Impulse ResponseFrom: U(1)5432AmplitudeTo: Y(1)10-1-2-300.511.522.533.544.55Time (sec.) 回目录
例8_27
离散系统
H(z)?0.632 2z?1.368z?0.568绘制出系统的Nyquist曲线，判别闭环系统的稳定性，并绘制出闭环系统的单位冲激响应。 num=0.632;
den=[1 ,-1.368,0.568]; [z,p,k]=tf2zp(num,den); p
dnyquist(num,den,0.1);
title('Discrete Nyquist Plot'); figure(2)
[num1,den1]=cloop(num,den); dimpulse(num1,den1);
title('Discrete Impulse Response');
p =
0.6840 + 0.3165i 0.6840 - 0.3165i Discrete Impulse ResponseFrom: U(1)8642AmplitudeTo: Y(1)0-2-4-6-8051015202530Time (sec.)
回目录
例8_28
一多环系统，
G(s)?r(s)16.7s (0.85s?1)(0.25s?1)(0.0625s?1)y(s)10GainG(s)其结构如图，试用Nyquist曲线判断系统的稳定性。
k1=16.7/0.0125; z1=[0];
p1=[-1.25 -4 -16];
[num1,den1]=zp2tf(z1,p1,k1); [num,den]=cloop(num1,den1); [z,p,k]=tf2zp(num,den); p
figure(1);
nyquist(num,den);
title('Nyquist Plot'); figure(2)
[num2,den2]=cloop(num,den); impulse(num2,den2);
title('Impulse Response');
p =
-10.5969 +36.2148i -10.5969 -36.2148i -0.0562
Impulse ResponseFrom: U(1)201510AmplitudeTo: Y(1)50-5-10-1500.10.20.30.40.50.6Time (sec.) 回目录
例8_29
非线性系统
??ax?bu?x??u?f(?) ???cx?其中
??2.1?1.87?0.2030.894??1??1.0?0?000??b???，c??00?1?2? a??100??0?0?????0010???0?k1??f(?)?k2?
当?k1,k2?的（1/2,2/3）或[1,2]时，判断非线性系统的绝对稳定性。
a=[-2.1,-1.87,-0.203,0.894;1,0,0,0;0,1,0,0;0,0,1,0]; b=[1,0,0,0]'; c=[0,0,-1,-2]; d=0;
[num,den]=ss2tf(a,b,c,d); num=-1*num;
[z,p,k]=tf2ss(num,den); p
figure(1);
nyquist(num,den);
title('Nyquist Plot');
p = 1 0 0 0