87. Block Diagrams of Control Systems

A table has been prepared of the equivalent conversions of the basic elements and transfer elements used when writing the block diagram of a control system.

(1) Basic elements of block diagrams

Element Block diagram Description

Transfer elements
(Blocks)

With the input being X(s) and the output being Y(s)
Y(s)=G(s)ｷX(s)
G(s): Transfer function

Branching point

Only the signal X(s) is taken out and the value is the same.

Combining point

Addition of signals
Y(s) =X1(s)+[±X2(s)]=X1(s)±X2(s)

Signal line

Signal flow. The arrow mark indicates the direction of the signal.

(2) Equivalent conversion of a block diagram

Type Before conversion After conversion

Series connection

Parallel connection

Feedback control

Combining point

Branching point