Re: Disturbance Responce for a simple control system

[Kai Mueller]

On Fri, Sep 25, 1998 at 01:47:54PM +0900, Hiroshi Shinozawa wrote:
> I think about the following Feedback Loop
> 
> DISTURBANCE -----------------------
>                                    | 
> STEP INPUT --->O---->|Controller|--O--|Process|--O---> OUTPUT
>                |                                 |
>                -----------------------------------
> I know Step Input Responce is easily calculated by OCST 
> "step" function.
> But I don't know how to calculate the Step Disturbance
> Responce.
> 
> I use "lsode" function to simulate a step disturbance
> responce as well as a step input reponce.
> I am searching a simple function like OCST "step" to 
> simulate step disturbance respponce.
> Advise me please. 
> **********************************************
> address@hidden
> Hiroshi_Shinozawa
> YHC TC Phone 731-22535
> **********************************************
> 

There are several methods in OCST to build your
system from systems discriptions of the controller and
the process. I recommend to look at (OCST m-file):

  controldemo
    [2] block diagram manipulations
        [13] design examples


I personally prefer the following method:

1. Assume the process is G and the controller is K
   (e.g. G = tf2sys(1,[1 1]); and K = tf2sys([1 1],[1 0]);)

2. The closed loop system according to your block diagram is
   Gcl = buildssic([1 2; 2 -1], [], [1], [1 2], G, K);

3. step(Gcl) shows the disturbance step response.
   (BTW step(Gcl, 2) shows the reference step response)


The syntax of step 2. is as follows:
   Gcl = buildssic([1 2; 2 -1], [], [1], [1 2], G, K);
                        ^       ^    ^     ^
                        |       |    |     |
                        |       |    |     first input is input to
                        |       |    |     system 1 (G) = disturbance,
                        |       |    |     second input is input to
                        |       |    |     system 2 (K) = step input
                        |       |    |
                        |       |    output is the output of system 1 (G)
                        |       |
                        |       no "internal inputs"
                        |
                        connect input of system 1 (G) with
                        output of system 2 (K)
                        connect input of system 2 (K) with
                        the negative output of 1 (G)

Kai

-- 
 Kai P. Mueller
 Control Department (Regelungstechnik) | Phone [+49] (531) 391-3835
 Technical University Braunschweig     | Fax   [+49] (531) 391-5194
 D-38092 Braunschweig                  | Email address@hidden