Home › Forums › FOMCON toolbox: Support forum › Fractional Control Basic
 This topic has 35 replies, 4 voices, and was last updated 6 years, 2 months ago by smitapadhy.

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December 27, 2014 at 12:51 #1031Pritesh ShahGuest
Hi,
I want to use stepinfo for fractional order system.
It is giving error.
Could you please give one example?
Thanking You,
December 27, 2014 at 16:35 #1033AlekseiKeymasterYou may use
stepinfo()
on an approximated system. This function is not yet available for fotf systems.January 8, 2015 at 11:19 #1035Pritesh ShahGuestRegarding FInding Norm 2.
———————Dear Alekesi,
I want to find norm 2 of fractional order controller.
G2=fotf(tf([0.5 0.1 0.01],[1 2 1 0]))
Fractionalorder transfer function:
0.5s^{2}0.1s+0.01
——————
s^{3}+2s^{2}+s
norm(G2)
Error::
Attempt to reference field of nonstructure array.Error in fotf/freqresp (line 14)
a = G.a;Error in fotf/norm>@(x)freqresp(x,G).*freqresp(x,G) (line 25)
f = @(x)freqresp(x, G).*freqresp(x,G);Error in quadgk/evalFun (line 331)
fx = FUN(x);Error in quadgk/vadapt (line 250)
[fx,too_close] = f(x);Error in quadgk (line 149)
[q,errbnd] = vadapt(@evalFun,tinterval);Error in fotf/norm (line 27)
n = quadgk(f, dx*1i, dx*1i) / (2*pi*1i);
—————————————————–Please help me for this also.
Also, if you can help me out to explain important of norm 2, it will be useful to me.Thanking You,
January 9, 2015 at 18:55 #1039AlekseiKeymasterThis is a bug. Consider the following patch: https://fomcon.net/forums/topic/preliminaryreleasesandpatches/#post1037
Towards your second request, see the following PDF: http://www.abo.fi/~htoivone/courses/robust/rob2.pdfJune 11, 2015 at 14:41 #1089syed naeem haiderGuestHi,
i am trying to use fractional integrator in simulink with physical model,, but the problem i am facing is that physical ball and beam system is attached with pc and matlab version used in that system is Matlab2008a ,,,, so when i load fomcon toolbox i do not get ant fractional blocks in simulink library of fomcon… ” FOTF_gui ” is working fine ….. in matlab ,,, but i cannot use fractional blocks in simulink…..
is there any way possible to use fractional integrator in simulink model by using fractional transfer function from work space to simulink…..
or any way to make fractional transfer function in simulink without blocks …..
June 12, 2015 at 15:38 #1093AlekseiKeymasterPlease see this comment: https://fomcon.net/fomcontoolbox/download/#comment1921
July 2, 2015 at 06:06 #1102pritesh shahGuestHi Aleksei,
Hope you are fine. Once again, thanks for nice toolbox.
I have some basic
1. If order of fractional parameters between, 1 to 2, than what is the effect on stability?
2. If more then 2, than what is the effect on stability?
There is some concept q*pi/2, but I am not able to understand properly.
July 26, 2015 at 09:05 #1107Nitish KatalGuestDear Sir,
I’ve been using the FOMCON toolbox and its working great.
I have some issue regarding the check of stability of the Fractional Order System;
Say I’ve a FO plant G and a FO PID Controller, how can I check for the stability of this system directly,
Like is the system is STABLE return 1 if NOTSTABLE return 0.
August 1, 2015 at 08:39 #1110pritesh shahGuestHi Alekesi,
I want to find out output of system using lsim function.
If it is same time interval (T), then we are able to get correct results.
But, in one of the problem, time interval is not the same. I am getting different answer.
Could you please suggest something.
Thanking You in advance,
Say example,
G=fotf(‘1′,’s^0.5+1’);
u=ones(1, 1001);
t=0:0.01:10;
y=lsim(G,u,t);
% I will get correct result as time vector has same interval.% if t has variable time values, I am not getting correct answer.
% U have checked code of lsim, h=t(2)t(1)August 1, 2015 at 09:30 #1112AlekseiKeymasterDear Nitish,
The function you are looking for is called isstable(). Therefore, just doisstable(feedback(G_PLANT*G_FOPID,1))
. This reply was modified 8 years, 11 months ago by Aleksei.
August 1, 2015 at 09:31 #1113AlekseiKeymasterDear pritesh,
This is a known problem with fixedstep solvers. The suggested method is to decrease step size until the results are the same.August 1, 2015 at 10:15 #1114pritesh shahGuestHi Nitish,
I think, You can make system closed loop transfer function using feedback function.
Check for stability of closed loop system.
Say Example,
G is fO plant, C is FPID.G=fotf(‘1′,’s^0.5+1’);
C=fracpid(1,1,0.5,1,0.5)
G_C=feedback(G*C,1);
isstable(G_C)February 21, 2016 at 14:35 #1191priteshParticipantDear Alekesi,
I want to define fractional transfer function k/(s+a)^alpha.
where, alpha is fractional order between 0 to 1.Could you please help for the same?
March 28, 2016 at 13:52 #1196priteshParticipantDear Alekesi,
Any idea about inverse Laplace of fractional order system?
Y(s)= (k1*s^(lam+mu)+k2*s^lam+k3)/(k1*s^(lam+mu+1)+(1+k2)*s^(lam+1)+T*s^(lam+2)+k3*s);
I want to find out inverse Laplace of Y(s)?
Any idea or comments??
March 28, 2016 at 15:06 #1197AlekseiKeymasterYou may want to check this out: http://www.tuke.sk/petras/foc_laplace.pdf

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