how to get PID output?
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hello i am currently doin my bachelor thesis ,, the project is ball on beam. i am using PID function for matlab to control a servo motor . the code is as follows:
s = tf('s');
P_ball = 0.48/s^2;
Kp =2;
Kd =1;
Ki=.75;
C = pid(Kp,Ki,Kd);
sys_cl=feedback(P_ball,1);
t=0:0.01:5;
step(0.25*sys_cl)
disp(sys_cl);
The problem is extracting the output value from the PID function. the output of PID function is supposed to be the angle of the servo motor,, now i dont know how to get this angle in order to give it to the servo motor continuously. can anyone help?
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Answers (4)
Arkadiy Turevskiy
on 7 Jul 2014
Your code, as written does not make much sense. You define controller C, but then do not use it, and instead just use unity gain when computing closed-loop response. I am also not sure why you are mutiplying sys_cl by 0.25 when computing the step reponse.
The more meaningful code would be:
s = tf('s');
P_ball = 0.48/s^2;
Kp =2;
Kd =1;
Ki=.75;
C = pid(Kp,Ki,Kd);
sys_cl=feedback(C*P_ball,1);
t=0:0.01:5;
step(sys_cl)
what you see then is the angle of the motor (the variable you control). The output of the PID would be something like a voltage request to the motor. Another issue is that typically a motor transfer function is not a double integrator, like your plant transfer function, but that's for you to figure out.
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parag patil
on 23 Oct 2020
Hello,
I had the same question. Sorry for being too late, but did you manage to get the answer?
Komal Damodara
on 4 Apr 2019
s = tf('s');
P_ball = 0.48/s^2;
Kp =2;
Kd =1;
Ki=.75;
C = pid(Kp,Ki,Kd);
sys_cl=feedback(C*P_ball,1);
t=0:0.01:5;
step(sys_cl)
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Komal Damodara
on 4 Apr 2019
s = tf('s');
P_ball = 0.48/s^2;
Kp =2;
Kd =1;
Ki=.75;
C = pid(Kp,Ki,Kd);
sys_cl=feedback(C*P_ball,1);
t=0:0.01:5;
step(sys_cl)
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