Dynamic Transfer Function in simulink

I have a Transfer function of my model... but my model is dynamic, the coefficients change in time . so this means that i need to represent this in Simulink, but i haven't being able to represent this , the blocks of TF in simulink are for fixed values. Any ideas???

      b3*s^3+b2*s^2+b1*s^1+b0
-------------------------------------
a5*s^5+a4*s^4+a3*s^3+a2*s^2+a1*s+a0

Answer 1

[Guy Rouleau]

I recommend this solution "How do I model a transfer function with coefficients that vary with simulation time in Simulink 7.5 (R2010a)?"

http://www.mathworks.com/support/solutions/en/data/1-D9A379/?solution=1-D9A379

I also recommend going through this post on this exact topic:

http://blogs.mathworks.com/seth/2011/03/08/how-do-i-change-a-block-parameter-based-on-the-output-of-another-block/

Answer 2

[Fangjun Jiang]

No. When you use the transfer function block in Simulink, you can specify the coefficients as b1, b2, a1, a2, etc. Then you'll have to set the value for a1, a2, b1, b2 etc. in the MATLAB base workspace. Then you can change the value for a1, a2, b1, b2 and re-run simulation without changing your Simulink model.

[Paulo Silva]

Actually it's possible to change the parameters with time without stopping the simulation, the only thing that can't change is the size of the Numerator and Denominator of the transfer function.

[Shahzad Ali]

can you please tell me that how to change the coefficients of the transfer function without stopping the simulation. it would be very helpful. i have a complex system but i ask this question for a simple block, which i am going to link it for you. https://ch.mathworks.com/matlabcentral/answers/408336-how-to-change-the-coefficients-of-a-transfer-function-block-in-simulink-during-simulation?s_tid=prof_contriblnk

Answer 3

[Javier Gonzalez]

Well... what I need is in the same simulation without stop change the values of the a1, b1.... and change this again, i know how to change this but how to represent this is the key.. i have seen something about Observability, in control theory.. but is not clear for me...

Answer 4

[Fangjun Jiang]

Okay, then you need to do the controller realization of the transfer function. Refer to this article but do a double check with a creditable control theory text book. In stead of constant block, you can use a dynamic signal to implement the multiplication so a1, b1 etc. can be changed during the simulation.