E.3.1 Objective

This exercise will introduce the integral control action of controllers. Special emphasis is given to the task of eliminating the remaining offset term of proportional control. It will also show the slower control action of integral control, compared with proportional control. Figure Ex. 2.1 (see Exercise 2) shows an example for closed loop control.

Ex. 3.1: Flow controller detail display for I-control

E.3.2 Operation

Call up the training application single flow loop. After this exercise has been called up, press F3 to get the detail display of the flow controller.

To prepare the controller for I-control only, set K to 0, T _INT to 1 and T _DER to 0. K= 0 causes the controller to switch to integral control only, using a unit gain of 1 for integral only. Gain for proportional and derivative control action is 0, as the detail display shows (see Figure Ex. 3.1).

To study I-control, change SPE from 300 (60% of range) to 125 (25% of range) as shown in Figure Ex. 3.2. Then change SPE back to 300 (A value of 310 has been used to create Figure Ex. 3.3).

Ex. 3.2: Integral control trend (SPE 300 to 150)

Ex. 3.3: Integral control trend (SPE 150 to 310)

E.3.3 Observation

It is observed, with integral control, that the PVE value settles down exactly at the value of SPE. No offset is left, as would have been with proportional control only. It can also be observed...