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diff --git a/29/CH7/EX7.17.3/exa7_17_3.sce b/29/CH7/EX7.17.3/exa7_17_3.sce new file mode 100755 index 000000000..ed8094a7b --- /dev/null +++ b/29/CH7/EX7.17.3/exa7_17_3.sce @@ -0,0 +1,22 @@ +//caption:stability_using_Nyquist_criterion +//example 7.17.3 +//page 238 +clf(); +s=%s; +s1=-s; +g=(s+0.25)/(s^2*(s+0.5)*(s+1)); +g1=(s1+0.25)/(s1^2*(s1+0.5)*(s1+1)); +GH=syslin('c',g); +GH1=syslin('c',g1); +nyquist(GH); +nyquist(GH1); +mtlb_axis([-2000 500 -30 30]); +xtitle('Nyquist plot of (s+0.25)/(s^2*(s+0.5)*(s+1))') +figure; +show_margins(GH,'nyquist') +disp("since the point(-1+%i0) is encircled clockwise by Nyquist plot ,so N=-1 and P=1(given)") +N=-1;//no. of encirclement of -1+%i0 by G(s)H(s) plot anticlockwise +P=1;//no. of poles of G(s)H(s) with positive real part +Z=P-N;//np.of zeros of 1+G(s)H(s)=0 with positive real part +disp(Z,"Z=") +disp("as Z=2,there are two roots of closed loop characterstics eq having positive real part, hence system is unstable.")
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