How can i use the PID controller function

I am trying to use the PID controller in matlab but when i do, i get the message "undefined function or variable". Is there some download that i can install or if someone could give me a solution I'd appreciate it, got some assignments i need to complete.

Thanks in advance

[David Sanchez]

Could you please give any example of how you are using the function? It is a bit difficult to guess anything by the information provided.

[William]

I was trying to following an example i found on this website:

http://ctms.engin.umich.edu/CTMS/index.php?example=Introduction&section=ControlPID

Kp = 1; Ki = 1; Kd = 1;

s = tf('s');

C = Kp + Ki/s + Kd*s

C =

s^2 + s + 1
-----------
     s

C = pid(Kp,Ki,Kd)

tf(C)

ans =

s^2 + s + 1
-----------

thats when i get the message undefines function or variable "pid"

Answer 1

[Arkadiy Turevskiy]

pid objects and PID Tool were added to Control System Toolbox in release 2010b. Upgrade to that release or later to be able to use pid objects.

You can still do what the example describes, you will just have to represent PID controllers as transfer functions, as discussed at the top of the example.

Answer 2

[David Sanchez]

As an example, you could take a look at the following link:

http://blogs.mathworks.com/seth/2009/12/24/pid-control-made-easy/

Answer 3

[bassem adel]

how can I use the pid function in MATLAB R2007b ?