Similarly, you can represent parallel connection of ‘n’ blocks with a single block. The transfer function of this single block is the algebraic sum of the transfer functions of all those ‘n’ blocks.
Feedback Connection
As we discussed in previous chapters, there are two types of feedback — positive feedback and negative feedback. The following figure shows negative feedback control system. Here, two blocks having transfer functions G(s)G(s) and H(s)H(s) form a closed loop.
The output of the summing point is –
Shifting Summing Point Before the Block
Consider the block diagram shown in the following figure. Here, the summing point is present after the block.
Block Diagram Algebra for Take-off Points
There are two possibilities of shifting the take-off points with respect to blocks −
- Shifting take-off point after the block
- Shifting take-off point before the block
Let us now see what kind of arrangements are to be done in the above two cases, one by one.
Shifting Take-off Point After the Block
Consider the block diagram shown in the following figure. In this case, the take-off point is present before the block.
Shifting Take-off Point Before the Block
Consider the block diagram shown in the following figure. Here, the take-off point is present after the block.
