Graphical solution of servo problems

MANY SERVOMECHANISMS can be represented by the block diagram shown below with A´s and B´s equal to 1. It is frequently necessary to extend the frequency bandwidth over which the output is approximately equal to the input and to decrease the difference between the input and output of the servomechanism by modification of the system. This may be accomplished by inserting lag and lead networks for A´s and B´s in the block diagram, respectively. The design problem is then one of determining the circuit parameters of the lead and lag networks.