how to add disturbance factor ?

I have to add a disturbance factor after 400 sec when my system is stable in order to check the stability while using PID controller. Disturbance factor is Aexp(-Bt). what i have to do ??

Answer 1

[Azzi Abdelmalek]

• Use these a clock block to generate a time t,
• multiply the time t by a constant -B,
• pass the output -B*t through a Math function block (choose exp function),
• multiply the output by A

[HASSAN]

Dear, I have done this thing already, as for as i have my understanding it will show the run time value but i want to add it after 400sec one thing. Another problem is that there is another time t parameter in my mathematical model both will be the same as you have mentioned idea to use for disturbance ??

Answer 2

[Toby Russell]

How would one do this in code? ie not using simulink

if I wanted to add a disturbance at 40 seconds to a system model in order to test the controller?

live script code

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

[Sachin Kumar]

Dear same problem i am facing if you have done this thing. Could you please help me to solve it out?