The Applet below shows PD control of type 0 and 1 systems, compares P and PD control for a type 1 system and illustrates the relative contributions of the P and D controllers to the output for the type 0 system.

The P controller output is proportional to the error while the D controller output is proportional to the rate of change of the error.

For P control increasing K reduces the rise time but increases the overshoot and oscillatory behaviour. With PD the P controller works as with P control but now the D controller provides an additional variable T

Open and Closed loop Transfer function for type 1 is

G(s) = K(1 + KTd)/(s(T1s + 1)), C(s)/R(s) = K(1 + KTd)/(T1s

And for type 0 is

G(s) = K(1 + KTd)/((T1s + 1)(T2s + 1)), C(s)/R(s) = K(1 + KTd)/(T1T2s

Gif image below show how the applet should appear.

COPYRIGHT © 2006 Cuthbert Nyack.