matlab的tfdata函数_matlab 入门基本操作命令与函数

一  ：tf([  ],[  ]) 函数

是传递函数的意思，一般学自动控制原理的时候经常用，在s域中，比如你要输入G(s)=1/(s^2+2s+1)，就可以在matlab中输入G=tf([1],[1 2 1]);就OK了。不懂的话你可以在command窗口输入help tf 就行了

matlab中  help tf  :

tf

Create or convert to transfer function model

Syntax

tf

sys = tf(num,den)

sys = tf(num,den,Ts)

sys = tf(M)

sys = tf(num,den,ltisys)

tfsys =tf(sys)

tfsys = tf(sys,'inv')

Description

tf  is used to create real-or complex-valued transfer function models (TF objects) or to convertstate-space or zero-pole-gain models to transfer function form.

二：

sysd=c2d(sys,Ts,'z'); % c2d ---连续的时间系统转化为离散的时间系统,即离散化.'t'表示双线性变换法

% Find critical valuecrs Kcr,Wcr % 'z'表示带零阶保持器的Z变换法,可缺省

三：

sys=tf(5.235e005,[1,87.35,1.047e004,0]);%获得传递函数。

dsys=c2d(sys,ts,'z');%将连续的时间模型转换成离散的时间模型，采样时间是ts=0.001。

[num,den]=tfdata(dsys,'v');%获得离散还建模型的分子分母矩阵

四： PID MATLAB 仿真程序

>> ts = 0.001;

sys  = tf (400,[1 ,50,0]);

dsys = c2d (sys,ts,'z');

[num,den] = tfdata(dsys,'v');

u_1  = 0.0 ;u_2 = 0.0; u_3 = 0.0 ;

y_1 = 0   ; y_2 = 0;   y_3 = 0;

x =  [0, 0 ,0];

error_1 = 0;

error_2 = 0;

for k=1:1:1000

time(k) = k*ts;

rin(k) = 1.0;

kp = 8;

ki = 0.10;

kd = 10;

du(k) = kp*x(1) + kd*x(2) + ki*x(3);

u(k) = u_1 + du(k);

if u(k) >= 10;

uk = 10;

end

if u(k) <= -10 ;

u(k) = -10;

end

yout(k) = -den(2)*y_1 - den(3)*y_2 + num(2)*u_1 +num(3)*u_2;

error = rin(k) - yout(k);

u_3 = u_2 ; u_2 = u_1; u_1 = u(k);

y_3 = y_2 ; y_2 = y_1; y_1 = yout(k);

x(1) = error - error_1;

x(2) = error - 2*error_1 + error_2 ;

x(3) = error;

error_2 = error_1;

error_1 = error;

end

plot(time,rin,'b',time,yout,'r');

xlabel ('time(s)');

ylabel ('rin,yout');