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.TH black 1 "April 1993" "Scilab Group" "Scilab Function"
.so ../sci.an
.SH NAME
black - Black's diagram (Nichols chart)
.SH CALLING SEQUENCE
.nf
black( sl,[fmin,fmax] [,step] [,comments] )
black( sl,frq [,comments] )
black(frq,db,phi [,comments])
black(frq,repf [,comments])
.fi
.SH PARAMETERS
.TP 10
sl
: list ( linear system \fVsyslin\fR)
.TP 10
fmin,fmax
: real scalars (frequency bounds)
.TP 10
frq
: row vector or matrix (frequencies)
.TP 10
db,phi
: row vectors or matrices (modulus, phase)
.TP 10
repf
: row vectors or matrices (complex frequency response)
.TP 10
step
: real
.TP 10
comments
: string
.SH DESCRIPTION
Black's diagram (Nichols'chart) for a linear system \fVsl\fR.
\fVsl\fR can be a continuous-time or discrete-time SIMO system (see \fVsyslin\fR).
In case of multi-output the outputs are plotted with different
symbols.
.LP
The frequencies are given by the bounds \fVfmin,fmax\fR (in Hz) or by a row-vector
(or a matrix for multi-output) \fVfrq\fR.
.LP
\fVstep\fR is the ( logarithmic ) discretization step. (see \fVcalfrq\fR for the
choice of default value).
.LP
\fVcomments \fR is a vector of character strings (captions).
.LP
\fVdb,phi\fR are the matrices of modulus (in Db) and phases (in degrees).
(One row for each response).
.LP
\fVrepf \fR matrix of complex numbers. One row for each response.
.LP
To plot the grid of iso-gain and iso-phase of \fVy/(1+y)\fR use \fVchart()\fR.
.LP
Default values for \fVfmin\fR and \fVfmax\fR are
\fV1.d-3\fR, \fV1.d+3\fR if \fVsl\fR is continuous-time
or \fV1.d-3\fR, \fV0.5\fR if \fVsl\fR is discrete-time.
.SH EXAMPLE
.nf
s=poly(0,'s')
h=syslin('c',(s^2+2*0.9*10*s+100)/(s^2+2*0.3*10.1*s+102.01))
chart();
sstr='(s^2+2*0.9*10*s+100)/(s^2+2*0.3*10.1*s+102.01)';
black(h,0.01,100,sstr);
h1=h*syslin('c',(s^2+2*0.1*15.1*s+228.01)/(s^2+2*0.9*15*s+225))
xbasc()
black([h1;h],0.01,100,['h1';'h'])
.fi
.SH SEE ALSO
bode, nyquist, chart, freq, repfreq, calfrq, phasemag
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