%源代码-实验-题目1%
t = 0:0.1:12; num = [1];            %步长；传递函数分母
Zeta1 = 0.1;den1 = [1 2*Zeta1 1];   %Zeta_n即阻尼比取值
Zeta2 = 0.4;den2 = [1 2*Zeta2 1];
Zeta3 = 0.6;den3 = [1 2*Zeta3 1];
Zeta4 = 0.8;den4 = [1 2*Zeta4 1];
Zeta5 = 1;den5 = [1 2*Zeta5 1];
Zeta6 = 0.707;den6 = [1 2*Zeta6 1];
[y1,x,t] = step(num,den1,t);        %构建阶跃响应函数
[y2,x,t] = step(num,den2,t);
[y3,x,t] = step(num,den3,t);
[y4,x,t] = step(num,den4,t);
[y5,x,t] = step(num,den5,t);
[y6,x,t] = step(num,den6,t);
plot(t,y1,t,y2,t,y3,t,y4,t,y5,t,y6);    %将六个曲线画在一个图上
grid on;
xlabel('t/s');ylabel('c(t)');
title('Unit-Step Response of \phi(s)=\omegan^2/(s^2+2\xi\omegans+\omegan^2)')
text(2.2,1.399,' \leftarrow \xi=0.1','FontSize',13);    %箭头注释阻尼比
text(2.6,1.15,' \leftarrow \xi=0.4','FontSize',13);
text(2.8,1.006,' \leftarrow \xi=0.6','FontSize',13);
text(2.8,0.9283,' \leftarrow \xi=0.707','FontSize',13);
text(2.8,0.8705,' \leftarrow \xi=0.8','FontSize',13);
text(2.8,0.7689,' \leftarrow \xi=1','FontSize',13);
str = {'\omegan=1'};                %注释Wn取值
text(1,1.7,str,'FontSize',13)

%源代码-实验一-题目3%
Zeta1 = 1; num1 = [1*Zeta1];    %K=1的开环传递函数分子
Zeta2 = 3; num2 = [1*Zeta2];    %K=3
Zeta3 = 5; num3 = [1*Zeta3];    %K=5
den = [1 2 3 2];                %开环传递函数公共分母
den4 = [1 2 3 3];               %K=1的闭环传递函数分母
den5 = [1 2 3 5];               %K=3
den6 = [1 2 3 7];               %K=5
num = [1];                      %闭环传递函数公共分子

figure(1);                      %画图1
subplot(211);
sys1 = tf(num1,den);            %K=1的开环传递函数
margin(sys1);                   %画Bode图并求裕度
subplot(212);
nyquist(sys1);                  %画nyquist图
grid on;

figure(2);
subplot(211);
sys2 = tf(num2,den);
margin(sys2);
subplot(212);
nyquist(sys2);
grid on;

figure(3);
subplot(211);
sys3 = tf(num3,den);
margin(sys3);
subplot(212);
nyquist(sys3);
grid on;

figure(4);
sys4 = tf(num,den4);            %K=1的闭环传递函数
sys5 = tf(num,den5);            
sys6 = tf(num,den6);            
t = linspace(0,50);            %横轴取值范围0到50
y = linspace(-5,5);             %横轴取值范围-5到5
y1 = step(sys4,t);              %构建K=1时的阶跃响应函数
y2 = step(sys5,t);
y3 = step(sys6,t);
plot(t,y1,t,y2,t,y3);           %将三个时域响应函数画在一张图上