefore, the proper P and I
value is requested for stability of control system.
∫
= Edt
Ti
Kp
MV