195
Proportional control (P)
The control quantity in proportion to the deviation cannot only rely on P control to eliminate steady-state
error.
Integral control (I)
The control quantity in proportion to the deviation integral value can eliminate steady-state error, but it
cannot control sharp change.
Differential control (D)
The control quantity in proportion to the deviation change rate can predict the change tendency of the
deviation, quickly response to sharp change and improve dynamic performance, but it is vulnerable to
interference, so use D control only when necessary. The PID control block diagram is as shown in Fig.
6-67.