nicholschart

Arguments

modules

real vector ( modules (in dB))

args

real vector (phases (in degree))

colorss

a scalar or a vector, the color indices for isogain and iso phase curves

Description

plot the Nichols'chart: iso-module and iso-argument contours of y/(1+y) in y phase/gain plane

nicholschart may be used in conjunction with black.

The default values for modules and args are respectively :

[-12 -8 -6 -5 -4 -3 -2 -1.4 -1 -.5 0.25 0.5 0.7 1 1.4 2 2.3 3 4 5 6 8 12]

[-(1:10) , -(20:10:160)]

Remark

Traditionally, the syntax for nicholschart is: nicholschart(modules=gains, args=phases, colors=colors), but the following syntax is also allowed: nicholschart(gains, phases, colors).

Examples

//Nichols chart
clf()
nicholschart(modules=[-6 -3 -1 1 3 6], args=[-1 -20 20 40 80 160 180]);

//Black diagram with Nichols chart as a grid
s=poly(0,'s');
Plant=syslin('c',16000/((s+1)*(s+10)*(s+100)));
//two degree of freedom PID
tau=0.2;xsi=1.2;
PID=syslin('c',(1/(2*xsi*tau*s))*(1+2*xsi*tau*s+tau^2*s^2));
clf();
black([Plant;Plant*PID ],0.01,100,["Plant";"Plant and PID corrector"]);
//move the caption in the lower right corner
ax=gca();Leg=ax.children(1);
Leg.legend_location="in_lower_right";
nicholschart(colors=color('light gray')*[1 1])

See also

• black — Black-Nichols diagram of a linear dynamical system
• nyquist — nyquist plot
• hallchart — Draws the Hall chart

History