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