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nyquist — nyquist plot
nyquist( sl,[fmin,fmax] [,step] [,comments] ) nyquist( sl, frq [,comments] ) nyquist(frq,db,phi [,comments]) nyquist(frq, repf [,comments])
| sl | : syslin list (SIMO linear system in continuous or discrete time ) |
| fmin,fmax | : real scalars (frequency bounds (in Hz)) |
| step | : real (logarithmic discretization step) |
| comments | : string vector (captions). |
| frq | : vector or matrix of frequencies (in Hz) (one row for each output of sl). |
| db,phi | : real matrices of modulus (in Db) and phases (in degree) (one row for each output of sl). |
| repf | : matrix of complex numbers. Frequency response (one row for aech output of sl) |
Nyquist plot i.e Imaginary part versus Real part of the frequency response of sl.
For continous time systems sl(2*%i*%pi*w) is plotted. For discrete time system or discretized systems sl(exp(2*%i*%pi*w*fd) is used ( fd=1 for discrete time systems and fd=sl('dt') for discretized systems )
sl can be a continuous-time or discrete-time SIMO system (see syslin). In case of multi-output the outputs are plotted with different symbols.
The frequencies are given by the bounds fmin,fmax (in Hz) or by a row-vector (or a matrix for multi-output) frq.
step is the ( logarithmic ) discretization step. (see calfrq for the choice of default value).
comments is a vector of character strings (captions).
db,phi are the matrices of modulus (in Db) and phases (in degrees). (One row for each response).
repf is a matrix of complex numbers. One row for each response.
Default values for fmin and fmax are 1.d-3, 1.d+3 if sl is continuous-time or 1.d-3, 0.5 if sl is discrete-time.
Automatic discretization of frequencies is made by calfrq.
xbasc();
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));
comm='(s^2+2*0.9*10*s+100)/(s^2+2*0.3*10.1*s+102.01)';
nyquist(h,0.01,100,comm);
h1=h*syslin('c',(s^2+2*0.1*15.1*s+228.01)/(s^2+2*0.9*15*s+225))
xbasc();
nyquist([h1;h],0.01,100,['h1';'h'])
xbasc();nyquist([h1;h])
| << nf3d | param3d1 >> |