Nyquist stability analysis of a type 0 system

To perform a Nyquist stability analysis, consider a simple type 0 system with the open-loop transfer function:

as shown in the diagram below.

To generate the Nyquist plot

1.    Create the above diagram using a const, transferFunction, and plot block.

2.    Enter the following polynomial coefficients to the transferFunction block:

Numerator: 1

Denominator: 1 1

Note: Always leave spaces between coefficient values.

3.    Choose System > Go, or click  in the toolbar to simulate the diagram.

4.    Select the transferFunction block.

5.    Choose Analyze > Nyquist Response.

The Nyquist plot is displayed.

6.    Drag on its borders to adjust its size.

The Nyquist plot for this system is a circle, with the real part of GH(s) on the horizontal axis and the imaginary part of GH(s) on the vertical axis. On this plot, the origin represents GH(j) and the point of intersection with the horizontal axis (Re(GH) = 1) represents GH(j0).