transfer function discrete gives NaN why?

[aswwwa]

Hello,

i have problem with discrete transfer function which has the input range [-30 to 30]

and the transfer function as shown in the image attached

the output is NaN ??? what could be the problem ?

[Barp]

It is difficult to see the diagram, but are you sure you are not feeding NaN to the block? The TF function should not be having NaN. Also, I noticed that you are feeding a TF model externally from a System Identification. Notice that the model could be generated invalid for moment and this would generate incorrect result. You have to verify with error checking and the parameters characteristics of the model to be sure that an improper system is not generated.

Also, when you try to create an adaptive control system like that, be aware that to improve stability of your system, in general it is a good idea to have the adaptation loop in slower sampling frequency than the control algorthm. To do that, you can try to start incapsulate your code into subVIs and if you right-click to any subVI, you can choose "SubVI node setup" and you can then choose "Discrete" with a specific sampling time that is slower than your main frequency. When executing a subVI that has sampling time slower than 2x the sampling time, the VI will just 'hold' the previous results for sometime.

[aswwwa]

making the sampling time slower for the adaptive algorithm is that including the ARX plant estimation model??

i have problem in implementing Dahlin controller ....the controller keeps changing because the ARX (B(q)) is changing for no reason ?? why is that happening

[aswwwa]

I have Fixed this problem and i put the code in sub VI as u suggested, in have another problem which is the input to the motor is not as required is way to big and changing all the time?

wat could be the happening?!! i  have attached the code