Home › Forums › FOMCON toolbox: Support forum › Fractional Control Basic
 This topic has 35 replies, 4 voices, and was last updated 4 years ago by smitapadhy.

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July 4, 2013 at 06:34 #794PriteshGuest
Hi,
I have some basic understanding problem. Whenever we take fractional transfer function. Inside calculation, they use approximation method and convert to higher order control system.
Then, if we use higher order PID (some different form), is it the same?
sorry for asking stupid question?
Thanking You,
July 4, 2013 at 10:00 #796AlekseiKeymasterTo an extent, yes; since approximations are used, we may consider a particular fractionalorder PID controller approximation to belong to a set of all possible highorder integerorder controllers for a given control problem.
January 30, 2014 at 15:36 #881Pritesh ShahGuestHi Alekesi,
One more question. What is use of Mittage Leffer function in FPID?
or In general.
Thanks,
January 30, 2014 at 15:46 #883AlekseiKeymasterIn general, the MittagLeffler function in two parameters is a powerful generalization. It may be used to compute the (roughly speaking) fractional exponential function and thus may be employed for solving fractionalorder differential equations. However, direct use of this function for realtime problems is limited. Therefore, it is not used in FOMCON for FOPID related computations.
March 7, 2014 at 14:44 #893Pritesh ShahGuestHi Alekesi,
I am little bit confuse between CRONE controller and fractional PID Controller.
What is the basics difference between these?
Thanking You,
Pritesh
March 7, 2014 at 14:50 #895AlekseiKeymasterThe underlying principles are the same. However, different approaches are used: the fractionalorder PID may be seen as a generalization of the classical PID, while the CRONE controller is based on a novel control strategy specifically developed by leveraging the flexibility of fractionalorder operators. In both cases frequency domain analysis plays an important role, in case of CRONE controllers even more so.
June 10, 2014 at 14:29 #932Pritesh ShahGuestHi Alekesi,
Once again, I am troubling you.
I am trying to identify model of fractional order structure.
Say I want to identify , k/(s^a+b); a is non integer.
How can I use FOMCON for the same?
Could you please give some small example if possible?
Thanking You,
Pritesh
June 10, 2014 at 16:13 #935AlekseiKeymasterYou can use the
fotfid
tool for this purpose.September 20, 2014 at 10:42 #958Pritesh ShahGuestHi Alekesi,
I have some basic understanding problem. We have a process control in our lab. We want to implement in real time.
By your toolbox, we got controller in Z Transform.
Now, we get error in time domain. How do we find out controller output? (Controller in z Transform)
Thanking You, once again.
September 21, 2014 at 09:25 #960AlekseiKeymasterPlease elaborate. If you use Simulink then you can use the fractional PID block from the FOMCON library.
October 21, 2014 at 05:26 #965SmitaGuestHi Aleksei,
I am finding error while testing the stability of a FOPDT(First Order Plus Delay) plant in fotf viewer(FOMCON command).The plant is K.(e^0.2s)/20s+1.The error is : Cannot assess the stability of a system with internal delays.
How can I solve it???Also I want to know which is the updated version of FOMCON : 0.41beta or 0.42beta
Please suggest.Thanks
Regards
SmitaOctober 21, 2014 at 07:55 #969AlekseiKeymasterAt the moment, it is not possible to assess the stability of systems with delays.
The latest version is 0.41beta, for which a patch has been released in April. See this post: https://fomcon.net/forums/topic/preliminaryreleasesandpatches/#post914November 27, 2014 at 15:17 #1012Pritesh ShahGuestHi Alekesi,
Difference between crone and fractional order controller ?
I know that both of them use kind of fractional calculus only. They have a different structure of controller.
Any comparison or any paper which you can suggest.
Thanking You, once again.
November 27, 2014 at 17:03 #1014AlekseiKeymasterCRONE has several generations of controllers. Kindly see the book in https://fomcon.net/fo/overviewofliterature/ for details.
For instance, the first generation CRONE controller has the following form
\[
C(s)=C_0 s^{\alpha}\tag{1},
\]
with $\alpha, C_0\in\mathbb{R}$. This can be seen as one of the dynamical components of a fractionalorder PID controller, e.g., the integral component
\[
C_I(s)=K_i s^{\lambda},
\]
where $C_0=K_i$ and $\alpha=\lambda$ in (1).November 28, 2014 at 12:54 #1019Pritesh ShahGuestThank You for your kind reply.

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