4．1(1) a=[2 1 8];b=[1];t=0:0.01:30; subplot(1,2,1);impulse(b,a,t); subplot(1,2,2);step(b,a,t);
(2) a=[2 1 8];b=[1];t=0:0.01:30; y1=impulse(b,a,t)' y2=step(b,a,t)' 4.2 t=0:0.1:10;
a=[1 5 6];b=[1 5];s1=step(b,a,t); a=[1 2 5];b=[1 5];s2=step(b,a,t); a=[1 2 1];b=[1 5];s3=step(b,a,t); plot(t,s1,t,s2,'--',t,s3,'+');
xlabel('t');title('阶跃响应s(t)'); legend('s1(t)','s2(t)','s3(t)');
4.3 a=[1 3 2];b=[-1 2];sys=tf(b,a); t=0:0.01:5;f=cos(t); subplot(1,2,1); lsim(sys,f,t); subplot(1,2,2); y=lsim(sys,f,t);
plot(t,y);xlabel('t');title('y(t)')
4.4 a=[1 3 2];b=[1 2]; [A,B,C,D]=tf2ss(b,a); sys=ss(A,B,C,D); t=0:0.01:10;
f=zeros(1,length(t)); zi=[1,1];
y=lsim(sys,f,t,zi); plot(t,y); xlabel('t'); title('零y(t)');
输入响应
