a unit step disturbance

Hi All,

I need to Simulate a controllers with a unit step change in set-point followed by a unit step

disturbance at a time of 40 seconds.

My question is, what ways are there of going about implementing the unit step disturbance?

Some guidance with this would be appreciated.

Some of the code is below

K = 2;

tau = 3;

den = [tau 1];

sysmod = tf(K,den,'inputdelay',1)

plot (time,response,'g');

hold on

step (sysmod,'k')

hold off

Hagglund-Astrom

Kc = 0.175;

tauI = 2;

theta = 0; %Defines the dead time in the process

haggast1 = feedback((tf(Kc*exp(-theta*s)/s)*sysmod),0.5);

step (haggast1,'g')

hold on

step (sysmod,'k')

legend ('haggast1','sysmod')

hold off

Thanks

Toby

[Toby Russell]

Is anyone here able to help me out with this?

I am looking for how to code a unit step disturbance at 40 seconds.

my code is as follows

(live script)

oad response.dat

plot (time,response,'g');

title ('Actual response')

xlabel ('Time')

ylabel ('Amplitude')

hold on

s=tf('s')

K = 2;

tau = 3;

sysmod = exp(-s)*(K/(tau*s+1))

plot (time,response,'g');

hold on

step (sysmod,'k')

title ('System Model Step Response')

hold off

Applying the Hagglund-Astrom Tuning

theta = 0.27; % Defines the dead time in the process

kp = (0.14/K)+((0.28*tau)/(theta*K)) % Defines the Proportional element CORRECT

ki = ((0.33*theta) + ((6.8*theta*tau)/(10*theta+tau))) % Defines the Integral element CORRECT

haggast1 = feedback((kp + (ki/s))*sysmod,1); % Applying the Hagglund-Astrom tuning

step (haggast1,'g')

hold on

step (sysmod,'k')

%step (haggast1,40)

title ('Haggland-Astrom Tuning')

legend ('haggast1','sysmod')

hold off

Applying the Cohen and coon PI Tuning

theta1 = 0.275;

kp1 = (1/K)*(tau/theta1)*(0.9+(theta1/(12*tau))) % Defines the Proportional element CORRECT

ki1 = (theta1*(30+(3*(theta1/tau))) / (9+(20*(theta1/tau))))% Defines the Integral element CORRECT

CC = feedback((kp1 + (ki1/s))*sysmod,1); % Applying the Cohen Coon tuning

step (CC,'g')

hold on

step (sysmod,'k')

title ('Cohen Coon Tuning')

legend ('CC','sysmod')

hold off