Control Systems - 1

Mason's Gain Formula

Mason's Gain Rule:

Mason's gain formula is a method for finding the transfer function of a linear signal-flow graph.

Let us consider a system,

Mason’s gain rule is given by:

1) Find the forward paths and their gains:

A forward path is a path from R(s) to C(s) that does not cross the same point more than once.  There are two forward paths in this example, so we have a j = 1 and a j = 2.  The two paths are:

2) Find the loops and their gains:

A loop is a closed path that can be negotiated without crossing the same point  more than once.  There are five loops in this example:

3) Find the Δjs:

4) Find Δ:

 Since there are no non touching loop pairs in this example, D will just be one minus the sum of the loop gains:

The Solution: