Plot Nyquist Didactic

A very simple function to understand Cauchy's argument principle and Nyquist Stability Criterion with 4 preprogrammed contours.

A didactic plot to understand and to present the Cauchy's argument principle (complex Mapping Theorem) and the Nyquist Stability Criterion.

The are four preprogrammed contours given by the variable "op".

'ret'; pts = [x0,y0, x1,y1]; % The vertices of a rectangle

'circle'; pts = [R, xc,yc]; % The radius and center of a circle

'ny_base'; pts = [R, xc,yc]; % The radius of a right semicircle and its center

'ny_desv'; pts = [R, xc,yc, epsilon]; % 'nybase' with a semicircle detour of radius epsilon.

'ny_desv_neg'; pts = [R, xc,yc, epsilon]; % 'ny_desv' through the left half complex plane.

Each preprogrammed contour is presented in four different colors and linestyles, enabling a fast understanding of the direction of the contour and the relationship between the contour in the s-plane and transformed one in the F(s)-plane.

Two possible animations:

1 - Both paths are drawn at the same time.

2 - After plotting the contour and the transformed contour, it is possible to run an animation of a point moving around both paths.

Update 2.0.0

Minor erros on axis during animations corrected.

Change from a step-size-based path construction to a number-of-elements based construction.

Update 2.1.0

Animated comparison of Nyquist, Bode and Nichols plots.

fc_lib_animate_pt_xy_without_sobrepo_sub_BodeNyqNich

fc_lib_animate_pt_xy_without_sobrepo_sub_BodeNyquist

A future release might contain an interative interface with those plots.

Update 2.2.0

Add 'ny_desv_neg', which does the nyquist contour with a detour on the left half of the complex plane.